Is it bad to run at 100% duty cycle?
Registered User
Joined: Apr 1999
Posts: 2,784
From: Rochester Hills, MI
Originally posted by Timberwolf
would be hard to go beyond 100% wouldn't it?
would be hard to go beyond 100% wouldn't it?
Actually it is possible to be above 100% duty cycle. MY 55lb injectors were running at 120% duty cycle. Ideally you want your injector duty cycle to be around 85%. What kind of fuel system are you running??
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Originally posted by IDOXLR8
Actually it is possible to be above 100% duty cycle. MY 55lb injectors were running at 120% duty cycle. Ideally you want your injector duty cycle to be around 85%. What kind of fuel system are you running??
Actually it is possible to be above 100% duty cycle. MY 55lb injectors were running at 120% duty cycle. Ideally you want your injector duty cycle to be around 85%. What kind of fuel system are you running??
Rich Krause
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Joined: Nov 1998
Posts: 71,121
From: Hell was full so they sent me to NJ
Originally posted by IDOXLR8
Actually it is possible to be above 100% duty cycle. MY 55lb injectors were running at 120% duty cycle. Ideally you want your injector duty cycle to be around 85%. What kind of fuel system are you running??
Actually it is possible to be above 100% duty cycle. MY 55lb injectors were running at 120% duty cycle. Ideally you want your injector duty cycle to be around 85%. What kind of fuel system are you running??
If you are using TTS DataMaster to get your duty cycle values, you might want to check with TTS to see if there is a bug in the program. Some of the data I see for relatively stock engines are getting duty cycles approaching 100%, and that makes no sense at all. I've suggested to several people with these oddball results that they check with TTS, but no one has done it as far as I know.
An interesting writeup on what happens to an injector as the duty cycle approaches 100%:
The last test that we run is the Tell All Test. We run each unit up in duty cycle, at 12,000 RPM, until it fails electronically. (Seen on the oscilloscope) This is prominently displayed with the laser and strobe. Most pintle type injectors fail at 86%/88% and the Disc will usually go to 92% +, depending on system pressure. All must cycle smoothly up to 85% to Pass. Bad injectors will sometimes go "static" at 70% or so and are discarded. NOTE: Most pintle injectors will increase flow rates up to 88%, 92% with Disc injectors, and then go "semi-static", half open-half closed, just before going full static. This time-out event occurs at different time/pulse width durations, in different injectors, but always produces a 50% or so Duty Cycle flow rate. This extremely dangerous situation will usually occur at the worst of times, full throttle-max boost-high RPM- just when you need 100% fuel delivery you get 50% and go dead lean. BANG!!! This problem seems to amplify a bit at higher pressures.
Thread Starter
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Joined: Mar 2002
Posts: 1,842
From: Bloomfield Hills MI
http://kak.com/camaro/car.uni
I believe the calculations for duty cycle TTS was making were correct. The injectors were approx open 20ms near 5900 rpm and thats about the same amount of time the engine has to make two full revolutions, am I correct?
I believe the calculations for duty cycle TTS was making were correct. The injectors were approx open 20ms near 5900 rpm and thats about the same amount of time the engine has to make two full revolutions, am I correct?
Moderator
Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Originally posted by Rodrigues
http://kak.com/camaro/car.uni
I believe the calculations for duty cycle TTS was making were correct. The injectors were approx open 20ms near 5900 rpm and thats about the same amount of time the engine has to make two full revolutions, am I correct?
http://kak.com/camaro/car.uni
I believe the calculations for duty cycle TTS was making were correct. The injectors were approx open 20ms near 5900 rpm and thats about the same amount of time the engine has to make two full revolutions, am I correct?
I have seen injectors go "static" and cause an engine to go boom. Not pretty.
Rich Krause
Thread Starter
Registered User
Joined: Mar 2002
Posts: 1,842
From: Bloomfield Hills MI
I am beginning to think that the pcm4less tune is trying to give the engine a lot more fuel than it actually needs. I am running ported that flow around 265 cfm at my max lift as well as an XE 224/230 112 lsa grind.
Originally posted by rskrause
Yes, but it just calculates one number from another. So the fact that they correlate does not mean they are correct. What size injectors and what is your combo?
I have seen injectors go "static" and cause an engine to go boom. Not pretty.
Rich Krause
Yes, but it just calculates one number from another. So the fact that they correlate does not mean they are correct. What size injectors and what is your combo?
I have seen injectors go "static" and cause an engine to go boom. Not pretty.
Rich Krause
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