14CUX EFi questions

[100SRV]

I have some questions below based on this quote from "a source"

" the orange and black wire also needs earthing through a resistor for manual and not for Auto, think that's the right way and from memory it was around 480 ohms, don't quote me on that"

From reference to schematics it looks to me as though it switches directly to ground when the transmission is in neutral, am I correct in thinking that when "floating" the result is a raised engine idle allowance to cater for clutch pack drag in the automatic transmission? This being the case perhaps I could use it as a "raised idle" when in low ratio...

It seems that the road speed sensor coupled with throttle position gives three idle management states:

0 road speed, 0 throttle = idle (~600rpm)
low road speed, 0 throttle = raised idle (~1200rpm)
road speed, throttle = no idle management

Is this correct?

Also I have read that running without Lambda sensors results in better part throttle economy as the mixture isn't being forced to stoichiometric do any of you have practical results to back this up?

cheers!
100SRV

[blitzracing]

Both the road speed and throttle pot signals can hold the idle high, I was under the impression the higher idle when the car was moving was to reduce engine braking, but I dont know how the auto side of things work. As for fuel economy, its all very marginal as yes you can run leaner under light load, but it runs a bit richer at low speed. (this is set by the CO trim value) The RV8 does not like being forced to run as lean as the catalyst map tries to force it so you can end up with a poor idle and snatchy low speed response. I have only compaired the two maps back to back by observing the fueling with an on board lambda gauge, and the catalyst map really does swing about a fair way depending on how good the base mapping is, so you can end up with periods of both rich or lean overshoot, so I doubt you would get a definative answer. You wont suddenly gain 3 mpg!

[100SRV]

Thank you for the reply Blitz!

I earthed the orange-black wire, maybe experiment with it later.
I didn't suddenly find that the fuel gauge stopped moving either ;-)
Throttle response is odd when compares to the previous SUs which had a hybrid of Rover P6 and Range Rover linkage, this had the effect of squashing the power modulation into the early part of the pedal travel. Now it has all proper bits it responds in a much more linear fashion. Time to re-train the right foot...

Having just returned from road-testing the car I have another question:
On start-up there is quite a bit of engine speed "flare" - it goes immediately to what sounds (no tacho yet) like 2000 or so rpm before slowly dropping to idle speed. I don't like this as I'd rather the oil pump puts some pressure in first before revving especially if the car has been stood for a while and the tappets have drained. Is this normal? Can it be trimmed out or is a modified map required?

100SRV

ETA - I think that the idle bypass air valve might not be happy (perhaps stuck open admits more air at startup) BUT the idle speed winds down so maybe not...mayby it needs cleaning and oiling?

Edited by 100SRV on Thursday 19th May 22:50

[blitzracing]

That high RPM is perfectly normal, as part of the power off cycle of the ECU is to wind the stepper motor air control wide open. This is done for two reasons, to reset the stepper to its "home" position,(as there is no stepper position feedback) and two provide enough air to ensure the engine starts easily when cold. It will then reduce the idle in stages as the engine warms up. The stepper control is held in the fuel chip, but information on the chip layout is almost non existant. Those who have it, wont dilvulge it! A mechanical way of limiting the idle lift is to put a 15mm plumbers gate valve inline with the air feed to the stepper, so you can restrict the airflow by part closing the valve. In terms of delaying the start until the oil pressure has risen, Mark Adams of Tornado systems is able to program this delay into the fuel chip (his Tornado chips already have a small delay programmed in) but its expensive at around £400. Personally I use an electronic timer to hold the 12v supply off the injectors for a few seconds after the starter has engaged, but it would be a nusiance if the engine was warm, so you could use the temp sensor to disable it.

On second thoughts why not put a relay on the oil pressure switch so it keeps the 12 volt off the fuel rail until it opens?

More generally the steppers do goo up, you need to clean the cone, shaft and cone seating area once in a while. Ive done a bit about stripping it out here:

http://www.g33.co.uk/fuel_injection.htm

Edited by blitzracing on Friday 20th May 12:32

Edited by blitzracing on Sunday 22 May 19:36

[100SRV]

Thank you again Blitz, I had a look at the site, very well written and informative. One of the steps I took was to check the base CO setting of the airflow meter, partly because I thought it sounded rich at idle - this was 2.54 Volts! I turned it down to 1.25 Volts and the rev flare on startup is significantly reduced. the engine off airflow meter voltage was within specified parameters (I think it was 0.6 Volts) with the engine off. I will still use a switch to isolate the HP pump relay for cold starts though.

Oddly the idle speed seems to be around 400rpm (I need to buy a better multimeter with more automotive ranges) and adjusting the screw next to the butterfly / bypass air valve port didn't affect this too much. I will check the butterfly clearance when closed to see whether this is too great.

The only other problem is that the improved torque characteristics show up how worn my LT77 is...