MFI Throttle airflow

[gdee123]

Any ideas why Cylinder 1 would be drawing ~ 25% more air than the others ( @ 1000 and 3000 rpm). Air bypass adjuster is screwed in all the way, the throttle stop screw is so backed off that the lever won't reach ( even with the linkage removed). I suspect the innards are coked up, its just that the other five are perfect ( air flows all the same, crisp action), why no1?

Car is running very well, I discovered the air thing in tracking down ( and curing!! TG for CMA) another problem ( judderring under load at 2000 rpm mainly in 2nd gear when accelerating: throttle - pump linkage was 112mm; reset - problem cured!)

[pwd72s]

Here's a great compilation of info on Pelican...Glad to hear you're running well.

http://forums.pelicanparts.com/showt...hreadid=269190

[spydr32000]

Have you check your butterflies are all closing off at the same time, not a twisted shaft, or a butterfly which has slipped in the shaft causing it to not close properly? Are all the linkages correctly adjusted on the throttle shafts?

[gdee123]

Paul

That's a good compendium, right enough. Trawled but not a huge amount on throttle bodies. CMA refers to Chemtool for de-carboning thottle innards. Haven't seen this in Ireland, I wonder would injector cleaning petrol additive work, neat?

Mike

I am reluctant to take the throttle assy's apart, bearing in mind the car is running sweet, but its an itch that will surely get itchier. Linkages seem OK, ie all throttle stops are resting nice at current linkage legths. Any non invasive way to check the trueness of the butterfly/shaft orientation?

[tfiv]

I am reluctant to take the throttle assy's apart, bearing in mind the car is running sweet,


If it ain't broke, don't fix it! Your instincts are correct.

[gdee123]

Wise words, Tom, you're right of course. But, it occurs to me that here we are, all with this wonderful obsession. The need for speed is primeval: just look at the Olympics. Type 911 presented an elegant means, an ideal design - useful, innovative, accessible, addictive.

All of the posts to this forum reflect this fine obsession, I am not unique in trying to fathom the ins and outs of how the ideal design can be optimised. But, if the car is running sweet, wahay what fun!

[Zeke]

Can't you look down into the stack with a small flashlight and a mirror? If there is something down there, you might be able to see it. Have you applied some spray at the base when the motor is running? You know, you could have a cracked TB. Many have cracked due to overtightening. It's usually the ear (on the metal stacks, too), but stranger things have happened.

Now, in my case, it's worn bushings. Can't tune the car well at all. But, it's on the list, along with about 40,000 dollars of other things.

[tfiv]

Wise words, Tom, you're right of course. But, it occurs to me that here we are, all with this wonderful obsession. The need for speed is primeval: just look at the Olympics. Type 911 presented an elegant means, an ideal design - useful, innovative, accessible, addictive.

All of the posts to this forum reflect this fine obsession, I am not unique in trying to fathom the ins and outs of how the ideal design can be optimised. But, if the car is running sweet, wahay what fun!

Garrett, I'm well aquainted with the urge! I've been messing with a 72 MFI T recently. After going through "check, measure, adjust" I had the car running (I was told) probably as well as a 100 + K original car will. However, I never could get the sychronization right on. So, despite being advised otherwise, I messed around with the basic throttle stop settings. After doing this it took me many hours just to get it back to it's former level, and never any better. To be fair, it probably needs the pump done, and the MFI T's never ran that well anyway. That's my story - and the rational behind my advice! Good luck. - Tom

[spydr32000]

Zeke, you beat me to it the butterflies are visible from the top of the stacks. These should be checked in the idle/closed position as well as full throttle,if there is a problem you should be ab le to see enough, if not lift the stacks off the throttle bodies, this will give a clear view.

Tom, I would be very surprised if this was caused by the MFI pump as it has nothing to do with individual cylinder air flow.

[glaverbel911]

Obviously your valve corrolation is totally off for cylinder#1 and it needs to be properly adjusted to bring all 6 in sync.
With the bleed srew completely closed and the #1 throttle open,,, you are not producing the proper amount of vacum , thus adversly affecting your distributor function and timing settings... and you are losing low end power and throttle responce off the line...

Robert.