Miata.lean hot restart

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Miata.lean hot restart

Postby nismoautoxr » Wed Nov 15, 2017 7:48 pm

This is a 97 miata witg an 02 vvt engine, 650cc diyat highz injectors and a t3 intercooled turbo. I do not have a log of it right now but here is what happens. If it sits for about 15 minutes after a normal drive.....it is extremely lean on the restart to the point that it might stall out after starting it unless I rev it a few times. I dont feel that its mat correction because I set everything above 70degrees to 100 so it shouldnt be correcting for mat at all so why on earth is it lean on hot restarts? Im going to get a log but so far I havent caught it but it is like 17 to 1 untill it runs a couple minutes. Is anyone else having this problem?
Ricky-
1995 Nissan 240sx, 403 LS strokerv8 N/A 6speed trans
MS3&MS3X v.3.0 PCB
42lb/hr Hi-Z inj.,230/232 @.050 on 114LSA cam
sequential fuel and sequential spark
LS3/LSA card MAF sensor
97 Mazda MX5
MS3 2002 vvt motor
.60 trim T4 Turbo at 15 PSI
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Re: Miata.lean hot restart

Postby MegaMicra » Fri Nov 17, 2017 3:23 pm

Can you not set the after start enrichment to cover this lean period. That's all I do.

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Re: Miata.lean hot restart

Postby NigeT » Fri Nov 17, 2017 4:55 pm

I have very similar issues with my NA8 MX-5. Once bit it goes lean shortly after engine start, maybe ager my ASE has tapered off.

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Re: Miata.lean hot restart

Postby nismoautoxr » Mon Nov 20, 2017 7:17 pm

MegaMicra wrote:Can you not set the after start enrichment to cover this lean period. That's all I do.

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Yes I can but the amount of afterstart enrichment and the taper time needed is a moving target ....i.e. dependant on the amount of time it sits before the restart. Sometimes its appropriate and sometimes its too much for too long, if that makes sense.
Im confident that its not an iat placement problem. The iat is in the cold side intercooler pipe about 4 inches prior to the trhottle body. Its a gm open element sensor. Besides that....I went into the tune and set everything above 70 F to 100% on the air density correction so it should be removed from the equation. I dunno wth is going on . Idk if the fuel is getting hot in the rail ....has some intermittent pressure issue....some goofy injector issue...idk. No other evident problems outside of that are going on while driving it.
I used to have a similar problem with my 240 sx back when it had a microsquirt module in it but all that went away when I put the ms3 in it. The LS2 engine didnt hurt either lol. I digress. Its embarrassing and irritating to try and leave somewhere and the car start and stall 2 times and surge at idle for amcouple minutes. I just wanna get to the bottom of tgis and fix it.
Ricky-
1995 Nissan 240sx, 403 LS strokerv8 N/A 6speed trans
MS3&MS3X v.3.0 PCB
42lb/hr Hi-Z inj.,230/232 @.050 on 114LSA cam
sequential fuel and sequential spark
LS3/LSA card MAF sensor
97 Mazda MX5
MS3 2002 vvt motor
.60 trim T4 Turbo at 15 PSI
nismoautoxr
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Re: Miata.lean hot restart

Postby MegaMicra » Mon Nov 20, 2017 7:51 pm

Could it possibly be heat soak of the inlet manifold causing the fuel to vapourise on restart. I know some of the rally guys over here use ptfe spacers between the head and manifold to stop this.

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Re: Miata.lean hot restart

Postby nismoautoxr » Mon Nov 20, 2017 7:58 pm

MegaMicra wrote:Could it possibly be heat soak of the inlet manifold causing the fuel to vapourise on restart. I know some of the rally guys over here use ptfe spacers between the head and manifold to stop this.

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I suppose it could. Its all stock stuff aside from the higher flow injectors and the turbocharger. I just street drive the car to work and around town and stuff. Im not sure exactly how to conclude if that is the cause. Ill have to think on that.
Ricky-
1995 Nissan 240sx, 403 LS strokerv8 N/A 6speed trans
MS3&MS3X v.3.0 PCB
42lb/hr Hi-Z inj.,230/232 @.050 on 114LSA cam
sequential fuel and sequential spark
LS3/LSA card MAF sensor
97 Mazda MX5
MS3 2002 vvt motor
.60 trim T4 Turbo at 15 PSI
nismoautoxr
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Posts: 2613
Joined: Sun May 29, 2011 10:28 am
Location: birmingham ,Alabama. U.S.A.

Re: Miata.lean hot restart

Postby arran » Wed Nov 22, 2017 7:25 pm

Have you not deliberately created this issue by levelling out the MAT correction? The configuration you have implemented is going to cause the behaviour you are seeing.

My experience with the default curve is that it is too aggressive even though it is setup to model gas law. In reality it had a leaning impact on fuelling on a hot day in my part of the world.

If I was you I would try reinstating the did fault curve but halve all the values so the S is much flatter
RX7 Series 2 13B Turbo. Megasquirt 3 with 3X Expander and V3 CPU. Firmware 1.4.1
Knock module, twin EGT, real time clock, WBO2, full sequential fuel and spark
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Re: Miata.lean hot restart

Postby nismoautoxr » Wed Nov 22, 2017 7:30 pm

arran wrote:Have you not deliberately created this issue by levelling out the MAT correction? The configuration you have implemented is going to cause the behaviour you are seeing.

My experience with the default curve is that it is too aggressive even though it is setup to model gas law. In reality it had a leaning impact on fuelling on a hot day in my part of the world.

If I was you I would try reinstating the did fault curve but halve all the values so the S is much flatter


Im not completely sure if u saw all that I posted but ive taken every bit of mat correction out of the equation by setting everything above 70*F to100%...that means any mat above 70 has no affect on the actual afr.
Ricky-
1995 Nissan 240sx, 403 LS strokerv8 N/A 6speed trans
MS3&MS3X v.3.0 PCB
42lb/hr Hi-Z inj.,230/232 @.050 on 114LSA cam
sequential fuel and sequential spark
LS3/LSA card MAF sensor
97 Mazda MX5
MS3 2002 vvt motor
.60 trim T4 Turbo at 15 PSI
nismoautoxr
Super MS/Extra'er
 
Posts: 2613
Joined: Sun May 29, 2011 10:28 am
Location: birmingham ,Alabama. U.S.A.

Re: Miata.lean hot restart

Postby arran » Thu Nov 23, 2017 4:11 am

I guess what I am saying is that the MAT correction exists for a reason. Your curve sounds like it is incorrect. This is what has been working for me:

Capture.JPG
Capture.JPG (165.59 KiB) Viewed 107 times


nismoautoxr wrote:
arran wrote:Have you not deliberately created this issue by levelling out the MAT correction? The configuration you have implemented is going to cause the behaviour you are seeing.

My experience with the default curve is that it is too aggressive even though it is setup to model gas law. In reality it had a leaning impact on fuelling on a hot day in my part of the world.

If I was you I would try reinstating the did fault curve but halve all the values so the S is much flatter


Im not completely sure if u saw all that I posted but ive taken every bit of mat correction out of the equation by setting everything above 70*F to100%...that means any mat above 70 has no affect on the actual afr.
RX7 Series 2 13B Turbo. Megasquirt 3 with 3X Expander and V3 CPU. Firmware 1.4.1
Knock module, twin EGT, real time clock, WBO2, full sequential fuel and spark
http://web.aanet.com.au/arran
arran
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Location: Brisbane Australia

Re: Miata.lean hot restart

Postby DNMakinson » Thu Nov 23, 2017 7:47 am

Extra ASE is the correct answer. That and allow EGO to be active at the idle area.

The coils of the injectors get hot, raising their resistance, and therefore decreasing magnetizing current, and therefore increasing dead time. It is a known phenomenon with many, if not all, HiZ injectors.

The range of idle AFR is great, with more tolerance toward rich than lean. Therefore, set your ASE for your worst case lean condition, and let things be rich for the short amount of time before EGO kicks in; on those occasions that the heat soaking of the injector coils does not occur.

I agree that 15-20 minutes of sitting is the worst case.

Lastly, set your ASE taper to work off Cycles, not seconds. That way ASE goes away more quickly when you rev the engine (or start moving) than when you crank and sit. You have already verified that things get better with revs, so this is the sensible approach to not maintain the extra fuel under that scenario.
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