jlh28athome

What is the most appropriate exhaust size for an A4 1.8T planning on a big turbo upgrade? I don't want to have the EGT drop in the exhuast piping and slow down. I am guessing maybe a true 2.25 or 2.5 inch exhuast system. I am willing to sacrifice a small amount on the top-end to preserve low-end torque.

Next, what kit, K04, APR, PES, or Custom would be the best at generating and holding a lot of torque throughout the rpm band? I don't want to hit full boost at 5K and generate 300hp for 500rpm or something like that. I would rather have 250-275 with massive amounts of torque available for several thousand rpm's.

Any suggestions, books I should read, web-sites that are good? I would guess that given my criteria that either the K04 with very strong programming or an APR kit when available for my 2001.5 would be my best bet. I am not partial to either of these. It just seems that the Ko4 is good for low-end power to about 240hp, and the APR for ~275 with a little loss in the low end. (negative for APR is that there is no support for intercoolers which I plan to add soon.)

Pes has good tuning support, but I think that the turbo hits boost a little later that the APR kit.

Anyway, opinions, experiences, whatever would be appreciated.

Audi2ptzero

The K04 will make more tq down low and in the midrange but will peak sooner then the APR/PES kits. With the bigger kits like the APR/PES your going to have less tq but the tq/hp will be about even in power and higher in the rpms since the turbo comes on later then the K04 and at an even pace which means it can hold the boost level to redline.


If your looking for tons of tq with a good amount of hp then go with a good chipped K04 on your 2001. GIAC even has a race chip for the 2001 K04 kits for 100+ octane.

johnAWD

A 3" exhaust is good for up to 800 rwhp.

2.5" is a GREAT plenty for these tiny heads & "tiny" turbos.

FWIW.

Merkin

300hp, go 3"

Mike M.

Works fine for me with the APR kit. Everyone has a different opinion for different applications so I'll just leave the exhaust question at that.

As for my very basic opinion (and take this with a grain of salt if you wish), another thing to keep in mind when you're looking for torque is your intake air temps and timing. You may want to look at the efficiencies of certain kits when considering your upgrade path and priorities. Some may state it's all fine that you can run way advanced timing on a "race" chip, but it's pretty worthless when your timing gets retarded by half or more due to excessive intake air temps (sometimes correlated by inefficiency of a particular turbo/manifold/software at high rpm). Also, be cautious when the bandaid comes as piggyback fuel to cool the engine. I've seen dyno pulls on some kits that run overtly rich at WOT, and showed little to no improvements over chipped A4's. Nonetheless, looks like you're already looking at aftermarket intercooling, which is a good start to big turbo'ing.

As for literatures, Corky Bell's pieces are usually good readings when you embark on your project. Good luck!