975cc 1140cc..... HOW LONG TILL WE SEE SOME VIABLE BB G4'S ??

mountainhorse · Oct 6, 2016

With the same 80mm stroke... as the G4-850's you could easily pull 975cc's out of a Polaris 900 (866cc stock)....

Soooooo.

I'm wondering how long before we'll see some custom cylinders and true BB's for these sleds?

Who will be stepping up and making something like this, a 975-1140 Etec, a reality?

I know that the 975's and 1140 Polaris BB Twins based on the 80mm stroke 866cc 900RMK engines were MONSTERS... with only first-gen CFi tech from 12+ year old tech...

With all the ROTAX evolution and tech advances in the G4-850's... a more civilzed brute force engine would be possible I would think

Has anyone "broken into" the Fitch/Etech ECU's yet (bullydog etc)?

Will more fuel through the aux injectors be good enough?

Pistons... what is available in cast or a hyper-forged alloy (4032)?

Pipes... that may be a challenge....cant see optimal numbers coming out of something that has 15% more displacement using a stock 850 pipe???:juggle:

Will the voice-coil injectors handle the fuel requirements?

What % of Capacity are the injectors currently running at full load?

The secondary injectors capacity?

Fuel Pump Capacity?

Is the Vibe-reducing tech compatible with different harmonics introduced with different rotating harmonics?

Would there be enough customer base to support this?

Would be great to hear thoughts on this... good rumors... viability etc...

MH NOTE: I've merged the two BB threads I started to keep in one place

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sledhead_24_7 · Oct 6, 2016

Unfortunately that 900 RMK came out of a John Deere tractor. It was way to over built with no thought out into vibration!

I guess if there is we'll find out toward the end of the season. Would be pretty cool though.

TreeThrasher · Oct 6, 2016

I'm riding a 950 etec 174 off the 800 etec this year. Will be riding a 1000 next year off the 850.

It can be done. The 950 is a hotrod. Stomps any stock cylinder big bore badly...and we have some fast 860/870 combos.

madmax · Oct 6, 2016

What's trygstad making? 930ish something. No dyno numbers yet. I talked to bullydog and haydays, no current plans to do anything other than what they have now with Polaris.

NWaxys · Oct 6, 2016

Big bore

Company I talked with said they see from 910-940 being the magic numbers cc wise yes you can always go more but this is what most builders doing. Tryg is a 927 in waiting to hear about speed shop Inc...

mountainhorse · Oct 7, 2016

Balance

sledhead_24_7 said:
Unfortunately that 900 RMK came out of a John Deere tractor. It was way to over built with no thought out into vibration!

I guess if there is we'll find out toward the end of the season. Would be pretty cool though.

ROTAX, I'm sure, found a better solution to vibration than Polaris ever did on the 866cc "900". Those Austrians know how to make things!
The 80mm stroke sure did make a big diff How it made power though

It's funny though, with the Polaris 80mm engines... the 975 (or even the 1140's) were much smoother than the stock motor... dynamic balance was affected by piston weight.... with the heavy additional bob weights that are bolted onto the Doo 850 multi piece crank... It is plain to see that Doo is paying attention to vibration management with the new engine.

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sledhead_24_7 · Oct 7, 2016

TreeThrasher said:
I'm riding a 950 etec 174 off the 800 etec this year. Will be riding a 1000 next year off the 850.

It can be done. The 950 is a hotrod. Stomps any stock cylinder big bore badly...and we have some fast 860/870 combos.

Who's building those cylinders/kits and such for you, if you don't mind?

damx · Oct 7, 2016

I know brent linderman ( arcticedge ) does a 950cc from the 800 cc. I'm sure he will be doing something with the new 850.

TreeThrasher · Oct 7, 2016

Start with crankshop stuff and go to work.

It is not a bolt on and have it work setup LOL

There are enough issues doing it this way that we will fire up the CNC and build billet stuff for the 850 builds.

fredw · Oct 7, 2016

Maybe leave it stock and throw on a three hr install, four grand turbo and make much more hp than any BB will do for that motor..

Turbos and elevation really like one another

christopher · Oct 7, 2016

So many things to look forward to with these new engines.

kiliki · Oct 7, 2016

christopher said:
So many things to look forward to with these new engines.

ya most first year engines the many things are called "recalls"

TreeThrasher · Oct 8, 2016

fredw said:
Maybe leave it stock and throw on a three hr install, four grand turbo and make much more hp than any BB will do for that motor..

Turbos and elevation really like one another

We turbo them as well...

Ill take a nasty big bore that works for the ground I ride 9 days out of 10. For that other 1 day a race gas turbo reigns supreme.

However if you would ever like to go for a rip in Revy or surrounding area with your 4 grand turbo setup and my 950 I think we should do that...

rulonjj · Oct 8, 2016

kiliki said:
ya most first year engines the many things are called "recalls"

Yes.......we ride Polaris. We know what recalls are. :face-icon-small-win

BIG JOHN · Oct 29, 2016

SHR is starting with a 180+ hp 850 kit (porting, can, timing) then the MPI turbo at 200 hp from 1000' to 9000' (200-190 from 10,000 up) on pump gas...

BB is is third and will be a spring/summer project and the bore size will be determined on meat in the new cylinder, dont want to go "too big" so they are "unstable, "too thin", "fail prematurely"....thinking a 920 is safe and anything bigger could be a bad choice with the stock cylinder:face-icon-small-win:face-icon-small-ton:face-icon-small-coo

mountainhorse · Oct 29, 2016

What kind of skirt and unsupported-wall thickness are you finding?

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TreeThrasher · Oct 30, 2016

Cut aways i looked at showed extremely similar thickness between 800 etec and 850 etec engines.

Just got off the hill with our 850...Thing is a dang rocket for a stock sled, bottom line. Stupid fast compared to anything else ever produced by Doo out of the box, I can't wait to get to work on these things!!!!

mountainhorse · Apr 5, 2017

With the big 80mm stroke of the ETEC-850.... I'm wondering how long before we'll see some custom cylinders and true BB's for these sleds?

Will the voice-coil injectors handle the fuel requirements?
What % of Capacity are the injectors currently running at full load?
The secondary injectors capacity?
Fuel Pump Capacity?
Is the Vibe-reducing tech compatible with different harmonics?
Would there be enough customer base to support this?

Would be great to hear thoughts on this... good rumors... viability etc...

I know that the 975's and 1140 Polaris BB Twins based on the 80mm stroke 866cc 900RMK engines were MONSTERS... with only first-gen CFi tech from 12+ year old tech...

With all the ROTAX evolution and tech advances in the G4-850's... a more civilzed brute force engine would be possible I would think

.

sledhead_24_7 · Apr 5, 2017

Could be

Trygstad's 927 is supposed to run really well, but that is just from talking with him at the Jackson hole hill climb.

sledsrock · Apr 5, 2017

sledhead_24_7 said:
Could be

Trygstad's 927 is supposed to run really well, but that is just from talking with him at the Jackson hole hill climb.

I figured you had one stuffed in yours already?

975cc 1140cc..... HOW LONG TILL WE SEE SOME VIABLE BB G4'S ??

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