EFI Conversion

Curious if anyone has done an EFI conversion on their cat?

I was wondering the same thing.

Sure seems like it would improve driveability, fuel economy and performance.

The kits that I've seen are spendy; some to the point where you might just opt for a newer engine with EFI instead. But I imagine someone on here has done the actual conversion...

there have been a couple around the forums who have added a factory efi engine as I remember a bombie with a 2.3, and an sprite with a 300-6. if I had an older rig I wanted to convert, there is an out fit that makes a tbi 400 kit for just about every thing that would be the way I would go

http://www.affordable-fuel-injection.com/
these were recommended when I was looking.
1k is not bad when considering I get about 250$ for a carb rebuild

They are spendy but you get what you pay for most times. I'm sticking with carburetor after fighting ecm issues on multiple rigs in the last year. I can handle a sticking float or clogged passage in BFE a lot easier than a burned out computer.

You can count on the drivability part. Economy and reliability are very dependent on the system.

I have been very interested in this as well.

willd said:

They are spendy but you get what you pay for most times. I'm sticking with carburetor after fighting ecm issues on multiple rigs in the last year. I can handle a sticking float or clogged passage in BFE a lot easier than a burned out computer.

You can count on the drivability part. Economy and reliability are very dependent on the system.

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Were the issues due to cheap conversions or just Murphy's Law?

I wouldn't have a problem with a tbi 400 based system like gm used in the 80's and 90's. with the proper installation and a good wiring harness there should be no problems. the new obd2 systems can be tome real power producers but they are real complex and I see so many new vehicles running around with lights on on the dash. it has got so bad in my town I ordered up a maxme electronic service tool even though it's kind out of my scope of work the local shops seem to have problems putting lights out and keeping them that way.

I am surprised I have not seen an LS swap on this forum at all. It seems like those swaps are rampant with every kind of rig out there except snow cats lol

I have no use for the ls the reason you see so many gm is cranking them out as crate motors, like welfare mommas are cranking out baby's I like the old school sbc and Chrysler engines I like diesel power even better.

I did a GM TBI on a 1976 GM motorhome with an Olds 455 engine using junkyard parts and a GM 1227747 computer. We got all of the parts off of various mid 80s GM vintage trucks with 454 engines. That is one of the most common computers (ECM) and is used on lots of different cars and trucks with various engines. You need the harness, ALDL plug, knock sensor, electronic spark control module (ESC), a compatible distributor with electronic spark timing module (EST), temp sensor, oxygen sensor, turbine fuel pump and a throttle body of the appropriate size for your engine. The performance chip in the computer would have to be from an engine similar in displacement, rpm and power as the one you are putting it on and made for a 7747 ECM. There are wiring diagrams and lots of info on the web to help you wire it up. In that vintage of vehicle, the TBI system was independent of the rest of the electrical system so it is easy to remove in the wrecking yard.

We did it for about 500 bucks but the biggest expense was the throttle body which was a couple hundred bucks. The computers are any where from 25 to 50 each. Throttle bodies for smaller displacement engines are way cheaper. These use the old ALDL (Assembly Line Diagnostic Link) for trouble shooting. You can get a USB to ALDL adapter on the web for about 60 bucks and use WinALDL which is a free download to your laptop to monitor your system. You cannot however burn a new chip without specialized equipment but lots of people have them.

I sounds harder than it is. We put it on the motorhome in about 3 days and it ran like a modern vehicle. I've been running it since 2009 and it is very reliable. GM pretty much made the system bullet proof. I carry a full set of spares but have never needed any of them.

I'll never go back to a carburetor.

wbuffetjr1 said:

I have been very interested in this as well.



Were the issues due to cheap conversions or just Murphy's Law?

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Murphy. Ecm's get old, chips die, wiring breaks down, a/c ripple from Chinese diodes fries sensitive electronics, sensors die etc.

I love efi for turn the key and run, no burning eyes when following, otherwise they have a lot of drawbacks if you don't know them in and out and have diagnostic capabilities with you. Spare parts can be carried but you have to weigh these things before jumping in.

I would recommend efi for applications where it merits the swap but it's not for everyone. If you don't know your way around an ohmmeter or understand what makes them tick, you need to consider the swap carefully.

I've never had a carburetor that ran as smooth or efficient as efi, but I have had efi quit on me, leaving me with a dead vehicle.

I would argue the tbi 400 in my opinion is reliable enough to put on an airplane and feel secure voltage spikes can be dealt with yet I have seen some of these old gm computers stand up to 20 volts continuous when alternators fail the big thing is protecting your wiring secure every thing and protect it with split loom and those cheap little crimp connectors are a no no remember gm developed the system in the early 70's but it was not fielded until the late 80's there is no efi system more tested or better thought out.

We have the AFI system on our LMC1500/AMC258. I have a good carb but have not been tempted to change out the EFI. It just runs too good. It had to be completely reinstalled though. Only thing I don't like is the programming of idle and warm-up adjustments, its all in the chip very expensive to have that changed. Had to disconnect the TPS to get control of the idle.

It uses all the GM tbi parts tubinator62 described and someday I will try to build one from junkyard parts with the 7747 computer from a 4.2 V6.

For the V-4 in the Imp might use a single bore throttle body from a 4 cylinder engine, that would be trick.

I'm a little uncertain about the fuel pump reliability in the conversion.

-Pat

I realize some guys here like the GM TBI setup. But I'm not really a big fan...

I have a 1986 Chevrolet Blazer. I bought it in California and it was an original California vehicle with associated emissions. 1986 was the last year of the carbureted Blazer, as they went to a TBI system for 1987. The Rochester Quadrajet in 1986 form would make Rube Goldberg proud; essentially a computerized carburetor.

Anyway, when it developed a head gasket problem that was all the excuse I needed to replace the engine. I wanted something "different". So I bought a 1988 2WD Suburban with a 454 TBI engine. I had both vehicles handy and swapped all the parts from the Suburban to the Blazer: Radiator, engine, accessories, wiring harness, fuel pump, etc, etc. (I did add a wire to the Suburban's harness to control the torque converter lockup in the Blazer's 700R4 as the Suburban had a turbo 400 transmission.) I had the computer re-flashed for some additional performance and to control the torque converter lockup. I essentially created a vehicle that Chevrolet never built - but perhaps should have; a 454 TBI Blazer with all factory parts.

But after all was said and done the performance was disappointing. Certainly better than the carbureted Blazer, but it wasn't anything eye watering. If I had to do it all again I'd opt for a newer generation LS series motor as Chad suggests. In my opinion they offer significant benefits over the GM TBI engines. The TBI's are okay...but there are better options.

Interestingly in the experimental side of general aviation some people are using the Chevrolet LS-1. Here's an unfortunate story of one installation. The NTSB report:
http://www.ntsb.gov/_layouts/ntsb.aviation/brief2.aspx?ev_id=20110930X51940&ntsbno=ERA11FA512&akey=1

There is another option you can use with the GM TBI. A company called Dynamic efi makes a modified GM computer with a flash memory that can be programmed on the fly with a laptop. www.dynamicefi.com. A friend put one in his motor home and he has had good luck. This is a good option if there are no chips suitable for the engine you have. They supply the software and programming instructions as well as a starting point to get the engine running.
Most of the GM tbi systems use an axial turbine electric fuel pump that is capable of 100 psi or more. The pressure regulator on the throttle body runs at 13 -15 psi, so you need a return line to the tank. Some of the later 454 systems ran at 30 psi. Most 454's had 80-90 lb/hr injectors and ran at 13 psi also, but I think they ran out of them just before they switched to rail injection so switched to the lower flow 350 injectors and ran them at a higher pressure. Typical GM.
It would probably be a good idea to have a spare fuel pump available.
The advantage of the older tbi systems is that they lend themselve to retrofitting on older carbureted engines and are a true closed loop engine management system. Because they were an interim solution to the new EPA requirements of the time, the electrical system is independent of the rest of the vehicle unlike today. A semi skilled mechanic like me can wire it up and make it work.
I agree wth Snocat Nome that if you do this don't use crimp connectors for the splices. I did all of mine with a soldered birdcage splice and shrink tube. Some of the signal voltages like the O2 sensor are less than 1 volt.
,

Snowcat Pat said:

We have the AFI system on our LMC1500/AMC258. I have a good carb but have not been tempted to change out the EFI. It just runs too good. It had to be completely reinstalled though. Only thing I don't like is the programming of idle and warm-up adjustments, its all in the chip very expensive to have that changed. Had to disconnect the TPS to get control of the idle.

It uses all the GM tbi parts tubinator62 described and someday I will try to build one from junkyard parts with the 7747 computer from a 4.2 V6.

For the V-4 in the Imp might use a single bore throttle body from a 4 cylinder engine, that would be trick.

I'm a little uncertain about the fuel pump reliability in the conversion.

-Pat

Click to expand...

I had the system you describe on a 1983 AMC Eagle with the computer controlled carb. I never could get it to run right, but at the time I didn't know as much about it as I do now. I finally put on a plain mechanical carb from an older 258 and it ran fine.

not trying to dig up an old thread but I have been considering megasquirt for my cat.

I have built and installed MS systems on three of my street vehicles and they have all proven to be not only an improvement over the factory FI, but also very reliable and user friendly. bieng open source, a good do it yourself type person can find any info they might need and make any fixes or mods required. they can be setup to use almost any combination of sensors made by whoever. . . making parts avilability a non issue. trouble shooting is easy when you can see what every sensor is doing via blue tooth and a free app on your phone. or you can still use a cable/laptop for communication and tuning if you dont trust blue tooth.

i wont rant in here all day but i can promise you a well built, well tuned megasquirt would have alot of benifits over just about any carb setup or older factory fuel injection.

that bieng said i also totally agree that simplicity is key in the wilderness and a burnt component. though unlikely, could make for a long, cold hike out of the backcountry.

The throttle body injection setups have the same basic shortcoming as a carburetor: the intake tract is a wet-flow system. It still requires the suspended fuel to navigate a torturous path of 90 degree bends and velocity changes. The throttle body does a better job of atomizing the fuel at the beginning of the system (better than the TYPICAL carburetor tune that is), but the fuel still has lots of opportunity to fall (or condense) out of suspension.
If an enthusiast were to apply the same amount of research and fabrication to a heated air intake and tuning their engine with a digital air/fuel meter they could achieve near-equal performance to a tbi system at a fraction of the cost and frustration.