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PRC Forced Induction crankshaft mod

I'd like to see an apples to apples stock sled conversion with this mod. Same sled, before and after... no other changes to the sled and see what happens.
 
keep us updated. I spoke with a guy who has been around along time. He said that they tried this years ago back in polaris developement and it actually lost power. He compaired it to taking a fan and putting it in the middle of a big room. It does nothing but circulate the air around. 2 stroke engines work on hi and low pressures. The case fills and there is a higher pressure in the case than the cylinder the ports open and the high pressure goes from the case to the combustion chamber which is the low side till it equals out. He claimed that it doesnt bring anymore air in through the intake into the case so there is still the same volume of air in the case. He also said that if it worked it would have already been in all the sleds sold today.

So all in all keep us updated with the results on the sled.
 
glh your guy is on it!!! The fan in a big room is a very good analogy. Two stroke air pumps, naturally aspirated, depend upon the compression ratios-high & low pressure, for exchanging the fuel/air charge. The "crankcase compression ratio" is a very important part of the overall balance. Notching the crank enlarges the open area in the crankcase to lower the crankcase compression ratio. Picture it as adding 0.020" to your cyl head. What does that do for performance???
I might be missing something here but I have built enough engines and worked with enough engine builders over the years to know that a correct match of compression ratios is crucial to building a strong engine.
When you send your engine to Jack or SLP for engine modding, there's a lot more thought into it than hogging out the ports and cutting the head.
That's why some places make an engine that "works" and others just make noise.
But I'll keep an open mind because I'm always on the look out for more "easy" power. Stay tuned, I know there'll be more on this subject.
 
I know it has been tried in the past,lord knows how many people have told me this but our design is not intended to work as a fan,the angles we cut are meant to collect the air/fuel/oil mix and direct it into the transfer port under pressure,when.
When the veins pass the transfer pocket and enter the case the area become smaller because the case clearance is fairly close so you get a small measure of compression,when it re-enters the pocket the angle of the veins release the charge directly into the transfer port.
That is the theory behind it.
 
we have dirtbike dyno's and are working on sled dyno's, it produces good power gains all across the RPM range.you can find our website address in the last issue of SnowWest magazine,it has the dyno charts on the site.
 
PRC.... It would be great if it works and as I said above... you'll sell a lot of them.

Get a couple into peoples hands (Mountain sledders) that are indepent and are keeping the rest of the sled the same... only changing to your crank mod (no gearing, track, suspeinsion, exhaust, bore fresh pistons etc.....just the PRC mod) and lets hear from them... that will be your BEST advertisment bar none...

A test of your mod will have no value if other items on the sled are changed at the same time as the crank.

I wish you the best of luck with your process... we could all use the power increase that you are talking about and would gladly pay if the benefits were delivered as promised.

PRC's website:http://parrisracingconcepts.com/Home_Page.php
 
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Mountainhorse we do have 2 summit X 800's and 1 07 M8 bone stock other than the mod that ran in the highcountry here in Montana,we are trying to get them to take the time to write testemonials so we can post them on our website,we have recently done cranks for some people from Alaska and are waiting for feedback.
 
Q: Isn't one benefit more "swirl" in the case? Mixing fuel and air better making it combust better and not pooling fuel in the case (droplets)?

RS
 
I know it has been tried in the past,lord knows how many people have told me this but our design is not intended to work as a fan,the angles we cut are meant to collect the air/fuel/oil mix and direct it into the transfer port under pressure,when.
When the veins pass the transfer pocket and enter the case the area become smaller because the case clearance is fairly close so you get a small measure of compression,when it re-enters the pocket the angle of the veins release the charge directly into the transfer port.
That is the theory behind it.

How does this differ from the "Turbo crank"? The obvious geometry changes from holes to slots but the theory still seems very similar. I've always been a bit curious about this type of mod to the crank lobes.

I've got two 809's and one 800 twin crank that need rebuilding currently so I'll keep and eye on this thread.

turbocrank
 
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Get a couple into peoples hands (Mountain sledders) that are indepent and are keeping the rest of the sled the same... only changing to your crank mod (no gearing, track, suspeinsion, exhaust, bore fresh pistons etc.....just the PRC mod) and lets hear from them... that will be your BEST advertisment bar none...

I'd offer up my sled as a test dummy!
 
Q: Isn't one benefit more "swirl" in the case? Mixing fuel and air better making it combust better and not pooling fuel in the case (droplets)?

RS

I do not think it is a swirl but, rather, a toss.. If you think about the F/A mix entering via the reed housing it is usually aimed directly at the crank journal. So, the only difference would be this stream of F/A mix hitting a "cupped" journal vs. a "smooth" one.. I could see this essentially scooping up the charge and directing/throwing it into another area of the crank-case.. Is this beneficial?? Don't know... could be, I guess... I suspect this mod only shows any difference (good or bad) on full circle crank designs..

Are you guys seeing any difference with the semi circle crank designs?

As for any fan effect?? In order for ANY fan to work, the fan has to be rotating at a much faster rate than what it is trying to fan.. correct? Think about it.. if you on a ferris wheel spinning at 200 rpm and you have a fan parallel to you also spinning at 200 rpm.. you will get no fanning effect..

So, since the 2 stroke crank is spinning at the same rate ans everything else internally... it would be very hard to have any type of fanning or forced induction effect simply because the crank is spinning at the same rate as everything else..

But, who's to say it does not work.. sure would be interesting to test it and see.. I think the testing method would be critical.. Ideally, you would want to hit the dyno at 8:00 am dyno the stocker... pull the engine down at 10am, do the mod, CHANGE NOTHING INTERNALLY , re assemble and back on the dyno in th afternoon for the results.. Possible?

Neat topic.. hopefully, it gets tested and posted..

Kelsey
 
Theory:The cuts forcing air away from the rod towards the transfer ports on each side would create a slight vacuum in the middle; thereby enhancing the air capacity of the case.

Real world: Throw in the turbulence of the rod and journals and the fact that the transfer ports are not always open which is going to create a damming effect and corresponding reverse compression wave and its anybody's guess as to the performance gains until it is actually put on a dyno...which is exactly what we all want to see.

Dynanometers dont lie.
 
RKT,we have dyno results for the dirtbike applications on our website and should have the sled results soon, Straightline Performance is going to test it and see what it can do.
 
dood, you put this on a credible dyno ( dyno tech prefferably ,, not SLP's lol )
and it shows half of what you claim you will be up to you eyeballs in orders.
dyno credibility i think is important, if you could baseline a stock known sled with the same dyno to calibrate to ,, test say an 08 M8,, if it shows 180 hp stock ,, we know that dyno is off a bit..
you show us you sled before and after and a control stocker with known values to validate,, again dynotech or similiar trusted and known 3rd party places, that have nothing to gain by showing falsified or inflated numbers one way or another. but if you do use slp's, it will show a directional change still
 
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