I swapped my 440's out with 600's and for the first time I've got a mild case of warm startup sputtering..5 or 6 cranks and a little gas tapping instead of the usual stock-like 2. Does anyone have experience with eliminating warm start issues with uprev+DW 600's (with fuel return)? I played with the cranking enrichment but it didn't do much -- any tips are welcome

 

bump for answers...i hate hot starts

 

did you adjust all your k multiplier and injector scaling?

Try removing fuel from the cranking enrichment. Warm starts usually are too much fuel and since you went up in injector size it would also be pouring too much fuel in.

 

Reducing the cranking enrichment worked for me too.


Jeff, did you get my email last week?

 

Good point. Also in you cranking enrichment you will need to adjust the values down. I had the same issue when the car was warm. Below is what I used for cranking enrichment. It helped lots. I would take more out in the 140 to 176 range to.



=

 

i thought i replied to it. let me check again.

 

Yes I adjusted the K accordingly, everything is stoich and it drives perfectly. Electrically there is no diff. between the DW 440's and 600's so no adjustment was needed on the latency, but I did double check to make sure it was correct..

I multiplied all the startup values by 0.8 and it still sputters on warm starts. How much are you guys usually pulling there? I guess if compared to stock I should be almost halving some of the values, maybe more?

 

Weird, i would think they would be different. I went up to 800's from 440's so it changed quite a bit.

My warm engine coolant temps i had pulled way back to get it to hot start ok. Just keep pulling fuel. Mine was single digits.

 

Thanks, I figured as much. I'll keep pulling the fuel and update the thread with details if/when I get it dialed in.

I was also surprised to learn the 440's and 600's are the same latencies. Both have a dead time of about 1.2-1.3ms. I did end up lowering the dead time from 1.3 to 1.2 to get the K to scale down properly... the K value, even set to 0, won't pull enough fuel if you have too much dead time.. 0.1ms change made a big diff...

The interesting part before I lowered the dead time to bring K settings back to life... was even though K wouldn't pull fuel, I could still pull fuel in the comp table. For a while both my mechanic and I thought the K setting was completely broken...

 

So if I have 600cc DW injector and I play with the cranking enrichment enough I can eliminate my hot start issues totally and have a normal start again?

 

If you have a fuel return set up and 600cc injectors i usually will set base fuel pressure at 38lbs static and mess with the cranking enrichment values. However i have had some Gen2 ecus that no matter what i do it has slightly longer hot crank then cold.....

 

Hmm... I wonder if the dead time has a similar affect on the Cranking Enrichment as it does on K (as in, working vs not working at all). I'll be sure to rule this out if I keep having issues.

 

It can help, not cure

 

Alright, I don't really mind a slightly extended crank 4-6 instead of 2-3 i just don't want to have it not start at all unless I hold the throttle to the floor to clear flood mode to have it start.

 

It fires up like a champ now... had to put the enrichment in the mid teens for the warmer temps, and took about 30% off the colder temps. Thanks for the assist guys.

 

np, glad it's working good

 

Glad to here you got it working.

 

wow nice info guys. no to thread jack...

I thought the exact opposite. Im running stock injectors but mild s7 cams.

I thought the reason why I had to give it gas for it to finally start was because it needed more fuel. but from that you all are saying is that it is the other way around. I will definitely try it out.

 

I doubt your issue is fuel related... if anything I would think you would be going a little lean with the extra lift.

More than likely you will need to mess with other parameters such as cranking timing, which is a whole other can of worms.

Either way let me know how it goes.

 

You're right, it is lean. You installed a higher flowing cam and have tiny stock injectors. Increase the cranking enrichment. For a first try make a wild change (increase it a lot) and see what that does. If it still has a problem then only increase it half of what you did hte first time and try again. After that you can start fine tuning it with small numbers. If you start fine tuning with small numbers you'll be tuning forever.