Broken Crankshaft Count?

[MSEngineering]

Very interesting Jon!

So as far as the ECM's...

You think its because the ECM isnt compensating and applying smart "smoothing" logic to the (probably not perfectly clean) raw signal from the CKP sensor? So when the RPM shifts up/down, the ECM is constantly chasing its tail adjusting actual timing, so to speak? Rather than taking an "average" CKP/RPM reading over a specified duration of time?

And then on the 01-05 trucks, we have the FICM in the equation too...when you think about it, its a pretty complex series of steps that has to happen correct?

1...ECM reads raw CKP signal from the sensor, processes it.

2...ECM turns that raw signal, does 'stuff' to the signal, turns it into a "replicated" smoothed square-wave RPM signal, which it then outputs/forwards to the FICM, so the FICM knows real-time engine RPM (as opposed to only getting RPM over "slow" 250k CAN)

3...ECM calculates actual injector pulsewidth, timing, etc based on what the tune says

4...ECM sends those commands to the FICM via the 8 discrete "injector control" wires

5...FICM receives signals, processes them

6...FICM fires the injector

I dont know enough about the actual hardware/software involved here, but between all of those steps and messages/signals flying around, it would seem there are quite a few areas of potential "screw ups"?

And onto the FICM...what exactly do we know about it? Does it do any extra processing of the injector-control signals? Does it have the ability to make any adjustments of its own? Is there any additional fuzzy-logic that happens within the FICM before it actually fires the injectors?

What is the first bottleneck in the entire system? ECM processing power? FICM processing power? FICM driver circuitry? Inaccuracies of the CKP sensor/wiring/signal noise? Injector solenoids themselves?

As far as what the ECM reports for a main injection timing PID to the scan tool...im sure that value is buffered, and maybe just a "roughly X* is desired right now" PID, and not a "this is the actual timing that the ECM is commanding at this instant" PID?

Given the sloowwww 10.4k Class 2 bus that 01-05 ECM's present scan tool data on, I would guess the ECM just broadcasts a "general/desired" value?

Has anyone plugged in a CAN datalogger on an 01-05 truck, and then compared it to what EFILive shows in logs over Class 2 bus?

Does this margin of error (IE, the actual timing jumping around) increase with RPM? Are the timing +/- fluctuations random on each crankshaft revolution, or is there a visible trend of certain times when the actual timing is constantly (>500milliseconds or so) + or - the "desired" timing?

Ben

The FICM does account and modify timing for this...

 

[Dave c]

Alt fire cam spools slower? More top end?

Slower spool. And about 15hp less on top. It's the way the cylinders fill with air. However. There is away to compensate around it.

 

[GSXRTURBO1]

Slower spool. And about 15hp less on top. It's the way the cylinders fill with air. However. There is away to compensate around it.

wait, whaaaat?

 

[mike diesel]

I went with 16:1 pistons and an AF cam. Somewhere between those 2, I lost a ton of spoolability. Normal driving was fine, 4x4 launching lost any spool I had previously with the stock motor.

So either the lower compression caused it or the cam...I don't know which. Had to go to a suncoast 1053 to spool again.

 

[DMAX497]

I went with 16:1 pistons and an AF cam. Somewhere between those 2, I lost a ton of spoolability. Normal driving was fine, 4x4 launching lost any spool I had previously with the stock motor.

So either the lower compression caused it or the cam...I don't know which. Had to go to a suncoast 1053 to spool again.

Same problem for me...

Went with AF cam and 16:5 compression and POO-bye to spool up...

Had to get the 3k stall 1053-1 put in. Hopefully that helps.

Also have little spool jet going on truck now too.

 

[duratothemax]

I went with 16:1 pistons and an AF cam. Somewhere between those 2, I lost a ton of spoolability. Normal driving was fine, 4x4 launching lost any spool I had previously with the stock motor.

So either the lower compression caused it or the cam...I don't know which. Had to go to a suncoast 1053 to spool again.

I have never personally driven an alternate firing order truck...but Ive driven plenty of built motor trucks...and yes, the lower CR's definitely do feel noticeably lazier than stock CR.

So I cant speak for the AF cam, but your lower CR is definitely a part of it.

 

[Verlon at ATP]

I have had 16.5 ovals in for threes years now. Had standard fire 6480 in for 2 years and this year went to the alt fire 6480. Spool does not seem any different than last year.

My turbo setup changes often enough that differences in spool happen all the time for me though.

 

[Stingpuller]

Cams

I will bet everyone who lost spool up with a alt cam went from a stock cam to it. If you drop compression I promise it will be harder to spool a turbo. Get your cylinder pressure down around 250 then you need to get creative! :woott:

 

[DMAX497]

I will bet everyone who lost spool up with a alt cam went from a stock cam to it. If you drop compression I promise it will be harder to spool a turbo. Get your cylinder pressure down around 250 then you need to get creative! :woott:

Like this creative?

Sorry to derail.

 

[TROJAN366]

I really hope I don;t lose spool due to dropping to 16:1 but I think the Danville 72R should keep things happy!

 

[hondarider552]

I ran stock lbz compression in my first engine and will be dropping to 15.5 next go around.

 

[56taskforce]

Correct me if I am wrong but I am to understand the reason behind dropping compression is to be able to run more boost. So it seems to me that it is a trade off and is moving the power higher up the RPM range. As far as AF cams loosing power I have to ask how many of those who are switching stay with the same lobe profile?

 

[wrcknkrw]

Seems to me most everyone changes more things than just a cam at the same time. Makes for too many variables to account the change in spool being solely the alt fire cam.

 

[Cknight199]

Same problem for me...



Went with AF cam and 16:5 compression and POO-bye to spool up...



Had to get the 3k stall 1053-1 put in. Hopefully that helps.



Also have little spool jet going on truck now too.

What is weird is I did the same and didn't loose spool down low.


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[juddski88]

And different turbo setups matched with different brand cams. Oval bowl pistons also don't react the same as standard "mahle" style bowls.

 

[hondarider552]

What is weird is I did the same and didn't loose spool down low.


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Didn't loose spool but your track time last Friday night proved otherwise lol.

 

[Cknight199]

Didn't loose spool but your track time last Friday night proved otherwise lol.

No but really my truck has always been hard to light, I used to have to switch between tunes while staging because some would kill the turbo because of fuel. Honestly it's almost easier to spool than it used to be which is weird


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[hondarider552]

I know the converter you run is less than optimal for your turbo though.

 

[Dave c]

Alter firecam. Oval bowl pistons. And less cr are all contributions to slow spool. Also a problem with the above is more smoke . It's all from lack of efficiency at one point or another.

 

[S Phinney]

Alter firecam. Oval bowl pistons. And less cr are all contributions to slow spool. Also a problem with the above is more smoke . It's all from lack of efficiency at one point or another.

I would agree some with your comments. Anything that bleeds off cylinder pressure will have those problems. Alternative fire cams with low LSA have more overlap . That reduces spool not the firing order. It may be possible to some extent for the cylinder pulses with a alternative fire came slows velocity of air flow but I would think that is a lesser contributing factor than profile of the cam itself.