[HORSEPOWER]

I have sold a good few Rotrex supercharger kits for the V-rod and generally customers are seeing around 160 + bhp. But I think one of my US customers only found 140 ish bhp. I now have a 1130 nightrod in which mad a poor power (104whp) as std and only makes 148 with the blower, we are making the same 9-10psi boost as usual so what's the deal???

 

[Johnny HotFoot]

the 1130 making 'only' 104HP isn't unheard of, plenty of us have put power robbing pipes on and have had a hard time tuning the EFI to bring the #'s up to stock levels (108-112hp)

what pipe and tuner is on that bike?

.... and I gotta say, a 44HP boost from a bolt on SC is pretty nice!!!

 

[Shaggyhou]

Has this just started to happen? Has Rotrex changed anything lately that may have more parasitic loss then before?

 

[richpf]

This could be explained by some bike and SC anomalies and simple math. The stock 1130 is stated to put out 110 Hp (whereas the stock 1250 is stated to put out 122 HP) (BTW, I could not find these #’s on the HD site). It sounds like the SC is producing a 45% Hp increase (approx.). The results pretty much align with your findings. Since your stating with a low 104 Hp, the net gain is dismal. Not every same model bike produced will generate the same Hp. The same could be true of the SC. But then, you probably already know this and it doesn’t help your frustration any.

 

[Gdub]

This could be explained by some bike and SC anomalies and simple math. The stock 1130 is stated to put out 110 Hp (whereas the stock 1250 is stated to put out 122 HP) (BTW, I could not find these #’s on the HD site). It sounds like the SC is producing a 45% Hp increase (approx.). The results pretty much align with your findings. Since your stating with a low 104 Hp, the net gain is dismal. Not every same model bike produced will generate the same Hp. The same could be true of the SC. But then, you probably already know this and it doesn’t help your frustration any.

Your 1130 and 1250 numbers seem a little off. Not sure how many 1250 are actually putting out 122, stock.

 

[Ernie82]

I thought that HD advertised the 1130 as 120hp and the 1250 as 125hp. Just working of memory.

 

[T-Rod45]

When you guys are talking stock HP, you are referring to BHP and when you are talking supercharged numbers you are using WHP... Am I correct?

 

[VrodPete]

When you guys are talking stock HP, you are referring to BHP and when you are talking supercharged numbers you are using WHP numbers. Am I correct?

Yes that's correct based on the numbers they quoted above. There will also be differences in WHP depending on what tire (180/200/240/250/260/bigger). If I recall, the typical loss between BHP and WHP is about 10% with the 180 tire, a little more for the 240. That'd make a stock 120HP 1130 motor put out 108HP typical. So 104 isn't terribly out of range and certainly within dyno differences.

 

[Ernie82]

I think your your right, thats probably the differance

 

[CPTJAM]

Good question! I plan on doing as much research as possible, very soon! Joe

 

[richpf]

Yes, I think one can lose as much as 15% between BHP and RWP depending upon drive type (shaft, belt or chain) and wheels. I pulled the 110 Hp figure for the 1130 and the 122 HP figure for the 1250 from two unrelated magazine reviews since I was unable to source from the HD site. Wikipedia provides the following:
http://en.wikipedia.org/wiki/Harley-Davidson_VRSC
"Harley-Davidson claims 123 horsepower (92 kW) at the crank for the 2008 VRSCAW model." "The 1130 ...produces 115 horsepower."

Given this, the paltry 104 WHP that started this thread is probably somewhere near the norm.

Since there are variances from same model bike-to-bike, I am curious as to what the acceptable deviation might be from the OEM stated versus production actual.

Anyone?

 

[HORSEPOWER]

it is an 07 Night rod with the big tyre. Its low mileage so could be a bit tight to. %age terms its making the numbers but its the lowest i've had on the rollers.

 

[Boost]

1130 with 240 tire so 104 on a good dyno is not far off. I would think you could get more than 140ish. More boost?

 

[richpf]

it is an 07 Night rod with the big tyre. Its low mileage so could be a bit tight to. %age terms its making the numbers but its the lowest i've had on the rollers.

Yep, you've got a big load back there. You could try swapping the rear wheel and tire with something lighter for a sanity check. The stock Dunlops are very heavy (assume that's what you get in England as well) over other options. I recall a post here where I think the Metzlers are supposed to be much lighter. A 8" DX wheel is much heavier than other stock options as well.

Any small (3-5 BHP) bump before the SC is applied will likely get you real close to your usual numbers. If it's a problem with your client, you might try the SE cams as a cheap solution to find more power.

 

[VrodPete]

it is an 07 Night rod with the big tyre. Its low mileage so could be a bit tight to. %age terms its making the numbers but its the lowest i've had on the rollers.

Makes sense. '07 was the only year that had an 1130 motor with the 240 tire ... '08 and later had 1250s and the SE's had 1250s

 

[Hannibal Jr]

Sounds right to me. Mine just pulled 107 at the wheel. Engine is rated at 120. All stock except for a sert to get a better tune. The rear wheel eats up all the hps. Mine was dyno'd after a screaming eagle 1250 that made 112. :broke:

 

[Louis]

Assuming you mean Nightrod Special that's the 1130CC motor (lose 5BHP) and the 240 tyre (lose some BHP), and has it got the horrible heavy Duncrap on it? That's a few more. Change the tyre? Just an idea..

 

[AOW]

change the tires & wheels and you could shave off close to 100lbs

 

[Ernie82]

change the tires & wheels and you could shave off close to 100lbs

Are you serious? I am really thinking about putting my bike on a diet.

 

[Louis]

Are you serious? I am really thinking about putting my bike on a diet.

Very expensive game, changing the wheels. The cruddy tyres on the other hand...