Author Topic: Right RPM for performance?  (Read 2781 times)

Offline Toronado

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Right RPM for performance?
« on: February 06, 2011, 04:27:02 AM »
What RPM should the butterfly's
open on my secondaries, at the throttle linkage
point?
My car makes most power at 4400 rpm
for horse power, and 3000 for torque,
do i want the secondaries to begin to open
at 2500 or 2900 rpm?
I don't have any current problems.
just want it to be correct I think
 it said 2200 rpm when i last tried
to look.
Thanks

Offline Schurkey

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Re: Right RPM for performance?
« Reply #1 on: February 06, 2011, 09:12:45 PM »
They SHOULDN'T open based on RPM.

The throttle blades open based on linkage geometry; and as long as they're open the right amount when the throttle lever is WFO, the rest should be OK.

The air valve opens based on air demand; some say vacuum--some say velocity.  Either way, it's not directly tied to RPM; although RPM is a large factor.
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Offline Toronado

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Re: Right RPM for performance?
« Reply #2 on: February 08, 2011, 02:06:33 AM »
The linkage for the Q-jet secondary
blades is designed to be bent.
 The sec. blades
dont open tell a certain point,
that point is adjustable, &
commonly adjusted there.
Mine has been bent by previous
owner like many carbs and
seems to be opening them a tad soon.

guess I just test it my self since I
simply adjust and test.

Offline Cliff Ruggles

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Re: Right RPM for performance?
« Reply #3 on: February 08, 2011, 03:49:58 AM »
I would use extreme care bending the tab in the pic.  They are easily broken.  The secondaries are mechanical (obviously), and driver controlled.   The airflaps are controlled by spring tension and opened by the engines demand for more airflow. 

It's an excellent system.  Spend your time adjusting the spring tension for the airflaps to get a smooth transition onto the secondaries.  Let the engine decide how much airflow it needs and when.....Cliff