fb305svs

yeah thats right, chassis dynoed at 280hp, and 320ftlbs... on the engine dyno, it ran 433hp and 406ftlbs..

most of my torque is there by the hp is gone... leads me to believe the exhuast is a real restriction...

my set up is the LT's into the mufflex y-pipe (3" off each collector to a y to 4" but its necked back down to 3" hooker catback setup...

anyways, im thinking this might be a lot of my problem with missing hp, whats everyone's opinion - dual 3" into 3" not good enough for the motor? will the 4" mufflex setup be the solution?

just curious on educated opinons on this...

THEGENERAL

the exhaust you have isnt restrictive by far .......you lost so much because you went from an engine dyno to a chassis dyno your drive train ate up alot of it not the exhaust system

br()bert

84firebird383

The 3" system is great as long as you use a straight thru muffler like the dynomax bullet. With a single flowmaster I ran 113.5 in the 1/4 mile then 116 with the bullet and 117 open exhaust. I have Hooker longtubes with teh mufflex y pipe. The motor has gone 119 with the same set up as my firebird in an 80 camaro. I think my lost hp between the 2 cars is either airintake or fuel starvation.

fb305svs

why would it be much diff? only thing that changed was a trans and a rear, and the exhuast... engine had full accesory package on it on the dyno


35% drivetrainloss is ludicriss lol i dont know anyone who has had more than 22% loss... and that was an auto.. i help run the dyno shop, so ive seen the engine cvharts and the chassis charts...

chio987

ya, that was my thought. well can't u just unhook the exhasut at the collectors and run the dyno open headers?? since u help run the dyno i'm sure u have access to it...right? that way u'll find out for sure if it's the exhaust.

fb305svs

well if i had a jack i would have done so... i will be next time for sure...

im just bothered by the fact that its a 35% loss, and that my torque didnt drop nearly as much... its like i lost all the top end...

THEGENERAL

how fast did you get it up to on the dyno was it a short run or ??????

fb305svs

nah it was a normal dyno run - 2500-6000, 4th gear etc... nothing out of the ordinary on the run... its best to do it in 1:1 in the trans, since there is no change in the gearing, resulting in extra drivetrain loss...

nolanr0413

so your car still runs about a high 12 low 13 , then who cares what the car has for dyno hp , thats runnin pretty good, also b4 u do exhaust work , run it open when you dyno it and then lok at the diff.

89gta383

iTrader: (5)

I think you have problems elsewhere. I put down 342 rwhp @ 5900 with an older combo with slp 1 3/4 shorty headers their small 2.25 inch y-pipe and dual cats connected to their 3 inch catback and 2 on the left muffler. Dropped the y-pipe at the header and picked up almost nothing, like 2-3 more rwhp.

I think you have some tuning problems or a restriction somewhere. Did you port match the headers to the heads, and do the same with the intake to the heads?

fb305svs

yeah the intake is port matched to the heads... proper gasket used etc... its not the motor, its something that has to do with the transplant...

its a comp 282 cam... ive been told 110 lsa cams need as good exhuast flow as possible... i dunno, gonna drop the pipes on the dyno and make it a little loud and see what happens...

i have a few other things to play with, like readjust the valves (shouldnt need it but who knows), double check my igintion - its dropping 4-5* out at like 4900 for no apparent reason... u can see it on the chart and you can see it when ya rev it, so that accounts for some of it too...

might have a carb issue too... had to lean it out A LOT after the engine tune... went from 68p/71s to 61p/70s.... that brought it up to almost 11:1... still pig rich...

another intresting issue is that now it has a HORRID off cruise stumble.... just terrible.... gotta maybe put a bigger squirter on or change the accel pump cam? has an orange one on there right now... street avenger 670 carb.... vac secondaries... when i dropped the secondaries down to 68, i lost a few hp and it got richer... only explanation for that is bad set of jets?


guess we'll see.. update soon.

Marc 85Z28

iTrader: (3)

Clutch slipping any?

fb305svs

dual friction centerforce... seems to launch the car ok?


i did the math today tho - the volume of a 12" length of a 3" pipe is 84... x2 ='s 168~ going back into a pipe that only holds a volume of 84...

how that effects airflow is kinda obvious, regardless of the fact the exhuast pulses are not all at the same time... did the math on a 4" pipe - comes out to 150~, guess i'll be pickin up a mufflex setup soon

Marc 85Z28

iTrader: (3)

Rather than spend the big money on the 4" system, why not dyno it with the exhaust disconnected? Diagnose the problem, don't throw parts at it

fb305svs

absolutely- i'm not gonna kill 525 bucks for a 4" system with out making sure i need it...

i'm gonna go loosen it up where the y connection is too, so it can be disconnected right after the y at the 4" copupling... righ tnow i have it adapted down to 3"...

330hp_91RS

I just recently changed my setup after I installed the new motor. I would expect the motor to pull about 425hp, or basically the same power as you saw from your motor on an engine dyno.

I went from:

Hooker shorties
2.5 inch y pipe
3 inch intermediate
crossflow Dynomax Ultra Flo (straight thru design)

I felt that the exhaust was really restricting the motor, and I was right...

Here is what I got:

Same Hooker shorties
2.5 inch pipe ( true duals)
2.5 inch Moroso Spiral flow mufflers
No H or X pipe, just straight side exhaust dumping in front of the rear tires

Anyway, right off the bat it was a night and day difference, not really in torque but in top end.

Regardless of what anyone else says, I do not think a 3 inch pipe is adequate for a 433 hp motor.

I went with the shortest pipes possible (thus the side exit) and 2.5 inch for both good flow and ground clearance.

I like the setup except it is rediculously loud, I mean out of control.

I decided to keep the setup as is but run Dynomax bullets along with the Morosos. I'll hardly lose power if any and it should get the car a bit quieter.

84firebird383

I just got rid of my dual bullet system. It was so loud I doubt it will quiet your current system by much. You might look into car chemsitry collector inserts.By the way. My car also felt faster with the dual 3' bullets vs the single 3' bullets but at the track it was only worth 1 mph. I am betting your 2.5 y pipe was your weak link 330hp_91RS

fb305svs

no, 2 1/2 would be fine even for my motor if it was all the way back, altho i think 3" would be happier with the cam... 110lsa and lower cams like a free exhuast...

i too think that the 3" is just too much of a restriction, and even for what its worth, it claims that the 4" setup is for 400hp" on mufflex's website...

i'll try un corkin it on the dyno, but i already know what im gonna find, at least hope to find

84firebird383

I understand why you think single 3" is to small. I thought exactly the same way a week ago. From my experience its the muffler that will hold you back on a single system. You need to have one that flows about 1000cfm,like the dynomax bullet.I will be going back to dual exhaust when I have the money for an oval set up.Not because its going to make a whole lot more power than the single,but because of the sound. If you have the opprotunity try getting a dyno pull with the 3' sytem minus the muffler before you uncork the exhaust completely.

Shagwell

What intake are you running? - I had tuning issues very similiar to your's after pulling my motor off the dyno and stuffing it into the car. I swapped in a four-hole 1/2 spacer under the carb and it solved it. Must have had signal issues once it had to pull the load of the drivetrain. - that was w/ a Weiand Team "G". - I like the intake, and i know it works, just something it needed w/ my combo.

Shagwell

also, what rear gear do you have? - if you've got to much or to little gear for your combo, that could throw your rwhp #'s off.

fb305svs

3.42 rear gears - i do know that higher gears can throw the numbers off, but in this case, 3.42's aren't a terrible gear for drivetrain loss... 4.11's? yeah they would be worse for loss...

as for the intake, i'm running a vic jr intake with a street avenger vac secondary carb...

i'm gonna uncork the exhuast and see what happens - i have a cut out i could install, but it would have to go in the single back, which i might do anyways... wouldnt be that big of a deal to put it in there...

i'm gonna drop it at the headers, and see what happens... guess we'll see!

330hp_91RS

Why would the y-pipe be the weak link???

I had 2.5 inch pipe running to a flowmaster y-collector.

I don't see how that could be a weak link being that no I have 2.5 inch all the way to the exits.

As far as the Bullets quiting my car, I'll be happy with even a 2-3 db change. I am planning using the Bullets in ADDITION to the mufflers I already have, Moroso Spiral flows.

3 inch single is not too small for over 400 hp but it is not optimal.

I run a Borla setup on my 4th gen and make 390rwhp.

About the muffler being the key, I agree, which is why my Borla setup makes the power it does. BUT, the crossflow version of the Dynomax Ultra-Flo that I had claimed to flow over 900cfm and it still lacked power.

fb305svs: What I would do if the Dyno tells you that you have a restictive exhaust is run one 3 inch bullet in place of your muffler now, and if that doesn't do the trick, get the Mufflex setup.

Putting a Bullet in place of your current muffler will only cost you like $60-70 total installed, which is less that the Mufflex.

84firebird383

Sorry, I thought you had one of those kit y pipes that usually neacks down to single 2.5 in the elbow before it goes back to 3". Yours probobly did not hold you back.The car chemistry collector inserts would be easier and look cleaner plus would quite your car better than the bullets.They would also get rid of any crackling sound you might have.They also claim to give more bottom end torque

unknown_host

iTrader: (1)

To make a long story short, people on these forums think a lot more of single 3" than they should. There are people with 450 horsepower motors that post gains of 2 tenths and 2 mph in the 1/8th just by opening a cutout with single 3".

unknown_host

iTrader: (1)

I ran the single 3" with a dynomax 3" bullet, it was way too loud. Dual 2 1/2" bullets with an X pipe is far, far quieter. I couldnt have conversations in the car with single 3" because it resonated so badly inside the car.

84firebird383

It was very loud and irritating for me too when I had the bullet in the stock muffler location. When i placed it right after the mufflex y pipe it was much quieter and no resonating. I still don't really like the sound tho so I will be going back to duals.

Matt87GTA

Whaaaatt???? 35% drivetrain loss!!???? Well I must be making some really crazy power!

I agree, your exhaust is too small. 20% loss for a manual trans and slightly more for an auto is the norm when you are considering an engine on a dyno with no accessories at all (water pump, power steering, etc.) and no driveline behind it. Is the exhaust all of it? Hard to say, but 3" is too small for your power level, IMO.

David @ Thunder

I can promise you the Hooker catback is not your problem. One of the guys that works here tested this theory just recently. His car was making 440rwhp through a full exhaust(long tubes, hooker catback). Disconnecting the exhaust at the y produced only around 10 or 12 more rwhp. Can you list details b/w the engine dyno and chassis dyno. Basically list everything that is different b/w the two runs. You should really only lose about 15-20% at the most.

fb305svs

the engine dyno had the accessories on it. alt and waterpump, and power steering. the ac compressor was on too, but the clutch wasnt engauged, besides that pull just spins free as day anyways.

I am pretty sure it has a lot to do with the cam, as to whether the exhuast in my case is hurtng it or not.. a 110lsa cam hates a restrictive exhuast, where as a 114 doesnt care as much.

that person who put 440rwhp down, did so with a power adder or something bigger than a 350, or a newer style motor...

literally the only diference between the dyno and now is the exhuast and the driveline... everything is the same, we dynoed it with my headers, my carb etc.

15-20% is where it should be, which puts me out over 50hp...

TRAXION

The right exhaust is about picking one that matches your setup as well as picking one that is free flowing. If you are going to run a high power 3" setup then you first have to pick the right muffler - no, not a flowmaster or spintech or whatever. You need a straight-through muffler. I ran hooker LT's, Mufflex 3" y-pipe, 3" intermediate pipe, into a hand picked Dynomax UltraFlo straight through muffler. It wasn't that loud because it wasn't a bullet - but it was still straight through. I ran 117mph in the 1/4 (11.6's). Don't tell me a 3" can't flow. Setup a good 3" exhaust. For pics, sound, video, and part numbers read my sticky long tube installation post.

Tim

Matt87GTA

Well Tim, I'm not really disagreeing with you here, but I just don't think a single 3" pipe will allow higher powered engines to reach their full potential. I'm not going to say for sure that yours was holding you back, but then again, did you ever try open header or anything larger? If it made the numbers is not the question.... If those numbers could be higher is.

IMO, and like you are saying, there is no such thing as "good" back pressure (resistence) so no matter the engine you should be looking for the highest flowing components you can get. Now "tuning" the exhaust to aid in the evacuation of spent exhaust gasses from the cylinders is a whole 'nother story..... But the muffler is not the place to tune your exhaust. It is also pretty easy to understand that smaller and lower power level setups will see less of a problem with lesser exhaust. I would expect the relationship to exponential in nature as the setup becomes larger and/or makes more and more power.

Which leads to the muffler type issue where I am in total agreement that the crossflow mufflers will never allow even mild 350s to breath like they should. A straight through muffler is the ticket and usually is even quieter than dual outlet crossflow chambered mufflers.....

As for me, I like my Flowmaster's sound and I don't think it is holding me back just yet weighing in at 4"s and all.... Then again, I have not ran mine open headered on the dyno (haven't even finished tuning it really!) or back to back at the drag strip to prove one way or another either.... There may even be tuning issues to look at when removing large amounts of resistence in the exhaust to get an accurate comparison.....

supermaxxbasher

Would it be possible to install dual cut outs in the y pipe one after each header,then y it into a single 3" pipe?

fb305svs

not with out reworking the y-pipe, reworking the cross member and such to gain ground clearence.. the outlets need to be pointed down, which hurts ground clearence more than it already is lol

supermaxxbasher

oh ok But are you talking about the y pipe for long tube headers cause I am talking about a y pipe for shorties?

fb305svs

longtubes - shorties, you could just do a single 3" cutout... i'm runnin g a dual 3" y into a 4" combo...