5.0 microsquirt mustang hits wall around 5000 RPM

88nitrous5.0LX · Jun 25, 2019

hello all,
I'm new to the whole tuning scene and have been battling this problem for a couple weeks now. I have been asking around on the net for some help, but seems a lot of the sites are more about bashing and criticizing me for not knowing instead of helping.. One fellow i did run into that was actually trying to help recommended i ask you guys on this page..
The vehicle is..
302 stock bottom
AFR 165 heads
Holley systemax II intake
FR 30lb Injectors
bbk long tube headers
b cam
bbk 75 mm throttle body
systemax nitrous plate kit (obviously not in use yet)
On microsquirt v3

The weekend before I installed the Microsquirt I was down at the track and she pulled to 6000 RPM all night long so I have ruled out coil, distributor and TFI module. When I first put the Microsquirt in i managed to mess up the ve table and spark table pretty good and did not set the correct dead time and voltage correction for the 30s.

I have since remapped the Ve table and Spark table also set the correct parameters for my injectors... car is running overall pretty dang well all the way up to about 52-5700 RPM then its like i hit a rev limiter it backfires and shudders I just cant seem to figure this one out.. Any help or advise will be greatly appreciated. I am gonna try and attach some data logs and current tune.. thanks

a91what · Jun 25, 2019

Have you considered that it's actually hitting the rev limiter. Once I get to my PC I will see what RPM the cars breaking up at and see if theRev limiter is activating. If you are relying on the factory tack it can be a couple 100 rpm off I have seen cases where the factory tachometer is almost 500 rpm off the actual. If I'm not mistaken the base tune that comes in the micro squirt has a 6000 rpm rev limit.

88nitrous5.0LX · Jun 25, 2019

Yes sir I thought that same thing, I use an autometer tach as well.. I even went as far as turning the rev limiter off, and it still does the same thing.. sometimes at 5500 sometimes at 5700 and anywhere in between.. I have added fuel and taken away fuel, same result.. I'm definitely scratching my head lol

a91what · Jun 25, 2019

Sure enough she hits a wall, the WB goes full lean at around 5600... thats a good one.

Could be the TFI is not providing adequate spark, please run down the IGN system for me. Also I was reviewing the Tune file VS the datalog and they do not match... The two IGN tables are different.
I can see lean spikes, that tells me that the cylinders are missfiring for some reason, check the plugs.

88nitrous5.0LX · Jun 25, 2019

Yea it just seems to stop dead in her tracks.. I pulled the plugs and they look like shes burning perfect!

It is a Ford motor craft distributor with new msd cap and rotor.. definitely has some miles on the distributor and hall effect sensor.
TFI module was replaced last summer think it was autozone brand though..
Brand new Ford racing plug wires couple months on them
Same thing with the auto lite spark plugs gapped to .038
Coil also for a fact was autozone brand replaced last year as well

She seems to run pretty decent all around except for high rpms or atleast something I can work with..

The reason for the log and tune not corresponding is because that data log was from a few days ago and tune was from today someone sent me the base tune and adjusted it slightly for my needs , runs better but does the same thing with this tune too

a91what · Jun 25, 2019

I also want you to try this tune for me, please note the IGN table is optimized for a 9-10:1 comp ratio but has the WOT curve set to that of the stock ECU for safe use of 89 octane. Once we figure out the breakup issue we can make it more aggressive.

When you load this tune file you will need to connect to the ECU, after it loads you will need to cycle the power to the ECU [turn the key off then on] I have setup the basics of closed loop idle for you based on the datalog you provided.

Good luck and keep us posted. I am willing to put money on weak spark issue, especially if the car is running a old or cheap TFI module...

I went through this issue helping @atatro

88nitrous5.0LX · Jun 25, 2019

Thank you so much for your help!! I will try her out when I get a chance and get back to you!
Thank you for your time!

88nitrous5.0LX · Jun 25, 2019

I am not seeing the link to the tune maybe i'm missing it lol

a91what · Jun 25, 2019

Looking at the datalog you sent, time stamp 175 you can see the MAP signal increase = increase in manifold pressure and at the same time the RPM drops.. a little bit later the AFR spikes lean[ there is a lag in the log for the AFR signal so the MAP and RPM are tied to this spike] this tells me that you may be experiencing a lean pop/missfire/spark crossfire at high rpm.
This can be explained by the IGN offset you have in the software.... it should be at 10* not 0* so the rotor is not positioned correctly [centered] on the spark plug post... [hope that makes sense] its called rotor timing, and yours is likely wrong this can cause issues with the rotor firing the wrong spark plug.

How to fix it....
1. unplug the injectors or the salt and pepper shakers so the car wont run, using a friend or a bump switch strobe the engine with a timing light while cranking and set the timing to 10* mechanically with the distributor. [DO NOT REMOVE THE SPOUT] This is the only time the distributor will be touched to set the timing.

2. plug everything back in and in the ignition settings set the offset to 10* and switch over to "fixed timing" set a value like 20 for easy reading. Now open the trigger wizard and using the trigger wizard adjust the offset until the timing number in the wizard box matches the strobed value on the balancer... Now the timing is set correctly.

rotor timing is critical if you dont understand the instructions above i can try to explain them using pictures from the software.

a91what · Jun 25, 2019

most likely the fuel will be off based on the fact that i used the tune and log files provided to me. please set the rotor timing as above.

88nitrous5.0LX · Jun 25, 2019

Ahhh i got you!! Yea someone who has done a few of these micros told me to
fix timing at 30 degrees
then match with a timing light with DISTIBUTOR

so i locked it at 30 and did not use the trigger wizard

88nitrous5.0LX · Jun 25, 2019

I will give her a rework tomorrow and see what we get, as far as the timing I understand what we are trying to achieve now.. thank you for your patience with me.

88nitrous5.0LX · Jun 25, 2019

Well i couldn't wait so had the wife help me get "Bad Habit" all set up for a new data log.. reset the timing according to your instructions... although I wont be able to get her out on the road until tomorrow, she has never idled so smooth!!! Warm up was a little erratic but not too shabby took a little free rev data log and looks like the trigger wizard ended up being -2.0

a91what · Jun 25, 2019

The ECU wont accept -2 the next time it starts. Should have gotten somewhere from 8-12 if the base mechanical timing was set correctly.

88nitrous5.0LX · Jun 26, 2019

Ok thank you I will give her another shot today!!

88nitrous5.0LX · Jun 26, 2019

I had a problem getting my timing light to trigger when the salt and pepper shakers were unplugged.. it barely wanted to flash and sometimes it didnt.. no sure if this is any indication of anything

a91what · Jun 26, 2019

Ok, let's try a different method. Your helper can hold the gas pedal to the floor while cranking, this will disable the injectors in the software.

88nitrous5.0LX · Jun 26, 2019

Ok perfect!!! I will give it a shot when I make it home!

88nitrous5.0LX · Jun 27, 2019

Just wanted to post that I got the timing dialed in finally, at 10° offset!! Will get some logs tomorrow evening and see what she does! I'm hopeful! The idle is still steady as can be too!

88nitrous5.0LX · Jun 28, 2019

I cant thank you enough. I'm speechless took the car for a spin and its a completely different car. Revved all the way out with a safe AFR here's the log..

5.0 microsquirt mustang hits wall around 5000 RPM

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