I'm curious what the performance impact would be. Doesn't that cut down on the amount of airflow through the throttle body?

 

It should have zero effect power-wise, but in theory this is one way to cure the hanging revs. The down-side is that the car might stall at idle when the A/C kicks in or when the power steering is loaded heavily at low engine speeds (like when turning sharply into a parking space).

Basically, this is a "hardware" solution to the hanging revs, whereas tweaking the dashpot settings in the PCM's tuning file is a "software" solution to the same problem.

Let us know how it works out - I'm really curious to see how it affects idle quality.

 

Let us know how it works out - I'm really curious to see how it affects idle quality.

Aye, cap'n - will do.

I've sanded it down a bit, and I'm about to reinstall it and go for a spin.

 

I can safely say that 7/64" is way too small - I started the car and it barely idled. Removed throttle body, drilled up to 3/16", reinstalled, and it idled well. I think this is a good size, but 1/4" might even be a little better - I don't have a drill bit that size at the moment and it's not so bad that I'd want to take the throttle body back off, so I'll leave it at 3/16" at least for now. I'll refrain from making any comments about the idle quality with or without accessories running, turning at idle in a parking lot, etc., until I've got a couple driving cycles into it and our wonderful adaptive ECU learns that there's less idle air coming in. So far, this mod is so-so; something you might do if you had the throttle body off to port it anyway. It is definitely not worth the $39 they want for their little plastic thing. I'll keep updating.

 

does their little plastic thing glue in or something?

what happens if your going along and you hit a bump and it pops outa it place...

then its sitting on top of the butterfly and when u hit the gas it falls into the intake manifold?

will they cover the dmgs to the car if that can happen?

 

It looks like it clips in a little better than that, but I wouldn't know as I've never held one in my hand. Either way, it doesn't seem like money well spent. Fast Forward Ltd. aren't a sponsor, are they?

 

I still don't really see the function of this piece. The hanging revs really is a nuisance and not a detrimental thing. The purpose of the hanging revs is acutally built into the ECU to burn off any gas that may have pooled in the intake manifold.

Why is that a good thing? Do you really want a backfire that melts your plastic intake manifold?

Just checking.

 

The purpose of the hanging revs is acutally built into the ECU to burn off any gas that may have pooled in the intake manifold.

Why is that a good thing? Do you really want a backfire that melts your plastic intake manifold?

Just checking.

Perhaps if you have swapped your EEC-V for a Holley 4160 this is an issue, but if you actually look at the location of the injectors and understood that if an engine is still running it is creating a vacuum that will pull in fuel you will see that what you have posted is a complete pile of (insert your favorite animal and the name you most like for its excrement here). Gas does not pool in your intake manifold on a fuel injected setup unless there is something seriously wrong. Indeed the hanging revs are an emissions controlled strategy that is used in concert with EGR to burn off hydrocarbons during engine deceleration, but saying that defeating this feature risks melting an intake manifold is alarmist nonsense.

 

Meh, if it pops the intake manifold, I'll get an early 2000 manifold.

W00t for me.

 

I think the real $64 million question is, if the hanging revs have been an emissions control strategy all along, how did Powerworks eliminate the hanging revs and still get a CARB exemption for their blower? Obviously, somebody cared about reducing the little "puff of exhaust" when shifting, or else Ford would never have programmed it into the PCM. But if it is (or was) important enough to include on stock Foci for emissions-control purposes, why doesn't it have to remain on a CARB-exempt supercharger kit?

While we're on this subject, I should point out that this hanging rev issue was only for US-spec Foci, AFAIK. Maybe it was for all of North America - I dunno - but I'm pretty sure that the European models never had the hanging revs.

 

Powerworks uses a aftermarket TB. Not sure if it makes a difference, but maybe that has something to do with it.

 

Our TB does have idle air provisions as does the manifold. It's actually smaller than we would like to optimally see, but we were able to work with it.

 

i made my own gasket when i changed over to a 65mm tb, all those years ago, and i made provisions to decrease the airflow through the bypass as well. Cured the problem

 

Awakening this thread for a "long term" update...

I'd have to say that this is a debatable modification. During the summer when I did this, the car ran normally, didn't idle funny or stall, even when making tight turns (such as jockeying into a parking space). However, once the weather got a bit cooler I noticed that the car wants to stall out right after startup, and unless you hold the revs at 2000 RPM for about 30 seconds before trying to move the car it will stall.

The 7/64" hole that I started with was too small, period; I ended up redrilling it up to 3/16". I suppose that if I had larger drill bits and opened the idle air passage up a bit it would probably help with the stalling, but until I get sick of the car stalling I'll keep it at 3/16" and run a high idle for a while to keep it running.

I'm a downshifter; I engine brake down hills, to stops, etc. It definitely seemed to help slow the car, especially when engine braking down a hill. Spare me your anecdotal evidence against engine braking, I've heard it all and have never experienced any ill effects after years of driving manual transmission vehicles.