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"TSR" Switch Fuel System, save money, drive on pump gas!
Component Matching #1
Page 2
Fuel weighs approximately 6 lbs per gallon. That means you pump should deliver a gallon in 2 minutes at 65 to 70 psi head pressure. That is what it will see under real world operating conditions. This is just to support the approximately 360 B.H.P. (Brake Horse Power) that your stock engine is capable of producing. Use BHP not net HP ratings for the purpose of this formula.
The formula is gallons per minute X 60 to get the G.P.H. (Gallons per Hour). Then multiply that figure by 6 to get the actual LBs in weight of fuel. The .5 BSFC ratio, (Brake Specific fuel consumption) as well as all A/F (Air/Fuel) ratios are measured in weight.
In order to have adequate fuel flow at pressure the pump upgrade should be capable of delivering enough fuel to supply a 500 to 600 HP engine. This is 250 to 300 Lbs per hr. It is important to keep in mind that this flow rating must be at 65 to 70 PSI of fuel line or rail pressure. This is what the pump will see in a port fuel injected turbo-charged application like ours.
The formula is 600 hp / .5 = 300 lbs per hr. 300 / 6 per gallon = 50 gallons per hr. 1 hr = 60 mn / 50 = 0.83 gals per min at 65 to 70 PSI head pressure.
The formula for 500 hp is .5 = 250 lbs per hr / 6 lb per gal = 41.6 gals per hr / 60 mins = 0.694 gallons per min at 65 to 70 psi head pressure.
The reason I use the 500 to 600 HP example here is that is what could be expected from a strong running upgraded TR engine.
The selection of fuel injectors will be governed by the same .5 BSFC ratio. Figuring 6 fuel injectors you can multiply the individual injector rating by six to get the projected total Lbs per hr they will deliver. Assuming that they deliver what they are rated at lets apply the formula to proper injector sizing to support a 500 to 600 HP TR eng.
There are 50 and 60 lb injectors available so lets go with those for the purpose of this example. 50 X 6 = 300 that will support 600 HP at .5 BSFC.
There should be a safety margin built in to your calculations since the more power you are making the easier it is to damage your motor. Running lean is a major cause of breakage.
60 lb injs X 6 = 360. Theoretically that should be enough to support double the 360 number in HP or 720. Don’t assume that, since just a couple of variables can skew those numbers quite a bit. Hence the safety margin.
The BSFC of .5 itself is not actually the true rate of fuel consumption but simply a rule of thumb to get a ballpark figure when estimating. The actual operating fuel consumption ratio of turbo charged engines is generally slightly richer. The ratios of .55, .6 and .65 are all incrementally 10% greater in that order and may be closer to your actual fuel consumption.
The ability of your pump to deliver fuel consistently at the very high pressure demands of port fuel injection and forced aspiration is also a big variable.
When estimating your fuel systems requirements, it’s always advisable to overbuild since the alternative consequence is possible catastrophic engine failure. The extra cost involved is a small price to pay for the insurance. The issue of compatibility is of minimal concern. The fuel system is one area that is unlikely to negatively affect the performance of the rest of the package if overbuilt.
The title of this article is component matching, sequence of upgrades. We have addressed 3 steps so far. The fuel delivery issue is a complicated one and rightly demands the time and attention to detail we have given it here.
Two more of the basic upgrades that will be needed to monitor the fuel deliver system and do the testing referred to in this article are the fuel rail pressure gauge and an adjustable fuel pressure regulator. These 2 pieces are both inexpensive and essential. The gauge should have the ability to be extended with a section of line to the easily viewed area of the windshield for testing purposes.
Since I like to keep these articles down to 2 pages, I will continue this with, Component matching & sequence of upgrades #2.
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