johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
Got a corsa 1.2 spi 8v. Have a few engine mods, about as much as can be done without removing the Spi and chucking in a great big carb. Anyhow, wondering if anyone knows how would a 1.2spi engine run with a kent 285 cam. Thinking of fitting mine as its a spare one lying around. Afraid of engine idle to high or possibly too low as it maybe lumpy. Anyone ever tried this.
BTW i'm not expecting any significant power gain, just seems to be a waste having this kent cam lying around un-used. Thinking at most i'll prob get 4 bhp more out of the 1.2 lol :-)
Not so hard to fit this cam as i have a rocker remover tool so its worth a try since its not alot of bother, aint gotta remove the head.
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
coudl be an interesting project to give it ago. even if it gave you 10% you'd see 5bhp, and really it would be getting it fuelling right after putting in the cam which would cause not to run right.
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
Since its an spi system, theres nothing really i could do to fuelling, there's no superchips availble, doubt the ecu can be mapped, which i would'nt bother with anyway. And i can't tinker with the spi like you can jetting a carb. I'm hoping the fueling with correct itself, if the ecu realise that the engine is getting more air from the higher lift. fingers crossed. 
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
the real bugger is that i can't adjust the idle speed if the cam is running very lumpy, so the engine would be idle at the usual 950 rpm or so but would be very lumpy since i would need to up the idle speed to idle correctly
|
Dave A
USER UNDER INVESTIGATION - DO NOT TRADE
Registered: 10th Dec 03
Location: County Durham
User status: Offline
|
it would run awful without the cam being timed in and the fuelling will be way out.
for 5 bhp (if you get that) is it worth it?
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
What do you mean by the cam being timed in? The timing on a std cam and aftermarket ones are identical, meaning both pulleys are timed as usual. The degree and duration is different on aftermarket cams but this does in no way affect timing marks e.g pulley allignment As for fueling that remains to be seen, it has been suggested before the the ECU has a good chance of adjusting the mixture, after all is that what the ecu is used for, the right mixture at the rite time. yes i think it is worth it. I can do the job in just over 30 minutes with the rocker remover tool, and can be put bck to orignal in the same time if needed, and as i said the cam is lying spare, why not put it to some use. cheers
|
Dave A
USER UNDER INVESTIGATION - DO NOT TRADE
Registered: 10th Dec 03
Location: County Durham
User status: Offline
|
what i mean by being time din is dialling in the cam. aftermarket cams will always give better results if the timing is advanced or retarded using a vernier pulley as most cams will give good gains but usually a lot higher up the rev range where it is not usable, especially on smaller 8v engines due to the low rev limits. if the cam is dialled in then changes must be made to the fuelling otherwise it wont run very well.
if you have the cam spare and want to give it a go, do it. let us know how you get on
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
would'nt go to the bother of fitting a venier pulley, as the cam is only a 285deg. It would prob be worthwhile with a 295 + cam. But yeah sure i'll give it ago at the weekend maybe, it will be intresting to see what happens, espically since everyone has different expectations of what will happen
As a side note, it will give me a better exhaust note, love the old warble puttery sound lol, cheers
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
just to let you know, i will fit the kent cam tomorrow. I will make sure to post the results of this little experiment here. But i can't be to sure of what more power i will truly have, as my centre peice exhaust is blowing out and causing loss of power. I'd say i would be very lucky to gain 5 ponies, espically since the 12NZ head is so restricted with small ports. Reckon it would be more like 3/4 bhp Altought i fitted a 295 deg cam to the older heads such as the 1300SR nova and 1200 carb nova, and it did produce pretty good results along with the other mods. I think the biggest source of all power on these little 12NZ is to dump the spi head, fit 1200 gas flowed carb head, and so you can run either a webber 32/34 twinkchoke from a 1300sr nova or slap on the big guns the webber 40s. The carb head and fuelled is the most important building block. i've had amazing results on my old nova by tuning. Engine was a C12NZ spi std, fitted the 1200 carb head which had been ported polished skimmed, fitted a set of 40s on a 1.3 nova sr T40 manifold, fitted a 295 kent cam, 4-1 manifold, striaght thru exhaust, as the engine was carb fuelled i had no need for a cat. The bhp figures jumped from about 45bhp std to nearly 88bhp. Got to say that it was amazing for a c12nz, like driving a totally different car, also changed the fd to 4.18 with 185/50/14 tyres, to be honest i was really pleased with the results, the nova could beat the corsa and nova 1.4 sri engines 8 valve MPI. If more power was wanted, the bottom end would have to be tinkered with, but it would'nt be worthwhile on a 1.2. Cya
|
Cybermonkey
Member
Registered: 22nd Sep 02
Location: Sydney, Australia
User status: Offline
|
interestng stuff
|
rallyman
Member
Registered: 28th Dec 05
Location: Chorley, Lancashire
User status: Offline
|
to increase fuelling you can fit any spi injector into that spi throttle body. You can also change to a larger spi throttle body from a 1.4,1.6,2.0. also you can fit a 1.4 spi ecu on to your loom.
I built a 1.2 spi for a customer last year, raised the compression, fitted a gte camshaft, 2.0 throttle body which required opening out the top of the ilet manifold for the butterfly to clear, 1.4 injector and ecu and made up a new cold air feed system as the standard nova/corsa intake is very restrictive.
chris.
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
quote:
Originally posted by rallyman
to increase fuelling you can fit any spi injector into that spi throttle body. You can also change to a larger spi throttle body from a 1.4,1.6,2.0. also you can fit a 1.4 spi ecu on to your loom.
I built a 1.2 spi for a customer last year, raised the compression, fitted a gte camshaft, 2.0 throttle body which required opening out the top of the ilet manifold for the butterfly to clear, 1.4 injector and ecu and made up a new cold air feed system as the standard nova/corsa intake is very restrictive.
chris.
Thanks chris for your reply. Could you pls check your U2U as i have sent you a message, and a few questions if you don't mind. Cheers
|
johnny27
Member
Registered: 5th Feb 06
User status: Offline
|
Did you do this conversion yourself? How did you work out the 2.0 spi tb to fit to the 1.2 manifold? Did you just cut metal?
|
