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mfi turbos rule
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that figure will be different to all engines.
a better way would be the lb's of fuel per hp , per hour
use this method and you can actually flow the fuel system and get a ball park figure, to start off at.

most mechanical injected engines will be around 1.25 to 1.35 lb's of fuel per hp, per hour...
There will not be alot of power difference between these figures, when you drop under this, the plugs start to b urn off the cad plating.

hope this is the answer you are looking for ??

cheers
Ash
 

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Discussion Starter · #3 ·
i dont have an "accurate" HP reading, because of either tire spin/clutch issues on the dyno.

im using 1050 as the Hp @ the crank in my calculations.

so..

BSFC = (lbs/hr)/ brake HP
lbs/hr = (inj cc) (#of inj)/ 10.2

another problem i have is.. how much fuel these injectors are actually flowing @ XXX psi ?

so ill make 2 calculations one using 1680 cc and one using 2100 cc
(supposedly a 160lb injector will put out 200lbs @ 80 psi ?? )

14 inj x 1680 cc / 10.2 = of total fuel lbs/hr = 2305.882
14 inj x 2100 cc / 10.2 = of total fuel lbs/hr = 2882.352
_______________________

from the logs we have 10 inj @ 100% and 8 inj @ 45%

100% of 1680 = 1680 x 10 = 16800cc/min / 10.2= 1647.058
45% of 1680 = 756 x 4 = 3024cc/min / 10.2= 296.47

1647.058 + 296.47 = 1943.528 total lbs/hr being consumed by the engine

1943.528/ *possible brake # = 1.850 bsfc

with that in mind. we burnt an electrode and the plugs are showing heat in them.

any ideas ? do i need to go back to math school ?
 

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Discussion Starter · #4 ·
using the 2100cc number
from the logs we have 10 inj @ 100% and 4 inj @ 45% duty

100% of 2100cc = 2100 x 10 = 21000cc/min / 10.2 = 2058.823 lbs/hr
45% of 2100cc = 945 x 4 = 3780 cc/min / 10.2 = 370.588 lbs/hr

2058.823 + 370.588 = 2429.411 total lbs/hr being consumed by the engine

2429.411/ *possible brake # = 2.313 bsfc
<- is that right ?


with that in mind. we burnt an electrode and the plugs are showing heat in them.
 

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Discussion Starter · #5 ·
mh said:
to get the actual flow numbers at xxpsi you have to dynamicly flowtest the injectors (test them at all pulswidths, most injectors are not lineare in their output)
but if you assume the injector flow is linear this formula works.
squareroot(new pressure / old pressure) * old flow rate.
V(80/43,5)1680 = 2278,3cc

from what i've read alcohol FI cars usualy range from 1.1 - 1.3 bsfc
why\how are you running 14 injectors? if it's a 4 cylinder it makes more sense to run either 12 or 16?
does somewhere such as RC engineering do the dynamic flow testing of the injectors ?

after all these calculations were made, and perhaps sometime in the middle of these calculations, i found a grip of formulas provided by RC Engineering,

RC Engineering - technical

the guy we have been using to tune the car has been doing this stuff for years, in his findings he states it takes about 2lbs of alcohol fuel/ per HP. now after reading very little (what ive done in the past 2 days or so) i see recomended BSFC numbers for what i belive is gasoline engines NA .45-.55 bsfc, turbocharged gas engines .60-.65 bsfc. simply doubling the gasoline turbocharged number would put us about 1.20-1.30 which is what ive seen others write, as well as you tell me. during the 1st dyno sessions we had found a number of 1.7-1.8 as the bsfc, but the timing number was super low, and the wideband showed lean, but the sparkplugs did not show any signs of heat or anything that would tell us we are in the wrong 'window', other than a little bit wavy of a HP curve, and what seemed to be down about 75-100hp. after throwing a bunch more timing & more fuel at it (wideband still showing lean, until we got up to aroun 2.0 bsfc) the car picked up huge power.

after talking to a fellow racer over the weekend, he claims to be using a 1.1lbs of fuel per HP made. i dont know if i should belive, or just call bs, based on what we have found thus far ???


SIXTYdashONE said:
i think they are running 12 and then 2 injected into the upper charge pipe.. Id dig up a picture but im too lazy
exactly what it is
 

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mfi turbos rule
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4,503 Posts
the figures i got , where from flowing the fuel system, once the engine was tuned on the dyno.

The retuning the engine for the drag strip, racing the engine in the car at the drag strip., then flowing the fuel system again.

More fuel was added to gain the desired Lambda readings.

The fuel usage, per moroso slide rule hp , was around the 1.25 - 1.35 lb's of alcohol per hp.

This was in the .72 to .79 lambda range.
Colour on the plugs , (base ring cad plating) found in the .82- .84 Lambda range.

Data from mechanical injection only.
Wedge headed engine.

Cheers
Ash
 

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i dont have an "accurate" HP reading, because of either tire spin/clutch issues on the dyno.

im using 1050 as the Hp @ the crank in my calculations.

so..

BSFC = (lbs/hr)/ brake HP
lbs/hr = (inj cc) (#of inj)/ 10.2

another problem i have is.. how much fuel these injectors are actually flowing @ XXX psi ?

so ill make 2 calculations one using 1680 cc and one using 2100 cc
(supposedly a 160lb injector will put out 200lbs @ 80 psi ?? )

14 inj x 1680 cc / 10.2 = of total fuel lbs/hr = 2305.882
14 inj x 2100 cc / 10.2 = of total fuel lbs/hr = 2882.352
_______________________

from the logs we have 10 inj @ 100% and 8 inj @ 45%

100% of 1680 = 1680 x 10 = 16800cc/min / 10.2= 1647.058
45% of 1680 = 756 x 4 = 3024cc/min / 10.2= 296.47

1647.058 + 296.47 = 1943.528 total lbs/hr being consumed by the engine

1943.528/ *possible brake # = 1.850 bsfc

with that in mind. we burnt an electrode and the plugs are showing heat in them.

any ideas ? do i need to go back to math school ?
I have been there before.. Chances are the injectors aren't actually flowing anywhere near what you would expect them to at the increased pressure. I have had had pretty good luck estimating (caluclating) fuel flow as above on some applications, but saw that the 160's seem to hit a wall as far as flow, in spite of additional base pressure. The only sure way to know how much fuel you're moving is to get fuel flowmeters on the car (not cheap, but a very powerful tool).

-Chris
 
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