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Feels like a four-barrel...


Gone but not forgotten
Jan 30, 2001
Hermosa Beach, CA
1987 Z51 Silver Coupe
'Splain something for me please.

Why is it that when I accelerate, say from 25-30 mph, and just steadily roll on the throttle until I open it up all the way, it reminds me (and feels like) a time when I had carburetors on my cars. Ya know? It feels like when the secondaries kick open on a four barrel, yet we all know there's only the one set of butterflies on the TPI throttle body. ;)

It's a good feeling, don't get me wrong. I'm just curious to what effect is occuring; is it a "venturi" effect, with the incoming rush of air helping to boost along more air? :confused

Just a thought.
i would venture to say that there are a number of reasons you feel this!! alot probably has to do with throttle position!! with all the sensors calling all the shots!! at partial throttle settings your timing is altered as is the fuel pressure regulators, when you mash the gas all the way, the computer goes into wide open throttle mode,adjusting timing and fuel delivery, in that mode you will definately "feel the butterflies opening" that is my opinion on that, and no i am not a gm engineer,but i did stay in a holiday inn last night!!:D hehehe

power band

the tuned port injection system has runner lengths that are (tuned)to accentuate the intake air flow pulses into the intake ports in the 2500rpm to 4000rpm range(aproximately .it depends on the cam timeing etc.) this is what your feeling the efficiency of the engine cylinders greatly increaseing in effect this results it the cylinders getting a fuller load of fuel/air mix that increases the power you feel in that rpm range, thats why chevys engineers designed the TPI with the those long curveing runners to get a ram/tuneing of the intake charge to increase torque. because there is only a few ways to cheaply add low end torque to an engine (some others are bigger displacement.increased crank stroke and higher compression ratio) these were ruled out because of emissions , need for increased engine cooling or fuel mileage concerns at the time

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