Quote:
Originally Posted by PTAddict
I use the Mast M90 on my personal car (LS7). I've also tuned a lot of GM ECMs on late models and retrofits.
As to what is "better", it depends. From my personal perspective, I won't use an ECU which doesn't support knock sensing/control, and both of these support it. Both also support drive by wire throttle, if that's what you want. To oversimplify a bit, the biggest difference at a high level is that the GM ECU runs open loop at wide open throttle, relying on the MAF sensor to account for airflow variations. The Mast runs closed-loop all the time, using a wide-band O2 sensor. Wide band closed loop is the optimal strategy for a performance motor, IMO, because it can account for variations that a MAF sensor can't, like the oxygenation of the fuel. But in practice, both can work well in performance applications if carefully tuned.
On that careful tuning part: some ups and downs to both. The Mast is much simpler in terms of the number of tables and interactions you have to deal with, but the (free) tuning software lacks convenience features like table smoothing and interpolation. That makes data entry for fuel and spark tables quite tedious. The GM ECU must be tuned with a package like HPTuners, EFI Live, or SCT Advantage. All of these packages are significant extra cost ($700+) if you obtain them yourself; otherwise you rely on a professional tuning shop, which is recommended in any case if you're not up on EFI tuning. The GM ECUs have a significant learning curve to tune correctly, more so than the aftermarket alternatives.
Another alternative to consider is the latest Holley HP or Dominator EFI system. I've not had any experience with these on LSx motors, but have tuned a couple of retrofit systems using the HP ECU recently. It's a very nice combo of ECU and software.
I'd give you a brief warning about cost assumptions. Depending on your exact combo, by the time you get everything necessary to make each ECU work, the cost differential can end up lower than you might imagine.
All this said, unless you're planning to change cams on your crate motor, I'd personally probably lean to the GM ECU package. Make sure you get it tuned, though - I've tuned three GM crate motors with retrofit ECU package, and each of them was fairly far out of tune, particularly the MAF transfer function.
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Question to PTaddict, do you know how far out the gm performance crate motors ECU's are? I have the ls3/525 going into my chevelle and am wondering how much more there could be in it. Have you done any of those set ups yet?
Excuse me if I am hijacking this thread, maybe a P.M. would be better let me know. Thanks.