Im planning getting a Procharger d1. My tpi induction manifold is completely stock. The car is a street car so I want torque down low. My plan was to get a high flo manifold like the F.I.R.S.T (www.firstinjection.com) or get large runners with baseplate and hog out my plenum. But I have talked to a few "engine" guys that tells me for a street car I should keep the factory tpi manifold because it gives me most down low, and when the tpi runns out of breath I will be in boost so the restrictions of the manifold wont affect me. They said it might efen give me a littel extra because of the higher velocity in the oem runners compared to larger aftermarked. Ofcourse I would loose a littel boost because of the higer resistance of the oem manifold and I would get more high end hp by going with a hi flo manifold,but as this is a street car and I never rev past 5800...the oem manifold with a procharger would give me the best overall performance.

IS this true ? or would I be better of getting a hi flo manifold before I supercharge ?

thanks

 

I'm boosting 6psi (Vortech S-Trim) right now with the stock TPI unit (L98). I'll tell you straight out that your friends are wrong. My intake is one of the many bottlenecks I need to work on to get the maximum potential out of my setup. The stock TPI, stock Heads, and Stock Cam restrict the top end of your powerband to 4500-4800 rpm. Launch the car and it pulls hard. Makes monster power between 2500 rpm and 4500 rpm. As it hits 4500 rpm I'm pushing full boost, but my setup is at its weakest point. Because I'm building boost to this point, the drop off in acceleration is pronounced. The motor continues to make alot of noise as it revs to 5500rpm, but it is no longer pulling. This is the result of the stock TPI unit, the stock Heads, and the stock cam. It really sucks!

Thanks to Crossfire for helping me understand it was not necessarily my TPI intake restricting my powerband, but more a combo of the stock TPI, stock heads, stock cam, *and mainly* stock exhaust manifolds.

Anyway, my advice after reading this whole thread and then editing my post is to get your desired powerband while you are still N/A. Then once you are happy with your powerband, choose the right sized S/C for your motor and install.

 

My limited expereince in this area makes me generally agree with Hawaiian. Don't get me wrong, it's MUCH stronger everywhere with boost, but it didn't have the kind of "billiard table" torque curve I always shoot for in my street motors. The boost would keep climbing but over 4500 but power would definitely drop off. Not quite as severe as a stock N/A system , but it was still there.

Got to the point we actually over-boosted in the upper RPMs just so that we could get meaningful midrange boost and a big bump in midrange torque where the boost and the stock intake seemed to work well together.

 

The comparisons your freinds are making are like apples and oranges. Not to mention, YOUR DON"T WANT more low end torque awith a street motor,... all your gonna do is burn the tires up. I believe you goal should be that you fill your cylinder and try to attain volumetric efficiency. Remember you only have to fill 1 cylinder at a time,...so, I think that The intake that you have will not change whether or not you attain volumetric efficiency.. YOu need to concentrate on the proper cam selection, exhaust, fuel requirements, and maximum tuning ( timing, etc,.). Remember, you are forcing the air in, it's not gonna change how much air goes into the cylinder if your intake is bigger..What can change that is a intercooler which will make cooler and more dense air,... that's what you want. Just my opinion.

 

A classic misunderstanding of superchargers there. remember Boost does not make more power AIRFLOW makes more power. Boost is more accurately a measure of restriction. If you take two identical superchargers and put one on a stock tpi setup and one on an identical motor, yet with a high flow intake (stealthram, miniram, base and runners, whatever) the stock tpi motor will show more boost than the high flow intake motor, sometimes by a lot. The high flow intake motor will however make substantially more power. I can go into more detail on the whys and hows of this if you'd like, and guido or somebody can really fill you in on that, but this is the short answer.

Edit:
BTW justin is right about the torque, especially with a supercharger, you're already going to have so much torque down low that trading some off for higher rpm power will actually make your car faster.

 

how much airflow does that supercharger make down low?

if its enough, soon enough down low, you can run a free flowing short runner intake with no real loss... like the LT1 for example...

i honestly wouldnt be too worried about the TQ down low though.. even without tuning for it, you're still going to make more then you can put down on the street.....

 

to rhuarc31 :

Please give me the long answer im interested in any info possible.

I wouldent think that a supercharger (procharger d1sc) gives you anything down low thats why I want a torque friendly indtake like the oem.
I talked to Procharger and they said that on my engine with a 6pound pully I wouldent begin to see boost before 2800 rpm and under that point the oem intake works great. But I can understand that it might be a problem at higner rpm even under boost (the reason to this thread)

I understand that boost is saying something about restriction, but isent it also saying something about air velocity? Air moves faster in smaller runners under higher boost than air in bigger runners under lover boost...but what in this situation gives the most volumetric efficiency.

Im leaning towards getting a bigger indtake, but if it wont give me anything below 5500 I would rather spend the money elsewhere.


any input is welcome

 

Given that I have nothign but "seat of the pants" expereince with the combo I worked on let me describe it this way......

Up to about 4500 the trade-off was a good one. The long TPI runners propped up the extreme low end (below 3000) where there was very little boost. From 3000-4500 it was an animal- blower making some meaningful boost, TPI runners still helping out, not hurting. 4500+ the party started to poop out pretty quick. Forget 6000. Plenty of boost, no power.

That's why we pulleyed the thing up to make some serious boost in the mid RPMs and just let it over-boost up top, and short-shifted it usually around 5200-5400 or so.

 

Man, I’m learning to hate these 2 topics (boost and harmonic tuning), and you’ve managed to combine them in one thread. The problem is that most people really don’t get either…

Lets start with that there is no such thing as too much torque, just not enough traction and/or a driver that isn’t able (willing) to use what they’ve got to work with. Second, you’re talking about a centrifugal blower, they don’t make any boost down low anyway, so it really isn’t going to change what the car does below about 3000rpm, and finally, the TPI doesn’t hit its harmonic tuning point till about 3900rpm, so you’re not going to feel any difference below that no matter what manifold you put on it. In other words, don’t change manifolds to change how it acts under 3000rpm, and anything short of a small, quick spooling turbo or a positive displacement blower won’t change it either (well, N2O sprayed at below that rpm will, but it could also blow things up).

TPI… I’ve said it before and I’ll say it one more time… repeat after me… the reason that stock L98’s fall on their face in the mid/high 4Kgrpm range has nothing to do with the intake. The stock heads are too small to breath past there, so that’s where it dies. The TPI sees it’s harmonic tuning points at about 3000, 3900 and 5300rpm (I know, I skipped the 3000rpm one above, that’s because it’s the 4th harmonic and so weak that 99% of people won’t feel it at all), if you put better heads on one (even stock early ‘80’s 305 heads flow better), and a properly matched exhaust you’ll find that it will happily pull to about 5500-5700rpm before the intake becomes a serious restriction.

rhuarc31 got the basics of boost right… boost is just a measure of restriction to the air being forced into the engine, essentially, if you’ve got a compressor forcing X air into the intake then you will see whatever boost pressure it takes to force that volume of air into the engine. Airflow is what determines power, it doesn’t make a difference if you can get X airflow into one engine NA and it takes 10psi to get the same amount into another, if they’re breathing the same amount of air they’ll make roughly the same power. You WILL NOT ‘loose boost’ with a restrictive intake, your boost will actually go up as long as the compressor is still pumping the same amount of air.

 

link = NFG (dead)

 

to B4Ctom1:

sorry forgot the s at the end

http://www.firstinjections.com


to 83 Crossfire TA:

It is my understanding that the harmonic tuning at 5900 cant be utilized because of manifold vaccum is that true ?

I have the trickflow 64cc cnc heads and the Crane 2032 cam. Do you say I should keep the oem manifold ?

All the high flo variants loose some torque down low, some more than others. even just Lrt looses some down low..if it wont help me the higher rpms then I wont change it. I know that there is a trade off one way or the other I just want the most balanced solution. = no or littel loss down low and strong pull until 5700.

thanks

 

Ok, a little more detail. First any time you restrict airflow into, or out of an engine, you lose power, that's common sense. Now here's how it affects a supercharged or turbocharged engine. It all pretty much comes down to making the compressor work harder to supply the amount of airflow. First you lose power do to higher parasitic loses, more drag on the 'charger. Second you create more heat, which causes power loss do to less air density, and the need for more ignition retard do to the higher chance of detonation. So in essence the 'charger may be pushing the same volume of air, but that does not mean it's pushing the same mass of air, and it's working harder to do it.
Take an engine with a restriction and put it at 6 psi of boost and it will be taking in substantially less air than a free flowing engine at the same boost level.
A simplistic way to look at it is to picture the supercharger as a volumetric efficiency adder. Take your stock engine running at 65% VE and add 50% from the supercharger and your at 115%. Take a modified engine with good heads, intake, cam, and exhaust and you may be running 80-90% VE, add your 50% and your at 130-140%. Now which engine do you think is going to make more power? (Numbers are for the purposes of demonstration, don't take them as rock solid).

Edit :the above is of course dependent on the properly sized supercharger. An engine with better orginal VE may need a bigger supercharger than the one with the lower.

As for your question about air velocity, to a certain extent that is true, though less in force fed applications, superchargers like volume. In the case of 'charger applications a good analogy is like trying to blow through a straw. Try blowing through a little coctail straw as hard as you can, then blow through a big soda straw as hard as you can. Sure the air came out of the coctail straw real hard, but it took you longer to empty your lungs than with the soda straw. So which way flowed the most air in the shortest time?

Also back to the point about boost vs restriction. Look at it this way, once again 2 identical superchargers, one with a restriction one with out. On the restricted one you're showing 6 psi, on the less restricted you're showing 3 psi. Even if you say that they're flowing the same amount of air, guess what you have an option!. Crank up the boost on the less restricted one to take it up to 6 psi, now guess which one's making more power and flowing more air? With a properly sized 'charger of course. This of course brings up pulley sizing, the same pulley that makes 6psi on one engine may not on another engine. I've seen pulleys that were supposed to put the boost at 6psi show 10 and i've seen em show 2.

As for 'charger spool up, well lot's of things affect that, and guess what, 2 identical chargers, one on a restricted engine, one on a free flowing engine, the one on the free flowing engine will spool up quicker do to less backpressure on the turbine. And then another thing people overlook is that spool up in a supercharger is directly related to pulley ratio. You want your supercharger to hit peak boost earlier? Swap out the pulleys. Just like any other type of gear reduction. Though there are issues about peak eff. of the supercharger and things that affect your choices.

Just as in any engine you need to look at the combination of parts as a whole. In your current case right now, with your heads and cam, your intake is already hindering your performance, if you improve there you won't loose all that much down low since you'll gain some back by removing the restriction and allowing your heads and cam to do their work better. Make sure the exhaust is flowing well for the same reason. Everything needs to balance. Add the supercharger into the mix and same thing, it needs to be sized appropriately. For what your talking about the D1sc may be to big, you may be better off with a P 1sc, may not, but you need to take that into consideration. Call up ATI and ask them, I've found their tech guys to be pretty knowledgeable and helpful.

Was that answer long enough for you? We can get deeper into the properties of fluiddynamics(airflow), thermodynamics(heat transfer), how they relate to eachother and the amount of engine a power makes, but that's getting pretty deep.

For my recommendation I'd improve the intake first, either by porting, swapping in runners and base, or a whole new manifold. See where that leaves you. You may find that after taking that cork out you have lots of power and are happy at that level, and spent much less money that on a supercharger. Of course after a while you'll want more, and then you'll already be setup to do it.

Edit: Oh I forgot, about the torque loss down low. Get yourself on the tpi board and see how many people you can find that have upgraded their intakes and are unhappy with the torque loss. It won't be many I guarantee you.

 

Check this out real quick.

Our engines use boost all the time, to create airflow. Right now, if your at sea level, your sitting in 14.7 PSI of boost. it just doesnt feel like boost because your used to it.


When an engine breathes in air, it creates "vacuum", but its not realy vacuum at all. its still boost, its just less boost and so it feels like a vacuum from outside because there is more pressure out here than in the engine..

where 30"~ of vacuum is actually 0 PSI...
0" of vacuum (WOT as we know it... or 100KPA) is actually 14.7 PSI @ sea level...

So lets take an engine pulling 15" of vacuum at idle. that means the pressure in the intake where we took the vacuum reading is actually about 7.5 PSI of boost in the manifold!

so basically, an engine seeing WOT is utilizing as much of the 14.7 PSI of atmospheric boost as it can to make power. we call this being N/A !!!

So when you slap even MORE boost, or artificial atmposphere onto an engine, your power gains are almost LINEAR except for losses due to heat and driving the supercharger...

THAT means, quite simply, the more power an engine makes before we slap forced induction onto it... the more power it will make when we start to crank up the boost.
NO ONE but NO ONE on this board has so far proven that you can make more than 345~ RWHP utilizing N/A TPI induction...
so following the rule of thumb above, if we DOUBLE the atmosphere (thats 15 PSI of boost!) on a BUILT TPI making 300 RWHP, subtract the power to drive the supercharger (50-60HP) then subtract the power lost due to HEAT (say 20%!) our motor is only making about 450 RWHP!!!!!! now that may seem like a LOT but...

NOW take the same motor, slap a stealthram on it. there goes our bottleneck... and now with the right cam we can make 420-450 N/A Quite easilly! NOW slap that supercharger on the motor and crank up the atmosphere to 30 PSI... (15 PSI "boost")

Oh look, now we make damn near 650 RWHP! isnt that something...

 

rhuarc31, yes, I pretty much agree with you on most of that as long as you remember that it is only the case with a properly sized/designed ‘charger, more complete comments:

No, if everything is still capable of flowing enough air to make that power then you will not loose power. As a matter of fact, if something was enough “too big” to allow you to make a significant change and not drop under the airflow the engine needs to make that power, you’ll probably gain power, since now your combination will be better matched.

Quote:

Now here's how it affects a supercharged or turbocharged engine. It all pretty much comes down to making the compressor work harder to supply the amount of airflow. First you lose power do to higher parasitic loses, more drag on the 'charger. Second you create more heat, which causes power loss do to less air density, and the need for more ignition retard do to the higher chance of detonation. So in essence the 'charger may be pushing the same volume of air, but that does not mean it's pushing the same mass of air, and it's working harder to do it.

Remembering the properly sized and designed ‘charger. The thing is that most centrifugal superchargers (except for maybe the most recent designs, but I don’t have any evidence there either way) and turbochargers are designed to move air at a relatively high pressure ratio, usually in the 2.5-4:1 (about 22-44psi boost), and are just starting to come into their efficiency range below 10 or so PSI boost. Theoretically, you could see something like 45% adiabatic efficiency at 5psi, and 70% at 10 PSI and on a 90* day you’ll have 200 degree intake air in both cases. Remember also, it takes a larger centrifugal ‘charger to move the same amount of air at a lower pressure, so there is even the chance that the supercharger won’t even move enough air to make boost at that lower pressure.

Of course, we’re just playing with numbers here anyway, the point is that it could happen either way in real life.

Quote:

As for your question about air velocity, to a certain extent that is true, though less in force fed applications, superchargers like volume. In the case of 'charger applications a good analogy is like trying to blow through a straw. Try blowing through a little coctail straw as hard as you can, then blow through a big soda straw as hard as you can. Sure the air came out of the coctail straw real hard, but it took you longer to empty your lungs than with the soda straw. So which way flowed the most air in the shortest time?

If both flow enough to stay in the efficiency range of the given compressor (most human lungs are only good for 1-2psi), then they will flow the same. The only reason that your example works is that your lungs can’t generate any real pressure and even the big straw is much below the airflow that your lungs are capable of generating.

Instead try blowing through a 6” and 12” PVC pipe. In both cases you’ll stay below the ultimate pressure that your lungs can generate and you’ll get the same airflow, but it will have more of an effect on other objects (say a card house built at the end of the 8’ long pipe) in the 6” one (I bet that you wouldn’t get enough velocity to blow over the card hose in the 12” one but you probably would with the 6”.

Quote:

Was that answer long enough for you? We can get deeper into the properties of fluiddynamics(airflow), thermodynamics(heat transfer), how they relate to eachother and the amount of engine a power makes, but that's getting pretty deep

Skip both, get yourself a good HVAC tech book… it deals with all of this but usually presentis it without any calculus, which will turn most people off the real engineering books.

Quote:

Edit: Oh I forgot, about the torque loss down low. Get yourself on the tpi board and see how many people you can find that have upgraded their intakes and are unhappy with the torque loss. It won't be many I guarantee you.

Again, the intake has little if anything to do with torque production ‘down low.’

 

No. Boost implies a relative pressure difference. NA the pressure in front of the throttle body is the same as behind the throttle body, the piston traveling downward + the air “slugs” moving down the intake runners + the exhaust “slugs” moving down your header tubes all lower the pressure behind them (create a vacuum) that fills the chamber. Actual boost fills the chamber in excess of what the mechanical action of the engine would be capable of without more pressure on the front of the system then atmospheric.

 

I’m reading “I want to spend some money before I spend the money on the blower but I want to get the most out of that money when I get the blower on it.”

If that’s true, the my $.02:

I want to like the trickflow heads (I have had good luck with trickflow products on ford engines), but unfortunately I’ve never seen a trickflow headed SBC that made the power that you would expect with the airflow.

I flat out don’t like the cam

Do you like the powerband that you have now (I may change the rest of what I say here depending on what you answer to this question)?

Anyway, not knowing what other parts you have, the first thing I would look at would be a killer exhaust, 1-3/4” primary long tube headers, killer y-pipe & cat back (3” is probably enough for the tubing but there aren’t many 3” mufflers that flow enough to not be a restriction at over 300-350hp). Second, I’d port the heads, focusing mostly on the exhaust side. I’d shoot for about 90-92% of the intake flow (+/- a little depending on how much boost you plan on running). If it was my car what would happen with the cam would depend on what the heads ended up flowing. After all this I’d look at the intake parts.

 

Crossfire, hmm, well basically in most cases we're saying the same thing. The definite point is the properly sized supercharger.

Maybe I wasn't clear enough on the airflow restriction part, but Yes if all the parts of an engine are capable of flowing a certain amount of air, then you pinch it off somewhere you do lose power. Which is what I was saying compared to what you're saying. In his case he's got good heads, an improved cam, I would assume with that he's got an improved exhaust (of course we know what assuming get's you). So in this case the intake would be a restriction and costing him power.

As for the straw vs pvc pipe, well once again mostly we just looked at it in a different manner. I exagerated small and you exagerated big, where we both know the truth is closer to somewhere in the middle with a fine balance point dependent on each indivdual engine. I would say that if he were looking at a smaller supercharger, say the p1, your comparison would be closer to accurate than mine. But my argument is that looking at the bigger supercharger that he is, the d1, which is capable of flowing quite a bit more air my example would be a little closer. Go even bigger and I get closer, Slap an f-3 on your car and see what happens (I have done this btw, though on a F**D, gotta love an 8 second car even if it does have a stinkin' blue oval on it).

Good point about the HVAC book They're also shorter usually. I usually recommend that anyone read the instruction manual for a superflow flowbench a couple times.

As for the torque down low, here's where I do disagree with you. The intake does have quite a bit to do with this. Too much personal experience, too many dyno sheets posted on this board, and in different magazines doing comparos and test and tunes have proven otherwise too many times to count. Now in our cars in specific what happens most by going to a better flowing intake, especially one with shorter runners, is a FLATTENING of the torque curve, where you may lose 20 or so lbs/ft down low, but gain them up top, and the middle will stay close to the same, assuming all other parts stay the same of course.

 

To rhuarc31 :

Im a frequent reader of the tpi board, but most people modify for drag racing and have eighter high stall converters or manual t. So they dont care much about low rpm torque or dont notice a loss.

Im very interested in info reg the F.I.R.S.T manifold because it is said that it is the only LTR style manifold that can make use of the harmonic tuning around 5800 rpm, thus making it great for both low and high rpm. Does anyone know anything about it?

to Kingtal0n

I see what you are saying and it makes sense. But with the stealthram I would loose considerable torque down low. I want to keep my torque and gain high end as well..know it is asking alot But im sure that supercharging and the right combination of parts will get me there.

to 83Crossfire TA :

You bring up some very interesting points! One of the reason Im going with the D1 is (have talked to procharger before starting this thread) is that is have a much more peaky build curve because of the helex impeller. It wont build much at low rpm but at higher rpm it will build pressure more exponentally that the P1. that should give me the most effektiveness from the Supercharger where the manifold is most restrictive.
You say that manifold design have little to do with torque down low.Can I get you to explain that in more detail. Im under the impression that manifold design have everything to do with torque down low.

The reason that my upgrades on the car seem a little backward is that it threw a piston so I had the engine rebuild with a complete zz4 rotating assembly. that was all I had planned for at the time. But my engine builder offered me the trickflow heads and that cam really cheap because another customer had burned him, and in denmark those parts dosent get sold every day. I rescearched the parts before saying yes and both the cam and the heads seemed to be good parts, and for the price (50% off) I couldent say no. And with the enginetaken apart anyway it wouldent cost me extra to have it installed. Besides the heads and cam the car is bone stock. the exaust is stock too, execpt for a cat back. A set of hooker super comp headers is part of my plan (if any have a better suggestion please let me know)

When the car was fixed It pulled much harder torque down low was definitely improved and the car pulled harder all the way up..but at approx 4800 it dies. It used to die at around 4400 rpm, so the head and cam definitely did something. I dont have a custom chip just bumped up fuelpressure, so that can have an effect,I do know that the car dosent runn lean at any time.

So to answer crossfires question..YEs I like my power band very much,.I would just wish It would go another 1000 rpm higher with out any loss down low.

what about the cam dont you like ?

Thanks so much for all your imputs..keep it coming where do I send the checks

:hail:

 

I'm not advocating any particular manifold, just any improved manifold. If you like the one from First, by all means use it. Looks like an improvemnt, though I haven't actually seen one in use. check the aftermarket review boards, see if anyone's talked about it there.
Try this guy, maybe he can give you some more info.
http://www.vettepics.com/1982_d.shtml
or this guy, he used one on a big inch small block
ncarboni@ccmail.racal.com

Either might be able to give you some more info on how the product works.

 

My point is that the bottle neck IS NOT at the intake. If an engine is just a big pump, and you have to get air THROUGH it to make power,.... you really need to concentrate on getting it out AFTER the intake and AFTER the cylinder. You will not have a problem getting boost into the cylinders, no matter what intake you have,.. it's getting it out, with the right cam, heads, exhaust and what not. All the other stuff like intake size, and whatnot are much less signifigant in a boosted application. IMO,.. maybe i'm wrong,.. but i damn well know that the bottel neck is not the intake, and the bottle neck is the rest of the exhaust part of the "air pump". in a N?A situation, you can concentrate on getting the intake or carb flowing perfect and acutally come close to 100% volumetric efficiency. It matters MUCH more in NA. maybe as much as getting it out

now just a pointless retarded comment to add: ( not trying to make a real comparison here) . Isn't it ironic, that a s/c is a airpump too, and what matters most is how fast you can get air out of it and getting air to it is much less of a concern? so my point is, we are getting alot of air into the motor regardless. Now we have to work on getting it out and volumetric efficiency and how to avoid heat whatnot.. those are the issues to concentrate on. Infact, a NOS system is now being compared to "forced induction" because you are essentially doing the same thing as a blower is. forcing air right? now, that being said, when you run NOS, Do you worry about the tpi intake size?.... not really.. what do you guys think. ? thanks

 

My question to Justin would be, if the TPI intake was not a bottleneck, why did you replace yours with a SuperRam? I'm not trying to be a punk either, I just wanna know. I dont know the math behind determining when the TPI intake would restrict you at higher RPM's, but I do know it happens to people. I always thought the length of the runners play a part in where the intake is strong (as far as the powerband). I look at the intake as one of the many parts along the path the air flows. First would be the S/C, then the TB, then in the intake, then the heads, etc. If the S/C, TB, and heads all can handle X ammount of flow, but the intake can't, dont you think it would be a restriction? Isn't there a reason a ported TPI flows 230 cfm, and the unported StealthRam flows 275cfm? If the flow didnt matter, then why would people care?

And another question for Crossfire; At what point do your heads restrict your powerband? I always thought your cam and valvetrain would dicate your powerband, and the heads would determine how much power (flow) you make. Better flowing heads will make more power, but do they also allow you to rev higher? Comparing two identical setups, one with stock heads, one with aftermarket. Wouldnt they both pull to the same RPM, just one making more power (thus going faster) than the other? I dont see why the stock heads would play a part in the powerband dropping off @ 4,500-5000 rpm on the stock (intake/heads/cam) setup. I can understand that stock heads wont make as much power, but it really feels like the powerband just ends around 4800 rpm for me. I would think its more of a cam issue. But then again, I'm not afraid to say I dont really know, so if you could school me I'd appreciate it.

 

didnt electromotive give up on selling this intake years ago or are they still selling it. this intake, this exact one, has been available for like 10 plus years...

 

Ok, ok, I give up, forget experience (personal and the thousands of hours talking to others), forget the bazillion discussions of this on the tpi and general tech boards, forget air flow theory, and forget the hundreds of dyno tests. The stock manifold isn't a restriction and flows just fine.

Agreed the exhaust needs to be done, notice that earlier I said I "assumed" that with the heads and cam he'd done some exhaust work, and that I made a crack about assuming at the same time. Also notice that he said he's got exhaust work planned so that subjects already covered.

i'm not crossfire, but in answer to CrazyHawaiian, your heads will affect your powerband mostly by their control over airflow. If they don't flow enough air to support the higher rpms/power level
, or if they don't have enough flow velocity in the lower rpms/power levels to fill the cylinders.

But once again it's just like I keep saying, it's the match of parts that makes the difference. The heads, cam, intake, exhaust, power adders, all work together to dictate powerband and power levels, not just one particular part.
I still think that the wrong supercharger is being considered anyway. If he only wants to run 6 pounds of boost on a fairly mild engine build, run the p1sc, it's cheaper, will come on quicker, and more closely matches the rest of the parts in his build.

 

crazy hawaiian,
My answer is that i changed it when i thought Bigger is better years ago, and I was running N/A,.. so it made a much bigger difference.
Ruarc31,
you're right the tpi is somewhat a restriction,....however, not nearly anything measurable. and if you read my first post, way up at the top of this thread.... i was saying just what you are now saying.... the match of the parts is what matters....they all have to work to gether and be mathced,..BUT i'm just saying that right now,... the tpi he has isn't his restriction,..yet, it's not where he has to start,.. he has to concentrate on the other things ew mentioned,...exhaust,,cam, heads, and whatnot

 

I was just asking because I'm gonna be putting a StealthRam on my blown L98 with stock intake/heads/cam. With the right cam and valvetrain I'm expecting it to pull to 6,000rpm. Thanks for the info though because if it does not pull like I expect at least I'll know what the problem is. I just dont wanna buy heads yet because I plan to ditch this 350 soon and build a Motown 400 block. I know the bottom end of my L98 will not last that long with my power expectations. So what do you guys think are the limits of the stock L98 heads? Do you think I'll pull to 6,000 rpm?

 

Crossfire you dont understand... Im pointing out that atmospheric pressure IS what moves the air into the engine when the pistons lowers the air pressure. air only moves when there is a pressure difference, after all. I was using "boost" as an example because people understand that word better than relative pressure difference. See? 14.7 PSI out here with 14.7 PSI in the motor is WOT... 98~KPA... so we have 14.7 PSI of "boost" even though it feels like nothing because its the same pressure as our atmosphere at sea level.


SO lets shorten my post. the MORE power an engine makes before you slap on a supercharger, the MORE power it will make with that supercharger at the same boost level.

since no one here has a N/A TPI car making more than 340RWHP, please be re-assured that ditching the TPI to make more power is always a step in the right direction. always. do the math!

 

For the most part, I agree, that is why I started my last response to you like I did.

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As for the torque down low, here's where I do disagree with you. The intake does have quite a bit to do with this. Too much personal experience, too many dyno sheets posted on this board, and in different magazines doing comparos and test and tunes have proven otherwise too many times to count. Now in our cars in specific what happens most by going to a better flowing intake, especially one with shorter runners, is a FLATTENING of the torque curve, where you may lose 20 or so lbs/ft down low, but gain them up top, and the middle will stay close to the same, assuming all other parts stay the same of course.

IT’S NOT THE SHORTER RUNNERS. If you slap a bigger intake, irrespective of the length of the runners you’ll kill velocity at low rpm’s and loose some low end torque. Again, there is no tuning that the TPI does that you will feel under 3900rpm…

Simple question. Most people swap converters fairly early on… What converter do most LT1 guys go with (is recommended by say PI, yank…)? What converter do most TPI guys end up with? I’ll give you a hint… they almost all go with a 2800-3000rpm converter. Now if the TPI did anything usable to the bottom end below that (and we’ll all agree that the LT1 manifold with it’s 2” runners does not), then why is that the converter of choice?

I guess you got a little ahead of me.

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Im very interested in info reg the F.I.R.S.T manifold because it is said that it is the only LTR style manifold that can make use of the harmonic tuning around 5800 rpm, thus making it great for both low and high rpm. Does anyone know anything about it?

Personally, if you’re going to spend money I wouldn’t do it on what is basically a TPI design for 2 reasons… most parts to upgrade a tpi cost close to as much as what it would cost to replace the whole thing, and the basic tpi design has a flaw in it which I suspect that GM kept the runner sizes low. It has a crappy port entry angle where it meets the head, which results in turbulence on the bottom side of the port. With good velocity this doesn’t matter that much, since you just end up with a pocket of air that the rest of the flow rides over… if you loose velocity it will suddenly become a restriction. If it wasn’t for cost and you really wanted to stick with a LTR manifold I’d tell you to look at the superram.

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You say that manifold design have little to do with torque down low.Can I get you to explain that in more detail. Im under the impression that manifold design have everything to do with torque down low.

I think I’ve already mostly answered that, but basically what I’m trying to say is that the TPI design isn’t really the reason that the engine has a good low end, any manifold that maintained port velocity, irrespective of runner length would have roughly the same low end.

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what about the cam dont you like ?

In general, I don’t like the crane lobes and feel that the compucams were designed mostly to fool the buyer into thinking that they have something that would give them a significant improvement without messing with the ECM… In the end you end up with something that looks bigger on paper but acts a lot like the stock cam.

Stock L98 heads top out in the mid 170cfm range on the intake ports, a stock TPI intake flows a little over 200cfm… the heads need to top out a little higher then the intake because of valve timing/lift. You won’t gain anything (besides “I think it feels better”) until your head flow exceeds somewhat over 200cfm roughly .050-.100” before your cams max lift.

170cfm is less airflow then a 350 will use at 5000rpm, which is why the stock L98’s won’t rev.

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but do they also allow you to rev higher?

yes.

No, I understand… I’m telling you that NA you’re not going to have any pressure differential forcing air in besides that which is created by the piston dropping in the bore (and only if you restrict airflow while it’s happening), and you’ll still have to fight atmospheric pressure to get the exhaust out.

Boosted you get a pressure differential forcing the air in the engine at a greater rate then just what he piston dropping in the bore displaces…

 

<b>No, I understand… I’m telling you that NA you’re not going to have any pressure differential forcing air in besides that which is created by the piston dropping in the bore (and only if you restrict airflow while it’s happening), and you’ll still have to fight atmospheric pressure to get the exhaust out.

Boosted you get a pressure differential forcing the air in the engine at a greater rate then just what he piston dropping in the bore displaces…</b>

But thats my point crossfire, if atmospheric pressure was 1 PSI less then thats THAT much less pressure available to push air in. My point was not to show that atmohspheric pressure is boost, but that pressure is what moves air, and pressure directly affects the density of the air moving into the engine, besides tempeurature. YOUR the one that told me THAT!

In fact unless im mixtaken, you can take two pressure differences at the same tempeurature and directly respond with % torque differentials.

For instance, Identical motor, making 1470 Torque @ Sea Level (14.7 PSI) would make 1350 Torque @ 13.5PSI (XXXX Elevation...)

ALL else being equal. Which is why i say, the more power the engine makes before you slap on a supercharger, the more power it makes at the same boost level. which is why ditching the TPI is never a bad idea for power.

 

Interesting to come back to this thread after a couple of days and see that people are still talking about the stock heads as a restriction etc etc when Has clearly points out he's running Trick Flow heads. And if your talking about your own setup, well start another thread, don't hijack his.

And I'm just gonna have to agree to disagree with you on the intake. Runner length and diameter do have a relationship to the powerband. Especially in conjunction with the rest of the airflow path, including heads and exhaust. There's just too much of a mountain of evidence that it does matter.

And all that's beside teh point, what the real point is is that Has has to make a decision, because if he really wants the engine to pull to close to 6 grand, he's gonna have to give up a little down low. If he matches the parts right the sacrifice will be minimal and he'll still be able to smoke the tires at will and rev up to 6 grand. If not he won't.

I personally would have done some different stuff, but with what he has, I'd do some free intake porting, or maybe do the runners and base (the first manifold if he really has his heart set on it) and drop a 100-150 shot of nitrous on it and be done, he'd have everything he says he wants for less money and hassle. If no N20 then spend some time tuning the supercharger belt ratio to make sure the boost is coming in at the right time. Call up ATI and grill 'em. Call up the cam manufacturer and grill 'em. Then prepare to spend some time tuning the computer or no matter what he does he isn't gonna like it.

 

Sorry for 'Hijacking" the thread. I know he has trickflow heads. What I didnt know was that the flow of the heads can directly affect your powerband independant of your cam or intake. Sorry for using my heads as an example in my question. This info can be usefull to anyone reading this thread (now, or in the future using search). And I think considering the subject, it was not a bad question to ask. Anyone who wants to know how to pull to higher rpms will benifit from knowing that.

So here's where I'm at now: He currently has the stock TPI, aftermarket Trick Flow 64cc heads (195cc in, 75cc out), and the aftermarket Crane 2032 cam with an advertised 2,000 to 5,500 powerband. His powerband still ends at 4800 rpm (just like my TPI setup with stock heads and cam). So considering all that, what is making his powerband end @ 4800 rpm? Do his heads still not flow enough or do you think its the intake?

 

So here's where I'm at now: He currently has the stock TPI, aftermarket Trick Flow 64cc heads (195cc in, 75cc out), and the aftermarket Crane 2032 cam with an advertised 2,000 to 5,500 powerband. His powerband still ends at 4800 rpm (just like my TPI setup with stock heads and cam). So considering all that, what is making his powerband end @ 4800 rpm? Do his heads still not flow enough or do you think its the intake? [/B][/QUOTE]



Its the intake, of course. If he swapped over to a stealthram or somthing similar (even a dual plane carb manifold like the performer RPM with a carb on top...) he could easilly jump from his current 300~ RWHP to about 350 RWHP... just because of the restricive intake being gone. then with the right cam those heads can put him in at over 400RWHP if he gets somthing big enough. Even edelbrock heads which flow less put you around 400~RWHP with a mild 234/244 cam. The TPI on a motor with heads and cam like that is only hurting... sort of like mine. My AFR's and Cam make decent power from about 3000-6500RPMS... but the TPI only want to do the 3000-4500 RPM part. So im basically stuggling to get off the line, i hit my peak area for about 1000 RPMS worth, then Im struggling again to work my way up from there. its a bass ackwards way of doing things for sure.

 

OK, then we’re on the same page… My original problem was with you saying something that roughly equated it to boost (to lazy to go look what it was).

I never said that it doesn’t. I said that the harmonic tuning that the TPI setup is hitting is not helping you any below 3000rpm, and nothing that it’s doing will be particularly felt below the high 3K range.

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And all that's beside teh point, what the real point is is that Has has to make a decision, because if he really wants the engine to pull to close to 6 grand, he's gonna have to give up a little down low. If he matches the parts right the sacrifice will be minimal and he'll still be able to smoke the tires at will and rev up to 6 grand. If not he won't.

I personally would have done some different stuff, but with what he has, I'd do some free intake porting, or maybe do the runners and base (the first manifold if he really has his heart set on it)

Right, and I already answered that… not knowing his budget I don’t know how much he’s willing to sink into this, but he’s not going to be doing any real revving or making any real power if he doesn’t address the exhaust first. SuperComps are fine if you’re willing to deal with the inconvenience. Y/cat back will probably also have to be addressed, especially if he goes with the supercomps…

Um, stock exhaust manifolds?

There’s a local guy that just built a TFS headed 350 TPI to replace his 305(using almost stock TPI parts… I’m pretty sure his plenum is cleaned up), mild cam, headman headers/ypipe and what was originally a flowmaster cat back (he added some different muffler to it, I don’t remember what). So far he’s run his best times shifting at 5500-5600…

FWIW, what it feels like it’s got power till is pretty different then where it’s actually making the most power under the curve. EX, my stockish L98 revs fine till almost 6K rpm, but runs the fastest at the track shifting at between 4400 and 4600…

 

Ahhhh! That must be it. His exhaust. Totally forgot about that aspect of the combo. And it would explain why the same thing happens to me (power drops off @ 4800 rpm) considering I haven't installed headers yet either. I jokingly refer to my car as the constipated man in a pancake eating contest. Well hey thanks for all your help guys! I've learned alot from this thread! I'll be sure to install headers before I hit the dyno. I wanted to do a baseline run with the TPI and stock cam @ 6 psi. Then I want to do the HSR and blower cam/valvetrain swap and see how much more power it makes. Thanks again guys!!

 

Did you happen to read a word i wrote people? am i invisible? Either agree or disagree with me, but dont ignore me!

SOMEONE PLEASE tell everyone that TPI is bad for performance?

 

Disagree.

Nothing wrong with TPI for what most people call performance...

 

Hehe dont worry bro, I'm reading what you say. I do agree that TPI does not flow as much as some of the aftermarket Intakes out there, but I'm not sure when the TPI becomes a restriction. From what I've read, the stock heads and stock exhaust pose a restriction way before before the TPI intake becomes a restriction. So thats where I'm at now. All this time I thought my intake was ruining my powerband, and turns out its my exhaust and heads.

But like you've said, I have yet to see someone put down over 375 rwhp N/A with the TPI. People with modded TPI motors usually put down insane ammounts of TQ instead. Works good at the 1/4 mile, but not as much fun on the freeway at speed. I prefer high revving high end power, so I know the TPI is not the right intake for me. Others might prefer more torque than horsepower, keeping the powerband below 6,000rpm, then the TPI is a good intake for them. After all, you dont need to rev to win, I just think its more fun.

 

I guess I missed the long line of LT1 owners putting down more then 375hp to the wheels with their "superior" manifold...

 

No, then you AGREE! I think TPI is GREAT For performance. I RUN TPI! I was just kidding about the whole TPI performance = bad thing. baiting. you know, the usual crap.


Actually What i was thinking was more along the lines of that TPI sucks for Horsepower, I guess. I mean unless you run a 250 shot or 15PSI of boost, there are far easier ways of putting down power than trying to squeeze the TPI for what its got. In my opinion of course.

I hope everyone understands im still slightly tipsy from all the brakecleen i was using to clean / assemble the motor and I found out that if you inhale enough of it you start to see some weird $#1T.

 

the new environmentally freindly stuff or the old stuff?

Funny how the new, "safer" stuff is MUCH, MUCH worse for you (it will actually absorb quickly through the skin and any decent exposure will give mild chemical burns, the old stuff did neither).

So what exactly are you seeing?

 

thats too funny. I dont really remember, but everything was sort of moving around even though i wasnt. kinda like when you stay up for too many hours. i was also seeing little black dots everywhere.

Using the stuff in the red cans... I guess your refering to the stuff in the green cans right? without the chlorine? I never tried that stuff, just assumed it wasnt as good since i figured like anyone else... "NO chlorine? DAM!"

 

it's not even a good/bad thing, they're just different, and the grean can stuff is much harder on the person using it...