I have a 2006, 3.6 Carrera 4, manual transmission with the VF-Engineering supercharger kit. It has been installed in the car since 2013 and about 30K miles and for the last 10K or so I've been fighting a problem which has had the car back to the local dealership too many times to count.

There is some kind of issue between the Mass Airflow Sensor relating
to the supercharger and the tune programming on the ECU. If I accelerate hard thru first gear the car performance when cold the acceleration is flawless, 2nd gear 6 and 7000 rpm's the car surges and
dips in RPM and Surges but not steady as it should.
If the mass airflow sensor is disconnected and the ecu goes into closed loop then it runs perfect in each gear. We have tried replacing the MAF and the associated temp sensor on the supercharger intercooler but no cure. Also, replaced all of the sparkplugs.
The problem is much more pronounced when the car is warm and also when the air temp outside is hotter than 70 degrees which is most of the time since I live in Florida.

I have called VF multiple times and they always say to send an email which I've done multiple times and VF-engineering never puts me thru to a tech.. The Dealer has run into the same problem So anyone that can offer some assistance with this issue would be greatly appreciated as I have the car at the dealership now trying to chase down the problem again.
Thanks.

 

I have had the VF kit in my car for around 9 years, and I would not recommend running the car to those RPM's until it has warmed up, I would also suggest checking the air filter. The little thing gets pretty dirt pretty fast. I keep 2 extras in my garage and change them often and then clean the one that was in the car. I made many alterations to their kit over the years but have never had any issues with it.

 

Mr Price,
thank you for the reply, I don't normally make it a habbit of running those RPM's when cold and have only been doing it to try and diagnose. Thanks for the filter tip. How many miles do you have on the supercharger kit and what alterations have you made?

 

Have you checked all the air connections?
Are you running the recommended pulley or a smaller one? Do you have a resistor inline with the MAF sensor?
CATTMAN

 

My car was completely taken apart 24 hours after I bought it, and over the next year and a half was very slowly put back together, many of the parts were one off I designed myself, the kit needed to be modified to fit those designs. I do not think anything I had to do would be helpful to your situation unless you plan to rebuild your car as well. My 997 is one of many cars I own and is only driven under certain conditions, it is 10 years old and only has a bit over 16K miles.

 

Car run perfect when MAF disconnected, this is the clue.

Is MAF and injectors stock? MAF could be out of calibration to injector size.

 

You may need a resistor inline with the MAF to "trick it". One easy thing to try is just clean the MAF sensor with MAF cleaner. Might to do the trick.
CATTMAN

 

You may need a resistor inline with the MAF to "trick it". One easy thing to try is just clean the MAF sensor with MAF cleaner. Might to do the trick.
CATTMAN

I was just speaking with the Tech at Porsche and we thought the same thing, any idea what value resistor?

 

Hi all,
Thanks for the replys. I finally got a return phone call to the dealership by VF-Engineering and an email to me.

It seems that the problem here is that at high RPM with boost the MAF is out of range. VF-Engineering's answer to that is to put a resister in line on the signal wire to the MAF to give lower numbers back to the DME or as an alternate adjust the software to scale down the MAF. The problem of course is that we will have to confirm that the AFR is not too lean and not safe.

Basically this is a BS fix. Rather than replacing the MAF with a MAP sensor and properly tuning to the MAP they know there is an issue here and their fix is to give false readings from the MAF across the entire RPM range to smooth out the high end.

Anyone know a good tuner in east central florida ?

 

Been a long time but I think VF installed a 370 Ohm resistor!

 

Been a long time but I think VF installed a 370 Ohm resistor!

Thank you, we have decided against the resistor as that will fool the MAF thru the entire range which could lead to leaning out the engine which is not safe. Finally got in touch with VF Engineering and they are supposedly testing the software against another 997 to see if there is something wrong with their programming. This has been going on for 3 weeks so I am holding my breath. Meanwhile I have installed a switch to turn off the MAF when desired which puts the car in open loop and it runs good then. I am leaning towards changing the Oxygen sensors even though the voltages and flip/flop's between +-5 volts seems to be working correctly.

 

If I remember correctly, I think Scott with Softronic is in your area. He should be able to help.

 

Do you have a contact telephone or email for him?
Thanks,
John

 

I pm'd you his email address.

 

I was thinking of this today and why don't you run a boost activated switch.....so that when the engine is under boost it automatically switches to NO resistor(where you say the car runs fine) and when under normal driving it runs off of the resistor!? May not be be what you want to do but should work and pretty easy to do!

Stacy