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MG MGB Technical - Mega Sqirt FI: will it work on a B?

Who else out there has been looking at the "Mega Squirt" DIY fuel injection controllers?

I was wondering if the B's siamesed intake ports would preclude the use of this system?

Any idea where to get individual throtle bodies? I seem to recall seeing some units from Weber, that looked like their carbs, minus the float bowl. Are there suitable junkyard throtle bodies? I see no mention of Throtle Position Sensing in their literature.

The term "Batch Firing" means that all injectors fire at the same time; How can this be? Would we not be spraying fuel all over the place when and where it is not needed. Sequential firing I can figure out, but not the "Batch" concept.

The novelty of the sidedraft is wearing out; waiting 15 minutes for the thing to warm up and run smooth. I DO NOT however want to return to the SU set-up (The su would be way to practical and do nothing to reduce the supply of surplus cash).

Pete
Pete

Pete, I don't have an answer to your question, but a couple of weeks ago I bought a Powerpro Series book, "Supercharging, Turbocharging & Nitrous Oxide Performance Handbook" by Earl Davis and Diane Perkins-Davis. The book was printed in 2001 and if you don't have the book you may want to look through it aa a book store near you. I haven't read the book yet so I cannot comment on the contents. There are lots of sources for components in the appendixes. Regards, Clifton
Clifton Gordon

Pete,
The batch injection is (or used to be) fairly common, as it was cheaper than sequential injection (because there were many fewer events to keep track of!) The idea is that on an engine, say a V8 for example, the intake valves are shut for only a very short time with the engine running. Therefore, if we inject fuel early, it will wait patiently for the short period of time before the valve opens and the fuel charge gets drawn in. Further, if we fire *all* the injectors simultaneously for 1/8th the duration needed to deliver a full fuel charge ('cause our example mill is a V8), by the time the valve opens the full charge will have accumulated. The downside is that you have no control over individual cylinders as is needed with current emissions laws.

There's a problem with injection on engines with siamesed intake ports, though. There will be a period of overlap when *both* intake valves that share the port are open, and in this case the late guy loses. The "early" cylinder will get mre of the fuel charge and will run rich, and the "late" cylinder will run lean. Here's an explanation:
www.planet.eon.net/~chichm/efi/siamese.htm

HTH!
Rob
Rob Edwards

Pete,

"Batch" or "Group" fuel injection is quite common and seems works reasonably well, although not as good as sequential.
I do a lot of work on a system called Motec and their program allows for either batch or sequential operation to be selected.
For sequential injection you must have both a camshaft and crankshaft position sensor, and separate ports for each cylinder.
Batch injection can use a crankshaft sensor only, and siamesed ports.
No sensor can only use continuous metering (no timing at all).
If the system you are looking at has no throttle position sensor, does it have an engine vacuum sensor?
Fuel injection can use either throttle position or vacuum to measure the required fuel.
Even though it is very expensive, you may be interested in looking at the Motec website. It has all the information that even expert users require. It also has a downloadable simulation program. All drawings are also downloadable.

http://www.motec.com.au

Mick
M F Anderson

Thanks for the answers. I am definitely on the bottom of the learning curve on this one. Having a good background in electronics will be a help.

Ron; I gather that a sequential system would be the better way to go for the siamesed ports. The Mega Squirt system has two channels for firing injectors; I wonder if I could use one for each port?

Pete
Pete

Hi,

After reading these posts, I was wondering if anyone has looked into the feasibility of a( pre-lambda - no o2 sensor))Bosch K-Jetronic with CIS (constant injection) but there may still be a problem with the siamised intake ports. However with an aluminum crossflow head and a K-Jetronic FI system the little beast may run real well. You would need a remote swirl pot with a high pressure fuel pump with return lines. Operation is similar to Batch system but without computer control. FWIW Alyn
Alan

I read a post or web site 2 or 3 years ago by a guy who adapted a volvo injection system to an MGB. 1 it was a lot of work and 2 it didn't add much power because the intake could not be individually tuned for ram air pressure because of the siamesed ports.
A fuel injection system for the after market cross-port head might well be a power maker.
A simpler system could be a TBI system with one central throttle body injector. There are lots of aftermarket computers and harnesses to adapt a GM Throttle Body injector system to almost anything.
Barry
Barry Parkinson

This thread was discussed between 06/07/2003 and 08/07/2003

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