How does PFC read the CAS on an SR?

[jspaeth]

Just curious......does someone tuning a Power FC tune timing with respect to some baseline reading that it pulls from the CAS?


I recently pulled my CAS doing headwork and then put it back in (EXACTLY) how the FSM suggests....

...but I failed to think ahead and check to make sure that the CAS was in there that way before pulling it out.


The car runs fine (just idling in driveway) so the timing isn't way off or anything.....just wondering.


Hypothetically, if you were rebuiliding a new map for the car, could you just put the CAS in at any angle and just tune the timing in the PFC with respect to that?

[johngriff]

Just put the cas back in at TDC just like fsm instructs. PFC reads the cas just like the stock ecu, because it is mostly a stock ecu.

[jspaeth]

Thanks John......I did put it in the way the FSM says, but I am just paranoid that maybe it wasn't in there that way before I pulled it out......(maybe someone pulled the head before and didn't put it in perfectly?).


Also, I understand what you are saying about the PFC, but for a stock ECU, all of the timing settings are fixed, and DEPEND on the fact that the CAS is in there a certain way.

So, if the CAS was (hypothetically) in there wrong, could you just compensate for that when tuning?

Like if CAS is setup for 20* rather than 15* at TDC, could you just add 5* to all of the timing cells and get the same "net" effect?

[johngriff]

Well you are not going to be off just 5 degrees when making an incorect re punch. I think there are like 16 teeth on the cas /360deg, so you would be off something like 20 degrees if you re-punch wrong.

As far as "clocking" the cas after punching it. Yeah, you should have clocked it to oem base timing before doing the inital tune with the PFC. If you did, hooray, set the base timing just like you would via FSM and you are set back to the condition of your tune. If you / your tuner did not start out by setting the timing to stock, either that should be noted, or one of you should be spanked for being bad tuners.

I get what you are saying. If you had the base timing @ 15 when the tune was done, and now you set the base timing up to 20, yeah, you have advanced the whole map 5 degrees, which depending on the aggressiveness of your tune and some heat factors + high load/boost could give you a death blow detonation.

I doubt your base timing was set at 10deg for the tune, so I would set at 15. If it was 15, sweet. If it was set at 20, setting at 15 now will retard 5 degrees which should be safer.

Whole margin of 5 degrees is not going to kill you, as long as you test drive a little, listen for detonation, and watch your temps, and compare them to previous conditions performance you should know.

From now on, start your tunes with sensors near factory settings and you shouldn't have any issues moving into the future.

[jspaeth]

Well you are not going to be off just 5 degrees when making an incorect re punch. I think there are like 16 teeth on the cas /360deg, so you would be off something like 20 degrees if you re-punch wrong.

As far as "clocking" the cas after punching it. Yeah, you should have clocked it to oem base timing before doing the inital tune with the PFC. If you did, hooray, set the base timing just like you would via FSM and you are set back to the condition of your tune. If you / your tuner did not start out by setting the timing to stock, either that should be noted, or one of you should be spanked for being bad tuners.

I get what you are saying. If you had the base timing @ 15 when the tune was done, and now you set the base timing up to 20, yeah, you have advanced the whole map 5 degrees, which depending on the aggressiveness of your tune and some heat factors + high load/boost could give you a death blow detonation.

I doubt your base timing was set at 10deg for the tune, so I would set at 15. If it was 15, sweet. If it was set at 20, setting at 15 now will retard 5 degrees which should be safer.

Whole margin of 5 degrees is not going to kill you, as long as you test drive a little, listen for detonation, and watch your temps, and compare them to previous conditions performance you should know.

From now on, start your tunes with sensors near factory settings and you shouldn't have any issues moving into the future.

Thank you for the good explanation....my tuner is DEFINITELY a good one (Jeff Evans, one of the nation's premier honda tuners).

If the timing was somehow set differently when I last was tuned, would that be something he could have immediately seen on his laptop?

Also.....I DEFINITELY did not get the teeth wrong when inserting the CAS....it's just that once you get that part right, you can change it by small fractions with minor rotations of the housing, that's all i meant.

And yes, I am hoping that the baseline was at 15* before, bc that's how I have it now (per the fsm) and would like to be able drive the car kinda hard to test out the new headgasket I just put in before getting retuned.

EDIT: Also...John.....I don't (yet) have an AFR gauge or exhaust temp sensor (getting at least an AFR gauge VERY SOON).......but, my PFC does read the knock sensor......as long as the knock stays down, is that a safe indication that the timing is not way advanced and nothing damaging is occurring?

i.e. Is knock alone a good enough measure of it's running safe?

[johngriff]

On face value I would have to say no.

Its like... if you tuned it, and knock was low, then didn't change anything, and knock is really high, yes I would look at it.

BUT.

If you added cams, turbo etc things that make more noise attached to the engine.. then it is not a reliable metric. (stock knock sensor).

Get some det cans.

How will you log EGT and AF/R?

[jspaeth]

What are det cans? (I must be stupid or something).

Ummmm....don't have anything set up to do datlogging yet, but would at least like to be able to see AFR at a minimum and perhaps EGT as well.


EDIT:

All that's new since I did the headgasket and took the head off is springs/retainers and a Greddy Intake Mani.

So with that setup, is there any reason for knock NOT to be an indicator of safeness? Could EGT go up without knocking? I don't see any reason why it would, but i am no expert.

[johngriff]

The springs and retainers might make more rotational noise than you had before, and the stock knock sensor can pick this up as knock.


http://www.rpsport.net/haltech/prdimg/38580-Knock-Box.png

These are Det cans, high quality knock sensor for tuners.

You need some kind of datalogging to graph that data over what the pfc is doing (injection, ignition, ve, rpm etc).

Thats why haltech is so G.

I also carry widebands and egt's too.
http://www.rpsport.net/haltech/prdimg/30027-EGT-Sensor.jpg

Wideband:
Wideband O2 - Haltech Engine Management Systems (http://www.haltech.com/index.php?option=com_content&view=article&id=92&Itemid=34)

Shoot me an email if interested.

[email protected]