Ziad

Hi Felix,

No, I haven't. I've had the car checked for a list of possible cuprits which Kevin helped me with (e.g. wiring, spark plugs, N75 frequency valve, fuel pump, etc.). I've installed a boost gauge and have been monitoring boost with pump and race fuel... Boost is around 16psi with normal fuel... and I've also been having great fun checking the boost with race fuel, which hits 17-18psi

Any suggestions?

Thanks

expressmechanic

I get the same problem when my MAF gets dirty. I just take out the two screws holding it in place, pull it out and spray some carburator cleaner. Then I get the remaining dirt with a paper towel.

If you have a K&N type air filter,this will happen every couple of months. Do not use the K&N oil on the filter.

BTW - I do this around every 2 months and I have never damaged the MAF sensor with carburator cleaner.

If that doesnt help, shoot me an email and ill help you out.

Ziad

Thanks for that!

I'll check the MAF and let you know... I don't use K&N air filter, I use the stock Porsche things

Cheers

TB993tt

A bit of a sweeping statement ? I have run BMC filter for years and never had to clean the MAF

Felix

Hi Ziad. No suggestions from me I'm afraid; I just found your post while searching for something else and was curious how things were.

NineMeister

This sounds like the MAF limit of the Motronic ecu is being reached prematurely. As far as I know, the Motronic ecu monitors the voltage of the MAF circuit and if a predetermined limit is reached it cuts the ignition/boost to bring the MAF voltage back into line. This always happens at peak torque which roughly coincides with the peak efficiency of the turbo/engine combination. If it is this problem there is no immediate and simple fix as the code is buried in the ecu chip. If you have a standard car I do not know why you are reaching the MAF limit unless there is a fault somewhere.

I think the way most tuners get around this issue is to fit a resistor in the MAF supply to reduce the voltage seen by the ecu for any given demand and then rescale the fuel table accordingly to compensate for the change. I have always seen this as a bit of a bodge, but there are other solutions which get around the chip code location problem, like fitting a larger AFM body which flows more air through for any given velocity. We don't work with the Motronic ecu so unfortunately I cannot help any further.

Acropora

Where does one come by this larger AFM body? My understanding is that the MAF is the bottleneck in higher power engines and I'd be interested if there's a larger one available somewhere.

Ziad

Colin

Many thanks for your feed back... My car is modified and I'm checking all the possibilities.

All the best

expressmechanic

Good for you. *Gives you a cookie*

NineMeister

We looked at CNC machining the larger body in aluminium and fitting the standard AFM within it, but never got around to initiating the machining work due to cost. For a one-off you could easily make a new tube and fit the meter but this would not be a sound commercial option. There must be larger AFM bodies available within the Bosch range that would do the job, however I cannot squeeze any information our of Bosch's technical department to deduce a definitive answer.
Does anyone know how Todd or RS get around the stock ecu's MAF voltage limit or do they just frigg it with a resistor (I'm sorry - please read this as "use a voltage clamp") like everyone else?

MarkD

Ziad,
This is a bit old but I am curious, was this resolved?

Ziad

Hello Mark

I had a lot of components checked. In the end, I don't think I changed anything cos nothing needed changing. The problem just never came back...