Grumpy

Now that MiniRams, are so popular it might be more an appropriate time to share some of the measures I took with the 89 TTA upper manifold. The two have an identical problem, IMO.

As a primer, the interested reader might refer to this old article I did in reguards to correcting the rear cylinder leaness problems, and plenum modifications.

http://www.gnttype.org/techarea/engine/plenum.html

And one of the key elements in realizing in part what was wrong was reading up on Heating and Ventilation. Yep, household furnace ducting.

One other idea was something Smokey wrote in one of his Popular Mechanic articles in the 60's. That was, corners, and manifolding was not as serious of downside, as one might believe.
And that with any manifolding compromises were going to have to be made. Back when I was executing some R+D engine design, we were working on an engine that was 3 HP per CID, N/A, and BTW, this was in the 70s. Anyway, this one engine was going into a hydroplane boat, and packaging was a real task. We had developed an intake on the dyno that was just impossible to get under the boat's cowling. The solution working back from the boat requirements and not cutting into any of the cowling meant going to a single larger carb., and having it blow against a vertical wall, and then having the ports point vertically into this chamber. This odd looking box, wound up costing less then 1% in HP, and saved breaking the streamlining of the cowling. Point is air and fuel will try to stay in suspension. It's about inertia, and in the carb world atomization. Just as mirror poishing of ports and runners will cost you HP, things that might really slick to a human, maybe meaningless to an engine.

Now if you read up on the heating and ventilation stuff, you notice that on a long run of vents, that they suggest the main column extend past the last vent by 1.5x the vent's opening. So if the last port is an inch wide then the plenum's rear most wall should be 1.5 past the last runners opening into the plenum. While the manifold I did exceeded that by some measure, I was also looking to increase the plenum's volume. And all the plugs now read as evenly, as the human eye can detect.

And on the 1.5 open area spacing around a runners opening, one of the best examples is an indy engine at the Garrett's Muscle Car Museum. Also, in Passini's Weber carb book he mentions it. Thou in these two areas they talk about clearances around the end of an injector stack or carb throat, the end of a runner is the end of a runner.

What I found most interesting, once I bolted the upper plenum on, was that I had to increase the PE AFR by 6%. Since it's about a 2:1 ratio in HP to fuel that would equate to about a 12% increase in HP, but since this was a turbo as HP goes up you also have to increase the fuel loading to help keep the engine out of detonation. So I see it as more likely being a 8-9% increase in HP, and of that I'd split the difference from the plenum volume to rear wall correction. Anyway, you may want to slice it, 4% for such a minor change was exxtremely worth while.
I also had to add some TPS AE, since there was a larger volume of air to acclerate.

One thing I really like about the 89TTA setup is the Monoblade. And this again goes back to the boat program. Air has alot of inertia. While most people think liquids pour, air while about 1/600 as thick as water, behaves like a liquid as far as it's ability to change direction. Anyway in other programs we figured out that going to what would seem to have been way too large of carb dropped the air's velocity enough to allow it to makes the bends, and transistions easier, when running blow against the wall manifolding. A quick glance would show some of what GM was thinking if you look at an individual runners cross section and one butterfly's opening. They, IMO, seem to want to impart alot of inertia into the air stream to fully utilise the tuned length of the runners. Bumping up the engine's air consumption, also means needing to lower the air columns speed to lessen the inertia involved, to maintain optimum cylinder filling.
Also explains in part why you don't see the HP you would expect with just changing the TB, in some cars.
As of yesterday I just installed a 3" monoblade in my car. I would have thought changing to that large of blade would have made a serious change in all the AE stuff, however, initial testing shows things are pretty close.

Pablo

iTrader: (1)

Neat post

JohnL

Thanks for the info. I second the vote for "neat post".

I don't understand how you can increase fuel by 6% and expect a 12% increase in HP though. That means that you're increasing your fuel efficiency as you increase the fuel load- how does that work out?

John

PS, I note you're also talking about AFR, not VE increase. I assume you meant decreasing the AFR (more fuel). If you're getting more hp, it's coming from increasing the VE, right?

LnealZ28

Actually, applying the pricniples of hvac ducting to intake design makes sense. Being in the HVAC business, I have often thought of intake tracts in the same way as ductwork. All properly done duct systems will have a plenum or trunk line, and individual "runners" to each register. I was taught to look at the plenum as a pressurized chamber, rather than in terms of moving air through it, much like manifold pressure. The difference is that the pressure in an a/c duct is static, where it varies with an intake tract.

Glad to see I'm not the only one who benefits from this analogy.

Twilightoptics

Very interesting analogy and concept.

It would make sense for air to have intertia, after all it is a mass of sorts.


When talking about plenums like your upper manifold, tpi, hsr, miniram whatever.... one would think that carbs and tbi setups give a more even airflow to the cylinders because of it's central base... there really isn't a wall for the air to run in and hit like there is in our injected setups.

Makes me glad I have a stealth ram with the big fat plenum!

LnealZ28

I've thought that also, and have entertained the thought of using a single plane carb intake modded for multi port EFI (like the Edelbrock Torker II) instead of the TPIS MR I've been considering. The air would still hit the bottom of the manifold, but it would seem like the air would be more evenly distributed because it would spread out evenly into the runners when it hit. Or so it would seem, I could be wrong............

Now the little gears in my head are turning..............

AlexJH

Grumpy, in your article, you mentioned a 2:1 ratio for plenum volume to engine volume. Is that for forced induction apps or does that apply to n/a cars?

I''ve never measured my TPI upper plenum but I'd assume it was only about 3L, maybe 1 more litre in the runners (if those count).

Grumpy

Your even more correct, then you might think.
While in N/A applications, it atmospheric pressure the rushes in to fill the vac of the piston moving down. In boosted applications, you have the PRESSURE of the plenum actually pushing the piston down. And in that realm it's about PMP. Peak Manifold Pressures. ie now much the plenum pressure Drops as the intakes open.

It's this changing of using vac to fill a cylinder to pressure pushing the pistion down, that causes the HUGE changes in VE, and the results in the code and tuning to keep the AFRs right.

The Sy code with it's boost multiplier table is an interesting item to work with. So instead of just have to get the main VE and PE right you in addition get it right. Again, it's one of those things that you have to know how the code works to tune.

Kinda rattled around here, but the conept of pushing the pistion down and pressure's and tuning all are pivotial in how it works to how to tune it.

Grumpy

Ahh, but carb manifolds have a floor rather then rear wall, so they in effect are fighting the same laws.
If you really get into carb stuff, then you'll note that the booster height to floor distance is an issue. As well as butterfly size, air speed, fuel atomization size and keeping the fuel in suspension.

And with the large the plenum the more likely you are to want more AE TPS, at the lower deltas.

Grumpy

You got it.
BUT, with the floor, it effects all 8 equally.
If you look at the manifold on my web page, the one hidden detail is what I did with the runners, and floor


Just remember in manifold sizing you if you go port, the runners are no longer carrying fuel so they are a bit larger then what you may want.

Grumpy

The 2:1 is for the high HP turbo applications.

Runners don't count.
Measuring the plenums is allows interesting, looks can be misleading.

And again as you increase the volume, you increase the signal dampning some. Might, might not, be a concern, but something to be aware of.

11sORbust

so you like the monblade TB? I have been eyeballing GM's v8 CPI monoblade for awhile. I'm thinking it could work with a 4b carb intake. Just make a TB adapter plate and weld 8 bungs...

Grumpy

I have a FBW, Fly By Wire, LS1 TB here, that's begging to have an ecm run it. Plan is to use the injector output to run the servo. ie devote an ecm to just running it, and leave the fuel and timing under normal ecm control. It would be run in conjunction with the stock TB. That way there is no need for redundancy controls that the oems have to rely on since this is just for triming the air opening rather then controling it. Kinda like a carb with a thinking set of secondaries. Be nice to optimise the actual air flow as well as fuel and timing. Lots of tuning to get that right. But I think even a simple ecm is more then configurable for doing this.

ScotSea

iTrader: (2)

Let me fully understand this. How do you define VE? What is the equation that you are using for VE?

How are you then measuring VE, to know that you have huge changes?

Been my experience that VE changes very little in boost on my turbo car. I measure VE every time the scan tool is connected. I have an LT1 MAF out in front of my engine, but I only use it for measurement purposes. I then calculate VE using the MAF data, and compare it to actual table VE used in the SD calculation. Very little change in VE (on my car) once in boost.

This makes me curious how you are getting and measuring the huge changes in VE.

Scot

Grumpy

Mechanical VE.
By huge changes, I mean while a N/A street engine is hard pressed to get to 100% VE, a turbo motor can easily do 120%.
I didn't mean to infer that it was just at that point that things changed drastically. Rather that begining there, that it allowed for going much higher in mechanical VE.
Better?.
Nothing better I'd like to do and be able to data log actual airflow, and do the calc's. But, I still have a ways to go to get there.

ScotSea

iTrader: (2)

What is the equation for mechanical VE?

Scot

18436572

Very interresting post!

You might like to know that I have just finnished a project that falls along these lines . I took an LS1 throttle body and modified it so that I can run it on a TPI setup. I had to make major mods to the plenum of the TPI. I mounted the LS1 TB upside down so that the throttle cable connected to left side of the engine.

I really thought that I would have major changes to make in the BIN but I did not have to make any changes due to the throttle body change. The pintel on the IAC looked a lot larger
than the one on the TPI . I thought that I would have issues with this but not one . I was supprized at how well the LS1 TB and the 8D worked together. The biggest supprize though was the increase in low to mid throttle responce . This TB change also gave me more power all the way through RPM range. Any way I had a whole lot of fun with this project .

ED

BIG_MODS

iTrader: (9)

What is the cfm for the LS1 TB? Or what is the advantage, may I ask?

JPrevost

Ahhhh... I love this kind of chit chat.
My manifold design background might not be too relevant but there are a lot of things that normal people don't even consider when they think up a design change. First and foremost, in a n/a engine with a large enough plenum, you can consider the air inside the plenum to be near zero velocity. For this reason alone, it's VERY difficult to measure actual gains between plenum shapes.
Log manifolds really aren't too bad except that the cylinder distribution will always favor the cylinders closest to the TB entrance, but not the closest, well.... it depends, still they aren't awful. A centralized design like a single plane manifold has a lot of advantages over a log style. First like posted earlier, the distribution equality is usually very good. This however isn't true just from the fact that <0.01% of the v8's in this world are flat cranks . Darn firing orders always mess things up.
I have no experience with twin vs mono blade so I can't comment there only that a mono makes heaps more sense than a twin. If not for the simple reason of pumping loss' , just look at how a plenum works. It is always flowing so why bother with an air foil in the front if there isn't one in the rear, you'll only trip up things more with a twin resulting in less flow potential if similar area. Then there's the fact of 1 short shaft and long "plate" butterfly vs 2 shafts with short butterfly’s, it's easy to see the benefit for laminar flow.
Now to the actual diffuser, this is a very important part of a restricted engine (I should know). What is bad is having the TB directly connected to a plenum. You want a smooth ~7 degree diffuser for at least a few inches after the TB, this will help a lot in increasing your TB's flow potential. This area isn't considered plenum volume because the velocity of the air is much higher. This is how you increase cfm if limited by TB size. It's really amazing how critical this area is. After all this talk one wonders why GM used the L98 twin tb on the 502 Ramjet engine when a monoblade would have probably been best.
Grumpy, FBW... that's just cooler than cool. Too bad they banned it in our competition . Something about college students rushing together a project of FBW that worries even me. I guess when you consider the acceleration of our cars it's probably for the best that it's banned.
I presume you'll be running a mechanical throttle body pre EBW just incase something does go wrong.
I think the best part about FBW is the traction control (includes launch control). Man oh man would that be cool to do. Run your best 60' times every time, eliminating one more variable in a tune. Please e-mail me if you want any help, my EE buddy is thinking about it for his senior design project and we have a bunch of SAE papers on it's operation.

Pablo

iTrader: (1)

Can you elaborate on what you mean by a diffuser?

Im imagining like an upside down velocity stack under your throttle body, basically small (TB size) to big(plenum size). Is that it?

JPrevost

Yup.
Basically you don't want to run a throttle body into the middle of the largest side, best to go in from a smaller side. Only other analogy that might make sense is a 2 liter bottle, it has a pretty good shape if the cap was the TB. Only thing you would do different to help with distribution would be to round the end. There are lots of little tricks to making just as much hp with less TB, the idea is to slowely diffuse the air so it doesn't seperate from the walls of the entrance to the plenum.

18436572

I have to be honest, I did not apply the principles that JRrevost describes. I really do not understand it that well. I just held up the two throttle bodies side by side and it seemed pretty simple that the LS1 had to flow better. I did however figure the area of the butterflies for each throttle body. The LS1 had about 800 more square mm's. Besides a friend of mine told me that it could not be done and there you go.

LnealZ28

Ya'll have got to stop this. My mind is going nuts with new ideas! Hmmm........a single plane carb intake modded for EFI with a monoblade TB anyone? Hmmm......... Maybe I should rethink this Mini Ram thing??

18436572

Well I have a long term project in my head. I am going to build a big block with a tunnel ram with dual LS1 throttle bodies, I am currently trying to figure out what size injectors to go with. I gues that depends on the how hot the big block ends up. The LS1 TB on the TPI is just a prelude to bigger things to come. I do have several projects for friends to wrap up first. One of these projects is a LS1 TB on a LT1 setup, should not be a problem but it will be fun.

SATURN5

Hehe......

Just wait til I finish fabbing up my intake..

Its just a old useless crossfire...

BW

11sORbust

cool

JP84Z430HP

Rading this makes me understand how the GM Vortec 350 intakes work a bit more. Now I'm wondering how well one of those would do for me instead......Maybe I'll try that out before I put any TPI setup on, I do have 2 complete, and one less injectors down in the garage.....

Those tiny little gears are turning in my head now, too!!!

Grumpy

Just to kinda follow-up, expand upon what Jon had to say. Yes, there are angles of convergence, and divergence that you want to follow. A cross section view of a carb shows an effective way to organise and acclerate air, with a min of muss and fuss. You can continue that same train of thought to runners, and the throttle body area. And there are things to keep in the back of ones mind. When folks talk port velocity, they are about always talking average. So depending on what all you're doing there is that once in a while when nothing makes sense time, when you may be dealing with a limited trans/ supersonic air flow. Do I have any hard data to support that theory?, No, but I offer it as an explaination for when thing just don't make sense. It just seems that in the past, there's been a few times, when I had something bottle neck, that it took alot of work to take a completely different plan of attack to get somewhere.

So while Jon's explaination is fine well and good, I've gone off on another tangent. I've replumbed my intake to take advantage of the pre Throttle body area, as being addition plenum volume. With the big throttle body, ie 3" monoblade, I'm hoping to in a way accomplice a variable displacement plenum. In the N/A world runners are critically important since they allow you to tune and acquire an quasi boost situation, at very specific rpm points. In the boosted world the T/S Charge does that for you. So while the runners generate a positive effect at some RPM levels they do an equally bad thing at other points. My contention is that in the boosted world, runners are just a means to connect the ports to the plenum, and plenum volume is what allows for quick cylinder filling.

Anyway, here's a few new pics showing the latest plenum, throttle body setup.

http://home.woh.rr.com/brucesgn/

Grumpy

I had been quoting Alan Lockeed.

But, I can see that it would be far better to do the actually testing, and use that data.

After thinking about this for the last couple days, I think I've come up with an answer. Since I have a couple LT/LS1 MAFs laying around here, and I think I know of a P4 ecm that uses the high frequency style MAFs, and a freq to gm/sec table for the LT1 MAF. I'm going to incorporate the MAF into the intake tract. Then feed the *other* ecm enough to be able to data log the MAF and then maybe input the WB into what was normally the TPS, and take that route. I can use my freq generator and counter to edit the MAF tables and scalers to use these other MAFs.

And since I'm independent of the VE tables, I can reverse engineer all that data to line up how things should be.

Glad, you mentioned that.

JPrevost

Grumpy, why don't you have the compressor out point towards the intake in? This would help shorten up that ducting.
What I was talking about has very little to do with big TBs but one area of your car that might benifit is the compressor out. I recall you testing a few different pipe diameters. I bet if there was a tapper out you would get the best of both.
Is there any way to move the turbo up a little higher so you can get a straight shot towards the throttle body? If you could, the tapper pipe would be a lot easier to build .
Also, instead of having the 7th injector where it is now, move it to the compressor out, right before it starts to diffuse. Just a thought.

Grumpy

Not sure what you do mean, but, angles of convergance, and divergance for manifolding are constants.

Odd as it may sound once you spin the housing around, you still have to have make 90d turns, and you can only mandrel bend tubing so tight. If I had access to hydro-forming then sure I could do all sorts of things, but that's just not the case.

If you look at the newest pics real close you can see a brass fitting on the compressor housing By no means the perfect location, but, before I start drilling holes in a compressor housing, I want to evaluate if there is any difference from what I have to moving it closer to the compressor wheel. There were several classified fixtures removed before the pics were taken.

ScotSea

iTrader: (2)

No kidding.

Your statement that the boost was "pushing the piston down" scared me a little. The air going into the engine is flowing from a higher pressure area (the plenum) to the lower pressure area (the cylinder). Don't think of it as pushing the piston down.

The problem is that none of the assumptions with the VE calculation you were quoting were also presented. That is why I was asking for the equation you were using. Just trying to get you to see the error there.

VE is the actual airflow into an engine divided by the theoretical airflow that the engnie could pull in. The assumption that you were using restricts the theoretical airflow to the airflow that would be there in a N/A situation. That assumption does not work for the VE value that we use in ECM VE tables. This is what I am trying to get to.

An example: Say you have a 5.7L engine pulling in 190 gps (MAF) and running at 3600 RPM. What is it's VE using your formula? It is 190 gps/205 gps, or 93 percent VE. (The 205 comes from a 5.7 liter engine drawing in 5.7/2 liters of air every rev, times 60 revs/sec, where a liter of air has a mass of 1.2g/L.) If you apply boost to the engine, and get say 255 gps of airflow at the same RPM, you will get 255/205 or 124 percent VE.

The VE used in an ECM VE table can be thought of the amount of manifold pressure that makes it to the cylinder. That is why ECM VE tables do not need to go over 100%. That is why the boost fuel multiplier can be misused. It is only a trim to PW for increasing pressure. If you are using the table that is in the example that you sent to me, I think that the table is being very misused.

Scot

LnealZ28

Don't mean to butt in on the VE discussion, which is interesting, but I had a thought.

So, I've been debating this intake idea the past couple of days and was wondering what you guy's thoughts are on these ideas. I don't really like the idea of using an elbow that adapts the TB to the carb opening, besides I'm not aware of one for a monoblade. Since I don't have any software to make neat drawings, I drew it out on paper and took a pic of it. Nothing is necessarily in scale, obviously! It's a Torker II manifold, the plenum follows Grumpy's lead and the basics of a/c ducting. The transition will go from the size of the TB outlet to the plenum size, making the transition easier for the air. Plenum and transition made from welded aluminum. I will take dist. clearance into account. This is a N/A app. My car has a cowl induction hood so I have plenty of room for a nice big plenum. Beautiful part is, it's custom made, very DIY and can be made to look good. Ain't EFI grand!

BIG_MODS

iTrader: (9)

You're not the first with that idea

https://www.thirdgen.org/techbb2/sho...hreadid=210366

LnealZ28

Damn guy stole my idea!! Seriously, it does mean that someone else thinks it's a good idea as well.

SATURN5

For what it would cost to fabricate it, a Holley Stealth Ram would be cheaper and easier. But... it you have the means to do it yourself..


BW

LnealZ28

Thinking about it, I seem to recall that F**d used something similar on their 3/4 & 1 ton trucks that had the 460 in them. A 4 bbl carb intake with EFI stuff on top. Saw one taken apart in a friend's repair shop once and it freaked me out. Yea, the HSR would probably end up costing about the same or less but it's just an idea.......

Grumpy

I've read that first paragraph at least 100x, and it's maybe just now making real sense.

All my early stuff was off kilter. I have some changes to do to the car, and I'll be getting back to gathering data, and hopefully making more sense of things.