[SlicktopTTZ]

Originally Posted by Nando

when i was looking this up i read something about thermal velocity, thats why they were sayongt he stock piping is actually pretty good..ill try to find the article and post it

I think that has to do with the amount of heat before/after the turbine. You want the most amount of heat before the turbine (exhaust manifold) and the least amount of heat behind the turbine (downpipe). Since energy (heat) seeks natural balance, this temperature difference aids in efficiency. This is why it is a bad idea to coat your downpipes, manifold coating is good though.

[Fern8321]

just from personal experience, if the piping is too big and you dont have the power to support it, the car will lose power. every car is different but a friend of mine has a lexus is300 with the supra twin turbo engine in it. His exhaust is three inch piping but he is losing power right now because he hasnt converted it yet to a single turbo and doenst enough hp to need 3 inches. he plans to convert very soon and thats why he went ahead with 3" all around. On the other hand i have a friend with a turbo civic and he uses 4" piping, but hes pushing 450hp to the wheels

[SlicktopTTZ]

Originally Posted by Nando

just from personal experience, if the piping is too big and you dont have the power to support it, the car will lose power. every car is different but a friend of mine has a lexus is300 with the supra twin turbo engine in it. His exhaust is three inch piping but he is losing power right now because he hasnt converted it yet to a single turbo and doenst enough hp to need 3 inches. he plans to convert very soon and thats why he went ahead with 3" all around. On the other hand i have a friend with a turbo civic and he uses 4" piping, but hes pushing 450hp to the wheels

How do you know he is losing power? What exhaust did he have before to compare to and how do you it is his exhaust and not something else that is causing the power loss? This just doesnt make sense, turbo cars do not rely on exhaust velocity to scavenge out gas!

[Fern8321]

hes losing power because he is losing back pressure, he has built cars from he ground up so i trust his judgement..its also not the first time ive heard of this happening, im no expert but at the end of the day the only way to know for sure is to try it and compare numbers.

[Eric@AMS]

Originally Posted by SlicktopTTZ

So you guys are saying with the JB3 and meth/race gas at 18-22psi (not sure what the highest race map is at boost wise) that these turbos wouldn't benefit from having unsqueezed exhaust all the way back? Oldbooster recently dyno'd with 525ftlbs at the wheels with race gas/meth/25 shot no2 and his car cut out early at 5,000rpm, he is at the point where every little bit will count. Even if it was only 15whp, what does that equal in 1/4 time where even a tenth of a second counts?

Even at that boost level the stock turbos are simply not moving enough air to benefit from larger piping like you are suggesting. have you seen the size of the N54 Turbo's? The turbine wheels is the size of a quarter...not figuratively....LITERALLY THE SIZE OF A QUARTER lol

Eric

[Vince@ V K Motorwerks]

Originally Posted by Eric@AMS

Even at that boost level the stock turbos are simply not moving enough air to benefit from larger piping like you are suggesting. have you seen the size of the N54 Turbo's? The turbine wheels is the size of a quarter...not figuratively....LITERALLY THE SIZE OF A QUARTER lol

Eric

Eric is right. There is no benifit of increasing the pipes to 3" with stock turbos they just dont flow that much air.

[1clean335i]

Originally Posted by Eric@AMS

Even at that boost level the stock turbos are simply not moving enough air to benefit from larger piping like you are suggesting. have you seen the size of the N54 Turbo's? The turbine wheels is the size of a quarter...not figuratively....LITERALLY THE SIZE OF A QUARTER lol

Eric

Exactly what I was trying to say on page 1. Hopefully with your credibility, he'll believe it now.

[SlicktopTTZ]

Originally Posted by Nando

hes losing power because he is losing back pressure, he has built cars from he ground up so i trust his judgement..its also not the first time ive heard of this happening, im no expert but at the end of the day the only way to know for sure is to try it and compare numbers.

No offense but I don't think he knows what he is talking about when it comes to turbo systems. You don't want any backpressure on a turbo system if you want to make power. When the compressor is forcing air through the engine and all the combusted gas passes through the turbine it is doing ALL of the scavenging out of the cylinder and blowing it into the exhaust pipe. If that exhaust pipe has ANY backpressure it will hinder the flow, resulting in a power loss. Exhaust velocity is important on Naturally Aspirated cars be cause they don't have a turbo to remove/force air! If you have a huge pipe on a NA car it will not squeeze the exhaust enough to keep velocity up and you will not scavange all the exhaust gas out, but go too small and the backpressure will create a horsepower loss as well.

[Eric@AMS]

Originally Posted by Nando

hes losing power because he is losing back pressure, he has built cars from he ground up so i trust his judgement..its also not the first time ive heard of this happening, im no expert but at the end of the day the only way to know for sure is to try it and compare numbers.

just so you know losing back pressure on a turbo car will NOT cause you to lose power. Back pressure causes a turbo to not spin as efficiently which can in turn hurt performance. Your friend sounds like he is applying NA engine theory to Forced induction engine theory and you can't do that.

There becomes a point where a turbo can only move so much air. When you hit that point making the exhaust larger will have no effect. You are just creating a larger area for the air to occupy but a larger volume of air is not being introduced. You can't improve on Zero back pressure if Zero back pressure exists.

Eric

[SlicktopTTZ]

Originally Posted by Eric@AMS

Even at that boost level the stock turbos are simply not moving enough air to benefit from larger piping like you are suggesting. have you seen the size of the N54 Turbo's? The turbine wheels is the size of a quarter...not figuratively....LITERALLY THE SIZE OF A QUARTER lol

Eric

Well I trust you guys at AMS, the 3" single with a 525whp (oldbooster) car goes against what the Garret turbo engineer says though. I also didn't know they were THAT small, I thought my stock 300zx turbos were small and they are like a silver dollar. Personally I felt a gain going from 2.5" downpipes and exhaust to 3" downpipes and exhaust, but like I stated earlier that was on twin GT2560s, which really aren't that big either. Eric, did you guys ever experiment with a 4" pipe at race gas/meth boost levels? To be honest I still think a single 3" would be a bottleneck on OldBooster's car, even if it was a slight one.

[Fern8321]

im saying the same thing everyone else here is saying..these cars dont need 3" piping, the turbos are too small, even vince and eric agreed. every turbo car is not the same.

[badass1g]

so if im thinking correct doesnt the cars oem exhaust have dual full 2.5 inch all the way back? if so thats a huge exhaust (5") and i can see how that would be enough if the cats were removed. is there a way to gut the stock cats? i know its a cheap way of thinking but it would be free hp.

[Fern8321]

Originally Posted by badass1g

so if im thinking correct doesnt the cars oem exhaust have dual full 2.5 inch all the way back? if so thats a huge exhaust (5") and i can see how that would be enough if the cats were removed. is there a way to gut the stock cats? i know its a cheap way of thinking but it would be free hp.

my exhaust uses the stock piping with the cats removed, and its faster than some 335's with similar mods and full exhaust. like i said before im no expert but i belive in results.

btw thanks for the clarification eric..ive been wrong before

[TMR]

If you say dual 3" will work... Do it. Id love to see how you make it fit.

[XPO186]

Originally Posted by TMR

If you say dual 3" will work... Do it. Id love to see how you make it fit.

It looks like it touches in a few places, but it's all there.

And btw, THAT IS NOT MY CAR.

[badass1g]

wow that full 3 inch exhaust is perfect. to bad the music in the vid doesnt let you hear the sounds do they sell that setup?

[midlife]

Originally Posted by 1clean335i

A full dual 3" exhaust is not needed for those tiny turbos.........

Many- like me - would want 3" exhaust for future turbo upgrade.
If dual pipes will not fit - someone should make a dual into single system !
AR already said they could easily make their current 3" dps into full 3" dps

[import36]

Originally Posted by midlife

Many- like me - would want 3" exhaust for future turbo upgrade.
If dual pipes will not fit - someone should make a dual into single system !
AR already said they could easily make their current 3" dps into full 3" dps

a la AMS?

[TMR]

my problem with the 3" was the pipe hung too low. The 2 feet from the downpipes to before the bend to the left. I guess my car is just too low. My next project is to go to a single oval 3.5" pipe.

[1clean335i]

Originally Posted by midlife

Many- like me - would want 3" exhaust for future turbo upgrade.
If dual pipes will not fit - someone should make a dual into single system !
AR already said they could easily make their current 3" dps into full 3" dps

A single 3" set-up like the AMS catback is ideal. I like how AMS merges into the single.

What a company needs to do is make a down pipe that already merges into a single 3" pipe whereas putting the merge further back in the exhaust. *hint*ams*hint*. Something similar to this-

[Former_Boosted_IS]

Originally Posted by midlife

Many- like me - would want 3" exhaust for future turbo upgrade.
If dual pipes will not fit - someone should make a dual into single system !
AR already said they could easily make their current 3" dps into full 3" dps

Why in the world would you do that other than weight savings. Remember flow is proportional to cross section area. The cross sectional area for 3" versus dual 2.5" is:

Single 3" = 7.1 sq. inches
Dual 2.5" = 4.9 sq. inches + 4.9 sq. inches = 9.8 sq. inches

The bottom line is a dual 2.5" exhaust flow the equivelant of a single 3.5" exhaust. That is a big pipe.

[marconi118]

Yes never make the mistake that 2 2.5" pipes equal to 5" pipe