posted January 08, 2004 01:14 PM                         

quote:

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Ignition Timing Strategy
The ECU determines ignition timing by comparing engine operating parameters with spark advance values stored in its memory. The general forumula for ignition timing follows:

Initial timing + Basic advance angle + Corrective advance angle = Total spark advance.

Basic advance angle is computed using signals from crankshaft angle (G1), crankshaft speed (Ne), and engine load (Vs or PIM) sensors. Corrective timing factors include adjustments for coolant temperature (THW) and presence of detonation (KNK).

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So, this means that the ECU takes the PIM (turbo pressure sensor) signal and specifically uses it to determine it's basic timing factor. This is how the ECU uses boost to set timing maps.

However, it does not use boost to set A/F maps, which is completely seperate, as you already stated above.



Chris

[ January 08, 2004, 01:16 PM: Message edited by: Chris Dittrick ]

--------------------
http://www.gtfour.ca/
1988 ST165 w/185 engine
294HP, 292ft-lbs / 240WHP, 238ft-lbs, 12psi

Raced your Celica down the drag strip? PM me or send me an Email to: chris@gtfour.ca with your details so I can add you to the list! Celica World Race

posted January 08, 2004 06:23 PM                

quote:

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Originally posted by Chris Dittrick:
Luni,

From autoshop101.com tech article #23

quote:

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Ignition Timing Strategy
The ECU determines ignition timing by comparing engine operating parameters with spark advance values stored in its memory. The general forumula for ignition timing follows:

Initial timing + Basic advance angle + Corrective advance angle = Total spark advance.

Basic advance angle is computed using signals from crankshaft angle (G1), crankshaft speed (Ne), and engine load (Vs or PIM) sensors. Corrective timing factors include adjustments for coolant temperature (THW) and presence of detonation (KNK).

---

So, this means that the ECU takes the PIM (turbo pressure sensor) signal and specifically uses it to determine it's basic timing factor. This is how the ECU uses boost to set timing maps.

However, it does not use boost to set A/F maps, which is completely seperate, as you already stated above.



Chris

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posted January 08, 2004 08:42 PM                

quote:

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Originally posted by Chris Dittrick:
Luni,

From autoshop101.com tech article #23

quote:

---

Ignition Timing Strategy
The ECU determines ignition timing by comparing engine operating parameters with spark advance values stored in its memory. The general forumula for ignition timing follows:

Initial timing + Basic advance angle + Corrective advance angle = Total spark advance.

Basic advance angle is computed using signals from crankshaft angle (G1), crankshaft speed (Ne), and engine load (Vs or PIM) sensors. Corrective timing factors include adjustments for coolant temperature (THW) and presence of detonation (KNK).

---

So, this means that the ECU takes the PIM (turbo pressure sensor) signal and specifically uses it to determine it's basic timing factor. This is how the ECU uses boost to set timing maps.

However, it does not use boost to set A/F maps, which is completely seperate, as you already stated above.



Chris

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posted January 09, 2004 03:59 AM                         

First off, it's awesome to see us getting into some tech debate on this forum.

Clayton- For your question on how the ecu determines fuel maps, it uses the AFM to determine how much fuel to supply, completely independent of the map sensor. It doesn't need a load input because it only needs to know if it is at idle, partial, or WOT, which comes from the throttle position sensor. Therefore your fuel maps are not affected...although it may just be dumping in max fuel at that point, which is kinda proven by the AF ratio's people have found the stock engine to have on dyno's. They were extremely rich.

Luni- Take a look at http://www.autoshop101.com/ . That is where I got the quote from...these are TOYOTA training articles. They are not wrong.

I 100% agree with you about how it sets the fuel maps.

The fact is, the MAP sensor is used to set the ignition timing. However, what signal it sends to the ECU when you unplug the hose is a mystery. Someone should find that out. Have you ever watched timing maps on a computer while a car is running? It isnt just one chart, it is constantly changing because they vary depending on load...it's 3 dimensional.

I agree that the car will run, and probably just fine with the map sensor disconnected. This is because the ecu also uses base timing, crank angle, crank speed, and the knock sensors, as well as the map to set timing at a given RPM and load.

However, I can name more than a few people who have blown engines at moderate boost levels while fooling the map signal to the ecu.

Not sure what you are saying about upgrading the turbo... If you upgrade the turbo, then yes I agree, at the same PSI you will make more power on the TD06, or whatever bigger turbo it is. However the ECU will not know that you are using a bigger turbo. It will set timing maps that were created for the CT26 turbo at that psi. This might not even be a bad thing, because you are probably less likely to cause detonation on a TD06 than a CT26 at say 15psi.

So what i'm trying to say, might not be clear because of my typing , is that yes the ECU will set teh ignition maps for the CT26 and you will still make more power on your bigger turbo. This is because it pushes more air, and the ECU is able to match it with enough fuel (as long as the fuel system can handle the monster turbo). Therefore, more air/fuel = more power. Ignition timing is as it was on the old turbo and may not be optimal, but it isn't going to hold horsepower constant. Dyno tuning the ignition timing after on an EMS would definitely yield you more power though.

quote:

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Originally posted by Luni:
Chris I believe, you are wrong. The ECU does not use the MAP sensor in ANY part of the decision making process for timing or a/f maps. Again the only functions our MAPs perform are 1)providing a signal to the stock boost gauge and 2)providing a signal to the ECU to initiate fuel cut.

Thats all it does from everything Ive seen.

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Again check out http://www.autoshop101.com/ . Scroll to article #23, and scroll down until you find my quote. It specifically says that what I said is true. I only said the ECU uses psi for timing maps, not fuel. Fuel maps are set by air flow just like you said.

quote:

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Originally posted by NuclearHappineS:
rebert ...
Facts that i know

3- I know the RC cars in the UK were made to run 18psi instead of 12 by doing 2 things : (and i read this on the UK GT4 board from a guy who worked for TTE) : a) bore out the hole on the wastegate hose port going to the TVSV by a calculated amount. b) make a low level FCD by soldering a zener diode into the ECU circuit board.

Those are 2 facts. and it works on the rally car so what makes it not work for other cars is beyond me .

When i said people unplugged their map sensors and ran fine for the most part. Well that's for the most part. I know one mr2 member that said he went from a disconnected map to a FCD setup and his 1/4 mile times dropped and his car got noticably faster.

I dunno what to make of that.

Ultimately you have a knock sensor. If you screw up, the knock sensor is there for a reason.

Alot of people say the knock sensor doesn't help you because if you run into any significant knock then 1) you blow the knock sensor before the ECU does anything. 2) your knock sensor is fine but you blow the Engine before your ECU reacts.

My spiel is done

-Nuke

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Nuke,

You are 100% correct about the rally cars. They bored out the hole on the TVSV which causes the boost level to increase. They do this because it is not legal under their rules (at least back in the gt4 days) to use an aftermarket boost controller. So this way they were able to make use of the OEM boost regulator to reach higher boost levels. They used a zener diode to eliminate boost cut because what it does is clamp the PIM voltage going to the ECU so that the ECU never sees load higher than 12psi and doesn't hit fuel cut. This way they can bypass fuel cut and increase the boost without breaking the rules.

This DOES work on our cars. I know a few guys who have done it...actually I know a guy that has been involved with TTE for many years and is building a rally ST165 right now...he's doing just this. He's in Australia.

On the 1/4 mile times. Yes this is true. What the FCD will do is curve your load (PIM) signal down by a resistor or something and causes the ecu to not see past 12.8 psi...except it changes the load signal gradually all the way from 0psi up to whatever the FCD is set for. This goes along with my quote from autoshop101. Because the ECU sees less load, it will give the engine MORE timing advance, which in turn yields more horsepower. I also saw in Sport Compact Car's Power Pages (good source I know ), that after the install of an FCD on a Talon they gained 5whp. It's in the power pages issue you can buy on the shelf right now. So this makes perfect sense with what I'm saying.

As for my thoughts on the knock sensor...well my opinion is that it isn't able to retard enough to prevent damage when severe knock is sensed. When I blew my 1st engine it was toast...nothing could be done...knocked like a mother fucker.

Speaking of the supra guys and Gforce I could talk to Reg Reimer, one of the Supra guru tuners, since his shop is like 10 minutes from my house. He does tuning with the same technology as Gforce, the techtom circuit boards. I'm sure he would have some input.

I hope someone takes the time to read this. I know its long but I hope this helps explain some of the mysteries of the OEM ignition timing strategy to everyone...

Cheers all, awesome debate thus far!

Chris

--------------------
http://www.gtfour.ca/
1988 ST165 w/185 engine
294HP, 292ft-lbs / 240WHP, 238ft-lbs, 12psi

Raced your Celica down the drag strip? PM me or send me an Email to: chris@gtfour.ca with your details so I can add you to the list! Celica World Race

posted January 09, 2004 11:01 AM                

quote:

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Originally posted by Luni:
Chris I guess Im an idiot cause I dont see anywhere in that article that states specifically it uses a MAP sensor to determine timing.

It says VS or PIM.

Where on our cars do we have a VS or PIM.
And how do you associate a PIM sensor to mean our MAP sensor.

Im not being a smartass or a dick, I just want to know where you are getting your information from so I we can be on the same page here.

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posted January 09, 2004 07:31 PM                

quote:

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Originally posted by Luni:
Cause it says VS OR PIM sensors.

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