MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - I just made HUGE progress on my fuel injection!

I have finally solidified my deservance of an "idiot sign". At the end of the fuel injection wiring harness on the drivers side of the vehicle there are two plugs; one for the coolant temp sensor, one for an injector. I had this magnificent epiphany:

"I wonder if those two have been switched for the last 3 years? maybe I should peel back the rubber boot and take a look."

Sure enough! The coolant temp sensor was receiving pulses for a fuel injector, and the ECU was measuring coolant temperature based on the resistance of a fuel injector! I swapped the two plugs, and unplugged my injection system to reset everything, and when I pluged it back in, it started up quicker then ever! Now that it's running properly, my idle has dropped to 600 from about 750, so I need to reset that so it doesn't keep stalling out, but what a difference in just a few minutes of playing.

Amazing!
Justin
Justin

kudos on the insight!

wish you could make Terre Haute!

rick
rick ingram

Oh man I wish I could go too! Now I'm really excited about my car!

Will there be any summer events say... in Grand Rapids, where everyone plans on getting together?

Justin

So how does it drive now? I imagine its got about 20 more hp?
Jeff Schlemmer

It has WAY more power. It was pretty juicy before, but this feels entirely different. I can't believe how much of a difference this had made. The idle has settled in to about 900 rpm's and it sits there rock solid, so I'm content with that.

What a difference in power...
Justin

Twist is having his UML Summer Party again this year August 18-19-20. There will be some V8er's there.

Guaranteed.

rick
rick ingram

Rick - Does that mean YOUR V8 will be there??? :)))

Steve
Steve Carrick

Justin,

I'm ashamed to admit that I made exactly the same mistake when I wired up my EFi the first time round.........so two idiots out there then !

Don't they run SO much better when you get it right ?

Mike
Michael barnfather

Steve...

if the Orthopaedic Surgeon will allow me to increase the weight bearing allowance and forces put on my biceps (ruptured in January and repaired in February), I'll be able to get to work in earnest, especially since I now have the space to do it in comfort and without having to pack everything up each nite, etc!...I currently am still restricted to 15 pounds or less...and I can tell if I'm exceeding that amount!

SO ... the B/GT in GR? Maybe yes, maybe no.

rick
rick ingram

Rick, 15 lbs.?! I thought you were restricted to 12 oz. curls. :)

Congrats, Justin. Three years of troubleshooting your FI, what perseverence! I would have went & bought a carb at the Townsend V8 Meet.
Carl Floyd

I,m curious about the fuel injection talk. I have a 78 MGB and am wondering if there is a way to convert it to a fuel injection system.
TSN Tom

Trust me, I researched carbs MORE than once but I just couldn't let go of this. I was determined to either A) Defeat it or B) Completely understand why it wasn't working properly, then replace it. In the last 3 years I have gained amazing insight on the fuel injection system and now have it pretty much mastered. I'll start doing fuel mileage testing this week and see if that has improved. I'm willing to bet it has.
Justin

Moss is coming out with a fuel injection system for the 4 cyl that is supposedly 50 state emission legal!

If you're converting over an 8 cyl with carb you need to make sure your intake ports on the cylinder heads have the relief notch cut out so the injectors can fire right towards the intake valve. (I can take a picture of this if necessary, I have a spare set of heads.)Fuel injection is GREAT once you have it installed properly...hehe!
Justin

Here...Here.


Mike
M Barnfather

Justin-

Comments about the relief notch- I thought the same thing when I was convrting my Buick 215 to Rover FI & asked D & about doing the notch in the heads for me. Dan said the difference would not be worth the cost, so I ignored the issue & went ahead with the conversion. I have 2 years of driving (25,000 miles) with no problems. It is possible I have lost a HP or 2, but it runs at least as good as when I had a carb, & gets much better gas milage.

I do run the O2 sensors with a white tune resistor & milage is a bit better than when I ran the 470 Ohm resistor without the O2 sensors.
Jim Stuart

Jim,

Do you think it's down to the Lambda sensors, or resistor.?....I'n still on the green one (UK spec)..(the 910ohm resistor is listed as UK cat spec in the TVR service book)......my MPG improved somewhat when I fitted the sensors, withot any obvious loss in performance ( I understand that their purpose is to work in closed loop mode when cruising).

I'm contemplating fitting a variable resistor to see if this makes any difference to power or MPG.

Mike
M Barnfather

The notch in the intake ports is somewhat less than half the diameter of the injector, so depending on the wiggle factor the shot is likely to miss the step. OTOH, a quick lick with a die grinder after using a gasket and felt tip pen to mark the cutout is all that's needed.

I'd guess I spent about 3 years or so on the Ford EFI system but wasn't quite as persistent as Justin. I threw in the towel finally and began conversion to Megasquirt. Hope to have it running a week from now, and I expect it to run very well indeed. But you know what would be way bizarre would be if it still had that same stumble around 2 grand. Can't see it happening but stranger things...

Anyway congrats Justin. Wonderful to have a V8 MGB that runs right.

Jim
Jim Blackwood

Mike-

This is my understanding, & I may be wrong-

The O2 sensors read the oxygen level in the exhaust, determining what the mixture is- rich or lean. This infomation is acted upon by the computer and the injector pulses are adjusted to obtain the ideal mixture per the computer parameters. These values are adjusted by your choice of tune resistor.

Without O2 sensors, the rich/ lean is determined by the fuel map in the computer, again adjusted by your choice of tune resistor.

The difference is that with O2 sensors, there is constant adjustments due to the feadback from the O2 sensor signals. This allows compensation for ambient temperature, engine temperature, humidity, fuel values, and any other factors that may affect combustion.

The factory choices of tune resistors may not match your needs/goals and a variable tune resistor would be a good way to solve the issue. I would suggest some auxillery metering to measure the results of the changes. The obvious would be a O2 meter in the dash. The problem is finding a meter that would work with the Rover senders, or you could install a third sender compatible with the many meters available.


Jim Stuart

This thread was discussed between 26/05/2005 and 31/05/2005

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now