I know that the formula is correct, so if the torque was measured properly[it should have been], I'm not sure I can believe the HP numbers myself.

Those #'s calculate to almost 115HP!!!

I was hoping his motor put out around 100HP. I told him to expect around 85HP, just so he would be happy when he got more. 115HP is more than I figured he would have by a good margine. I can't wait for him to get it back on an accurate dyno to get some real #'s.

At a peak of 86.6 ft/lbs. of torque, I'm guessing my calculations could very well be correct. My calculations were based on the torque at the peak HP levels[72ft/lbs].

 

Scooby,
The torque curve looked real good,just the HP numbers sucked(not accurate anyway)We had the DS strapped down extra tight(so tight I had to re-ajust the chain)I didn't notice any wheel spin or hear any jumps in the rpms.I was doing all the runs in 3rd gear on 20" street tires & stock gearing,also running Trick fuel left over from my last dune trip
Jeff

 

I think the dyno run needs to be repeated (for free).

See http://www.mobiledyno.com/sys-tmpl/m...ryofoperation/ for info on dyno operation and http://www.awe-tuning.com/info/faq/a...dow.cfm?FAQ=22

I thought you need to run in 4th or 5th gear which ever is closer to 1:1?

The best numbers you quoted are for without NOS??? Could there have been a power loss on the dyno with NOS, similar to at the dunes?

 

Scooby,
I couldn't agree you more on getting another free run on the dyno,shoot the guy never faxed me the dyno sheets like he was supposed to!
On what gear to be in I wasn't sure,4th or 5th does make sense though.
What gear is 1 : 1?
The best numbers were without NOS,not sure why? In the dunes I only had a loss of power on the first runs(before I bumped the N20 jets)But I have been slowly bumping up my N20 jets...........I guess I will keep working on it.The NOS is something I dont mind taking my time on, to get it right.

 

I used 4th gear. I don't have the gear ratios off hand. Maybe the clutch had minor slippage with NOS. I run a 9/9 carbon fiber/kevlar clutch with PAMI springs, and engine oil without friction modifiers.

After my initial dyno run, the other runs showed a slight drop in power due to engine heat, but not a 10HP drop.

If the torque and corrected HP figures pan out, I don't understand why the base DS760 kit doesn't get blown away more than it has been reported to. I saw some dune videos and your frontend was not off the ground except at takeoff??? With this power/torque, you shouldn't have any trouble with most banshees. You should be able to run with 520cc banshees. Maybe you are killing your acceleration with too low gearing. Maybe 12 paddle haulers are needed or taller haulers. I run a 17 tooth front sprocket and 22x11x10 10-paddle taller haulers. For me, the gearing is still too low for flat drags. But my setup is different - the turbo needs to be under load to make power.

What is your torque at around 3000RPM? Is it at least 40 ft-lbs? Maybe your setup sacrifices a little bottom end for more topend, which might explain why the base DS760 holds it own at the start of the race?

 

Your last paragraph stated it exactly. Jeffs motor is built for more high end power, and a base level 760 produces it's power in the stock RPM range. When Jeff and I raced, I could take off in second and back off the throtle to keep the front down, knowing that I had the low end power to muscle away. Jeff would have to take off in first to keep the revs up and controll the wheelie.

After the first 50 feet or so, our race was over. From that point on, he simply walked away from me. It didn't matter how well I rode, or how bad he goofed, he could simply motor away.

 

Scooby I think the 10hp drop with nitrous could be correct... maybe?(I think I am still to rich on the NOS set-up)but you do have me wondering when the NOS comes on you get that acceleration surge and the rpms climb rapidly(the rapid climb of rpm's could have been slippage,of clutch or tires)Hmmm.
Although I don’t trust the dyno numbers now, I cant re-schedule for another week or so(the hole shop and crew went to Vegas for some big Kart race)I just cant win this week, already changed the street tires and put the paddles on the 10" rims for the dunes this weekend(but now it's supposed to rain)Also just received some tires(paddles for the wife’s Scrambler)from Rocky Mtn and one of the wheels is leaking air thru the center welds(shoot!!)
Well enough bitching, the videos you seen are probably from Pismo(before I installed the dual carbs)Me and Don's races where pretty even until the dual carbs, now its not even close.
I would love for HP numbers to be 114hp,but until I get it on a dyno again who knows.
Before I do anything with paddles or gearing I am in desperate need of an extended swing arm(take-offs are a joke right now)I think that’s also why the base 760 stays with me on starts.I also think that my power comes on a little higher in the rpms then the base 760 ,meaning I have to rev higher on take offs in turn wheelie problems. So you are probably correct Scooby about me having more top end.
The gearing and tires I run at Sand Mtn are as follows:
15 front/40 rear sprocket and 22x11x10 haulers, and I cant keep the front end down in 1st or 2nd.(I do have a spare 16 , 17 front)
I have raced Banshees(not sure of the cc's) that the owners claimed they dumped 4 to 5k in(just the motor)and I run about even with them(with out NOS)
The peak torque was 86.6 at 3100 rpm(per there dyno?)
Jeff

 

72X4150=298800
298800/5250=56.91428571
57hp is the correct figure for this torque at this rpm

 

QuadMXer, If you read the entire thread you will notice that we suspect the RPM was measured at half of actual. This was due to the program for the dyno being improperly set up. If you use the torque figure listed, and double the RPM, your HP readings are drasticly improved. Either way, I can't wait to get that thing back on a dyno to see exactly how it does, without having to convert anything.

 

Something has been bothering me for a while with Jeffs dyno numbers. I'm not trying to discount the power he is making, but simply trying to understand the numbers.

Correct me if I'm wrong, but I read that torque is "multiplied/divided" by gearing, meaning that if you have a gear ratio of 1.30, the dyno run will show 30% higher torque than if the gear ratio was 1.00.

If this is true, and the DS has a 3rd gear ratio of 1.31 and a 4th gear ratio of 1.05, a dyno run in 3rd gear resulting in 86ft-lbs/114HP equates to a 4th gear dyno run of:

(1 - 0.247) * 86ft-lb = 65ft-lbs

(1 - 0.247) * 114HP = 86HP

I know it would be dissapointing to us all if this is true, but 86HP is still a repectful figure. But I hope that I'm wrong. I was calculating additional power gain that I could achieve by similar motor mods, based on 114HP. I may need to adjust my expectations if all this is true.

Can anyone confirm that this calculation is correct or incorrect?

Jeff, when can we expect a new duno run?

FYI: I've been looking at Jeffs engine mods along with his dyno numbers to see what engine mods would go well with my turbo and give the most power gain per dollar.