4" downpipe?

Try contacting www.horsepowerfreaks.com
They were working on a 4" DP earlier this winter.

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".

The HKS Hiper Titanium exhaust is 4" in diameter. Combined with the 4" DP there will be a reduction in backpressure at the turbine outlet.

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

anything over 3.5" is overkill.

take care,
nils

anthracite said:

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

Click to expand...

From what I understand, the DP Chris was working on was going to bolt up to the turbine outlet flange.

nils said:

anything over 3.5" is overkill.

take care,
nils

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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!

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!

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I agree... =)

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

take care,
nils

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.

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.

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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

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

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

PHR sells a nice custom 3.5 inch DP for the single turbo kits...
www.powerhouseracing.com
Peter

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?

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?

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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

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

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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

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

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

Click to expand...

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

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.)