Actual Methanol Consumption??

Why is it that when you do the math to calculate methanol consumption per HP per minute that it looks like most oversize there pumps a lot.

Example....at 2300hp and using 1 lb per HP hour = consumption is 5.82 gals per minute. So a Enderle 110 pump which is rated in the 12-13 gallon range seems way overkill.

Is it the pressure pursuit that requires the over sized pump? Or to cover up unknowns or?

Those that have fuel flow meters, do you see closer to the math calculation for your particular power range or is there something else going on?

Building a new fuel system for a fuel change is why I'm digging into this.

Blessings............................Ron Clevenger

 

Hey Ron, one way to deal with this is to think in terms of the air mass flow rate through the motor, the target Air/Fuel ratio, and the fuel mass flow rate which then results. This eliminates all of the guesswork of picking a bsfc figure and then wondering how much power did the boost device rob from the crank or how much of the boost is due to inefficiencies. This method works for all fuels and all boost devices. It is very easy to accomplish with a simple spreadsheet.

Calculate or estimate the pounds per minute of air going through your motor. You will need to know the specs of your motor and some basic specs for the boost device. This is your mass flow rate of air through the motor, usually calculated in pounds per minute. Let's work with meth for this examle. Pick a really horrible Air/Fuel ratio, say 3:1 for a boosted solid meth motor. Divide your air mass flow rate by 3, and then you have your required fuel mass flow rate. Divide your fuel mass flow rate by the density of a gallon of meth (say 6.63 pounds per US gallon) and you then have the required meth fuel flow rate in gallons per minute for any engine RPM that you care to calculate.

Make sure that your pump will deliver a bit more than this amount at all times, and you are good to go. If you later decide to change fuels, just change your target air fuel ratio. Sounds hard, but it can get you real close real fast once you get the hang of it. The first couple of times are the hardest, and after that it's all repetition, that's why the spreadsheet approach works so nice. Once you have a spreadsheet you can begin to add little "what-if" adjustments as you start to think through different scenarios.

Another really rough hand held calculator method is this. Take your crank HP and then add back what you think the boost device is robbing from your crank. Take the total HP number and divide by 100 and then multiply by 9.4. This will give you a "rough" approximation of the air mass flow rate through your motor because it usually takes about 9.4 pounds per minute of air to make about 100 Hp (gas or alcohol - does not apply to nitro). Take your air mass flow rate and divide it by your target Air/Fuel ratio, and you will get yor desired fuel mass flow rate in pounds per minute. Divide this number by the density of a gallon of your fuel, and you now have your desired fuel flow rate in gallons per minute. Not the most elegant approach, but it gets you very close too.

 

Ron - your 1 lb per HP hr rule of thumb is a good one for naturally aspirated methanol engines.

But as Mike correctly points out . . . more methanol is needed as the manifold boost goes up (really cylinder pressure). NHRA T/AD engines are running almost twice as rich as stoichiometric air-fuel ratio chemisty would predict, closer to 2 lb per HP hr.

I think the extra methanol is needed to evaporate and cool the mixture as the piston continues the compression process after the intake valve closes several degrees after BDC, to keep the cylinder from detonating and/or other catastrophic damage. Just my 2cents . . . other ideas ?????

Patrick Hale
www.DragRacingPro.com

 

Thanks guys, that helped a bunch and see now were I had some holes in my numbers.

The math didn't seem to add up but the trees were in the way to see through it .

Now I have several approaches to circle the wagons before testing how close I am to right.

Blessings....abundantly............Ron Clevenger

 

Well, I'm not changing the blower (ProCharger F3-139) only fuels. Previously ran gas (VP...C-16) at 40 psi boost. So I pretty much know what the blower curve is and on my 565 BBC with 18 degree Big Chiefs and at the blower speed overdrive it makes 40 psi at 8200-8300 rpm.

I really appreciate the sharing of info. I love the engineering aspect of new challenges. Pretty much run the route with gas.

Blessings.........Ron Clevenger
Creekside Racing Ministery John 14:6

 

Mike, gas previously,.....now "switching" to alcohol. Thought I made that clear but maybe not.

The ProCharger is very much like a screw blower in boost curve and needs.

Anyway you guys have straightened me out. My old #1 pump flowed 5.82 GPM (gas) and will be way short of what I'm gonna need on alcohol.

Thanks...........Ron

 

MFI injection ?........

 

You had to ask, actually I have sponsorship with one of the leading blow thru carb companies. So the carb is being converted to blow thru alcohol. But we can't get enough alcohol fuel through the carb's 4 .150 needle and seats to probably get above the 1800hp area. So I've designed a mfi supplement to add fuel above a preset rpm. Using spud's fuel enrichment soleniod operated enrichment valve to feed port nozzles. I'll use an rpm switch to bring the extra fuel into the overall fuel system. Spud's enrichment valve (pretty neat if you have not seen it) has a metering jet to tune with and the hardest part is to know were to size the port nozzles to start with. I'm thinking of starting with some .024's for a start point to supplement.

I know just switching to all MFI would simplify it and we do run a complete conventional blown injected alcohol deal on my son's car. But the sponsor has been good to me and it could work out good for him too to make it work. And the worst part is, I'm an old school tinkerer.

Blessings..........Ron Clevenger

 

Sounds like fun. Yeah I kind of recalled that your's was blow thru from awhile back. I just wanted to make sure you hadn't moved on to EFI cuz if you had I would then have recommended that you do your pump sizing exercise and then add another 30% capacity if planning to use back pressure controlled pumping loops. Can you ramp in Spud's valve with say PWM, or is it an open/shut deal? Have a Blessed Christmas Holiday!

 

It's a open shut deal. Of course the MFI will follow the pumps pressure curve. And when it comes in it will more than likely have a small fat spot. But since I only race outlaw index it won't be critical like class racing is. I try and keep "fun" in my racing program. We are a 3 generation racing family now.

Blessings........Ron

 

We are talking blowers here, do the numbers and math apply to turbo motors or should those ball park numbers change?? JW

 

The two methods that I mentioned apply to all forms of mechanical boost including turbos, since they are both based off the mass of air actually going through the motor and the fuel of choice. Since turbos are so non linear, you really need to use one of these approaches. Think of the engine as a volume device (linear), and the turbo as a variable air density amplifier (non linear). Much different than a positive displacement roots or screw. The choice of MFI or EFI will also make a big difference. EFI done right has a vastly better bsfc outcome and can mean less fuel needed.

 

Interesting thread.....

How do I calculate the flow I am losing in the pump sizer?

It's a lil Bertha with a 900 gear set and a .040 jet in the pump sizer.

Thanks
ML

 

Mike,

I'll have to check my records.... hopefully today or tomorrow.

Thanks!
Mike L.