Just thought that I would share the results of an experiement with y'all.
I have a NA 455 engine, with the Fel-Pro (i.e. FAST) controller. I use this car as my daily driver, and strive for both performance and drivability/gas mileage.
Ever since the FI has been installed, I have not liked how difficult the car is to drive around town- just touching the throttle slightly can be enough to launch hard, making it uncomfortable and probably not helping the gas mileage. (Turbo 6 cars probably don't have nearly this sort of problem, because they have to wait for the turbo to spool up before they make their HP- with an NA car and blown/supercharged car, the HP is all right there waiting for you to touch the gas pedal).
My throttle body is a 1000 CFM 4-barrel with progressive linkage. I thought that maybe if I could restrict the airflow on the primary bores somehow, it would be less "touchy".
My first idea was to make some sort of restrictor that fits over the primary bores, with a small (3/4"?) diameter hole. But after thinking about it, I realized that this would not really affect low-throttle performance, and would only decrease airflow under high throttle position.
So I did some checking- the throttle bores are 1.75" diameter, and I found that a raquetball (from your local sports store) is 2.25" diameter. Bought some, dropped it in the driver's side primary throttle bore. I thought this would work because on a progressive linkage, you already have an airflow imbalance- the primary throttle bores are more toward the front half of the engine, therefore the rear half must not receive as much air. So by the same token, what if the right side of the engine received more air than the left side? Probably won't be noticable.
Initial driving around was much improved- now 1/4" of throttle travel was a decent takeoff from a stoplight, and not spinning the tires. Overall, driving around was better.
My concern, though, was air distribution. Since I can only block one side or the other, I wanted to make sure that I wasn't running lean on one side and rich on the other. Since the raquetball was on the driver's side, the oxygen sensor (in the passenger side exhaust pipe) would see lean if this was a problem, and make corrections.
Results at 70-75 MPH:
Original: 16% TPS, about 8.5% injector DC, about 48 kPa, O2 correction around 0-2%.
With raquetball: about 26% TPS, about 9.8% injector DC, 52-53 kPa, O2 correction around 7-9%.
Summary: The test failed. Drivability was much improved, but gas mileage went down because half the engine was running rich and half was running lean. The engine seemed to shake a bit also- probably from running imbalanced right-to-left.
Just thought I would share that...
-Bob Cunningham
I have a NA 455 engine, with the Fel-Pro (i.e. FAST) controller. I use this car as my daily driver, and strive for both performance and drivability/gas mileage.
Ever since the FI has been installed, I have not liked how difficult the car is to drive around town- just touching the throttle slightly can be enough to launch hard, making it uncomfortable and probably not helping the gas mileage. (Turbo 6 cars probably don't have nearly this sort of problem, because they have to wait for the turbo to spool up before they make their HP- with an NA car and blown/supercharged car, the HP is all right there waiting for you to touch the gas pedal).
My throttle body is a 1000 CFM 4-barrel with progressive linkage. I thought that maybe if I could restrict the airflow on the primary bores somehow, it would be less "touchy".
My first idea was to make some sort of restrictor that fits over the primary bores, with a small (3/4"?) diameter hole. But after thinking about it, I realized that this would not really affect low-throttle performance, and would only decrease airflow under high throttle position.
So I did some checking- the throttle bores are 1.75" diameter, and I found that a raquetball (from your local sports store) is 2.25" diameter. Bought some, dropped it in the driver's side primary throttle bore. I thought this would work because on a progressive linkage, you already have an airflow imbalance- the primary throttle bores are more toward the front half of the engine, therefore the rear half must not receive as much air. So by the same token, what if the right side of the engine received more air than the left side? Probably won't be noticable.
Initial driving around was much improved- now 1/4" of throttle travel was a decent takeoff from a stoplight, and not spinning the tires. Overall, driving around was better.
My concern, though, was air distribution. Since I can only block one side or the other, I wanted to make sure that I wasn't running lean on one side and rich on the other. Since the raquetball was on the driver's side, the oxygen sensor (in the passenger side exhaust pipe) would see lean if this was a problem, and make corrections.
Results at 70-75 MPH:
Original: 16% TPS, about 8.5% injector DC, about 48 kPa, O2 correction around 0-2%.
With raquetball: about 26% TPS, about 9.8% injector DC, 52-53 kPa, O2 correction around 7-9%.
Summary: The test failed. Drivability was much improved, but gas mileage went down because half the engine was running rich and half was running lean. The engine seemed to shake a bit also- probably from running imbalanced right-to-left.
Just thought I would share that...
-Bob Cunningham
