8 replies to this topic

[Petrol]

I’m building an MPI from scratch and want to get the best out of the engine. I want it to rev freely and smoothly using the stock ECU so the plan is to blueprint the engine by balancing both weight & CR. I’m also planning to port the head myself and fit bigger valve(s)
So far I have seen 2 books -

David Vizard - Tuning the A-Series Engine
Dez Hammil - The 1275cc A-series High-performance Manual

I’m looking for info on porting and cylinder head chamber shape. Which book will be my best bet?

Thanks
Pete
 

 

[cradley-heathen]

in my opinion the vizzard book.

 

im no expert as i have ever had to do much engine work on an mpi, certainly not performance stuff anyway, but i think the ecu is the limiting factor really, im not sure how much you can do to the engine before you will have trouble getting it to run right, i would think head work would cause some bother with the fueling etc.

[cian]

I tuned my mpi as far as it would go on the standard ecu and i found the more mods i added ( head etc ) the worse it ran, since then i added the sc 5 port management kit and the difference is starteling, definatly budget for the kit in your build otherwise the money you sink into heads cams etc is wasted

[Fast Ivan]

There's a fair bit of info on head mods in Vizzards, dimensions, tools and tips.
Cian, how do you get round the cold starts with no idle air control valve that the sc kit removes?

[cian]

This is one of the points i raised with sc and they said to use the throttle for a minute or so untill the engine heats up and then the idle is stable and thats what i have been doing and its perfectly fine

[Petrol]

I tuned my mpi as far as it would go on the standard ecu and i found the more mods i added ( head etc ) the worse it ran, since then i added the sc 5 port management kit and the difference is starteling, definatly budget for the kit in your build otherwise the money you sink into heads cams etc is wasted

 

OK thanks for your help guys. Maybe I need to have a rethink about the best route to take

 

Pete

[Fast Ivan]

it all depends on how far you want to go really, are you looking to squeeze as much out of it as you can or just a bit more power/acceleration?

[Petrol]

it all depends on how far you want to go really, are you looking to squeeze as much out of it as you can or just a bit more power/acceleration?

 

 

In the 80’s I used to have a Mini 1000 and the engine I built was a bit of a screamer –
12G295 big valve head
Twin 1 ¼ SU carbs
Fast road cam
Lots of lightened stuff – flywheel, thin ring gear, forged rockers etc etc
Fully balanced including CR’s

The upshot of it was, it was a great drive. The gearing was standard but with the high revs it was a car that put a smile on your face.

What I am looking for with this MPI build is to something that’s as fun to drive. I’m not particularly after more HP and I don’t really want to change the engine management system. I appreciate it limits the revs but I just want it to get there without a struggle. I am changing the 13” wheels for 10” and 165 tyres and can change the final drive if needed.

Might be worth a mention that I have never driven an MPI, nor a 1275 Mini. I appreciate it’s a longer stroke and inherently more difficult to rev but with the right engine mods / gearing combo, I’m sure it can be done.

So far I have bought a 1.5 Roller rocker assembly and a set of Kent valve springs to go with it. Probably a mistake but I can probably get a credit note if I return them.

That’s what I’m looking for. Any help would be great.

Thanks
Pete
 

Edited by Petrol, 11 February 2014 - 10:40 PM.

[Petrol]

Think I have got to the bottom of this

 

1000cc screamer is easy due to the short stroke

1275 needs a full race build to get it to rev

With an MPI it's difficult especially with the limitations of the ECU. I don't really want to go Megajolt so will work around it by gearing / balancing

 

Thanks to monster_mini AKA Nick for the advice

 

Pete