word to the wise: beware of the Pettit ECU above 13 psi, and especially above 14 psi

I've blown two engines now with a Pettit ECU pushing close to 15 psi...injectors were cleaned and flowed by RC, fuel filter was clean, 20b fuel pump

Jeff at Pettit always told me to stay at 13 psi or below unless I'm running race gas....as long as you do that I think you're fine, but a cold night (engine failure #1) and boost creep (engine failure #2) can still bite you unless you leave a margin of safety....and don't expect the fuel cut at 14.7 to save you....it won't (usually)

after 7 years of running a Pettit, I'm going Power FC with the rest of the herd, the ability to monitor engine vitals and run bigger injectors is a huge plus, I think it's worth the $800 (and I should be able to get $350 for my Pettit)

 

you like to cite this, mahjik, but I wager RTS's car was on a dynojet dyno (corrected value?), cold day, great porting....basically one in a hundred cars hit that

everyone else I have ever seen on here is lucky to get over 320

 

Lucky to get over 320? You haven't been here long enough then. I guess Oakridge was lucky to... I have yet to see a car even with stock ports running a Pettit ECU not get at least 320 from around 13 PSI. It's actually the other way around, people with the PFC typically struggle to get a good tune to get the same numbers the Pettit ECU can deliver right out of the box.

However, in the long run, with a proper tune, the PFC is a good way to go if you are shooting for numbers over 350rwhp. We have several people in the KC area running the Pettit ECU's and all doing well over 320 without issues for years.

RTS3GEN's car actually has about 50k on the motor and is tracked very hard every year. It is dowel pinned which helps, but the other thing is that he makes sure to torque the engine studs whenever he's down there. The FSM list the torque rating to around 28 ft/lbs, howver he's been doing over 40 ft/lbs for at least 3 years. I'll definitely do around 40-45 ft/lbs on mine when it goes back together. Pettit has started torquing their races motors to 50-55 ft/lbs.


cruiser,

It would be helpful if they did have AFR's for the dyno run or something to monitor the intake temps. Then you could see if you are really rich or if the IC is just not being able to do anything after each run.

I would probably start by seeing what you can get to monitor a few things. At least that way you wouldn't be just replacing parts one at a time guessing if it might fix it.

 

The PFC isn't going to fix that problem. If you are tuned for 13 PSI, and you creep to 16 PSI, it's the same thing. The ECU isn't going to automatically retune itself when the creep happens.

If you have boost creep, the ECU doesn't mean anything as a MAP is a MAP regardless if a Pettit or PFC is running it.. Whatever you tune the map for, that's what it's expecting to run.

 

But looking at the numbers for oakridge and his A/F ratios, the for 14.5 and 16 psi are in the dangerous range of 12.5 (and leaner) to 1. I'd be leary of running any car at that ratio and expect it to hold up long since the given safe value is 11.5 or less.

Tim

 

Oakridge didn't intend on running 16 PSI, his boost crept to that. However, his engine didn't have detonation and the world didn't end when it happened. Having boost creep with any ECU is bad. You are only tuned for what you are tuned for (and creep is usually defined as unwanted boost... if you are tuned for it, it's not unwanted). I'm not suggesting everyone go out and run 16 PSI on a Pettit ECU. I'm suggesting to go run 17 PSI on the stock fuel system with any ECU.

However, 400 HP has been done on the stock fuel system before. Most people don't know much about the old schoolers pushing what little bit they had as far as they could go. Simply saying you can't get over 320 with the Pettit ECU (or you are one in a billion that has done it) is flat out incorrect information.

 

I agree, the PFC will not fix boost creep, but running larger injectors provides a larger window of safety, esp at higher boost (i.e. greater than 13 psi)

anyway, I'm going with the BNRs, which have the wastegate ported...problem solved

I've actually been on this forum for 5 years, and have seen very few Pettit or M2 chipped cars exceeding 320 at the wheels (in terms of actual dyno sheets)

don't get me wrong, I love the Pettit ECU, but it's time to move on

 

do you know if he was running race gas?

 

Absolutely not.

If you have 1600cc injectors, they are only running whatever map you tell the ECU to run. If you creep or spike over what the ECU is programmed for you still can detonate.

The PFC runs a MAP just like the stock, M2, Pettit or any other ECU for the FD. The difference is the PFC can be adjusted. However, if you are tuned for XX PSI, and you creept to XX+4 PSI, you are still in the same boat as people with stock injectors and a Pettit ECU.

The only "safety window" larger injectors will give is lower injector duty cycles. However, I've been hear for quite a while and I'm still waiting to hear about a motor blowing directly due to high injector duty cycles.

You might want to take a read here:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/what-situation-do-you-have-259912/

 

He never said. You can find his thread in the Dyno/Timeslip section.

 

I think you're defending your position to retain the Pettit ECU

hey, I don't blame you, it's cheap and effective...Power FC, bigger injectors, and tuning is at least $1500

 

No I'm not defendind the Pettit, I'm telling you that your thinking of "fuel safety" is flawed. Your thinking will get you replacing your engine again even with the PFC.

People blow engines using the PFC just like any other ECU. The PFC won't save you if you creep or spike. In some cases it's worse since it ignores the Knock Readings.

 

the main reason I'm going PowerFC is: a) I want 380 at the wheels b) I want to run 15 psi reliably c) I'm kind of bored with the stock sequential twins (actually very bored) d) I want to beat every Mustang I come in contact with

 

like I said, creep will be gone (BNRs)

car will be professionally tuned to 15 psi

 

If your goal is to run 380+-, then yes a programmable ECU is the best choice. However, for those not seeking numbers like that, there are other options.

Just FYI, even wastegate porting doesn't solve creep for everyone.

 

Mahjik, as I already said, the power at 13psi isnt delivered as its shown on th graph which is "averaged out". If you can somehow overlay two power curves, you'll see that I make better power at 13psi in low revs and mid revs, up to 6000RPM (5200RPM on the graph), but then it starts bucking on both ECUs. IC was cold at touch on both runs.

Only way to get a good insight into whats going on is to get the PFC or some very expensive gauges.

Am I wrong in thinking its the ignition. Is there a way I could check the coils if they're still within specs ?

I already found a T2 lading coil which I could put in the car.

 

Yes, but it takes more than spark to make power. I'm just suggesting that if you have access to some monitoring equipment (I would assume the dyno would have some stuff like a wideband), then that will help you more than just trying to add stuff one at a time and hopefully one of them will fix or make the problem go away.

No, you aren't wrong thinking it's ignition. However, you shouldn't get break-up at 12 PSI. Here's a thread on testing the coils:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/testing-ignition-coils-spark-plug-wire-corroded-408014/

another ignition related thread:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/got-weird-spark-issue-430550/

 

I wasn't really talking about the boost creep but rather the unsafe, or what most would deem unsafe A/f Ratio at either boost levels (14 and the boost creeped 16). Maybe 12.5 to 1 isn't as bad as people think but I would feel safer at a richer A/F level.

Tim

 

I'm guessing he had high rpm ignition breakup. My graph was the same with the stock ignition. I've since installed the HKS TP and high end brakeup has disappeared.

 

Majik,

"QUOTE"The FSM list the torque rating to around 28 ft/lbs, howver he's been doing over 40 ft/lbs for at least 3 years. I'll definitely do around 40-45 ft/lbs on mine when it goes back together. Pettit has started torquing their races motors to 50-55 ft/lbs.

Is this with the stock bolts/ Can you do this on a non-doweled engine?

 

No, its a calibration problem. I revved it up to 7500RMP on each run, but on graph its shown as 6800RPM or so.

 

I don't think I would go much beyond 40 ft/lbs on the stock engine studs, but that would be more than enough.

 

Ive Spoken With Cam While Down At His Shop In The Past. He Says There Are Almost No Differences In The Way That He And Brian Richards(m2) Configured Their Computers. While I Was Down There With There With The Wolf 3d I Did Mid 320hp Range At 11.5 Lbs...

 

I heard that the Pettit ECU is tuned for 94 octane (florida gas) while the M2 ECU is set for 91 octane (california gas), this makes a lot of sense considering where both tuners are located but can anyone confirm this?

 

I just paid for an HKS TP and should be getting it sometime next week.
Lets see what it does for my ignition breakup and power.
Keeping my fingers crossed.