Lazy secondaries

[Lincster]

Hey there......I have a 92' MTX (3rd owner) for about 2 weeks now. It's a great motoring experience and I can see why SHO owners are so passionate about their rides. It seems some times the secondaries don't open..........at 4,000 RPM there's suppose to be an extra WHOOOOSSE of acceleration..........I've only experienced it 10% ..........was told it has aftermarket big bore butterflies. Huummmm..... what do I check for? Thanks.....cruise on.

 

[jayro]

I would pop the hood and watch to make sure the secondaries are opening correctly. Either have a friend help, or you can see through the opening under the hood. Also, with my BBB I lose a little right when they open and then build quickly. In mine it is a little smoother transition than when stock. Enjoy the car..
Jeremy

 

[Lincster]

Thanks

Hey there......thanks for the info.....There's a thread about factory secondaries...... maybe some of it applies to B.B.B. setup............Thanks...cruise on.

 

[hawkeye18]

BBBs are just factory butterflies with the bore on the butterflies enlarged. Stock is 57mm, BBB is 60mm, IIRC. It's not a huge difference (for that you want HBBs!) but it's definitely noticeable. It's much more noticeable when combined with ported/polished runners, gasket matching, head porting, etc.

There's a little tab in the middle of each butterfly assembly that moves when you get to 4K rpm. Open the hood, goose the throttle, and see if those little tabs move. If they don't, then check for either the vacuum reservoir (cylindrical thingy behind the intake) being unplugged or the IMRC (Intake Manifold Runner Control) module being unplugged, electrical and vacuum. Also, make sure the vacuum lines are hooked up to the vacuum reservoir correctly; it's a one-way valve. Disconnect the line from the intake and suck on it; you will know if the valve is open or not. If it isn't, then reverse the lines...

and no "you suck" jokes either.

 

[SASHO91]

BBBs are just factory butterflies with the bore on the butterflies enlarged. Stock is 57mm, BBB is 60mm, IIRC. It's not a huge difference (for that you want HBBs!) but it's definitely noticeable. It's much more noticeable when combined with ported/polished runners, gasket matching, head porting, etc.

There's a little tab in the middle of each butterfly assembly that moves when you get to 4K rpm. Open the hood, goose the throttle, and see if those little tabs move. If they don't, then check for either the vacuum reservoir (cylindrical thingy behind the intake) being unplugged or the IMRC (Intake Manifold Runner Control) module being unplugged, electrical and vacuum. Also, make sure the vacuum lines are hooked up to the vacuum reservoir correctly; it's a one-way valve. Disconnect the line from the intake and suck on it; you will know if the valve is open or not. If it isn't, then reverse the lines...

and no "you suck" jokes either.

Those are some HUGE BBB's....

Stock size is 37. BBB's are 40-41.

 

[hawkeye18]

OK, so I didn't recall correctly. So sue me! Upon re-reading those numbers after I posted I was thinking, "hey, isn't the MAF only 55mm?"

 

[firstgen89sho]

I have also noticed a difference just getting rid of the intake airhorns, you don't feel the secondaries opening as much as you do with the airhorns in there.

 

[Lincster]

will checkem' out

Hey there........... Thanks for sharing the knowledge with me.......BTW I have an 80 mm MAF , runners ported, heads ported, the 2 former owners really cared for this car. Will check out suggestions ASAP . Thanks.