Over-clocking Stock Ignition

driller

El Presidente
Staff member
How many rpms would the stock ignition be capable of providing on a modified '93 Mark VIII?
 
How many rpms would the stock ignition be capable of providing on a modified '93 Mark VIII?

Oh Jeez...

What kinda "modified" are we talking about now? :D

Jet propulsion? Mixing liquid hydrogen and oxygen like the space shuttle?

I'm no rocket scientist, but I don't think they use RPMs to measure anything on that last one... :D

:D -J
 
I've run to 7,600 on my '98 Cobra, which is essentially the same system.

but doesnt have a 4r70w to control as well....
which is where the problem arises.

The PCM can only do so much...and the 98 Cobra PCM is lightyears faster than the 93-95 EEC-IV PCM.

Lets keep this apples to apples and not tossing any orange cobras into the equation.
 
Lets keep this apples to apples and not tossing any orange cobras into the equation.

I think we could probably blend those apples and oranges with a little Malibu and Stoli and figure this thing right out... :)

:D -J
 
your limited by the factory edis on the car that only has enough to control spark up to a certain point. if you are really worried about it get a distributor and put it in the valve cover with a regular coil. the stock system will only handle so much. the 97 and 98 cars are coil on plug and are not the same ignition system.
 
your limited by the factory edis on the car that only has enough to control spark up to a certain point. if you are really worried about it get a distributor and put it in the valve cover with a regular coil. the stock system will only handle so much. the 97 and 98 cars are coil on plug and are not the same ignition system.

Yep, Scott L. here in Atlanta has that SHM dohc 4.6 motor in his gen 1, and has hit that wall too with the stock gen 1 electronics. He tried a FAST set up too, without much luck. He is converting to a COP gen 2 set up because he could never get the gen 1 or FAST to work correctly in his car. The SHM motor needs to spin 8k+ to be in the power band from what he told me.
 
Yep, Scott L. here in Atlanta has that SHM dohc 4.6 motor in his gen 1, and has hit that wall too with the stock gen 1 electronics. He tried a FAST set up too, without much luck. He is converting to a COP gen 2 set up because he could never get the gen 1 or FAST to work correctly in his car. The SHM motor needs to spin 8k+ to be in the power band from what he told me.

How much HP is that motor putting out?
 
I have heard from others and have researched enough to suspect limitations with the ignition when spinning higher rpms.

The question then becomes what is the limit and what can be done to overcome it?

I know some who have went with aftermarket ignition setups with varying degrees of success and failures.

Gen2s seem to be more tolerant of higher revs and I have heard of converting to coil on plug. This only makes sense to me if it is a coil issue or plug wire limit.

Seems to me different issues would require different solutions. I suspect from the tuning trials after the head swap that the car was having problems at higher rpms (well above 6000). I hope to soon have a dyno tune and be able to determine the new power curve and see if the car would even benefit from higher rpms. It may all be a moot point at this time to rev it higher if the power curve is falling off. I know before it was peaking at 5400-5500 and the seat of the pants dyno tells me it is still pulling hard several hundred rpms above that.

So if anyone has some insight, please feel free to discuss. :)
 
Swapping to COP is not gonna solve any issues in your case. You would be still using EDIS to run the coils.

I'll give you a complete wiring harness to run OBD II. Hell I'll give you a complete shell with harnesses, modules and whatnot. The most cost effective solution IMO.

BUT I also doubt you've reached the potential of the old EEC IV. I have a buddy here locally with a built motor and chilled vortech putting down 545rwhp at 6700 rpms.
The car runs low 11s due to traction issues. All in an old 94 car, stock ignition.
 
Last edited:
I have heard from others and have researched enough to suspect limitations with the ignition when spinning higher rpms.

The question then becomes what is the limit and what can be done to overcome it?

I know some who have went with aftermarket ignition setups with varying degrees of success and failures.

Gen2s seem to be more tolerant of higher revs and I have heard of converting to coil on plug. This only makes sense to me if it is a coil issue or plug wire limit.

Seems to me different issues would require different solutions. I suspect from the tuning trials after the head swap that the car was having problems at higher rpms (well above 6000). I hope to soon have a dyno tune and be able to determine the new power curve and see if the car would even benefit from higher rpms. It may all be a moot point at this time to rev it higher if the power curve is falling off. I know before it was peaking at 5400-5500 and the seat of the pants dyno tells me it is still pulling hard several hundred rpms above that.

So if anyone has some insight, please feel free to discuss. :)

In light of that article posted regarding the Coyote engine, I would think that engine balancing and valvetrain are the limiting factors. They indicated that to get 7k rpms, they needed the crank to be 100% balanced and needed variable valve timing. The roller rockers probably didn't hurt either...
 
I would think that engine balancing and valvetrain are the limiting factors.

I'm fairly certain it is the ignition breaking up in my case. I would have to datalog it somehow to be certain. What would I look for?

Ignition Control Module

The ignition control module (ICM) is a custom microprocessor-based thick film electronic module. The ignition control module receives engine position and speed information from the crankshaft position sensor, and desired spark advance information from the powertrain control module supplied spark output (SPOUT) signal. The ignition control module uses this information to direct which coil to fire, and controls the turn on and turn off of that coil to achieve the correct dwell and spark advance. The ignition control module also provides a synthesized Profile Ignition Pickup (PIP) signal. The PIP signal is used by the powertrain control module for engine speed information and fuel injector timing. The ignition diagnosis monitor (IDM) signal sends electronic ignition system failure information to the powertrain control module, where it is stored for use during diagnostic test mode. The IDM also provides the signal to drive the tachometer.
 
I'm fairly certain it is the ignition breaking up in my case. I would have to datalog it somehow to be certain. What would I look for?

Not sure if OBDII collects the data you're looking for. There's about 15 different metrics under the 'spark' section of LiveLink, and I'm unable to decipher what's what. I'll bet Lonnie might know. My guess would be either SPARK_SOURCE or MAX_SPARK_LIMIT. When it comes down to it, it will be limited by any of the following:

1. Can the coils provide power fast enough? (Probably yes.)
2. Can the battery charge the coils fast enough? (Probably yes.)
3. Can the coils maintain a stable, properly shaped signal? (Not sure)
4. Can the EDIS (Gen 1) or ECM (GEN 2) provide precise enough timing? (<1 degree error @ 6000rpms = >18,000 Hz...by today's standards, no problem. Back in the mid 90's, maybe not.)

Those are my thoughts. I'm guessing on #4 based on the various performance timing modules floating around out there.
 
Spark Source only tells you what spark table the PCM is running in at the time.
Will have no effect on high RPM operation other than to tell you if your running on the borderline table or the base table or some other spark table.

Max spark limit is..just what it says...its the max spark allowed by the PCM.
Again wont have any bearing on higher RPMS or not, it's just a "set value".

Those are obd2 functions, not EEC-IV
obd2 uses max allowed
eec 4 uses "wot spark", and is a much simpler easier to understand process.
WOT spark is WOT spark.
 
I'm fairly certain it is the ignition breaking up in my case. I would have to datalog it somehow to be certain. What would I look for?

depends on what the "that datalogging solution" will show you, only way to tell is gonna be to hook one up and start a log file.

Feel free to call me when you dive into this as I said on the phone.

I'm deeply interested in what EEC 4 parameters are available.

I can set up a remote desktop connection with you, and I can "look over your shoulder" at all the porn you've downloaded (joking smile)
 
Back
Top