Dead time mesurement

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ignitionautosport
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Re: Dead time mesurement

Post by ignitionautosport »

I've also run a (electrically) total loss EFI speedway car. Dead time mattered there.

It's like saying "oh this engine has variable cams, it makes it nicer to drive but engines never used to have them and they ran fine, so you really shouldn't get to hung up about setting them up".

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If flow drops enough to drop pressure in the rail, then your fuel system is a bit marginal, I'd suggest.
Dead time is just one factor, and it may or may not help depending on other factors.

Recently one of the local club guys raced his Evo with a fucked alternator in a hillclimb, did fine all day just charged it off his ute between runs.

It didn't blow up.
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PhillipM
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Re: Dead time mesurement

Post by PhillipM »

stevieturbo wrote:
when you know your alternator is fucked...it's more sensible not to race, and I say that from direct and very costly experience.
I've run without the alternator when required. Running around in puddles, streams, knee deep mud and sand tends not to be too kind on them. Having ignition/injector compensation for the system voltage is a big help when you need it. If I miss one race just for an alternator issue I may as well pack up for a year.
Not to mention they're underdriven to cope with the heat and rpms, so low down with the load on the voltage drops to mid 12's instead of ~14v.
Why would I not spend 10 minutes filling a few cells that might help right when it touch or go?

Hell, engines never used to have these EFI things, carbs used to work just fine, never had any trouble tuning them either...
stevieturbo
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Re: Dead time mesurement

Post by stevieturbo »

Driving around in puddles doesnt quite place the same loads as pushing 1000+hp from a setup with no alternator though.

Things can...and did go bang and IDT values were correct as decided via DTA's own methods.

And as for the speedway car, when it is built and tuned and all components designed for loss of battery charge including fuel and ignition systems again it's a totally different scenario.

As for variable cams, often people do get rid of them in the quest for power. On some applications retention can be of benefit, in come cases not so as it can limit cam profiles.
PhillipM
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Re: Dead time mesurement

Post by PhillipM »

Come and try it when you're foot is flat to the floor for 30-60 seconds (try that on a circuit) at full load when all your engine, rad and ancillaries are coated in a nice layer of insulating mud.
Then you can tell me it's not hard on engines.
MarcoV6T
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Re: Dead time mesurement

Post by MarcoV6T »

corsaboy wrote:are you sure Marco that in 2stroke mode the IDT will be added twice.
because than I still can not explain my problems.
Well, the injectors will fire every revolution, whereas in sequential they will only fire(open) once every two revolutions.

This is how(my guess) DTA ‘measures’ the IDT; let’s say that the real IDT of a specific injector is 1.00ms at 14V, but you put 1.50ms for the IDT, and let’s say that you need to inject a net of ‘1.00ms’(idling) of fuel, which comes from the fuel map.

Now when running sequential DTA will open(on time) the injector for (1.00 fmap + 1.50 IDT) = 2.50ms every two revolutions(one oto engine cycle), or a ‘net’ or real injection of 2.50 – 1.00(real IDT) = 1.50ms.

But in ‘2 stroke’ it will be (0.50 fmap + 1.50 IDT) x 2 = 4.00ms, or a ‘net’ or real injection of 4.00 – (1.00 * 2) = 2.00ms.

Thus the AFR will change considerably if the ‘real’ IDT is not correct(or close to) when switching from sequential to two stroke at idle and low loads.

corsaboy, do you still got problems?
corsaboy
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Re: Dead time mesurement

Post by corsaboy »

less problems, next week i'm going to the tuner to do a full day on the dyno..

In my logging i had before on idle an IPW of 1 - 1,1ms
My fmap was 0,87 with a underpressure comp from -60 / -70%
My IDT at 13,7v is 0.7. When i calculate this the 1 - 1,1 ms is a vaild value.

I couldn't get my lambda good, was always around 0,77 - 0,81

Now i had played around with the new DTA and we have seen in the other topic that i needed to do a min add of 100% to my fuel map.

My IPW on idle is now without pressure compensation 2- 2,4 ms with a lambda (closed loop) of 0,84
The fmap is around 1,8 and the IDT is still 0,7
with a little compensation from the lambda it's now running ok in idle

Without compensation and with a lambda of 0,94- 1,00 i had a fmap of 1,1 and the IDT 0,7


I'm still not sure why map old mapping isn't good anymore..
My only explanation is that the ECU had to be in 2stroke.. All the mappings say not but i cant explain why i've to add a little more then 100% to my fuel map
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