Engine cutting out on high rpm

[Yves]

I've added the msq of a run on high rpm. I also tried recording my last run to high rpm (5000) but for some reason it hasn't recorded.

I'm currently experiencing the engine cutting out once it reaches 5000 rpm. It's as if it reaches a wall there. I first checked the revlimiter but it was set at a low limit of 6000. I also disabled the revlimiter in the last run, but to no avail.

As some may have read in my previous post, it's a new manifold with ITB's and I just finished the airboxes for the stacks. Not sure if this is an intake restriction or not. I tried to use the intake and airboxes but without the K&N filters attached, but the result was the same, it wouldn't rev above 5000.

The VE's seem to increase to 5000, not falling off, which I would assume would be the case if the boxes or intake was restriction.

Is there something else I need to look at.
I'm also a bit troubled that tunerstudio didn't record the last run. Maybe some electronics issue ?

Thanks for any input. Really need some help on this.

[Yves]

For clarity, I'm using a HEI type electronic dizzy with external coil.

This one :

http://www.msdignition.com/Products/Dis ... butor.aspx
http://www.msdignition.com/Products/Coi ... _Coil.aspx

It feels like I'm hitting a revlimiter.

[grom_e30]

look out to see if the ecu is losing sync with the tach input signal can feel like a misfire or a rev limit, rpm may drop to 0 in the log, also look at the sync loss counter.

[Yves]

look out to see if the ecu is losing sync with the tach input signal can feel like a misfire or a rev limit, rpm may drop to 0 in the log, also look at the sync loss counter.

You mean during driving or with a log ? In a flash I saw some lights flickering on the screen in red. Not sure what they were. Left side, bottom of tunerstudio.

I'm having the impression that something stopped working as the logging failed during my last run.

Meanwhile I've been searching this forum and the internet and it seems there are reports about VR-sensor ignitions cutting out above 5000 rpm. Since it really felt like hitting a revlimiter, this seems to be the first things to investigate. Is there something else I can check ?

[grom_e30]

when the ecu loses sync the cranking and ase and wue indicators may flick back on, you can record a normal data log and can look for sync loss in that log

[Yves]

A question : in the ignition options, my dwell type was set to standard dwell. I now see some info on the internet that says it should be fixed dwell and 50% dwell duty. Would that help ?

[grom_e30]

that setting seems to be for ignition modules that have internal dwell edis ect, by all means try it and see if it helps.

[jsmcortina]

A question : in the ignition options, my dwell type was set to standard dwell. I now see some info on the internet that says it should be fixed dwell and 50% dwell duty. Would that help ?

Where is this?
What does the actual Megasquirt manual say?

James

[Yves]

A question : in the ignition options, my dwell type was set to standard dwell. I now see some info on the internet that says it should be fixed dwell and 50% dwell duty. Would that help ?

Where is this?
What does the actual Megasquirt manual say?

James

Here :

http://www.diyautotune.com/tech_article ... butors.htm

TunerStudio Ignition Configuration for MS2/Extra or MS3:
•Spark mode to 'Basic Trigger'
•Trigger angle / offset = 10� (this will vary, depending on the distributor orientation, see notes at the end of the article)
•Ignition Input Capture to 'Falling Edge'
•Spark Output to 'Going High'
•Number of coils to 'Single coil'
•Spark A output pin to 'JS10' if using our build guide above
•Dwell type to 'Fixed Duty' and use 50% duty cycle

I left it at the standard settings that came with tunerstudio, which is standard dwell type.

So what should it be ?
I would like to continue tuning the car, but this is seriously blocking me. Engine can normally run to 7500 rpm, which is a far cry from where I'm now.

[jsmcortina]

How is your MSD wired in?

James

[Yves]

G terminal to a seperate ground going back to the relay board and battery
B terminal to Vref on the relay board (same as TPS)
R terminal to tach on the relay board
E terminal to S5.

And the 2 pole connector :
+ to coil +
- to coil -

there is also info saying that one should turn the R 52 & R56 pots ...http://www.msextra.com/doc/general/tachin-v357.html#vr

[jsmcortina]

We seem to be at cross purposes here.

You posted a link to how to wire in an MSD distributor and MSD box (e.g. MSD 6AL)
Now you are talking about HEI7 ?!?!

Please read the HEI7 section in the appropriate hardware manual (i.e. click on where it says Manuals above.)

James

[Yves]

No, I'm not using the HEI7 (although that seems to be similar) or msd 6. I'm using an MSD 8366 distributor, which is similar to the electronically controlled distributor of GM. I just searched on the internet and found the link in my previous post.

http://www.msdignition.com/Products/Dis ... butor.aspx

It's wired like this :



Tach output from coil goes to the dash tach.

Please advise as I'm not sure what to do now.

[jsmcortina]

According to their page it is an HEI8 replacement.

In any case, do not use fixed dwell with HEI7 or HEI8 as you will get excessive dwell at low RPMs and insufficient dwell at high RPMs.

How is your Megasquirt wired internally? Are you actually using JS10 for the spark output?

Have you strobed your timing to confirm it is correct? Does the strobe show a spark dropout at high RPMs?

Are you using a higher energy coil? What dwell does the manufacturer advise? Single coil installations will always suffer from dwell starvation at high RPMs.

James

[Yves]

According to their page it is an HEI8 replacement.

In any case, do not use fixed dwell with HEI7 or HEI8 as you will get excessive dwell at low RPMs and insufficient dwell at high RPMs.

How is your Megasquirt wired internally? Are you actually using JS10 for the spark output?

Have you strobed your timing to confirm it is correct? Does the strobe show a spark dropout at high RPMs?

Are you using a higher energy coil? What dwell does the manufacturer advise? Single coil installations will always suffer from dwell starvation at high RPMs.

James

James,

I hereby include a logfile of the events. I went 2 times up to 5000. Pulled fine untill that rpm and then it held back really serious.

As for sparkt output : yes JS10
I havent changed anything regarding dwell time. It's the same setting that came with tunerstudio in my files. (see attachment). I found some thread on the msd forum with an msd rep saying it should be in between 3 and 3.25. I currently have 3.1

I do notice that the AFR drop really low, in the 10 range at those rpms.

I do not seem to see any events.

Thanks for helping me out and sticking with me. I really appreciate it.

[jsmcortina]

I do notice that the AFR drop really low, in the 10 range at those rpms.

That could be the problem, is the VE table tuned in that area? The VE values seem to jump up a lot. 10:1 AFR when free revving will almost certainly hold the engine back. Try leaning the VE table out in that area and see if that changes things.
i.e. in the row where it has:
89 108 107 105 103 100 98 95
Perhaps try:
90 90 90 90 90 90 90 90

James

[jsmcortina]

Also, in the datalog, just as you reach the higher RPM you step on the throttle and then the engine really dies because there was a BIG dollop of accel enrichment on top of the already over-rich mixture. Looks like your AE is adding far too much fuel.

James

[Yves]

James,

Another run. This time I pulled the VE's lower.

I was able to make a run to 5000 and it stopped revving, when I saw that the tach on tunerstudio was flashing red. I went into the designer mode and changed the limits on the gauge. Then I could run over 5000. Awfully strange.

MSQ and log attached.

Hopefully someone will find this useful.

Thanks already for the heads up with the too rich AE.