OK, revlimiter stuff here we go. I did quite a bit of research a while back regarding rev limiters. (google my name and rev limit)
this doesnt make me an expert by any means, but here is what I have gathered and beleive to be fairly accurate.:
the rev limit on these cars is set by a combination of the knock box and the ECU itself. not the fuel pump relay like a lot of people beleive. when the rev limit is reached, the ecu cuts the fuel (by way of the fuel pump,) while the knock box causes the spark to retard.
I have opened up the fuel pump relay in my scirocco (that ahs a rev limit of 6800) to prove that there is no logic in the relay. its just a relay, nothing fancy.
more pics of that can be found here: http://www.angrymods.com/proje...relay/
I beleive the 16v rocco rev limit is actually set at 6800 roms, while the 89 GTI rev limit is set to 7200. you can get the ECU and knock box out of a 89 GTI and raise your limit. but you will still suffer from fuel starvation due to the limitations of CIS at those RPMs.
at one point we had a theory that you could swap out a crystal in the knockbox with a higher frequency one and basically overlock the chip, faking it into beleiveing the rpms were lower than they actually were. thereby preventing the knockbox from retarding the spark. I have some pics of that.
and here are some pics of Barnys Knock Box, who supposedly raised his spark retard rev limit using this method. http://www.angrymods.com/proje...ys_KB/
so anyway, I did some research, found out about that much, never could locate a crystal of that frequency in the USA (thats a specialty NASA part or something) and gave up eventually.
you may as well just go with megasquirt and be done with it.
The opinions on this seem highly varied in all the historic threads I've looked at.
There are multiple references to different fuel pump relays. Some say that running the blue stock relay has no rev limit. This is not true at all as I have the blue relay and fuel dies like clockwork at 7200 rpm
Others say it is a function of the knock box breaking the relays ground circuit at 7200 rpm. This seems plausible. There is also mention of aftermarket knock boxes that defeat the rev limiter.
Why on earth do I want to do this???? When I am racing auto cross I could really really use the extra 500 to 1000 rpms I think my engine is capable of. I'm pulling very strong when I hit the limiter and it's driving me nuts.
Has anyone successfully defeated this system? (without changing out your engine management system)
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