Hello from Czech Republic

I have a question on all of you. Here in Czech I am doing amateur rallying/hillclimb racing with 1.1 Spi Cinque. I know, this thread has been here for like milion times but I need help.

I would like to get mods like 75 exhaust manifold, 75 re profiled cam and 75 TB with better air supply to the engine. Is there any mods that I can do? Like skimming the head for like 1mm or get bigger injector or fuel pump?

I need to stay with the 1108 engine because regulations but swapping the 1242 60 engine could possibly be nice because these engines lookwise are the same.

Thank you for your help.

p75 throttle body won't work on an spi, contact Sparky5 on here and he can supply you with a 40mm enlarged TB.

a p75 exhaust manifold will sit quite low under the car as the 1242 engine is taller, better to get a decent 421 manifold from the likes of supersprint that's for the 1108.

866 cam from a p75 will work, gives you a bit more lift over stock. But a proper cam from Piper, C&B or other aftermarket cam company will make much bigger difference.

Head skim will improve things as it will on any car.

bigger injector is totally pointless and will just make it run crap, think of an engine as an air pump not something that burns fuel, to make more power you need to get more air through it and only when the fuel system can't keep up do you need upgrades there.

be careful swapping engines, if you know what your looking at it's very very clear whether an engine is 1108 or 1242 as soon as you open the bonnet.

Sounds like you should read the regs of whatever your entering in detail and decide how much you are happy to spend before you do anything at all tbh.

Hello,

Thanks

As I said, N1400 - stock cars to displacement 1400ccm. The engine cas be upgraded but can't be swapped or for example the injection has to stay monopoint as it is. So that's why I asked for bigger TB and etc.. Also I thought that 38mm from p75 will work.. Some guys here says that it is working as piece for piece conversion.

the P75 throttle body doesnt have an injector as the p75 has a mpi fuel rail and 4 injectors..

It does physically bolt on, and you can split the top and bottom so you could in theory put the top half with eh spi injector on top and have the lower p75 part with the butterfly (which is 38mm) - but they don't marry together nicely with a nice smooth curve down into the butterfly, so would need modification to work well.
Sparky5's 40mm throttle bodies are well known on the forum and beyond, tried and tested and well worth it. As i said before, an engine is essentially an air pump and improves on getting air into and out of the engine is where the power is made..

Without looking at the exact rules and what is an isnt allowed and is allowed its hard to say what exactly i'd do.. if you must keep the spi setup then the 40mm throttle body is definitely the right way to go - if its more the engine must be the same i'd look at ditching the spi setup entirely cause the statement the engine cant be changed but mods are allowed to me means you could change the head and possibly slap a pair of twin carbs or ITBs on.. Whats the rules on engine management too, can you use aftermarket management, can you ditch it entirely and go to carbs etc.

Got a link to the rulebook?

blu73 said:

if its more the engine must be the same i'd look at ditching the spi setup entirely cause the statement the engine cant be changed but mods are allowed to me means you could change the head and possibly slap a pair of twin carbs or ITBs on..

Click to expand...

He says it's gotta stay SPI.

I'd look at the Formula 750 cars, I'm sure they're restricted to SPI as well. Jenvey do some SPI single throttle bodies but you'd probably need a lot of customization to get it to fit and work with the FIRE.

yes i know Dunc, I was trying to get at if thats exactly what the rules say or if that was the understanding of the rules... spi setups are pretty rare and I don't think this is limited to just a car.. Most cars even of the cinqs era didn't have spi, so the rule must be more around the fact the fuel system can't be altered in certain ways but the original post also talked about changing the fuel pump and injector so I'm just not sure what the rules actually are exactly :shrug:

Formula 750 cars are restricted to using 1 choke of a 40mm carburettor.