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| Lower Comp - Higher Boost VS Higher Comp - Lower Boost https://www.ausmini.com/forums/viewtopic.php?f=5&t=33719 |
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| Author: | pristic [ Mon Jul 09, 2007 7:58 pm ] |
| Post subject: | Lower Comp - Higher Boost VS Higher Comp - Lower Boost |
Fella's, Whats the go here. My braiin hurts trying to think it through. If I run higher boost and lower compression OR lower boost and higher compression whats the difference? Eg/ 8:1 and 12psi instead of 9:1 (or more) and 4-6psi... Why is one better than the other, etc? Cheers, Peter. |
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| Author: | benjamin [ Mon Jul 09, 2007 8:32 pm ] |
| Post subject: | |
less compression more boost more power  higher compression will aid power but wil limit boost.
so set the compression dependent on the boost you want to run. there is more power increase with boost than compression 
but low compression will make it less powerful off boost. |
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| Author: | pristic [ Mon Jul 09, 2007 8:42 pm ] |
| Post subject: | |
Ok cool. As I thought... so we want to run it like we talked about... big boost 
Pete. PS: Picked up the High Flowed T02 tonight
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| Author: | drmini in aust [ Mon Jul 09, 2007 8:43 pm ] |
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Only downside of low compression with a turbo is it'll be a bit s-l-o-w (or a slug) down low before it spools up. Particularly with only 998cc. That's why kazjim rebuilt his last time with a 1098 crank in.
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| Author: | Maxi23 [ Mon Jul 09, 2007 8:44 pm ] |
| Post subject: | |
What about when running a supercharger DrMini ? |
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| Author: | pristic [ Mon Jul 09, 2007 8:53 pm ] |
| Post subject: | |
Supercharger is 'on' alot earlier so you wont have the same lag... but still a bit Kev, that just means ill have to hold the pedal and keep the revs at about 3000rpm before I let the clutch out... rofl... oh this is going to be one fun motor... (ill have plenty of orange clutches spare hehehe) Pete. |
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| Author: | sox61 [ Mon Jul 09, 2007 9:23 pm ] |
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Sorry to hijack but... Any thoughts as to how much boost is safe to run with 8.5:1 CR. 8psi? 10psi??? 12psi?? |
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| Author: | pristic [ Mon Jul 09, 2007 10:15 pm ] |
| Post subject: | |
The answer is 'it depends' Which part will 'break' first? Usually head gasket... if that holds, pistons collapse? etc... Pete. |
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| Author: | sox61 [ Tue Jul 10, 2007 8:50 pm ] |
| Post subject: | |
pristic wrote: The answer is 'it depends'
Which part will 'break' first? Usually head gasket... if that holds, pistons collapse? etc... Pete. Yeah, i know the story. Just wondering if anyone had experience with boost levels at certain comp ratios... I don't think my boost is excessive... We'll soon see
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| Author: | slinkey inc [ Tue Jul 10, 2007 11:04 pm ] |
| Post subject: | |
Carl, Metro Turbo engine has 9.4:1 compression standard. People in the UK are running up to 10psi with that but no more. (I love to state this fact when some people sau 9:1 is the limit for 7psi...well nah it's not! But it's the overall setup that makes it's ok to run larger compression.) Metro Turbo motor has strong pistons to take the abuse and fancy exhaust valve to keep the heat down (I think). So really 8.5 should be able to go beyond 10psi. Of course if you take my advice and blow you engine up...sorry. 
But I reckon you'll be fine. Providing your pistons are up to, your head, and gasket and that you use 98 octane ertrol always. |
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| Author: | low n blown [ Thu Jul 12, 2007 3:27 pm ] |
| Post subject: | |
7.5:1 compression ratio, with 21psi boost at full noise on lown blown. Pulled well from idle, went like stink over 3500rpm. |
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| Author: | Boostedmini [ Thu Jul 12, 2007 3:57 pm ] |
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i am using 7.6:1 and run up to 18psi, basically as a rule of thumb, 9:1 you can run 10psi or so, 8:1 you can run 14 or so, and 7:1 you can run up to 18psi etc. anything over 12psi you want an intercooler, strong pistons and good ignition system Grant |
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| Author: | justfanginaround [ Sun Aug 10, 2008 1:16 pm ] |
| Post subject: | |
i've always used the old schooll method of 8/8/8 8 psi 8:1 cr 8000rpm limit but if you look at it and add the numbers you get 24 so if you want to run say 10 :1 cr at 8000rpm you car safely have 6 psi |
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| Author: | Morris 1100 [ Sun Aug 10, 2008 4:20 pm ] |
| Post subject: | |
Has anyone thought of adding oil jets under the pistons to cool them? It is a bit fiddly to make but I think it could be worth it. |
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| Author: | awdmoke [ Mon Aug 11, 2008 9:50 am ] |
| Post subject: | |
Most of the UK turbo mini boys who bother with oil squirters just use Ford ones |
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