SPOautos

Ok guys, I'm trying to help someone out with thier car and need to know something about the Pettit ecu.

Does the Pettit ecu support larger fuel injectors???? I dont understand how it could, seems like if I have a Pettit with the unlimited chip and stock inj then switched to larger inj they would have to change something in the ecu to let the ecu know i had larger inj.

When I was shopping over a year ago i was told that the Pettit was good up to 13psi on pump gas and 14.7 on race fuel. I was never told anything about upgrading the fuel sys and turning it up to 16 or 17!!!!

What is the deal can you throw in some upgraded inj/pump and it run right????

Thanks,

JoeD

i think the Pettit Unlimited ECU can support larger injectors. ive seen some some people with that setup on this forum.

dclin

iTrader: (4)

If it can't support larger injectors, could you not add a piggy back fuel computer like the Apexi S -AFC or HKS Super AFR to turn fuel down?

Kinda defeats the cost savings of a upgraded ecu over a Power FC, but might be a solution if he absolutely wants to retain the Pettit ecu.

JoeD

the only downside i see of havin larger injectors with a Pettit ECU is running really rich. since you cant tune it and pull fuel out, a lot of extra fuel will be injected.

rotaryextreme

iTrader: (2)

dlin is right. You can use an APEX super AFC with larger injectors. I don't have experience with the hks one but I think it should work as well. Using the SAFC to lean it out is ok since you will not run into the fuel cut issue with this kind of device. Make sure your upgraded secondary injector is not 50% larger than your stock one. I will not upgrade the primary injector using the super afc. This kind of device is intercept the MAP sensor signal and modifies it and sends it back to the stock ECU. Let's say right now at idle, your MAP reading is 20 in/hg. If you use a larger primary injector, there is not much you can modify since it's already at 20in/hg. You can only modify the signal to 30 in/hg. So in this case, modifying the primary injector will affect the idle. But secondary is a different story since it only comes on when there is load on the engine and at high rpm. For the pettit ecu or m2 or g force or whatever upgraded stock ecu, just upgrade your stock secondary to 1100 cc/min max then you will be fine. Just to back myself up, some of you know I am working on runnning the automatic ecu in parallel with the power fc. I got an auto ecu from a forum member so I wanted to test it out to see if it works. I have 950cc/min and 1300 cc/min injectors. Luckily, I still have super afc on my car even though I have power fc already. I took out the power fc and plug in the stock auto ecu. I lean the super afc by 50% and my car still barely idles but if i do not have the super afc, my engine will be flooded by then. Now I still use the super afc for quick fuel adjustment. Much easier than fooling around with the power fc cells. One more thing is if you want to upgrade your injector so you can run higher boost, make sure you let your ecu tuner know about it so he can adjust the ignition timing accordingly. Super AFC only fools with the fuel map, nothing with ignition.

Chuck

Bucrx7

Does anyone know the timing for pettit's ignition? Is it too aggressive to run 16 - 17 psi? I'm going to swap my secondaries to 1300cc and use the HKS super AFR to fine tune it with a pettit unlimited ecu.



Tony S.

Wade

iTrader: (1)

You won't be happy at all with the drivability if you try to use larger injectors with a Pettit ECU. It would be far better to use an additional injector controller and an additional injector, or even better yet, an ECU that supports larger injectors (E6K, Power FC, etc.)

I can go into more detail if necessary.

Wade

rxrotary2_7

wade....duty calls....no pun itended

Wade

iTrader: (1)

Here is a private message I recently left to someone who was wondering about using a stock based ECU and an s-afc or similar such piggyback device:


*********************************

No, that won't work either. It does not actually have adjustments every 50 rpm, it has 11 RPM levels which can have their borders moved in 50 RPM increments. But this is really beside the point, even if it had adjustments every 10 RPM, it wouldn't allow this setup to run properly.

Let me try to explain this. Sorry, but it will be wordy.

It is all about the stock ECU's (or reprogrammed ECU's) switch from pri to primary+secondary injectors. When the two primary injectors hit a certain duty cycle, all 4 injectors are then utilized but the duty cycle is reduced to about 39%.

Now put larger secondary injectors (or primary injectors, it really doesn't matter, the same problem exists as long as the ratio of primary to secondary injectors is changed from the stock 550:850 ratio). Leave everything the same and everything will run fine until the ECU turns on all 4 injectors. Then things will be far too rich because the new large secondary injectors will be delivering too much fuel.

Enter a PMS, S-AFC, or any another piggyback type of fuel computer. You think you will be able to dial the fuel down after the injector transition and make the car run right. Let's imagine you have a really advanced unit that will allow for really, really high resolution with both RPMs and Load. You get the car warmed up, drive around for hours tweaking it, and you think you have it running pretty well. You're pleased at this point.

You stop to get something to eat and hang out with some friends. A few hours later, you leave, expecting the car to run just great. Well, it's about 20 degrees colder outside now compared to earlier. The car is bucking at light load at some transition areas. And at other places, you see the car is puffing black smoke from being too rich. Why is that? Well, intake air temperature is an input to the stock ECU, and since the air temp has changed since you last tuned your car, the changover is occuring at a slightly lower RPMs and slightly less load than earlier. Hmm, you make a few small adjustments and it seems to run well again.

The next morning you get up to go to work. Start the car, it runs fine. You start driving down your street, and the car is bucking wildly sometimes and puffing black smoke other times. Why? Well, now, not only is the intake air temperature different, but the water temp is playing a big role in the injector staging too.

The end result, either you get tired of trying to make it work right and switch to something that really supports larger injectors, or you live with bad tuning. You can just take the shotgun approach and make the car too rich everywhere around injector transition, which would solve the bucking, but the car will still miss and hiccup from being far too rich at times, and you will also have a less than ideal power curve because your a/f ratio shoots down into the 8.0:1 range and various places throughout your powerband.

If all you do is drive around at less than 3K RPM and occasionally give it full throttle and just run through the gears, this might be okay for you. However, if you are like most people, you typically use a variety of RPMS up to 4k or 5k and lots of different loads and throttle positions when driving, particularly "spirited" driving. If you are like this, you will never be happy with any type of larger injectors and a stock based ECU setup.

In descending order of desirability, if more than about 360 rwhp is desired, I would use these alternatives:

1) Programmable ECU that supports different injector sizes (Power FC, Haltech E6K, etc.)
2) Programmable ECU or stock-based with piggyback, and either higher fuel pressure from an adjustable or rising-rate regulator, with bigger pump
3) Stock based ECU or stock-based with piggyback, with additional injectors and separate controller

I would really only consider #1 if I wanted things to work the best and be the least amount of trouble.

Wade

rxrotary2_7

ok Wade
i see what you are saying about the stock based ecu problem. i was just curious as to the real reasoning behind it. (ps..good explination)
tell me what you think of this set up i am planning on doing. i am using the pettit ecu. and a rp fuel pump as of this moment. (fuel wise mods) what i want to do is add 2 additional injectors keeping my ecu and adding a halech f5 into the mix. i am planning on running an entirely different fuel system for my additionals. i already have an extra rp fuel pump, injectors (i will be using 460's) and its own dedicated fuel filter and lines. i am not sure of what future goals with the car are as of right now, but i can never keep a car at the same "level" it is at for very long. this is not my "race car" (i have an rx2 dedicated to that...almost) , just want a fast street car. at the stage it is at right now, it can always be turned back to "emissions legal" by swapping in the stock cats, and if i run additional injectors, this will also not be a problem IF the issue ever comes up, but by going haltech, it would be a BITCH to get it "legal"...do you see where i am comming from? if it makes a difference, my other mods include intake, dp, mp, catback, pulleys, fmic and apex avcr. i run 12* all the time right now, and wanted to run like 15 safely. i do plan on upgrading the turbo eventualy, but not for a while. i want to cook the stock twins first. also, if i do go single, am i required to change the ecu i am running?

Wade

iTrader: (1)

This is a big one, so many questions.

If you want to run 15psi and you have the Pettit unlimited ECU, you shouldn't need more injectors. Before going through the trouble of adding injectors, try a wideband lambda meter and see if your a:f is good, it probably is. If it's in the low 11:1 range at full boost in 4th you don't need to worry about fuel.

IF you need more fuel, there is no reason why additional injectors won't work. I don't know the features of the F5 but I'd assume it allows several RPM bands and a few loads so you can ramp up the fuel from 0psi up to your max boost. Should work fine.

You could also bump your fuel pressure up a bit and get extra fuel.

If you go with additional injectors, I'd suggest welding or pressing the injector bosses into your lower intake manifold rather than using an intake elbow like the GReddy. The GReddy will work but you aren't guaranteed proper fuel distribution to the from and rear rotor and you will be putting gas before the throttle body, which means any time you take that stuff off it will have gas on it. Not ideal or safe if you ask me.

Whether you use additional injectors or just the Pettit, at 15psi the stock injectors will be hitting 100% duty near redline. Personally I don't worry about this but a lot of fuel injection companies will tell you never to run more than 85% duty cycle (wonder why... they sell injectors??), but if you do, you really have no way to change that with the Pettit ECU. Even if you add more fuel with the F5 the Pettit will still turn the stock injectors on the same amount. I have never heard of someone having a problem with the stock injectors from running them static, if you ever find someone who says they have then send them my way.

And don't forget, nothing is truly "safe", 15 psi can destroy an engine even if there is plenty of fuel, so be careful.

Wade

rxrotary2_7

thanks for your explinations wade. you have been a great help.
i never thought of the stockers running 100% even if i did add fuel via AI's. good point. and i also never heard of anyone running them static. also, i know there is nothing that is "safe". i have been through MANY motors. (5 alone on THIS fd in under 48k miles) this is another reason i want to add injectors. figure just throw fuel at the motor to be on the safer side, and maybe be on my way in the future for any more upgrades.

rxrotary2_7

ok....i am going to be a pain in the A$$ with this post.

question 1...what is te ACTUAL duty cycle of the pettit computer on the primary injectors AFTER 4.5k rpm's?


the reason i am saking this is a good reason.
after gettng so curious i HAD to call pettit, i have found out from someone who answer the phone, that after about 12lbs of boost at WOT, the ijectors are running at 100% duty. now if i were pettit, and wanted to continue to sell ecu upgrades without damaging my rep, i would have done this on the safe side....which i fell they have done in a way...
so if what they are saying is true, then ANYONE who has a pettit ecu running anything LESS than 14.7lb of boost, is runnin to rich.... i think that is safe to say... being as if the secondaries are running at 100% and can not go any further after 12lbs. does anyone see where this is going? no? stay with me

i had a problem in the past that i never figured out wht it actualy was, but i did put a "bandaid" on it to fix it.
after 4500 my car would break up and lean out....long story shorter...i put an adjustable POT inline from the water temp sensor signal to richen up the mix via tricking the ecu to think it is running colder than it actualy is. at the time i wasnt think of the stock inj running 100% duty cycle. and after i found this out it make a light go off in my head. then where the F did te extra fuel come from, to compensate for the lean-out...duh...from the primary injectors, they are cotroled in part by the water temp. sensor. am i right? so....now comes my "theory" (which will probobly be wrong). if this is the case (being able to run the the primary at a different duty as what the pettt ec is telling it) wy cant i run the primary inj at 100% duty i it is okay for the secondries to do so? hence...more fuel availabe sitting right there in the car never being "tapped" into. and they should not run static, just as NO ONE has ever had any problems with the secondaries. wade you said it yourself, and pettit claims to NEVER ONCE have this problem or even hear of it. it seems logical to me. just add in a fuel prs riser and be done with it. this all goes back to my #1 question that pttit was notable to answer, what is theduty of the primary after the secondaries come on line? if it is true what wade said "39%" then there is a bit of fuel not being utilized that COULD be used. i kno there has to be a way to make the injector duty rise as rpms go up, i CAN figureit out if my whole theory is even partialy correct.

GOD i hope someone understands what i typed, it all makes sence in my head, but i feel as if i cant type it out right and i want to know BAD!!!

rxrotary2_7

anyone

rxrotary2_7

anyone?

nobody?

rxrotary2_7

nobody?

Bucrx7

I would also like to know too. Anyone?

maxcooper

This may help clear things up: After the secondaries come on, both the primaries and secondaries are running at the same duty cycle. 100% means both the primaries and secondaries are open 100% of the time. The 39% thing is just the point at which the transition from primary only to primary+secondary occurs.

Also, I too have never heard of anyone frying their injectors from running high duty cycle. But it does give up tuning control, which I see as a real problem if you are trying to get the car to run well. You can tune up to 93% (or something like that -- it changes with the cycle time) and then they go full open or "static" as it has been called in this thread.

-Max

rxrotary2_7

max,
not to disagree with you. but do you know for a fact that the primary injectors are also running 100% when the secondaries are? if so....
then i am extremely confused. how did i find the extra fuel to *cure*(badaid) my problem? please go back and read my last post if you dont understand my queston. there HAD to be more fuel somewhere....where did it come from?

maxcooper

Only from second-hand information, but there are reliable sources (Wade, others) that say that the transition is immediate and that primary and secondary injectors have exactly the same duty cycle when they are both running.

No map on the Pettit ECU has the injectors running at 100% at 4500 RPM. When someone says that an ECU "runs 100% duty at 12 psi" they mean that the peak duty cycle for the ECU at 12 psi is 100%, which probably occurs at 7500 RPM or so, when the load is greatest. At 4500 RPM, the duty cycle will be much less.

If you mess with the temp sensor signal to the ECU, it will result in slightly different injector signals due to temp compensation. I suspect that you were not at 100% duty cycle and that your temp compensation added some fuel and fixed your problem.

It is useful to pretend that you are the ECU in figuring out how these things work. Be sure to limit yourself (in your role as ECU) to only that information that you know. You know engine speed, manifold pressure, air temp, and a few other things. You also have some fuel map tables that someone programmed into you. You know nothing about injector sizes, fuel pressure, air flow, etc. Your job is to read your inputs and choose a value from the fuel map, apply some minor compensation values (like temp), and then hold the injectors open for the time you calculated. If someone changes the things you cannot measure (inj size, air flow, fuel pressure) you won't know about it and thus cannot compensate.

The big issue with running different sized injectors is that you can't hobble together a solution for this problem very easily because the transition logic is inside the ECU. If you increased BOTH the primary and secondary injectors by 30%, you could use a piggy-back box to apply a 30% reduction in the injector pulse width and get proper behavior. But, if you just enlarge the secondaries, you can't do that because you don't know when you are in primary or primary+secondary injector operation. You can't do it by RPM because it happens at different RPMs based on load. You could try to setup your gizmo so that it would only apply the compensation at the appropriate loads + RPMs but you will spend tons of time and never get it right -- it is a losing battle. Don't waste your time.

-Max

rxrotary2_7

just for the record, i am NOT trying to run larger injectors ona stock based ecu, only trying to understand how my problem was *fixed*. and trying to figure out the duty of the primary injectors while secondary ones come online to see if it is at all possible to "get" more fuel out of them(primary).

thanks for the info wade and maxcooper. you have been a great help. i think i understand it now, but it seems that between the 2 threads, there are still some misunderstandings with others. i hope they *get-it* also.