Lancia Integrale 8v piston to head clearance

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Ozze
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Lancia Integrale 8v piston to head clearance

Post by Ozze »

Hi

Im about to build a new motor for my dedra integrale. Will be forged pistons and forged H-beam rods, with all balanced internals and new bearings. Have dry fitted the rods and pistons in the block (wich had to be decked since it wasnt level 0.09mm) Now the pistons protrude quite a bit from top of the block (around 0.5mm) meassured roughly, since i dont have the H-beam rods home yet. The H-beam rods are suposed to be standard spec som it should be the same. The head gasket im using is 1.02mm thick, and consists of 3 metall layers (cometic) and im thinking the clearance left will be too small?

Engine is a turbo engine and hope to produce 300-400 hp, going to be used as a track day car.

Edited:the subject was wrong, engine is 8v not 16v

Regards
Ozze
Last edited by Ozze on August 2nd, 2006, 8:05 pm, edited 1 time in total.
Guy Croft
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Post by Guy Croft »

OK

Ignore clearances for now; the biggest danger you face is the effect this has had on the compression ratio. The 8V Integrale runs 8/1 static CR with up to 1 bar on overboost. You are aiming much higher; you're going to need to reduce your CR because you'll need 18-20psi boost to get that power. Your CR for that boost needs to be much lower than standard. For 20 psi - 1.4 bar I'd be running between 7.2 and 7.5/1 max, or she'll likely detonate.

The compression ratio is a function of bore size and head volume, piston bowl volume, clearance of piston above or below block, gasket etc etc. You have not indicated that the piston bowl (dish) has been made to lower the CR. Even if you are running standard 84mm bore size, I estimate your compression ratio is going to be over 8.0/1 to start with. See below.
This by the way is from known 8V CR and production piston height data only as I do not have an accurate cc figure for your piston bowl. I have set it up to allow for what I think is the piston bowl volume and oyur pistons set up 0.5mm above the deck. i have assumed standard bore size. If you give me the bore size, burette measurements of piston bowl and combustion chamber we can make it more accurate.

You also need a minimum of 20 thou" piston to head - measured with compressed gasket and piston fully 'rocked' over - they tilt at tdc - quite a bit. I would be more comfortable with 1mm (40 thou"). The other problem you have is the reduction in piston to valve clearance from running the pistons so high. You need certain clearances vertically measured in the plane of the valve axis and radially.

You can certainly reduce the CR with the 8V by removing metal from the head but there still remains the piston - head and valve issue.

You know, readers, I write this well-meaning advice, it works, you read it and use it. But when it comes to trying sell things, pay for it all, all I hear is: 'Oh, Guy Croft's so expensive...' I hear it from everywhere. 'I'd like to buy your parts but my wife wants new kitchen...' My 'cheaper 'competitors win again. I get their engines to fix after a while.
Get the pistons wrong and you end up paying twice over for them. Get them from me, sure - not at all cheap - I do my own expert CAD design that the supplier reads from email - so we have full traceability and they will be exactly right for your engine.

GC

(Edited by GC for 8v Integrale head, I had assumed 16v)
Last edited by Guy Croft on August 3rd, 2006, 8:43 am, edited 4 times in total.
Ozze
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Post by Ozze »

Today i burrated the pistons bowl, and they are 18ml big. And the head has standard combustion chambers, std turbo head so that should be 47.7cc acording to Fiat workshop manual.

What would that give in static compression, with my current headgasket (1.02mm thick) Cylinder bore is 84.35mm and piston diamater is 84.26mm.


Regards
Ozze
Last edited by Ozze on August 4th, 2006, 1:11 pm, edited 1 time in total.
Guy Croft
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Post by Guy Croft »

OK Ozze

Here is the CR calc revised with your stated piston bowl (not dome) volume, gasket thickness and head volume:
Attachments
CR way too high mainly because pistons are too high in block. 8.33/1<br />Ignore the squish band data, that's for working out bolw volumes.
CR way too high mainly because pistons are too high in block. 8.33/1
Ignore the squish band data, that's for working out bolw volumes.
Int 8v CR - Ozze.JPG (76.1 KiB) Viewed 7951 times
Ozze
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Post by Ozze »

reading this excel calculation you have done and reading your first answer, i guess the compression ratio i get will be too high to boost around 1.4-1.5bar (or up to 2.0bar) ? Even if i use 98 octane fuel? I can even get 100 octane fuel from the gassations here (Sweden), would this help?

Should i then get the pistons shaved of 0.5mm of the top? this should also decrese compression somewhat? What else can i do? Would racefuel help?

Regards
Ozze
Guy Croft
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Post by Guy Croft »

No way, get your CR down to 7.5 or lower. You don't run high boost high CR, ever with turbo units.

Read:
http://guy-croft.com/viewtopic.php?t=14
for guidance on piston to valve marking out and clearance. You can make the VRs as big as you like, it will help lower the CR.

Mill the pistons down to clear the head. Open out the combustion chamber as well to increase the volume, it's easy on that head. You can shorten rods too, by resizing off original centre, not easy but do-able.

Or just sell the pistons to someone who can use them and start again.
Attachments
CC's opened out on a head of similar layout to 8V Integrale.
CC's opened out on a head of similar layout to 8V Integrale.
pic 010.jpg (115.54 KiB) Viewed 7940 times
Ozze
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Post by Ozze »

What would the compresion be with 0.75 shaved of the pistons and all other values as said before?
How much would be possible to boost with this cr?
What possible horsepower would that give?

Regards
Ozze
Guy Croft
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Post by Guy Croft »

Ozze, now you're going to have to do some of this yourself.

E mail me for the CR calculator, aim for 7.5/1 with 20psi boost or 7.2/1 with 25/30 psi boost. I am not making a bhp prediction, I don't know nearly enough about the engine.

GC
Ozze
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Post by Ozze »

How can one calculate or is it just "seat of unacceptable" that say how much one can boost with a specific static CR? I now camshafts will make difference to dynamic CR but there has to be some sort of standards to work after?

If standard integrale 8v runs 8:1 and boosts 1 bar, with 65% ve it would run 10.14:1 (dynamic CR) and needs 95.92 octance fuel
7,2:1 and 1.4bar boost would need 98.92 octane and use 11.14 (dynamic CR) Still with 65% VE.
(This is calculated using TurboCalc, from turbofast.com.au)

//Ozze
Guy Croft
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Post by Guy Croft »

It is totally a question of actual experience, what static CR you can run with any boost. Unless you ahve extremely expensive/advanced software to model the whole engine package, which few can afford.

If you run with the figures I gave you you won't go far wrong, they are from my own exp.


GC
Ozze
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Post by Ozze »

Got the mail today.
Thanks for your help guy

Regards
Ozze
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