Limaxray

I am in dire need of some advice. I have a '99 Non-DBW 1.8t A4, and a couple months ago the K03's wastegate decided to disintegrate. Instead of buying a new K03 or a turbo kit, I decided it would be fun to torture myself and fabricate my own turbo kit and fueling solution. I bought a tubular exhaust manifold, external wastegate, and a T3/T04E hybrid turbo and fabricated a downpipe and all the other supporting hardware. For fuel I used a set of 50lb/hr fuel injectors driven by MegaSqirt(which works surprisingly well in addition to being completely open source). I have it street tuned using a WB to about 15-16:1 at idle and cruse and go up to 12:1 under full load. It drives and idles well. I'm still working out a way to control ignition, so for now that's still in the hands of the Audi ECU.

Now here's the problem. When I get on it, I'll start seeing boost a little above 2k, and it gradually builds up to a whopping 5 PSI by 6k. I don't understand why this is.

Here are a few of my thoughts why:

-I have a MTM chip. It advances the hell out of the timing, to the point where the car was still pretty quick when the K03 crapped out. I know for a bigger turbo, you want less advance to raise EGT's quicker thus reducing turbo lag. The car runs at about ~25-30 degrees of advance at cruse and light load, and lets up as revs and load increases. Could this be too advanced?

-Maybe my turbo is too big. It has a .50A/R cold side and .70A/R hot side. I was under the impression this would work well as this is the type of turbo a lot of the small engine Honda guys use.

-Maybe my turbo is shot. I bought it brand new, not refurbished or anything, but there is still the possibility it has a faulty bearing or something.

-Maybe there's something wrong with my wastegate. Perhaps it‼sup>TM</sup>s opening to early or leaking exhaust around the turbo. I tried cranking my boost controller all the way up, then disconnected the pressure signal all together, then connected it to the atmosphere port on the wastegate, none of which made any difference.

-I have a small exhaust leak after the downpipe (at the stock Audi exhaust clamp that I had cut off it was so badly rusted on). Could this leak be causing some sort of problem?

-Are my AFR off? What trend in AFR works best for building boost in these engines?

Any thoughts or advice would be much appreciated. I really am stuck now so it would be a big help if someone could give me anymore ideas or share their experiences. Thank you in advance.

WJM

could just be the wastegate not being set tight enough

Limaxray

I think I found the problem. Appearntly, this little metal ring that came with my wastegate that Tial failed to even mention in its instructions is actually a valve seat. Wow I feel like an idiot. So I guess I'll go home tonight and pull off my wastegate and see if this works.

Audi2ptzero

Yes you need to put that in. They dont install it so you know you can replace it.

Audi2ptzero

They do this so that the fuel is burning on the way thru the turbo and spooling it up quicker because the speed of the flow of exhaust gas is increased.

Less timing will produce less tq and more tq will increase your spool up. It is pretty much a give and take.

On my setup I see a max of 42 degs of timing off boost and 22degs on boost, but thats for a 8:1 cr on 91 octane running 16psi of boost.

Limaxray

Yeah wow so I installed the valve seat and it works much better now. I really feel like a moron. It spools up very quickly and pulls much harder then the K03 ever did, even though I so far only have it tuned to 10 PSI and 5000 RPM. I was going to get a GT28RS or GT2871R once I got everything working, but I'm pretty happy with the performance of this turbo so far, so I'll probably stick with this one.

Limaxray

...but I guess you need it to make it drivable off boost.

By retarding the ignition, you create a less efficient burn, sending more unburned into the exhaust as you said. More advance is more efficient, and produces more torque, less advance means less torque, but makes your turbo into somewhat of a gas turbine and spools it quicker. Personally, I'd go more for the torque, but I under estimated (because forgot to install a stupid freaking valve seat) how well my turbo would spool.

Anti-lag, like that used in WRC, 'comes on' when the throttle is let up. It not only retards the hell out of the timing, it also runs it super rich, dumping even more fuel into the turbo. This keeps the turbo spooling through turns. I don't know if they still do this, and I wouldn't do it, as it isn't to great for the life of your fairly expensive turbo.

Audi2ptzero

Problem is that I tend to use 110-112 leaded octane now, so I might just turn the adv timing up a bit.


As for running the car very rich when lifting off the throttle, we can do that on the dbw cars using lemmiwinks. So much that it shoots a fire ball out the back of the exhaust. Wont do it on my car since I run a dump tube off of my ext wastegate.