Bigretardhead

okay, well I'm just going to hook up the AFM for now. then, once its running, I will try it with and without the AFM plugged in, and see if there's a difference. oh, and I'll be doing it on a dyno probably, so don't worry, it will be seeing boost and load and stuff before I determine who is correct. ( and I hope its white FC, just because I don't want that damn AFM, lol).

White_FC

On the basis that this has been the way that cars have run for many many moons (RPM and Vacume)

On what basis are you making your claim? You seem much more sure than I on the matter you obviously have a good understanding of the code in the ECU, care to elaborate?

Your trying to tell me the total advance will be much higher in idle than in 5th gear at WOT? Get ya hand off it.

The MAP sensor is used for trimming the timing map, most definatly so. However the main 'load' sensor per se really is the CAS(Rpm), thats what changes timing the most really, so see it depends which way you look at it as to what is the main 'load' sensor.

I will be most suprised to see if the AFM does more trimming of the timing map than the MAP sensor. _Most_ supprised...

But I do like being proven wrong, so I can't wait for Bigretardhead to goto the dyno.

HAILERS

WHITEFC......What does that phrase mean *Get ya hand off it*?????? Just curious. I can make a guess, but, my minds probably in the gutter, so to speak. It's a term/phrase I'm not familiar with.

Henrik

As the author of the Rtek chips, I have a pretty good understanding of the
ECU code

Don't forget that the AFM and boost readings are "coupled" as a fn(rpm, VE).
While your correct that it could be done off the MAP sensor, in FC ECUs it
is not.

Prove it for yourself, its an easy test. Get your timing light and a vac pump. Hold the engine at a constant rpm above idle, and apply vac/pressure to the boost
sensor - see what happens to timing - zilch under normal operating conditions.

I never made any statements about total advance - don't know where your
getting this from. Obviously total advance has several components to it, the
two largest are rpm and load (AFM), analagous to mechanical and vacuum
advance in dizzy setups.

-Henrik

White_FC

Probably thinking along the right lines there HAILERS..



I thought as much..

I can't say I could forget that, seeing as I never had that sort of inate understanding of the stock computer

This is precisely what leaves my questioning this whole thing. I've done this before!
Without an AFM, just the MAP sensor that timing most _definatly_ changed(read:retarded) with or without the MAP sensor connected. By connected I mean the vacume line. When it was disconnected, MAP sensor seeing atmospheric, it was more retarded than with it connected to vacume. How much? I couldn't say. A few degrees at most.
This was above what the stock computer would consider idle speed. (including TPS)

No, I made the statement about total advance. Because it was seem intuitive to me that if it retards it under load(you say by ways of the AFM reading), it retards it and that is included in total advance, total timing whatever you want to call it.

How much does the AFM change the total advance given a certain vacume (not strickly possible in the real world but i'm sure the code has that info in it)
Or concersly, how much does the MAP sensor change total advance given a certain AFM value?

I've never done any testing with the AFM so im very interested.

My point still stands though, and someone on a dyno could prove this _VERY_ easily.
If the total advance is the same, or damm close to, in neutral at a certain RPM as it is in 4gear on the dyno at that RPM then the AFM doesn't do squat.
If it changes a few degrees, then there you have it, it does have a large input into the whole shebang.

This has some interesting conatations for people timing their car in neutral and then going to the dyno.

Henrik, if you could provide some numbers that would be interesting aswell.

Bigretardhead

okay, well now I've got a problem....NO spark. I've checked sooooo much stuff, and I still can't figure it out.

so, I've got all the sensors still running to the ECU in the engine harness, passenger side. the other harness is untouched. I know the coils work, ECU has power and ground, ECU has all sensors from pass. side harness except the knock sensor isn't connected to its box yet(but that shouldn't do it, right?) , and everything on the other side harness is like normal, and has not been touched. CAS works. coil is getting power.....but, no signal. no fuses are blown. I've looked through ALL my wiring, and wiring diagrams, but I can't figure out why its not getting any signal from the ECU...

is there something besides the sensors on the pass. side harness that is required for the ECU to even send a spark signal? I would think that all the ECU really needs to make its initial base timing spark signal is CAS, power, and ground, but I'm obviously missing something...

White_FC

Well thats all I had hooked up to mine, so i'm at a loss as to why yours isnt working.

Bigretardhead

hmm...maybe its the ECU then... I guess I'll try one of my spare N/A units for now, since the turbo isn't even routed into the TB yet (v-mount project). this thing is a PITA.

Bigretardhead

well, tried a different ECU, no such luck. guess I'm pulling out my harness to find what I fucked up.

but still, it seems like it should work with just CAS and power/ground.

HAILERS

When all seems darkest.......pull the cas out of the engine. Leave the electrical connector in place.

Pull your LEAD wires just barely out of the coil bores. Where they are just resting on the hole of the coil bore. Just one of the lead coil wires will do.

Turn the key to ON. NOT START.

Spin the gear at the bottom of the cas as fast as you can. You WILL see a large spark at the LEAD coil wire that is just out of the coils bore.

If you saw spark, you don't have a sparking problem

If you did NOT see spark, then I suggest you get a meter out and pull the plug off the boost/pressure sensor and see if there is 5vdc approx, on the BROWN/WHITE wire. If there is NO approx 5vdc, then the ECU MIGHT have bitten the dust.

Note that a slowly spinning starter/engine will pull down the voltage to the coil assy and there is a chance you won't notice spark.

If your really, really, really sure you don't have spark......pull a plug off the lead sparkplug. Wet your fingers. Touch the wire end. Wet a finger on the other hand. Touch a good chassis ground. Now have someone crank the engine over (I have not had any takers on this suggestion as of this date. How about you??) humor.

Bigretardhead

hmm... thanks hailers.

tried the CAS thing, no spark. I even licked my finger and and touched the wire/chassis during cranking. hehehehe. and yeah, nothing. then I checked the MAP brown/white wire, and I'm getting app. 1 V. I think I fucked up the wiring a little hehehe.

White_FC

Make sure all the things are grounded properly, AFAIK there was a few ground points in the stock wiring.

Bigretardhead

okay. I'll check into that.

and the MAP brown-white was showing 1.17 v.

we also check all the wires to the CAS, and every single one of the 4 also was showing .622 v...... is that right?

HAILERS

Sorry, the 1.17vdc is very discouraging. It should read approx 4-5vdc.

There's nothing special about the boost/pressure/map sensor as far as spark goes. It is just a convienient place to see if the ECU is putting out a Ref voltage or not. If pin 2A of the ECU shows not 4-5vdc, then the thing will never spark. 2A is a output wire that feeds Ref voltage to several sensors, TPS, MAP, AFM etc.

Several things have the Ref voltage going to them. Again, the pressure/boost/map sensor was just handy. The ECU's pin 2A is more difficult to get to.

Whatever makes the Ref voltage inside the ECU, gets destroyed by someone grounding by accident or by design, one of the brown/white wires that carries the Ref voltage to the sensors.

Got a spare ECU. Might try it. Then again there's always the chance if one of the brown/white wires is grounded, that you'll fry that one also. Make sense?

You might want to access the ECU and look at the small plug and see if you have the battery voltage on that plug plus I believe another 12vdc from the main relay. If they are there.....then the ECU is cooked. Ain't a gonna make spark ever and ever.

Forget about the cas wires. Not a worry and the voltage is not to be considered. It's the cas that actually puts out the voltage TO the ECU. What you read from the ECU TO the cas is not relevant. Just forget that idea for now.

EDIT: Just in case.......none of the sensors that are supposed to get a ref voltage on their brown/white wires, have squat to do with SPARK. It's the idea that this ref voltage is not available to the devices inside the ECU either, therefore no spark.

I've seen that 1 volt stuff before. Won't work. Gotta be 4-5vdc.

EDIT: I'm not near any diagrams, so I can't tell you which of the wires on the small plug of the ECU are supposed to have the 12vdc. I know one is black/white but I forget the others color. Key to ON when you look for it.

HAILERS

Ah. I went back to figure out what kind of car/combination you have. You've some type hybrid and are using the stock ECU for spark only. Question: the ECU normaly gets its ground circuit from a ring terminal on top of the rear rotor housing. Is the wiring still there??????? If that ground for the ECU is not there, the ECU can't/won't make spark.

You need to get a meter and go to the ECU. See if the ground wires on the PLUG are ringing/ohming to a good chassis ground. Like to the studs that hold the ECU down. Again, I don't have the pins in my head. One is 2R. It's the middle plug. You'll need a diagram. No diagram.....look for pure black wires and see if they are grounded or not. Anything over say 1 ohm is not really very good.

DON'T do a bunch of silly things like run grounds to the coils or the ECU's chassis. That isn't helpful in any way. Gotta ground the wires at the ECU that are supposed to be grounded. Maybe I'll post the ground wires for the ECU tomorrow.

Bigretardhead

okay, black-white doesn't have any power. white-blue is the other wire, it shows 12v. looks like black white is our problem.

hailers, you are wanderful. looks like we are starting to get somewhere.

Bigretardhead

both blacks are grounded well.

Bigretardhead

okay. I think we got it. apparently black-white got routed into brown-white somewhere. hopefully this does it!

Bigretardhead

yeah!!! well, it started up last night. I guess that was our problem.

thanks VERY VERY much hailers, and all others that helped!!!

Rex4Life

For archive purposes and people that use the search feature--the AFM most definitely impacts the ignition timing. Aside from rpm it is the biggest factor on ignition advance. Here's a chart from another thread I created:



and the thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-timing-measurements-497564/

Scott