Any MEs in the house??? Help!!!

[lecroy]

I am doing a major change to my fuel system and I am trying to determine the size of lines I need made up. I have used what I think would be a worst case condition to prevent it from running lean. Bike is still going to run on methanol this year and will be turbo charged once again....


Assuming 250 HP

Methanol Specific Gravity is 0.792 @ 60 deg F

I am using a BSFC of 1.35 for a worst case condition. I have read that most of the race cars will run around 1.

So 250 * 1.35 = 337.5 pounds of fuel / hour.

Water weighs 8.345404 pounds / gallon.

337.5 / (8.345404 * 0.792) = 51.062 gallons of fuel / hour.
= 0.014 Gallons / second

Using an orifice coefficient of 0.61 ( for a knife edge)
The new fuel rail will run at 7PSI (I really like the Mallory 4703M regulator)
Using Excel: =POWER(((Flow2*SQRT((SpecGrav2/PressDrp2)))/(29.81*OrCoef2)),0.5)

I get a size of 0.125"
with a 3AN or 3/16 = 0.188" it would seem to be plenty of overkill.

 

[Guest]

Someone here might be able to answer this, but someone on
www.dragbike.com
definately could.

 

[Paul]

I always used to use 1/4" bore for all my fuel-lines. Two reasons, 1 - I would never have fuel starvation, 2 - just one set of fuel-line spares to carry!
Even when I was running a 500cc Triumph twin on methanol, I still used 1/4" bore.

 

[Anonymous]

Pardon a possibly stupid question - Considering the small size of the parts you are discussing, why not simply go with a 1/4" hose and get 4 times the flow area your calcs call for?

That way any line or fitting losses will not be any problem at all and you can sleep at night. Given the consequences of a lean run on methanol, I would be inclined to not even come close to the minimum requirements your calculations call for. Unless the larger fittings for the 1/4" hose pose packaging or cost issues, of course.

Mark

 

[lecroy]

I posted to the dragbike.com group.

Paul,
It's not quite so simple of a problem. I would need to draw the whole thing up for you, but the basic idea is that I ballance the inlet to outlet sizes to get enough back pressure to run the nitrous. The carb has no float, and there is a small scavage pump the drains the bowl and returns the fuel to the tank.
The lines from the tank to the filter, pump, regulator and rail are all 3/8. Way oversized of what the engine can take. The line to the carb is not under pressure like a normal float type carb would be. If I make the lines too large, the pump needs to be sized to handle the higher amounts of fuel. The drain line of the bowl also needs to be much larger than the inlet to prevent overflow. I want to stay with the Holly Blue.

LOL, its a mess!!!!

 

[Jethro]

Sorry to hyjack, this will be quick. Aren't stock Suzuki fuel lines 5/16"? Why would you go smaller to a 1/4"?

 

[lecroy]

I had a 3AN line made up to test and measured about 200ml for about 10seconds of running. This is way off from the 540ml I was looking for. I looked at the crimped ends and they are VERY restrictive. I thought 3AN would mean a 3/16 inside diameter, but the actual part measures about 0.07". When I calculated the flow for this size I end up with 190ml for the 10 seconds.

What gives? Are the fittings that couple to the line not all the same?
I looked at a 4AN and measured about 0.10". Closer to what I need, but not what I would have expexted.

 

[lecroy]

LMFAO, Its not the ID but the OD of the tubing. Crap. Now that that is cleared up and my flow calculations seem good, I still need to verify fuel consumption.

 

[lecroy]

As the fuel problems continue on the next years chop job. Everything I could find on the subject says the calculations are good.

I was thinking about the 1/4" fuel line and decided to run a test. I use two Pingle high flow petcocks on this bike. Using one of them I just stuck a section of 1/4" ID hose and let it gravity feed. I measured about 200ml again. Funny how that number keeps coming up. Anyway if I use a BSFC of 1, I get about 125HP. My stock GSXR would kick it's butt. With the pump I can flow much more than this of course.

I think I am going to give up on the floatless Keihin. The balancing act to run the N2O from the same pump and regulator is a no go with the Holley blue pump. When I had first started down this path I used gravity feed and could not get enough fuel into the carb. Then I added a small pump. This would cause the needle to leak even at 3PSI. Fuel would pour out of every little hole. Then I put in the drain. This worked fine with a feed pump and a scavage pump, but required a seperate pump for the N2O.
I tried running some tests today with the needle valve and it looks like I can hit the flow rates. So, I am now thinking about going back to a float with a drain tube. This, or I am going to order an S&S super B turbo alcohol carb. But it all sounds the same ...

"Turbo carb bowls are also fitted with a
fuel overflow fitting to prevent excess fuel entering the bowl from flooding the engine during operation. Excess fuel is normally
routed back to the fuel tank or an overflow reservoir."