How much compression can 93 octane handle?

[edz250r]

Hey guys....I'm having someone build my engine at the moment. He does about 40 a year and knows what he is doing, but he told me that my engine should be between 195-200psi of compression with the ESR cool head and 21cc dome. It will also have a new bore/pistion (on 3rd bore) with mx porting. He said that I will be fine with this compression if I run 93 octane.
What do you guys think? I've heard over 185psi compression requires a mix of pump/race gas, but this guy knows his stuff so I'm confused.

Thanks....

[zedicus00]

93 is prolly fine. the highest i can get is 91 and i run around 185 compression fine. dont go over 200 and i would stay closer to 195 then 200 even.

[edz250r]

great, thanks.

I can even find 94 octane at a couple places, so I should be in even better shape using that.

[310Rduner]

Ask all the porting specs from the builder, which he should have already given you (don't accept "it's a secret") and compare against this chart.

[edz250r]

What chart? did you forget to include it in your post? :-)

Also, we agreed on a mild port that he said will give me more power throughout the powerband. I know a lot of people on rriders.com say that you either get low/mid or mid/high, but you can't get all three, but he said that you can still go a mild port which cleans up all the ports and can give you better performance at low/mid/high. He said that he could do a more aggressive port that would only hit low/mid or mid/high, but he wanted to keep it very dependable since i'm only a trail rider.

Do you all agree that a mild port can provide better performance from low all the way to high? I was recommended by several people to use this guy and he also works pretty closely with ESR, so it sounds like he knows his stuff.

[zedicus00]

yup i know a couple of places that do a good 'mo power everywhere' port job on 250R's it is jus concidered a mild porting. works good smooth power and ultra reliable.

[310Rduner]

Originally posted by edz250r
What chart? did you forget to include it in your post? :-)



....maybe....


shhhhh:o

http://macdizzy.com/compress.htm

[beerock]

put a 22cc dome and play it safe or run a 50/50 mix 195-200 is a little over board for 93 octane, even 94

[deathmetal]

Whats a stock 250r putting out on compression? What is the general rule of thumb for compression raises, example what else would bump it up?

[beerock]

i think 165-175?