11 replies to this topic

[CooperTrooper]

Hi, im in the process of saving for this mod and was wondering if any of you guys had this engine mod already??
Please reply and let me know how you rate the performance after the mod. Cheers guys!

[fikus01]

when it first came out my friend did it, it was ok but with the same spec a carb'd engine would have made more on the rollers, fuelling the a-series becoms difficult with twin point over a certain point, thats why JCG didnt try for 100bhp, they stopped at 90 and thats only crank bhp, not wheels! sure it can be done but its a case of changing ecu's and moving injectors to get it to work as well as a carb (i think it can be done with up-sizing injectors tho dont quote me). aparantly the guy at emerald ecu's injected an a-series just single point throttle injection and betterd the factory outputs! then after all that u need to consider emmissions and legality!!

reading this gave me an insite to the complications of injecting the a-series!

emeralds a-series injection project

[Dev]

I've got stage 4 head but the rest of the kit.

yes it is worth doing, but i would consider changing the diff to a 3.44 as well.

Its not quite as fikus put it but not far off, the problem is the head and that all 5 ports suffer from charge robbing of some sort. the MPI more than others.

If you want to talk about it you can pm me and i'll let you know what to do.

Also remember that most mpi's only make 88 bhp with this conversion.

Dev

[fikus01]

actually having read that back i was a little hard on the old mpi injection system, but it was late when i wrote it so apologies, but stil port robbing is the problem.

[Dev]

I wasn't critising you fikus because what you said is pretty much spot on, it just can be a little frustrating with some people who think they know more than they do IYKWIM?

At least you bothered to put a constructive reply which is better than just "bin it and put a carb motor in"

Cheers

[CooperTrooper]

is there anyway to stop the port robbing or is that impossible?

[Dev]

i have some theories on how to do it but have yet to put it in to practice.

all i will say is its expensive and i am struggling to build the required bits

[useless]

Hi,

just out of intrest are the bhp figures you said about at the flywheel?

[Dev]

Hi,

just out of intrest are the bhp figures you said about at the flywheel?

Yes the 90 bhp kits rarely make 90 bhp normally 88 at the fly.

[Sprocket]

is there anyway to stop the port robbing or is that impossible?

Yes

Use seven or eight ports

[fikus01]

you could get a spacial crank made that has the pots 1 up, 1 down, 1 up 1 down, rather than the outer 2 up and inner 2 down. but then if it was that simple i think rover would have done that instead! failing that the 7 or 8 port head is the only other way, dont dismiss the 7 port tho just because the exhasut port it shared, this doesnt hurt bhp!

only other thing i saw, right about the time twin point came out, someone was using 4 injectors, 1 pointing at each port!! i dont know how succesfull this was!

[Sprocket]

Port robbing exists no matter how many injectors you fit or how big they are.

Easiest fix is to run a wet manifold instead of port injection, that way the fuel/ air mix is all the same at the port and each cylinder draws in the same ratio mix.

Again there is a big myth that the MPi will give more power. It doesnt. What it does do is improve emissions.

Its the engine that produces power. The fueling, if inadequate is what restricts the engine producing power.

The MPi suffers on port injection because at higher RPM, there is such a tiny injection period, any 'powerfull' engine needs lots of fuel. Thats the difficult bit. Port robbing reduces the period to inject all the fuel for that cylinder cycle, even further. There just isnt an injector thats fast enough that can sqirt the right amount of fuel. The point of the injection is what is being looked at and to date, the MPi ECU is the only one that achieves it. Real pitty that its locked code.

As for the 7 port head, yes it does get rid of the port robbing but it is far from perfect. The shape of the inlet ports on the outer cylinders is pants. The 8 port is a better port design. There is no substitute for the real thing. However forgetting the inadequacies, the 7 port is deffo a 'budget' option. Stick a turbo on it and these inadequacies almost disapear.