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Digital Fuel adjuster
niceperson709 - 3/12/08 at 03:37 AM

Just bought one of these to try and play around with the mixture on my N16 pulsar motor and I'm just wondering if anyone here has had any experience with them.

MikeRJ - 3/12/08 at 10:38 AM

It's rather too simple to be safe or effective if I'm reading the description correctly.

If the only thing it is doing is mapping the AFM output voltage to a different level, then how does it differentiate between low engine speed, wide open throttle and higher engine speed with a partialy open throttle where the air flow could be the same?

BenB - 3/12/08 at 11:45 AM

I see no reason why it can't be safe or effective (though there's a big scope for getting things wrong)...

as a step between sticking with an ECU and going for an aftermarket ECU it looks like a nice bit of kit (especially as it can be removed simply if you ever sell the car).

though personally I'd go for a fully mapable ECU and take full control over the engine.... the interceptor will make the ECU change fuelling and ignition- it won't be possible to change one and not the other.

MikeRJ - 3/12/08 at 01:11 PM

quote:
Originally posted by BenB
I see no reason why it can't be safe or effective (though there's a big scope for getting things wrong)...


For the reasons I have mentioned, it's basically a one dimensional lookup table. Since an engines volumetric efficiency changes with RPM and throttle opening this will never give you accurate fueling at all RPM/load points.

Given the apparent complexity of the hardware (for what is really a trivial task) I'm very surprised they didn't implement a 2D correction table.

I guess if you use this to optimise only WOT fueling, then closed loop control should take care of some/most of the inaccuracies at part throttle, but it doesn't seem ideal to me.

[Edited on 3/12/08 by MikeRJ]

britishtrident - 3/12/08 at 03:11 PM

Its the kit sold by jaycar, if fitting I would advise making up proper breakout connectors.

My understanding of most hot wire AFM systems (mainly based on the Lucas with the Hitachi hotwire as used on late 1980s Rovers) the the hotwire output was only used at lower end of the speed range.

With age the hot wire AFM go out of calibration by a mile -- the voltage of the output signal drifts slowly upwards so it could be useful device.

MikeRJ - 4/12/08 at 09:16 AM

quote:
Originally posted by britishtrident
My understanding of most hot wire AFM systems (mainly based on the Lucas with the Hitachi hotwire as used on late 1980s Rovers) the the hotwire output was only used at lower end of the speed range.


I think that was true of most of the true hot wire systems since the AFMs didn't have sufficient dynamic range to cope with everything from idle to WOT maximum RPM.

However, the modern AFMs that use a ceramic heater element seem to have a much greater range, e.g. the one on my car is used to limit turbo boost via a solenoid valve; the ECU looks at airflow vs engine RPM and and calculates boost pressure from this. Why they didn't use a simple MAP sensor I don't know...