S
Not sure the market could support, seems more and more are going with boost or staying stock.
975cc 1140cc..... HOW LONG TILL WE SEE SOME VIABLE BB G4'S ??
- Thread starter mountainhorse
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600 mountain miles on TMS927 here in Wyoming, power, torque and over all run ability are amazing in the new chassis, also have a very well running 2016 TMS872 with 2200 miles, these 2 sleds are put side by side every time they are out so the clutching and gearing changes can be varified.
Have been running ZRP 85 gram base weights loaded to 97.4 grams and feel they can handle a gram or two more as it is still a little high on peak RPM, overall another quality package from Dave and the TMS crew.
There have been a few issues in the stock skidoo wiring harness with broken boost injector wires and TPS wires other than that it is a very good mountain motor as it generates very quick ground speed.
Have been running ZRP 85 gram base weights loaded to 97.4 grams and feel they can handle a gram or two more as it is still a little high on peak RPM, overall another quality package from Dave and the TMS crew.
There have been a few issues in the stock skidoo wiring harness with broken boost injector wires and TPS wires other than that it is a very good mountain motor as it generates very quick ground speed.
How are guys coming along with clutching improvements for these? How are the turbos doing?
Love the BB stuff but on the big twins the clutching is not easy..
I wonder if this jackshaft over the engine concept is causing them grief..
RS
Sent fra min S60 via Tapatalk
Love the BB stuff but on the big twins the clutching is not easy..
I wonder if this jackshaft over the engine concept is causing them grief..
RS
Sent fra min S60 via Tapatalk
I probably would have if things had worked out to have them ready at the beginning of the season. But I'm not going to tear down mid season for a handful of good pow days and ride spring snow the rest of the time. Then start over again with a 18 175.
Next season possibly.
T
There Is a builder that has a 985 etec out there out of the 800, but is still in testing. Most likely he got something cooking for the 850 too
No clutching issues with this BB and no issues with belts either, Big Bore has been on this sled from day one, Dave put the first 100 miles on the sled before he brought it to me along with a secondary shaft to convert to a floating secondary so no blown belt on this sled after many wide open pulls in the steep and deep and hard pack.
Stock 850 ETEC (for those who may be wondering)
Bore: 82mm
Stroke: 80.4mm
I understand that there are safe overbore limits with a stock cylinder.
New cylinder monoblock, 13mm overbore, and 95mm pistons... an 1140 would be nice !
Or 6mm overbore/sleeve for a 978?
Bigger bore, tuned more conservatively, no fuel control box, reflashed ECU... may give an amazing 'package'
With a super conservative stock-like tune... we should be able to expect similar HP/cc (.2hp/cc for the stock 850, which BTW is about the standard for all 2S sled twins these days)
927cc ~ 185hp
975cc ~ 195hp
1140cc ~ 228hp
Pushing harder will of course get more power... but will of course have pro's and con's to it.
TMS 927:
Anything larger than the approx 4mm overbore 927?
BTW.... what is the actual piston bore for the 927?
What pipe is used on the 927?
How highly tuned is this 927?
IE: Is it pushed hard like a race motor....
Or does it have a more conservative tune?... geared toward pump fuel at ALL altitudes and longevity/user-friendliness in mind without needing any tuning knowledge to own?
With the same level of tuning as the TMS-927 has (porting, fueling, compression, pipe) what would the stock 82mm bore in the 850 make .... what is the power diff in the two, fully tuned, engines from TMS (850cc vs. 927cc)?
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Bore: 82mm
Stroke: 80.4mm
I understand that there are safe overbore limits with a stock cylinder.
New cylinder monoblock, 13mm overbore, and 95mm pistons... an 1140 would be nice !
Or 6mm overbore/sleeve for a 978?
Bigger bore, tuned more conservatively, no fuel control box, reflashed ECU... may give an amazing 'package'
With a super conservative stock-like tune... we should be able to expect similar HP/cc (.2hp/cc for the stock 850, which BTW is about the standard for all 2S sled twins these days)
927cc ~ 185hp
975cc ~ 195hp
1140cc ~ 228hp
Pushing harder will of course get more power... but will of course have pro's and con's to it.
TMS 927:
Anything larger than the approx 4mm overbore 927?
BTW.... what is the actual piston bore for the 927?
What pipe is used on the 927?
How highly tuned is this 927?
IE: Is it pushed hard like a race motor....
Or does it have a more conservative tune?... geared toward pump fuel at ALL altitudes and longevity/user-friendliness in mind without needing any tuning knowledge to own?
With the same level of tuning as the TMS-927 has (porting, fueling, compression, pipe) what would the stock 82mm bore in the 850 make .... what is the power diff in the two, fully tuned, engines from TMS (850cc vs. 927cc)?
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I think a more user-friendly, elevation flexible BB for the 850 would be a better seller to the masses... something that benefits mostly from the increase in displacement rather than than a 'higher-strung' state of tune.
No doubt that a 290cc addition to the 850, to yield 1140 with 95mm pistons, a 33% increase in displacement, would have a considerable perk in the performance department.... Getting those cylinders with those bore sizes would be a bit of work however.
Not sure if a bore and sleeve could yield the 95mm bore required for th e1140 and still leave enough metal to have sufficient transfer port sizes. utilizing the stock ROTAX-850 ETEC Monoblock cylinder casting.... Or would a billet or custom cast Monoblock be required to pull that off.
Not to discount the more race-inspired kits out there.... those definitely have a place for many performance enthusiasts.
IMAGE: Trygstad MS
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No doubt that a 290cc addition to the 850, to yield 1140 with 95mm pistons, a 33% increase in displacement, would have a considerable perk in the performance department.... Getting those cylinders with those bore sizes would be a bit of work however.
Not sure if a bore and sleeve could yield the 95mm bore required for th e1140 and still leave enough metal to have sufficient transfer port sizes. utilizing the stock ROTAX-850 ETEC Monoblock cylinder casting.... Or would a billet or custom cast Monoblock be required to pull that off.
Not to discount the more race-inspired kits out there.... those definitely have a place for many performance enthusiasts.
IMAGE: Trygstad MS
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Wondering about my previous question:
I'd expect an 8% diff in performance of a TMS-850cc and a TMS-927cc tuned to the same level based on displacement alone. (race gas, and high altitude running)
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