Air Supply and TB Flap on Startup
10-25-2016
#1
OF top 99.5% creator (Formerly of the Puffinblunts variety)
Thread Starter
Air Supply and TB Flap on Startup
During cold starts or any other start what is the TB's flap doing on an EFI engine? Is there another source of air control (ex: IAVC) that supplies air at startup?
I know when cylinders are flooded with fuel that holding the fuel pedal down all the way opens the TB flap wide open. Is the flap closed during startup?
I should know this but, I don't.
I know when cylinders are flooded with fuel that holding the fuel pedal down all the way opens the TB flap wide open. Is the flap closed during startup?
I should know this but, I don't.
Last edited by Wankenstein; 10-25-2016 at 07:39 PM.
10-25-2016
#2
If you think a good mechanic is expensive, try hiring a bad one
Re: Air Supply and TB Flap on Startup
Pick a car to discuss.
Your 1997, the throttle valve is connected directly to your foot. If you move your gas pedal with your right foot, you should be able to guess exactly what the throttle blade is doing....
The rest is controlled through the IAC/FICV.
A current Honda fly-by-wire system has no IAC, all engine speeds are obtained by controlling/manipulating throttle blade position by the PCM and/or TACmodule.
(HOWEVER in the event of one particular electric throttle failure I remember: The throttle blade is spring loaded to roughly 15-20%(?) opening as a fail safe position, but when you press the gas pedal the car still could accelerate, albeit quite slowly. In the datastream I saw the PCM manipulate ignition timing to obtain an RPM increase so the car could limp along at a reduced speed... )
Your 1997, the throttle valve is connected directly to your foot. If you move your gas pedal with your right foot, you should be able to guess exactly what the throttle blade is doing....
The rest is controlled through the IAC/FICV.
A current Honda fly-by-wire system has no IAC, all engine speeds are obtained by controlling/manipulating throttle blade position by the PCM and/or TACmodule.
(HOWEVER in the event of one particular electric throttle failure I remember: The throttle blade is spring loaded to roughly 15-20%(?) opening as a fail safe position, but when you press the gas pedal the car still could accelerate, albeit quite slowly. In the datastream I saw the PCM manipulate ignition timing to obtain an RPM increase so the car could limp along at a reduced speed... )
10-25-2016
#3
OF top 99.5% creator (Formerly of the Puffinblunts variety)
Thread Starter
Re: Air Supply and TB Flap on Startup
Thanks Ezone.
I wasn't thinking of a particular make, model or year however, I also wasn't considering the different types of systems that have been employed, such as the ones you mentioned. What I'd like to know is what controls the air portion of spark + fuel+ air during startup?
My friend with the Passat feels that his engine may not be firing due to lack of air due to a possible issue of the TB flap not opening during cranking. I told him I'm not sure what the flap does at startup on his car (and mine) and if the flap is soley responsible for the amount of air needed on startups.
Concerning my '97 I don't press the pedal at all when cranking but, does that equal to the flap being closed based on your statement: "Your 1997, the throttle valve is connected directly to your foot. If you move your gas pedal with your right foot, you should be able to guess exactly what the throttle blade is doing."
I wasn't thinking of a particular make, model or year however, I also wasn't considering the different types of systems that have been employed, such as the ones you mentioned. What I'd like to know is what controls the air portion of spark + fuel+ air during startup?
My friend with the Passat feels that his engine may not be firing due to lack of air due to a possible issue of the TB flap not opening during cranking. I told him I'm not sure what the flap does at startup on his car (and mine) and if the flap is soley responsible for the amount of air needed on startups.
Concerning my '97 I don't press the pedal at all when cranking but, does that equal to the flap being closed based on your statement: "Your 1997, the throttle valve is connected directly to your foot. If you move your gas pedal with your right foot, you should be able to guess exactly what the throttle blade is doing."
10-25-2016
#4
If you think a good mechanic is expensive, try hiring a bad one
Re: Air Supply and TB Flap on Startup
What I'd like to know is what controls the air portion of spark + fuel+ air during startup?
My friend with the Passat feels that his engine may not be firing due to lack of air due to a possible issue of the TB flap not opening during cranking. I told him I'm not sure what the flap does at startup on his car (and mine) and if the flap is soley responsible for the amount of air needed on startups.
my '97 I don't press the pedal at all when cranking but, does that equal to the flap being closed
