is 8.5:1 now concidered ok for 400bhp?
25-06-2005, 11:13 AM
#1
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is 8.5:1 now concidered ok for 400bhp?
it seems that a while back everyone was diving for low 7's but now i'm hearing/reading more and more that higher CR is fine especially with good management and that better results are being gained etc
views please
8.5:1 C/r
http://photobucket.com/albums/v333/l...rent=comp8.jpg
7.5:1 C/r
http://photobucket.com/albums/v333/l...rent=comp7.jpg
views please
8.5:1 C/r
http://photobucket.com/albums/v333/l...rent=comp8.jpg
7.5:1 C/r
http://photobucket.com/albums/v333/l...rent=comp7.jpg
25-06-2005, 11:47 AM
#3
Lee, its perfectly possible to get 400bhp on 8.5:1 from a LET if that is what you are asking?
But bear in mind that the higher the CR the less boost you can safely run (although retarding the timing can help with that) and the less boost you run means less torque, which means in turn that you need to turn a lot of rpm to get the figures you are after.
Jap turbo motors do it this way, cossies boys historically have always gone for less rpm and more torque to get the same figures.
Many ways to skin that particular cat, but personally i would say in your instance you would be better off going a bit lower as you arent going to be too fussed about off boost performance anyway, so its a nice safety margin.
On decent fuel ignore all that and you can happily get 400bhp from big torque moderate rpm as it moves the det point so significantly.
But bear in mind that the higher the CR the less boost you can safely run (although retarding the timing can help with that) and the less boost you run means less torque, which means in turn that you need to turn a lot of rpm to get the figures you are after.
Jap turbo motors do it this way, cossies boys historically have always gone for less rpm and more torque to get the same figures.
Many ways to skin that particular cat, but personally i would say in your instance you would be better off going a bit lower as you arent going to be too fussed about off boost performance anyway, so its a nice safety margin.
On decent fuel ignore all that and you can happily get 400bhp from big torque moderate rpm as it moves the det point so significantly.
25-06-2005, 12:03 PM
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what impact does bore and stroke make i.e the fq400 evo has 85mm bore 88mm stroke 1998cc 8.8:1 C/r and makes the figures i'm after?
how can that be translated in to my 87x87 "square engine"
how can that be translated in to my 87x87 "square engine"
25-06-2005, 12:20 PM
#6
Bore and stoke is a complicated relationship, generally a long stroke motor will rev less (less valve area possible) but as im sure you are aware that doesnt really become an issue with the EVO, and likewise some other engines that are long stroke such as the Mi16 pug engine also rev extremely well.
Yours is 86mm stroke by the way mate, unless you have a custom crank?
Yours is 86mm stroke by the way mate, unless you have a custom crank?
25-06-2005, 12:30 PM
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Originally Posted by chip-3door
Bore and stoke is a complicated relationship, generally a long stroke motor will rev less (less valve area possible) but as im sure you are aware that doesnt really become an issue with the EVO, and likewise some other engines that are long stroke such as the Mi16 pug engine also rev extremely well.
Yours is 86mm stroke by the way mate, unless you have a custom crank?
Yours is 86mm stroke by the way mate, unless you have a custom crank?
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