Right.

After scouring the forum for quite a while, I don't really have a definitive answer to a couple of questions.

-What is the limit of the standard SPI pump and injector? Some people say 80hp, others say 100, I don't know. I've heard sayings of Astra 1.6 injectors., not entirely sure it's necessary.

-The standard fuel pressure regulator, is it worth adjusting slightly?

The engine I will be fitting is quite modified, and I expect it to run 85hp+, I just want to make sure that standard fuelling is ok at this sort of range. The information is out there I'm sure, I hope this isn't a repeat thread.

Thanks

My guess is it'll be fine. On the SPI cars I'm not sure how you'd go about upping the fuel pressure -- maybe a restrictor in the tank return?

Only sure fire way of knowing is a wideband lambda/AFR (or get a rolling road to do a power run with lambda hooked up?)

The Trofeo cars went MPI (albeit, using an SPI ECU!) very early on, but you'd guess they never had to worry about emissions!

This thread makes interesting reading: https://www.fiatforum.com/cinquecento-seicento/72415-increasing-fuel-pressure.html

It mentions manually adjusting the regulator from the top part of the throttle body.

An AFR with a wideband is something I've been looking into. They're quite expensive, but at least then I get a definitive answer on whether I need to mess with the fuelling anyway. The rolling road run would be a good idea, cheers

So if they're running on an SPI ecu, was it just simple batch injection? That'd probably be overkill for me, an uprated pump might be a solution (if it indeed runs lean).

Razman said:

This thread makes interesting reading: https://www.fiatforum.com/cinquecento-seicento/72415-increasing-fuel-pressure.html

It mentions manually adjusting the regulator from the top part of the throttle body.

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According to that article from Wolf Direct Racing, forgotten where it was now, it's well worth turning up the fuel pressure just after a few small mods.

Wolf Direct Racing often spoke with forked tongue! Still, Custard put the article here. Worth a peek.

As for batch, semi sequential, sequential, etc -- the P75 ran batch too (albeit with a different ECU), the MPI cars run semi sequential (hence the cam sensor). I'd guess the euro 4 FIRE engines run sequential (CC1 should know).

Rolling Road as as a power run may be cheaper than a wideband (although it has no resale value!) and will give you an idea of where you've got to.

you can up the pressure on the spi by turning the little screw with an allen key. Its on the top at the front and will (if noone has ever messed with) usually have a small blob of plasticy stuff on which i guess it to stop it moving once set at factory.

Not sure what the oem pump can deliver but from my experience the fuel pressure varies quite widely as stock, I have seen as low as 0.8bar and as high as 1.2bar - i would say the stock pump is more than upto 85-90hp but you may want to check the pressure is not one at the low end - but do get a good quality inline gauge (fit infront of the TB) and measure it rather than just tweaking it up a little, too far and the will run crap. And change the fuel filter first too

But, and i can say this with quite a bit of coinfidence having messed with fuel pressures quite a bit that the actual pressure makes little difference to how the car runs so long as its not far too low or far too high. The ecu uses the lambda signal to see if the engine is rich or lean and adjusts accordingly. A nice wideband is nice so you can keep an eye on things but thats all it does - see it as a seperate circuit entirely as the management one. The narrowband the ecu uses cannot take a wideband signal as one is 0-1v whereas a wideband is 0-5v signal. Being that you have little to no control on the standard ecu to change how much fuel the ecu decides to chuck in i would say its not really worth the money to get a wideband really. I have one on my turbo but thats a bit different to a NA car running stock ecu.

The emissions tester at MOT station will give you just as good a reading of whether the car runs rich/lean/ok.

hope that helps your decision??

Good answer, exactly what I was looking for

I reckon I'll invest in a nice wideband at some point in the future, for peace of mind more than anything. I'll check that it isn't at the low end of that pressure range, just to make sure, and adjust accordingly I know that the gauge isn't completely necessary, and is more useful on a turbo car, but I'd like one anyways

My new 4-2-1 already has another bung in it, so that's quite convenient really! Very good info in this thread, I'll be sure to favourite it

Fingers, blu, thanks for the help. It's much appreciated as always

Problem with the MOT man, though, is that he'll not be able to test the car past fast idle, or under load (which is where the damage usually happens).

good point.. Again, don't think its much of an issue on a NA engine thats not really really heavily tuned though. If it runs ok then its probably not going to blow itself up unlike a turbo motor which can go pop spectacularly just from running a little lean but still run ok.

Why not consider getting a P75 head??

When i had my old car on the road it got rolling roaded at 86 hp , and 96 ftlbs or forque . and i got told and showen by the rr guy he showed me were the Injecor was maxing out , so if we turned the presure up a little it would just max out even earlyer in the rev range ???

i now have a astra injector in it needs to have a remap to make gains from it , ive had to turn the little screw down quite a bit , as when i fitted it , started up ran round for a bit to make the car get used to it , yeah it was quicker , but when it came to idel it would some time cut out , but when it was on tick over it was LUMPY as hell , V8s had noting on me , but if there was a way i could "remap" the critch chip to make use of the bigger injector , , For now fella Id keep hold of the Standard injector , Ill post more up when i can

A P75 head doesn't seem like a bad idea to be honest. If i was going that far however, i'd probably save up for some better engine management.

This engine might possibly make similar sort of power, so i'd be very interested if you come up with anything I'd been wondering about the astra injector, but without proper mapping (as you've said) i'd struggle to make it work properly.

I know that Lee on clubcento had an astra injector, but made use of a mappable ECU chip. It was superchip IIRC, but they're roughly £230 including VAT. Remapping the Mckritch would be a good solution, not sure if they can be mapped anyway?

I wish i could afford proper engine management......

You can get microsquirt kits or the Det 3 for about that money. But then you have to pay for the RR.

Razman said:

A P75 head doesn't seem like a bad idea to be honest. If i was going that far however, i'd probably save up for some better engine management.

This engine might possibly make similar sort of power, so i'd be very interested if you come up with anything I'd been wondering about the astra injector, but without proper mapping (as you've said) i'd struggle to make it work properly.

I know that Lee on clubcento had an astra injector, but made use of a mappable ECU chip. It was superchip IIRC, but they're roughly £230 including VAT. Remapping the Mckritch would be a good solution, not sure if they can be mapped anyway?

I wish i could afford proper engine management......

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It is not difficult to wire in the P75 ECU. Using the Cento loom and splice the injector wires. That's the common way of doing it. Obviously you would need key/codebox/ECu.

:yeahthat: trick is to find a P75 with all them bits still on it in a yard - they proper getting rare now.

I'll keep my eye out

Presumably if i decide to run an MPI head, ill need a better fuel pump. Any recommendations?

Also, can the P75 ecu be remapped?

Razman said:

I'll keep my eye out

Presumably if i decide to run an MPI head, ill need a better fuel pump. Any recommendations?

Also, can the P75 ecu be remapped?

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Why do you need it mapped?

Yes, any out of any MPI fiat car . I use one from a mk2 punto.

Why do i need it mapping? Because race car! Nah seriously, it'd just be to optimise the fuelling. But it'd probably be fine as is.

The pump seems like an easy change then What would be the problem with using a mk2 punto head then, along with ECU? Cam sensor?

It's probably a stupid question, but im curious

Razman said:

Why do i need it mapping? Because race car! Nah seriously, it'd just be to optimise the fuelling. But it'd probably be fine as is.

The pump seems like an easy change then What would be the problem with using a mk2 punto head then, along with ECU? Cam sensor?

It's probably a stupid question, but im curious

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It's not a stupid question. People just say P75 head is just assume to get the P75 inlet and exhaust mani (is a much better deisng than the P60/cento one).

If you could get a Punto MPI head (up to mk2b), then i don't see a problem at all.

This is just from my reading not something I have done myself, i am 16v all the way haha, but I do see the attraction of the P75, I wouldn't go with SPI.

Ming

Thanks ming

It might be much easier to find a Mk2 head, so if it's possible ill probably go with that.

Ill have to research it a little more though!