gas consumption question.

[harbormaster]

OK, I have 2 454s for the z29.

What would be the difference in fuel consumption per hour between twin 454's and twin 350's?

[Klingon]

Scott,
My shop does a fair amount of performance motors mostly Porsche racing types. There is a bit of data on the dyno called BSFC, this stands for Brake Specific Fuel consumption. This is an an index of fuel use. Basically stated most engines use about 1/2 lb of gas per hp per hour. If you have a motor making 300 hp, it will use 150 lbs of fuel per hour. A fuel efficient motor will run about .4 lbs/hp/hr. A high performing non turbo will use .6 lbs/hp/hr. So if you know the hp of your motors you can get an idea of what it will use at full output. If you know the hp of your motor and find that it is somewhat out of the limits you can get more hp by leaning or riching the motor. The other device is to also use a lamba sensor to get the correct mixture. The cheap ones you see for $200 or less are ok but their bandwidth is far too narrow to fine tune the mixture and require too much exhaust temp to read correctly.

Alan

[mattyboy]

Scot,
who cares if you have money in your pocket if all the other boats are passing you!!!!!! wink wink :D
put the 454's in it you won't be sorry!!!!!!
that's alot of boat for twin 350's to push around
I'd go twin 496 ho but I have champagne taste on a beer budget eek! :p plus I can't get my own boat to run, so why the hell are you listening to me :rolleyes: wink

happy 4th Scot

Matty

[smoothie]

Same here,go with big motors for a big boat :D And set up a payment plan for your fuel eek! A buddy of mine has a 32 ft sea ray that we take to the islands for a weekend. After 3 couples split the bill for fuel and docking fees its really a cheap way to go...so let it happen boat captian. :cool:

[Rootsy]

Scot,

gonna depend on the power numbers of each motor and the rpm where you are gonna operate them. Motors are most efficient for fuel consumption at the point of greatest torque. EFI is going to be more efficient than a carburetor and there are a whole host of other factors.. but in GENERAL a good rule of thumb, knowing some power numbers you can use the link below...

http://www.westechperformance.com/pages/Tech_Library/How-To/fuelflow.html

[MOP]

Like wise thinking on it depends on the whats done to the motors. Speaking of stock 454 350hp vs 350 260hp, there is about 7-8 gallons an hour difference. Same general sized boat say 36 footer with 350s roughly burn 17-21 same setup 454s 23-27. in a standard cruiser speed is maybe 2-3 knots difference. I love small blocks but think a 29 should have big blocks and I would think would be reasonably cheap to run axcept when the hammer is down. Down the road it will be worth more with the big blocks. Besides how do you factor in a BB **** eating grin.

[fasttrucker]

Bigger engines will running 'at the same speed' as smaller motors well...you might find you get better fuel milage.This is true with big trucks my 460hp cummins is the best example much better then older smaller engines that had to work harder.I was getting 7+1/2 mpg.vrs 5 mpg on my first truck which had an older 300hp motor.

[MOP]

Fasttrucker has a good point, I have a client that repowerd a 40 Silverton sedan, he pulled the 454 350's and put a pair of 502 Pleasure Crafts not sure of HP. But he said he went from upper 20's per gallon to low 20's per gallon with a 2 knot increase at same RPM. He did re-prop do not have specs.