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Technical 1242 8v SPI Preparing Engine For Turboing

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Technical 1242 8v SPI Preparing Engine For Turboing

On a hi-boost turbo engine I'd look to going down to at least 8.6:1 compression ratio, this is what VAD hi-boost converted cars run which i'm sur ethey based on manufacturers turbo cars.

To give you an idea on some manufacturer cars ratios.

The VAG 20VT engine 150 or 180bhp forms are 9.5:1 on the higher boost models ie 210-225bhp models they are 8.9:1.

Some more examples of charged cars MINI Cooper S runs 8.3:1 standard and Wossner forged pistons are 8:1 to run higher boost levels.

Again using Wossner pistons as an example, when turbo charging a Clio 172/182 you drop compression from 11:1 standard to 8.5:1, conversely if keeping it N/A and tuning it you raise compression to 12.6:1! Ford Duratec 2L16v turbo conversion goes from 10:1 to 8.5:1

Lancia integrale 2L 16V 8:1
Renault 5GT Turbo 7.9:1 for more boost 7.5:1
Fiat Uno/Punto turbo 93-97 7.8:1
Fiat Uno turbo 90-92 7.7:1
Subaru Imprezza STI Verstion 9 8:1
Ford Escort Cosworth 8:1
Fiat 20VT 8.5:1 for more boost 8:1
Nissan Pulsar/200SX etc 8.5:1 for more boost 8:1
Nissan Skyline 2.6 twin turbo 8.25:1 for more boost 8:1
Mitsi EV0 3 to 7 are 8.8:1 for more boost 8:1

So got to ask yourself, if manufacturers spend millions of pounds on engine development and thousands of hours on test beds not only tuning them but in durability tests and have come up with these figures, it's probably best to base your own calculations on these figures.
 
I spoke with a engine builder who has been building engines for race since 1972. He claim that if CR is lowered to under 8:1 you will not have problems with detonation - all relative...
Of course you can provoke a detonation, but the engine won't be running on a knives edge regarding detonation/knocking if you have a CR under 8:1.

The MPi boost fueling will also save cylinder 1 and 4 from running lean and you will be able to raise boost a little more and push ignition forward resulting in even more power.

Regarding your question about skimming the head to max I will refer to davethetrike's quote above.
-/+ 0.9mm pr. 1:1 on a 1242cc sounds correct (I used +/- 1mm pr. 1:1)

You can contact Fiat and ask them how high the Cylinderhead are standart. When you have that figure you can calculate what CR will be with the 16v pistons.
 
16V pistons in an 8v! :)

Thats lateral thinking for you. Of all the forums I've visited during my research this tech cento one is the best and most innovative. You're all nuts and I wish I owned a Cento. They're just a wee bit tiny for me though.

Slinks, yer in good hands(y)

Edit, with that compression ratio you could really load the nos
 
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righto! update time. Muchos progress has been made on the thinking front! lol ;) The turbo is going to be 1242 8v MPI with the whole engine management handed over to Megasquirt running alongside an Innovate LC-1 Lambda. So i'm now on the lookout for a P75 head, although i have no money :(! Christmas is creeping up now too, hopefully someone will buy me a megasquirt! lol ;)

Anyways I had a day off work today so took a trip to the scrappy and treated myself to these little babies ;)



Thats right, p85 16v pistons and rods, that's what i'll be running in the turbo block, so as soon as i get some new half bearings for the bottoms they'll be going in here:

Please continue to follow my thread, I haven't given up i promise! For those of you who are wondering, the broom yellow Abarth cinq i bought is going to be the one getting the turbo treatment ;)

Thanks for looking

Lenny
 
looking good mate.

i'm not sure what to do with my engine at the moment. getting very tempted to buy another P75 engine and build it up, ready for being turbo'd.

my current engine is a very good n/a engine - but with the head skimmed like it is..
 
arc said:
looking good mate.

i'm not sure what to do with my engine at the moment. getting very tempted to buy another P75 engine and build it up, ready for being turbo'd.

my current engine is a very good n/a engine - but with the head skimmed like it is..
Click to expand...

hmm, thought you were going with methanol injection, high comp. high boost? or have you thought better of it now?

Lenny
 
arc said:
it's an idea, albeit a very very silly one..
Click to expand...

haha, what turbo cinq isn't a silly idea? :rolleyes: I hear what you're saying though, might be more trouble than it's worth! would be surprised if it was without problems.

Another question, Who could lend me a hand programming the MS when i get it all wired in? And could someone please work out the CR that I am going to arrive at with the 16v pistons fitted, Trickers thread says 7:8:1 would this still be correct after the head is skimmed? Sorry to be a pain!

Lenny
 
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arc said:
depends how much of the head you skim off.

i should be able to help with the MS mapping (y)
Click to expand...

but if i get a 2nd hand head, then get it skimmed before fitting it, how do i know if it's been skimmed before? can i measure it?

And nice one with the ms mapping, i have them maps that you gave me but neither of them suit the 7:8:1 compression ratio that was given by tricker one has got 8.0 written on it and one 9.8?

Thanks again

Lenny
 
they were only the igniton maps, and they're a base to work from. but they should run it.

u can measure the tops of the combustion chamber when the head is off, its a faff using syringes and parafin. but it works.
 
arc said:
they were only the igniton maps, and they're a base to work from. but they should run it.

u can measure the tops of the combustion chamber when the head is off, its a faff using syringes and parafin. but it works.
Click to expand...

i used that method on a mini head, i needed 22.2 cc's in 1 combustion chamber of the head to get a CR of 10:1

i found it hard to control the syringe tho,it kept sticking then when it did go it squirted it all over the place.:rolleyes:
 
Whiley said:
reckon you could get your hands on anymore of those pistons lenny?
Click to expand...

hmm, was a rare occasion they don't normally break engines. Just so happened that there was a p85 there with a mashed head (stripped threads on cylinder head extension bolts etc). I'll keep my eyes open whilst i'm out and about though. But I must say, Arc has first refusal as he asked me first

Will keep a lookout anyways (y)

Lenny
 
Alex22 said:
How much did the pistons set you back mate?
We're all 75 turboing :slayer: lmao!
Click to expand...

haha, all copying trickers idea!! the pistons, con rods, 16v inlet manifold, fuel rail and injectors and 16v TB set me back £30. I know i probably won't need any of that except the pistons and rods but though i'd get it while i was there cos thats the price i was paying.

Lenny
 
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