Thread: VF570 installed
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      12-14-2012, 01:20 PM   #63
GuidoK
#buildnotbought
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If it wouldn't be tuning you'd get an engine light with some obd2 code like p0171 or so.

But what they can have done is adjust the mixture (in the tuning), so the pumppressure doesn't get too low.
If you calculate: @6750rpm the afr is about 11.8, so thats about 572x parts gas (6750/11.8)
@7800rpm (the max in this run) the afr is about 13.6, so thats (also) about 573x parts gas.
If the afr hadn't changed, the parts gas used (per minute) would be higher of course.

It's a big coincidence that in the high revs the engine (with higher afr) uses exactly as much fuel than in the highest rev before the afr start to rise.
So it's not because the fuel pump stops suppling fuel (no obd code), but maybe it is the result of careful tuning not to overstress the pump (resulting in fuel pressure too low) and letting the afr rise.
But a lean mixture gives more power (that could be the other reason). It's just bad for your engine if it gets too lean (valve temperature too high so they burn).
Still, then why have a high afr in the mid revs.
If the afr didn't rise above 6800rpm, it sure wouldn't produce so much power I think. Maybe up to 50HP less.

Last edited by GuidoK; 12-14-2012 at 01:25 PM..
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