Anyone mod their secondary butterfly linkage?

Sincoln

Sincoln

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When the IAC was getting replaced, noticed the throttle body had dual butterflies. Then noticed the 1st butterfly opens earlier, while the sloppy linkage binding the two together rather lazily, intentionally opens the secondary butterfly at a later time, and it barely opens fully at WOT.

Was wondering if anyone tried incorporating an adjustable linkage to allow for quicker and more reliable secondary butterfly opening? Or giving it a 1:1 to ratio between butterflies so they both open at roughly the same times?
 
No one has tried this? Next time you are near the throttle body, remove the intake hose (engine off). Manually move the throttle lever and watch the butterflies. The one over the firewall-side port opens significantly earlier than the other one, acting like a very small single-bore at light throttle (smaller even then most lo-po NA 4 cylinder engines with a single bore TB). The other butterfly never really catches up until you are basically at WOT, but even then, it might be a millimeter behind with opening. Has to be leaving some HP off the table in the lower revs. Don't remember my Mark being like that.
 
That is interesting, I've never heard of that before. Might have to investigate further on that.
 
Yeah, dunno if it'd fall on it's face or not if they open identical at lower speeds. Given the delicate nature of the AX4N, it might have been Ford's way to delay power a bit, so it would take a deliberate stab at the gas pedal to make things go while still be mild enough for grandma and grandpa ;) Definitely noticed that other butterfly doesn't seem to go quite fully open under a WOT simulation. And the linkage (on mine at least) has some slop in it. Even removing the slop (might be a 1/32 to a 1/16" slop before the second blade moves) would probably make throttle more snappy.
 
I was thinking about the decrease it would make at WOT for the AX4N too. It makes sense that it would be like that.
 
Haven't messed with mine yet, but thinking a throttle return spring running in tandem with the secondary linkage, would at least remove the slack by keeping tension on the bar link at both ends w/o interfering with operation.
 
Could be the intentional design, especially for improved mpg. I spent a lot of time tinkering with 4 and 6 barrel carbs on old muscle cars. On those, the secondary (butterfly) wouldn't open up fully until vacuum was very low. The primary and secondary weren't normally open together until a sharp acceleration/WOT type condition. If they were intended to be operated together all the time, then just have one big valve for simplicity, not two. Same thoughts for 2 valves in the throttle body.

When cleaning up my Lincoln's TB last month, I did notice the "gap" in operation between the two butterfly valves. Didn't think much of it.
 
Yeah, they run fine as-is, though the play could in theory allow for the left-most blade to stick, or possibly open/shut/pulsate as certain engine speeds.
 
Went ahead and made a simple connecting bar, and swapped the factory one out. Can't make the bar shorter as it'll pre-load the secondary open, causing higher idle, but you can remove the slack and make the holes for the studs on the linkage, very close to their size, and it won't bind, unlike the factory link bar which has an irregular hole on one end, that's very loose on the stud.

Throttle response tip in, like say going 35 with your foot barely touching the pedal, then a small push, it seems to respond better. Nothing crazy though. Not going to jump a curb and destroy a window.

If attempting: IF operating the linkage and everything opens to WOT smoothly w/o binding, but all of a sudden it binds when the cruise control is reconnected, gotta play with the CC linkage end.
 
Ran across this on an article discussing 4.6L DOHC engines in the early Cobra SVT's and Lincoln Continentals.

Of course, enthusiasts are familiar with the nicely shaped aluminum intake that featured a large central plenum with long individual runners. The Cobra engine also utilizes the aforementioned butterfly in one intake port that opens at 3,250 rpm. Limiting airflow to one port improves velocity at low engine speed and enhances efficiency and power. The DOHC Cobra engine also used the twin 57mm throttle-body, 80mm mass air sensor log-style exhaust manifolds.

Inside Look at Modular V-8 Performance From 1996 to 2014
 
I’ve had many cars since 1962, but my ‘02 Conti is the first Ford product I ever owned.
I didn’t know the history of the engine, and it’s relation to the Mustangs, but I did know they had a much better overall record/reputation than the 4.6L Northstars in the Caddys.

I know many don’t care for the Conti FWD 4.6L setup.
Since I was originally looking at buying a used Caddy, that would have been FWD, the
Lincoln Continental FWD was fine by me, since the much of the reported trans problems seem to have addressed by the later years of production.

Years ago I would have been interested in tweaking to get more performance.
But alas, that time has passed.
Although I have to say my FWD Conti can accelerate very quickly when asked to.

Thanks for posting the article – I learned something - it was very interesting.
 
The butterfly the article was referring to was the IMRC butterfly from the earlier engines.
 
Sincoln said:
No one has tried this? Next time you are near the throttle body, remove the intake hose (engine off). Manually move the throttle lever and watch the butterflies. The one over the firewall-side port opens significantly earlier than the other one, acting like a very small single-bore at light throttle (smaller even then most lo-po NA 4 cylinder engines with a single bore TB). The other butterfly never really catches up until you are basically at WOT, but even then, it might be a millimeter behind with opening. Has to be leaving some HP off the table in the lower revs. Don't remember my Mark being like that.
Click to expand...

I have a 1994 Mark VIII and both throttle body blades do NOT open at the same time. The left side blade is the first to open and it opens quickly. The right side does not start opening until about half throttle or so, but the right blade does open all the way. Just not at the same time. I want to mod the linkage somehow to both open in unison. I still have the IMRC's in it.

Ive looked at my . On my car the TB is hard to get at. Its dead center up against the firewall facing "UP" with the snorkel tube attached on top. Next up, I'm trying to get in there to find where the EGR valve and TPS sensor are hiding. Its hard to see in there, this is my first car with this type of modular engine. I need a good engine diagram. Just cant see whats behind there....yet.
 
I wouldn't mess with it tbh.

The Mark VIII"s engine is fairly reliable. Though I only had mine from 62k to roughly 125k. At 100k miles, front wheel bearings, rear shocks (can mod in Thunderbird shocks from the late 90's easily enough, just use the large washers to compress a new rubber bushing against the hole in the shock tower. Tighten it good) and the oil filter adapter gasket. That gasket is a pita to get as you have to use access holes in the front assembly to get it out. When they leak, do NOT ignore it. It'll puke oil out like you have a hole in the pan and is dangerous on tires too. It can puke it out fast enough that it could run out on a long drive if unaware. Everything else was regular maintenance.
 
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