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MG MGB GT V8 Factory Originals Technical - Fuel Injection 'upgrade' from SU Carbs?
|Not sure if this is an upgrade or not but how easy is it? I currently have a 3.5 V8 in my Roadster with a custom manifold & SU carb adapter (similar to Factory GT V8 with carbs at the back of the engine). What is needed to convert this to Fuel Injection and is it likely I will need to modify (or replace) the bonnet? |
|You will need:|
Throttle bodies ( I have seen SUs modified, i.e. stripping out all the fuel metering equipment from the carb,) there are also SU throttle bodies available, although these are expensive, and yo ucan always hunt the scrap yards for something that will fit.
Injectors. These will either mount into the throttle body, into the manifold behind the throttle body, or in front of the throttle boides in a mixing chamber called a plenum. These are usually best bought new.
Injector rail. This is to ge the fuel along to each injector at full pressure.
Swirl pot. This is to ensure the engine is correctly fuelled in hard manouvering
fuel pump needs to be uprated due to the high pressure needed for injection.
You will need a return line back to the fuel tank for excess petrol as well.
You will also need a throttle position sensor, and an injection computer to tie it all together. I'd reccomend Megsaquirt (www.megsaquirt.info) as it is free.
I'd also go for a lambda sensor in the exhaust to make sure that the car is fuelled correctly.
|I hesitated between Holley and fuel injection. I have selected Holley. I am happy.|
You need to make small cutouts in the intake port in order to clear the injectors. That is if you have a pre SD1 engine and plan to use OE Rover injection.
You're welcome to inspect my Efi setup and have a test drive (I guess you are local.)
Are you contemplating flap-valve or hotwire system ?
The 'easy' route is to use an RV8 bonnet for clearance, otherwise there is a lot of machining to do on inlet manifold,plenum base, trumpets and plenum top
You will get a big improvement in performance and fuel economy.
Terry Brown at Freckleton will probaly have an Efi inlet amnifold, but you would be better off buying a full Efi system off E bay (preferably off a Range Rover which is a runner)
Thanks for the offer. With regards to the type of EFI - I haven't really thought about it, it is really just an idea at the moment.
It is eBay that got me thinking about this as I have seen a few 'complete' systems on there recently. I am a little unsure about what I need. The other option is Weber/Edelbrock 4-barrel carbs but this seems more expensive?
|Best way to to buy (secondhand) the fuel injection set up from a ranger rover (or rover). Hot wire is heaps better than the earlier flapper set up which had problems. How to you tell the difference? The flapper style mannilfold had a flat top with six central bolts and the hot wire mannifold is taller with a striped pattern on the top. by the way Rangerovers had the "hot wire " type manifold from '86 onward even though they ran "Flapper style" electronics for another three years. You might be able to save money by getting the latter style manifold off a '86-89 and fitting it with hot wire sensors. The true hot wire set ups have a large "3.9" inbossed in to top/front.|
Get an intake manifold, trumpet tray (with trumpets) and top cover/throttle body. Basicaly everything in the valley of the "V" is the fuel injection and unbolts up/down as a unit.
On the manifold you need the fuel rail with its regulator. Temperature sensors for each of the fuel rail and the water in the manifold and a throttle position sensor.
You also need an air flow sensor and the computer and its loom. You will need to wire into your car a fuse off the ignition, a fuse to power the computer and a fuse for the fuel pump. ie buy a second MG fuse box.
You must measure how much bonnet clearance you have above the manifold (without the trumpet tray/cover, suggest you stack up wood or cardboard until you can't close the bonnet) and then take the trumpet tray to a machine shop.
Have them weld up the 3 vacuum take offs then machine up to 16mm off the bottom of the tray and up to 12mm off the top. if thats not enough then have them machine 5 (or even 7) mm off the top cover, but it's unlikely that you'll need that much clearance. Some people even replace the front "corner bolts" with phillips heads to get couple of mm. They should charge less than $150 to do this.
You can take off 33-34mm toltal before running into clearance problems with the throttle body/rocker cover.
I took off 16mm plus 12mm off the tray and 5mm off the cover then found I had taken 12mm more than I needed (Doh!)At some stage Iwill get my spare trumpet tray machined and will take 15 off the bottom and obviously less off the top.
You also need to cut down the trumpets. I did this myself because it wasn't hard and to save money.
There is a slight complication here in that the trumpets are all the same length and sit on different hight sholders machined into the trumpet tray. The four center trumpets sit higher than the two pairs at the front and back. The idea of the different height trumpets is to even out the lenght of the air channel through the intake mannifold so that you get the same "air ram" in each cylinder. MEASURE THE DIFFERENCE IN HEIGHT BETWEEN THE MIDDLE TRUMPETS AND THE END BEFORE YOU GET THE TRAY MACHINED.
For example if you machine 10mm off the top of the tray and 5mm off the top cover you must shorten the four middle trumpets 15mm.
It is important to ratain the height difference between the middle and front/back trumpets.
|Accidently sent that too soon.|
When you have the bottom of the tray machined you will remove the shoulders for the front and rear trumpets. This means you need to shorten them more than the middle trumpets. Put the middle trumpets back in and them measure how much you need to shorten the end ones to reessablish the height difference you measred earlier.
This all sounds much more comlicated than it is.
For the fuel supply you don't actually need a swirl pot at all or infact do anything to the tank. You do need a return line from the engine compartment which is not hard to do.
Buy a bosh high pressure pump ($150), a roller vane high volume "feeder pump" ($95) that Peirburge make, a large half liter metal filter ($20)
and a very late model MGB fuel level sender ($60).
This late sender actually has a fuel pick up incorporated into it which will give you a fuel pick up and you can use the old pick up as a return line.
You set up so that the feeder pump draws through the big filter from the late model pick up. The feeder pumps feeds the high pressure pump, which feeds through to the fuel rail on the engine, which inturn feeds back to the old "pick up" back at the tank. The filter protects your pumps and injectors AND acts as an external antisurge tank. You can set htis up in about an hour with some rubber tubing, sissors and a few clamps. Because you're using a feeder pump you can also put all this in the boot if you like. The feeder is supposed to be good for drawing up to one meter. The reason you need a feeder pump is that the high pressure rollervane pumps don't draw well and petrol (unlike water) does not siphon at all well. Infact the petrol has a vapour pressure of 90 plus KPa at 37.8 degrees. This is why the described set up has the Tank (wit its own pressure release system) in the system. If you have a closed loop in your fuel supply this pressure will cause your pump to either fail and/or be very noisy.
There are part numbers listed in the archives."swirl pots, who needs them" "EFI fuel supply"
I have tried just about every set up possible and this (the easiest/cheapest) has been the only sucessful (quiet reliable) to date. I have had the tank down to a few litres and never had a surge problem.
Bottom line- fuel supply allow $300 Australian.
$150 for machine shop costs. The cost of manifold trumpet tray, throttle body, computer and air flow meter will vary.
I'm not sure about the distributor, others can tell you if the one you have is OK.
|PS- you can get the trumpets out of their tray by putting it onto your oven. They pull out quite easily when hot because aluminium has a larger coefficient of expansion than steel.|
|......but don't tell the missus, evidently if you can cook the trumpet base, you can make Sunday lunch for 6 people !!!!|
Excellent resume, Peter...Except that I got away with just one Bosch pump, carefully mounted close to the tank outlet.
|Another possible route, I saw recently a 4bbl throttle body, may have been on ebay or a link to a website but it was a single cast piece about the size of the center body of a Holley, smoothly contoured with a single injector mounted for each bore two to the front and two to the rear, angled into the throat just like an injector would be mounted to an intake runner. It looked to be short in height and designed to accept a conventional round air filter. Now one of those with a MegaSquirt controller would be a very simple, easy, effective, and tunable conversion. That's the one I would recommend if you'd prefer not to do the machine work to get a late Rover EFI intake to fit, and I would still recommend the MegaSquirt controller in any case. As far as the tank, I wouldn't worry about the swirl pot. Just mount an external pump by the tank and try to stay above 1/8 tank of fuel. Going this route one should easily be able to keep costs under $1000, and maybe half that.|
|You will need a black box for the EFI, the 14cux is preferred.|
Seen the 4 barrel on the Internet ( I think )
This guy uses it to good effect on the mini
All the basic information you need to fit one of Rover's Lucas fuel injection systems is covered in Roger williams' books 'How to Give your MGB V8 Power' and 'How to Improve your MGB, MGC or MGBV8'. Both books are excellent.
|P L Hills|
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) and for the people in Melbourne can be got from Petro-ject 03 98737006.
You can always try it with out one and when you find you need it splice it in later.
The main high pressure pump is a Bosh one pt no 0580464070 and cost $140.
|Take a look at this site http://www.twminduction.com/ThrottleBody/ThrottleBody-FR.html |
SU throttle bodies!
This thread was discussed between 07/05/2005 and 16/05/2005
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.