Detonation and torque converter stall

[mthibbitts]

Hi all,

Finally got my crawler dynoed.

It does have a C4 Auto, Atlas 4 speed transfer case and a GM 14 bolt one ton axle so there is probably about 35-45% drivetrain loss.

It put down 135hp to the wheels with a max boost of 14 psi and only 12 degrees of total timing. It's as much timing he could add without severe detonation. Intake temps were reasonable and I have the coldest copper spark plug I can put in this head. Its 12mm motorcycle spark plugs. 

Specs:
- Stock turbo block with CP turbo pistons.
- Essinlger SVO Aluminum head
    - About 64.5 CC 
    - Esslinger EFI intake adapter
    - BoPort 2.1 cam
- 255 Walbro pump
- Billet fuel rail and adjustable fuel regulator
- Air to water intercooler
- Stock injectors
- Stock IHI turbo

Engine runs good with no mechanical issues and ignition/cam timing is correct.  Compression ratio should be very close to stock. The only thing my tuner suggested to be the cause of the detonation is that the turbo is so restrictive its causing backpressure. I know people have put the Esslinger head on all the time, but I am sure they have never kept the stock IHI turbo. Thoughts? 

Also, my stock injectors are maxed out and could not keep up at 6000 rpms.  I thought those could handle 250 hp? Maybe the EFI intake adapter is the cause of this issue? It pushes the injectors farther away from the head and maybe atomization isn't as good hence why they are maxed out?  

With that said, what is a good turbo you recommend for this set up? T3/T4?  Looking for a quick spool up since I rock crawl this and it won't see the strip. Needs to flow good too. Would like to run 20lbs of boost or so.

 Also, what size injectors would you recommend I step up to?

Does anyone know what the stock stall is on a Turbocoupe with an auto?  I have a stock Pinto TC and I believe it's about 1600 stall which is too low (was told it was 2200 when I bought it). The engine wants to stall occasionally when I nuts it from park to reverse or drive. This started after I put the new cam in so I am sure it exasperated the condition.  I was thinking a stall of around 2500-2800?

Thanks in advance!

[Stinger]

Don't worry about the converter or anything until you get the power where it should be. It's down a LOT of power unless the drivetrain is taking up much more power than expected. As a comparison, a customer car here a few years ago running the same cam with a ported iron head and a larger turbo made 302hp at the wheels at 12psi. That same combo made 230hp at 20psi through a T5 (so about 15% loss) when it arrived (another shop was working on it). It was also SEVERELY detonation prone and it would only allow about 10-12 degrees of timing advance with 91 octane fuel. Turns out the cam timing was off a tooth.

The IHI turbo isn't the cause of the problem at that power or boost level. That's stock boost and 60hp less than stock.

Stall speed depends on how much power you are pushing through it. Until you have power dialed in, you won't know how to size the convertor, or even how your current one will act.

Injectors will likely need to be about 80 lb/hr. We sell a couple options in this size range.

[mthibbitts]

Thank you for your response and knowledge I truly appreciate it. Do you think the cam needs to be retarded or advanced? 

[Stinger]

It needs to be checked and zero'd, preferably using the "ebar" method.

I think it's currently advanced a tooth as that's what builds low RPM cyl pressure and makes it detonate.

[mthibbitts]

Thanks. Unfortunately, Bo said you can't do this with this cam as intake and exhaust are not the same. 210 on intake and 220 on exhaust. The dowel is also not in the same location either so I can't point that straight down like you could with the stock cam. No sure why he designed the cam like this.......From what I have read online with it advanced it will create more cylinder pressure. I will retard it one tooth and see what it does.

Thanks!

[Stinger]

The split duration is to improve performance so that one is understandable. I don't think he has control over the dowel location as he buys the cam blanks pre-made and then has them ground to his specs. I think the dowel is cut when the blank is made. I agree that I don't know why the dowel is where it is though.

[mthibbitts]

OK, so I retarded the cam (1) tooth. Does a tooth count as the raised portion or the lower portion or both? It was on a raised tooth and now its on a lower tooth. It definitely runs a bit smoother and sounds different and doesn't detonate as soon or as much as it did before. I am only running 92 octane and tune is still set up for 93 octane. Question, think the cam needs to be retarded one more tooth or is the ignition timing causing this? Are you able to revise the last "test 2" tune you sent me to run 92 octane or 91 by chance?

[Stinger]

A tooth is raised portion to raised portion. So it sounds like you moved half a tooth.

I have no way of telling you whether the cam timing is right now or not. It's not typically a guessing game. It's set with a degree wheel when the ebar method and stock timing mark can't be used.

Do you have an adjustable cam gear?

You just click and select the entire timing advance table and remove 2 deg (92 octane) or 4 deg (91 octane) from it to adjust it for lower octane premium fuel.

[mthibbitts]

Thank you! I will retard the timing in the ECU as suggested and see how it runs. If it detonates still I will do the E-bar method. Bo said it will get me real close but not perfect. I do have an adjustable gear. 

Thank you for your help again. Your intuition was correct the entire time. Wish there was someone local that had a bit more knowledge on these motors, but I guess it's good I'm learning as well.  

Also, engine does not stall now when I shift out of park so looks like the Torque Converter will suffice for now and I don't need a bigger turbo....yet!

[Stinger]

Good to hear.

If you ebar to verify you're on the right tooth, then you can use the adjustable gear to dial it in from there if you want to dial in a bit more torque for instance.