VP race fuel question

[hcr ditch banger]

Ok Modman u sound like the most knowlagable member when it comes to all these av / race ras ?????? stock 2010m8 just a can . i just run the recomended 91octane around home going to Valmount this weekend for the first time should i go with the strait 91 octane there or go with a 15% or 20% race fuel mix help make this easy for me please. i don't mind spending the money if it is worth it . just would like to know the right ratio to blend the two together.

 

[Luke The Drifter]

Ok Modman u sound like the most knowlagable member when it comes to all these av / race ras ?????? stock 2010m8 just a can . i just run the recomended 91octane around home going to Valmount this weekend for the first time should i go with the strait 91 octane there or go with a 15% or 20% race fuel mix help make this easy for me please. i don't mind spending the money if it is worth it . just would like to know the right ratio to blend the two together.

It'd be pointless to run race fuel on a stock M8. I ride the exact sled and I've never had an issue with 91 pump fuel. If memory serves me right the stock compression ratio on a 2010 M8 is around 9:1. Save your money or put it elsewhere on the sled.

 

[Vertical-Extreme]

Well that's cheap for av gas ! I was buying it $1.86/L here last year, going through about $80-$90 worth a day on a big day, and I know its over $2/L here now. Biggest PITA is only having so much of it and driving a mini-tanker truck around. My one riding buddy also runs av so between us we had like 6-7 jerry cans in the truck for a weekend of riding. I opted for more displacement and less compression to make the same power, and I can do it on pump gas too.

2.00 bucks a liter ? Someone had you over a barrel (no pun intended ). Ok maybe a little .... I just bought 200L from spring bank for 1.70 last week. Cost me 356 bucks tax in. The cheapest I have heard for vp this year is 625 a barrel for VP111. I fully agree though, run the least octane you can, don't get caught in the "I'm gonna run race / avgas so I get more power BS

 

[oler1234]

LOL you lost me a couple posts back - I'm assuming you got a new ride something based on an 809 triple from a Mach Z. Who built the motor, what head, what RPM you going to run, what pipes, porting etc. Lots of things can determine what fuel you need, if you have a wild port job then starting will be hard enough at elevation without adding race fuel in the equation so you may want to consider the stock head, but below 3,000 ft shouldn't be too bad for starting but you will need definitely need more octane with the 15:1 CR. There is corrected and uncorrected ratios for compression so you need to determine if you want the corrected or uncorrected ones (there is also a separate one for 4 stokes that accounts for dished or domed pistons - negative or positive values) so make sure you use the right formula. Corrected ratios use the effective piston travel (from port close to TDC - NOT the full stroke!). To determine the uncorrected value for your sled you need the bore, stroke and head volume in CC's. The manual for the stock 809 should list the compression ratio for the stock head, and I believe Doo lists the uncorrected value (probably something like 9:1), but if its like 5:1 then it might be a corrected value.

your talking static and dynamic compression ratios when you are saying corrected(dynamic) and uncorrected(static)

 

[imdoo'n]

wow, that was a mouthful bart, i'm thinkin i'm lost, gary has been mumbling something over in the corner, about formulas and lhf and ex girlfriends. i'm thinkin maybe some of these questions are for the engine builder. or a least mix as much octane as you'll need.


bart would this have been the cause of said big kitty going over backwards in a parking lot a while back?

 

[Modman]

Ok Modman u sound like the most knowlagable member when it comes to all these av / race ras ?????? stock 2010m8 just a can . i just run the recomended 91octane around home going to Valmount this weekend for the first time should i go with the strait 91 octane there or go with a 15% or 20% race fuel mix help make this easy for me please. i don't mind spending the money if it is worth it . just would like to know the right ratio to blend the two together.

sorry bro, i'm just a normal guy like you. I was lucky to work for a guy building motors years ago, and I have worked on a lot of big sleds by chance/fate/ or punishment . I am also lucky to have a close family member that is a fuel distributor, so I learned a lot about fuel over the years...... Luke hit it on the head - No need for anything other than 91 octane in your sled at any elevation. Save your money.

 

[Longhairfreak]

Ive seen people who thought that their sleds needed a 50/50 mix and when they got up top sled ran like crap. He dumped it out topped it up with premium and sled ran fine.

 

[Carrots]

Pretty sure this is a dumb question but how do I find out my compression ratio?


Sent from a iPhone

 

[Modman]

wow, that was a mouthful bart, i'm thinkin i'm lost, gary has been mumbling something over in the corner, about formulas and lhf and ex girlfriends. i'm thinkin maybe some of these questions are for the engine builder. or a least mix as much octane as you'll need.


bart would this have been the cause of said big kitty going over backwards in a parking lot a while back?

LOL what going over backwards? You gotta wheelie to go over and my sleds don't wheelie......that often.

Yes they would be questions for the engine builder but often times its just a motor with a head and some guy bought it off some guy and he bought it off some guy that stuck the head on it and no one really knows whos head it is or where it came from or what the compression ratio is and no one has a phone # for this magical engine builder....blah blah blah.so just trying to help him out. If you have a Black Magic motor you fit into this crowd....built great motors but now the company is extinct. Good luck getting help. Or you'll hear....."My brother bought it and the guy told him to run av gas in it." LOL Even with a name on the head if the domes are custom cuts then no one will really know what the deal is, especially if someone has done some backyard additions to the sled and isn't running the original motor combination. Been down that road a few times over the years......Best thing he can do is call up the manufacturer if it has a name on it and see what they say or you can CC the heads but not much point if he knows the CR. So many times guy just have the heads knocked down off the deck by a local machinist (the old "just take 30 thou off" routine) and don't touch the squish, clearance, angle, etc. Sounds like he knows its 15:1, so that thing has pretty good compression! 18:1 in the hillclimb bikes.......about 200 PSI and the nitrometh. With those pressures you have to strap the motor to keep the head from lifting....15:1 on a bigger displacement triple and you will have trouble pulling it over on a cold day! Probably goes like a raped ape though, those 809's were fast revvers. rubber side down.

 

[Modman]

Pretty sure this is a dumb question but how do I find out my compression ratio?


Sent from a iPhone

You need bore and stroke and your head volume in CC's, then its just a calculation. No such thing as dumb questions.

 

[hcr ditch banger]

Thank for all the tip an answers guys . have fun sledding