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Discussion Starter #1
Just curious if any of the single turbo guys have a 4" downpipe. If so what difference did it make?

I am assuming that this would be coupled with a 4" exhaust as well for max flow.

Obviously the 3" DP can make big numbers... but I'm just curious if it would have ANY effect.

Thanks,
 

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More torque than you
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With 3.5" exhaust a 4" downpipe won't move more air than a 3.5" dp would. A chain is as strong as it's weakest link.
Also don't forget that the exhaust housing on your turbo is also probably 3.5".
 

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AutoBanh Motorsports
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Unless you are not using the adapter part that bolt up to the DP from your Ti
you still have a 3.5 " at this adapter.
Tommy
 
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Lonestar Dawg said:


It's funny you said that because when I bought my car a year ago I thought any turbo upgrades to the Supra were overkill!
I agree... =)

There has been a couple of guys trying 4" piping with NO improvements what-so-ever in hp.

take care,
nils
 
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Lonestar Dawg said:
Nils, Thanks for the info. Do you know which turbos were in place on the cars that tried the 4" DP? I wonder what effect it had to the powerband across the board and on EGT's.
Richard,
Not really sure to be honest with you.. I remeber reading on the mkiv.com list a while back. I'm pretty sure they were APU Supra's..... but dont hold me to it =)

take care,
nils
 

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Just remember guys
Air move from intake - the head - the header - the exhaust........
Overkill mean that one of this parts are limited your flow, so have a 4" down pipe would not help.
Even though it down not help, it may effect your torque.
Just my opinions

Tommy
T-78
 
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So what DP is 3.5". Sorry im new to the forum, I actually don't even have a Surpa yet I have a 11 Sec VR6 Turbo Jetta. Selling it moving on to the get my dream car the Supra TT. Any help you guys can give me is apreciated.

Phil
 

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4" Downpipe

I currently run a custom 4" downpipe with my T88-34D turbo. BIG difference from the downpipe the GReddy single turbo kit brings.

Now I am looking for a better 4" downpipe with better fit and finish than the one we made ourselves. Any ideas?
 

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Discussion Starter #16
Re: 4" Downpipe

t88Hpower said:
I currently run a custom 4" downpipe with my T88-34D turbo. BIG difference from the downpipe the GReddy single turbo kit brings.

Now I am looking for a better 4" downpipe with better fit and finish than the one we made ourselves. Any ideas?
Wow... finally someone who uses a 4" DP. Do you have any before and after numbers to share with us? How did it effect torque, HP, spool, etc?

Thanks,
Jim
 

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Re: Re: 4" Downpipe

Jim Swantko said:


Wow... finally someone who uses a 4" DP. Do you have any before and after numbers to share with us? How did it effect torque, HP, spool, etc?

Thanks,
Jim

Sorry, no B&A dyno numbers, but a 3.5" downpipe is just too small on a T88-34D turbo. The 4" cut down on lag big time and you can FEEL the difference. I did 741rwhp with the T78 and GReddy downpipe, and I figure I must have been around 800rwhp with the T88-34D and 4"downpipe. I plan to do at least 850 with the T88H I just got, and that NEEDS a 4" downpipe, as the turbo's exhaust is just about 4"

Ernesto
 

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Ernesto, you need to put pontoons on that car. You're gonna go flying off the end of the island right into the ocean!
You said the car put down 741 rwhp with a T78. Did you mean to say T88? If that was with the T78, what type of setup were you running at the time? (NOS, cams, intake, TB, head mods)

Take care
 

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Lonestar Dawg said:
Ernesto, you need to put pontoons on that car. You're gonna go flying off the end of the island right into the ocean!
You said the car put down 741 rwhp with a T78. Did you mean to say T88? If that was with the T78, what type of setup were you running at the time? (NOS, cams, intake, TB, head mods)

Take care
At that time, I had the T78 kit @ 30psi, front mount i/c, VPC, GCC, JE Pistons, Crower Rods, OS Clutch, HKS 272 cams, no cats, Super Dragger, 720cc injectors, HKS fuel rail, twin in-tank pumps, race gasolene, extrude hone head and intake, bored out throttle body, and other stuff I probably cant remember.

That was four years ago. The cars is totally different now. T88H turbo, GReddy four row i/c, Haltech fuel comptuer, Electromotive Ignition Computer, 2nd generation JE Pistons, Crower Rods, HKS3-disc clutch, HKS cams, 4" downpipe, 1,100cc injectors, Weldon pumps, Mustang BBK throttle body, etc etc. Veilside intake with 100mm throttle body on the way, head work next(port, valves, and high cams) I'll keep you posted.

Ernesto
 

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Thanks for all the info on your 'old' setup. Thats very impressive for the T78. I expected to see NOS in the list as well. The extrude hone work really seems do wonders with the airflow. I just finished cleaning up my intake and throttle body this weekend. (The throttle body work was mostly cosmetic though.)
 
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