Hot restart issues
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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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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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Originally Posted by DNMakinson
(Post 1533046)
Post a log. Preferably 2 logs. One with a good start cold and one with a bad start hot (no throttle).
Cold start log was too big so it's on my server at work. Just grab it from the URL below. Thanks. cold start log |
Items you have that are contributing to your issue:
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Originally Posted by DNMakinson
(Post 1533229)
Items you have that are contributing to your issue:
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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 DNM |
Originally Posted by DNMakinson
(Post 1533244)
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 |
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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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. |
Originally Posted by DNMakinson
(Post 1533512)
Just realize the interactions of the various components of the tune.
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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? |
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: https://cimg8.ibsrv.net/gimg/www.mia...aefb39984f.png 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. DNM |
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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Originally Posted by curly
(Post 1533609)
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. |
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. |
Originally Posted by curly
(Post 1533609)
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.
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! |
Originally Posted by DNMakinson
(Post 1533229)
Items you have that are contributing to your issue:
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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. |
Originally Posted by DNMakinson
(Post 1533648)
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. |
Originally Posted by poormxdad
(Post 1533624)
Have you made adjustments to yours?
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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