viceprp

I tried doing several searchs on the Test Pipe and found none in Audiworld.

I am currently building my way to the GIAC K04 Turbo Upgrade and I'm doing all the smaller upgrades now so when the time comes, I can just slap the turbo on and get it tuned (in a nutshell). I have a Higher milage car so I'm taking the proper precausions.

I was discussing with several individuals about the Test pipe vs. High Flow Cat. I currently have a 91 oct APR ECU and was told with any upgraded ECU it will overboost with the test pipe. Also CEL problems will occur with the TP (of course). Anyone want to give me some insight? Anyone have the TP and run into any problems besides the CEL (which can be modified)?

Also, I was talkin to Austin from GIAC about intake upgrade and this is what he had to say:
"Additionally, from my years in the B5 (I have had 2 2000 A4s and a B5 S4), there are no real gains to be had from an intake upgrade as the ram air system on the B5 is very efficient"

With a K04 upgrade, I would think everything will be accounted for. If i kept the kkk turbo, then maybe it wouldnt show as much, far as gains go. I'm hoping to get all the smaller upgrades done before this coming fall and would like some insight besides these. I see plenty of your sigs and notice some of the upgrades you have done, im taking in account of those as well.

Thank you for your patience

viceprp

Also, the gain differences between the Test Pipe vs HFC were very close but the cost of the two is the big difference. If you had the chance to do it over again, Which would you prefer? I have a mechanic that would let things "slide" so the visual inspection wouldnt be a problem.

PiMPMAN101

I have not heard of overboost from a testpipe. I made my own cold air intake for around ~$30, I think it's worth it. Really opens up the turbo's spooling sound and DV sound. If I had to do it again, I would have got a HFC. It would save all the trouble when inspection time comes around.

RallyVermont

I have been running a TP for years. I'm about to swap to a HFC. You are able to run them with non foulers on the rear O2 sensor to get rid of the check engine light. I figured with my turbo out it was time to swap to a HFC to clean things up a bit for Miss Mother nature.

I like the TP.. it hurts low end TQ but gives you some good HP gains up top.. Though the losses and gains are not very large or noticeable.

Comes down to:

1. price

2. environmental benefits

Either a TP or a HFC will give you benefits over the stock CAT with an upgraded KO4 system. It's really just a matter of patience dealing with the CEL issue of the TP to keep costs down over a good 2.5+inch HFC.

viceprp

Thanks. I'm gonna go with 034 3" HFC and call it a day. Cheers

Nitrew

Why consider a HFC when a 3" TP can be had for less than $200.oo? Two non-foulers + one testpipe = no CEL and no restriction. Unless your visual inspection is very involved why even worry about a TP... they are old news by now, anyone throwing a CEL on a TP is a below amateur tuner at best.

20 minutes and a search function can quell this storm. Even NASIOC has a great (and relevent) DIY.

Allroady DungBeetle

With a K04 a good HFC will flow enough that a TP would be VERY minimal if any "real" gains. Intake is not needed at all. Again, no gains to be had in real world driving. Use a CAT, they are a good thing for the environment and again - no real gains past a HFC with a K04 as you're just not pushing that much through it.

The correct tune set up for the correct turbo & systems you will not "overboost".

You can gain more efficiency than a TP would ever give by installing a decent charge air cooler (intercooler/aftercooler/mist system etc)

myers1.8TQ

2nd on the HFC. My LaBree HFC is a great piece and havent had any problems with it.

600whpA4

If you do find that you end up with a over boost issue with the TP you can always add a MBC parallel to the N75 to get rid of the boost spike. Over boosting is really only an issue on a DBW car since it can cause the ecu to shot the throttle if the boost spikes too high.

This really shouldn't be an issue since the TP will decrease the back pressure at the back of the exhaust housing and this means more exhaust will flow thru the path with the least resistance and this tends to be thru the WG. The TP will allow the turbo to spin faster and this means more air flow out of the compressor.