Question: Carb Secondary

[Tim81]

Hello 81er

Can one of you fine people tell me at what RPM does the secondary open on a stock Qjet E4ME?

Thanks Tim

 

[Hib Halverson]

Secondary opening is not RPM-dependant. It's airflow dependant. As the engine accelerates and airflow reaches a certain quantity, the secondary air valve begins to open and allow airflow through the seconday barrels.

 

[Peer81]

You can see it at your throttle pickup. I think at 2/3 or 3/4 open throttle the secondairies will start to open.

Greetings Peter

 

[Nut]

Secondary opening is not RPM-dependant. It's airflow dependant. As the engine accelerates and airflow reaches a certain quantity, the secondary air valve begins to open and allow airflow through the seconday barrels.

Hib.... on a slightly different carb topic; my stock carb on my '81 does not "howl" like the Q-jet that was on my '72. Is this typical for this carb or are my secondary's not opening fully? Carb seems to be operating fine, no hesitation, flat spots or bogging down. But I do miss that howl when you stomp on it.

Thanks............... nut

 

[lars]

The current version of my Q-Jet paper has an entire section dedicated to Q-Jet secondary operation - it describes how the secondary side works and the causes of non-operational secondaries. Drop me an e-mail if you need a copy:

V8Fastcars@msn.com

There is a significant difference in sound between a 1972 and a 1980 vehicle. In 1973, the EPA mandated "noise polution" requirements, which required better muffling of engine noise at wide open throttle. As an example, Pontiac had intended for the 1973 GTO to have a functional Ram Air system through the NACA-style hood scoops on the '73 model. Due to the new "noise polution" standards, Pontiac could not get the car to meet noise limit requirements with the open hood scoops, and all '73 GTOs had closed scoops and a well-muffled air cleaner. If you put your 1972 air cleaner and inlet system on your '80, it will likely make the same sound as your '72.

Lars

 

[Peer81]

Nice, that's a thing I didn't know

Greetings Peter