Changing injector and TB on spi

[johnny27]

Got myself a little corsa 1.2 SPi 8v. Since its a 1995 corsa converting the head to 1.2 or 1.3 carb type and a twinchoke is not legal, as i don't think a carb can run with a cat, plus things are really tightning up with emmision test on the MOT in NI. Pitty though, as i had really good power gains with the whole carb and carb head setup.

Anyhow been told i can fit a 1.4 or 1.6 Spi injector, and a 1.4 or 1.6 TB with no mods, i think the only TB that need mods is the 1800 and 2000.

Can anyone tell me if the 1.6 spi TB is a straight swap, and also what vauxhalls came in 1.6 with spi system?

Also been told that i can swap my 1.2 ECU for a 1.4 ECU, apperantly its just a straight foward plug out plug in job, anyone confirm?

I'm asking these things because i am currently fitting a 285 deg kent cam with great difficultly lol (see my other thread) and i have been told by alot of people over on corsa sport that i will need to upgrade the fuelling to get the engine to run properly. Cheers

[Adam]

Use a 1.8 SPI tb, with a 1.6SPi inlet manifold. The 1.8 tb has a larger throttle plate than the 1.6 one.
The 1.6 inlet will need porting out slighter as its a few mill smaller than the 1.8 tb.
Fit the injector out of a 1.4SPi tb if you want,see what it drives like compared to a 1.2 injector, but any bigger than a 1.4 injector will flood the engine

1.6SPI engines were fitted to mk3 astras, and mk3 cavaliers iirc. 1.8spi is fitted to mk3 cavaliers. Should be able find plenty in a scrappy.

The ecu will plug straight in, but i would stay with a 1.2 ecu.

It will be interesting to see how a SPI engine runs with that type of cam fitted.

[johnny27]

Thanks mate, i've never really worked on SPi systems, or even any injection systems, but the spi seems striaght foward enough. So Is the throttle body the whole unit that sits on the manifold, or is it just the top part (the bit with the flap?) or even the bottom part where the flap is? Thanks mate, you've been very helpul
BTW i think i remember you saying before you have a modded SPi? What sorta power gains does the 1800spi TB and 1600 manifold give? roughly?

[Adam]

I haven't done the 1800spi tb and 1600 manifold on mine yet, but i've been told it drives much nicer with it fitted, seeing as the throttle plate is larger so more air can be drawn in=more fuel=more power. In theory.

The throttle body is the whole part that sits on the top of the inlet manifold.

[johnny27]

cheers man, i would be stuck without your knowledge of engines, i hope you don't mind me asking you all these questions, as i'm pretty well in the know how with carbs and 8v valve small block engines, but did'nt realise to lately that the 1.2 Spi unit could be tuned, i have no experince with them other than chucking them in the bin for a 32/34 or T40s, but you seem to know alot about the SPI.
Could you estimate a rough BHP figure with the 1800 TB, 1600 manifold, 1400 injector, 285 kent cam fitted, and the car has already had a decat, straight thru enlarged centre section, and a rage back box? the car also has a foam universal air filter, not that would make any differnece to power whatsoever, just sounds abit better, and there is a slight increase in the throttle response.
Bearing all the mild mods in mind, what bhp could be expected of this C12NZ with 45bhp std? And also i plan to fit my 4-1 branch manifold from my nova, so could you give an estimate with that fitted as well
I don't expect it to be much as the engine is so restrictive with the orgianl spi head and ports. thank mate

[Adam]

Im not sure what the cam will be like on a SPI engine.
With a de-cat, full system,4branch, gte cam, i think Aragorns brother got around 60ish bhp.
So depending on what the engine runs like with the cam fitted, you would probably be around 65ish bhp.

Only way to be sure what its running like is to get it on a RR tho. I've not had mine on one, but it drives miles better than a std 1.2i, with a std engine i struggled to get to the limiter in 3rd, no probs now tho.