Backpressure

[Dr.Mario]

Someone is arguing with me about how some cars need backpressure in the exhaust. Some one asked if they should get true duals for thier v6 and i said go for it...but this other guy said no because there wouldn't be enough backpressure. Now i'm under the impression that with true duals the guy would see a gain across the whole curve but the other guy says it will kill his low end. So is there any truth to that :confused:

[TransAmDriver]

It will hurt the low end a litte, but make up for it with the pick up in high end.

[Wolfgang]

Originally posted by KinKornKarn
Someone is arguing with me about how some cars need backpressure in the exhaust. Some one asked if they should get true duals for thier v6 and i said go for it...but this other guy said no because there wouldn't be enough backpressure. Now i'm under the impression that with true duals the guy would see a gain across the whole curve but the other guy says it will kill his low end. So is there any truth to that :confused: Dynamometer's will prove over and over that true duals do not take away low end torque. It just feels that way because of the fact that there is so much more top end torque. The increases are much more noticable the higher up the RPM range you climb. The low end will still gain some, believe it or not. :yup:

[PC PaiN]

Back pressure = low end torque usually

true duals give gains under the curve where it matters. They don't give much if any peak gains. But I'll take 15-17RWHP under the curve over 2RWHP peak any day of the week

[Dr.Mario]

Now there are two conflicting posts :rotfl: I agree with shadow messiah though...i think there will be a gain throughout the whole curve

[Dolemite]

When I pop off my cutout, my lowend suffers....by I make up on the top end.

[Dr.Mario]

Originally posted by BlackWS602
Back pressure = low end torque usually

true duals give gains under the curve where it matters. They don't give much if any peak gains. But I'll take 15-17RWHP under the curve over 2RWHP peak any day of the week
This is exactly what i think...but the otehr guy seems to think it would hurt more then help

[Dr.Mario]

Originally posted by Dolemite
When I pop off my cutout, my lowend suffers....by I make up on the top end.
Thats wierd cause when i have my cutout open i notice a gain everywhere...i confirmed this with lower 0-60's consistently on my g-tech :confused:

[PC PaiN]

Originally posted by KinKornKarn
This is exactly what i think...but the otehr guy seems to think it would hurt more then help

As far as V6's go, :shrug: The kid could always use a H pipe for some added backpressure in the system

[Dipstick]

I put headers and a 3" cat-back system on my `94 Dodge Ram and the power band(where it kicks in like a 2-stroke)moved from 1500 to 3000.

[Dr.Mario]

Originally posted by BlackWS602
As far as V6's go, :shrug: The kid could always use a H pipe for some added backpressure in the system
but it would still be better over the stock exhaust in my opinion

[98Firebird]

i put a full 3" system on my v6 (minus headers which ill have next month) and theres one jackass i know in a little vw golf with a 2.0l who shit talked me saying i just made my car slower... anyway, my bottome end sorta seems to suffer, but once it gets to about 3-4k rpms, the difference there more than makes up for it. bottom line is, the car IS faster

[PC PaiN]

Originally posted by KinKornKarn
but it would still be better over the stock exhaust in my opinion

no doubt

[Dolemite]

Originally posted by KinKornKarn
Thats wierd cause when i have my cutout open i notice a gain everywhere...i confirmed this with lower 0-60's consistently on my g-tech :confused:

well, let me reinerate that: the car FEELS like it loses low end power. I know for a fact that I make up for it on the top end, because I trap like .3-.5 mph FASTER (according to ge-tech Pro Competition) with it uncapped.

[Dr.Mario]

Originally posted by 98Firebird
i put a full 3" system on my v6 (minus headers which ill have next month) and theres one jackass i know in a little vw golf with a 2.0l who shit talked me saying i just made my car slower... anyway, my bottome end sorta seems to suffer, but once it gets to about 3-4k rpms, the difference there more than makes up for it. bottom line is, the car IS faster
See i think that you didn't lose any bottom end...it just "feels" slower because my car felt slower in the bottom end with my cutout open...but when i tested that theory out with my g-tech it was false...the car was faster 0-60 with the cutout open. We can try it on your car too...i have the ws6 up here and my g-tech.

[98Firebird]

hell yeah, ive always wanted to dick around with g-tech. lol... anyway, the loss of backpressure just seems to decreases the sotp in the lower rpms

[QWIKLS1]

What's a Gtech cost (ballpark)? :confused:

Matt

[Dolemite]

Originally posted by Ole1830
What's a Gtech cost (ballpark)? :confused:

Matt

I've seen them on ebay for $25 (or $45 :dunno: :think: ) new.

[Dr.Mario]

Originally posted by Dolemite
I've seen them on ebay for $25 (or $45 :dunno: :think: ) new.
got mine for 25 off ebay :D :cool:

[Dipstick]

If you lose it in the low end and make it up in the high end, the 0-60 times might be the same.

[eboggs_jkvl]

Let me guess? Another tech question in B&G? Right!

:gotpics:


Should we put NWS on this? Come on guys, use the tech forums for this crap. WE are trying to build up the tech forums with threads and history for future references. Who in their right mind would look in B&G for a tech answer?

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Dayem


E:)

[Dr.Mario]

i figured more people would see it and it really isn't a tech question that relates to ls1's :confused:

[eboggs_jkvl]

Backpressure isn't tech?


If that's so, why are all of the answer coming about cars?


Car site?

[Dr.Mario]

Originally posted by eboggs_jkvl
Backpressure isn't tech?


If that's so, why are all of the answer coming about cars?


Car site?
Its tech but not about ls1's...i didn't see anywhere appropriate to put it in the tech sections...so i put it here

[eboggs_jkvl]

Oh never mind. Leave it here. Have a good evening.


Later

[94BAMF]

If the exhaust is TOO large you will lose velocity, which will cause a lose in power. Obviously the velocity is slower on the low end because the engine is moving less air, therefore you lose torque. Small exhaust or restrictive exhaust can have very good velocity on the low end, creating torque, but as rpm's climb, velocity can go up no more because the pipe is too small, creating back pressure. Ideal exhaust system has no backpressure period with good velocity.

[PC PaiN]

I think what Elmer was getting at was to post this in the V6 forum :)

[Dr.Mario]

Originally posted by BlackWS602
I think what Elmer was getting at was to post this in the V6 forum :)
ahhh...i understand now...but it wouldn't have gotten answered as fast either...i was just wanted to make sure i wasn't completely wrong

[PC PaiN]

Well I'm gonna go ahead and move this to V6 so it will be there for other V6'ers reference :)

[ChillPhatCat]

Originally posted by 94BAMF
If the exhaust is TOO large you will lose velocity, which will cause a lose in power. Obviously the velocity is slower on the low end because the engine is moving less air, therefore you lose torque. Small exhaust or restrictive exhaust can have very good velocity on the low end, creating torque, but as rpm's climb, velocity can go up no more because the pipe is too small, creating back pressure. Ideal exhaust system has no backpressure period with good velocity.

Yes... the thing is that our headers are designed by default to provide the best velocity with as little back pressure as possible... most headers should be pretty close to ideal in their open state... so anything after the headers is just a restriction.

From what I've heard from the exhaust experts is that the only loss in power is percieved when the exhaust is opened up... it's just that the power band smoothes out at the same time it gets you the top end power... so it just feels like you lose low end because there are less power spikes...

[Dipstick]

Originally posted by ChillPhatCat
Yes... the thing is that our headers are designed by default to provide the best velocity with as little back pressure as possible... most headers should be pretty close to ideal in their open state... so anything after the headers is just a restriction.

From what I've heard from the exhaust experts is that the only loss in power is percieved when the exhaust is opened up... it's just that the power band smoothes out at the same time it gets you the top end power... so it just feels like you lose low end because there are less power spikes...

I hope the second paragraph is from the poster and not the source of the first paragarph. If it was a complete quote, wouldn't you think that the builder of headers would be an expert?

Some of this appears to be a cut-n-paste from a couple years ago.

Before I put the headers on my `94 Ram 5.9L, I could get wheel spin around 1500 rpm. After the headers, I couldn't. SOTP results indicated that the power band(spike)went up to 3000. Over all power probably increased in the high end, but I did lose low-end SOTP torque.

[ChillPhatCat]

Your post is nonsensical... But if you're wondering I do not cut and paste from anybody... And "our headers" was referring specifically to those that are on the market for the L32/L36 seeing as we're in the V6 forum.

What I said didn't quite come out as I meant it to, but exhaust shouldn't matter after the headers, in other words if the headers are designed correctly, whatever is behind them shouldn't matter... so you should not lose low end torque... This requires also that the purchaser of said headers chooses a set that have the correct size collectors for their engine build.

[hrspwr00v6]

i have true duals. didn't hurt my low end. actually helped it a lil, it seems to launch harder. top end is awesome.

and sweet sound too boot!

[slow6inslo]

got any sound clips??

[hrspwr00v6]

there is one on the cv6 board. i don't know the url off hand, but do a search there for 'doin' it' under exhaust forum.

[ChillPhatCat]

I finally got my 3" exhaust on today... sounds awesome and it feels soo smooth. As soon as I get the Y-pipe remounted it's gonna be awesome.

It really picks up around 60 MPH now where before when it had 2'5" coming out of the cat, power was a little delayed...

I drove it around with only the Y-pipe for a couple days and it didn't really seem any different than with the 3" on, the only noticeable difference between no exhaust and the full 3" flowmaster was that the sound doesn't shake the entire inside of the car now.