Question:

I know JWT advises against the use of any fuel management (Cartech/Vortech FMU, S-AFC/Fields SFC, etc, etc)

Does anyone know why? Is anyone running this setup with a FMU and/or S-AFC installed?

What's so bad about it? I imagine the JWT can't make your A/F ratios perfect, so what's wrong with using a Cartech and S-AFC to "fine tune" the A/F Ratio and Injector Pulse Width?

I figured I'd ask because people ask me this all the time and I have no idea....

So let's discuss!

IanS

 

Because JWT bases their pulsewidths on known factors. Injector size/fuel pressure/ecu imputs.


If you change the fuel pressure, the pulsewidths will be "off" across the board(or whenever you raise it ie.. boost). You might want to fool with the safc for fine tuning but FMUs are considered gross adjusters. Unless, there is some big descpencies in the JWT ecu tuning, you would be hard pressed to improve on it.

 

Yes, but you change the fuel pressure and make the pulsewidths "off" with a stock ECU in the same way by using an FMU, correct?

But let's say that my JWT ECU was overly conservative and gave me a 10:1 ratio - I would need a FMU to re-tune it to 12.1:1 since a SAFC probably wouldn't be safe to adjust that much with.

Or even worse - what if the JWT somehow runs overly lean, like 14:1??

Then why couldn't I use the Cartech...what's so horrible about it?

That's more my question I suppose....just theoricising.

I suppose I'll find out myself after I install everything back in come January. Just wanted to know if anyone has done testing by using both. I guess I'll install the SC, 370's, and such and remove the FMU, dyno tune, then add the FMU if need be.

I guess also I just don't like the idea of not being able to tune using the adjustable Cartech. I'll probably get over it when I'm pushing over 300hp.

 

like Jeff is saying...I think its pretty much plain and simple from my understanding that JWT(and most any other chip turners) designs their maps off 1:1 FP(ie stock, un-altered FP) so any adjustments as far as FP could throw you waaaaaaay off unless JWT specifically designed your program to work off a higher FP for some reason. but AFC fine tuning is definently a viable option, many do fine tune over JWTs programs after install to clear up any "spots"...talk to any chip tuner and you'll get a frown or a nasty email when you mention FMU

 

http://forums.maxima.org/showthread.php?t=268093

Ian. Read this post Stephen is laying down some nice info here.