High compression question
Posted January 13, 2007 - 08:56 PM
Posted January 14, 2007 - 05:56 AM
Hi, I was thinking of buying a high compression piston for my wr450 2003. The standard compresstion is 12 to 1 i think ( correct me if I am wrong). I was thinking of switching to a vertex high comp 13 to 1 piston, If I make this switch to the 13 to 1, will I have to use race gas, I don't mind using high test but I don't want to have to buy race gas every time I want to fill up.
I tried it I have an 03 WR 450 and I weigh 290 Did'nt do anything for my power in fact took away from the top end. I went back stock and pulls great.... This is not like a car engine higher is not better.. Stock is awesome You shold be using race fuel now just like EVERYONE!!! Pump gas is TRASH its the lowest quality in the world... It's made for low compression fuel injected emmission controlled CARS!! If you need more power for you!! Then I suggest A CR 500.. If not then just go back with a Wiseco ultralight stock compression good luck.. Oh yeah and some cams might help go with the YZF 450 cams...
Posted January 14, 2007 - 10:10 AM
Posted January 14, 2007 - 10:41 AM
Posted January 14, 2007 - 10:49 AM
Posted January 14, 2007 - 11:25 AM
Posted January 14, 2007 - 11:46 AM
Posted January 14, 2007 - 05:37 PM
Posted January 14, 2007 - 08:18 PM
Posted January 14, 2007 - 08:24 PM
it really depends on the bike,a fellow tech has a klx650 bored to 700 and a je 13 to 1 piston with just about 70 horse and he uses 93 octane with no problems.so i would give it a try at least you may be able to get away with it.
Agreed. There is "mechanical compression ratio" and this is the number you see, and then, there is "effective cylinder pressure" which takes into consideration, valve lift, opening, duration, overlap etc. Basically, this squeeze doesnt take place until the last vavle has closed. So mechanically, compression ratio can be high, but squeeze can be lower. Now if you dont change anything except the higher compression piston, you will also raise squeeze. And a larger bore will also raise compression. As compression ratio is "the area above the picton at TDC vs BDC, and with the oversized bore, the area above the piston at BDC will increase, while area at TDC doesnt, effectivly raising compression ratio too. Most late model cars now come with a compressio ratio of 10.5 and 11:1, doing this while running regular gas because of variable valve timing.
Posted January 14, 2007 - 10:03 PM
Posted January 15, 2007 - 07:12 AM
If you do this for a livin then you should know NOT to run the lowest octane you can!!! How long ya been doin it? And did you know that the fuel we use for the cars is not worth a darn!!! If ya'll are just trying to save money than maybe you need to get into fishin!!! This is crazy if you really think that!!! Race fuel has additives that keep the cylinder temp down and this creates MORE horsepower period... I've been doin it since 1980.. High compression causes problems for the bike.. It will NOT last as long as stock!!! Stock.. The word is not the same as using stock for a car!!! Like your ford truck is stock... put compression on it and it will run great cause it has 8.1 compression. These bikes come out of the factory race ready, but most of you dont race, so why do you want to go all out and pimp these motors out? Can you handle the power all the way through and stay WFO through the whole race? We race every series TCCRA,TORN,WORCS,TORCS,STORM,PRO CIRCUIT, And All the other mx series I do NOT see but maybe 10% of people with high compression.. Stock is fine enough.. 12.1 cant get much higher than that.. 13.1 will not notice much difference... If you run pump gas do it at your own risk.. THAT my friend will be a big waste of money.... It's like buying a drag car with a 502 big block 13.1 and tryin pump gas... WASTE!!! I'm not mad just tellin how it is.. and from 30 years experience... Thats why you turn to the forums right cause YOU dont have the experience.
Posted January 15, 2007 - 01:30 PM
And i agree with using the lowest octane fuel you can, lower octane fuel can actually give you more power as it explodes with more force, however that force and too much compression (low squish band) can cause the piston to detonate and ping causing damage, but i guess this is just opinions, and everyone has one..... I too have been racing snowmobiles for years, i know it's a bit diff the bikes but the fuel issue has come up and I use race gas for my ultra high compression 440 racer and i mix it 50/50 with 87 octane for my other 800 racer, not as high compression, and i have no problems, just keep the detonation away.........
Posted January 15, 2007 - 02:39 PM
Posted January 15, 2007 - 03:56 PM
Posted January 15, 2007 - 04:18 PM
Posted January 15, 2007 - 06:34 PM
what i was implying was that you should run the lowest octane you can get away with for each application WITHOUT DETONATING!!so running 112 vp would be cool in a 8.5 to 1 cruiser,i dont think so,it will accually run like crap.thats all
Dude this thread was about!! HIGH COMPRESSION!!! Not a cruiser... 13.1 not 8.1 And as for the ride to work no you dont use race fuel... YOUR NOT RACIN!!! If your just playin dont pimp out the motor.. It's not cool to pimp yer motor just to drive to work or play once a month!!!
Posted January 15, 2007 - 06:36 PM