Power Loss in High RPMs
 

Hey everyone, im having an issue i cant seem to wrap my head around and ive been searching forums with no luck so i need some help. I had recently purchased a 1990 TT and fell in love, my dream car. Anyways there have been modifications done (ecu, exhaust, jdm motor swap, ect.). The jets intalled have me running 16psi of boost on what i believe are stock turbos, witch is high in my opinion and possibly the problem. I have noticed that when im driving hard, my power band seems to level out or even slightly decrease at 4500 RPM on up. It takes about 15 seconds to go from 90mph to 120, and im crawling past that to gain more speed. I dont know if the car was like this when i had bought it because i was head over heals the first month, but i do notice im still loosing power as time goes on. I have checked the TPS, and boost peaks at around 3800 RPM without hesitation. No detonation, engine sounds fine. Every once and a while after boosting it stalls out until im almost to a stop and the idle picks up. Its not a flat out stall, the engine floats at 100-200 rpm before dying, if thats even related. Any input would be great and help me from being a random parts changer.

My advice is

" If it has a Turbo, It Needs a Wideband.."

That is the Best Single Diagnostic tool a Car can Have ( IMHO )

http://www.innovatemotorsports.com/products/MTXL.php

Cap

Sorry, Im new to the wideband kit, so excuse the obvious question.

Do these systems run stand alone or with the ecu, because the info would be hard to use unless i can tune my ecu, or if i have a fuel regulator of some sort that works side by side with the ecu. Is it just a monitor, or are there units that regulate fuel?
Im just shooting in the dark, I have no experience with these units and its probably easier than i think. But i would like some info before i run out and get downpipes (witch is a necessity, but was waiting for upgraded turbos). Thanks for the info.

A Wideband is just a Gauge.. Like a Temp or Volt or Oil Pressure gauge.. what you do with the Information you get from it is up to you.

The 'Fuel Mixture' gauge will let you know if something is wrong. As the Mixture should have been set up to run 14.7:1 ( 14.7 Lbs of air to 1 Lbs of Fuel ).. that is the 'Normal Good for Smog' set up that will not load up the Cats with soot..

Running around town, the Mixture will 'Dance' above and below 14.7 ( The magic Number ) and the Cats will be happy and all is well..

When you 'Push your Foot into It', the 14.7 Mixture is Perfect for Smog, but KILLER for engine Life, as this is the Mixture that will make the Most heat.. this is not a Problem when the engine is Lightly Loaded, but soon after the engine really starts working for a Living, you had better get the Mixture down to 13.5:1 ( 13.5 air, 1 Fuel ).. this is the 'best Power' mixture that will not make as much heat, and more power doing it..

IF the Mixture stays at 13.5:1 all should be good, but 'Cooling Issues' in all Motors will start to creep in, and as the HP/Liter starts to rise, the Pistons will start to get a little Soft, and 'Various Areas' in the Piston Top will start to lite off the Fuel before it gets a Spark.. then things go down hill FAST.. ( fractions of a Second can kill an Engine )..

So USUALLY Turbo engines will run 12.9 fulley loaded..

Some Shitty tunes that are hiding a Knocking Condition can run 11.5 to keep things cool, and waste fuel..

USUALLY if you are below 12:1 on a WOT Turbo tune, you are doing something wrong..

Back to the Gauge.. If you are running down the road, and Ease into the Throttle, and the Mixture RISES ( > 15 ) then you have an Issue that needs to be adressed NOW.. if you 'Flog' the car to get it going you run the Risk of Melting things..

If the Misture gets out past 17:1, it just will not have enough power to make enough heat to melt things and runs like KRAP. BUT, you could have Knocking that will still break things..

So a Wideband Gauge is a Tool to see what is up.. It's not possable just to 'Plug' the Wideband into an ECU and have things take care of themselves.. as too much is happning.. it must be 'Tuned', then watch the Tune for Problems..

[ Class Dismissed ]

Cap

Thanks for that Cap, definitely useful info here.

Wow! Fantastic info, greatly appreciated! I have yet to find it explained in that much detail and clarity. Ill be sure to jump on a good wideband kit and put that knowledge to some use.