TPIgirl

Sorry this is not directly PROM stuff but you guys would know this.

Later on in 2004 I'm going to be swapping to a non-computer type distributor. I know the ECM needs to still get a reference pulse of some kind so it knows the engine speed.
Which wire/s on the ECM do I connect to the new distributor?
I'm assuming I would be connecting to the tach output on the distributor or the ref signal from the distributor module. Does this signal have to be a certain type/voltage for the ECM to read it correctly? I mean I know it does, but what is the ECM looking for exactly?

Thanks in advance!

The_Raven

I may be missing something here, but wouldn't you also remove/disconnect the ECM when converting to a non-ECM controlled distributer, usually meaning a carb conversion?

TPIgirl

No it's not a carb conversion, just a distributor conversion. I still need to control the injectors.

jeepguy553

I think I see what she is talking about here. Sounds like she may be installing one of those hybrid distributors. I have one in my tool room. Basically a GM large cap dizzy but with a vac advance canister on it.
Is your current distributor a computer controlled distributor (small cap) with an external coil? I can't see the advantage in doing this, though. If you do this, the ECM won't have any way to control/monitor spark timing. Can I ask WHY you are doing this?

TPIgirl

No I'm going to use a mechanical MSD distributor with external blaster coil, but not much different from what you said.

I do have a small cap distributor now. I am wanting to get rid of the ECM control over the spark advance and do it all mechanically. Why? so I can keep a very tight rotor phasing at high RPM and full advance. I will require this a little later on.

j91z28d1

on the diagram i'm looking at its

distr ref pulse HI pin D8 ppl-wht

distr ref pulse LO pin D9 blk-red


i would guess ground lo and hook hi to the white wire like you said but i have never done this. so its only a guess

9secIROC

It wont work without a computor controlled distributor. The ecm needs the signal and pulses from the ignition module inside the CC distributor. Your only option would be to go to an aftermarket ECM with an inductive pickup option.

11sORbust

Install a cam sensor.....

11sORbust

maybe could even use the mech fuel pump spot. rig the pickup in the f/p pushrod hole and mount the magnet trigger on the f/p pushrod lobe(on the cam)....

TPIgirl

I guess I could put a crank trigger on the engine but would that be the right signal for the ECM?
What do you think about this Rbob?

MTPFI-MAF

MSD makes a distributor for our cars Part#8366 it just plugs into the original harness. And a msd Coil to replace ours is #8226

but it will still operate normally cant lock it out form the computer on this one.

11sORbust

the crank sensor is not the same.....the crank revolves twice as much as the cam/dist....the cam sensor setup on a vortec should work......

TPIgirl

No you're missing the point to detach the distributor completely from the ECM except for letting the ECM know the engine speed. I don't want the ECM controlling the timing.

So what is the ECM looking for? What voltage and is it one pulse for each cylinder firing? two pulses per cylinder? one pulse per two cylinders? anybody know?

RBob

iTrader: (1)

The distributor sends one pulse to the ECM each time a cylinder is to fire. So it will be eight pulses per 2 engine revolutions. As an example at 2500 RPM the DRP to the ECM is 1.4 msec in duration and is a high going pulse. The pulses are square waves.

As for the amplitude of the pulse, I am not sure. For some reason I think it is a 5 volt signal. The ECM has a differential input so it may not be critical.

As for hookup, the ignition module has 4 pins that go to the ECM. They are EST, REF, REF-, BYPASS. The EST and BYPASS won't be used (in your setup). The REF will be the high going DRP pulse to the ECM. The REF- is the low side or ground reference of the DRP pulse (of the differential input).

The module itself has molded onto it the letters G B R E, the R being REF, and the G being REF-. Can get the required wires from that.

To prevent a SES light disable the malfunction code for DTC 42.

As a side note, the injectors will fire on the falling edge of the DRP pulse. As it is a batch fire system, this really doesn't matter.

RBob.

TPIgirl

Excellent information. Thank you! :yourock:

Grumpy

A distributor is a distributor.
You can do rotor phasing with any of them.
Lots of work for no real gains, has been my experience. years ago when the cam grinders were alot sloppier, and flat heads were the rage, it probably helped <g>.

If your into doing the best possible ignition then you want to jump up to the LS1 coil near plug setup. A FAST eDist and some clever reworking of a dual sensor or MSD dual sensor distributor gets you the signals.

Bypassing the ignition part of the EFI is going to cost you drivibility.

To feed the ecm a dissy signal take a 1K ohm resistor off of the neg side of the coil and feed it to a LED. Take the wires from across the LED to an ignition module, where the reluctor originally plugged into the module and then leave it connected to the ecm in oem form. Then flag the ignition code in the code.

TPIgirl

Grumpy, my intent is to use a quality aftermarket non-CC distributor to handle ignition timing, and keep the rotor at perfect phasing at all times. ODB (I think you know him?) told me it is necessary because my engine is supposed to turn some pretty high RPM when it runs again. He said that with the stock distributor the rotor would be over 0.300" away from the distributor terminal when the spark fires with 30* of computer advance. He said this is one of the reasons why many people have trouble making power with TPI at higher RPM, so I need to avoid this.

I double checked the measurements on my cap and figured in 6* initial advance that would be phased correctly due to the distributor housing rotating, plus 30* computer advance which should be 15* arc in the distributor cap. I measured the width of the distributor terminal and divided by 2 (0.0825") and subtracted that from my 15* arc (0.4458") measurement and that left a 0.363" gap between my rotor tip and the cap terminal. ODB said that it would work but I wouldn't be able to run a lean A/F ratio with a spark gap like that and it would cost a lot of power as the RPM goes up. He also said the stock system
could be improved by running more initial and less computer advance along with a very wide rotor tip, but he said that won't be perfect either so I need to do it the right(er) way.

So there is why I need to just give the ECM a signal so it can tell engine speed & that's all.
Thank you for the information (to all). I will try it when the freezing weather stops here

11sORbust

U sure about that?? Everything I know indicates the opposite... Less initial advance would make the gap tighter,right? 0 initial advance would mean the rotor is directly lined up with the pole. So running less initial and more ecm timing would net a way tighter rotor phasing than any mechanical dist. Could you ask odb about all that. I know alot less on the subject than him.....

9secIROC

I used to take my old 377 small block to 7200RPM with the stock Distributor in my IROC. Never had a problem. Finally replaced it with an MSD after the gear wore out. I've see many 9 and 10 sec TPI vettes also with stock distributor.

TPIgirl

Tim
When you set initial timing by moving the distributor housing you are moving the pickup and cap terminals by the same amount in relation to the reluctor wheel. This means that rotor phasing stays dead on when you rotate the distributor body. The spacing on the reluctor wheel is the signal for the spark. The reluctor wheel and rotor move together. By rotating the distributor housing you move the pickup point for the signal and therefor add advance to the spark. Since the cap is bolted directly to the distributor housing and moves right along with the pickup, the phasing does not change.
The advance from the ECM comes about simply by the ECM telling the ignition module to signal the coil sooner. ECM advance creates the spark well before the rotor is lined up with the terminal in the cap. ECM advance is relative and added to whatever your initial advance may be. Your initial advance will be correctly phased but any extra advance comes about by creating the spark before the rotor is in phase with the terminal.
The factory tries to work around this by making very wide rotor tips on some models. They work but the quality of spark isn't so good for a serious motor.
Bo

steve8586iroc

Why would a wide rotor tip cause the quality of the spark to suffer if the quality of the components, ie.. cap and rotor, is up to the task?

Steve

Grumpy

The high rpm problem with a v8 and a single coil is TIME!. The coil doesn't have enough time for the current to build. CDI is the about the best answer, but it replaces current energy with voltage.

As you exceed, ~5K, the spark is more and more just a trigger to cascade the combustion reaction.

There's just so much data that's opinion that's been repeated so many times that people accept it as fact.

Going back to the original research before it's been rewritting with opinion added is really necessary to get to some facts about ICE.

The Secret to good spark is the spark duration. How long you can keep the spark *lite* in the chamber.

It's been out of print for years, but try and get a copy of
Troubleshooting & Repairing Automotove Electronic Ignition Systems, and THEN read Dr Jacobs Guide to Optimizing your Ignition System. It'll save you alot of work if your serious about ignitions.

Forget anything that has to do with advertizing and marketing, they're just trying to sell parts.

9secIROC

Just curious on the type of motor your building? How serious is it? 7 sec motor? 1500+ HP turbo nitrous big block? Never really paid much attention to rotor phasing, even in my old nitroused 615 CI Big Chief motor.

11sORbust

yeah...tpigirl, what kind of engine are you building??

TPIgirl

It's a L98 bottom end with a cam and ported 305 heads and TPI.
It needs to be good up to 8000 rpm.
My Page

Grumpy

8,000 RPM is just a matter of cubic money.

Numbers like that mean Carrillo rods, COLA type Cranks, and max valve curtain area. The rod tension loads get incredible at those speeds.

Just some points to ponder.

11sORbust

stock l98 bottom end and a ported stock tpi intake to 8000rpms?

JMatlock88

RBOB, thanks for the excellent information! That is exactly what I was looking for for my class project! Could you please explain to me how you calculated the 1.4ms duration for the DRS @ 2500 rpm? Can you point me in a direction as to where I can find the amplitude of this signal?

For my class project, I'm going to design a controller that functions as both a WOT switch and a RPM window switch. ...An all-in-one nitrous safetly device for fuel injection if you will.

I will use an opamp comparator circuit for the TPS switch which should be very simple. The AND logic will also need to see 3000-6000 RPM window from the DRS.

According to my understanding the chip will be seeing 200 Hz at 3000rpm and 400 Hz at 6000rpm. The calculations are shown below.

I don't mean to hijack your thread
Thanks for your advise!

RBob

iTrader: (1)

The the 1.4ms duration DRP at 2,500 RPM was measured. Stuck the distributor in a drill press, applied 12 v to the module, spun it up and scoped it.

Your 200Hz at 3 grand looks good. Go to National Semiconductors site and get the app notes and data sheets on the LM2907. It is a frequency to voltage convertor.

RBob.

SATURN5

A LM339 Quad OP amp along with the LM2907 should make up the guts of your board. Look for window comparator notes on the net. There are several good sites with info. Pots will make your trigger points adjustable, or if you prefer, fixed. Use an output to trigger a transistor to your solenoid relay.
BW

biggtime

I want to jump in on rotor phasing. I use 38 degrees base on my race car, I pull 12 degrees out when I use nitrous. I then pull another 5 degrees in high gear. So what you do is set the rotor at 30 degrees on number one. This way you are in the middle of your range. I run through the top end right around 9000 rpm, with no ign issues. Oh yeah, and thats with 16:1 static compression. MSD also makes some rotors with a extra wide tip on it.
I do not know what you are doing but your combo will most likley never see 8000 rpm. I would guess it will be done making power around 5500-6000. Just my $.02