1275 turbo with small bore head
Turbo Mini Forums

Well I've turbo'd my built up 1275 5 speed 68 midget. Great performance but milege sucks.

For my 59 bugeye I'm looking to go a differant direction.
1275 block, high compression with mild cam, small bore head, but with the Metro Turbo carb and turbo.

My hope is the better mileage of a 948 when cruising - but with some thrust when the boost comes on. Slide in the 5 speed and a have a nice economical cruiser, that will still "come alive" when needed.

Anybody ever try this? Any advice ?

IMO a high(ish) compression 1275 with low boost and a 5 speed trans, coupled with a 3.9 or 3.7 axle will give 40mpg easily when driven with reasonable restraint.I cant see any advantage in using a small bore head on a 1275.

My own car, with an inline engine like yours, runs 10/12 psi boost and can go down to 25mpg, but I get close to 40mpg on a longer journey.

you cant put a small bore head on a large bore iirc?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Nope you can't put a small bore head on a large bore block. Thinking about it you probably could if you blocked up lots of water ways, but there is no point.

MPG is got by having an efficient engine not a restricted engine. I would suggest you buy a decent wide band lambda sensor and tune it properly or get it on the rollers. Obviously without knowing your exact spec, head, cam, boost, etc, then it is difficult to know why you are getting bum MPG. Also what is bum mpg?

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Thanks - I do have a bit more aggressive cam, but I should probably get it on the rollers, play with the needles and dial it in. What needle and spring do you use ? and did you recurve the advance on the Dizzzy. I don't have boost retard on the timing.

Ever do anything with a detonation sensor? I just installed a wide band mixture guage and but haven't done much with it yet.

Thanks for the replay

These days I just assume everybody has mapped ignition. The best, and I mean the best, thing you can do to improve you engines MPG is fit mapped ignition and then you can advance it massively on cruise and save a fortune. A megajolt will pay for its self in fuel in no time.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Hello and Welcome

What do you class as high compression ratio? More than 9.4 with a metro turbo setup and chance are you'll be needing new pistons pretty soon

If I were to build a high MPG motor I would go for a turboed SBU.

They can match standart metro turbo powerwise and dedicated driving must be more rewarding on an economical point of view ?!

Rusty by nature

to add to the above,

my 1380 7 port injected turbo (8.5:1 CR) has returned 40+mpg on a run, and there was still room for leaning the mixture out.

I would say a 5 port head would be better due to not having massive ports,

keep the compretion ratio up to 9 or a little above, and use a mildly ported head and you should see good mileage,

also somthing like an MPI cam or kent 274 should be good

MPI cam is a wilder cam than standart ?

Rusty by nature

a little bit, but not over the top,

similar to an MG metro cam I think but with a wider LCA,

I have one to measure but haven't got around to it yet

Joe, this might save you from having to measure

http://www.mlmotorsport.com/forum/index.php/topic,11.0.html

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

Cheers Gary.

Since I have a 256 on the shelf it's not worth finding an MPi then

Rusty by nature

I have an mpi cam going spare