Cam sensor advancement

[buickpower]

I was reading an article on gnttype that said sometimes sputtering or popping with larger cams can be helped by advancing the cam sensor a couple of degrees. It also listed the lengths of tape you put on the balancer to get varying degrees of timing. Since default is 25 deg ATDC, would 24 degrees be advancing the cam sensor? Just wanted to verify.

 

[turbopaul]

Some myths never die....decide for yourself if the injector fires at a different time when the cam sensor is moved....

http://www.turbobuicks.com/forums/showthread.php?t=17681

Paul

 

[buickpower]

i've read that thread before, some people like LC still maintain that it helps, and i just wanted to tinker and prove it for myself. can anyone answer my question?

 

[buickpower]

never mind i found it.

 

[Blown&Injected]

It would be advancing it 1*

What are you trying to check out and do you have any results yet?

I read the advance cam sensor thing and am about to put one in with a big roller cam and am interested in personal experiences

 

[bruce]

Here's some more data:

http://www.t6p.com/forums/showthread.php?t=5966

Yes, it matters, moving the sensor a few degrees does nothing. You have to change the code, to change the injector timing.

Switching to batch fire, as mentioned else where, does change when the injectors firing point in relationship to the intake valve opening (for at least some of the injector firing events). So in that reguard, running in batch *may* seem to be an improvement, since every once in a while the injector offset might be better.

Just as a FWIW, the injector firing offset table, needs to account for load and rpm to be effective, and PE is different situation alltogether (well at least to what I've seen/ found).

But, I don't run 9s.

 

[Blown&Injected]

Gonna have to read that post a few times to try to get it

So how about the executive summery? Cause and effect type stuff?

Sounds like Batch fire changes something with regard to injector fire - but only sometimes???

BTW, this is not a challenge!!! Just trying to understand.

Is the load and off set table critical for those only interested in WOT?

Damn, I thought I knew somethin'bout these cars. PE = Power Enrichment? As in add fuel for more load? Sounds like an entire different table

 

[bruce]

Gonna have to read that post a few times to try to get it
So how about the executive summery? Cause and effect type stuff?
Sounds like Batch fire changes something with regard to injector fire - but only sometimes???
BTW, this is not a challenge!!! Just trying to understand.
Is the load and off set table critical for those only interested in WOT?
Damn, I thought I knew somethin'bout these cars. PE = Power Enrichment? As in add fuel for more load? Sounds like an entire different table

Yes, that link and the other take some time to grasp, well to us mere mortals.

Yes, the injector firing in batch fire is just once every engine revolution, and not based on anything other then the DRPs (Distributor Refernce Pulses, ie crank sensor). So every 3rd *window* the injectors all squirt. So the fuel is left to puddle around, or blow past an open valve, or just whatever, with the puslations in the plenum, it all kinda blurs with the fuel not being synch'd to any definite event/ cylinder position.

At the longer injector durations it's not as critical, since the injector PW covers so many cam related events at that stage.

Yes, PE = Power Enrichment. ie the commanded AFR goes from 14.7 to whatever the chips PE AFR is set for. BTW, there are other fuel adders.

 

[TurboTR]

Yes no matter what it will never die (lol). But the reality is, the crank sensor pulses are what the ecu uses for crank position reference info. Things that happen in relation to crank position (spark, inj) are referenced off of those pulses. The cam sensor is just a logical pulse, not a crank position pulse. It just marks the correct signature crank pulse so that a sequential inj system can sync up to the firing order, and in our case the DIS as well.

If ~ 1-2 deg mattered so much on inj timing, and if the cam sensor was used to reference inj timing, why on earth would there be only one cam pulse every 2 engine revs??

Having sequential inj is ok if you know what angle to set it for. But the "correct" inj angle is a moving target and changes with speed and load anyway. I think some oem's control the inj angle in terms of when the inj event is finished, as opposed to when it should start. For low speed emissions operation it's all probably quite important. At wot it seems to hardly matter for our port inj systems with ~ long inj duration.

TurboTR

 

[bruce]

The cam sensor is just a logical pulse, not a crank position pulse. It just marks the correct signature crank pulse so that a sequential inj system can sync up to the firing order, and in our case the DIS as well.

If ~ 1-2 deg mattered so much on inj timing, and if the cam sensor was used to reference inj timing, why on earth would there be only one cam pulse every 2 engine revs??

Having sequential inj is ok if you know what angle to set it for. But the "correct" inj angle is a moving target and changes with speed and load anyway.

The ecm couldn't care less about the DIS, other then to toggle the Bypass line, and send the EST signal. The module figures out which coil to fire. The injector fire signal is not an imaginary, or just when ever event, it is keyed to the crank's rotation.

Any cylinder just fires once in two engine revolutions, so to fine #1 or any spefic cylinder means just one cam synch pulse ever other revolution.

That's why I said you have to use a table for it.

 

[TurboTR]

I guess my post was misunderstood.

TurboTR