Quiet Storm

Why does it take two carbs to make the same amount of hp on roots type blowers than Whipples. In the 700hp range on a hp500. Do the roots type use more fuel?

blown1500

Hello Quiet Storm,
It takes a certain amount of air flow to make any given hp. For 700 hp, one carb on a roots blower is enough air, but most roots blowers big enough to make that much power need two carbs to give better fuel distribution. One carb on a proper blower top will work. Roots blowers are not as efficient as Whipples or Prochargers, therefore they use more fuel and make less power at the same boost.

Quiet Storm

blown1500
The reason for my question is I spoke to an engine builder about what I want from a pair of hp500's. I was thinking Whipples all the way. From the charts it looks fairly easy for them to produce that hp. He suggested the roots because if you use a big enough one, they can turn slower and make less heat. That’s better for the engine. Okay, but the boat that I'm looking at only holds 110 gallons of fuel. With twin 750 or larger Holleys on each motor, I think I would spend as much time refueling as boating. Is there a significant difference in fuel consumption?

Whipple Charged

quietstorm,

No question, the more efficient blower will consume less fuel. But roots usually need two carbs for equal distribution and usually need more fuel to cool the intake air charge. On a 500hp carb with our sc, the stock 800 works just fine, the air volume is not perfect, but it certainly flows enough fuel to make 700hp. A 1050 dominator will make 20+hp more at the same air fuel with the larger CFM flow.

Some engine builders will recommend roots because thats what they know, they've done them time and time again and have good faith in them, there also typically much cheaper, but there is very little question that they are not as efficient as the later generation superchargers such as the screw and centrifugal.

It's not as simple as bigger is better, a 1471 turning so slow to make 700hp would be very inefficient so thats not quite true, every supercharger has an efficiency range. And either way, the roots is still going to create more heat at those boost ranges (4+lbs.).

Thanks,
Dustin

RumRunner

Quiet Storm:

HP is HP The Whipple systems are more efficient than a roots blower, but the B.S.F.C. (Brake Specific Fuel Conusmption) or the amount of fuel used to make that HP will be very comparable. You'll see alot more difference at the gas pump based on how you prop, & drive rather than which style of blower you use. There are pros & cons to each system, and you can very easily make the type of power you want with either system. I've got a 468" BBC with a 250 Blower Shop Blower and a single 1095 King Demon that makes well over 700HP on pump gas.

Doug

Quiet Storm

The engine builder suggested BDS 871's for my application. We didn't get int the size of carbs? I want to upgrade the Bravo 1 drives with the Teague Platinum Series upgrade and change the ratio from 1.50 to 1.36. Maybe the will last awhile at 700HP.

Doug
So far all I see more pros for the Whipples. I have them on my 454's now and after they were dialed in have been fine. What are the pros for the roots type other than they look fantastic.

Dustin
How much height would the 3.3's with intercoolers add to the height of the HP 500's? And are you suggesting the 1050 dominators for this setup?

Thanks
Roger

Whipple Charged

Quietstorm, the 3.3L with intercoolers or without would be approx. 3" taller and I gain that back by running a 10 x 2" stainless flame arrestor from Eddie Marine. If you want to take some measurments, from the valley of the block to the carb mounting flange is approx. 12" SC has a 4500 bolt pattern. If you want the best carb, I would run a King Demon 1095 or 1195. I don't think you'll need the replaceable sleeves. The one thing the compressor loves is air flow, and the BG's flow a lot of air, I mean a bunch! And you know, looks are worth at least 200 horsepower!

Thanks,
Dustin

blown1500

Hi Quiet Storm,
Rum Runner is right. HP is HP and the brake specific fuel is about the same, but-it takes more HP to pull a roots type blower than the much more efficient Whipple. I have seen engines with the same prop shaft power get noticably better fuel ecenomy with Whipples. Why do you think you need a cogged belt system to run almost any boost with roots type blowers? We install roots type blowers all the time but we recommend Whipples. Usually, the choice is made for appearance or because the customer believes what someone else has said about how much power the roots type make. Littlefield and many others make good quality parts and their systems are reliable and beautiful-but, put in a pinch, they usually admit they cannot compete with Whipples or centrifugal hp in a properly matched set up. The ultimate, though the most expensive is TURBOCHARGERS

Quiet Storm

Thank you guys for all the information. I’ve learned a lot from this. I am looking at a specific hull type but the boats I have found have different motor arrangements. Some have blowers (roots type) and others that are good candidates for blowers. The boat that I like the most has HP 500’s. After talking to the engine builder I wasn’t sure what type of blower to go with.

I’ll go with the Whipples with the King Demon carbs., bonus info from Dustin. I’m not up to turbochargers yet.

Thanks
Roger

RumRunner

Roger:

I went with the roots blower for the look, and the price (I couldn't beat the deal) We do alot of work with Whipple stuff, they are great !!! They build tremendous power, and a ton of torque very quickly. If you need a hand getting the carburetors dialed in once you get everything together let me know.

Doug