3 Litre engine build started

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3 Litre engine build started

Postby spryboy1974 » Thu Apr 12, 2007 7:09 pm

I have now stripped down my Z7X Laguna engine ready for its re-build.
I have also got the supercharger i will be using! :D

The charger in question is from a 3.2 V6 AMG merc.
This engine runs 9:1 compression and runs 1 bar of boost producing 350BHP.

This has now thrown up the question for me again about what compression ratio to run.
I have worked out that the standard Laguna engine,(9.5:1), has a static comp ratio of about 9.3 and the dynamic effective comp is about 7.4.
Not sure how accurate that is,(i used calculators from another website),but can anybody tell me what they mean and why do we need to consider them when building an engine!? :?

Do i go for DG's 7.6:1 forged pistons,Wossner can do standard 9.5:1 forged pistons or maybe something in between??

I know i have talked about this with you guys in the past but i am still a bit confused, sorry! :oops:
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Postby simontaylor » Thu Apr 12, 2007 9:41 pm

sounds good, keep us all updated on progress.
and some pictures would be nice too.
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Postby Stunned Monkey » Thu Apr 12, 2007 11:59 pm

Dave can't supply 3 litre low comp pistons. I will be getting some made soon for about a grand a set but it'll be a few months yet, got to make some money first :) The static CR of a NA laguna/safrane engine is 9.6:1 dynamic CR is down to when the inlet valve closes. Google it for more info..
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Comp ratios

Postby Tony Smith » Fri Apr 13, 2007 2:03 pm

Lower compression means you can run more boost or ignition advance (or a combo ) before you get pre -ignition (pinking/det). Sticking with the high compression will mean you'll need its ignition map to be very accurate and it will have a far smaller safety margin if the car is used in extreme conditions.
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Postby David Gentleman » Sat Apr 14, 2007 1:39 pm

Stunned Monkey wrote:Dave can't supply 3 litre low comp pistons. I will be getting some made soon for about a grand a set but it'll be a few months yet, got to make some money first :) The static CR of a NA laguna/safrane engine is 9.6:1 dynamic CR is down to when the inlet valve closes. Google it for more info..


Yes, I can....£750 a set with rings...
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Postby Stunned Monkey » Sat Apr 14, 2007 9:36 pm

Oh, so you CAN now do them.... ? You told me you could only do them in batches of 24 (4 sets). What's changed?
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Postby clee » Sun Apr 15, 2007 7:56 am

Mayhap he's bought a lathe :?: :lol:
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Postby spryboy1974 » Sun Apr 15, 2007 9:06 am

I'm sure i have asked you this before Martin but,what comp ratio will your pistons run? :?
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Postby spryboy1974 » Sun Apr 15, 2007 9:08 am

DG,i notice that your pistons have pockets in them and standard A610's are flat top???
Will this not bring down the comp a bit?? :shock:
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Postby Stunned Monkey » Sun Apr 15, 2007 1:25 pm

They don't look like PRV pistons. They're from a 4 valve-per-cylinder engine (24v PRV pistons aren't pocketed). Probably just a catalogue photo...

The LM600 slug I'll be copying obviously came from a 24v engine... I have made comparisons to a standard piston and there's a difference appropriate to a standard A610 CR but I haven't checked it.
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