Dead time mesurement

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Rob Stevens
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Dead time mesurement

Post by Rob Stevens »

I had a play last night with the 2/4 stroke mode, it's brilliant. I changed my dead time from 0.75ms to 0.9ms to get it bang on, very simple yet clever Idea of Allan's.

I guess you need some sort of adjustable voltage supply to do this for the entire voltage range, but worth a play if you have never tried it.
stevieturbo
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Re: Dead time mesurement

Post by stevieturbo »

That's the thing, without varying the voltage the reading becomes almost irrelevant as the single static value is just added to the IJPW anyway and never changes

I really dont get the whole obsession some have with IDT, the older ecu's and other ecu's ran just fine before it was even a consideration !

And in an ideal world, your voltage should be pretty stable anyway, and if it isnt then you need to rectify that.
MarcoV6T
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Re: Dead time mesurement

Post by MarcoV6T »

Yes but the static value(IDT) will be added twice in two stroke mode(instead of only once in four stroke), and will change the AFR reading if it's not close to the 'real' IDT for that voltage, so yes it's still relevant.

It will also at least give a starting point if you can't change the voltage.

Is it useful? I guess it will help having a better idle with big injectors when a fan kicks in, as long the system(DTA) reacts fast enough. At low and mid load, it will be insignificant with a good working lambda regulation, and at full load, peanuts.
Bollah
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Re: Dead time mesurement

Post by Bollah »

Thanks for tip. I'd never looked at this, so tried it yesterday. Seems the values initially set were wrong and causing me a few minor issues, so changed it from 0.7ms to 0.75ms and a minor tweak to my idle settings and suddenly the car is just that much nicer to drive and idle :)
corsaboy
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Re: Dead time mesurement

Post by corsaboy »

MarcoV6T wrote:Yes but the static value(IDT) will be added twice in two stroke mode(instead of only once in four stroke), and will change the AFR reading if it's not close to the 'real' IDT for that voltage, so yes it's still relevant.

It will also at least give a starting point if you can't change the voltage.

Is it useful? I guess it will help having a better idle with big injectors when a fan kicks in, as long the system(DTA) reacts fast enough. At low and mid load, it will be insignificant with a good working lambda regulation, and at full load, peanuts.
are you sure Marco that in 2stroke mode the IDT will be added twice.
because than I still can not explain my problems.
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ignitionautosport
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Re: Dead time mesurement

Post by ignitionautosport »

It is a great feature.

Dead time vs voltage is awesome on stuff with marginal charging at low rpm, e.g. underdriven alternator so it doesn't fly apart at race rpm. Also means you won't lean out if charging system fails.
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gnutz2
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Re: Dead time mesurement

Post by gnutz2 »

I agree, it's great.

If you need to measure the dead time at different voltages just disconnect the alternator and run the test, then flatten the battery with the lights and run the test again.
stevieturbo
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Re: Dead time mesurement

Post by stevieturbo »

ignitionautosport wrote: Also means you won't lean out if charging system fails.
That ignores and does not compensate for loss of fuel flow from lower voltage to the pump.

It would be a dangerous assumption to expect AFR's to be maintained should the alternator fail just because IDT values may be correct.

A good closed loop system will go some way to providing safety, but even this needs treated with caution under some circumstances, and at some point safety limp mode features really need introduced.
PhillipM
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Re: Dead time mesurement

Post by PhillipM »

Better than not having them.
stevieturbo
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Re: Dead time mesurement

Post by stevieturbo »

PhillipM wrote:Better than not having them.
Many ecu's never had them for years....and never once did I have problems tuning them.

Just the same as you could refrain from using them with DTA if you wanted, and prior to the S series, DTA never had them either. 7 years with the old P8 and various injectors and never had any problems.

yes having them with correct data across all voltages is a good thing, but it's wrong to think they'll save your engine in the event of major failures elsewhere like alternator failure....and I had a pretty major bang that will support that lol.

when you know your alternator is fucked...it's more sensible not to race, and I say that from direct and very costly experience.
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