see sig, im still working on getting it tuned correctly, i was hoping somone could give me a rough esitmate, im going to be needing a new tranny real soon ;(

 

How much boost?

 

I like the dyno myself. No guesses- just real world answers.

 

im trying for 12 pounds of boost, but with my compression ill prob go with 6 pounds.... Sorry i forgot to include that earlier. as for JB97C5 if i had a dyno in my garage i wouldnt be here asking these kind of questions....... do you have one i could use ?

 

Darn, I just loaned out my portable dyno. Wheel dynos are typically not that accurate. It depends on how smart the operator is and what the quality of the dyno is. Engine dynos are good.

Your best bet is to do a search here at TGO for "gncalculator.xls". It will give you an HP estimate. Taking it to the track and weighing it and making some runs will give you a better HP estimate. I prefer the track for HP estimates. They are rough estimates though. It all depends what kind of bragging rights you need. Wheel dynos are the best because you just play with the drivetrain fudge factor. At the track, you play with the drivetrain factor and wheel spin fudge factor. Both are good at giving you a reference when trying to tune the engine though.

 

I use desk top dyno to estimates mine it put me at 400 hp and the car ran 12.88 @108mph
So it was probly +or - 20 hp or so. I have now installed a larger cam and a blower 4psi.
Desk top dyno estimates 575 hp 602 ftlb. Its not complete yet so I have no real life data Hard for me to believe I will make that much power!
My set up is .060 over 350, 10-1 compreshion dart sportsman II heads. Custom cam
Int. 230 560 exh. 235 565 on a112 lca. Hevaly moded edlebrock hi/flo. Base and runners 52mm tlb.

 

You should be way out of fuel… you should have enough engine that at 12psi boost you’re capable of making just over 600hp, but you only have enough injector for about 400.

 

What size injectors should i go with, some 42lb SVO's ? I thought 32 would be good for what i have, at least thats what was reccomended.....

 

Well, if you’re really in that hp range I’d probably be looking at some 50, 55 or most likely the newer 65pph Delphi injectors. Of course, a lot of what your decision would be based on what you're doing for engine management now.

 

Yeah, for 600HP with a BSFC of .55 to .65 you should use injectors that size. If you plan on using the batch fire ECM you are much better off getting Peak&Holds and using a batch fire ECM that can fire them. SEFI is another story......it would work fine with 65#/hr saturated injectors.

Just to give you an example. I am running an engine with much less HP than yours with 42#/hr saturated injectors and the idle pulsewidths are in the 1.2ms range with a 730 ECM batch fire. They are very sensitve at idle. They work fine at WOT, but that is on an engine making less than 500 FWHP.

 

By that do you mean that you had problems with them at idle, or just that tuning them right took a little doing?

That is pretty much the only reason that I’m dumping my TPI intake… seems like above 36pph with a stock ecm you enter a no man’s land that you get all sorts of different replies/answers about what works and what doesn’t. Switching to the single plane it will be a few minutes to swap injectors, that way, worst case if I have to I can put some 36’s and open the wastegates to pass emissions or drive it a longer distance, and it should be much easier to experiment and find what it takes to make what work.

FWIW, we’re running 77pph injectors (high Z) in my brother’s LTD with a high impedance driver (haltech), and their idle and part throttle is probably better then it was with the 36’s they replaced, an transient response was much better since the 36’s would go to 100% DC when you tipped in and crossed the torque peak (though they were fine at WOT/at the track)

 

There really wasn't any problem with the injectors themself. In terms of tuning idle, the problem really was with my tuning method. I was making VE adjustments for 25ish size injectors and it would swing the AFR from very rich to very lean. They are sensitive in terms of VE table changes at idle and part throttle cruise. Once I flattened out the VE at idle it helped a lot. Small .1ms BPW changes make a decent size change in AFR.
That is with the idle set at 800 RPM, -4* overlap at .050", LT1 intake, stock HEI with MSD2 coil, Autolite 24s at .030". If you ask me, the real problem is with the HEI and MSD2 at idle. I think with a better ignition it would idle at less RPMs.

I hated the Ford 42#/hr injectors at first. Now I like them.
When I started asking about injectors around here last year I got all kinds of answers. It all seemed like VooDoo magic to get them to work right with a batch fire ECM. I also got the impression that anything above 36#/hr with batch was questionable. I am running a 730 ECM with $58 BBZB code that does two injector squirts per engine revolution (all 8 cyls fire). The idle BPW at 800 RPM and 24* BTDC timing has BPW of 1.2 at a 14.7 AFR. Going to a 13.8 AFR yields a BPW of 1.43ms. So it all comes down to time resolution that the ECM can do. I think with 42#/hr saturated the stock ECM has enough resolution. Some people don't think the stock ECM has enough resolution.
Once I get some of these projects done I want to make up an OP AMP setup feeding an A/D on an Atmel AVR chip so that I can capture the actual voltage of an injector firing. I am curious how much of that 1.2ms takes into account injector open and close time. I also ran the 42#/hr on a bench setup to look at the spray pattern. I was worried that they were not opening sometimes with low BPW. The pattern looked fine by eye. I picked up some use 55#/hr Siemens/Deka Peak and Hold to try later on this summer with a modified 749 ECM. There is no rush on that though. Changing the injectors is simple on the LT1 intake.

Is the ECM in the LTD Sequential fire or Batch fire? Yes, bigger injectors are better for transient throttle (AE).

The thing that bothers me with big injectors is the small BPW at idle and cruise. If an injector starts to get clogged in the least bit it is going to throw the AFR way off for that cylinder. I have been playing witht he $58 BBZB code on the bench to figure out the single fire mode (i.e. Quasi-async mode). If I could fire the injectors single fire at idle and part throttle then I would be very happy with either the 730 or 749 ECM. I think the 730 with $58 and saturated would be a great setup because it would take my double fire 1.2ms times and double them to 2.4ms in single fire. That would be about perfect. I like the 730 because they are cheap and widely available. I paid double the price for the 749 ECMs. I bought the Ford injectors because they were cheap compared to Deka, Delphi, etc. saturated or P&H. Other ECMs are better, other injectors are better but the stuff I ran fit the budget.

By the way, I did think of trying the Megasquirt EFI with the Ford 42#/hr. I was going to try the alternate fire batch mode. It would have given the 2.4ms BPWs that I was looking for. It would have not given enough fuel for WOT (8ms BPW) at 5800 RPM. The Megasquirt code doesn't have a way of transitioning from single fire to double fire. Yeah, I could have added it (C code) but I like the stock GM ECMs better because of Limp Home mode and the extra Inputs and Outputs available.

 

What makes you say that?

I guess that the real question is at what point will the GM ecm not go for any shorter a pulsewidth as a limiting factor. If the injectors are just too slow it would be a matter of hitting them with a higher current/voltage to open them faster, of course, I know that the 77’s that my brother is running are fast enough to idle on a 5.0 with a fairly mild cam, low compression and locked out timing.

Batch fire

Huh, I’d love to know some details there… I played with turning it on and off when I was messing with the ‘165 ecm and I honestly couldn’t tell the difference in the way the car ran. Somehow I was under the impression that quasi-async only actually did it if it had to, and still went synch most of the time, of course, I’ve come to the conclusion that I can’t seem to pay attention to the ecm stuff long enough to weed out real info (well, I would argue that it’s not really a problem with my attention span, but that’s another argument altogether).

I just snagged a few ‘749’s so I’m probably going to pop one into the place of the ‘730 running $58 in my formula whenever I get the drivetrain straightened out in it. I was figuring that the slightly beefier injector driver circuits might be worth a little bit at idle with bigger injectors… I guess I’ll see.

The whole MS thing rubs me slightly the wrong way… seems like I know more people that I have some reasonable faith in that can’t get them running right (I actually know an EE that works days on guidance stuff for space and weapons that can’t get his working correctly) and the ones that I know that did never keep them on the car for more then a few months before they decide to move on to something else…

 

I think it would idle better with a better ignition because after I cruise with it and come to stop, it idles at 14.7. After idling for some time it will increase to 15.2. I think it starts to misfire. I could be wrong. It seems to want a little more fuel so I have been tryin 14.3 AFR at idle and it climps up to about 14.7 AFR. That is where I have it set right now. It could be the whole "LT1 intake idle" problem that I have read about. I have yet to experiment with that theory.

It is not really how low the GM ECM will go. It is how fast the injectors open/close. From what I have read it takes about 1ms for them to start spraying fuel and another 1ms to be completely open. The GM circuit is good for getting them to close quickly. In the complete injector on time, 1-2ms is wasted in turn on time and about .5ms is wasted on turn off time. An ideal injector would have allowed that 1.5ms to 2.5ms to be used for BPW adjustability. With that, the ECM could have less resolution in BPW times. The ECM and injector go hand in hand. The ECM needs better resolution with big injectors and the injector needs fast on/off times.
At one point last Fall I was thinking of trying a higher voltage on the injectors to get a faster on time. I couldn't find any specs for a real max. voltage on them. Also, a higher voltage is harder on the turning off circuit (inductive spike) and I couldn't find info on just how hard the GM circuit could be driven and dissipate the extra turn off heat. In the end, it wasn't worth it. The simulations showed I would only gain about .3ms of time.

The ECM proabaly does single fire or async fire rather well. The batch fire is only a problem if it tries to do double fire batch all of the time (2 squirts per 720* crank degrees). If it does single fire (1 squirt per 720* crank degrees) or async fire (one squirt per XX msec) then all is fine at cruise and idle with large injectors.
With my setup I have 1.2ms idle BPW with double fire. It would jump to 2.4ms with single fire. Since the idle is at 800 RPM, then a complete 720* cycle is 150ms. With batch fire it squirts every 75ms. With single fire it would squirt every 150ms. That seems like a long time between squirts and may cause an erratic idle if I ever figure it out and use single fire.
Async mode on the GM ECM checks every 12.5ms to see what the BPW would be if it fired. Since the engine likes 2.4ms of fuel per 150ms of time, then I could go to asynce and pick a min. BPW of 1.7ms and it would fire the injectors every (1.7/2.4)*150ms = 106ms. I chose 1.7ms because that is on average a good min. BPW for saturated injectors. Having them squirt every 106ms is much better than every 150ms.
I am guessing the LTD is doing single fire or asynce at idle.

I really don't have any details yet. I have read about the mysterious quasi-async $58 stuff at the DIY PROM board. No one gives a clear answer and most spread false info about it. From reading the BBZB $58 code it just seems like plain single fire so far. Don't quote me, I am still trying to figure it out. Yes, it is supposed to do quasi if it has to. I have been playing with the code on the ECM testbench trying to get it to enter quasi and have yet to do it using the info from the P4_turbo_Sunbird doc. I have been reading/commenting the code to figure out how to get it to do quasi mode so that I can try it in the car.
Don't worry about the attention span. Reading & commenting code is quite boring. For example, I spent 3 hours last night writing out the GM 2D lookup table (interpolation) code and drawing pictures of y=mx+b and figuring out the binary way of doing it. The return for 3hrs of time was very minimal. That time would have been much better spent finishing up the turbo truck intercooler. But I am cheap when it comes to car stuff and use a $20 ECM with the cheapest usable injectors I could find for my HP level. So I am stuck with figuring out how to make it all work. It keeps me out of trouble I guess.

I have a few 730 and 749 ECMs for current and future projects. The 730 and 749 are similiar. If you pull the cases off you will see the PCBs are the same, but the chip population is different. You don't gain much with a 749 running saturated injectors. The 749 is a must have if you run peak and hold injectors (still need to change the inj. current sense resistors for V8). The 749 circuit will not act more beefy when compared to the 730 ckt with saturated injectors. The ECM injector FET has a resistance on the order of less than .1 ohms, so using a 749 with two FETs will allow the injector banks to see .1/2 = .05 ohms or less. There is almost zero gain in doing that. Maybe .1ms of injector time if that. The 749 ECM is great to have though because you can do either saturated or peak-hold with it. The only downside is that they using get 2x the price of a 730 at the yard. I did cave in myself and get a couple just in case.
If I remember correctly, you are running a 4L80E in the Camaro. What are you going to control that with. I was thinking about putting the 4L80E in my car when the TH350 breaks. My plan was to finally break down and run the 94-95 SEFI Camaro ECM that does SEFI and controls an "E" trans. I need to figure out how to convert an HEI to have a cyl 1 pickup in it (a late Summer project if the trans. breaks). I hope the TH350 lasts the Summer.

I think the MS is a great learning tool. It is simple and the code is freely available. I am a fan of any DIY project with the info freely available. I read throught the C code every so often to see what kinds of features have been added. The MS needs more I/O, but that is really the only short coming for using it as a real EFI. The code needs more functionality but that will come it time.
In terms of using the MS real world on big HP without knowing how to code......I would personally leave it in the box. I think it is a great EFI product, but I think it is more for the hobbyist/experimenter types with the code it has in it now. If the code was more refined it would be great for everyone. For me, it is hard to move away from cheap GM ECMs that include limp home mode and a bunch of unused Inputs/Outputs and fairly refined code. I bought the MS as a test tool for alternate bank firing the port injection. That can't be done with a 730 or 749 ECM in stock form. I can also throw it on a lawnmower or something later on so it doesn't go to waste. I really don't know yet, it may work well in the car. Coding in C is a lot quicker than messing with GM Assembly.

 

well right now im using the stock computer with a moates adapter and a prom i had somone do for me based on my sig, i know thats not the best way to get tuning done but i just dont have the money for the equpiment, id like to try and get it tuneable and running with the stock ecm, but i had been contemplating going with something like the holley unit or the MS, but im afraid that might open up an all new mess of problems if i go that route.... Right now the car idles fine when it's cool, but when it warms up it gets sluggish and nonresponsive, could be the fact that injectors are too small though.....

 

If you are running a 730 or 749 ECM you can do tuning with MonteCarSlow's NVRAM module. He was selling them for $50 shipped over at DIY PROM. It is a complete "emulator" that uploads the new bin through the ALDL link. No extra add-ons to buy. All you need is an ALDL cable and his NVRAM module. The stock chip would need to be programmed once with the NVRAM updated BIN.

Once the stock bin is re-programmed and the NVRAM module is in the ECM. You simply upload a new bin through a laptop PC with an ALDL cable. No messy "emulator" hanging out of the ECM. Right now the software only works with the key on and engine not running. As the software matures, it can do engine running bin updates RELIABLY (other external emulators usually can't guarantee that).

I have been working on a $58 BBZB code hac to use the NVRAM module with the $58 code.

There is nothing wrong with buying a chip in my opinion. You have to start somewhere. There is a lot of "hardcore DIY PROM tuners" that complain about it, but don't realize not everyone has the time, skills, or interest to play with PROM tuning. I just hope that engine running better vs. cost was worth it. If it wasn't then you might reach a point where it is worth it to get your own tuning equip. It all depends on what the cost of a new chip burn is.

Anyway, The MonteCarSlow NVRAM module is worth a look for "emulating" for $50 if you use a 730 or 749 ECM. Only certain bins are supported right now, but more are to come in the following months (I think). What bin are you using now (BCC)???