MGB conversion

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SouthCoastGT
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MGB conversion

Post by SouthCoastGT »

Hello, I'd like to convert my GT to fuel injection, primarily for reliability and economy, but the occasional bit of sport would be nice.

Currently I have twin SUs, but I can get hold of an Extrudabody bolt on kit, including throttle bodies, fuel rail and injectors, which use the existing manifold on the 5 port head.

I have three questions: would this kit be worth getting, and where can I go to get the rest of the fuel supply kit and sensors? Finally, who can fit it? I have no workshop facilities at all, not even a driveway.

Thanks
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Re: MGB conversion

Post by Matt Cramer »

On 5 port heads, you'll either want to have the injectors at least 6" from the port split, or use the semi-sequential Siamese injection mode.

Where are you located? That will help for recommendations for an installer.
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racingmini_mtl
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Re: MGB conversion

Post by racingmini_mtl »

Actually, on a 5-port head, the best options are either a single point injection (with one or 2 injectors) for a wet manifold setup or a fully sequential port injection with the injectors close to the head. A semi-sequential still leaves an AFR imbalance that you can't correct and a dual wet port setup gives you even less control on AFR distribution.

You may want to read this article about the early work on the siamese injection mode and some of the issues with the siamese port setup. Please note that some of the information in there refers to older firmware and is no longer accurate. It also talks about a turbo setup which does add a few complexities.

Jean
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SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

Thanks both, I'm located on the south coast of the UK, near Brighton. As I don't have any sort of workshop facilities I'm looking for someone to do this for me, but I don't mind helping out at all.

My most immediate question is would the hardware described in my first post be worthwhile purchasing? Alternatively would anyone have any cost effective solutions to relatively simple conversions?
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Re: MGB conversion

Post by billr »

Do you have a link to info on that "Extrudabody" system?
SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

Have a look on this page, this all I know
http://www.mginfo.co.uk/upgrades4mgs/En ... tions.html
DaveEFI
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Re: MGB conversion

Post by DaveEFI »

Have you asked on an MG forum? You might get a wider audience there. I've not seen a B with MS, but there are plenty A series engined cars with it - and the principles will be the same, if not the hardware.
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billr
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Re: MGB conversion

Post by billr »

I should "bow out", since I know little about that car, but I am curious:

Is yours an I-4 or I-6? When I heard "5-port" I was thinking I-6, but the linked-to site shows I-4s with "2 ports". What are you working with here?
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Re: MGB conversion

Post by 2cvJasu »

billr wrote:I should "bow out", since I know little about that car, but I am curious:

Is yours an I-4 or I-6? When I heard "5-port" I was thinking I-6, but the linked-to site shows I-4s with "2 ports". What are you working with here?
I-4. Two intake ports and three exhaust ports, total 5-ports...
SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

I've tried a couple MG forums, but I'm afraid the majority of users believe these cars were created perfectly and any change is sacrilege. I've lost count of the "why do you want to do that?" responses...

Bill, I'm sorry but I don't understand what you're asking. The head is similar to an A-series, but bigger.
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Re: MGB conversion

Post by racingmini_mtl »

billr wrote:I should "bow out", since I know little about that car, but I am curious:

Is yours an I-4 or I-6? When I heard "5-port" I was thinking I-6, but the linked-to site shows I-4s with "2 ports". What are you working with here?
The B-series engine in the MGB and the A-series engine in the Mini (the real original one no the BMW one) are 4-cylinder engines with a 5-port head: 2 intake ports and 3 exhaust ports on the same side of the head. So you have intake ports that are shared by cylinders that are 180 and 540 degrees apart.

That's not much of a problem when you use a carburetor but with discrete injection pulses you need to be careful how the intake setup is designed and what injection strategy you can used with a specific design. And when you add wall wetting contribution which is intrinsically not symmetrical in dual point setups due to the siamese ports, you add more variables that need to be compensated for.

It is complicated but it's far from being an impossible task. The problem is that few people take the time and effort to understand the entire scope of the different constraints and many just reuse intake parts designed for carbs and skimp on the needed instruments. If you want to do that, use a single point injection and a single WBO2 sensor: you'll basically end up with an electronic carb setup which is fine. If you want a dual injection setup, you'll need a setup that allows you to do fully sequential injection and you need dual (or triple) WBO2 sensors to monitor the inner and outer cylinders and make sure your injection timing is correct. Depending on your injection strategy, you may also need to trim the inner and outer cylinders differently to take into account the different wall wetting contribution.

I should add that in a dual point setup, ideally you would want to inject as close to the head as possible. Injecting further away will increase wall wetting contribution which might increase the difficulty in tuning fast transients. And adding a balance tube (like in the standard twin SU manifold) will also add unwanted fueling variability.

Port injection has been successfully done using the MS2/Extra siamese injection mode and also with the MS3 using standard sequential injection (but in a non-standard way). The advantage for the MS2 is that it has a dedicated set of parameters that cater to all the peculiarities of the siamese-port head with a lot of flexibility in choosing an injection strategy. With the MS3, you have to repurpose the standard sequential injection strategy so you only have a single mode but that can arguably make things simpler and you do have a more powerful ECU with more options.

There's a lot more to say on the subject and more can be found on this forum, on the TurboMinis forum, at the link I gave above and other places. And there are others here and elsewhere who are better equipped than I am to elaborate on the challenges and solutions of such a project.

Jean
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SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

Thanks for the info. Interesting reading. Lots of projects I've read are unfinished so any conclusions aren't there to follow up on.

If the Extrudabody system is worth getting I'll need someone to spec all the other parts along with the ecu, fit and tune it. Any tips on any of those?
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Re: MGB conversion

Post by dontz125 »

racingmini_mtl wrote:That's not much of a problem when you use a carburetor but with discrete injection pulses you need to be careful
Ok, here's my stupid idea of the day - is it possible to PWM a fuel injector such that it flows a continuous-but-varying fuel flow, much like a carb jet? I realise the injectors aren't designed for it and probably wouldn't like it, so - what about some other kind of solenoid valve? dP across the orifice will remain the same assuming a referenced regulator, so atomisation shouldn't be an issue.

It's been too long since I've looked at orifice-flow calcs, but I recall they were distinctly non-linear vs orifice size, so range / turn-down / granularity could get interesting.
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billr
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Re: MGB conversion

Post by billr »

I'm thinking a stepper would be more definable/predictable, but wouldn't a TBI and "wet" manifold accomplish the same thing with existing MS capabilities?
racingmini_mtl
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Re: MGB conversion

Post by racingmini_mtl »

Yeah, if you want to have an electronic carb, use the single injection point (TBI) wet manifold setup; this will work with discrete pulses because all the cylinders "see" the same injector(s) in a relatively symmetrical way regardless of pulse timing as long as you use 4 pulses per cycle.

Otherwise, use the sequential dual injection point setup where you can deal with the discrete pulses by correctly timing the injection and monitoring the AFRs; there is no need to invent a new way of injecting fuel to mimic carbs. If you want to do the latter, use mechanical injection.

And the Extrudabody setup seems to use the standard SU manifold which means you get the balancing tube and it also seems to have injectors that are relatively far from the head. Both of these have the potential of creating issues with AFR distribution that you won't be able to control. I would look at something different that addresses those 2 issues.

Jean
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SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

Thanks chaps, that's pretty much made up my mind. I'll pass on the system that's been offered and look for something more akin to what racingmini describes.
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Re: MGB conversion

Post by dontz125 »

... and another dippy idea from the House of Madness gets shot down, but the customer goes away happy anyway - my work here is done! :lol:
billr wrote:I'm thinking a stepper would be more definable/predictable
A PWM solenoid has to be very predictable / repeatable, otherwise open-loop idle & boost control wouldn't work. Which method would have better control especially at turn-down could be an interesting experiment, but one that the need for which you and Jean have just obviated.
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Re: MGB conversion

Post by stevemgbgt »

I have an Ms1 on my MGB for seven years or so running four injectors close to the port in a modder inlet manifold.I run a wideband in the centre exhaust only and as such I cannot recommend it as I could be causing untold damage and am certainly losing out on performance/ economy.It seemed a good idea at the time.I considered upgrading to Ms2/3 and going sequential but I am not sure I could work out the injector sizes and timings,and the cash required is presently unavailable.I bodger the system together myself and it cost me approx £1000 GBP so I imagine it would be expensive to have it done.I believe there is a ready-made kit involving a 7/8 port head.Have fun,Steve.
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Re: MGB conversion

Post by DaveEFI »

SouthCoastGT wrote:I've tried a couple MG forums, but I'm afraid the majority of users believe these cars were created perfectly and any change is sacrilege. I've lost count of the "why do you want to do that?" responses...
Of course you'll get that. All classic car forums have them. But you should also hear from those who have done this.
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SouthCoastGT
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Re: MGB conversion

Post by SouthCoastGT »

I've asked Jenvey to take a look at the problem for me. As long as I can get a compatible DCOE40 manifold they should be able to sort all the hardware. I'll just need to find a local MS expert to fit and calibrate it.
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