Fast start features

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JPh
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Fast start features

Post by JPh »

I have read some lines about rusefi having fast start features, but didn't find were it is documented.

So my question :
If you run fully sequential your engine won't start until sync is achieved so 2 crank turns in worst case. Can we switch to wasted spark and batch fuel during cranking?

Instant start is appreciated by the end user and he thinks bad start means bad running.

Most tunened engines are more difficult to start (valves overlap high compression etc.).
More and more use E85 for it's anti detonation power. But this fuel induces starting problems.
My car has an other problem : it runs a car engine with a motorcycle battery so no margin for cranking.

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andreika
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Re: Fast start features

Post by andreika »

JPh wrote:
Fri Mar 20, 2020 7:10 am
I have read some lines about rusefi having fast start features
Can we switch to wasted spark and batch fuel during cranking?
Yes, that's true. If you enable this option, it will use batch fuel/wasted spark right after the first sync (until fully synced):
faster_engine_spin-up.JPG
faster_engine_spin-up.JPG (22.44 KiB) Viewed 487 times

JPh
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Re: Fast start features

Post by JPh »

Thanks for the tip.
But we have to wait for cam sync to begin fuel and spark or does it switch to crank sync?

mck1117
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Re: Fast start features

Post by mck1117 »

By the way - batch fuel is pretty good by itself. It's actually pretty hard to detect a difference between batch and sequential without an accurate dyno, fuel flow meter, and exhaust gas analyzer.

Here's what a startup sounds like on my car (5.3L v8, no cam sensor connected, batch fuel, wasted spark):



(don't mind the tach reading zero :P )

The startup fueling isn't ideal, so it could probably start a bit faster with some tweaking. I know @OrchardPerformance has been doing some work to make his car start up really nice, so he might be able to share his progress here.

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Re: Fast start features

Post by JPh »

Thanks for that exemple.
On every rusefi start I have seen on videos, it seems allways to be some sort of a delay before something happens.
I hope I will soon have my engine starting to make measurements to compare between oem and rusefi.

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Re: Fast start features

Post by puff »

I believe it has something to do with trigger-wheel tooth patterns and synching methods.
With old-style distributor-based ignition you get the right spark immediately after you start cranking, while here we wait for the missed tooth + then another entire crank rotation (at least this was true some time ago).

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andreika
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Re: Fast start features

Post by andreika »

JPh wrote:
Fri Mar 20, 2020 1:06 pm
But we have to wait for cam sync to begin fuel and spark or does it switch to crank sync?
In fast spin-up mode, we wait for crank sync. Ignition/injection will start right after the first sync point of the primary trigger.
Please be aware that this mode works only for certain trigger types (e.g. 60-2).

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Re: Fast start features

Post by Abricos »


mck1117
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Re: Fast start features

Post by mck1117 »

andreika wrote:
Sat Mar 21, 2020 5:38 pm
JPh wrote:
Fri Mar 20, 2020 1:06 pm
But we have to wait for cam sync to begin fuel and spark or does it switch to crank sync?
In fast spin-up mode, we wait for crank sync. Ignition/injection will start right after the first sync point of the primary trigger.
Please be aware that this mode works only for certain trigger types (e.g. 60-2).
I think it works on most trigger types with enough teeth - I know it works on my 24 tooth LS trigger pattern.

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Re: Fast start features

Post by JPh »

Thanks Abricos for the video.
I will be happy with such a starting.

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Re: Fast start features

Post by JPh »

If I see well the sync tooth is just before the sensor granting an immediate sync.
As stated above its the main condition of fast start.

OrchardPerformance
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Re: Fast start features

Post by OrchardPerformance »

Just something to note here, I have found the lower my battery charge the longer the engine takes to fire, with a charged battery I can get OEM quality starting.

I am investigating this a little as I am wondering if this is an effect of not having a voltage correction for dwell and a large voltage drop during cranking.

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Re: Fast start features

Post by 960 »

OrchardPerformance wrote:
Tue Mar 31, 2020 9:15 am
Just something to note here, I have found the lower my battery charge the longer the engine takes to fire, with a charged battery I can get OEM quality starting.

I am investigating this a little as I am wondering if this is an effect of not having a voltage correction for dwell and a large voltage drop during cranking.
Whats your cranking settings now?

I am thinking of enrichments etc you had best luck with.

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Re: Fast start features

Post by mk e »

I have always felt that fast start is best left to OEMs trying to satisfy irrational customer perceptions and racers want start DELAY so there is time to get oil, often thicker and much slower moving than the 0W20 many OEMS now use , flowing BEFORE the engine comes to life. Years ago before EFI I hooked ignition to the oil pressure safety switch on a setup....much like Honda lawnmower engines connect it to the oil low switch today. That was a drysump much like my current setup and cold it was at least 1-2 revolutions before there was oil flowing everywhere but with carb and distributor it could start ...probably 1/2 a rev which was bad.

When my engine finally goes back together I will be adding an oil pressure transducer to feed pressure info to the ECU and will use that to enable fuel during cranking and probably to force a limp condition at below normal oil pressure and shutdown at some low oil pressure value. Still just a plan at the moment but as I continue to repair damage from low running with low oil pressure because I didn't believe the gauge it a pretty firm plan along with a more full appreciation of the standard approach of redundant sensors on critical items.

just a though

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Re: Fast start features

Post by JPh »

I agree with your thought for a race engine, and specifically one with a dry sump.
But for my very standard engine with a bike battery, I would like to have some margin not to stay caught in a desert place. Perhaps I will enhance the starting ability by adding supercapacitor.

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