I'm new to this sweet, sweet car, so bear with me on the lack of specific turbo knowledge. 2002 A4 Avant 1.8t 5-speed. Big Thermal R&D pipes on there and Podi boost gauge. The current setup drones like crazy at higher speeds and minimal gas input. But, it's crazy fast. The gauge peaks to 25 psi and maintains 20. I'm just going to have to suck it up and take a little less HP for the sake of sanity and passenger comfort.

So, I've got a muffler guy who is going to chop out the resonators at the Y junction and put in turbo pack mufflers. These have smaller passages and will cause some restriction, but will hopefully stop the droning. The question is, will the turbo automatically adjust to the slight increase in exhaust back pressure and spin a little slower? Is the turbo pressure based on exhaust and computer input? Do I need to pay attention to valve adjustment (the N75?)?

I'd like to think I can still get a good amount of boost over stock, but I certainly don't want a blown turbo or burnt valves. Unknown at this point if this has been chipped, but I'm guessing yes by the performance. Thinking that I'm pushing 250-26o0HP range right now. But 32 MPG on the highway!!!

Thanks,
Truk

 

Uhh, stock boost is like 8 psi. Stage 1 or 1+ will get you what you're seeing so yes you are at least chipped and likely have bigger injectors. If that's the case, you're probably around 235hp at the crank. Did you actually look to confirm the turbo is the stock KO3? FYI, as long as you stay out of boost, you can have a huge turbo on it and still get high MPG highway.

You don't have to do anything when altering the exhaust. Higher backpressure affects how soon the turbo spools up so you might see it come on a bit sooner.

 

The stock turbo question is a good one. Not sure if this is K03 or K04 (just learned what these are). How does one find out which it has? And the chip?

Thanks

 

To find what turbo you have, look under the hood. Bring up a couple of pictures of a KO3 or KO4 and even a GTRS to get a feel for what they look like. Then take a look in your engine bay, left side of block along exhaust. The turbo is right there.

I'm not aware of a way to figure out what chip you have other than maybe perhaps calling the software people and asking if they have your VIN on file or something. I have no idea if that will work.

 

Theres no way thats a stock turbo. definatly post some pics.

https://www.audiforums.com/forum/sho...haust+manifold

This should help the diagnosis.

 

You could peak 23psi on a stock turbo. You won't hold it very long, but you can do it. The gauge could be reading high, too. Telling the difference between K03 and K04 isn't easy if you don't know what to look for. The dfifference between those two is not outer size, really. You have to be able to see the imprint on the side to know.
I get better mileage with a GT28Rs than I did with stock K03. Simply because you have to clobber boost a lot in order to really use up gas. On the highway you wouldn't be doing that much unless you are a speed-idiot. But since all of the supporting mods required to run a bigger turbo are needed, they in turn let the car breathe better.
Don't equate higher boost numbers with more HP. It's volume of air that is every bit as important. Just because a K03/K04 CAN boost that high, doesn't mean it should. You need a bigger turbo to hold that kind of boost to redline. While you may spike to low 20's psi, you sure as hell aren't holding it very long.
And in talking HP numbers, you are missing the most importaqnt thing.... how much of that gets to the wheels? It for sure is not 250hp. Not even close.Thermal R&D are some of the louder exhausts out there. I'm guessing you have the "Race" version. The "Street" version is a little more quiet, but both drone and there isn't much you're gonna do about it. you can cut and addresonators all day, that exhaust still drones.

 

Appreciate the info. Perhaps I can track down the last owner and acquire a list of mods. Otherwise, the exhaust gets chopped this week for inline mufflers. I'll post something if it's worth doing.

 

What is the cheapest way to get more HP. I just picked up a 02 A4 5speed with only
20K on it.

 

Search button is your friend.

 

For anyone interested, had the front resonators chopped out and mini turbo mufflers put in their place. Reduction in power is minimal as far as I can tell, and the system is much quieter during normal operation. Still some droning when going uphill in 5th gear at 70mph, but think I can live with that. System still sounds great overall. Total cost $220.