My setup is a Stage 1 +++. Like many others, I see my boost go to a high point of around 23psi, then drop to 18 psi by redline. This does not seem to be due to the physical limits of the turbo, as I have been made aware of another similarly equipped 16g car with AMS AEM and IC upgrade that can hold ~21psi to redline.

What is the exact cause of the taper, and what can be done to attenuate it?

 

The maps are tunned that way since VISHNU tunning philoshpy is not to just to turn up boost to make more power but to have smooth nice power curve. The only thing that matters is that power curve keeps going up with tunning of the fuel and timing. If you look on http://dyno4mance.com the cars make peak power over 6000 RPMS when the boost is lower.

A comparison to AEM which is standalone is different than EXEDE which uses the stock ECU that is already very smart and intercepts and adjust the signals. From What I have learned the VISHNU tunning with EXEDE factors in MAF sensor like stock ECU does but AEM doesn't. The EXEDE offers great drivabilty since it still uses the quality ECU.

Also it is illegal to have standalone while piggy back is legal. In order to pass smog in SOCAL you need to hook up to the ECU. I passed my Smog test in SOCAL

 

This isn't telling me anything, and I have the Xede-Flash, Xede, cams, gears, full exhaust, O2 housing, lower IC piping, 10.5t turbo, etc.

 

I think it has to do with the stock tapering of the ECU.

 

that told you everything


You have the same peak power as other cars that run 22 psi to redline.....basically

Your powerband is extra smooth thanks to this and there is no reason to push your trubo any higher at those rpm levels

Vishnu is taking care of your car basically, unlike many other shops and tuners

 

I'm not doubting anyone's ability to tune at all. Shiv did a great job with my car. I am however, asking what governs the boost taper. I am inclined to believe it is controlled by the ECU.

Now, as for telling me that the power difference between 18psi and 22psi is negligible at that rpm, I find that difficult to believe. This being said, why not hold the boost to redline?

 

It has been tunned to taper.

The boost can be adjusted in the Exede if you wanted to do it.

 

What if you're already running 100% on all the boost tables ? stock turbo

 

with the addition of a piggy back with so many mods... will a person be able to pass smog anyway in CA?

 

If I can remove the taper via the Xede, I would be interested in doing so and dyno testing the difference between the present 18psi taper and holding the boost as best as possible to 21-22psi. Any idea of where to address this in the Xede programming?

I am interested in knowing the rationale from Vishnu in programming the taper as is.

 

I have 100% values in the boost tables in the XEDE and the most boost I can get at red line is 19psi.

 

Find yourself a Big 16 G compressor chart

 

Where is the boost measurement taken, at the intake manifold?

 

Found this site:

http://www.stealth316.com/2-3s-compflowmaps.htm

It will take me a bit to get through it. Care to expedite things a bit with a brief preface to where I should pay special attention?

 

Muahahaha! Ted, you sound just like me. At this point I have learned to listen to no one anymore. It has ended up frustrating me, IE tuners calling other tuners "idiots" or worse. You must learn things on your own with a little guidence. I know this didn't help, but I understand your position.

-chris