Howdy all,
Does anyone actually know what sensors have any control at all on the ignition timming?
Is it only the MAP sensor, Air temp and obviously the CAS? Does the water thermo sensor have any change on the timming?

Any input at all would be appreciated.

Cheers, Nathan.

 

From the S5 Turbo FSM (others will be similar), the following sensors can affect ignition timing:

CAS (obviously), AFM, coolant temp sensor, knock sensor, manifold pressure sensor, TPS, mileage switch, 5th gear switch, clutch switch, neutral switch; and for S5's only, add the rear defroster switch, blower switch, headlight switch, fog light switch and A/C switch.

Surprisingly neither of the air temp sensors affect timing. This surprises me.

Just goes to show how incredibly complex OEM EFI can be, even stuff this old. .

 

Thanks NZConvertible, what section of the FSM are you looking at to find that? I did look there first.. I just couldn't find any info!

But why on earth do the "mileage switch, 5th gear switch, clutch switch, neutral switch; and for S5's only, add the rear defroster switch, blower switch, headlight switch, fog light switch and A/C switch." all effect timming?!!

like.. really... rear defroster switch?...

Does it list exactly in what way the effect the timming? And im equally as suprised that air temp isn't accounted for... (especially when those listed above are.. )

 

S5 FSM, page F1-76 (NA) or F2-74 (Turbo). It doesn't say how much each sensor effects timing, but it's safe to say that the AFM, coolant temp sensor, knock sensor and manifold pressure sensor are the main ones, with the others just trimming as the engineers felt necessary, due to things like changes in idle speed.

 

Now this is very interesting...

When I get my new engine in I will be running the stock computer for ignition and using a microtech for fuel only.... Until I can afford a fuel/ign microtech.

But I am NOT going to have the AFM there.....

It was my (very limited) understanding that the AFM had very little, or no, change at all on the ignition timming.....

Sounds like its time for some serious experimenting with a timming light and some voltage input to the sensors when I get this car running again.

Anyone else have anything to add?

 

https://www.rx7club.com/forum/attach...&postid=871818

The red dots in the jpg were for another post, not related to this thread ....on the whole. The *0* are the players, the *X* the non-players. The ignition timing is shown at the bottom, far right.

 

Thanks HAILERS, I guess i'm just going to have to get out there with a timming light once I get my new engine in and find out how much exactly each sensor has an effect on the advance/retard.

I just still can't get over that the rear defroster switch changes the timming...

Cheers anyway guys.

 

AFM and CAS (rpm) are the big ones. The AFM serves as the "load" sensor for the ECU.

-Henrik

 

Yes, that is correct for the fuel injection ammount, but im near on 100% sure its not the same for ignition timing.

 

Why do you say that?

-Henrik

 

That was just my understanding of how the stock ECU controlled the ignition side of things.
However it seems from your .sig that you obviously know a hell of alot more than myself on this subject since you make a replacement chip for our ECU's.

How exactly does the ECU control the ignition with the AFM? I thought someone did some dyno pulls looking at the timming and noticed that with the hose to the MAP sensor disconnected that timming didn't change? (Im sure it was someone on these forums...)

 

That was the fuelling, not ignition. The MAP sensor definitely affects timing.

 

hehe I think I worded it wrong...

I ment the the timming stayed close to static without the MAP connected, as in it advacned/retarded only with respect to RPM not load when the MAP sensor was disconnected.

I realise the MAP sensor is integral to the ignition advance/retard system

 

yeah i've thought the same, i mean if you take the stock ecu feature by feature it has a lot more than the typical standalone, it just has a slow processor and its not tunable (easily)

mike

 

The AFM (along with a couple of other sensors) tells the ECU how much air is entering the engine. At a given rpm, any change in the AFM reading (ie via your right foot) reflects a change in the load on the engine which the ECU then uses to modify timing (among other things).

-Henrik

 

Yep, most people don't believe this. Of course a lot of it is related to emissions and sensor failure detection/handling (how many standalones have a limp mode?). The maps in the stocker are also quite a bit larger (finer resolution) than you get in a typical standalone.

All in all, amazing what can be done with 1MHz.

-Henrik

 

I understand perfectly well how the AFM works, my question was wether or not it only was used for fuel, you have now told me it is used as the primary load sensor for the ignition timming aswell, not in fact the MAP sensor.
Thank you for that.

Why then does everyone say then, that with a FCD your timming wont change above 8.6PSI of boost?

 

If you think our ECU's are impressive, you should see what new ones are capable of. They make even top-end aftermarket ECU's look like kids toys. The trend in new-car management modification is heading back towards piggybacks (albiet very sophisticated, laptop tunable ones), because throwing out the stock ECU is such a huge step back in capability.

 

What's weird is that it seems like the car has two air temperature sensors.

There's one inside the AFM and there's a seperate one by the throttle body.

If it says the IAT doesn't affect timing, that means the one inside the AFM probably does. I wonder if that also means a lot of people have their SAFC's hooked up wrong.

 

yes, instead of replaceing an $80 alternator because the voltage regulator went out you get to change the $800 ecu!

the rx8 is an excellent example of that, the guages for instance are networked, as is the traction control, etc, so you almost cant remove the ecu without major effort

 

I just thought I'd **** someone off and bring this thread back to life and ask a question...sort of.

I'm running out of things to mess with/up on my car, and I've been *adjusting* my afm's spring tension a tooth this way, a tooth that way and found that when I went a tooth to the more tension side that the car seems to react better. Part SEEMS to be on the fuel side looking at the afr, but after reading this thread It could also be the timing that is giving me that more responsive feel (not my imagination)

I have three turbo afms and each one reads a different voltage if I apply the same weight to the vane. The vane being unbolted and standing on its end with a given weight resting on the vane and reading the voltage output with a SAFC.


The afr's being leaner when I apply more tension to the afm spring, but the afr's reading about the same at wide open throttle in fourth gear. Stock afr's SEEM to be in the 10.5 range at full throttle. I see 100 percent on the safc percentage for the afm.

I hope nobody reads this and goes out there and screws up his/her afm. It's easy to do. humor

I've gotta go spend some money and have one of these afm's calibrated so I'll know what STOCK really is. Can't stand the idea of all three reading different.

Just one tooth one way or the other makes a large difference in the spring tension and the output voltage.

 

Why do you care about ignition timing and stock AFM's when you can just go stand-alone EMS and mess around with ignition timing to your heart's content?


-Ted