7 replies to this topic

[banana_man16]

hiya i have a 1275 spi and im looking to change it to mpi for more power? and was wodering if its alot of hassel? could any 1 tell me if u have to change alot of things loom etc? i'v had a look around in mags ect and u can get mpi conversion kits but not sure if thats the real thing if that makes sense if not has any 1 got any suggestions bout a way round it i.e how to make it faster (up to 100bhp would b nice to beat saxo vtr's ) with differnt mods already got rid of the cat and got a k+N air filter and looking at a new manifold and throttle body! not to keen on webbers or anything.

thanks alot



liam

[mini_dave]

The standard SPi and MPi are similar in power and for the hassel you wouldnt gain much out of it, the MPi is alot different aswell, the raditor is mounted differently and i think that it doesnt have a dizzy (someone may correct me). i would think you are better getting the engine rebuilt for the money. to gain more power (100bhp ish) you would need to look into getting a new head, cams, rokers, mabey even a larger bore.

[E.L.M.O]

i never knew the diffrence between a spi and mpi and i admit, i was curious

[Bill USN-1]

MPI was developed more for emissions then for power.
While there may be a very slight increase in "potential" power due to the dry intake runner(fuel not using up space with the incoming air) if the motor is tuned and the air fuel ratio and timing are optimized, you will see very little difference.

The MPI is probably worse on the A motor due to it's siamesed port head.

An engine is an air pump.
you have to get more air in and get more air out.
and use it efficiently!!


So
bigger Throttle body
bigger intake
bigger head(ports/valves)
bigger cam to open the valves
bigger pistons
bigger exhaust
better ignition and timing control
And try to make everything as light as possible.

Then it all has to be optimized to work together as a package.(rolling road, dyno)

[AlexM]

Yes, the mpi mini and the spi both had similar power outputs. However when you say convert to mpi, you could fit an 8port cylinder head and have mpi that way.... Then you would get more power, more like 120bhp with few other mods. Although the expense would be high.

[banana_man16]

thanks guys that really helped think i'll prob end up satying wiv spi and just use other mods such as new head etc

thanks again

liam

[Sprocket]

You will not gain any more power over the SPi by changing to MPi, Fact!! The injection system is not what produces power, same way as a bigger carb wont produce any more either.

The MPi system does however improve the emissions levels and thats the only reason it exists!

As also explained above the engine is completely different, you cannot easily fit MPi on a Non MPi block, i recon it could be done, but as of yet I dont know of anyone who has.

Spend your money tuning the engine in the correct manor

[Dev]

In order to gain more power ie 100 bhp plus from and mpi you would probabley need in excess of 10k to do properly the head alone will set you back 1.4k ( bill richards 8 port) to stay injected mbe do a injector set up its brilliant but again steep at 3.4k.

as psrocket says stick with tuning your spi. it will be cheaper.