511.99 ?

[DrX]

Does this limit apply to COS3?

Made some changes to the fuel system when I re-assembled the truck, so I am running a lower base fuel pressure in boost now. Hence, the values in my VE tables are now higher. On initial tuning I found myself hitting 511.99 g/s resulting in REP mode/throttle shutdown as soon as boost kicked in. I already hady C6101 maxed out.

I scaled down the IFR and VE tables by 20%. REP is no longer being triggered, but the logs show that I am still hitting 511.99 pretty easily. Does the 511.99 limit only apply below a certain RPM or TP?

[joecar]

512 g/s is the upper MAF limit in the PCM... i.e. the PCM can read upto 512 g/s from the MAF.

[DrX]

512 g/s is the upper MAF limit in the PCM... i.e. the PCM can read upto 512 g/s from the MAF.

Yes, I am aware of that. I'm just trying to understand why 1 day it was shutting me down(usual MAF/MAP to TP correlation codes) and the next it was not, even though I still hit 512g/s with the down scaled VE table. By the way, I am running an SD tune - dual 90mm throttles, no MAF.

Edit:
I should add some context: Other threads on here mentioned that hitting 512 g/s was the reason for triggering REP when the rationality tables were already maxed out(actually I had to fully disable the MAP rationality test using the VSS limits).

At least in my case, this limit does not in itself appear to be the trigger.

[joecar]

Ah, I missed the question, sorry... :doh2:...yes the MAF 512 g/s limit applies to COS's also.

My $0.02 understanding:
even tho you have maxed the rationality tables, there still is disagreement between MAF and MAP/TP (since MAF is being limited);

the MAF limit does not directly trigger REP, but can indirectly trigger it by causing the rationality tables to trip;

this is where you toss the MAF.

[DrX]

I tossed the MAF a long time ago.:)

I think I still hit 512 g/s(calculated) last night after scaling down another 20%. No REP though. I think I will try working the table scaling back up again and see where REP gets triggered.

[joecar]

Can you post a log file...

[DrX]

OK. Here's a couple I just logged tonight. Looks like I also have a new mechanical issue now, but don't mind that (see the lean spikes).

The 443 log is with no scaling of the IFR and VE tables. The throttle closes at frame 6571. The tables have been scaled down 36% for the 445 log, but 20% works just as well. Looks like the trigger may be the DYNCYLAIR value.

[joecar]

Hmmm... think it may be both DYNCYLAIR and DYNAIR...

I see DYNAIR flatlining at 512 g/s several times (reflecting the PCM's 512 g/s limit on airflow)...

I see DYNCYLAIR reach 2.58 g/cyl in the first log, it may not flatline but I agree it may be tripping the sanity tables... you are moving large air.

[DrX]

Hmmm............I did not have this issue last year and I had NO scaling in the tune at that time. But I was also logging lower DYNCYLAIR values for some reason. Here's an old log file:

[DrX]

Now, I did change the fuel system a little. I used to have 2 regulators with a higher base fuel pressure kicking in under boost. So that would have reduced the values in my old Boost VE table somewhat, thereby reducing the calculated DYNCYLAIR, correct?

[Highlander]

I would scale the injectors and cyl volume!