Hello,

I'm seeking info about above mentioned ECM. I've understood that there is wide possibilities in modifying that boxes program when the engine itself is altered heavily.

I have a following combo:

I have a DIY EFI in a Chevy Vega with the above mentioned ECM.
The engine is as follows:
350 cid Chevrolet with Corvette 58cc ported aluminum heads (int. 1.94" exh. 1.5") and Corvette 1989 STD hydraulic roller cam( centerline 117both, dur@050 207 int, 214exh). Rockers are rollers 1.52 ratio, and the comp is now 10:1.
Bore and stroke are STD(4"x3,48"). Engine redline is 5500 rpm and I plan on using around 8-10 deg initial timing that could go to 38 total.
No intake air temp sensor or EGR, the computer itself comes from a 1988 350 TBI pickup with the last letters being AKAP.

I've made an intake manifold myself with 8 injectors on it which pulls VERY hard on the midrange, VE% being approximately 107% from 3300-5200. And I have headers and twin 2,5" exhaust on it (1000cfm rating). It has an ACCEL 1000 cfm throttlebody and a big aircleaner. I have a 4-wire lambda and the stock MAP and knock sensor and an adjustable TPI TPS. And an adjustable fuel pressure regulator with the additional vacuum steering. STD engine temp sensor.

The trans and lock-up converter are stock TH700 1988 PU with VSS still on it that came with the engine. Rear end is a Ford 9" with 3.89:1 gears and the car weighs about 2500 lbs.

I have simulations of the performance of the engine but do not want to bother you with this too much. Peak torque is 479 ft-lbs@4000, avg 407 and peak HP is 419@5000, avg 265.

My question is:
Can you help me on programming the ECM's tables for this combo ? Or advise me on people and places who could provide a custom chip maybe?
Currently I have a standard prom which doesnt work that well as you can imagine.
The engine starts though and I made a cable with which I can hook a laptop to the ECM using RT Tuner.

Any suggestions, anyone?

 

This is a DIY board, no prom begging here.........

But If you like to learn how to program your own proms this is the place to be. Read the stickies first, ask questions later.

There are company/persons who do custom programming if you search around.

/N.

 

Does it REALLY sound like I'm begging here?

Initially I asked for piece of advise for the prog. tables, didn't I?

First of all, I want to do this myself in order to learn to do it myself. I reside in Finland, Europe and there aren't people here that can help me in this case.

If I cannot do this myself then I want to know a place where to buy things.

 

You want to do it yourself- good- , read this thread, there are good info in it.

https://www.thirdgen.org/techbb2/sho...hreadid=288763

should get you started, it covers the most: equipment,tuning and so on....

Equipment you can find here www.moates.net

Check my location

 

Humm, spray.se... swedish, right? Hello neighbour! You've been in Wheels Mag leaning over to your engine bay in a pic? If that is the case then I've seen that article.

I'll take a look at your site, was also wondering whether it would be a good starting point to use 1990 MAP-based Corvette's tables to begin with? Since my engine is not that exotic.

Postscript: It was Power Mag... same pic.

PS2: Location:sweden, ahum..

 

yes its me..........Now my engine is bigger and so on but its off topic........

You could start with a stock vette tables or why not the Super_AUJP code developed by people here, do a search and you will find info about it.

*You may have to change ECM to run 8D?? I dont know but someone here does, for sure or you could search...

There is alot of help here for the 8D code.

Ps there a maybe 8-10 people now in sweden that can do Proms for GM ECM..

/N.

 

right out of the gate, I see a problem with what you're attempting to do. the '7747 ecm is designed to run 2 TBI injectors,which you are using to run 8 injectors.

I'm assuming these 8 injectors are in a port injection type manifold(1 per cylinder). If this is the case, it will be more difficult to tune with that ecm than it may be to find a '7730 ecm, which was designed to run in an 8 injector port type intake. You can then run the $8D code- camaro and corvette TPI based. the '7730 ecm is probably the most widely used ecm other than the '7747.

the problem in what your attempting is that the firing scheme for the injectors is different for TBI than it is for port injection, so it may run, but tuning will be tricky.

going to a '7730 ecm will also give you faster ALDL, so data logging is more useful, or I guess I should say quicker.

 

I agree 100% on going to a different ECM, the 730 (as posted above) is pretty good to work with.

Now if I were you, I would get a 727 ecm (730ecm in a underhood version, thats weather proof). It cam in gran-prix's and other gm cars around 1990. I would think it wouldn't be too hard to get your hands on the 727ecm, with a mostly complete wiring harness.

Your setup is just begging for some more cam, something around 230 deg @ .050.

 

Lot of reply's and info, this is a good thread already.

jwscab, why exactly do you think driving 8 separate injectors would be difficult to tune with 747?

I studied some TPI setups (dont ask for ECM numbers, cannot recall) and they are set the same way; two separate 4-injector drive sets and only duplicated "drivers" in the box that are wired the same way I did to my 747. So 747 has two inj. "drivers" and TPI has two duplicated "drivers". And when I asked from GM that which kinda resistance should the injectors have, they said "Anything above 1,7 ohms." Seems weird, but works.
BTW, what's the real english name for those pieces inside the box that give impulses to injectors? These "drivers" I'm referring to?

I don't see the problem, at least yet since I'm not that far out with this stuff than you gentlemen.

Low C:
I've tried and tried different kinda cams with Eng. Analyzer Pro and with my selfmade intake there seems to be none better than the original stick. And I've tried...
Now you think: simulation, who's this dumbass?
I've learned that program to be somewhat accurate. Even Chevy High Performance tested this simulation prog and found it out to be very accurate.

 

its not a problem of driving the injectors, actually, the TBI injector controllers (in the '7747, a chip almost exactly like the LM1949, national semiconductor) can drive the 8 injectors easily.

its a problem of firing schemes. the TPI and TBI fire the injectors at different times and rates. so yes, it could work, but the tune will be tricky, as I mentioned before. the accel enrichment and vol efficieny tables are also not optimum for port injection, really, they're not optimum for TBI either, but that is whole other thread.

the $8D is much more geared to what your doing, if you are doing port injection. the code is designed for this a little better.

so, to sum up, the '7747 will give you:
wrong firing scheme for injector layout
slow aldl
code not designed to run port injection


the '7730 will give you:
later code, deisgned to run a port injection scheme
faster aldl
more control (fans, vats, etc)
most importantly-more people using this format, so you can get help from many more people with experience with this ecm.

also, to clear up one other item, the '7730 is the in car ecm, the '7727 is the underhood weatherized version.

hope that makes it a little clearer. I realize some of these things might be harder to get at your location, but a little leg work now will save alot of tuning headaches, if you can help it. the suggestion for the '7730 is made becuase its a factory implementation for what you are trying to do.

so, hope that helps.
good luck!

 

Hello,

the thing is running now with an emulator and without a prom for the first time.

Glad I have good friends who need same things and have electronic capabilities as I don't have that to much but I am learning.

We noticed the difference between the two injectors programs. But then again, the original intake setup is a double plane intake with a small rectangular hole in the intake approx. 1 1/2 inch beneath the butterflies. And in a 45 degree angle.
Now, somebody said that the Inj #2 is only "supporting" Inj. #1 then I dont believe that. That little rectangular hole sure will not be able to provide enough fuel to the "other" side in a double plane intake.

Here's the car:
http://v8.kapsi.fi/v8album/Hot%20Rod..._5834.JPG.html

Here's some interior:


Here's a pic of my engine:

 

Oh sshiiittt..., they came too big.

How do I correct this?????

 

A smaller engine pic just wouldn't be the same.

You need to resize the pics in a pic editor program and then post them.

There is a thread around here for repinning a 7747 to a 7730. So a harness change isn't required.

Edelbrock had a system that works just like what you are doing. Least I think they did from what I've seen around here.

Maybe Grumpy or JPrevost will see this and comment.
But from the comments I've seen, it doesn't work the greatest using a TBI ecm for port injection.

If you can't get a 7730 for cheap (to you) over there.
Ask around here. Somebody might help you out.

 

Well,

I'll have to take that 7730 into consideration.

First tests of the car resulted that the TH-700 gave up...

Lot of work but power was present so that's not such a big deal.

 

I noticed your injectors are rather far from the ports. This could be why the "wet flow" TBI computer is actually running the engine. That and the fact that you've got a really mild cam.
I just got finished swapping from a 7747 to a 7730 in a friends truck that had the zz4 crate motor. It took me honestly only 4 burns to get the truck tuned really well for idle and part throttle. It's even strong on the top end that I put of installing the wideband for a while. Oh, and really it was more like 3 chips, the 1st one was stock and had VATS but trucks don't have VATS hence a no start .
Convert to the 7730 and it'll be much easier in the long run.
There is a thread on this site that details the exact pin swaps needed. You also have to remove the ESC and use a resistor and jumper to get the knock sensor working. The reason for this is the ESC module (knock filter) is built onto the 7730's memcal so the knock signal goes directly into the ecm.

 

Ok,
thank you JPrevost.

The reason why injectors are a little higher in the in the intake is that I wanted to homogenize the air/fuel stream and keep the fuel a tad cooler in the process. And the injectors are aimed downwards to some extent...
I know, these are not "strong" reasons to do it like that but I'm happy with it.

That 7730 sure sounds intriquing, who sells them and what's the price? Who can I turn to? Suggestions?

A friend of mine says he could get those 7730s for about a 200 $ a piece but im not sure whether the wire connector frames are in the price. Or are the two connectors (24pin and 32pin) the same?

I do know that I have a mild cam but I REALLY like how it is able to fill the compression cycle. 200 psi is the calculated pressure, thanks to a large lobe separation.

 

Check out ebay!

I've bought several 730/749 on ebay, just ask if they have the connectors.

 

Now since I don't so this conversion on a regular basis I can't give you the complete run through. Basically there is an extra plug. The 2 on the 7747 will work in 2 of the 3 plugs on the 7730. The 3rd "yellow" plug can be made from just about any other plug, just look for pictures and you'll see that with a little bit of grinding they'll fit. That's how we did it. Also, be sure to get a memcal and all the suporting hardware. It does seem like a large initial investment but I can't stress to you enough how much better the port injection runs with the $8D code (7730 and 7727). I tried working with the 7747 and it was rather frustrating to make changes and not see any improvements. I can't say tha tthe 7747 won't work well for you if you tune it but you'd be venturing deeper than anybody else has which leaves you alone in the tuning world.
BTW, I love the way you did that intake, very nice for flow distribution!

 

Thanks JPrevost for the comments.

So choices are now 7730, 7749 or 7727.
What's the difference between these? I definately want to run the engine with MAP and not MAF.
So, in your opinions, would you prefer 7730. And is the 7727 ONLY weatherized version of 7730? Nothin more, nothing less?

And also JP, thanks for the nice words about the intake. The flow distribution was the key factor for me making the intake like that.

 

And is the 7727 ONLY weatherized version of 7730?

Yes..........

/N.

 

The 727 runs basically the same but there were a few differences discussed in recent posts.

One negative on the intake that I can see, is the likely fuel puddling that will occur in each plenum. Even though the injectors fire towards the valves, the waves will send plenty of fuel droplets and vapor up to the plenum. The low cool spots will collect fuel at high loads. Once you let off the throttle though, it'll vaporize quickly and get sucked in. This may show up as rich at trailing throttle, or lots of exhaust backfire. It probably won't be as bad as I say though. Looks killer, and looks powerful.

 

GTA324,

may I ask you why you will convert 7730 --> 7749? What is gained?

RednGold,

you are right about the fuel puddling. When I had a rich mixture and drove it, a frind of mine was behind me and said whenever I let the gaspedal off there was a "foxtail"

I tuned fuelpress, and we did changes to the programming and it helped considerably. I haven't managed to get it to run lean enough but my estimation is that it MIGHT backfire a bit but only little, if any.

But now I'll get the tranny off and slip in a built 700 and after that I will post new Qs if you gentlemen have time and possibility to answer I'd sure appreciate it.

 

With the 749 I can run 8 p/h injectors.

I run the $58 code now in the 730 but when I start tuning with the blower I will upgrade to p/H and 749.......

/N.