Gains from a larger D.P

[mec108]

I have a very stout 4.1 with PT-72 Qtrim turbo and 3 Inch downpipe. What gains can, I expect by switching to a 3.5 inch or 4 inch downpipe ? Thanks

 

[OneLethal87GN]

A new article in GM High-Tech mentions about a 20 h.p. gain from a 3 to a 3 1/2" downpipe. I believe it was Red Armstrong's car.

 

[36IndexGN]

Actually it was his wifes car

If thats a big turbo, than yeah it would be very helpfull. I had a little old Garret T-25 and I went from 2.5 stock to 3 inch custom, it made a world of difference.

 

[87ttypeV8]

what about a stock turbo on a slightly modified car...
i currently have a THDP 3" that is pretty dented up now... about 3 big ones!!

do they sell a 3.5" or would that make really no diff. on a stock turbo since there isnt that much pressure in the exhaust?

 

[U1ARUNIT]

You won't gain anything with the stock turbo. It's desinged for larger turbo/motor combos.

 

[Two Lane]

WHAT'S THAT BANGING SOUND UNDER THE HOOD?

Fitment can be a serious challenge with a 3.5 Downpipe.

Something to consider.

HTH

 

[GNVYUS 1]

Tons of supras at over 800 whp all have 4 inchers. It has to do something for those bigger turbos like yours.

Fitting it however is a big challenge, you would need the poly mounts, and the ac delete plate from www.buickgn.com to start with.

I heard Cotton has one coming, not sure if this is accurate though.

I would get one if I had a PT 72.

 

[Big88]

Down pipes

To whom it may concern

I just changed my down pipe from a three inch atr. To a four inch that i made myself. On the advice of Joe Lubrant. I could not belive the differance. I am running a pt 88 4 bolt turbo. I went from struggling 9.8's and 9.9's 142's mph. To 9.4's at 148 the engine never sounded this good before. after two years of this struggling my problem is solved, Now i can concentrate of tuning this beast. Thanks JOE!!!!!
Tom Stevens

 

[mec108]

I have a pt 72 q- trim turbo which is medium size turbo by today's standard. My biggest problem is my A.T.R headers. I don't know of any one who makes a 3.5 or larger down pipe to fit my application? Any information wil be much appreciated THANKS guys.

 

[gnxtc2]

Hey Two Lane

When I went from a 3" THDP to his 3.5", the 3.5" went in easier than the 3".

You need the 3.5" DP when you start using a Q trim wheel. The smaller DP blocks the wheel. You could also grind it open more on the 3".

Hope this helps

Billy T.
gnxtc2@AOL.COM

 

[mec108]

Gnxtc2. What type of headers do you have on your car?

 

[Russ Merritt]

No one make one for ATR headers. Cotton can make you one. I'm gonna end up going that route. He has a new tig welder so life is good in Cotton land.

 

[mec108]

Thanks, Russ for the information. I guess thats the route, I'll have to take also.

 

[Russ Merritt]

No problem. HEY JACK! Chime in and tell us all how good you make DPs.

 

[mec108]

And, If they are stainless steel.

 

[gnxtc2]

Originally posted by mec108
Gnxtc2. What type of headers do you have on your car?

Stock headers that were cut open, cleaned up, and welded closed again, and port matched to a 1400 Fel Pro gasket

Billy T.
gnxtc2@aol.com

 

[mec108]

Big 88. Going from a 3inch D.P to a 4 inch D.P, About how much H.P did you pick up. roughly Thanks

 

[Big88]

Down Pipe HP

I would say it had to be atleast 50hp. The 3" was way to small for a pt88 turbo. the engine never ran smooth to much back pres.

 

[mec108]

Big 88 Do you have a 3 bolt or 4 bolt turbine housing for your "super size" 88 turbo.

 

[Big88]

D.P.

Mec108
Its a 4 bolt.