400 rpm

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Rob Stevens
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Re: 400 rpm

Post by Rob Stevens »

Have been thinking about this, if you used an idle air valve the car could drive its self at very low rpm, however I've checked the software and the minimum speed for auto idle control is 600 but I think this could still work fine. But you would have to use map corrections.
stevieturbo
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Location: Norn Iron

Re: 400 rpm

Post by stevieturbo »

I've always found idle air bypass valves to be tricky, even for a simple idle.

I'm sure that with a normal open throttle and reduced timing you could probably get rpm down quite low. Although that may reduce usable torque too far.

It's an odd one for sure, and would require testing various options.
Trials
Posts: 9
Joined: Tue Feb 25, 2020 12:29 am
ECU Model: S60 Pro

Re: 400 rpm

Post by Trials »

Yes it’s an interesting conundrum. The car as I bought it has no idle control and all vacuum connections blanked off.
stevieturbo
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Re: 400 rpm

Post by stevieturbo »

Trials wrote:Yes it’s an interesting conundrum. The car as I bought it has no idle control and all vacuum connections blanked off.

The OEM standard car, or the trials vehicle with the engine fitted ?
Alex DTA
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ECU Model: S40 Pro
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Re: 400 rpm

Post by Alex DTA »

An added complication is that the ECU will revert to the cranking timing if the RPM drops below 500 RPM (the minimum transition from cranking threshold).
katana
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Re: 400 rpm

Post by katana »

Having just re-read your initial post I think maybe lowering the engine rpm isn't necessarily the 'right' way to go! You said a steady low rpm is desirable for traction but surely that would be wheel rpm? The engine could be running at 1000 rpm but then through a (say) 3.65:1 gearbox and a 5:1 rear diff ratio and you've got 55 rpm wheel speed - the engine would likely run bang-on steady at that speed (using IAV / timing) and options using more than one gear? Sorry if I used Ford ratios - its what I know LOL!
stevieturbo
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Re: 400 rpm

Post by stevieturbo »

Alex DTA wrote:An added complication is that the ECU will revert to the cranking timing if the RPM drops below 500 RPM (the minimum transition from cranking threshold).
Is this not a user adjustable setting ?


katana wrote:Having just re-read your initial post I think maybe lowering the engine rpm isn't necessarily the 'right' way to go! You said a steady low rpm is desirable for traction but surely that would be wheel rpm? The engine could be running at 1000 rpm but then through a (say) 3.65:1 gearbox and a 5:1 rear diff ratio and you've got 55 rpm wheel speed - the engine would likely run bang-on steady at that speed (using IAV / timing) and options using more than one gear? Sorry if I used Ford ratios - its what I know LOL!
Agreed as said earlier. It just seems like a poor way to approach things.

I'd want a higher engine rpm, stability, excellent control over torque available etc etc. trundling down to a very low rpm at the point of stall just seems the wrong way to go about it. Torque can be reduced quite considerably through tuning where needed
Alex DTA
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Re: 400 rpm

Post by Alex DTA »

stevieturbo wrote:
Alex DTA wrote:An added complication is that the ECU will revert to the cranking timing if the RPM drops below 500 RPM (the minimum transition from cranking threshold).
Is this not a user adjustable setting ?
The transition from cranking to running is user adjustable, from 500 to 4000 RPM.
The ECU will then use the main ignition map until the RPM drops below 500 RPM again.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: 400 rpm

Post by stevieturbo »

Alex DTA wrote:
stevieturbo wrote:
Alex DTA wrote:An added complication is that the ECU will revert to the cranking timing if the RPM drops below 500 RPM (the minimum transition from cranking threshold).
Is this not a user adjustable setting ?
The transition from cranking to running is user adjustable, from 500 to 4000 RPM.
The ECU will then use the main ignition map until the RPM drops below 500 RPM again.
Ahh, so it cannot be set to below 500rpm.

So in this instance the ecu would not be suitable for his desired application.
Trials
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Joined: Tue Feb 25, 2020 12:29 am
ECU Model: S60 Pro

Re: 400 rpm

Post by Trials »

A couple of points of clarification.

It’s the trials car that has no idle control not the donor car.

To further explain the need for the very low rpm.
The car could very well be being driven as suggested here at a 1000 rpm. This would most likely be on a very slippery surface. If traction is lost then forward momentum of the car is lost. To regain traction the rpm must be dropped so that wheel speed matches vehicle speed so that the attempt to regain traction is as gentle as possible. It’s in these circumstances that the very low rpm are required.
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