johnnyboatman

iTrader: (5)

if the bsfc is supposed to be around .465 and an engine is dynoed at .745 what could be the problem, the air flow ratio is 12.6 is all the extra fuel going to go in the crank case or will it burn it, ive talked to some guys and they say theres a problem and the builder of course says its ok im at three to one odds, 3 who say theres a prob and one who says its ok.i would like to know what you guys think.i do not want to install these just to have to pull them back out cause theres a problem and washed out the bearings.

Unlimited jd

iTrader: (5)

N/a sounds like a pretty inefficient motor. What's the specs?

bobl

Since the A/F is correct, you would tend to believe the fuel is being burned. In my experience A bad BSFC really points to something in the setup of the engine, cam timing, ign timing, severely mismatched components, etc. something way off in the engine build. It also could be a calibration issue with the dyno or fuel flow meter. Fuel burned is usually a very good indicator of the power the engine is really making. If the dyno was reading low it would make the BSFC incorrect. What was your observed HP reading on the dyno and what correction factor? BSFC is based on raw power, not corrected.

Bob Lloyd
Full Throttle Marine

johnnyboatman

iTrader: (5)

the engines are talldeck 540s, brodix heads, 10.2.1 compresson, hyd roller 611,631 lift, 1050 dominator, the builder said i should quit worrying about it and install it in the boat. the engine was supposed to make 700hp but only made 620hp, had lots of carb problems at first couldnt get the engine to pull any fuel had to choke the 1150s down. im not going to lie, i can do almost anything to the boat myself but when it comes down to this im LOST!!

GPM

I'm not a carb guy, but that sounds like a lot of carb for a 620 hp motor.

articfriends

iTrader: (1)

Scan your dyno sheets and let us see your actual fuel used numbers/un-corrected hp. IF base hp ISN'T shown we can calculate observed hp from your fuel numbers. Yoou don't tune motor for BSFC, you tune it for egt/afr/knock/plug color/egt's and hp/tq. BSFC's in the mid 7's tells me either the data is all screwed up/un-reliable or your motors are terribly in-effiecient, post your dyno shets, Smitty

bobl

What do you mean by "choke the 1150s down"?

johnnyboatman

iTrader: (5)

was told they converted them to 1050s

bobl

I don't see the BSFC or correction factor on the dyno sheet. However, it appears to be burning around 290 lbs/hr of fuel at peak HP. If you divide that by the .745 BSFC you mention it comes out to around 390 uncorrected HP(not very likely). But, if you use .48 BSFC which is in the area it should be it comes out to 600 uncorrected HP. I'm thinking they just have the formula messed up for the calculation in the dyno program. Fuel consumption looks pretty reasonable. If you don't have the correction or observed data, post the location it was dyno'd at and I can look up weather data and altitude for that date and get a pretty good idea of what it should have been.

Bob Lloyd
Full Throttle Marine

Rookie

iTrader: (4)

Do you have the cam card? At 10.2:1 and with todays heads and cams it is kinda hard not to accidentally make more than 617HP with a 540 (1.14HP/cu.in.) Was this dyno'd with full accessories and wet marine exhaust? That can make a huge difference compared to no accessories and dyno headers.

Am I wrong for thinking this??