Motorcycle tank capacity

[racer x]

Hey Milton. You bike looks good. I cant wait to here it .
    My thinking is and that is all it is at this stage. ( I do have an oil containment pan ordered mind you)

 My plan is to run slightly lower compression than I am now Say 12 to1.The 100 octane from one side of the tank goes into the carbs .The bike runs great and with a lot of timing advance it will make lots of power (for 249cc) .


Then from the other side of the tank to an electric fuel pump I will feed 118 octane fuel. that will go in with the nitrous . 15 /18 jets and cool things down. At the same time I will move the timing back enough to keep it from having problems.
Don't have specific numbers yet .But I am starting with the tank for a better aero position and building the rest as I can. That is why I want to still run in the gas class.

[racer x]

racerx, its easy and best to get confirmation from
scta tech.....

my opinion is that you are carrying or have the capacity to carry more than 1.32 gallons of
fuel.......no matter how many reserviors......so ok for modified.....

IS that the answer? as long as I have the capacity to carry more than 5 liters of fuel it is OK for modified.No matter how many tanks or reservoirs are on the bike.

[Seldom Seen Slim]

I'll ask for the "higher up" folks to give an opinion.  gotta call one of them today anyway -- will see if 1.32 g is total onboard capacity or per-tank capacity -- and put you to rest either way.  Thanks for the perseverance.

[racer x]

I'll ask for the "higher up" folks to give an opinion.  gotta call one of them today anyway -- will see if 1.32 g is total onboard capacity or per-tank capacity -- and put you to rest either way.  Thanks for the perseverance.

I asked Deb to ask Todd. I hate to be to persistent .But I need to get the desine finalized.
 I could make the tank 1.32 gallons feeding the carbs.Then another .5 to feed the nitrous. Packaging is everything on a little bike is critical.

[joea]

may want to rethink the premise...

if your running on the lower octane thru carbs
all the time, and then always have the 118 as
fuel enrichment with nitrous....your net
octane that the cylinder is seeing may be
woefully inadequate........

ie..you will have cylinder pressure that will find the
weakest link in the hydrocarbon chains present.....

just be careful...

[Dean Los Angeles]

I doubt if anyone cares if you have more than one fuel source. It would be considered one tank no matter how you split it up. If you had a stock tank with a separate holding tank for the other fuel I don't see any difference as long as it conforms to the safety rules.

As far as running different fuel for nitrous, is there some fact here or are you guessing. Octane is a measure of anti-knock only. The amount of heat in the fuel is a whole different thing. Two different fuels with the same octane rating can be very different.

ERC 110K has an octane rating of 115 and a heat release per unit rate of 19,800
ERC A-8C has an octane rating of 120 and a heat release per unit rate of 19,683

[Seldom Seen Slim]

I got distracted and the post I started to write -- didn't get posted.  So, delays notwithstanding, here's further comment -- from someone with more whiskers than I (at least when it comes to ECTA rules):

If both (or all) fuel tanks are completely plumbed -- petcock, hose, fuel pump, filler cap, etc -- and the total capacity of the entire group is more than 1.32 gallons -- the bike may run in the Modified class.  The modified rule says fuel tanks must be at least 1.32 gallons capacity. 

Dean's got a good point, and I'll further it -- at Maxton, with the run time being so short -- is there time for the fuel switchover to happen completely?  Say you make the switch at half-track.  You'll be in the lights within 20 seconds or so (considering your probably speed) -- so will the fuel line from the switchover point to the carbs/injector rail exhaust the first type of fuel and get completely over to the second type -- in time?

However - - the answer to the question is that I was in error -- total fuel capacity on board is what will be considered for this item.

[Cajun Kid]

Eric, I would reconsider using two fuels. One fuel and N2O should achieve your desired result,,, mixing the deal may give you an undesirable ... boom...

Be careful my Friend,

Charles

[racer x]

Eric, I would reconsider using two fuels. One fuel and N2O should achieve your desired result,,, mixing the deal may give you an undesirable ... boom...

Be careful my Friend,

Charles

I am trying to be a careful as I can be.But I am in uncharted territory. Not much hard data on modifying the 250 ninja for real. Jon and Mike have done some with the turbo but I am using a different engine and a different approach.And doing it myself . So any help or advice will be greatly appreciated.I am learning as I go

   From the beginning. The 249 cc four stroke engine makes 26 hp stock .It is different from the previous engine because it uses shim under bucket valve train . The old engine used rocker arms.
   For the last three years I have tweaked the engine to 33.7 hp (last good dyno run.) Most of the power comes from feeding it lots of fuel and advancing the timing . I got 1 hp just from not tapering the timing off at High RPM .  I also have forged pistons and other good stuff.

I have a programmable ignition system with two ignition maps that can be switched with a simple open or closed circuit.My plan is to run 45 deg on map 1 then when I push the nitrous button a relay will switch to map 2 and that map will have 42 deg or so.


I found from dyno testing that 45 deg of advance works best and I use Rocket 100 all the time.
  I have not tried running 118 but I GUESS it would loose power If I ran that fuel .I may be wrong there.

I have a thick copper head gasket to lower the compression" some "for the nitrous  . But that would make running 118 all the time worse.

 I was told to use high octane fuel with nitrous to cool the charge . That way I can get away with more timing advance than otherwise.    
    Maybe I should can use rocket 100 with the nitrous and It will be OK . That I don't know . My thinking is "somemore " Octane when spraying nitrous would help guard against Knock

As far as switching things during a run .I don't need to switch anything on the run.Fuel runs from the tank to the carbs like normal.Then when I energize the nitrous system .Fuel will be delivered to the solenoids from the electric fuel pump.The solenoids will open with a thumb button and a WOT switch

I run a 1/4 mile in 14 sec .4th gear at 90 mph .I only go 110 in the mile. So I am in 6th gear at the 1/2 mile. I will just spray from the 3/4 mile marker on . That is a 7 second shot. I could spray from the 1/2 mile but that would be for later .(Like Sunday afternoon in October) haha
I will have to start another thread about jetting and pump and bottle pressure for 10 hp on a 15 cubic engine.

[Seldom Seen Slim]

Bottle pressure is usually around 900-1100 psi no matter how much you're dosing the engine.  The jets are set for that pressure, so to speak.  If you've got a tiny bottle you might run into problems with the pressure sagging as the contents are used, but spraying 10 isn't much -- so it'd have to be a tiny bottle for you to suffer much sag.  We use a 10# bottle on my 1340 cc bike -- but for two reasons.  First of all -- it's got to spray for about 45-50 seconds on the long course at Bonneville, and second because we use the nitrous to actuate the air shifter, too.  That last item doesn't use much, but we don't want to have any issue - nor a need for a bottle warmer under normal conditions.

Back to dual tanks -- both are plumbed to the engine, right, and you theoretically could change tanks on the fly, right?  Is the system gravity feed or is the fuel driven by a pump.

[racer x]

I have not built anything yet . But no only one side of the tank would be plumbed to the carbs. Then the other side would go to a fuel pump.Before I got the idea to use two fuels .I was going to remove the gas gauge sender and put a 1/4 inch fuel nipple in a plate and cover the hole where the level sender was. But my tank is to wide .So I need to build a new tank anyway.

As for my GUESS. I was going to use 7.5 psi of fuel pressure through a 18 fuel jet.And with 1000psi of nitrous in a 2.5 lb bottle I would regulate it to 900 psi and spray that through a.15 nitrous jet. I would make the fuel line shorter than the nitrous to make the system go rich at first . Dose that work at reducing shock to the bottom end?

I think I will have enough pressure to last 7 to 10 seconds
 
Also about fuel lines. Some Kits have braided steel fuel line.I like that but again packaging is everything.Can I use that clear red and blue line that comes with some cheaper kits.It will fit better .But I like the steel lines better.

[RansomT]

Racerx, I like what you are “thinking/doing”.  Remember that when you spray you are only going to add enough fuel to offset the ~18 HP gain.  You will be mixing the 2 fuels at a about a 2:1 ratio, so your octane will be lower than the 118.  BTW, the effects of “cooling” are more felt with Nitrous than the fuel.

A 2 ½# bottle will be just fine with that small of spray especially if you regulate it to 900 psi.  When I was running a Nitrous bike, I used two 28 jets with a 2 ½ bottle (dry shot).  I had it regulated to 850 psi, but I heated the bottle to 1250 psi.  Spraying only 6th gear, the bottle psi would drop to right above 850 psi.  5th and 6th, the pressure would drop to the high upper-700s.

[racer x]

Thanks Encouragement is a big help.
  I don't think I can get 18 hp from nitrous But that is what I need. It will be fun trying.
So maybe I should just go with a single tank and have two outlets one fill cap and run 110 octane fuel for both the carbs and the pump?

[LSR Mike]

I'm not a serious bike guy, only having owned a couple of Honda 350 Four's.
but for the switch between octanes, why not have 2 different tanks, same shape, or not; with the 2 different octanes. Just switching tanks?  use one for each class, would be included in the class change inspection?

Out of the box?

[racer x]

The reason for using two fuels is to get a little more octane when spraying nitrous. I don't want to run hi octane with low compression because it may cost me power .I only have 30 hp to work with.If I lose 3 hp that is 10 %

  .My concern is this
If the total of both tanks is 5 liter . 2.5 per side .But when I run in the gas class I only have half in use .The other side is empty and sealed .Is that tank still legal for modified class?

      It could be thought of at that point as a 2.5 liter tank with a 2.5 liter cavity welded to it.  My concern arises from people putting things inside there tank to lower capacity allowing them to run in altered. I don't want to be an altered.