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post #1 of (permalink) Old 02-25-2005, 02:32 PM Thread Starter
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Another 258 GM TBI post -- chip burning / files???

Hi all,
I've read up a bunch on this topic - various sources - and I'm just about ready to hit the junkyard and start compiling parts as soon as the weather improves.

The most complicated part I think most people agree on is the chip programming/erasing/burning/buying/spark&fuel tables/Howell/ALDL/laptop/cable
aspect. [img]images/graemlins/tongue.gif[/img] [img]images/graemlins/confused.gif[/img] [img]images/graemlins/crazy.gif[/img]

Now, in surfing all GM TBI info I could find, I came across a site of Triumph TR8 guys who have been playing with the GM TBI also, and they offer a chip burning service for $19.95. You give them your chip and your program, and they will put it on the chip for you. [img]images/graemlins/laugh.gif[/img]

web page

Now I know some of you have this system running, and if we could get a program together, and a programming service, we could create an easily-purchasable 258 chip for this swap.

So my questions are:
1) Am I just on the slow bus, and have you guys done this already? Does someone else or any of you offer a programming service? Is there one of you I can just buy a programmed chip from (for a reasonable cost)?
2) Would those of you with the program info be willing to help (me and others)?
3) Does this make sense to any of you? The rest of the system seems very bolt on.

Seems to me that with this critical portion, we could make a simple plug and play GM TBI bolt-on for the whole 258 community.

Post up your thoughts.
Thanks,
Pete
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post #2 of (permalink) Old 02-25-2005, 03:28 PM
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Re: Another 258 GM TBI post -- chip burning / files???

I have a question that requires an honest response......
Are you doing this because you want to have the fun of doing the chip programming (something that I can understand), or, are you looking to reallin improve the performance of your jeep.

First, allow me to point out that while it sounds like a fun project, it is going to take a lot of time and probably more money than you expect. Second, do your state emissions laws allow this?

You might be better off with a total engine swap...like maybe the small block chevy with TBI. Not only do you get about 2-3 times the HP, but you still have a chip that you can reprogram if you want....and believe me, there is a ton of info on doing this to the SBC. For what it is worth, I picked up a SBC with the auto (4L60E) tranny including wiring harness and computer for $500. I know ther are a lot of v6's an v8's that will mate to your existing tranny with little effort. If I were not swaping trannys, my task would be a lot easier and cheaper. Even so, I'm amazed at how easy the swap is....electricly.

I'm not trying to change your mind......just wanted to point out an option....

And to answer your original question....do a search on fuel injection and you will find a ton of info on the subject.
post #3 of (permalink) Old 02-25-2005, 04:16 PM Thread Starter
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Re: Another 258 GM TBI post -- chip burning / files???

Dawg,
Good questions.

A) Emissions aren't a problem - I get my GM HEI and weber carb to pass the Massachusetts Dyno test, and I imagine the FI would run cleaner than that, so it's not for that.

B) I'm just trying to improve my power some, improve my operating-at-angles, not pay $1000 for a Howell, or more for a MOPAR FI upgrade. It still seems for less than probably $300-400 and not a whole lot of time (if you could get the proper chip) you could build the whole system.

C) The part I'm trying to AVOID is the programming. I'm sure it's fun if you're into that sort of thing, but...

D) I've considered a 4.0 swap too. But my 258 is a relatively new rebuild, and my tranny is only a few years old. I don't think I need a V8, and not really interested in pursuing that. I suppose I could pull the whole motor & tranny, sell it, buy a 4.0/tranny and install that, but frankly that seems like a lot more work than bolting on the GM TBI.

Really I'd like to find a good source for a 258 Chip for the GM TBI that's not big $$$$.

Hope that seemed like an honest response. [img]images/graemlins/smile.gif[/img]

Pete
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post #4 of (permalink) Old 02-25-2005, 04:28 PM
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Re: Another 258 GM TBI post -- chip burning / files???

Very honest response....
And taking your responses into consideration....your objective is valid...who wants to get rid of a good 4.2......

I would be inclined to think that a V6 TBI with a close displacement would work without any changes....assuming you use the same sensors......

When I was considering the same thing you want to do, I did a web search and came across a web site that gave a ton of info on the chip programming...including the hardware you needed and some of the assembly code.
The best way I can describe the sites as a DIY fuel injection. Based on the info, you could build your own system from scratch...

Good luck.....don't forget to post your results for the next guy
post #5 of (permalink) Old 02-25-2005, 04:44 PM
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Re: Another 258 GM TBI post -- chip burning / files???

Curious -- what really do you want to change in the chip?
More cylinders? Use the V6 TBI. That should have fairly close to the same number of cylinders as yours.

More fuel - richer/leaner? Why? The AF fuel ratio requirement's the same, just under stochiometric - where the ECM tries to keep it. Use the O2 sensor.

Different fuel? Propane, LNG?

More or faster timing advance? A faster advance is good if you plan on launching sand drags at 5000 RPM. Otherwise it's just about right -- if you use the EST.

Higher temperatures? Are you planning on running the engine at super high temps - like 600 degrees?

Hotter air input? For the Sahara desert?

I'd put it all together, see how it runs like it is at first. Then if you want more or less timing advance, change it.

That's like the fallacy most folks do - when they swap carbs on an engine they re-jet it richer thinking it needs more fuel. Then they wonder why it gets poor mileage. Air Fuel Ratio requirements are the same for all engines. If the carb is WAY too small, they might have trouble at the top end where it can't deliver enough fuel. Just the opposite of going from a 4.3 to a 258.
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post #6 of (permalink) Old 02-25-2005, 04:51 PM Thread Starter
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Re: Another 258 GM TBI post -- chip burning / files???

Rich,
Only reason changing the chip is even a question is that it seems so many people have trouble with it, and if it just bolted on and ran great as it was from GM I would think people would know that by now. [img]images/graemlins/laugh.gif[/img]

If that were the case it would be too easy, wouldn't it? [img]images/graemlins/tongue.gif[/img]

Yes, 6=6, and I'm not looking at alternate fuels. [img]images/graemlins/wink.gif[/img]

I suppose that's the best suggestion -- just do it and see how it runs -- but I guess I was assuming that a custom chip would be required.

Pete
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post #7 of (permalink) Old 02-25-2005, 05:17 PM
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Re: Another 258 GM TBI post -- chip burning / files???

I've done some web surfing on TBI conversions. One thought that comes to my mind about using the GM 4.3 (262 cubic inch) V6 TBI system on an AMC 258 would be the using the GM 4.3 V6 TBI 7 pin electronic ignition module. The best advantage, in my humble opinion, for using the GM TBI computer system on an AMC 258 would be because the GM TBI computer could be used to control both spark and fuel curves. There is lots of information to converting an AMC 258 to use the older GM 4 pin electronic ignition module HEI distributor. It's going to take some homework, but converting the older GM 4 pin electronic ignition module distributor to the newer GM 7 pin electronic ignition module should be possible. The vacuum advance and spring / weight advance will NOT be needed because the GM TBI computer will do what the vacuum advance and spring / weight advance do. In my humble opinion, custom chip buring would not be needed if the GM 4.3 V6 7 pin electronic ignition module was installed in the older GM 4 pin electronic ignition module distributor if all the other GM 4.3 V6 sensors were used. Once all the sensors and 7 pin electronic igntion module got hooked up to the GM 4.3 V6 computer, the computer should have the ability to "learn" the 258 engine with the values available in the "Block Learn" function of the GM computer.
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post #8 of (permalink) Old 02-25-2005, 08:07 PM
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Re: Another 258 GM TBI post -- chip burning / files???

Exactly!!!!

The difference of 4 cubic inches is not going to make a significant difference!

The problem folks have from Howell is they use mechanical HEI - or whatever distributor is already there - it's not able to be controlled by the ECM. The result is often ping and detonation. Do a search on this board, see for yourself.
Use the EST type module - the 7 pin HEI distributor.
Howell doesn't even provide the wiring for it.

Make sure you use the KNOCK SENSOR with it - mount it similar to the stock one -- that's VERY important.

Howell and the others make a big deal of "recurving" the fuel curve -- "smoke" to get you to buy their stuff - it's been proven time and time again the stock original chip works the best.

Howell has no idea about engines -- they tell you to plug up big holes in the TBI/manifold's adapter with silicone!!! Even a high school kid knows that only holds for a few minutes.

They may know how to shorten or lenghten a wiring harness, but they should stick to that.
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post #9 of (permalink) Old 02-26-2005, 08:52 AM Thread Starter
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Re: Another 258 GM TBI post -- chip burning / files???

Well, GM made a 6-cyl HEI computer-controlled distributor as well. When I was 'collecting' distributors at swap meets when I was doing the standard HEI swap (mostly $5-10 each, just to have more for friends, or parts or whatever), I picked up one or two of the computer controlled ones as well. There are no weights or springs inside, and it has the additional plug for the computer connection.

Unless there's some fundamental difference in the body of the distributor, there should be no reason that distributor shouldn't mount into the 258 just like the older GM HEI that everyone swaps in.

I guess I'll go down into the garage and take a look at those 'stribs.

Thanks for your input guys!

It can't be this easy though [img]images/graemlins/tongue.gif[/img] -- why would anyone go through the trouble of using just fuel control if the whole system just drops in and works great? I'll try to research it some more.

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post #10 of (permalink) Old 02-26-2005, 10:43 AM
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Re: Another 258 GM TBI post -- chip burning / files???

Good point.....why would someone try to do it the hard way.

I'm in the middle of doing an SBC (5.7L out of a 94 P/U) to my 84 CJ.....
Once I got a hold of the schematics, I was amazed at how easy the electrical portion is. I'm taking more stuff off my jeep than I have to put back. The new harnes is going through the same hole (enlarged a little) as the original computer harness did. I'm even mounting the computer in the same spot. The following is the connections I have to make..
1. Battery
2. Ignition
3. Start
4. Check Engine Light
These last two are optional.
5. Tach
6. Oil Pressure

The hard parts are engine mounts, relocating brake lines, transfer adapters...etc.

If you found a doner vehicle....grab the harness and everything asociated with it. Just try to get the sensors in about the same locations. I suspect the hardest part will be adapting the TBI to your existing manifold. Otherwise, I know the 258 has enough holes in it for the sensor...I wouildn't be surprised if they were even the right size.

Please keep us posted....you just may start a new fad....
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