Startup help please.

[conn110]

1965 Corvair Port injected 164ci 6 cylinder MS 2.2 Megatune 2.25

I can get the car to start if I crack the throttle to about 7-15%. Once the throttle closes, it dies.

I'm trying to tune startup as suggested in the megamanual. It says to change the cranking pulsewidths and req-fuel to get it to start. Is there any method to be using? Which pulsewidths? Priming? The upper temp or lower temp? All of them? Is lower pulsewidth leaning them out or richening them up? Just a short primer on the subject would be great.

[conn110]

I should also add that I am using the throttle body from a 300zx. There are no holes in the throttle plate to let idle air in. Should I crack it open a bit and then tune from there?

[Bernard Fife]

conn110,

I have just edited the manual to clarify this. It now says:

Typically, the first time someone tries to start their engine with MegaSquirt, it starts after about 5 minutes of alternating various cranking pulse widths numbers to get started (on the Enrichments page), and changing the:

- Cranking Pulse Widths: Remember that the cranking pulse widths need to be with ~0.5 milliseconds of the optimal value at both -40ºF and 170º F. Generally the -40ºF cranking pulse widths should be about 3 to 5 times the 170ºF number. If you over-estimate the correct values, you WILL flood the engine. Note that even in a 'piggy-back' application, do not set MegaSquirt's cranking pulse widths to zero. This will cause unpredictable pulse widths up to 13 milliseconds. Instead, set them to 0.1 milliseconds in that application. This allows very little fuel to flow.

- Afterstart Enrichment: If the engine tries to start, but dies right away, you need to adjust the after start enrichment. Generally this should be between 25-45% for 100 to 250 cycles,

- Warmup Enrichment: If the engine starts but dies after a several seconds or minutes, then you need to adjust your warm-up enrichment. Use up to 15% greater than the defaults if that seems to help.

- VE Table: Adjust the values at the idle kPa and rpm to get it to idle. You want to change the VE table entries while watching the engine MAP (in kPa) to try and lower the MAP as much as possible. Do this after the engine has warmed up. As you do this, the engine rpm will rise, and you may have to adjust the throttle stop on the throttle body to lower the rpm back to the desired idle speed. Once the idle VE are tuned, you will have to retune the afterstart and warmup enrichments.

If you have been trying to start your engine for more than 15 to 20 minutes, you ought to investigate other sources of problems before continuing to try to start the engine. ...

This is here: http://www.megamanual.com/ms2/tune.htm#howto

I have removed all the references to changing the req_fuel - people found this confusing, and it wasn't helping to explain the process (it was an artefact from the original version of the manual dating back several years).

Just FYI, longer pulse widths always mean more fuel, there's lots more info here: http://www.megamanual.com/v22manual/mfuel.htm

And yes, if the engine dies when you closed the throttle, you need to adjust the throttle stop to keep it open, so the engine will continue to run.

Lance.

[conn110]

Thanks Lance. Yes, the Req-Fuel was throwing me. I started to wonder about that throttle body. I had assumed it would automatically allow in the minimum required air. Oops!

Once the TB is adjusted to the point of starting, should I make that new position 0% throttle for TPS calibration?

[Bernard Fife]

Once the TB is adjusted to the point of starting, should I make that new position 0% throttle for TPS calibration?

conn110,

Yes, definitely. Anytime you change the throttle stop, you should recalibrate the TPS.

Lance.