Aftermarket Heads vs Stock

[RUDY]

Heard that the Polaris has a weak compression ratio 9.4:1..Talked to a few people and some said go 13.1:1 or 12.5:1...My concern is the sled is new and under warranty and going with a higher compression head when would I have to do a rebuild..If anyone can tell me what kinda mileage I could expect out of a 9.4 compared to a 12.5,Thanks

 

[magnet]

Heard that the Polaris has a weak compression ratio 9.4:1..Talked to a few people and some said go 13.1:1 or 12.5:1...My concern is the sled is new and under warranty and going with a higher compression head when would I have to do a rebuild..If anyone can tell me what kinda mileage I could expect out of a 9.4 compared to a 12.5,Thanks

there is no such thing as mileage when your talkin sleds lol
if you have questions about polaris mods contact Chris at parkland motorsports in Stony Plain. 780-963-0080

 

[neilsleder]

Put the stock head back on before you take it in for work. It not hard to switch a head out.

 

[Rob1334]

What was your source for 9.4??? When I talked to a couple people they claim stock cut rate is around 12.3. Who's head have you been looking at? I have talked a LOT with Fastrax and Power Addiction about some of their stuff.

I would think you could look at the same mileage as if you used a stock head as long as you run a safe amount of compression for you elevation and also fuel to match it.

 

[RUDY]

What was your source for 9.4??? When I talked to a couple people they claim stock cut rate is around 12.3. Who's head have you been looking at? I have talked a LOT with Fastrax and Power Addiction about some of their stuff.

I would think you could look at the same mileage as if you used a stock head as long as you run a safe amount of compression for you elevation and also fuel to match it.

I did a google search and that is what I found,not saying there right it's just the number they said...If it is 12.3 I would be happy with that.

I also talked to Chris about this he said a 13.1:1 would work for down here and the mtns..Only thing he said is I would have to move the ethanol plug from one spot to another depending on location...

 

[polarisdragon800]

Will have to get a programmer

 

[Rob1334]

With who's head? Power Addictions you do not.

 

[Modman]

What was your source for 9.4??? When I talked to a couple people they claim stock cut rate is around 12.3. Who's head have you been looking at? I have talked a LOT with Fastrax and Power Addiction about some of their stuff.

I would think you could look at the same mileage as if you used a stock head as long as you run a safe amount of compression for you elevation and also fuel to match it.

12.4 corrected CR? That seems high for a stock sled, would need to see the PSI, that's around 165-170 PSI I think. There is a difference in corrected CR and uncorrected CR, 12.4 is probably the uncorrected, and usually manufacturers deal with corrected values (typically what is listed in the services manuals I think). Commonly 2 strokes have a corrected value because of the effective stoke of the piston once it is above the top of the exhaust port, corrected CR is listed as the effective stroke from Exhaust Close to TDC, so the corrected CR is always lower because the stroke length calculation is less.

My point being that you could both be right, corrected CR could be 9.4 and uncorrected could be 12.3. If you have the bore and stroke length stock, and the combustion chamber cc volume I can calc it for you. For corrected you will need the exhaust close to TDC measurement from the top of the exhaust port.

Hope that helps.

 

[j.c.higgins]

If you're running an aftermarket can and a head you don't need a controller.

 

[deaner]

Pretty sure lightening1000 has exactly what youre looking for in the swapmeet. I think he bought a power addiction head for his, but then ended up turboeing it instead.

 

[RUDY]

Pretty sure lightening1000 has exactly what youre looking for in the swapmeet. I think he bought a power addiction head for his, but then ended up turboeing it instead.

i did talk to Lightening1000 about it,i also called Power Addiction and Brad said a 13.5 is what Lightening has is too high for riding in the Edmonton area...He said that the a 13.1 will work for 3-6000ft,so should work fine...Does anyone have a 13.1 and ride it around here and in the mtns?

 

[trench]

I read about this on Snowest, I think that the 12.5 cr head was recommended for riding at our elevation around Edmonton. The 13.1 might be a little much to run on pump gas.

 

[RUDY]

I read about this on Snowest, I think that the 12.5 cr head was recommended for riding at our elevation around Edmonton. The 13.1 might be a little much to run on pump gas.

read 13.1 will work around here but need to run a good premium fuel in the sled...the 12.5 is good for 0-3000ft

 

[j.c.higgins]

Yes the 13.1cr will work here but you'll need to run the non-ethanol type fuels like Shell gold and i'd add a race fuel blend for my own piece of mine. And i maybe change the fuel plug to the Ethanol position. This will change the timing and fuel curve to allow you to run the higher compression safely. But hey if you're uneasy or don't want to do this then go with the 12.5cr and be happy. Besides it's not like your talking 5 or 10hp difference between cr ratios. If you want the best of both worlds then you change heads/domes for the type of riding you're going to do, if this isn't for you go with whats safe and be happy!!

 

[trench]

I thought the 13.1 head was good for 3000 ft and above, if your riding in the Edmonton area your closer to 2200 ft. I imagine you would be fine with good fuel on a nice day, but at -25 with some crappy ethanol fuel????

 

[j.c.higgins]

You're right you'd probably be in the danger zone! So i would blend in some race fuel for added protection. But thats just me! I'm not worried about the extra cost of adding race fuel or avgas.

 

[H2O]

I just ordered the 13.1 head but I ride 4000-6000 ft. If you are running at 2200 ft and want to run pump fuel only then I would get the 12.5 head.