13 replies to this topic

[colinu]

Folks,

I've almost convinced myself that I want to convert my MPi engine to run on carbs. Yes I've searched TMF, found several threads - answers vary from not possible to possible but a pain... but none I've found offer anything approaching step-by-step guidance. Before I go any further:

• I'm talking about retaining my MPi lump/head/etc removing the ECU and fitting an HIF44 (i.e. not an engine swap to a older 1275cc carb model)
• I'm not worried about MOT emissions as this will not be for UK road use

So, I'm thinking (naively?) that this is probably what the MPi to carb conversion would involve:

• Remove the ECU
• Remove all the air/fuel inlet parts (manifold, injectors, throttle body, air filter, etc)
• Replace that with an HIF44 (suitably needled) + inlet manifold
• Tie any "unwanted" MPi sensor cables out of the way
• Probably need to re-patch or bypass some of the MPi harness (e.g. ignition to starter)
• Fit MegaJolt (plus EIDS, trigger wheel and VR sensor)
• Get a good MegaJolt base map... get her running, then start tinkering with maps and needle

I'd probably also remove the brake servo as I've never rated them that much.

Am I on the right lines, or am I overlooking anything? e.g. would I need to remove any of the MPi sensors, or can I leave them in place but disconnected from the harness? Is the list of parts replacement as simple/complete as I've stated? Is the process of removing/fitting parts as straight forward as I think it should be (I have experience of complete engine/block/head strip down and rebuild so I'm not afraid of this task). How about actually getting it to work/run... no worse than any other MegaJolt system, or is it a time consuming pig to get right?

Also... airbag and seatbelt pre-tensioners... I guess that's tied into the ECU somehow - yes? Would it be advisable to remove the airbag and pre-tensioners too?

If anyone has done this conversion I'd appreciate their advise... even if it ends up being "steer well clear of it"... I'd rather be put off now than be a week into the conversion with a load of MPi bits on the garage floor thinking what the hell have I got myself into


Cheers,
Colin.

Edited by colinu, 16 May 2012 - 05:53 AM.

[DeadBert]

I know it in no way answers your question but why go to carbs and not go for a modified injection and custom ECU setup?

Chris

[yeti21586]

You will need to run mega jolt I'd your going to attempt to do that conversion, as an mpi lump doesn't have the hole in the block for the dizzy, so the spark will have to come from the mega jolt

Edit.

Doh!!!! Maybe I should read the whole of people's posts before replying, ignore me lol

Edited by yeti21586, 16 May 2012 - 06:18 AM.

[Bungle]

the lack of dizzy will mean you will have to get your sparks from somewhere else

Edited by Bungle, 16 May 2012 - 07:11 AM.

[charie t]

Good job you read it bungle

• I'm not worried about MOT emissions as this will not be for UK road use

You need to run it with something like megajolt, i've just done it to a mini. The standard loom from an older mini can be used, and bin the mpi loom complete
The temp gauge wire if you use it, needs something thinking of, as does the cooling system piping. Its easy to do though

Edited by charie t, 16 May 2012 - 06:39 AM.

[colinu]

Deadbert - I have my reasons for wanting a carb conversion (plus I have most of the parts lying around)

Charlie t - approx how long do you think this conversion could take? Assume I'm competent, had most parts to hand, and had no distractions?

[Dan]

It shouldn't take long to do this at all. It's only like the final stage of building an engine and fitting the ancilliaries assuming you keep the MPi cam. If you get the right trigger wheel and sensor that fits easily then the only fiddly bit will be setting up the megajolt. I would assume the bulk of the physical conversion could be handled in a weekend easily, leaving just the setting up and tuning to work on. The temperature gauge is different in the MPi so you need to use the MPi sender for it I believe if you stick with the OE gauge. It might be the easiest thing to do about the tank is fit a good used late carb one. While I know you have said the MOT isn't a problem wherever you are going to use it if there are any regulations there you should check up on filler neck sizes because only the MPi tanks are restricted to unleaded. Personally I would trim the MPi parts out of the loom and keep the rest as the MPi harness is much better designed and built than the earlier ones. The SRS ECU is completely independant of the engine ECU so the airbag is not involved (although may as well be removed unless it's been replaced, they have a shelf life of ten years). The alarm/immobiliser ECU is closely integrated into the engine ECU and they are coded to each other and must work as a pair so you might need to chop the alarm out too if keeping the rest of the loom. Although specialists do have the ability to recode their programming.

[Ethel]

Just in case it's not clear, it'd be very hard to get a carb'd engine through injection MoT emissions tests.

There are alternatives to MJ that would work with the existing crank sensor Emerald, Omex... or you might manage to modify the Rover trigger wheel. You'd also have to sort the fuelling with a low pressure pump or regulator.

[AzMaN]

Just in case it's not clear, it'd be very hard to get a carb'd engine through injection MoT emissions tests.

not true, i had a 1275 spi converted to a 1380 carb, flew threw 2 mot's quite happily on the emmisions.

[Ethel]

MPI standards are higher, 0.5 carbon monoxide against 0.75

[colinu]

Fueling... I read a thread a while back where someone suggested removinging the in-tank pump and fitting a blanking plate, and/or fittiing a fuel pressure reducer. Is that practical/possible with an MPi tank? Also what should the fuel pressure be reduced down to (this engine is actually a John Cooper 96bhp Works conversion... yeah I don't believe those figures either ).

Airbags... I never realized they had such a relatively short shelf life. Most will have "expired" by now... wonder if anyone has ever bothered replacing theirs!

[tmsmini]

Colin:
I have a similar project and I am about 90 minutes away from you. I am also on the MOASF forum.
My purpose is different as I eventually plan to go FI, but only after sorting the carb/MPi block issues.
Glad to share what I know or have found out.





Terry

[colinu]

Terry - tmsmith on MOASF by any chance? I'll PM you on that forum later today.
I had a search on MOASF this morning and seems like you and StarLord have some experience if this conversion.

[tmsmini]

Starlord(Chris) may have done something with an SPi.
Mine is a work in progress. I will eventually be using megasquirt to control the Rover system, but first I will do an ignition only setup with a carb or two.
Like I said mine is a work in progress, but I need to make more progress as the shell is out for paint.
terry AKA tmsmith