952GTR

I have the Vitesse stage 3 full kit on my 86 951. That has a MAF, 83# injectors(which should be too big dont you think) but I think this setup worked before I bought the car. It will Stumble at WOT or PT in every gear @ 3800 rpm. The Air/Fuel ratio goes full lean when it stumbles. Otherwise, car runs well.

Could it be DME?

Fuel pump not meeting demand?

Have the bigger injectors affected the DME electronics?

Any ideas are welcome and thanks for the help ahead of time.

fast951

If you are running the V-Flex or V-MAF+ software, you are able to set overboost limit and rev limit yourself. This is done via the PiggyBack.

Check your PB. Depending on which you have, look at "Setpoints" or "Switch" screens.

The overboost or rev limit acts as if you hit the rev limiter (full power kill).

If you are experiencing a hesitation around 3600rpm, but not a full power cut, just a blip in power. Then, check your map sensor. When the software detects a MAP fault, it warns the driver by generating a hesitation/blip at 3600 then at 4600 RPM. This remains in effect till the fault is fixed.

If you are using the PB as a boost controller. It relies on the MAP sensor. So a faulty sensor will yield boost control malfuction.

I would check for the above conditions first. If not the cause, report back, maybe something mechanical.

fejjj

^^^good customer service right there^^^

952GTR

Thank you!!! Illl put the disc on my laptop and hook up to the USB. Will it be self-explanatory? The previous owner from Dallas said it was defined, I wonder if that's what someone did.

952GTR

Said it was detuned!

952GTR

I'm not familiar with your setup so I'm not even sure if I have the V-flex or the V-max. I have a disc that says Peter Gerets Vitesse R vrt8.v3. The piggy back is red.

fast951

Hopefully the previous owner included the list of images on your chipboard. It will describe in details what you have.

Since you have the CD, I would read the documents. If you find a MAP sensor installation document, more than likely you have the V-Flex or V-MAF+ software.

I would start by reading the MAP installation document, as well as the PB user manual.

Follow the PB installation procedure.

Find the MAP sensor and trace the wires back to the DME.
In the PB you can monitor the MAP signal to make sure it's functioning.

While in the PB examine the "setpoints" to familiarize yourself with the user defined overboost, rev-limit or engine temp limit that may be set.

952GTR

Update!!!! FIXED!!!!!

Turns out the MAP sensor was bad causing the stumble

Also, The Vitesse boost regulator was bad. As soon as I bypassed it, i had 20 psi.

A HUGE thanks goes out to John fast951, while on vacation might I ad for his super customer service! Anybody looking to go with more power, full kits etc, PPLLease consider any Vitesse setup as he has been superb with helpful hints.

333pg333

How come your forum name is 952GTR? Just curious.

fast951

Glad you are making progress, and happy I wad able to hrlp.

The stumble was caused by a fulty MAP sensor. When I get back I can walk you through a test procedure.

I doubt the boost solenoid is bad. Boost control is done via the PiggyBack. It operates in closed loop and relies on the MAP signal. A faulty MAP causes the PB (when programmed properly) to reduce boost, which you were experiencing.