Is it possible to..........

[JollyMG(1)]

Turbo the Efi? as opposed to dumping the Efi for the original carb setup as on the original MG Turbo's?

And if so what's involved? or would it be easier just to convert to carb?

;)

[Mat_C]

Moto-build have done it. Its difficult to do as the the fuel injection system obviously isn't boost sensitive. You also have to run less boost as due to the higher CR.

Be an excellent drive though - if only the carbed turbo had the (off-boost) throttle response of the efi.

[JollyMG(1)]

Cheers Mat, yeah theres lots of things to think about like fuelling as it would run too lean when boost kicked in and would need a device to change the fuelling rate at a certain rpm, I would almost certainly have to have the Turbo bottom end for strength as surely there must be differences in the Efi and Turbo O series lumps.

Yes is would be good if the Turbo's had the off boost acceleration, but I suppose that's down to the LC they need.

[Mat_C]

AFAIK the only *major* internal differences between turbo/efi are the fully-floating small ends with oil thrower and sodium filled valves.

[GK AutoWorks]

Fitting a Turbo to the EFi has its limitations.

1. You can only run low-boost pressure. The air flow mass meter system on the EFi wasnt designed to see boost and cannot meet the demands needed under load/high boost.

2. The compression ratio isnt a problem (Efi 9-1, Turbo 8.5-1) but the pistons are, they are not strong enough for the job. The Turbo engine also has two extra studs to support the manifolds on the head, and the exhaust valves are sodium cooled.

3. An oil feed for the Turbo has to be fitted, as well as a drain. The best and only long term solution is the fitting of a Turbo pump. The oil drain on the Turbo engine goes into the back of the block, the pre-1989 O series doesnt have this but those after DO.

4. You'll need to modify the EFi inlet manifold. This will be very VERY fiddly and is easier if the engine is out, as to fit the inlet manifold on with the turbo/exhaust manifold in place will be nigh on impossible. There will be heat soak issues as well caused by the long inlet tracts on the inlet plenum running directly above the turbo.


To fit a carb/turbo system to an Efi engine is still not the ideal solution. The fuelling will be ok, as will the ignition, as in both, a Turbo ECU will be used. The boost will still have to be kept low. Don't forget that both ways would need a change of exhaust system and minor wiring changes.

To do either would require alot of time and effort. It's not true that the Turbo is poor low-down compared to the Efi. Throttle response is marginally sharper in the EFI but the torque does not compare to the Turbo by the time everything starts to happen at around 2000rpm. Getting back into an EFI feels like someone's taken 2 cylinders away, they really cannot compete.

Your options for extra performance are = Fit a complete Turbo engine with the carb system IF you can find one. Not going to be very cheap.

Tune the existing engine to improve top-end performance. Some good gains can eb made by fitting 2 inch exhaust system with downpipe's, an FSE power boost valve and different air filter element with more effective cold air feeds. Bosch injector's can also be fitted which have a better spray pattern. With this lot you can see 130bhp on a healthy engine and retain all the virtues of the EFI which it's famed for.

OR, fit a T series NASP or go the whole hog and source the turbo version. Although more modern, neither option will be more economical than a well looked after and tuned O series/Turbo lump, and although the T series Turbo in standard form is 200PS, isn't faster than a O series Turbo tuned to the same power level.

[Mat_C]

Originally posted by GK AutoWorks

Throttle response is marginally sharper in the EFI but the torque does not compare to the Turbo by the time everything starts to happen at around 2000rpm. Getting back into an EFI feels like someone's taken 2 cylinders away, they really cannot compete.

[/B]

I want my turbo to be like that - it only gets going at 3500rpm and pulls off like a milk float off boost.

Need to sort my bloody exhaust valves out!

[GK AutoWorks]

It's all to do with low end fuelling, the Efi has the advantage here because it has a basic map, the Turbo tends to run quite lean on part-throttle (limitations of the carb system means fuelling isn't quite right everywhere, and they have a weakening device to improve economy and emissions)

However, increasing the fuelling using a air-bleed device see's quite stark differences in low down performance, with virtually no changes in overall fuel economy if driven gently, i've obtained 35mpg on a run which is not far off what an Efi can do!

[Mike Brock]

Boost activated fuel delivery is the answer. MF2 5th injector etc. You'll need the Maestro/Monty Turbo ECU. MF2 wires into MAP sensor (3D mapping). Turbo block with lower C/R is a must. It can be done.

Mike Brock...