Rpm limits of p59

[garryharris841]

So do some pcms have rpm limitations?here's my problem, 2005 silverado, ls3 based stroker, nice build. 24x, 13:1, e85..... Anyway all our rpm limits are set to 10,000, speed limits 200. We hit a rev limit at 7100 rpm, I can hold the pedal and it will bounce off of it. But the funny thing is, that the data log shows rpm peak and gradually slow down, all data from the ecu stops for about 2 seconds so my logs don't show bouncing off this limiter, and scanner just "connects the dots" from the last data point. This engine revs and we need it to. It's a pulling truck and some tracks we will peak at 7000 and some loose tracks we hit the limiter and lose all momentum. I'm on my phone and don't have a way to post a log but I guess I'm really just wondering if this ecu can even process at those rpms above 7000. This is a max effort NA build and I find alot of tuners have never done this.

[blindsquirrel]

Crank position sensor, or incorrect sensor gap, or excessive crankshaft endplay.

[garryharris841]

So we've been over that, gap, different sensors. It is so consistent I'm sure the ecu is commanding it but when it starts we lose data for 1-2 seconds when it does it so we can't see the dropped injector pulse. We've checked thrust endplay.

[blindsquirrel]

Well, I'm sure it can't be anything in the tune file. Otherwise you would've posted it. Right?

[garryharris841]

Look I know it's hard to believe that I don't bring my computer home, it stays with my dyno, I'm certain it's not in the tune, and so is everyone that picked it apart already, the question was, if anyone has found the limitations of the ecu, as far as I know gm never Released an engine package with a p59 that even came close to 7k. So why would they make one capable of it. I've been down this road before, you post a tune, 10 guys tell you what they don't like about it, and it usually isn't relevant to the issue, but none ever have a solition, and that's not the point of the post, I just wanna know if anyone has found a processing limitation of these. I appreciate your response but I've been over the basics like cam and crank resolution.

[blindsquirrel]

The problem, as you've described it, sounds 100% exactly like how they behave when there is a crank sensor issue. A 'new' sensor is just one that hasn't been proven non-defective yet. Even GM-branded parts are more often these days sourced from the same Chinese suppliers for the off-brands. But you are sure it's not that, so this too is probably wasted effort.

[gametech]

edit- nevermind.

[SiriusC1024]

You seem competent enough, and I take your word for it that it's not the crank sensor or reluctor.

Your reasoning about the processing capability makes sense. Here you pointed out that you lose telemetry briefly. In a previous post you mentioned backfiring, which could possibly occur if the processor isn't able to keep everything synchronized.

One thing you might try is loading the stock OS and run it in SD. You're probably aware that in SD with the stock OS the secondary VE and Lo spark tables are referenced exclusively. I wonder if the enhanced OS has more overhead?

Could try trimming a few things out to reduce processing load such as:
- Disable Airflow>General>Complex model
- Doubt you're closed loop, but disable if so.
- Disable PE. Command desired EQ through the open loop table exclusively.

Another thing that might reduce processing load is to go into System>System Options and disable something like Brake TqMgt. Idk what the implications of disabling those options are concerning the way your vehicle will behave. Worth a try maybe?

Of course, check for non-normal behavior in your non-normal operating range. Things like voltage instability from alternator overspeed.