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Megasquirt advice
prelude1980 - 24/7/10 at 05:16 PM

I've Posted on Msefi but not had any replies yet so hoping to get a bit of advice

I'm running ms2 v3 firmware 2.88 using alpha N. I'm after some advice on the cold start and some general tune on the VE table and Accel enrichments.

I can't seem to upload the files but put a link to my original post on MSEFI



MSQ

coyoteboy - 11/8/10 at 12:12 AM

Unless someone has worked on your exact engine it's hard to tell, this is the difficulty with MS quite frankly - the wiring etc is easy, it's getting a feel for the control of the parameters to get your car running. Do you have wideband lambda feedback? What stage are you at? Is it starting at all? I installed, tuned/mapped my boosted engine from scratch so I should be able to help, but I can't guarantee it!

[Edited on 11/8/10 by coyoteboy]

fatbaldbloke - 11/8/10 at 08:46 PM

You don't include much detail on your cold start problems, but it's very common to under-fuel. Cold starting really needs a load of fuel chucked at the engine. Typically, the cold start pulse width is around 5-6 times the pulse width you see at idle. So, if your datalog is showing 4ms at idle, go for something like 20ms for a full cold start.

prelude1980 - 12/8/10 at 05:24 PM

i never know what information to include. But would you really add so much? what happens with the advance do you put more advance too?

prelude1980 - 12/8/10 at 05:27 PM

quote:
Originally posted by coyoteboy
Unless someone has worked on your exact engine it's hard to tell, this is the difficulty with MS quite frankly - the wiring etc is easy, it's getting a feel for the control of the parameters to get your car running. Do you have wideband lambda feedback? What stage are you at? Is it starting at all? I installed, tuned/mapped my boosted engine from scratch so I should be able to help, but I can't guarantee it!

[Edited on 11/8/10 by coyoteboy]



i got the engine running and drivable, the starting seems a bugger because as i start it needs my foot on the pedal to get started and when it does dies pretty much straight away, start a 2nd time then a third and on the third it usually idles with a bit of pedal.

fatbaldbloke - 13/8/10 at 07:23 PM

OK, simple steps, but with a proviso. My knowledge is really with MS1 so I can tell you in principle what to do but you'll have to tweak to suit MS2.
As it's running after a fashion first get a smooth idle, maybe 1000-1100 rpm. Don't worry about getting it slower. Make sure the throttle bodies (assuming that's what you're running and not just one TB) are balanced. Set the bottom tps value row in the VE table to your tps value on idle so you can adjust the VE values without worrying about interpolation between cells. Set the bottom column at around 800 rpm (so you can tweak the VE to prevent stalling) and the second column at your idle speed. This way you can set the idle in just one cell. To begin with also set the idle ignition advance at 10 deg btdc. You can change all this later but it's just a way of getting started. Don't worry about AFR at idle just getting it running really smoothly.
Assuming you've done that, log the pulse width at idle. To get a good cold start you need to set two tables, one is the cranking fuelling, which should be around 5x the idle pulse width at cold, and just scale up through a range of temperatures. The other is post start enrichment, go for something like 150 cycles and this should be around 20% at 4 deg C, scaled to 0 at around 75 deg C.
Also, during setting the thing up set the AE trigger really high so any ripple you have doesn't set off the AE. This should be set last just as a final tweak and not used to overcome other problems. Give it a try; does that make sense?
Datalogging is really your key to progress once you get it running, always datalog right from starting up, then you can see what's happening and adjust accordingly.

[Edited on 13/8/10 by fatbaldbloke]

[Edited on 13/8/10 by fatbaldbloke]

matt_gsxr - 15/8/10 at 07:39 PM

That is a nice little set of information FBB.

Regarding the differences between MS1 and MS2.

In MS2 the cranking pulses are set as a percentage. This is the percentage of the required_fuel (well it says this, but I am not convinced). Default runs from 312% at - very cold, to 101% at 100degC. At 20deg it is around 180%. The manual claims that this is a good starting point.

Matt

prelude1980 - 16/8/10 at 05:28 PM

quote:
Originally posted by fatbaldbloke
OK, simple steps, but with a proviso. My knowledge is really with MS1 so I can tell you in principle what to do but you'll have to tweak to suit MS2.
As it's running after a fashion first get a smooth idle, maybe 1000-1100 rpm. Don't worry about getting it slower. Make sure the throttle bodies (assuming that's what you're running and not just one TB) are balanced. Set the bottom tps value row in the VE table to your tps value on idle so you can adjust the VE values without worrying about interpolation between cells. Set the bottom column at around 800 rpm (so you can tweak the VE to prevent stalling) and the second column at your idle speed. This way you can set the idle in just one cell. To begin with also set the idle ignition advance at 10 deg btdc. You can change all this later but it's just a way of getting started. Don't worry about AFR at idle just getting it running really smoothly.
Assuming you've done that, log the pulse width at idle. To get a good cold start you need to set two tables, one is the cranking fuelling, which should be around 5x the idle pulse width at cold, and just scale up through a range of temperatures. The other is post start enrichment, go for something like 150 cycles and this should be around 20% at 4 deg C, scaled to 0 at around 75 deg C.
Also, during setting the thing up set the AE trigger really high so any ripple you have doesn't set off the AE. This should be set last just as a final tweak and not used to overcome other problems. Give it a try; does that make sense?
Datalogging is really your key to progress once you get it running, always datalog right from starting up, then you can see what's happening and adjust accordingly.

[Edited on 13/8/10 by fatbaldbloke]

[Edited on 13/8/10 by fatbaldbloke]



Wow i'll start having a play with what you've said and post back what happens

coyoteboy - 17/8/10 at 10:33 AM

Cold start tuning is very hard, it's bordering on flooding the engine (as I found out a few times) so creep up in amounts, using flood-clear to blast as much as possible out before attempts.

The biggest problem here is making sure you keep your battery OK as if you've not set your battery correction up well your fuel amounts will vary massively from the beginning crankings to the end crankings across the session - best achieved by keeping a running normal car hooked up to the kit with good jump leads during the process - this doubles the CCA cap of the effective battery and maintains more charge while you fiddle between cranks.

Use the above amounts to get in the right ball-park. IIRC during cranking it is ignoring the throttle input if you set the cranking speed correctly, this means that if you need to give it some throttle, you're probably over-fueling for the temperature. Remember that just a few degrees makes a huge difference to starting ability, so give it time to cool between attempts when fine-tuning it, but don't worry to start with.