NO PC - Mega Squirt/Mega Tune, never ending issues Options

[Scott S]

Hi All -
Does anyne have a megasquirt/megatune FI set up that actually works... at altitude?

My brother has been building a big bodied audi S-4 for thre years. As of today the car has less than 1000 miles on it over that time. The car is blisteringly fast - it dynos between 550 and 600hp at the crank. However the megatune management system is so unreliable/unstable that the car will run great for an hour, then start doing things like randomly shut itself down, or drop a cylinder for no reason. The guy who is the go to guy back east actually reccommended that he set his idle to 1500+ rpm's to keep the car from stalling when the AC is turned on. Other than that, the usual response is just to wait for the next upgrade. The mechainic who is doing the build is fantastic and just as pissed as any one over the issue.

The lower elevation guys have no issues, it only seems to be affecting those at higher altitudes. Its like they never tested the system anywhere above sea level.

There have been a few threads on the MS system on our board, but even after searching, I could not find where anyone was ever beyond the point of "well, there are some issues, but I will work them out later". Just curious if anyone has actually successfully installed a fully operational system.

Thanks - sorry for the book...
Scott S

[JamesM]

Hi All -
Does anyne have a megasquirt/megatune FI set up that actually works... at altitude?

My brother has been building a big bodied audi S-4 for thre years. As of today the car has less than 1000 miles on it over that time. The car is blisteringly fast - it dynos between 550 and 600hp at the crank. However the megatune management system is so unreliable/unstable that the car will run great for an hour, then start doing things like randomly shut itself down, or drop a cylinder for no reason. The guy who is the go to guy back east actually reccommended that he set his idle to 1500+ rpm's to keep the car from stalling when the AC is turned on. Other than that, the usual response is just to wait for the next upgrade. The mechainic who is doing the build is fantastic and just as pissed as any one over the issue.

The lower elevation guys have no issues, it only seems to be affecting those at higher altitudes. Its like they never tested the system anywhere above sea level.

There have been a few threads on the MS system on our board, but even after searching, I could not find where anyone was ever beyond the point of "well, there are some issues, but I will work them out later". Just curious if anyone has actually successfully installed a fully operational system.

Thanks - sorry for the book...
Scott S

I have ran multiple and different MS systems in one form or another for years.

I am not as high as you in terms of elevation but SLC is definatly above sea level. Max ambient air pressure i see here is about 85kpa. With my megasquirted 914 I have not yet encountered any issues that stem from running at high altitude that i am aware of. Last autocross i took it to was up at alta ski resort ~8200ft elevation and i did not seem to have any problems running up there as well, other then the problems you would expect when trying to autocross a 914 at 8000+ ft elevation after a 4000ft climb anyways.

I suspect your problem might not be entierly altitude related.

What hardware version and code version are you running and what are the details of your setup? are you controling ignition as well as fuel?

And whats the deal with setting the idle to 1500+? is this due to a lack of an idle control valve?

I need more information here to get an idea of whats going on.

Do you have any datalogs when the problem is occuring?

When you say you drop a cylinder is that just for a single ignition event or does it continue to miss?

If you are having processor resets I would suspect some sort of interference or bad hardware. The resets themselves can cause all sort of other issues when running as during initial boot up the MS takes a pressure reading to use for altitude compensation. If a reset occurs and the processor takes its altitude compensentation reading while the engine is spinning it is going to get an incorrect measurement and from that point on everything will be fuched up.

one more thought... I just reread your post and saw that it runs fine for an hour before it starts acting up which gives me a couple more questions...

what are the details on your injector setup, low or high imp injectors? resistor pack? PWM?
and
where do you have your ECU mounted?