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    Here is an example of a viable "Group Buy"


    A promotion that has the words "Group Buy" in the title is still a promotion, and from the rules that were handed down to me by Harris Publications is that non-advertisers cannot run promotions or open sales programs on the forums outside of the swapmeet.

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    Have a great season.

    From this point on, all vendors/mfg's promoting Pre-Season tiered sales programs, in the Polaris Forums, that are not paid advertisers will be appropriately moved to the swapmeet section of the forums.




Well-known member
Lifetime Membership
Apr 18, 2009
Kalispell, MT

Which EFR turbo and trim is being used in the MTNTK kit? (what Map are you showing above?)

Is your system making positive manifold pressure (>14.7PSIa) at engagement?

Does MTNTK have any tables on lb/min demand at consistent manifold pressures for the 800 AXYS engines over the RPM range while pressurized?
It would be nice to see what these engines "need" in terms of mass/flow/pressure.

Also... Have you put a vacuum gauge at the reed vacuum reference point to see what it is reading at idle?
Then see what vacuum is required to begin to lift the CRV... set the spring pressure at just slightly above that
and you, IMO, will have an optimized BOV-circuit for your configuration.

It is nearly impossible to get rid of some flutter when you chop the throttle..but it's good, from a performance perspective, to try to minimize it.

They use a 6258 with.64 AR.

According to my boost gauge, it is still reading vacuum at engagement. Granted I have my engagement a little lower than typically seen in turbo clutching.

No they don't. Getting accurate lbs/min would be pretty difficult without a boat load of instruments. If you want to try to guess: http://www.turbos.bwauto.com/aftermarket/matchbot.aspx

Reference at the reed cage is looking for a delta between compressor pressure and post TB, not necessarily vacuum. I talked to BW and Mtntk, they do not offer a lighter rate spring. Mtntk said that they never had this flutter on the Pro kit, but now that they added the intercooler and the 800HO making more power, they get a bit of flutter at higher boost levels.


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Premium Member
Dec 12, 2005
West Coast
An intercooler, or other volume 'adder' on the charge side, can add a bit of "bounce" in terms of surge from my understanding.

Checking vacuum at idle with a simple needle gauge and using a hand vacuum pump with gauge to see when the CRV starts
to lift is a decent "systematic approach" to getting the ideal setup... FWIW.

That turbosmart DP CRV is an easy adjustment 'tool' for finding that point IMO... a bit pricey at $130 all in, but what isn't these days??

The 62/58 is the smallest EFR available... with the estimated numbers that Tory posted... looks like some efficiency without
limiting the output might be had with a smaller turbo... though the EFR, by virtue of the low spool mass alone still would get my vote over others.

NOTE: Surge, Flutter, and chatter are being used above in this thread interchangeably.
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