More FI Questions....

[KG4PAM]

I've been reading through the TOTW thread on fuel injection in preparation for hopefully converting my CJ over. The info I'm looking for may well have been in that thread, but I must say I didn't read every post on each of the 30+ pages in detail. Hopefully some of you can shed some light for me.

I currently run a 304 with Edelbrock intake, Performer 1405 carb, Duraspark dizzy with large cap conversion, MSD 6 series CDI, and MSD Blaster TFI coil. It runs fairly well, I just want to go injected to increase all around driveability and mileage.

Of course, the golden standard would be MPI. I am not wanting to spend the ~$3k for Edelbrock's system. I seem to remember seeing info several years ago on swapping a setup from a Chevy 305. It involved drilling and tapping injector bungs in the intake, and a fair amount of modifications to get it tuned properly. Has anyone ran either of these systems?

Assuming that I won't be able to afford or deal with the MPI system, I will go TBI. From what I have rad so far, there seem to be 3-4 different routes to take- Holley Projection, Howell, "junkyard"- plus several mixes of the junkyard setup with other ECMs.

Will any of these work with the hybrid TFI/MSD 6 ignition I have?

It seems like the Howell system is well liked, but from what I've read so far it isn't able to control timing. I figure if I put a computer in the jeep I might as well let it control as much of the engine management as it can.

Holley- will control timing, except tuning is a little more difficult and may involve connecting a laptop. Apparently there are two versions- analog and digital? Or is the analog an old version that isn't made anymore?

Junkyard- more elbow grease, plus the possibility of bad junkyard parts. Much cheaper though.

I would like to think that I am fairly mechanically inclined. I don't mind crawling around a junkyard looking for parts to save money, so long as I can still put together a decent reliable system. I can also use a laptop fairly well (I do have an EE degree, even if I don't remember diddly). What are your thoughts? My main concern is finding a system which will interface well with the MSD ignition and control timing.

Thanks for hearing my soliloquy.

[gmakra]

Another option is to go junkyard with additional components you need from Affordable Fuel Injection.

AMC Jeep: Affordable Fuel Injection

They sell kits that control the spark and have are more in tune with specialty setups like you have. They will probably have an off the self BIN that will get you started.

[Happy Joe]

It is unlikely that injection will get much, if any better mileage over a properly set up and driven carburettor. My mileage went down; although the superior off road performance was worth it. Fuel injection does make mileage less dependent on good driving habits giving more consistent mileage numbers; so the mileage of a driver with poor mileage driving habits may go up.

What fuel injection does (especially multi-point) is to give superior fuel mixture control abilities to the computer. Throttle body injection is little more than an highly controlled carburettor although when properly designed and set up it can control the mixture a bit better than bug sprayer technology. Due to intake manifold runner characteristics TBI still has all of the mixture distribution problems inherent with carburetors. Non sequential multi-point injection allows somewhat better mixture distribution but the best mixture control is done by sequential multi-point injection which can, but is not always designed to, deal with each cylinder's requirements on an individual basis.

With junkyard systems the biggest, but not particularly difficult, points to deal with are;
Camshaft position interface, I just use/build a distributor that has the ability to output position information to the computer.
Fuel/mixture & timing curves/tables; use a computer from an OEM engine that has a close displacement and similar bore stroke to the intended target engine.
The computer normally provides a spark output than can run the MSD box, unless the output is for a DIS (Distributed Ignition System)

Other sensors are needed by the engine to allow it to do its job, especially the speed sensor, to keep problems minimal. These can, usually, be taken from the donor vehicle along with the wiring harness although some research an into the speed sensor signal and various mechanical adapters may need to be built (machine work may be necessary to install multi-point injectors in the manifold, if an OEM one is not available).

Before attempting injection, I recommend some study into the various OEM injection and ignition systems; their requirements, applications, similarities and differences.

Enjoy!

[1986cj]

If you want to do your own junkyard system yourself, you need to read up on the faq's from Bill USN in that article and you can find them here http://www.binderplanet.com/forums/forumdisplay.php?f=75

[KG4PAM]

Thanks guys. I will do some more research and see what I can find. I don't see how people drove carbureted vehicles day in and day out for so many years. I have had nothing but problems with them on my jeep, whether it be a BBD, MC2100, or Edelbrock (although in its defence the Edelbrock has done MUCH better than the others). It seems like there is always a vacuum leak or mixture adjustment, etc. that has to be tweaked. I am not excusing myself from the blame though... If I can let a computer control things I should get more consistent performance, as you said.

Thermodynamically and aerodynamically speaking the carburetor should always be more efficient than injection. Just in my experience- Arrghh!

I just wish I had the money for a diesel conversion. A turbine/electric hybrid would also be interesting.

[jfwireless]

MY mileage went from around 12 to 18 with a junkyard TBI install and the EBL Lockers board. The EBL lockers board was the difference, able to tune on the fly with improved TBI programming and more fuel table resolution.

I also had the 304 with Edelbrock intake and the 1405 carb before the TBI install.

Jim