entropy
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posted November 18, 2009 03:59 AM
 Edited By: entropy on 18 Nov 2009 12:05
fuel pressure apparently varying with temp
Dyno is a FactoryPro where we do about 4-5 sec constant rpm, constant load steps at increasing rpm: i.e. 4k then 4.5k then 5k and so on... Stop to tune where needed. This is not fast...
the primary difference between the 2 sessions wrt fuel system is fuel pressure regulator
notice that both on Oct 31, and Nov 14 fuel pressure dropped about 5psi from beginning of the set to end.
Is it the pump getting hot or the fuel getting hot.
Does the hot fuel simply make the pump hot and somehow put out less pressure???
(the fuel gets very hot, i do NOT smoke in the dyno room)
notice on the 14Nov that when i added fresh fuel, the pressure recovered strongly.
31-Oct-09 fuel pressure at dyno, OEM fuel pressure regulator, Muzzy pump
3850rpm = 40.6psi (no load) T = 0
5300rpm = 44.8psi (under load)
9460rpm = 42.6psi (under load)
10400rpm = 40.9psi (under load)
12260rpm = 39.6psi (under load)
2220rpm = 35.9psi (no load at end of dyno session) T = 72 min, 40 sec
14-Nov-09 fuel pressure at dyno, adj fuel pressure regulator, Muzzy pump
2360rpm = 47.2psi (no load) T = 0
2980rpm = 46.5psi (under load)
8160rpm = 44.5psi (under load)
12140rpm = 42.3psi (under load)
12620rpm = 41.7psi (under load)
2200rpm = 42,3psi (no load, shut down to add fuel, cool a bit) T = 69minutes
shut off motor to add fuel, cool down, prob 15 min interval
2400rpm = 44,0psi (no load) T = 0
12920rpm = 45.4psi (under load)
3340rpm = 46.2psi (no load, shutting downl) T = 3min 30sec
None of this makes a shits worth of difference at LSR or dragracing bc run times are so short. 
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Shane661
Needs a life
Posts: 11494
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posted November 18, 2009 04:24 PM
Karl, any chance it is the transducer being affected by the temps?
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entropy
Moderator
Posts: 8671
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posted November 18, 2009 09:05 PM
quote:
Karl, any chance it is the transducer being affected by the temps?
not likely, i have a gauge on it also.
But who knows, i may have spaced on looking at the gauge and comparing with logs as we ran it..
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tcchin
Zone Head
Posts: 867
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posted November 19, 2009 07:53 AM
Did you happen to notice if the pressure bypass return line to the tank was still flowing a normal amount of fuel? If so, then the issue is in the regulator.
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entropy
Moderator
Posts: 8671
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posted November 19, 2009 08:31 AM
quote:
Did you happen to notice if the pressure bypass return line to the tank was still flowing a normal amount of fuel? If so, then the issue is in the regulator.
hey Tim,
i don't know how i would notice if the return line was flowing a normal amt of fuel???
the behavior is the same with both the OEM reg and the adj reg.???
In any event, i am on to the next phase of my experiments.
Andy turned the head around in 2 days, min seat cutting to clean em all up,
new (used ) valves, heavier seat pressure, 443/415 cams
fresher pistons, new rings, newly honed block
last experiment of 2009, hope something good comes out of it.
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tcchin
Zone Head
Posts: 867
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posted November 19, 2009 01:54 PM
On my Suzukis, I can look in through the filler cap and see the bypass fuel flow. You may be able to do the same. My point is that as long as there is fuel bypassing the regulator, the pump is keeping up with demand and the pressure drop can be attributed to the regulator. If there is no fuel bypassing the regulator, then the pump has reached its flow rate capacity at that pressure, and the pressure drop can be attributed to the pump.
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entropy
Moderator
Posts: 8671
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posted November 19, 2009 10:05 PM
quote:
On my Suzukis, I can look in through the filler cap and see the bypass fuel flow. You may be able to do the same. My point is that as long as there is fuel bypassing the regulator, the pump is keeping up with demand and the pressure drop can be attributed to the regulator. If there is no fuel bypassing the regulator, then the pump has reached its flow rate capacity at that pressure, and the pressure drop can be attributed to the pump.
OK, i see.
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