hobbsy
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| posted on 10/7/10 at 11:36 AM |
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Turbo R1 - lowering compression options??
Anyone with experience suggest which is the best option:
1) double up on std head gaskets - feels a bit of a cheap and dirty way, may not give enough of a drop and will it be as reliable as the other
options?
2) thicker cometic head gasket. I'm enquiring as to prices and thicknesses available
3) decompression plate (from Ferriday engineering or similar). Doesn't appear to offer a price advantage and you still have to use a standard
head gasket. The plate itself is re-usable I believe and is available in copper or aluminium. Seem to be made to order so I can have whatever
thickness I want.
I haven't got as far as compression ratio calculations (or even decided what comp ratio is appropriate for the boost I'm looking to
run).
I'm thinking <10psi certainly. I believe others have run around a 1.6mm gasket..
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maximill666
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| posted on 10/7/10 at 11:56 AM |
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Either fit low compression forged pistons, but that involves a complete strip of the motor to split the case's which can be a bit of a pain, but
are a worthwile investment if you do plan to go beyond 10-12psi+ or easiest way is to fit a thicker Cometic head gasket.
I went with a 51 thou thick cometic gasket which will lower compression down to around 9.5:1, if you go any lower off boost performance will suffer.
Stock head gasket thickness is 23 thou, but if you double up on stock head gaskets dont expect them to last very long at 10psi.
I would recommend ordering from Rob at Cometic europe, they are a special order and have to be made at cometic in the states and take 3 weeks from
order to delivery, cost is around £70 if I recall correctly.
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sebastiaan
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| posted on 10/7/10 at 11:58 AM |
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Can you not space up the barrels? I've seen this done on a number of bikes, but am not sure if the R1 uses seperate cylinder barrels...
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hobbsy
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| posted on 10/7/10 at 12:02 PM |
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I wasn't seriously considering option 1) but I thought I'd put it in there for completeness more than anything else!
51 thou = approx 1.3mm
At 9.5:1 how high do you think you could go boost / power wise?
What pistons where you considering. TBH I was going to go the stock engine and low boost route but then someone sold me some cheap H beam rods! 
Are the cometic gaskets re-usable?
And to put it into context how much is a standard head gasket?
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CraigJ
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| posted on 10/7/10 at 01:02 PM |
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fit a thicker base gasket/spacer.
A guy i used to work with did one on his gsxr and ran about 7-8 psi with no problems.
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JohnL
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| posted on 10/7/10 at 01:32 PM |
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Disclaimer: No personal experience, just what i have read in books.
Using thick head gaskets and/or spacers increases the distance from the top of the piston crown to the cylinder head, supposedly facilitating
detonation, which can be destructive especially in (very) high RPM.
Since you will be applying less than 10 psi you will have a relatively trouble free engine (possibly as trouble free as an unmodified one) with forged
internals. Another small benefit is that forged pistons and rods are usually lighter than the cast equivalents, so you will rev a bit faster too ...
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maximill666
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| posted on 10/7/10 at 02:35 PM |
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A block spacer is not on option as the barrels do not separate from the crankcase
At 9.5:1 around 10-11 psi of boost will be fine, power produced and how early in the rev range it builds will depend upon what turbo you use.
If you are fitting those H-beam rods then whilst the motor is completely stripped I would reccommend fitting JE low compression turbo pistons &
you can run a stock thickness cometic head gasket.
As far as I'm aware you cant reuse the cometic head gasket.
Stock head gaskets are around £40
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turbodisplay
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| posted on 10/7/10 at 04:55 PM |
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Its ture that increasing the distance from the head will affect squish, increasing detonation tendancies, however i think that is more of an issue on
2 valves per cylinder engines.
I`m doing option 4) make your own metal shim head gasket, center foms the extra spacing, 2mm in my case.
Darren
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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hobbsy
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| posted on 11/7/10 at 09:35 PM |
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Just looking at the low comp JE pistons.
They do 9:1 and 10:1
Need to decide which to go for.
If I go for these I guess this now becomes a fully built engine, which wasn't what I was planning at the outset but means if I get greedy for
power I can turn the wick up a bit 
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