I have this crazy idea about rigging up 2 RC servos to turn the mixture control screws on a Holley so I can adjust the mixture and AFR while driving. Has anyone seen this done before?

 

why ? your idles circuit is only to 1/4 throttle .

 

Yes exactly, and that's where the throttle is the majority of the time in everyday traffic on a street driven car.

I've found the AFR changes quite a bit with engine / under hood temperatures. I've also found that under hood temperature changes fairly rapidly from idling in traffic to moving along at speed.

 

then ditch the old technology and go efi.

 

Its too expensive.

 

You could do it the cheap way, take the hood off and get the wife to lie in the engine bay with a screwdriver, shout clockwise/anti-clockwise commands over the howl of the wind.

 

I will have to post up a pic later when I get home. I fly R/C planes, and had a bunch of standard size servos just sitting around, so I decided to make an adjustable choke for my car, using that and a a servo tester with a potentiometer I reverse engineered. I had a push rod running off the servo directly to the choke linkage on my Edelbrock (at the time... I use Holley now) When the potentiometer was turned it opened the choke accordingly 1:1. Most servos for planes don't go past 90 degrees of rotation either direction from center, but there are a few options out there. You can remove the stop in any servo, but will lose the proportionality. I think this would be cool to try though... I wonder if any existing mixture control solenoids could be modified work with your carb, and wired to operate correctly.

 

How expensive is a custom one-off system going to be by the time you get it to do anything useful?

Unless you want to reinvent the wheel for its own sake (nothing wrong with that) you're going down a path that Detroit, Hamburg, Tokyo, Seoul and a dozen aftermarket companies thoroughly mapped out a long time ago.

 

trying to make a standard carb into a ccc with rc car part. waste of time , money and effort

 

I don't see an issue with have having servos rotate the mixture screws in and out a few turns to tune the car when needed. A reliable setup could be made for under $20 and all you'd need in the cabin would be a vacuum gauge. I get the $20 dollar number based on the price of a couple small servos, which can be had for under $5 these days and this:
http://www.meritline.com/multi-esc-s...FQWe4Aod1F4A3w

I don't see a real use for this other than it would be kinda cool.

 

How long are RC servos going to last in engine heat?

I don't even see how it's useful to have a manual idle mixture adjustment from inside the car.

 

To all you guys saying it's not going to be worth the expense.

I fly RC aircraft and have lots of servos and linkages lying around. I also already have a wide band AFR gauge and a vacuum gauge hooked up inside the car. So this would cost me practically nothing.

As someone already mentioned, I think a big issue would be finding a way to shield the servos from engine heat. I'll also need to come up with a way to mount the servos to the carb securely so vibration won't knock them loose.

Why am i going through this trouble? because having driven with the wide band gauge long enough I feel there is more room for MPG if only I could adjust the ilde mixtures while driving.

 

On a side note, carburetted piston engined aircraft have cable operated mixture controls in the cockpit as well as manifold vacuum gauges. Don't see why our cars can't have the same.

 

Because we don't drive at different altitudes and from hot climates to cold climates like planes do.

Set it and forget it. If you can actually do it right the first time, you shouldn't need to touch it again.


It wouldn't be hard to do anyway, it shouldn't take more than a day to figure out a mounting system and linkage. If in fact you are proficient in RC hobby. It also wouldnt cost you anything if you had the parts laying around. I am sure I could rig something pretty up in a few hours, would be totally useless though, and an unnecessary chunk of wiring from receiver to battery to servo's to transmitter would be a total annoyance in my car.

Its quite useless to tune your idle mixture while driving. When it in fact adjusts your "idle" mixture.

On a side note an remote idle speed screw would be interesting, and it sure would help cold starts without choke.

 

Bad idea. RC Servo's are NOT meant for that sort of duty. The engine will quickly cause their deaths, and some servo's upon dying tend to spaz out. They are not by nature waterproof either. Dust, chemicals, contaminants....

I bet they don't even last a month.

 

Lol. Is that why every single modern car has EFI constantly adjusting the mixture several times a second? I've easily seen temperature changes of 25 degrees or more from driving to work in the morning to driving back in the evening. Not to mention under hood temperature changes from idling in traffic to moving along at speed. This easily affect fuel density.

 

Yes this is the main thing that's holding me back. I'm pretty sure they would get cooked very soon.

 

No, it's for emissions reasons. Nothing to do with performance, really.

 

Whether it has any use, value, or longevity at all, I love quirky little ideas like this. Do it!

Could you remote mount the servo's, and cable drive the mix screws?

 

Yes emissions play a part, and so does performance. Otherwise Nascar wouldn't have ditched carburetors over EFI. Same for pretty much all major auto racing.

 

Hmmm. Remote mount them where? the firewall?

 

Up to you, this is your prototype. If it was me though, I'd just jury-rig it up as quick and dirty as possible the first time, to establish proof of concept. Then worry about solving problems like heat etc down the track if/when they become apparent.