Moorron
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| posted on 2/2/07 at 10:23 PM |
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max compression ratio for a turbo conversion.
is there anyone here who can work out whats the most boost i can run on 98 octane fuel and an engine with a cp of 10.5? one of the lads at work said
on 95 octane fuel i am on the limit to detonation (assuming air temp is low) at 5 psi, but i want to double check this with some of the peeps here.
Im trying to get away from lowering the cp as it means more work and cost for a locost turbo conversion on my cbr1000f engined mk indy.
ps, the guy who 'worked it out' converted a harly to a supercharged one for his final year uni project and is a right number crunching
nut. I trust him, but looking about on the net i see that most turbo bikes look for about a 8.2 cp ratio.
is it going to go.....BOOOOMM? lol
Sorry about my spelling, im an engineer and only work in numbers.
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BenB
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| posted on 2/2/07 at 10:56 PM |
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For this kind of thing I'd recommend
"forced induction performance tuning" by A. Graham Bell from which the following diagram comes....
Crap. My website seems to be insistent on not taking a link to it. See photo archive 
BTW it states that a reduction to RON95 will require a CR reduction of 1.5....
[Edited on 2/2/07 by BenB]
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BenB
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| posted on 2/2/07 at 11:01 PM |
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PS it seems to show that for 98RON without an intercooler you're looking at 9.3(approx):1 at 5 PSI boost.....
8.2CP would allow a rather more useful 7-8PSI without an I/C but you'd loose power due to the lower compression.... Intercoolers make a lot of
sense!!!!
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Simon
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| posted on 3/2/07 at 12:41 AM |
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I'm using the standard 9.35 compression ratio with my R V8 and am going to run 1 bar (14psi), but I have a pair of intercoolers that should keep
the intake charge temp down to acceptable levels.
I'm not changing comp ratio for the obvious reasons - driveability, will retain torque characteristics, more power, and
"bovvered"
Would it not worth your while just getting a thicker headgasket - someone like holeshot may be able to supply.
ATB
Simon
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froggy
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| posted on 3/2/07 at 12:50 AM |
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ferriday at stafford have done me a copper head gasket for my cbr to bring the cr down to 9.5 and the uno turbo will have the wastegate set at 7 psi
running through an rs turbo ic its the fuelling that will cause the most grief as you really need to rig up an lc1 reader to set it up and keep the
afr on the rich side when on boost to keep the charge temps under control.At 5psi you should be on for 180hp but with al the fab involved it makes an
r1 swap look more tempting for all the hassle with the turbo conversion
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PAUL FISHER
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| posted on 3/2/07 at 01:08 AM |
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It all depends what you want from the car and what you are going to use it for,you have a choice,if your not going to run more than 6psi boost then
you can leave your compression ratio as standard on most bikes,some bike engines are stronger than others,for every psi boost for a bike engine your
looking at adding around 10bhp,so a fireblade lump120/ 130bhp+6psi boost would result in 180/,190bhp,this would be within safe limits of engine
internals.If your going to run anything above 6psi on any bike engine then you have realy got to start looking at reducing cp ratio,stronger pistons
and rods,and crank,intercoolers or chargecooler,and or water injection,if you want reliable bhp,it all comes down to £££ at the end of the day bhp
costs.
[Edited on 19/05/04 by PAUL FISHER]
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Moorron
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| posted on 5/2/07 at 09:01 AM |
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Interesting responces.
Im trying to avoid using a thicker head gasket for 2 reasons, greater risc of h/g failure and by lifting the head up will adjust the cam timings which
will then need to be modded to bring back to normal.
Nice to see that if true i can get 190 bhp out of mine with 5 psi. i also would never fit a turbo without an intercooler or charge cooler. so charge
temp will b controlled if i can get the air out from under the bonnet.
just picked up th elaser cut parts, so now its just waiting for some turned bits to allow the manifold to be fabricated.
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Moorron
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| posted on 5/2/07 at 09:32 AM |
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Description
THE ELASTIC BANDS ARE OPTIONAL
Sorry about my spelling, im an engineer and only work in numbers.
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Simon
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| posted on 5/2/07 at 08:09 PM |
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Nice drill press - same as mine
ATB
Simon
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Moorron
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| posted on 6/2/07 at 08:40 AM |
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oops sorry about the pic size.
Made a silly mistake tho, the exhaust header clamps (that hold the headers into the ports) are too big! damn. im going to struggle to fit it all in,
made some dummy chassis rails up to see what space i am left with. but i think its do able.
Yeh the drill has saved me a few times, its just the right power too as when the drill bits stick its not strong enough to snap the drill so just
stalls.
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