hp per cubic inch

[carreraboat]

on a bbc with a roots blower on pump gas what would you say the hp per cubic inch is?

[DMOORE]

I'd say for a reliable lake boat, set up to do hundreds of hours, 1.5-1.6hp/ci is pretty reasonable. That is also on 91octane fuel.
Just an opinion.
Darrell.

[DMOORE]

you have to add in the "available cubic dollars" factor to correctly finish the equasion:D:D
Dude, ain't that the truth.
Darrell.

[BOOGEYMAN]

1.5 on pump gas(91) is not a problem.

[carreraboat]

so on a typlical naturaly asperated it is 1.25 to 1.30 you only gain a quater on blown set up?i sure thought it would be more

[Unchained]

Unfortunately for all of us the HP / ci is never going to be real impressive as compared to a modern DOHC 4 valve engine with variable cam timing because there are several factors that just can't be over come.
The large cylinder volume is going to be hard to fill efficiently with only a 2 valve cylinder head.
The valve train weight is so high to close those large valves that large springs are required which take hp to operate.
The fact that none of us have overhead cams is all the more valve train weight to have to ovecome.
And for our big V8s to get any kind of impressive hp/ci #'s requires a healthy cam and ports to get there too which compromises drivability.
Many foreign passenger car engines are well over 1 hp/ ci right off the line and run on pump gas for hundreds of 1000's of miles.
I remember back in the late 1960's, a 350 hp 350 chevy was regarded as quite a beast and wouldn't run on todays pump gas.
A 450hp 454 chevy was the highest hp single 4v engine chevy made and was 11:1 compression with a solid lifter cam.
Now when you force feed the engine with a turbo (or one of those old school mechanically driven heat generating devices) you overcome a lot of the cylinder filling inefficiencies. The Turbo becomes the great equalizer.
I had an Audi TT with a 225 hp out of 1800cc (104 CI) on pump gas. 2.16hp / ci. turboed and intercooled.

[BOOGEYMAN]

so on a typlical naturaly asperated it is 1.25 to 1.30 you only gain a quater on blown set up?i sure thought it would be more
1.5 is not bad for a low boost pump gas set up.

[HeavyHitter]

Something to be said about a cross flow head with turbo. The little 528 makes 2.13 on 91 octane. 4 digit torque from 4000 rpm on up is hard to beat even spinning a few rotors.

[Infomaniac]

2 per CID is real easy with a Whippled intercooled deal.
A properly engineered engine will make 1.2 easily normally aspirated on pump gas operating at stern drive RPM's
The same properly engineered engine will do nearly 2.0 with an intercooled roots blown pump gas setup
I have found it to be about 1.4 per with a budget built roots blown deal running a reallly small blower working really hard.
There are alyways exceptions. Where it is dyno tested (duh) how many RPM's the engine is runniing etc.

[BradZ]

I have a pair of engines in Wildcat MTI that were featured in the latest Powerboat Magazine regarding the engine builder "Ateco". They are 598ci that are 2hp per cubic inch on 93 octane. Ran them two seasons. 16:71 blower running 8.5 lbs boost intercooled is conservative on this setup.

[carreraboat]

what about running a little oversized blower to keep the overdrive to minimum so you can keep your intake charge temps low?

[BOOGEYMAN]

Remember that it takes more HP to turn that oversized blower as well.

[carreraboat]

does anyone have any numbers on what series of supers taken to turn?