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Hot restart issues

 
Old 04-29-2019, 08:23 PM
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Default Hot restart issues

I know, not a new issue for a novice user to have but I was hoping someone could point me in the right direction. I've been struggling with this for awhile now and I've been reading and watching the how-to video on this page. I think I've made decent progress but the hot starts have me baffled. I know it's just my lack of understanding all the nuances of tuning but I'm doing my best to learn as much as I can. Right now my cold start is good. The car warms up fine and idles good when warmed up. Car runs well and the AFRs seem good. It's the hot restarts that are giving me fits. The car just stumbles and doesn't start unless I get on the gas. Now the fact I need to give the car gas should be a clue but I've adjusted the ASE and ASE Taper with no success. Some background on the car. 97, stock motor with an MS3 Pro pnp from DIYAutotune. I have deleted the MAF and installed a GM IAT. Recently I installed Flow Force 640cc injectors and a DW200 fuel pump, adjusted the Req fuel and dead times. I am taking these steps to eventually install a BRP MP62 which I already have. I've included my current tune. Appreciate any advice.
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Old 04-29-2019, 09:40 PM
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Post a log. Preferably 2 logs. One with a good start cold and one with a bad start hot (no throttle).

1st thing I whould do is multiply all of your MAT correction curve by 0.855 (1/1.17) and all of your VE table [and idle VE table] by 1.17. That way you are proper referencing a more normal air temperature while tuning, and the curve makes sense to other looking in. That is not your problem, just a little something that needs cleanup.
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Old 04-30-2019, 07:46 PM
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Originally Posted by DNMakinson View Post
Post a log. Preferably 2 logs. One with a good start cold and one with a bad start hot (no throttle).
Here you go. It was about 50F in my garage. The cold start log is the car idling up to temp (about 190F). The hot start log is about 20 minutes later. You'll see the initial start fail. The second try it catches, and eventually evens out. It actually started better than yesterday but it's cooler out tonight. I physically felt the IAT and it was not as hot as yesterday. Probably because I didn't drive the car and just idled up to temp parked.

Cold start log was too big so it's on my server at work. Just grab it from the URL below. Thanks.
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Old 05-01-2019, 12:00 PM
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Items you have that are contributing to your issue:
  • As I mentioned in post #2, you need to adjust your MAT correction and VE tables so the MAT makes sense. Then, if you want to combat a FALSE MAT reading at a hot restart, Ignore MAT will ADD fuel, not pull it.
  • Advance in idle area (you are not using Idle Advance) swing 10* from 25 to 40kPa. That, with your idle advance correction, is giving 15* swings. This is causing the up and down.
  • Your MAT corrections, as mentioned before, are all above 100%. Then you have chosen to Ignore MAT during ASE, which means you are pulling 17%+ fuel during ASE due to that setting.
  • I don't think you have calibrated WUE. There is a wizzard for that. At cold, you are really rich; at least in terms of 12.5 AFR. Maybe NA's need that, IDK.
  • Use the re-scale function to create Ignition Table bins similar to the ones in your VE table. In anticipation of Boost. Unless you just want a straight linear from 150 to 200 kPa.
  • Turn on EGO at lower CLT. I use 70*
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Old 05-01-2019, 02:12 PM
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Originally Posted by DNMakinson View Post
Items you have that are contributing to your issue:
  • As I mentioned in post #2, you need to adjust your MAT correction and VE tables so the MAT makes sense. Then, if you want to combat a FALSE MAT reading at a hot restart, Ignore MAT will ADD fuel, not pull it.
  • Advance in idle area (you are not using Idle Advance) swing 10* from 25 to 40kPa. That, with your idle advance correction, is giving 15* swings. This is causing the up and down.
  • Your MAT corrections, as mentioned before, are all above 100%. Then you have chosen to Ignore MAT during ASE, which means you are pulling 17%+ fuel during ASE due to that setting.
  • I don't think you have calibrated WUE. There is a wizzard for that. At cold, you are really rich; at least in terms of 12.5 AFR. Maybe NA's need that, IDK.
  • Use the re-scale function to create Ignition Table bins similar to the ones in your VE table. In anticipation of Boost. Unless you just want a straight linear from 150 to 200 kPa.
  • Turn on EGO at lower CLT. I use 70*
Thanks for the advice. I hope I can get some time this weekend and try to clean things up. I didn't make the changes yet that you pointed out in message #2 since I didn't want to make changes and have the tune different than what I posted. I suppose I could have re-posted the tune but just wanted to maintain the baseline for the thread. Question on that... I can see why my MAT correction would need adjustment. I was playing around with that and it's messy at the moment but I don't understand multiplying the VE table by 1.17. Do you mean all the fields or just the X, Y axis and then reinterpolate?
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Old 05-01-2019, 02:50 PM
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Look at the fueling equation. It includes MAT Correction and VE as multipliers (along with MAP, and a few other items).

If you divide all MAT corrections by 1.17 and do nothing else, then immediately every fueling point (save Crank and Priming pulses) will be lean. To keep you where you have already tuned, the VE must be increased by the inverse of the amount MAT is decreased.

That is true except during ASE, where you would then be richer than you have been.

I suggest you fix that issue by turning off the "Ignore MAT during ASE". Use that as a last resort later if you need to.

Best of Luck

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Old 05-01-2019, 03:57 PM
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Originally Posted by DNMakinson View Post
Look at the fueling equation. It includes MAT Correction and VE as multipliers (along with MAP, and a few other items).

If you divide all MAT corrections by 1.17 and do nothing else, then immediately every fueling point (save Crank and Priming pulses) will be lean. To keep you where you have already tuned, the VE must be increased by the inverse of the amount MAT is decreased.

That is true except during ASE, where you would then be richer than you have been.

I suggest you fix that issue by turning off the "Ignore MAT during ASE". Use that as a last resort later if you need to.

Best of Luck

DNM
Ok, I see now. Thanks for you patience and advise.
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Old 05-03-2019, 02:22 PM
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Since I have just begun messing with the MAT correction would it be a better strategy for me to just set the fields all to 100 so it's not doing anything, work out the other issues that where pointed out and then start adjusingt the MAT as needed ?
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Old 05-03-2019, 02:56 PM
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If you wish. Still have to compensate for the change in the correction that MAT is presently giving. I would still suggest doing so in the VE tables.

The shape of your MAT table is not bad, however. It is just all one-sided. If you zero it, then tune VE some in the morning at 70*, and then some at afternoon at 85*, you will fight yourself; showing rich in the evening, lean in the morning. As long as you tune VE while running at the same MAT temps, and then later tune the MAP table, no worries. Just realize the interactions of the various components of the tune.
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Old 05-03-2019, 03:06 PM
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Originally Posted by DNMakinson View Post
Just realize the interactions of the various components of the tune.
Thanks again. You hit the nail on the head here. My inexperience with the interaction of all the different settings has probably been the biggest challenge for me.
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Old 05-03-2019, 08:51 PM
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DNM,

Sir, you have always provided sage advice here. Can you tell us why there isn't a universally approved MAT correction curve?
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Old 05-04-2019, 09:23 AM
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I think, like many things, there can be general rules of thumb, but every installation is unique. Also, I can say what approach I took to tuning MAT CORR (MC) and what results I got and use, but have no other tunes / results to compare against.

Theoretically, the correction should match the ideal gas law. In that case, the corrections at Tnow from Tbase are (Tbas+460)/(Tnow+460): Tnow = the temp under review, and Tbase being the 100% CORR temperature. For less confusion in tuning (as I mentioned above) Tbase should be around your typically experienced value. For me that is 70F.

How should that be applied. Well, to be valid: 1) The measured temp should be the actual air temp; 2) the temp must be measured at the same location that the MAP sensor is measuring the pressure.
Meeting (1) is difficult under certain circumstances due to what is known as Heat Soak. Meeting (2) is related to (1). Ideally you would want the MAT sensor to be in the intake manifold. However, the pick-up of heat from the IM into the sensor has been known to give false readings. So, to combat those things, on a Turbo car, the consensus it to place the sensor on the outlet of the FMIC. There, it is shielded from the engine heat and gets a good read on the air temp just before the throttle.

What is the negative of this? It is before the Throttle, and therefore will not take into account, under most circumstances, for air temperature drop due to throttling, so that it is not seeing the temp of the air as it the temp where the MAP sensor is reading absolute pressure.

So: When I tuned my MC, I did not use data when my throttle was opened less than 40%. The goal was to have the measured air temp be very close to the air temp within the IM. The implications are that the MC are valid for MAP of about 80kPa and above, but not correct for cruise. For me that is what we want. We want very little EGO correction in boost, and more EGO correction available for lower kPa. That is what we end up with. When I tuned MC at cruise, I would go rich as my MAT increased with long, hard pulls. I pulled fuel in the upper right of the VE table. Then in cold weather, I would go lean up there. That is why I suggest tuning MAT corrections up top.

Maybe people don't care, because they want richer AFR when MAT is higher? I guess that would help with detonation? IDK. I'm just giving my philosophy, which is to not need EGO to hit my prescribed AFR table values.

My resultant table was not the full Ideal Gas Law corrections. About 5% less in each direction.

Some people, to combat Hot Restart issues, flatten the top of the curve. However, realize that is only a true fix for that one condition, when MAT sensor is really heat soaked. By that, I'm not saying it does not work, even if the sensor is not heat soaked, only that it is a fix that is compensating for another issue, rather than correcting for the actual issue. By placing the MAT sensor on the FMIC, away from radiator and engine heat, one should find little true heat soak of said sensor. I believe the writer of the TS manual called it "perceived heat soak". Also, I hesitate to compromise 99% of running time tuning to fix a problem that occurs for 1 minute of run time, at a non-critical time. Afterstart vs running in boost.

That all being said, here is my table:


The ideal gas law would put the 15*F correction at 111, where I am at 108. (the 0* is prediction, and I have never run the car that cold). Note that my Tbase is 70*, where I am at 100%.
The ideal gas law would put the 140*F correction at 88, where I am at 92.
So, I'm lower correction at both extremes, but far from flat.

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Old 05-04-2019, 10:37 AM
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Regarding warmup AFR, there's a really cool table hidden in VEAL menu, under WUE, advanced settings. It's a curve to keep AFRs lower during warmup rather than targeting your warm running ~14.7 AFR. Personally I think a car starts really well with a few seconds of 11.0, and then warm up around 12.5 until ~140 coolant, then tapering from 13.5 to 14.5ish hot.
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Old 05-04-2019, 11:37 AM
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Originally Posted by curly View Post
Regarding warmup AFR, there's a really cool table hidden in VEAL menu, under WUE, advanced settings. It's a curve to keep AFRs lower during warmup rather than targeting your warm running ~14.7 AFR. Personally I think a car starts really well with a few seconds of 11.0, and then warm up around 12.5 until ~140 coolant, then tapering from 13.5 to 14.5ish hot.
OK. That is cool, and great to know. I have personally been happy with 14.7 after ASE, except for 1st drive off, things go lean, and I have not been able to combat that with EAE, as it lasts about 3 seconds. More related to time after start than absolute CLT. Still, this could help. I understand that often OEM's runs richer (not just extra WUE) during warm-up. BBro may be interested in this as well.

PosCat given.
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Old 05-04-2019, 11:59 AM
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Sir,

Thanks much.

The way I understand it, if I had no MAT correction--100% across the board--and I tuned her at 80 degrees, I should be lean when it's 40 degrees out, and rich when the car is fully warmed up and under boost, MAT 105ish. (My new Vibrant intercooler is amazingly efficient).

My problem is the values in the idle boxes of the VE Table that give me high 12s on a cold morning start give me 16s on a hot restart on a hot day. I have "Ignore MAT Correction at Startup" ON, and I need a very large number for the ASE Taper on a hot restart so that the MAT Correction for temps under boost (as you stated) doesn't pull fuel at idle, and I have it flat 100% at colder temps so it doesn't add even more fuel when cold. I read a post that explained when using some of the new large injectors on a small motor, the electrical properties of the injectors can be different enough at 40 degrees vice 200+ and that's what's happening to the AFR, not heat soak of the MAT sensor. Unfortunately, I can't find the post.
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Old 05-04-2019, 12:10 PM
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Originally Posted by curly View Post
Regarding warmup AFR, there's a really cool table hidden in VEAL menu, under WUE, advanced settings. It's a curve to keep AFRs lower during warmup rather than targeting your warm running ~14.7 AFR. Personally I think a car starts really well with a few seconds of 11.0, and then warm up around 12.5 until ~140 coolant, then tapering from 13.5 to 14.5ish hot.
Poscat given, as well.

I have never seen, let alone touched that table. I found the explanation for this in the manual. However, I still have questions. If WUE is zero (100%) at high temps, does this table do anything? Does it do anything outside of WUE Analyze?

From the manual:
AFR Temperature Adjustment to Lambda - For most less radical engines targeting your standard stoich AFR is desireable. However, for various reasons you may want the engine to run more or less rich during warmup. Adjusting this curve allows you to raise or lower the target AFR during warmup. By Adjusting the curve down, the target AFR for that temperature will be lowered. For example if your target AFR at 32 degrees is 14.7:1 under normal condition and this table is set at -0.5, WUE Analyze will use 14.2:1 as the target AFR.

Have you made adjustments to yours?

Thanks!

Last edited by poormxdad; 05-04-2019 at 01:08 PM.
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Old 05-04-2019, 01:21 PM
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Originally Posted by DNMakinson View Post
Items you have that are contributing to your issue:
  • As I mentioned in post #2, you need to adjust your MAT correction and VE tables so the MAT makes sense. Then, if you want to combat a FALSE MAT reading at a hot restart, Ignore MAT will ADD fuel, not pull it.
  • Advance in idle area (you are not using Idle Advance) swing 10* from 25 to 40kPa. That, with your idle advance correction, is giving 15* swings. This is causing the up and down.
  • Your MAT corrections, as mentioned before, are all above 100%. Then you have chosen to Ignore MAT during ASE, which means you are pulling 17%+ fuel during ASE due to that setting.
  • I don't think you have calibrated WUE. There is a wizard for that. At cold, you are really rich; at least in terms of 12.5 AFR. Maybe NA's need that, IDK.
  • Use the re-scale function to create Ignition Table bins similar to the ones in your VE table. In anticipation of Boost. Unless you just want a straight linear from 150 to 200 kPa.
  • Turn on EGO at lower CLT. I use 70*
Working on this today. I am confused by the idle advance settings. If the idle advance is off (which it is) then I am not understanding what is causing the idle correction giving the large 15* swing. Been reading and searching online but so much of what's out there is out of date or unresolved threads.
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Old 05-04-2019, 05:24 PM
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I did look again. When the 15* swing occurred, it was after the engine almost died and went out of CLI. At about 25 seconds on you Hot Restart Log. Otherwise, the swing is about 10 degrees, which is the sum of the engine going from 900 RPM at 40 kPa and 1200RPM at 30kPa. That is a 6* swing. Sorry to have misled.

curly I presume that is just to have targets set to accentuate the creation of the WUE curve. After the fact, if EGO is on, would it not over-ride the offsets that were used, and drive the fueling back to the AFR Targets? Thinking it is this way as it is a VEAL functionality.
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Old 05-05-2019, 08:28 AM
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Originally Posted by DNMakinson View Post
I did look again. When the 15* swing occurred, it was after the engine almost died and went out of CLI. At about 25 seconds on you Hot Restart Log. Otherwise, the swing is about 10 degrees, which is the sum of the engine going from 900 RPM at 40 kPa and 1200RPM at 30kPa. That is a 6* swing. Sorry to have misled.

curly I presume that is just to have targets set to accentuate the creation of the WUE curve. After the fact, if EGO is on, would it not over-ride the offsets that were used, and drive the fueling back to the AFR Targets? Thinking it is this way as it is a VEAL functionality.
No worries at all. I'm just trying to understand things correctly and appreciate the help.
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Old 05-05-2019, 11:32 AM
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Originally Posted by poormxdad View Post
Have you made adjustments to yours?
Yes, I target 14.5 at warm idle, I'm not in front of my tuning laptop right now, but my curve would roughly be -2.0 at less than 100 degrees. I'm also 100% ok with seeing afrs in the 10s very briefly if I start driving when cold. A lot of people freak out at the numbers on the gauge vs. how the car behaves I've found. I'm glad OEM's have found a way to warm up, let you drive immediately, never go below ~13 afr, and have zero hot restart issues, I haven't figured out the magic combo to do all of that.

My key is mid to low 12s during warm up, long ASE taper at higher temps, and an exponential growth looking AE curve.
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