Turbo Compression Calculator

[spray25]

That is all with stock gasket and pistons. Still conservative though.

 

[Boondawgin]

Altitude and octane

I think the octane requirement still holds true at altitude, because even though you are compressing air, that air doesn't contain as much oxygen as it would at sea level.

 

[trailblazer98]

I don't know anything about the RX but when do the valves close to start the compression? Compression doesn't start until the valves close. If your valves close after the piston starts up on the compression stroke it would reduce your compression. Yamaha's 11-1 volumetric compression could actually be a 10-1 compression. I don't know much about the sled but this just a theory on why the calculated octane ratings seem high.

 

[spray25]

Good poin TrailBlazer. Does anyone know, or have their engine torn down enough to investigate?

 

[AndersY]

I think we are still missing something. MC says 10 lbs on pump fuel with thicker headgasket.

When I plug the numbers into the calculator though it says that you should be running 95.2 octane.

Even at 10 to 1 with LC pistons it still says 92.5 octane.

Maybe it depends on the pump? :wink: (here in Sweden premium is 98, and regular 95)
RON(Research Octane Number), MON(Motor Octane Number) or PON(Pump Octane Number)? In Europe it is usualy RON and in US it is PON, I think. In Canada I don't know. Short on the subject: www.btinternet.com/~madmole/Reference/RONMONPON.html

 

[BlgsRX-1mtn]

If you click on the turbo calculator link there are calculators for engine size using the 2.91 bore and 2.28 stroke a four cylinder engine is 60.63 CI. Then there is the engine VE calculator which uses size, RPM at peak HP and peak HP. I used 10,200 for RPM and 140 for peak HP. This gave me a VE of 101.71, so go figure that one out. Even if I up the RPM to 12,000 (way above the REV limiter) the VE is 86.45. Drop the HP to 100 RPM @ 10,200 and you get 72.65 for a VE.

 

[Snow Fever]

I have a rear mount MC-xpress, I run between 2200 and 6500' altitude, we only have 91 octane fuel here and I run 9lbs and 11lbs and have had NO issues. On top of that I made a home made device that makes my turbo spike 4lbs extra boost every time you wack the throttle for about 2 seconds. Ran this set up for about a month and half at the end of the season and the only thing that happened was I blew the air box off once. (Never had the intercooler off for so long, the rubbers must have seated and not been as tight as when I installed the turbo?) Keep in mind I do not do death runs down the lake on 11lbs. But do daily 100mph trail runs heading to the riding areas. Hats off to Camoplast for building a 162x16x2.5 that holds up to this abuse.

 

[snowy1]

snow fever: how do you keep the boost down 9 to 11 once I turned mine up to 18 I can,t turn mine back down, I am going to try to turn it down to 14 this year, I will see how long that last.

 

[Snow Fever]

I'm just getting old I guess, good thing I never had this sled in my 20's when I was bullet proof (Or thought I was) These days Fear and comon sense stops me from doing lots of Fun Stuff. :?

 

[Mountaintech]

snowy1, do you have a boost controller or did you just change the length of the control rod? If you just changed the length of the rod I would suggest getting a controller. Do a search for Turbosmart or TurboXS.

 

[snowy1]

yes I have a controller, I know what you mean about getting older I am 42 and I can tell I am not 25 anymore, there is alot of hills I just sit and watch even though I know the sled can do it I know i can,t.

 

[slymax]

That turbosmart boost tee is a piece of junk. The one I had on my sled corroded shut last year and I had to pull it off. 18lbs+ of bosst sure was snaky though.

 

[Snowest]

Where could a person get a fuel tester?

 

[TurboCobra]

those calculations are good for a starting point and knowing what to buy/blend, but I think a knock sensor is going to tell you the bottom line! I can't wait to set one up with a relay to knock down the boost, or send spray into the intercooler! Anyone working on this?

Also, I have already purchased a 6 port electric fuel switch to switch to my rear fuel tank (50% 91 octane & 50% C12) when I switch to higher boost. Still figuring out which boost controller to run.....