What is optimal rpm for m8 with twins?

[Alberta Sledder]

I have an 08 m8 with jaws twins,bd, and digitron. Pulls like a train around 7800 to 8100 at home (2500 ft) with 68.5 gram weights. What would you guys try for around 6000-8000 ft for weights? Is there a rule of thumb?

Thanks

 

[m8magicandmystery]

you will probably need 63/64 gram weights...no rule...just guessing...how is the fit on those jaws...any issues..?...heat etc

 

[Alberta Sledder]

Thanks... The twins fit great after one slight mod at install. One pipe did not like one power valve. I made a small ding in bottom of the one pipe with a ball peen hammer, re-painted and works great. No heat issues what so ever.

 

[m8magicandmystery]

Thanx...i have stm valves so i should be ok...what does your chart that is under your hood suggest for weight at the altitude you want to ride...??..i would think that because the twins you would want to run two or three hundred rpm higher then the single that you would be two grams lighter then the suggested,,??

 

[Alberta Sledder]

I think it was 70g or 68g for above 9000ft???? Wife won't let me store sled in town. I will check to see if ac has something less than 68g to grind on monday. I have an extra set of 75, but that may be too much to grind. Maybe I'll try for the fun of it.
Thks for the help.

 

[m8magicandmystery]

pick up a set of dalton adjustables 65 to 75 gram set..you won;t regret it

 

[Rowdy1132]

I have a set of speedwerks pipes, melted the hood alittle, had to move oil inj bottle. I'm only getting 78-8100 also, at 7000-8000ft. So have the same questions. Running 68 grams. My check engine light came on and flashed twice, but goes off if i shut in off and restart. Not sure what's going on. I also am trying a 36-40 helix. Really loads the motor up on lower end. Probly didn't help much but i'm in same dilema....thanks

 

[m8magicandmystery]

I have a set of speedwerks pipes, melted the hood alittle, had to move oil inj bottle. I'm only getting 78-8100 also, at 7000-8000ft. So have the same questions. Running 68 grams. My check engine light came on and flashed twice, but goes off if i shut in off and restart. Not sure what's going on. I also am trying a 36-40 helix. Really loads the motor up on lower end. Probly didn't help much but i'm in same dilema....thanks

speedwerx twins..???...what sled you running..??

 

[Rowdy1132]

It's a 07 M8 with factory ECU and porting

 

[m8magicandmystery]

ok...help me out here...speedwerx web site only shows rocket twins for 700..unless im blind..??...can someone enlighten me or post a link to speedwerx 800 twins..??...and how is the fit and workmanship on the speed werx..??

 

[Rowdy1132]

I bought the kit from Proven on snowest. Not real sure. It really runs. I've seen a few for sale in swapmeet. They fit good, melted hood a little but not bad. your suppose to oil delete, i just moved oil bottle by the brake. You send your ecu to cat and they reprogram it. Runs real nice with no box to mess with.

 

[Bearcat]

Alberta Sledder:
Just wondering... how you are running so light weights?

Pal just put Jaws twins to his CF 8 SP -07 (with CE 156" track) and he's running 75gr at 0-3000ft. We haven't played with the clutching or gearing (still 60/60, will be lower) yet but it did spin good with those weights.

So have you tried more weight or is pal's setup so lost here

 

[Alberta Sledder]

In response to light weight question:

I forgot to add that we swaped the stock helix for a dalton helix recommended by local speed shop. Wicked step up...excellent up and back shift. I have tried heavier weights (73g) at 6-8000 ft and with this helix they resulted in low rpms (7500). If you are running a stock seconday helix that could be the difference??

I never tried my 08 m8 with the stock helix as it came off my 07 m8 before I sold it. I am new to clutching, but I would assume that a different ramp angle would change the weights.
Cheers

 

[Alberta Sledder]

Hey guys,

Correction:

I tried the 73g weights at home not 6-8000 ft.

Cheers

 

[RACINSTATION]

The Speedwerx twins are not for sale to the public. They are a custom pipe built for the hillclimb race team. There are a bunch of them running around and the flat out rip when set up right.

 

[bushy]

I think 7900 to 8000 is the money spot. I've run 8200 with no appreciable benefits.

With Jaws twins.

 

[Bearcat]

We tested the sled in deeper snow just couple days ago. Seems it may need lighter weights. Well it needs new gearbox first as it exploded. Need to get smaller gears and retest how sled reacts.

Otherwise - jaws twins rocks. They really woked the sled