I can't this time. You actually took your head out of your ass on one of your posts. Good job!

 

In my opinion.....If the block is new then leave the stock bore. If there is a decent amount of miles (about 20,000) on it then go .20 over. As you run the motor the pistons wabble in the cylinder. It creates an hour glass shape inside the cylinder. This leads to the gap on the piston rings changing and it goes up and down. If the gap in not check through the whole cylinder it may close and do more damage. At least with going .20 over you will most likely have a cylinder that is nearly perfectly striaght. Which will leave an even gap in the rings throughout the whole rotation. This also minimizes the pistons ablitity to wabble.

As for the .40 cooling issue.....My motor(2.3 stroker 9.7:1 compression) had 61,000 miles of daily driving on it, before a faulty spark plug took one of my pistons out. I never had any cooling issues. I was on the stock radiator with just a slim fan. Now the only thing I did do was change the coolant once a year to make sure it was at optimal cooling ablity year round. My motor took the daily ass kicking I gave it. For the 2 1/2 years the motor was in my evo, it was at 520+hp on my 60 trim turbo. Then for another 6 months with my 6262 at 555hp. The whole time the car only saw 93 octane. I can not wait to get it back up and running and go for 600+ on pump 93.

Like I said this is my opinion. I am not out to offend anyone. I have engine building experience. I have built several engine before. This is just some of the things that I learned along the way.

 

 

I'm just going to say this.... Raising the compression does not spool the turbo faster, it raises the VE of the engine and creates better transient response under the curve. By doing this the engine makes more power on it's own which also creates more power per psi of boost than a lower compression engine. Where a lower compression engine would need more air and fuel to make power, the higher compression engine will make the same numbers with way less boost and fuel. So since the higher compression engine makes more power per psi of boost it gives the illusion of faster spool... example: a 12.5 comp engine at 13psi would out power a 9.0l at 20psi.

The downfall, it does create more heat, and with heat in the cylinder comes pre ignition/detonation which leaves you having to run a higher octane fuel to fight this off. So my suggestion is, if your building a fun street car which you are not the only driver of but used as a daily, keep your compression down for better use and power from lower octane fuels. If this is a purpose built car for weekend fun or competition, then high compression will make you the most power pound for pound... Just make sure you re-up on your head studs to keep the head on the block

Ask me how I know this....



I speak from experience....

When my wife gets another car and will no longer be driving mine, my next engine will be a 11.0:1 with alky injection - lots of it.

 

Actually it does affect spool. Higher comp ratio is more engery displacement or more energy efficient. The spool wil be quicker if all other things are eqaul, it will make more power at same boost, and more heat, which makes tuning a little more dificult at higher boost.

 

Sorry man, obviously you built more high compression boosted cars than I and know it all. Even the guy I hate - buschur will tell you the same thing, but I'm sure you know more than him too. This is why I don't post on TR much anymore, to many know it alls and not enough do it alls...


Here is a post by an engineer and one of the wisest people on evom... and I was wrong about VE, it increases exhaust gas efficiency

 

[QUOTE=THE_ONE;8700857]
The downfall, it does create more heat, and with heat in the cylinder comes pre ignition/detonation which leaves you having to run a higher octane fuel to fight this off. So my suggestion is, if your building a fun street car which you are not the only driver of but used as a daily, keep your compression down for better use and power from lower octane fuels.[QUOTE]

I plan on running e-85 daily. would that knock greatly reduce my chance of knock?

 

Greatly you lucky bastard, I wish I had a few stations around here.

 

also, to ask a stupid question...again lmao
would I be correct in assuming that even tho a high compression boost build does not spool faster, but does however achieve the same power as a high-boost/low compression car at a lower psi level, that a high compression boost build would actually hit that power alot sooned since it only has to spool to let's say 13lbs compared to 20lbs?

did that make sense or did I word it wrong?

 

well apparently Houston has alot of access to e-85 so alot of people out here run it daily. maybe this move wasn't such a bad thing haha