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 - Complete 3.9EFi Hotwire system - swap for carbs?

Hi there!

Havn't posted here for a while.

Having finished all the body mods on my 67 (3 synchro) GT, my V8 & SD1 box now fits. That was a lot of work - the welder certainly paid for itself!!

Anyway, to the point!

I have a complete 3.9 EFi Hotwire injection system.

Inlet manifold, plenum, fuel rails, injectors, correct ECU, wiring loom, airfow meter etc.

The plenum, trumpet base and manifold have all been cleaned are in v.good condition. the wiring loom is in excellent condition with the correct relays. The ECU was in perfect working order when removed from the original Range Rover (stored indoors since removed). The injectors have a little surface rust on the bodies but the engine ran well.

I had planned on using the EFi, hence stripping and cleaning all the parts.
However, I have now changed my mind and want to fit the Edelbrock / Weber 1404 500CFM carb kit instead.

I have a rebuilt 3.9 with 10:1 comp ratio, high torque cam etc so would need a tuning chip / aftermarket ECU, plus swirl pot or modded tank, inj pump etc etc.

I want to get the car on the road, and also have many more parts to buy so want to reduce my timescales / costs a bit.

I had planned on putting the complete kit on ebay to raise funds to buy the Edelbrock / Weber kit.

But... Does anyone have a good condition kit they would like to swap for an EFi upgrade?

I can supply photos of all the individual parts of the kit.

If anyone is interested please contact me on the above email address. If there is no interest I will put the parts on ebay in week or so.

Paul
Paul Grundy

Paul,
You might regret selling given rising fuel prices.
According to Rogers books, you can put a stock 3.9 hot wire system onto a 3.5 engine without any difficulties. This things pretty flexible. In light of that I can't see that there would be a problem with the Higher compression 3.9.
You don't need a swirl pot, you don't need Oxygen sensors, you don't need a speed sensor.
Wiring it in is simple enough. YOu need a power supply for the computer and a wire from the ignition.
You may (or may not) decide to run the fuel pump through the computer.
If you want to oviod the speed limiter then either; don't connect the speedo to the computer (I haven't) or simply don't wire your pump through the computer, use the MG loom.
I also am not using oxygen sensors (lambda sensors) in the exhaust. As far as I can tell these are there primarily for antipollution reasons and keeping CO emmision within the capacity of the catalytic converter. The engine works very well without them. You might conceiviably get better fuel economy with them, I have my doubts, antipollution is not about good economy. Instead you need to change the tune resistor to a 446-494 (470) Ohm "green" resistor. This resistor is an "external to the computer" plug in and can be found in the loom near the computer/relays. On mine it is a blue plastic plug and a small resistor in clear shrink wrap platic in a loop of wire about 10cm long. I got a replacement from an electrical shop for about a $1.

The Manual Gear box resistor is 510ohms. You may already have one. If not, tThis is placed between pin 34 and ground. It might be an orange brown wire (check your haines Manual). You need this because it tells the computer that this is not a auto box in gear and will let you start the motor. Cost about $1.

You don't need a swirl pot in yout tank. You use two in-line pumps.
Details-
A very late fuel gauge sender ADU 3218 , which has a fuel uptake line in it, which connects to a large cheap filter (Kmart $18) , which connects to a feeder roller vane pump, which connects to a high pressure rollervane pump. This connects to the fuel rail and thence back to the old pick up point on the tank.
The feeder pump is a small high volume rollervane pump able to keep up with the larger high pressure Bosh pump but more able to draw petrol, The Bosh high pressure fuel pump can deliver high pressure but draws petrol very poorly. The feeder pump can pull through a filter up to about half a meter above the tank without cavitating and becoming noisy (I've tried this). However I would not place it much higher than the top of the tank (ie the boot) as I expect much higher fuel vapor pressure regulations in the future.
The feeder pump is made by Pierburg in germany and is called an Auto-suction vane cell pump. stock no. 12001. it can deliver 0.5 bar when used as a primary pump. It cost $95 Australian (apply exchange rate to get an idea what it might cost localy) The main high pressure pump is a Bosh one pt no 0580464070 and cost $140. You should be able to set this up in a couple of hours with some rubber fuel line and some 'bundy' tubing. Bundy tubing is fuel line tubing for your "under the car" fuel lines. Can be got from any hyrolic fittings shop. Its cheaper than rubber fuel line.
Machining the plenum-you don't have to actually do anything here except provide the measurements to the machine shop.
This will cost about $100 dollars. Just take the trumpet tray to a machine shop and get them to weld up the vacuum take offs, grind off the bumps/left over bits of the take offs and generally tidy up. Then machine 15 or 16mm off the bottom of the tray and up to 10mm off the top. You might also need to have 5mm machined off the top cover as well depending on how much clearance you need.
How much clearance do you need? Set the plenum up on the car, take out the trumpet tray from the middle. Substitute a stack of paper or wood between the intake manifold and the top cover in order that you might see how thick the stack can get and you are able to get the hood/bonnet shut.
You'll also need to cut down the trumpets, depending one how much you have machined off on the top of the tray and the top cover. Before haveing any work done to the trumpet tray do measure the height difference between the trumpets, write this down somewhere. After you get the tray back then cut these trumpets to maintain this height difference. An addittional bonus I've discovered recently, is that if you cut the trumpets 10mm shorter than you strictly need to, you get better air flow into the engine and noticably more power.

All of this will be less work than the mucking about with different jet sizes to get a carby running less efficiently than the efi.
Peter

Forgot to state, the big half litre filter acts as an external swirl pot as will as acting as a filter and protecting your pumps and engine.
Peter

Paul, I have put the Rover F/I in 8 M.G.B.s & it is not as hard as you think! I have a hot cam in my 4.2 & with a 112 center line on the cam the stock ecu is happy. I can take a new tank to a welder & for $50 he welds in a swirl pod (3 inch. exhaust pipe) that sets off the bottom of the tank 1/8 inch. & puts in a 1/2 inch pick up tube that goes to the fule filter & thin the bendex fule pump, that I put close to were the chrome bumper fule pump sat OR on a R/B car were the no. 2 batt. use to be right behind the driver seat (U.S. car) 150.K on my F/I set up & no problem with the fule pump! I do 5 mpg BETTER with the F/I over the carb. The O2 senser will help with the fule mileage!!!! I make up a set of motor mts. that lower the motor! I back the motor up on my cars 1 1/4 inch for A/C & lower the motor .400 tho. & I leave in the chrome bumper crossmember & with this the oip pump base that we use is close to the stering rack (.300 tho.) Your 10-1 comp. ratio is NO problem for the ecu, I was running 12-1! with rover P76 rods (6.25 inch long) with a 1.1 comp. height piston, REAL HOT cam, buick 300 PORTED HEADS, R headers, alu flywheel & with the stock ecu it would do a TRUE 25 mpg at 65-90 mph. ALL THE TIME & with the long rods you change the timming of the motor (how fast the piston goes up & down) & it ran on 87 oct., junk gas! & no knock! I LOVE the F/I so much I will NOT do a carb! I would look at getting a cam that will work with the F/I, if your will not. My 4.2 with a 3.0 rear will do a 13.6 1/4 mile. With a alu. hood I took .850 off the bottom of a 4.0 trumpet stack (4.0 stack has fewer big holes in it that were vac. for power brake hose) &you will have to grind some alu. off the bottom of the trumpet stack & the top of fule rail, were the 4 feet that hold it to the intake, were everything will mate. I took .250 tho. off the top of the stack were the plm. mates & up to the bolt that holds the ft. cover on, on the plm. Lots of luck! It might cost you some more time BUT it is well WORTH it, to do the F/I! The best I EVER did with a 4.2 carb motor was 21 mpg. once.
Glenn Towery

Glenn certainly knows his stuff, been making a living at this for years.When I do another MG I'll certainly get a set of his mounts.
I've just thought that the gear box wire would make a very nice antitheft device. Totaly disables the car!
Peter

Old age is creeping up on me. The reason why I logged back in (then forgot why!)was to say;
In order to get the trumpets out of the tray, put the tray into your kitchen oven and heat it up a bit. They pull out easily 'cause of the different coefficients of heat expansion. Once you've cut them then put them back in later with silicon. I used "ultragrey" on my engine. Heat and sensor resistant etc.. but more importantly is the same grey colour as the aluminium, so looks tidy.
The oven thing gets a bit smokey though so it is not a bad idea doing this when you're "home alone". Ignorence is bliss.
Peter

Thank you very much for your input!

After giving it some more thought I've now decided to keep the EFi - you've twisted my arm!

Definitely the way to go - especially considering the increasingly soaring fuel prices! Didn't realise the EFi was that much more efficient.

Looks like I was given some false info about the ECU. I was led to believe I would need a tuning chip or a programmable ECU to run the engine with anything other than completely standard spec. As you say, it's not much different than stock.

I already have the later sender unit for the fuel return to my tank. Plus last night I managed to get a very nice aluminium swirl pot on ebay for a good price! I can use my facet pump to feed the swirl pot, so just need an injector pump now. I plan to house the swirlpot / pumps in my spare battery well.

The wiring sounds pretty simple too, didn't realise it was that straight forward.

Once the engine is back in I'll have look at bonnet clearance.

Thanks again for your time and advice. No doubt I'll need to pick your brains again when it comes to wiring it all up!

Paul
Paul Grundy

Paul
Take care to include a vapor line back to the main tank. The vapour pressure of petrol @ 37.8 degrees C locally is around 90KPa so vapor bubbles form in the petrol very easily.
When I first started messing around with fuel delivery I thought I could simply put the pump up near the engine rail in a loop, feeding back into itself , and supply, top up, that loop via the origional pump. I assumed that any light ends that came out of solution (butane etc) would simply be burned/injected into the motor. Not so. I didn't take vapour pressure into account. A vapour lock will form and stop the primary low pressure pump operating. With a filter in the loop, it runs for about 10 minutes. Just long enough to lure you into a test drive!
Then you've got to wait for everything to cool down (including the driver!)
I then tried using a second T piece to bleed pressure away, which worked but the main pump would then cavitate noisily because small bubbles would form in the warm petrol and get pulled past the T.
You need to oviod any sort of closed loop in the system. In other words, you need to inclued the petrol tank. Obviously the main petrol tank has pressure release capacity. Mine uses a charcol canister set up, earlier cars had a vented cap.
Peter

To whom it may concern
Our company joula sanaat is one of the large company in the iran in the field of manufacturing of automobile engine parts.
We are looking for a production line for manufacturing of injector nozzle for spark ingintions engines.
If you are supplier of such production lines please contact Mr. reza manouchehri via ore contact information .
Please don,t hesitate and ask me if there is any question .

Best regared
R.Manouchehri
Joula sanaat

Emile :joulasanaat@sme.ir or joulasanaat1376@yahoo.com

Web sait: joulasanaat.sme.ir
TEL:00987124452140
FAX:00987124452139
R.manouchehri

To whom it may concern
Our company joula sanaat is one of the large company in the iran in the field of manufacturing of automobile engine parts.
We are looking for a production line for manufacturing of injector nozzle for spark ingintions engines.
If you are supplier of such production lines please contact Mr. reza manouchehri via ore contact information .
Please don,t hesitate and ask me if there is any question .

Best regared
R.Manouchehri
Joula sanaat

Emile :joulasanaat@sme.ir or joulasanaat1376@yahoo.com

Web sait: joulasanaat.sme.ir
TEL:00987124452140
FAX:00987124452139
R.manouchehri

Glenn- Nosey me, what is your best 0-60 time if you have it please? Vic
vem myers

This thread was discussed between 10/10/2005 and 30/10/2005

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