Heat Soaked Restart Issues

[Cringer]

For cammed N/A setups is there any general guidance on heat soaked restarts? The car starts great cold and hot (after an immediate shutdown). But once you let it sit for 30 min+ it takes a lot of cranking to get going (starter is fine and engine turns over strong). I have tried more/less air, fuel, spark and nothing really helps. So I guess I'd like to know what the target EQ ratio and spark timing is ideal...you know "general guidance".

My guess is I need to experiment with the OL Injector Temp Gain ([ECM] 12442). The problem though is that the lowest temp is 176*F (80*C) which is in the range of heat soaked, but also is going to impact cold starts.

I have put a fuel pressure gauge on the rail and noted that fuel pressure spikes to 85 PSI (586 kPa) after 10 minutes of sitting with hood closed, but by the 30 minute mark is was down to 54 PSI (372 kPa). I video'd the fuel pressure gauge during start up and as soon as the motor cranks pressure rockets directly to 70 PSI (482 kPa) immediately.

[gtstorey]

Is that 70psi on both hot and cold engines?

[Cringer]

Is that 70psi on both hot and cold engines?

I didn't check it with a gauge for cold starts.

Edit: after cranking is over and the engine is running it drops to 58-60 PSI as expected btw

[gtstorey]

I would try and see if it is different pressure on hot and cold starts. Somewhere around 70-75 psi is where Alvin says that the Injectors will have trouble opening so that may be the problem.

[Cringer]

I would try and see if it is different pressure on hot and cold starts. Somewhere around 70-75 psi is where Alvin says that the Injectors will have trouble opening so that may be the problem.

Yeah but that is not the issue. If I restart at 10 min (when pressure is 85 PSI) the car starts no problem. The problem is when I continue to wait (pressure drops to normal range, but tip temp climbs) is when it has a hard time starting (it does start, just takes 2-3 seconds of cranking).

[STAGEUP]

Yeah but that is not the issue. If I restart at 10 min (when pressure is 85 PSI) the car starts no problem. The problem is when I continue to wait (pressure drops to normal range, but tip temp climbs) is when it has a hard time starting (it does start, just takes 2-3 seconds of cranking).

The dreaded injector shutdown due to overpressure. I deal with this quite a bit due to our 110-120 degree ambient temps here in Arizona during the summer. This is how I fix it. Add 20% to the area in the picture below (highlighted area). Let us know how it goes..
inj shutdown .png

[GHuggins]

The dreaded injector shutdown due to overpressure. I deal with this quite a bit due to our 110-120 degree ambient temps here in Arizona during the summer. This is how I fix it. Add 20% to the area in the picture below (highlighted area). Let us know how it goes..
inj shutdown .png

Wouldn't it be better to dial in the tip temp table? That's how I normally fix this remote tuning them. You're essentially doing the same thing, but with crnaking and initial start fuel before the alternator starts charging the way you're doing it, right?

[STAGEUP]

Correct, and yes, essentially doing the same with tip temp. Again, this is my opinion, but I prefer massaging this table as I feel it carries more weight on the issue at hand.

[GHuggins]

Im willing to try it as long as it doesn't cause other fueling issues with alternator voltage drop or heavy electrical loads

[Cringer]

The dreaded injector shutdown due to overpressure. I deal with this quite a bit due to our 110-120 degree ambient temps here in Arizona during the summer. This is how I fix it. Add 20% to the area in the picture below (highlighted area). Let us know how it goes..
inj shutdown .png

I tried this and it resulted in the worst results yet.

Again, this is not a high fuel pressure issue. This happens after pressure drops to normal and injector tip temp calculates higher.

I am still curious about:
1) Hot start EQ ratio
2) Hot start ignition advance

[STAGEUP]

Well shoot. Let me ponder.

[hjtrbo]

Fact: Cold start is good. Immediate hot restart is good. 10 min hot restart is good. 30+ min hot restart is no good. Fuel pressure fine.

Conclusion: It's directly influenced by engine off time.

What tables have an engine off time axis or are influenced by heat soak?

E.g.
FA cranking stage 1 (x axis is engine off time in seconds btw). What happens if you add 20% in the problem area?

[edcmat-l1]

Does it need MORE fuel or LESS? Have you tried WOT clear flood mode? Are we just assuming it needs MORE fuel? Have you tried just cracking the throttle?

Do you have data logs of various starts and no starts comparing throttle angle, timing, IPW, etc.?

[hjtrbo]

Does it need MORE fuel or LESS? Have you tried WOT clear flood mode? Are we just assuming it needs MORE fuel? Have you tried just cracking the throttle?

Do you have data logs of various starts and no starts comparing throttle angle, timing, IPW, etc.?

Good call,
cringer are you able to get the wideband ready for logging prior to crank? Would be interesting to see what it's doing

[Cringer]

Fact: Cold start is good. Immediate hot restart is good. 10 min hot restart is good. 30+ min hot restart is no good. Fuel pressure fine.

Conclusion: It's directly influenced by engine off time.

What tables have an engine off time axis or are influenced by heat soak?

E.g.
FA cranking stage 1 (x axis is engine off time in seconds btw). What happens if you add 20% in the problem area?

yep yep been there got the logs.

The OL tables are set up to mirror a 2012 Holden/Chevy PPV with the factor flex fuel, otherwise this car won't start on tastier blends of E.


Current Tune1.hpt
Current Tune - 35 minute heat soak.hpl
hjtrbo 20 pct more FA1.hpt
hjtrbo 20 pct more FA1 - 11 sec immediate restart.hpl
hjtrbo 20 pct more FA1 - 32 min heat soak.hpl

[Cringer]

Good call,
cringer are you able to get the wideband ready for logging prior to crank? Would be interesting to see what it's doing

Yeah I will have to crawl under the dash tomorrow to rewire it for constant power.

[edcmat-l1]

Good call,
cringer are you able to get the wideband ready for logging prior to crank? Would be interesting to see what it's doing

A wideband doesn't mean anything in a non running engine.

[hjtrbo]

Don't be a dick.

The cunt needs to warm up and be sending data before cranking ya fuck stain.

Love you Ed

[ns158sl]

I was also fighting this. Problem is I already took the wideband out now to keep refining. Ive found that it is way too much fuel. Engine is already warm, shouldn't need cold start amount of fuel. Another tell tale sign for me was it would flare like a bastard when it did take off, which made me chase my tail getting start air correct. I lowered a small amount in the OL EQ table in the range I was having issues, and also reduced the FA table by .02 until it started much better. Inj Tip temp I feel shouldn't be messed with.

[07GTS]

have u tried raising the maf s/s startup g/s for the hotter temps u only have 7.3 g/s there but ur min air and startup are almost double it so it may be using that table till the maf is good ?