11 replies to this topic

[Matt_Brum]

Hi all,

Does anyone have any knowledge of the SPI's tolerance for aftermarket cams?

Im picking up a stage 3 1293 engine that will have a minisport CA4 cam installed in it. Will this be too much for the ECU to meter for?

I looked on the minisport site but there is no info on the cam profile apart from "Race/Rally".

Anything would be good, just deciding if i need to change the cam whilst i strip and rebuild? )

I hope I'm not covering old ground... i did search about.

Thanks,

Matt

[vasi]

According to common lore it is not advisable to change either the cam or compression ratio of the standard spi lump. Most of all other mods can be accounted for. I believe this boils down to ignition map, whereby changing such features would require different ignition timings fromm that of standard.

[Sprocket]

True Vasi.

It also has a lot to do with the overlap of the valves opening on longer duration cams. This affects the Manifold Absolute Pressure (MAP) readings for the ecu so again fueling and ignition are screwed and you'll never get it through emissions tests. The engine will run but not to the cam's potential.

Any of the cams that are designated 'injection' were designed to work with the standard ECU. I recomend the Kent MD274. They do a scatter patern of this cam also, i'm building another engine with one of these so cant comment on that yet, but the MD274 is great, pulling fron 1500 right up to 6500. It realy takes off at around 2500 with peak torque around 4500. Power and torque curves are nice, smooth and progressive.

Its not about the power numbers, its about how it drives.

Oh and my engine is a 1399cc with a Group A rally head, the fuel consumption on the other weeks Wirral Llandudno run worked out at 34mpg, so only 4mpg down on the standard 1275. Which is surprising. Got to hand it to the injection.

[vasi]

Its not about the power numbers, its about how it drives.

This is so true. 100bhp @ 6800rpm with frick all at 2000rpm is about as much fun as a chocolate kiln.

I'd take 85hp @ 6000 with driveability anyday.

[Matt_Brum]

Thanks guys!

Might be a CA2 profile CAM so might see how it runs.......

Speak nicely to the people at Aldons R.R see how the ECU is coping, be interesting to see what happens.

Can always whip her out again.

Matt

[Sprocket]

Word of advice

Do not let any one 'sell' you a piggy back ECU unless you can pick it up dirt cheap

[fikus01]

some of the factory spi's came with a kent 266 cam!! if that helps!

[powermadcoop]

there seems to be a few MD274's?! im confusd

im a bit poo poo at this to be honest. do I go for the sports injection or the sports torque one?

im gunna be putting this with the k and n air filter.

play mini 3" side exir exhaust

minisport stage 3 head

1.5 rockers

any ideas?

[powermadcoop]

is there any benefit in changing the cam and not doing the head?

[Sprocket]

Yes, but ultimately you gain better results by doing both, id say if you are building the engine, its already out of the car and cant afford the head, then fit the cam, at least once the engine is back in the car, its easy to swap the head at a later date

[powermadcoop]

ok cheers. Would you still say to use the md274 cam without head then replace head at another time...?

[Sprocket]

Only fit the cam if you are planning on taking the engine out and splitting it from the gearbox.

Otherwise, if the engine is in the car and you would have to take it out solely to fit the cam, i would buy a decent head instead, its not worth the effort and you may be disapointed with the results after pulling and refitting the engine just to fit a cam, the head will yeald better results.

Having said that, once the cam is in there, its only a matter of hours to fit a decent head at a later date.

Like I said, you will only really get the best of either with each other.