Cold Start tips.

[horsewidower]

My car has been a cold blooded bitch since we put it together. We almost always have to use starter fluid to get it going. Once it has heat, it'll start fine. I tried playing with the primer map this morning, but no joy. It has 10* of advance at start up. Any hints??

Bob

[dieselgeek]

Re: Cold Start tips.

My car has been a cold blooded bitch since we put it together. We almost always have to use starter fluid to get it going. Once it has heat, it'll start fine. I tried playing with the primer map this morning, but no joy. It has 10* of advance at start up. Any hints??

Bob

10* of advance should be fine, but you want to confirm that's what it's actually doing. Watch a timing light and make sure you have good ignition when cranking.

SEcond thing is to figure out exactly how much fuel is going in during cranking. A good rule of thumb is, for a warm start, 1.0 - 1.5 x warm idle fuel quantity. To know this accurately, you have to know that your injectors are squirting the same number of times per rev when cranking, as when running. On a megasquirt, all injectors fire for every tach pulse, so it's easy to flood it with a big fuel number.

or maybe try this: get it warmed up, and then shut it off. Crank it with no throttle and see if it starts. Keep reducing fuel and restarting it until you find the lower threshold of where it won't start. Just above that should be your warm cranking pulsewidth.

For cold starting (which is what, like 65 degrees out there? lol), maybe double that number at most.

-scott

[horsewidower]

Re: Cold Start tips.

Yeah, wish it was 65. In the garage, the IAT said that it was 51*. Couldn't get it to start tonight, pissed me off. Even with the starter fluid.

I still have things to work out. Damn it.

[dieselgeek]

Re: Cold Start tips.

got a datalog of it cranking?

something I forgot to mention but that can be a comon problem on VR-sensor crank trigger ignitions: sensor spacing can cause low RPMs not to trigger. If it doesn't fire right away on the fluid, then UI'm pretty sure you're having ignition problems...

does your laptop software display RPM steadily when cranking, or is it bouncing/erratic? a datalog will show this better.

[horsewidower]

Re: Cold Start tips.

Its bouncing, I think you're right, I need to move the VR closer.

Sometimes I get no spark at all and I have to reboot the computer.

Bob

[dieselgeek]

Re: Cold Start tips.

Its bouncing, I think you're right, I need to move the VR closer.

Sometimes I get no spark at all and I have to reboot the computer.

Bob

yeah, that's for sure going to be a VR position thing. the bitch of it is, if you get it too close it'll start fine, but then it'll lose tach at high RPMs. Sensor spacing is going to be critical on your system, which probably doesn't have adjustable impedance...

[horsewidower]

Re: Cold Start tips.

I've got gain controls...??

[dieselgeek]

Re: Cold Start tips.

I've got gain controls...??

is that a question? or a statement?

[BBR]

Re: Cold Start tips.

I've got gain controls...??

is that a question? or a statement?

It's a questment.... or is it a Sta-stion.?

[horsewidower]

Re: Cold Start tips.

Let me restate.

I have gain controls.


???

[horsewidower]

Re: Cold Start tips.

Talked to the local dyno operator, we should be back there next week. I have to fix this cold start problem, otherwise the car just sits until I get there after work and get it going.

[dieselgeek]

Re: Cold Start tips.

IF the gain controls let you "turn up" the gain, try that, otherwise, I'd just put the VR sensor closer to the trigger wheel. Make sure you can free rev without losing tach signal though.

[horsewidower]

Re: Cold Start tips.

IF the gain controls let you "turn up" the gain, try that, otherwise, I'd just put the VR sensor closer to the trigger wheel. Make sure you can free rev without losing tach signal though.

I'll get under there and adjust the gap before i do anything. Do you have a suggested gap size?

[dieselgeek]

Re: Cold Start tips.

most VR sensors want .030" - .060"

[horsewidower]

Re: Cold Start tips.

That helped a lot!!!

Now I'll just play with the primer map and the cold engine coolant map to see if I can get it up to par.