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Chris Ross
Joined: 07 Jan 2008
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Ted Simmons
Joined: 03 Apr 2007
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Location: United States, Maryland, Silver Spring
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 Posted: Tue Mar 29, 2011 1:07 pm Post subject: Fuel consumption |
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| Quote: | | Chris Ross - I have come to the conclusion that the 4 gal fuel cell in my car is just too small to make it through a longer event like the ARRC at Road Atlanta. I'm in the process of working with FuelSafe on designing a new bigger cell for my car, but I have some questions. I'm very space limited in my F600, especially on height so I want to do some type of collector or internal surge tank to try and maximize the amount of fuel I can use. FuelSafe isn't sure which would prove to be a better solution for this particular situation with a fuel injected engine. I am leaning towards making the cell with an internal surge tank in one corner of the cell with a low pressure in tank fuel pump feeding it and the suction and return lines for my high pressure external pump in the surge tank. Problem is that the height of the cell is so shallow they are having trouble sourcing a small in tank pump that lays on its side or has a inlet fitting so they can plumb a short piece of hose and a pick up. The other option is a collector with three ball check valves. This would be a simpler solution since I wouldn't need a separate low pressure scavenge pump, and would hold a little more fuel, but I just don't know enough about fuel cell design to know how affective these collectors are. I figure I need to run the cell down to around 1/2 gall of empty with no fuel starvation. What have been your experiences with collectors versus scavenge pumps? Any recommendations on a scavenge pump? |
I noticed your question regarding fuel consumption over on Apexspeed forum and copied it above so people won’t have to look it up.
I’m surprised by the volume of fuel the 600cc engine appears to consume. With the fuel injection I would have thought the usage would have been less not more than a two-stroke engine. My experience with a 2003 Yamaha R1 (1000cc) was I used about 3.5 -4 gallons during a National race. I’m really surprised the 600cc would consume more fuel. Anyone have any thoughts on why it would use more fuel? Glen Cooper has also said the Novakar used a lot of fuel (5+ gallons) at the ARRC. Does the McMahan conversion use a lot of fuel? I haven’t seen them complaining about it. What makes their engine use less fuel? Does running higher than stock fuel pressures contribute to the problem?
My R1 experience required I place a smaller “sump” tank in the car and feed it with a low pressure pump. The high pressure fuel pump was fed from the sump tank and I never had a problem pulling the final few drops of fuel from the cell. |
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Chris Ross
Joined: 07 Jan 2008
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| Posted: Tue Mar 29, 2011 5:11 pm Post subject: |
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I never ran mine much with a competitive two stroke so I don't know how they compare in fuel consumption. Jay said he just underestimated the length of the race at the ARRC and just didn't put enough fuel in it. Another 1/2 gal and the car would have been fine. The Novakar benefits from a more upright fuel cell also which helps prevent fuel starvation. The KBS fuel cell cavity is so long and wide that it will fuel starve quicker in a corner. Carbs also hold some fuel in the bowls so they will tolerate a little bit of fuel starvation as long as the corner isn't a long one. Fuel injection doesn't have any reserve so any air bubbles that get picked up will most likely cause the engine to hiccup.
My biggest issue is my cell held approx. 20 lbs according to the scales at VIR which means it wasn't even 4 gallons, more like 3.5 gallons at best. There is just no way to make a 1 pace lap + 19 race laps + 1 checker lap for the ARRC on 3.5 gallons. So no matter how I look at it I need a new fuel cell. I am a very firm believer of do something right the first time, even if it costs a bit more, and you won't have to do it again. This new 5.5 gallon cell I am going to order should be plenty of capacity, but I don't want to take a wait and see approach on fuel starving in the corner because of a pick up issue. Question is how to accomplish this. A ball check valve collector is simpler, but it is a more passive approach. A internal surge tank being fed by a low pressure pump is a more active approach, but adds a bit of complexity (and another failure mode with a second internal pump. I'm in a bit of a quandary as to which path to take.
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Jay Novak
Joined: 15 Mar 2007
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| Posted: Tue Mar 29, 2011 6:07 pm Post subject: |
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I also think a big issue with fuel consumption is that we have not had much if any development on how to use the fuel pressure. I think that we are using too much fuel pressure thus running the engines a bit rich & using more fuel. I think things will get much better when we understand what is the proper fuel pressure.
We will have a Lamda on our next car & should be able to dial it in very quickly.
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Ted Simmons
Joined: 03 Apr 2007
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Location: United States, Maryland, Silver Spring
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| Posted: Tue Mar 29, 2011 7:17 pm Post subject: Fuel pressure |
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| I had a Power Commander and a lambda sensor on the R1. Fuel consumption did go down after dyno tuning the fuel curve. I think part of the problem is with just using fuel pressure to get the right mixture. |
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Chris Ross
Joined: 07 Jan 2008
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| Posted: Tue Mar 29, 2011 7:19 pm Post subject: |
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Jay has a point. When I ran the ARRC I had not tuned the car so it was running a bit rich. The car now has a proper tune for the restrictors so the gas mileage is probably a bit better.
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Chris Reinhardt
Joined: 04 Dec 2005
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Location: United States, New York, Ossining
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| Posted: Wed Mar 30, 2011 6:19 am Post subject: |
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| Chris Ross wrote: | | Jay has a point. When I ran the ARRC I had not tuned the car so it was running a bit rich. The car now has a proper tune for the restrictors so the gas mileage is probably a bit better. |
Also the fact that you are running restrictors, less air=less fuel.
A good rule of thumb for a brake specific fuel consumption is 10 gallon an hour for every 100hp.
When I raced Superkarts we had 45 minute races and we were real close on fuel, I built a small 2 quart accumulator tank put in series with the main tank, without a vent, it worked perfect.
CR
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George Bugg
Joined: 20 Aug 2009
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Location: United States, Alabama, Toney
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| Posted: Wed Mar 30, 2011 7:34 am Post subject: |
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So, Chris... uh.. Chris R. ... well, Chris Ross... 
What fuel pressure are you running?
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Chris Ross
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WCM McMahan
Joined: 24 Jul 2009
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Location: United States, Georgia, covington
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| Posted: Wed Mar 30, 2011 12:20 pm Post subject: |
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I believe the car are using around 3-3.5 gallons a race. Maybe a bit less, but close to that. The reason we didnt have this issue with the snomobile stuff is due to the float bowls storing available fuel. This is what Chris and I have came up with that makes the most sense anyways. When I got home from this last race, I took the fuel cell apart and discoverd a bit over 1 1/2 gallons left in the cell. However, when we took it to the test site, it was starving for fuel. Upon further investigation, we noticed that the pickup wasnt all the way on the bottom and the design wasnt very good at all. Sloved the problem with a in-tank fuel pump and collector tank. Now the car runs on less than a 1/2 gallon of fuel. How much further will remain unknown as i was getting tired of laps at the test site around the culdesacs. After 20 laps of that, it takes it toll on you. Especially when you dont fit tight in the car and bounce around in it like a bb in a coke can. no comments need on that one Ted. [img]  [/img] |
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