i recently aquired a 2000 S4 6sd. it runs great except for at 4000 rpm the car falls almost flat on its face. one friend of mine said that this is when the engine switches over from short runners to long runners. i was thinking maybe a vacum leak or an electrical connection would be preventing this, i can hear the turbos spool and i can fell the amazing power all the way to 4000k but when i get there it just kinda feels like it runs out of power. also, are the turbos the same size on this car or is one a small fast spooling turbo and one a big slow spooling turbo. and if so maybe a bad turbo? this is my first turbo charged car. i am also big into muscle cars, i have a 1967 mustang gt with 350 hp. so im a little lost with all of this electronics. Any help would be greatly appreciated!
Thanks
Ted

 

I’m new to owning an Audi, but not new to turbo. The Turbo are the same size on this car & it sounds like you may have a boost leak somewhere in the system. Check all your hose as the stock ones are pretty weak. You should invest in a boost gauge, this way you can see how much boost is escaping. Good luck...

 

There is only one set of intake runners on this car. No long and short just one per cylinder

 

LOL, read the FAQ!

Now, is the car stock? If so, it does run out of breath up top.

However, you can also have a boost leak (TBB & DV's), throttle cut (doubt it if you are stock), you just might need a tune up.

 

how much does a "tune up" cost for the s4 and what does it entail if you dont mind me asking. i know what a tune up on old cars are but not the new ones.... and yeah it runs out ob breath at high rpms, it just seems like it hits 4k and just loses all the power. in 5th gear its hard to get past 4k its almost impossible, but once you get past it it seems to gain some power back. a buddy of mine has an A6 with the 2.7t and it justs keeps pulling hard right past 4k, this is why i think it has a problem. and i believe the car is 100% stock, one theory i had was that some one might have messed with the wastegate and tryed to get more boost out of it and the computer senses and overboost and shuts the power off, what do you think?
thanks

 

Read the FAQ on what gets replaced @ what milage. Basically, filters, fluids & plugs. Cost is variable, call around your area.

You should notice some loss up top, but it should still pull. I say you have a boost leak, & possibly a failing N75.

Now, you need to check for stored codes, & run some Vag-com logs on block 115.
http://www.ross-tech.com/
http://www.bentleypublishers.com/tech/audi/

 

what is a N75? im not up on all the part numbers. i was thinking that vacuum lines need replacing and maybe the diverter valve being that its a rubber diapfram inside could be bad. i noticed some (american) hose clamps on vacuum lines,,, thus makes me think that someone thought it had a leak before, so i will replace them tonight. i will check the hose clamps on the boost tubes, i did i quick check this morning and they seemed tight and not rotted. thus leading me to think it is the DV or vacuum lines leaking when it starts to see more boost around 4K

 

TBB & DV's are a good place to start.

The N75 is the valve the controls boost.

 

ok, will replace the dv, where is the N75 located? on the turbos or the manifold? and the TBB = throttle body b?

 

any modifications to the car?

any idea what your boost is running at?

you may be running into throttle cut. or you could have a boost leak and you are just in limp mode.