Higher PSI and shorter pulse or lower PSI and longer pulse
02-27-2014, 07:32 PM
#1
Higher PSI and shorter pulse or lower PSI and longer pulse What gets better fuel atomization assuming all other variables are the same.
Higher fuel rail PSI and a shorter pulse
Or
Lower fuel rail PSI and a longer pulse
If you have any equations/personal experience built around this that would be pretty cool to see.
Higher fuel rail PSI and a shorter pulse
Or
Lower fuel rail PSI and a longer pulse
If you have any equations/personal experience built around this that would be pretty cool to see.
02-28-2014, 10:36 AM
#2
Teching In
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At the risk of oversimplification, I would go with an increase in fuel pressure. If you increase the injector pulse width you will run out of available pulse width sooner which could cause a lean out condition at wide open throttle.(Or at max fuel demand situation) For instance if your injector pulse is at 60% and you increase it to 75% that only leaves 25% left till the injector is maxed. Obviously this is a complex question and every setup is unique with lots of variables. On the other hand if you are only at 20% duty cycle that may not be an issue. Hope that gives you something to go on. good luck
02-28-2014, 12:07 PM
#4
Dont confuse pulse width with duty cycle. They are not 100% interchangeable.
With that being said, I would always aim for 60lbs of fuel pressure on an NA build. For boosted apps on smaller cid engines (as what normally happens. Some huge turbo on a 5.3/347) you have to have an injector that flows more in boost but can act like a water hose when out of boost. Most people throw in 85s or larger hoping for 1k out of everything. Normally either the engine idles like trash and drivability is compromised or your VE table is hacked up.
If you are using boost remember 2 things. A rising rate fuel pressure regulator is your friend. And second a quality injector is predictable at every fuel pressure so make use of it.
If you need help decoding that let me know.
With that being said, I would always aim for 60lbs of fuel pressure on an NA build. For boosted apps on smaller cid engines (as what normally happens. Some huge turbo on a 5.3/347) you have to have an injector that flows more in boost but can act like a water hose when out of boost. Most people throw in 85s or larger hoping for 1k out of everything. Normally either the engine idles like trash and drivability is compromised or your VE table is hacked up.
If you are using boost remember 2 things. A rising rate fuel pressure regulator is your friend. And second a quality injector is predictable at every fuel pressure so make use of it.
If you need help decoding that let me know.
02-28-2014, 09:09 PM
#5
TECH Senior Member
There is not enough info in the question...
Each injector behaves differently.
And, there are various complications...
for example, HUGE injectors may be easier to control at idle by running a reduced rail pressure (e.g. 45 psi).
Each injector behaves differently.
And, there are various complications...
for example, HUGE injectors may be easier to control at idle by running a reduced rail pressure (e.g. 45 psi).