DownPipe ???????

[donZ]

i just replaced the stock down pipe, and gutted cat ,with a 3 inch one (not sure who makes it ) , and test pipe.
it seems like it does not pull as hard, does this sound right ????

 

[donZ]

do they make much of a differance, with a stock turbo ?

 

[azgn]

if you still have the stock elbow, probably not....the elbow is the restriction, not the pipe

 

[speedy1320]

Don, when I put my 3" on AND the 3" race-cat, it made a world of difference! Your car should show improved results.....the stock exhaust on these cars was the largest factor in holding back horse power!

Tom

 

[donZ]

what elbow, are you talking about ?

 

[blackbuick87]

The elbow is the dooflicky the DP bolts to, and it contains the puck. While you had it off to do the downpipe you should have ported it with a dremel tool.

My budget 3"DP increased spool up, thats about all. Sounds a little better

 

[UNGN]

I tested the "ultimate 3" downpipe", the Terry Houston, vs. a stock replacement 2.5" downpipe and a ported elbow, last year.

The Stock replacement/Ported elbow was only .05 slower on average in the 1/4 mile than the 3" THDP downpipe and this was running high 11's. Seat of the pants, its pretty hard to feel .05 seconds.

If your elbow isn't ported and your exhaust is stock or restrictive, there is more bang to the buck by fixing these than upgrading the downpipe.

 

[turbo buicks]

how easy is the stock elbow to port? how long does it take?

 

[UNGN]

Originally posted by turbo buicks
how easy is the stock elbow to port? how long does it take?

It's very easy, and hard to screw up. Cast Iron won't load up a stone or burr like aluminum and with a carbide burr it will cut like butter.

Open the outlet to 2.6" all the way through (OD of the donut gasket) and blend a radius on the short side. That's about all there is too it.

 

[tangofox]

I picked up 2 tenths and 2mph in the 1/4 by replacing my ported stock elbow and gutted cat by putting a 3in down pipe with dump tube on. I was running with an open dump. I did't get a chance to run with it closed because it starting raining.

 

[UNGN]

Originally posted by tangofox
I picked up 2 tenths and 2mph in the 1/4 by replacing my ported stock elbow and gutted cat by putting a 3in down pipe with dump tube on. I was running with an open dump. I did't get a chance to run with it closed because it starting raining.

I picked up 4 mph and went .4 seconds faster, switching from a ported elbow/stock down pipe to a THDP with a dump. That's because my exhaust sucked.

When testing the ported elbow/2.5" downpipe vs. the 3" THDP I kept everything else the same and the conditions were identical.

I did 5 runs each using the same boost, launch, tire pressure, everything. I averaged the 3 best runs and the ET was only .055 different. The MPH was an average of 1.5 mph faster, but that's because the THDP will allow the engine to rev slighly better and make more top end hp (above 5000 RPM) than the ported elbow.

Average ET/MPH of the entire test was 11.8 @ 114. Slower than this, I can't see an apples to apples ET difference of more than .1 seconds.