Fuel injector sizing
#3
http://www.rceng.com/technical.aspx
About 250hp at the wheels with 80% duty cycle and about 300hp with injectors at MAX (100% duty cycle).
You shouldn't go past 80% duty cycle, so 250rwhp.
About 250hp at the wheels with 80% duty cycle and about 300hp with injectors at MAX (100% duty cycle).
You shouldn't go past 80% duty cycle, so 250rwhp.
#5
http://www.rceng.com/technical.aspx
About 250hp at the wheels with 80% duty cycle and about 300hp with injectors at MAX (100% duty cycle).
You shouldn't go past 80% duty cycle, so 250rwhp.
About 250hp at the wheels with 80% duty cycle and about 300hp with injectors at MAX (100% duty cycle).
You shouldn't go past 80% duty cycle, so 250rwhp.
Trending Topics
#8
No, you never run injectors at 100% duty. 80% duty cycle is the usual max.
#9
I'm not sure of the duty cycle, don't have a monitor on it. I can tell you we've had no problem with the car going lean at any time, we've been able to add fuel and take away - at 17 psi.
If 350 is the target, 55 will support that...actually I hope they support 365, which is what the new engine should produce when we get it to the dyno.
There are several dyno sheets out there with 380-400 with 55# injectors, not sure of the duty cycle - I do remember that Robs old car maxed them out around 410+ or so, if my aging memory serves me correct.
If 350 is the target, 55 will support that...actually I hope they support 365, which is what the new engine should produce when we get it to the dyno.
There are several dyno sheets out there with 380-400 with 55# injectors, not sure of the duty cycle - I do remember that Robs old car maxed them out around 410+ or so, if my aging memory serves me correct.
#10
Yeah those calculators can be misleading a bit. For example if you plug in Turbo S HP with a .60 BSFC then the factory injectiors are undersized. Use a .45 or a 110% duty cycle and it'll put you in the ballpark. Another consideration is the static fuel pressure. Under boost, where we make max power, fuel pressure rises based on boost signal @ the FPR. That also changes the max. That calculator is a VERY conservative estimate. If I use that I'll need 115 lb injectors for my 3.0l......
#11
Better safe than sorry I say. Are $250 worth of injectors worth risking your motor over? With higher fuel pressure, you can squeeze some more flow out of the stock 37# injectors to support around the 300-350whp area. 55# injectors would be much more appropriately sized for say the 350whp area, and that would definitely keep the duty cycles low. It has been proven for decades by the automotive industry as a whole that it is generally not a good idea to run injectors past approximately 80% duty cycle for long periods of time. Doing so can wear them out quickly and cause them to fail, stick 100% open, etc etc. In my experience, for some odd reason the stock Bosch 951 37# injectors as well as some other Bosch/Siemens injectors seem to withstand constant high duty cycles a bit better than many other brands of injectors, though it's still an unnecessary risk IMO when $250 worth of aftermarket injectors can completely bypass any potential problem.
#12
Addict
Rennlist Member
Rennlist
Small Business Partner
Rennlist Member
Rennlist
Small Business Partner
Joined: May 2006
Posts: 5,252
Likes: 6
From: Denver
-Rogue
#14
If your going with a standalone EMS then yeah, might as well throw in something a bit larger and use sequential injection.
#15
I've been told that if you size injectors too large such that you are running low duty cycles then the flow of fuel through the injector nozzle never really gets established properly due to the short time they are open meaning you don't get proper atomisation of the fuel and therefore poor mixing with the air in the combustion chamber. Is this an issue anyone has observed?