Megasquirt Help!

TheYac

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May 22, 2021
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Hi all. I have a 1986 GT Convertible that I put a On3 Turbo kit into. Had the car Dynotuned and got her running awesome when you are above 2000 RPM. I'm have trouble with her running between 1100 and 2300 rpm. It sputters and wants to stall....even under load, 5th gear 50 mph 1900 rpm you can hear the engine sputter and its just not happy...above 2500 this car is an absolute beast. I know its just getting in and tuning this end part (something the dyno guy really doesn't mess with-hes more concerned about the upper end power band)
I will include a few of my Tuner studio files. I replicated the problem a few times while in the data log. I hope I did it right so i can get this sorted out. just to be more thorough. Stopped for gas, tried to leave the station (temp 185*, everything looking good) I have to struggle to keep the car from stalling....bring it up to 3K then let off the clutch to get her rolling without stalling... get up to 2400....car is a gem to drive....
My reason for asking for help is, I think the Idle control valve settings and some timing/fuel setting need to be adjusted-but to be honest, I'm new to this and frankly out of my lane.
Thanks in advance!!
 

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a91what

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uhh are you sure? I see some glaring issues that a tuner should have fixed before starting the tune. Is this an ms2pnp or a microsquirt?
The ignition table is scaled for an NA engine, it stops at 100kpa and 33* of timing.. boost is anything above 100kpa. Basically its either running 33* in boost [not likely or it would be parts scattered on the ground] or the timing is not properly synced.

Based on the ignition settings it is an MS2pnp

I would need a datalog of the issue, but Im convinced that you will need quite a few things fixed.
I think you also have a scaling issue on the map sensor
 

TheYac

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May 22, 2021
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uhh are you sure? I see some glaring issues that a tuner should have fixed before starting the tune. Is this an ms2pnp or a microsquirt?
The ignition table is scaled for an NA engine, it stops at 100kpa and 33* of timing.. boost is anything above 100kpa. Basically its either running 33* in boost [not likely or it would be parts scattered on the ground] or the timing is not properly synced.

Based on the ignition settings it is an MS2pnp

I would need a datalog of the issue, but Im convinced that you will need quite a few things fixed.
I think you also have a scaling issue on the map sensor
 

TheYac

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May 22, 2021
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Truthfully I was praying you were the guy to reply... yes is an Ms2pnp. ... I might have included the file prior to his tuning. I apologize... you’re dealing with a rookie. I can slap the cpu on this tomorrow and do a whole new file and get you totally accurate information. Again I really don’t want to waste your time, but i know a few adjustments will make this awesome. I’m going to attach the best “hit” on the dyno. He dialed it down not wanting to put to much stress on the block. The numbers changed minuscule but 500ft/lbs at the block is dangerous for a stock set up... we made 405 at the wheels...
 

a91what

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That is respectable numbers.
Drivability is the hard part.. with a turbo you just set the timing safe tune in the fuel and let boost make the power.
 

TheYac

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That is respectable numbers.
Drivability is the hard part.. with a turbo you just set the timing safe tune in the fuel and let boost make the power.
I hope I attached the correct file.....I just took the car out and drove it around and replicated the problem several times. My AFR is WAY low at low rpm and low kPa loads. Put the car in 5th gear at 40 mph about 1400 rpm light pressure on the accelerator and the AFR is showing 17 on the gauge. Is it starving for fuel at this low RPM.....I tried to put a little more fuel into it but I don't want to do too much.....I hope this is the right file.....The ones I posted were totally the wrong ones.
 

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stanglx2002

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Its hard to answer the question when you don't have a datalog of the event happening. Could you please attach a datalog of it happening to help further.
 

a91what

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I hate to tell you this but the tune was setup in a way that does not work for closed loop fuel control.. it will take a few tries to get right but once done will be correct.

The timing table is a real mess, this needs to be fixed in a bad way. the lack of timing advance in the cruise rpm range is not helping with drivability.
I have taken the liberty to alter the tune file quite a bit, please do not do any wot pulls until I can see how much the changes affect the final fueling from a normal driving log.
I did not alter the timing table as it will affect the idle, this is easily fixable but takes time to do.
Closed loop idle will work once the valve settings are set correctly.. some of them are rejected values used to populate an entry that was not filled in during setup..

The tune is so fat through 2800-3500 rpm that im surprised you have not lifted a ring land yet. at the same time its so lean coming up into boost you are lucky you havent popped a gasket yet.

I can help you fix it but it will take some doing. DO NOT do anymore wot pulls until we get that cleaned up.
 

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TheYac

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I hate to tell you this but the tune was setup in a way that does not work for closed loop fuel control.. it will take a few tries to get right but once done will be correct.

The timing table is a real mess, this needs to be fixed in a bad way. the lack of timing advance in the cruise rpm range is not helping with drivability.
I have taken the liberty to alter the tune file quite a bit, please do not do any wot pulls until I can see how much the changes affect the final fueling from a normal driving log.
I did not alter the timing table as it will affect the idle, this is easily fixable but takes time to do.
Closed loop idle will work once the valve settings are set correctly.. some of them are rejected values used to populate an entry that was not filled in during setup..

The tune is so fat through 2800-3500 rpm that im surprised you have not lifted a ring land yet. at the same time its so lean coming up into boost you are lucky you havent popped a gasket yet.

I can help you fix it but it will take some doing. DO NOT do anymore wot pulls until we get that cleaned up.
Ok, I will try to get this into the computer later today....Thank you for helping. I'll contact you later....
 

TheYac

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May 22, 2021
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Morning drive to work. Then the drive home. Stopped for gas and left it idling. At that stop sign and the one a few minutes later it wanted to stall. it did smooth out nicely in the 12-2000 RPM range. I tried to keep it down there. Never went over 2/3 Throttle. We're definitely heading in the right direction....
 

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TheYac

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May 22, 2021
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Morning drive to work. Then the drive home. Stopped for gas and left it idling. At that stop sign and the one a few minutes later it wanted to stall. it did smooth out nicely in the 12-2000 RPM range. I tried to keep it down there. Never went over 2/3 Throttle. We're definitely heading in the right direction....
 

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a91what

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Are you doing any kind of autotuning during the log file? Quite a bit of fuel trim needs to be done at idle, you will likely need to replace the plugs. If you are not autotuning then I can do a fuel trim from my side
 

TheYac

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May 22, 2021
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Are you doing any kind of autotuning during the log file? Quite a bit of fuel trim needs to be done at idle, you will likely need to replace the plugs. If you are not autotuning then I can do a fuel trim from my side
No I’m not using auto tune ... I have a new set of plugs ready to go, but I’d figure I’d wait till it’s closer to being tuned in that low RPM so I don’t trash another set.
 

a91what

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This time I gutted your timing table and built you a real one.. I also scaled the tables for a street car.

again please datalog so I can see how the changes affect the idle and cruise ect. Keep in mind that I had to make some pretty drastic changes and anytime you deal with values above a 15% change in a single step the end error tends to be skewed.
 

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