Coleman

Cheers- I was wondering if anybody had a ROW de-tuned chip for a 95 ECU that allowed the 993 to run on lower octane fuel-? I think Porsche used these in Africa and other places where the fuel was dodgy.. It's rather simple to make a piggyback duel-boot EPROM, a single switch could choose between the lower octane EPROM and the higher- check this Eprom duel boot If you have a chip, I'd like to borrow it so I can burn one. I'm gonna be driving across the country this summer.. this could save tons of cash with the price of gas.. (it's not like I need the extra power the higher octane gives me in Montana ;-)

Coleman-

Sooner

You should give Steve W. a call at Rennsport Systems. He does chips, & I am betting he could could map it to whatever fuel you want.

RallyJon

Can't the stock map pull enough timing to compensate?

Coleman

I dunno.. I never ran anything lower then the 91 we get out here on the west coast-

Coleman.

TomF

Even with the chip, I wouldn't run lower octane fuel just to save a few bucks. The long-term damage to your engine could be very $$$$. Just my .02.

Coleman

Wait, "long term damage" like, what? pre detonation? Wouldnt that be taken care of with the new timing curves?

Coleman-

Peter R.

You don't need the chip. If you run 93 or 91 octane you can turn the switch on the DME to a lower setting. I'm sure there's a post on this board somewhere. There's posts on everything on this board !

Peter R.

Coleman

.. Wait, wasnt that switch (5 or 6 postion potentiometer inside the ECU) only on 964's and maybe some 94 993's? I think it's not on the newer 95 motronic.

Coleman.

JasonAndreas

The fuel quality switch was only used on the 964 up until March 1990, nothing made since then will have one.


The MY94-95 993 ECU supports multiple mappings (variant codings) internally for USA/CAN, ROW, M150 (No Catalytic Converter), RS, etc. The map selection is controlled with a jumper and a resistor so it shouldn't be too difficult for someone to attach a switch and some debounce circuitry.

TomF

I would second the notion of calling up Steve W. for his take on this. It is an intriguing idea, but lower octane in a 993 always makes me nervous. These cars really want to drink 93+, unfortunately around the NW, we only get really crappy 91. Keep us posted about what you find out.

Geoffrey

With proper programming, you can run these engines on 87 octane.

Steve Weiner-Rennsport Systems

Yessir, but they won't get out of their own way.

These engines become VERY lethargic when programmed for crap gas.

Coleman

Okay.. I agree, bad idea.. Forget I even suggested it..

Coleman-

Bruce SEA 993

I'm glad that is cleared up...sounded like a false savings to me. All there was available in Montanabaun was 91 and I would have prefered 93 for my high speed runs there (don't try this at home and no animals were harmed etc, etc...disclaimer after disclaimer).

TomF...91 only in Seattle. Me thinks you meant 92. Also there are several places to get 94. Cenex in Auburn and Black Diamond. Also, there is Trick Racing gas in Auburn to blend to 93 if you want. Still, you have to go to Auburn to get it.