Power loss with 3'' exahust?

[Insearchofatsi]

I have a 92 gsx basically all stock. I tried searching for this but didnt find anything useful so if someone can paste a thread thanks. I want to get a 3 inch thermal exahust and 3 inch downpipe w/no c at or with it hollowed out. I know that with the turbo it wouldnt be a severe loss but would i be losing any power. I plan on getting all the supporting mods for a 16g as soon as i can. When i put 2.5 exahust on my old z24 i lost lots of power and I was just wondering if this would be as dramatic if at all. Thanks Sorry for the newb questions

 

[BOBS90TURBO]

I am no wiseman but I think you will not lose any power, in fact you should gain quite a bit, I did a 2 1/2' on my old all stock gst and it felt like I had raised 20 or 30 hp.
Why go 3"inch, you will get boost creep.

 

[PaulPDX]

I just went from stock to a full 3" o2 elim turbo back on my 91. No noticeable loss in power at all. You can cast aside all the bench racing arguments that has taken place here in the forums. The car drives normally at normal speeds and in heavy traffic. Once you step on it, the car lets you know the 3" system is there.

 

[DSMJim]

You will not loose power on a turbo car with a large free-flowing exhaust system. The only people who will tell you that are guys who believe cars NEED backpressure which is completly untrue. It has been proven over and over and over that backpressure is ALWAYS bad in an exhaust system ESPICALLY on a turbo car. On an NA car they lose down low typically but alwasy gain uptop (generally Honda's I'm refering to as they are typically the faster N/A cars.)

Gains of 15-20 HP have been reported with a simple turbo back exahust system. You want the largest possible exhaust system possible as the faster you can get the exhaust away from the turbo the better. Some people said they got boost creep from a 3" turbo back on a stock turbo, however I had a 3" with my T-25 and never got boost creep so I'm speaking from my own experience. I have never had boost creep issues ever on any of my turbo cars.

If your getting arguements from V8 guys who say it's stupid to do a 3" exhaust on a 4cyl turbo car, tell them it's the same a I diesel how they need a super large exahust. Not because they are diesel but because they are turbo! V8 guys are pretty dumb when it comes to turbo stuff.

 

[kpt4321]

You won't lose power. A larger exhaust will decrease the pressure after the turbo, which will do two things:

-For the same pressure differential across the turbine, you will have a lower manifold pressure, which decreases reversion.

-For the same manifold pressure as before, you will have a higher pressure differential, speeding up spool time.

 

[Insearchofatsi]

alright, thanks alot guys. Well i am gonna get a tial external wastegate would that stop the boost creep on a stock gsx with 3 inch? Nah, i gotta go 3 inch man, im going t3/t4 50 trim soon.....after i get my fmic, which is after i get my injectors, pump, and safc, which is after a couple other things. Cars make me poor

 

[PaulPDX]

This back pressure myth is almost as bad as the underhood insulator being mistaken for a fire supression blanket...

 

[92tsifwd]

Originally posted by DSMJim
You will not loose power on a turbo car with a large free-flowing exhaust system. The only people who will tell you that are guys who believe cars NEED backpressure which is completly untrue. It has been proven over and over and over that backpressure is ALWAYS bad in an exhaust system ESPICALLY on a turbo car. On an NA car they lose down low typically but alwasy gain uptop (generally Honda's I'm refering to as they are typically the faster N/A cars.)

Gains of 15-20 HP have been reported with a simple turbo back exahust system. You want the largest possible exhaust system possible as the faster you can get the exhaust away from the turbo the better. Some people said they got boost creep from a 3" turbo back on a stock turbo, however I had a 3" with my T-25 and never got boost creep so I'm speaking from my own experience. I have never had boost creep issues ever on any of my turbo cars.

If your getting arguements from V8 guys who say it's stupid to do a 3" exhaust on a 4cyl turbo car, tell them it's the same a I diesel how they need a super large exahust. Not because they are diesel but because they are turbo! V8 guys are pretty dumb when it comes to turbo stuff.

I agree, but why does he want a 2.5 inch exhaust, a 16g needs a full 3 inch exhaust to get the biggest gain and 3 inch exhausts are not much more. Pay a little more now, it will be worth it.

 

[Insearchofatsi]

Yea, when i had my cavalier I wanted meinkee to weld on 3 inch piping and the guy wiouldnt do it. I said I want more power and he said, "no youll lose power. All 4 cyclinders shouldnt be allowed to have a 3 inch exahust, you want power, go v8."Granted this was a Z24 but still he said all 4 cylinders. Recommend any good places for gettin your exahust on in PA/NJ?

 

[PaulPDX]

Originally posted by Insearchofatsi
Yea, when i had my cavalier I wanted meinkee to weld on 3 inch piping and the guy wiouldnt do it. I said I want more power and he said, "no youll lose power. All 4 cyclinders shouldnt be allowed to have a 3 inch exahust, you want power, go v8."Granted this was a Z24 but still he said all 4 cylinders. Recommend any good places for gettin your exahust on in PA/NJ?

He welds and installs generic mufflers for soccer mom's day in and day out, and NASCAR (which is 1950 technology) is probably the only known form of motorsports to him... he knows how to turn a wrench, weld, and bend pipes. But, what does he know about turboed engines?

The statement he made is completely false. When you add a turbo, it's a whole new game.

 

[anconover]

you wont loose HP on a 3" exhaust no matter the turbo. what you lost was the low end torque you may have felt before.

 

[ARTSUPRA]

Originally posted by anconover
you wont loose HP on a 3" exhaust no matter the turbo. what you lost was the low end torque you may have felt before.

Well this is one of my concerns how bad is it really? I am runing 14B so how much will a lose on low end. I am in proccess building my own intercooler piping and exhaust so just want to have a heads up

 

[14.5 drift]

hehe there is no low end on a turbo car, maybe, barely the top of the bottom end with that small of a turbo, but the midrange will be good and the top end will be great!!! No worry about it. PLus the big exhaust is gonna help you spool wich makes up for bottom end losses.

 

[PaulPDX]

It's not even noticeable. All the benchracers and self proclaimed rocket scientists have gone around so often spreading the lie that it's got people all paranoid.

The facts are all laid out like 8 posts before yours. Please read it. People post good info for a good reason.

Quicker spool up is going to erase any ill effects of low end torque loss. It's not like slapping on a 3" system to a non-turbo car. Once that compressor starts spinning you're off in a cloud of whale dung. That, is the beauty of forced induction.

 

[DSMJim]

Originally posted by 92tsifwd
I agree, but why does he want a 2.5 inch exhaust, a 16g needs a full 3 inch exhaust to get the biggest gain and 3 inch exhausts are not much more. Pay a little more now, it will be worth it.

Who said anything about a 2.5" exhaust?

 

[14.5 drift]

I dont know but the guy is asking about a 3 inch catback.

 

[ARTSUPRA]

Ok, reassured on 3" then

 

[swing lo]

Originally posted by Insearchofatsi
alright, thanks alot guys. Well i am gonna get a tial external wastegate would that stop the boost creep on a stock gsx with 3 inch? Nah, i gotta go 3 inch man, im going t3/t4 50 trim soon.....after i get my fmic, which is after i get my injectors, pump, and safc, which is after a couple other things. Cars make me poor

If you want precise boost control then you need to get an external w-gate which will prevent boost creep.

Somebody correct me if i'm wrong.

 

[PaulPDX]

Internal gate can do the job if it is the right size for the turbo.