BritishV8 Forum

Guys, I need a number for the air requirements to produce 1 Hp of output from one of these engines, preferably in kilograms/min flow rate per horsepower output. Anyone have that info? Thanks.

Jim

JIm, All I've heard is increase of (1) cfm.@28",intake flow, will get you approx.(2) hp. on gas,8 cyls. roverman.

Sure you don't have that backwards Art? Seems like a 300 hp 350 (back in the day) required a 600 or 650 cfm carb...

Jim

I think Art has it right. I recall it being 1 hp per 1 cfm @ 28" for a four banger, or at least very close to it. This is not 100% accurate though, just a measure to estimate, as similar heads with different flow the one with less flow can produce more HP than the one with higher flow. However, that is a science I do not master, but know people who do.

OK maybe I worded that wrong. How much airflow THROUGH THE ENGINE will produce 1 Hp (or 300 or 500 etc.) We all know that a head that has been ported to flow 200 cfm is not going to make 400 hp per cylinder, N/A. That'd be 2400 hp on pump gas without a power adder and that's just ridiculous.

Jim

> How much airflow THROUGH THE ENGINE will produce 1 Hp (or 300 or
> 500 etc.)

100 HP requires 140 CFM based upon a reasonable assumption for Brake Specific
Fuel Consumption (BSFC).  The BFSC assumption keeps us from having to guess
at volumetric efficiency.  A 550 hp engine uses an actual 770 CFM but you need
to convert the pressure drops.  4 barrel carbs are rated at 1.5" but that is
too restricitive for an engine at WOT.  0.7" is more reasonable for a tuned
engine to keep the carb from being overly restrictive.

        Flow @ 0.7 In Hg = (CFM Rating @ 1.5 In Hg)/SQRT(1.5/0.7)
        770 = X / 1.46385
        X = 1127 CFM flow rating required

> Sure you don't have that backwards Art? Seems like a 300 hp 350 (back in
> the day) required a 600 or 650 cfm carb...

A 350 hp engine uses an actual 490 CFM but that doesn't mean a 490 CFM rated
4 barrel carb will provide the required flow.  It takes 717 CFM at 1.5" Hg to
equal that 490 CFM at 0.7" Hg pressure drop:

        Flow @ 0.7 In Hg = (CFM Rating @ 1.5 In Hg)/SQRT(1.5/0.7)
        490 = X / 1.46385
        X = 717 CFM flow rating required

You can make the same power on less rated CFM but the engine would make more
power with more CFM.

Dan Jones

Thanks Dan. So disregarding the carb rating, it'd be safe to say that on average we'd need 140 actual cfm of airflow through the engine to produce 100 hp? That is the information I'm after. I'm working out the math for the amount of heat that needs to be removed by the new intercooler design.

Jim

The most recent info (from Australia) calculated from fuel consumption figures indicates 14.2 Kg of air used to produce 300 hp at a 12.5 afr. Does that seem correct?

Jim, Have you considered E85 ? "Latant heat of evaporization"? Better cooling than gas and approx 15-20% moore power, but 9.85 "stoich". roverman.

I'm chasing you, Art! I just wanted to post to let you know I'm right behind you! LOL

Only if it pings Art. For now I'll stick with pump gas. The Methanol I'm using is the working fluid of the intercooler, not the fuel. It takes half the heat to vaporize that water does but it boils at 148* F and I don't have to worry about it freezing. If I was going to use it for fuel I'd calculate the heat I need to remove, subtract as much as the correct power mixture would handle, and make up the rest with water injection. Then if that didn't remove enough heat add a smaller intercooler or nitrous. But I'm trying real hard here to keep this simple.

Jim

OK at this point the numbers are in and it looks like I need a pump that will flow 2 gallons a minute (120 gph) and tolerate temperatures in the 150-300*F range. Any suggestions?

Jim

How about this one:

http://www.daviescraig.com.au/Electric_Water_Pumps-ELECTRIC_BOOSTER_PUMP_12V_SHORT___PART_No__9002-details.aspx

I guess the suggested operating temp is 50º low but it flows nicely and isn't very big.

I was always under the impression that E85 had lower a HHV than gasoline and therefore less performance. It also returns poorer fuel economy - I put it in the same category as propane and natural gas as far as suitability for driving.
I found this interesting article on a real life comparison between E85 and gasoline under somewhat regulated conditions and the E85 didn't fare very well (even in terms of environmental impact).
http://www.edmunds.com/advice/alternativefuels/articles/120863/article.html
 Based on costs to manufacture, real life performance and availability, I see this alternate fuel having the same fleeting impact as propane and NG.

I'm thinking maybe something like this Summit fuel pump might work well:
http://www.summitracing.com/parts/SUM-G3136/
140 gph/14psi for about 80 bucks.

Jim

OH. yeah. I wasn't thinking about a pressurized pump. That seems like it'd work. Maybe you could find one on craigslist or something.

E85 at face value and treated with the identical approach to gasoline will not perform as well. You can burn it with a gasoline system and it will work but that's the best you can say about it. It can make more power when utilized properly and that means a lot more compression or cylinder pressure.

Yes, When E85 is used in a "built for gas, engine" it provides less economy and probably slightly less performance. Like putting "race gas" in your 9/1 comp. daily put-put, and expecting more? Were one seriously interested in pros and cons, they would "peep" Performance E85 site. With comparative octane of 105 and stoich of 9.85, it's not for everyone. At around $2.50 a gal., it's a good alternative to race gas. We as a people, are fed much misinformation to steer us in a given direction." We shoudln't use E85 because children will starve for lack of corn". In Lancaster, Ca. their building a facility to make E 85 from garbage. Propanol is highest in performance of this group and is being invested-heavy by British Petroleum and Chevron, I believe. Has it ocoured to anyone, E85,"has" to fail ? roverman.

"We shouldn't use E85 because children will starve." -signed Big Oil. I love the one about how it's more efficient to pump stuff out of the ground then into a super tanker and cart it all across the globe to bring it here to be further refined. LOL! What a joke. I think they might be ignoring half of the equation for environmental impact there.

Seriously, I'm no big proponent for E85 but it is a great race fuel alternative. I watched "King Corn", I recommend this documentary BTW. Very interesting. AND the way it's being utilized with Flex Fuel vehicles that are not using some type of forced induction is halfhearted at best. We really need to be producing Ethanol from other sources than corn too. What about sugar beats? What happened to switchgrass? Sorta feels like E85 is going the way of Big Oil with the way it's being handled politically. It's turning, well turned, into a Big Agra football.

There has got to be a bit more honesty on both sides of the alternative fuels debate too. It's like trying to get accurate information by watching the News. WOW that's sad

Sorta like global warming, huh? How'd we get on this anyway? All I do is mention Methanol as a potential refrigerant and all of a sudden it's all about the politics of Ethanol production and use as a fuel. What's that got to do with refrigerants?

Here's the next question, what is the smallest tube that will deliver a 120 gph flow rate at a14 psi head pressure, or shall we say, pressure differential across the line, say the line is 8 inches long.


Jim

Yeah, sorry man. I started doing head pressure calculations but my numbers were based on the density of water. I'm not much help lately.

Dan, Regarding the .7 hg, 4bbl sizing for optimum power. I read the Engine Masters mag. when I can. Case in point, 350" sbc, std. Holley 750 cfm.,447hp at 6,200. Your formula provides max hp. with 916 cfm.? I'm thinking air flow rating system for slide plate injection would roughly equate to inlet port flow, ie. no pressure loss? Thanks, roverman.

Jim, Since there was no takers on the flow vs. tube dia. I thought I'd take a plug at it.

Steep learning curve on the pressure head loss per ft of methanol. I've run a bunch of calculations based on pressure loss for water and tried to sub in the specific mass/density of methanol at 49.38 lb/cu.ft. I get a different number each time of course because I'm just an animator by trade. LOL.

My point is you could get away with going down to .250 ID with some loss in flow because the friction is pretty low at 8" length. loss in head pressure looks like about 12% with the decrease in dia. from .375 ID (3/8 tube).

Hope that helps.

Really? I'm astonished. I found out that a 5' head of water is about 2.2 psi. I'd never have thought that that would be enough to push 1gpm of water through a 1/4" tube. Maybe I should set up a siphon to test it, could be about right.

Jim

I think that would be a good idea. I could have missed something. It was a super lengthy process to try to work through it. More math then I've had to do in a long time. The hardest part was trying to find a reference I could use to calculate something so short (8"). Most of the equations were based on 100 ft of tube.

Could be that the Mass/Density of Methanol is 78% of water. OR I messed up one of the numbers.

I was a bit surprised too because the reduction in head pressure vs. tube dia. seems like it should be exponential because of the reduction in cross-sectional area. I guess it could be that 120 gph at 14 psi isn't based on 3/8"??

I don't know. It's pretty confusing. Just trying to help.

I appreciate it a lot Nik. I did the test, using a 3 ft head since I'll be losing 2 ft going from the bottom of the condenser to the top of the evaporator and using a 5-1/2 ft length of 5/16" fuel hose. It emptied the 1 gallon water jug in right at 55 seconds into the lower jug. So I'd say your numbers are close. Maybe I should see if I can buy some Methanol and try it with that.

Jim