Cam Advance Leading to Cam Signal Errors

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shalco
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Joined: Mon Sep 05, 2011 2:52 am

Re: Cam Advance Leading to Cam Signal Errors

Post by shalco »

I've attached a picture of some typical values from the data log showing how the advance rockets up once Cam % hits about 90%.

Variable cam advance is only available on the intake on this engine (flat 6) .

I'm not using the position signal from the second cam, and have wired the single DTA output to operate both intakes cams.
Attachments
Cam Advance.png
Alex DTA
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ECU Model: S40 Pro
Distributor: DTA
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Re: Cam Advance Leading to Cam Signal Errors

Post by Alex DTA »

Some people believe that wasted spark burns the exhaust gases better, as you get the second spark on the exhaust stroke. I have no real world data to prove or disprove that.

I can see the problem with your cams. You haven't turned on the PID loop.
However, your target map isn't ideal, so it won't work very well if you do. You'll need to refine that a bit first. I don't have the target maps for that engine, but you may be able to find them online. If not, just smooth out what you have, and then turn on the PID loop.

I need to write an article on how cam control works, as it's asked quite often.
shalco
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Joined: Mon Sep 05, 2011 2:52 am

Re: Cam Advance Leading to Cam Signal Errors

Post by shalco »

Thanks I'll smooth it out, I've got an idea of how it should look from a technical description.

With the PID loops settings is it sensible to only allow values between say 88% and 95%, as that was the response range without the PID loop in place?
Alex DTA
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ECU Model: S40 Pro
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Re: Cam Advance Leading to Cam Signal Errors

Post by Alex DTA »

No.

85% to 95% PWM will advance the cam. 50% will keep it where it is. Lower will retard it.

The base PWM map can only fully advance or retard the cam, it cannot control it. Most often this is just set to 90% in order to get the cams to move quickly in the area the cams need to move.

Then the ECU uses the target map, which is in degrees of advance, to move the cams to the target position. This is the critical map.
shalco
Posts: 11
Joined: Mon Sep 05, 2011 2:52 am

Re: Cam Advance Leading to Cam Signal Errors

Post by shalco »

Ran it today with PID activated, the standard PID control didn't seem to track target cam advance, but when I changed it to use modified PID, it worked a treat!

I haven't had time yet to build an optimised cam target map, the Toyota-2ZZ target looked a reasonable start point so I tried this with great mid range results. A bit of tweaking to do but its looking good !
Attachments
Cam-Adv-Changes.png
Rob Stevens
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ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Cam Advance Leading to Cam Signal Errors

Post by Rob Stevens »

I've never used cam advance but I think you need to use the real time chart and the knobs box set to use cam timing on one knob to swing the cam target around and then adjust the PID controls so that you get the best response you can.
This is before you do any power runs.
Then I'd be inclined to do power sweeps with different cam timing to then build a picture of what the engine likes at various rpms.
But like I say I've never had cam advance!
shalco
Posts: 11
Joined: Mon Sep 05, 2011 2:52 am

Re: Cam Advance Leading to Cam Signal Errors

Post by shalco »

Yes, my next job is to do some full and part throttle power runs at various cam advance settings to get an idea as to what works best where.
Rob Stevens
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ECU Model: S100 Pro
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Re: Cam Advance Leading to Cam Signal Errors

Post by Rob Stevens »

Using the knobs box and cam on the knob should speed up many of the light throttle sites settings.
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ignitionautosport
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Re: Cam Advance Leading to Cam Signal Errors

Post by ignitionautosport »

The manual outlines how to set it up very well; I'd be tweaking the PID so it's perfect tracking (as Rob already said), then set Fuel to closed loop and adjust cam target on the fuel knob. That way when you are changing the cam timing the fueling adjusts to suit by itself - at least in the lighter load sites, you may not want to use closed loop when doing power runs naturally.
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