ForceFedC5

Hello,

While I realize this is a tuning question, I thought I'd get some helpful answers here due to the high HP aspect of it.

Does anyone know the highest HP that was successfully tuned using FI with a factory ECM that supports a 24x reluctor? Is there any benefit/can you switch to a 58x reluctor for more accurate control? I realize changing the reluctor wheel is a big deal, but not so much if you're starting from the beginning.

I realize high HP is subjective. For me I'm thinking over 1000rwhp tuned via speed density.

Curious about your thoughts. TIA!

Pekka_Perkeles

C5 Corvette engine control module or thus PCM? No, I don't know. But I'd have to guess pretty much..

No, since C5 PCM only understands 24x.

SD of course with that amount of rwhp.

ForceFedC5

Questions apply to my 2000 FRC. Just curious what the hp limitations of the 24x wheel/factory PCM are. I know the 58x is more accurate, however I'm not sure if the difference is measurable in performance and/or drive-ability. SD tune of course

95BlueBomber

I was just thinking about starting this topic. I am shooting for 1000 RWHP this winter and was debating a Haltech ecu or not.

ForceFedC5

For 1000rwhp there is no issue (I can state that from experience). I'm curious how much further you can successfully go however

DRIVER456

Im over 900hp on stock pcm 24x reluctor,on E85.about 10 to 12lbs of boost

robert miller

I was a few under 1200 rwhp in a auto car worked good...

ForceFedC5

That's getting up there! I wonder what the record is.. I bet some auto cars with powerglides are up there as well, although perhaps at that level they are using a stand alone ECU.

stevieturbo

For the most part, the trigger wheel will not be a power limitation unless the wheel falls apart ( but I'd agree the 24x is a crap design..but still functional as long as the wheel works etc )

The choice of OEM or aftermarket ecu, covers a hell of a lot more than what the crank trigger might be.

ForceFedC5

Great response. So that leads me to ask the question, what are the HP limitations of the OEM ECM with a 24x reluctor wheel? I believe the ECM's that use the 58x wheel are faster and more robust?

stevieturbo

I guess the limitations may come with things like how much injector can they handle...or what sort of rpm's can it reliably handle or is programmed to accommodate.

Boost less of an issue, as even if scalings might be incorrect, boost wont be a limitation as such in the same way many would max out a MAF and continue to push on. Although with a suitable map sensor, there sort of isnt a limit.

If the physical wheel was...is a problem, people make 1 piece billet wheels. Wheel alignment with the sensor would be more critical with the 24x than the 58x, so if crank movement became an issue that could be a limitation.

ForceFedC5

So technically, if we exclude the rpm limitations, would the limitation be the amount of time it takes for the engine to rev to redline? I realize gearing plays a factor, but if a 1000hp engine goes from 3k rpm to 7k rpm in 3 seconds, and a 2000hp engine goes from 3k to 7k rpm in 2 seconds (all numbers pulled out of thin air), at what point does the increase in crankshaft speed cause an issue where a 58x reluctor wheel would be advantageous? i.e. the PCM cant read from the 24x fast or accurately enough to safely support the application?

stevieturbo

The 24x pattern is just a **** one. Add to that the welded construction of the two halves of the wheel. And less resolution....58x is just a better design..same as 36-1 or 36-2 is a better design etc etc.

In either case, the ecu could easily read a tooth, go for a coffee break and come back to see the next tooth...ecu's ability to read, or it's speed is not an issue. ECU's and their processors operate a little faster than we do ! lol Or indeed we can even get our heads around.

Nor really is rate of rpm increase much of a concern...because rpm will rise far faster in 1st gear, than it would in say 4th gear....so is it a real problem ? I'd say not.

In terms of resolution...possibly the worst possible crank trigger wheel would be the archaic 4 tooth setup some drag guys seem to love as it offers almost no resolution for huge time/rotation periods in every revolution....but many use it and still make a ton of power.

Pekka_Perkeles

Indeed.

I nice example is the PCM's real time capability of detecting a misfire for each individual cylinder. It is based on the acceleration rate of the crankshaft after successful (or unssucessful) spark. Works nice with 24x, of course.

ysb02

Highest rwhp I've seen personally with the c5 ecu was ~1350rwhp. I don't see why it would have a limit on hp beyond using injectors it can't handle or a boost psi too high for it to read in sd mode.

Biggest drawback that I've found is the lack of e85 flex support beyond the ecu hack people are doing. The aftermarket ecus blow away even the newer GM ecus though. If you're shooting for 1500+ I'd look for a 3rd party one.

ForceFedC5

I'd love to go with an aftermarket ECU, but I dont want to lose my gauges, active handling, etc.. They do have piggy back systems but I've been quoted well over 4k just for installation.

robert miller

I had a billet aftermarket one also had it welded onto the crank.

silver408z

Have you talked to blownbluez06 about his haltech setup? He has a way to keep the gauges with a piggy back and pretty sure it was under 4k. I believe he has sold it to a few people and they installed it themselves with him supporting them.

ForceFedC5

I spoke with Bret perhaps a year or two ago. Bret definitely knows his stuff, is a really nice guy as well. Unless costs have come down significantly, it was beyond my budget.

ForceFedC5

I should also mention that my state requires ODBII connectivity to pass inspection...