HP losses from Bravo 1X drive
12-30-2006, 12:59 AM
#61
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Re: HP losses from Bravo 1X drive
Strip, those photos are at my shop when we dyno'd Rage's boat.
It is rated to 800 PSHP. The most I've measured is 588 though. You are correct about it loading the drive pretty hard. Basically you open the throttle all the way and the dyno loads it to the predetermined RPM. So, far a few seconds you are at WOT at 4000 RPM and the boat is not moving! The problem is the drive is gear reduced. So if the engine is turning peak torque at say 4500 RPM, then the prop shaft is turning 3000 RPM, but has the torque multiplied by 1.5. A 400 ft. lb. engine would be making 600 ft. lb. at 3000 RPM at the prop. To the dyno it's like measuring a big diesel engine. All the dyno measures is torque. I won't be dynoing any supercharged big blocks at the prop
It is rated to 800 PSHP. The most I've measured is 588 though. You are correct about it loading the drive pretty hard. Basically you open the throttle all the way and the dyno loads it to the predetermined RPM. So, far a few seconds you are at WOT at 4000 RPM and the boat is not moving! The problem is the drive is gear reduced. So if the engine is turning peak torque at say 4500 RPM, then the prop shaft is turning 3000 RPM, but has the torque multiplied by 1.5. A 400 ft. lb. engine would be making 600 ft. lb. at 3000 RPM at the prop. To the dyno it's like measuring a big diesel engine. All the dyno measures is torque. I won't be dynoing any supercharged big blocks at the prop
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12-30-2006, 10:03 AM
#62
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Re: HP losses from Bravo 1X drive
It's all controlled with a lap top. I just set the lap top in the drivers seat, open the throttles until it loads solidly and press record. The computer takes over and makes the sweep based on the input parameters. The only trick is to be ready to pull the throttles back when it hits the max rpm. That's what I'm doing in the picture where you can see my bald head leaning ove the seat.LOL.
12-30-2006, 12:20 PM
#63
Re: HP losses from Bravo 1X drive
It's all controlled with a lap top. I just set the lap top in the drivers seat, open the throttles until it loads solidly and press record. The computer takes over and makes the sweep based on the input parameters. The only trick is to be ready to pull the throttles back when it hits the max rpm. That's what I'm doing in the picture where you can see my bald head leaning ove the seat.LOL.
Does the blue plate touch the cav plate ? or what keeps it from turning?
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12-30-2006, 12:59 PM
#64
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Re: HP losses from Bravo 1X drive
Yes, that is the torque arm. It has pads on it that seat against the cav plate. To use it on the engine stand I have an adapter that slides into the bell housing with a stop on it for that plate. So all I do is slide the absorber onto the prop shaft or the engine stand and set the proper gear ratio for the application.
12-30-2006, 03:48 PM
#65
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Re: HP losses from Bravo 1X drive
Bob,
Eric Betty (EB Marine) has secured dyno services for us here in Nashville at one of the racing oriented machine shops at a reasonable rate, so we will be able to dyno my motor before we install it in the Heat.
I'll let you know how it goes on the Nordic forum.
I think it will make it much easier to prop the boat with this data in hand. Your situation this past summer comes to mind.
I may have been overwinding my old setup........
Regards,
Steve
Eric Betty (EB Marine) has secured dyno services for us here in Nashville at one of the racing oriented machine shops at a reasonable rate, so we will be able to dyno my motor before we install it in the Heat.
I'll let you know how it goes on the Nordic forum.
I think it will make it much easier to prop the boat with this data in hand. Your situation this past summer comes to mind.
I may have been overwinding my old setup........
Regards,
Steve
12-30-2006, 04:09 PM
#66
Re: HP losses from Bravo 1X drive
Yes, that is the torque arm. It has pads on it that seat against the cav plate. To use it on the engine stand I have an adapter that slides into the bell housing with a stop on it for that plate. So all I do is slide the absorber onto the prop shaft or the engine stand and set the proper gear ratio for the application.
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
01-05-2007, 05:36 PM
#67
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Re: HP losses from Bravo 1X drive
Here are some numbers to stir things up. I just dyno'd a Whipple charged 383 on the prop shaft dyno. On the engine dyno it made 555 HP at 5800 RPM. Guess what it made at the prop shaft???? 490 The only difference was that the boat has Gibson mufflers. They aren't supposed to cost any HP, but even if they do that's a 65 HP loss running through a Bravo X drive. Interestingly the percentage loss increased with RPM. At 3600 it shows a 10% loss. More like 12% at 5800. So, on a 300 HP engine a Bravo does cost about 30 HP, but double that and the loss goes up proportionally. I'll be testing some other engine packages this winter so I'll post more results.
01-05-2007, 05:58 PM
#68
Re: HP losses from Bravo 1X drive
Here are some numbers to stir things up. I just dyno'd a Whipple charged 383 on the prop shaft dyno. On the engine dyno it made 555 HP at 5800 RPM. Guess what it made at the prop shaft???? 490 The only difference was that the boat has Gibson mufflers. They aren't supposed to cost any HP, but even if they do that's a 65 HP loss running through a Bravo X drive. Interestingly the percentage loss increased with RPM. At 3600 it shows a 10% loss. More like 12% at 5800. So, on a 300 HP engine a Bravo does cost about 30 HP, but double that and the loss goes up proportionally. I'll be testing some other engine packages this winter so I'll post more results.
Would of been nice to take the muffs off then back up test
Cool info thanks for sharing
Rob
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01-05-2007, 06:32 PM
#69
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Re: HP losses from Bravo 1X drive
Engine dyno was totally rigged and wet exhaust. Didn't have the power steering belt on. I would have liked to test without the mufflers but they are through bolted and sealed with 5200, so they're not coming off. I've tested them before and not seen any power loss, as is the claim from Gibson also.
01-05-2007, 11:53 PM
#70
Re: HP losses from Bravo 1X drive
Engine dyno was totally rigged and wet exhaust. Didn't have the power steering belt on. I would have liked to test without the mufflers but they are through bolted and sealed with 5200, so they're not coming off. I've tested them before and not seen any power loss, as is the claim from Gibson also.
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
