Need ideas for a progressive throttle on Derek's EFI manifold

[Derek]

Well I've got about a year of daily driving on this rig and I'm ready to fix something that's been bugging me for a while. Getting it of the line smoothly. The throttle is just too touchy at the bottom end. Here's a shot of what I'm currently using

 

I can't seem to come up with a good way to make it progressive without going to an eccentric and cable arangement.

 

Anyone have any ideas on a progressive setup that uses the rod configuration I have?

 

Thanks

Derek

[JSM]

...

Edited April 9, 2010 by JSM

[RTz]

Hi Derek,

 

You should be able get closer to what you want by adjusting the geometry of the middle pivot....

 

 

 

 

Shortening "leg A" would slow the throttle down.

 

Making the angle shallower, between "leg A" and "leg B", you'll get a slower initial response, with increasing rate as you get closer to WOT.

 

It will probably take a few trial's to get it working fully, and to your liking. You might try building a simple sacrificial circular part (to temporarily replace the L-shape link), with multiple holes, so you can easily experiment.

[Sven]

I really like your linkage and "L-crank" setup, wish something that nice existed for sidedrafts (without spending TWM level of money, that is).

[olie05]

Ron hit it on the money. This is simply a bell crank, Same idea that the pushrod suspension guys are using to turn their linear rate springs into effective "increasing rate" springs.

 

The only other option is to go for an eccentric cam with a throttle cable, as you mentioned.

[Xnke]

I'm currently looking at the same thing, but I still need the rotary motion of the SU throttle set-up. Even with my SU's, the part throttle modulation is touchy, and with the twin 50mm TB's its gonna be even more so.

[Leon]

Hi Derek,

 

You should be able get closer to what you want by adjusting the geometry of the middle pivot....

 

 

 

 

Shortening "leg A" would slow the throttle down.

 

Making the angle shallower, between "leg A" and "leg B", you'll get a slower initial response, with increasing rate as you get closer to WOT.

 

It will probably take a few trial's to get it working fully, and to your liking. You might try building a simple sacrificial circular part (to temporarily replace the L-shape link), with multiple holes, so you can easily experiment.

 

You took the words right out of my mouth (and the picture out of my brain)! Thanks for posting Ron, I was going to eventually if no one else thought of simply changing the geometry. How lazy I've become!

[Derek]

Thanks Ron. Looks like a workable idea.

 

I'll cut a couple test ones out of corian to get a feel for it.

I'll update with results.

 

Thanks Derek

[Derek]

Success!

on the first test I opened up the angle 10 degrees. Throttle response was smoother. Went another 5 degrees and that was just right. I shortened the link that's parallel to the firewall and got my full throttle back. Did last nights and this mornings commute and it was a huge improvement. I can actually lug through a turn now without lurching.

 

Thanks Ron

 

Derek

[RTz]

[woldson]

Lurching is such a classy thing to do!! Make you feel like a real MAN!

 

Congrats Derek!

[olie05]

That was quick. I guess it bothered you enough to do something about it NOW.

[Derek]

That was quick. I guess it bothered you enough to do something about it NOW.

Well I had a little free time in the Bridgeport so i figured I'd better get it knocked out! And it was bugging me for year.

 

 

 

 

Derek 

 

 

 

[Tony D]

Send your old bellcrank to JeffP, it will make the transition from the Superflow 901 Dyno linear actuation nicer than what we have currently cobbled up on there now...

 

Though sadly it will likely be off that by the time you get around to reading this!

[TimZ]

Well I've got about a year of daily driving on this rig and I'm ready to fix something that's been bugging me for a while. Getting it of the line smoothly. The throttle is just too touchy at the bottom end. Here's a shot of what I'm currently using

 

I can't seem to come up with a good way to make it progressive without going to an eccentric and cable arangement.

 

Anyone have any ideas on a progressive setup that uses the rod configuration I have?

 

Thanks

Derek

 

Refresh my memory, please - is that engine hard mounted (i.e., aluminum plates for engine mounts)?

[Derek]

Send your old bellcrank to JeffP, it will make the transition from the Superflow 901 Dyno linear actuation nicer than what we have currently cobbled up on there now...

 

Though sadly it will likely be off that by the time you get around to reading this!

 

 

 

The old crank is still sitting here on my desk! 

 

 

 

[Derek]

Refresh my memory, please - is that engine hard mounted (i.e., aluminum plates for engine mounts)?

 

 

 

Hi Tim

 

 

Not hard mounted but I have a torque plate welded across the drivers side mount. There is very little movement under acceleration.

 

 

 

 

Derek 

 

 

[TimZ]

Not hard mounted but I have a torque plate welded across the drivers side mount. There is very little movement under acceleration.

 

I hate to say it, but I'm thinking from looking at the geometry of that bellcrank, it's not going to take very much movement to make a pretty significant change in throttle position, which could be contributing to the touchiness that you are experiencing. If the engine can move at all, it would be a good idea to isolate the engine movement from the throttle movement. Ideas anyone? A throttle cable would work, but you didn't want that as I recall (I get it - I like my old school mechanical linkage too )

[Derek]

I hate to say it, but I'm thinking from looking at the geometry of that bellcrank, it's not going to take very much movement to make a pretty significant change in throttle position, which could be contributing to the touchiness that you are experiencing.  If the engine can move at all, it would be a good idea to isolate the engine movement from the throttle movement.  Ideas anyone?  A throttle cable would work, but you didn't want that as I recall (I get it - I like my old school mechanical linkage too )

 

I figured that's where you were heading with that question! I think it must play into it for sure. But opening up the angle has made a big enough difference that I'll probably be sticking with this arrangement. It's still touchy but compared to what I had it's a huge improvement. Theoretically I could make a cam wheel to drive a cable over to the throttle lever. I may give that a try some day but my to do list is so freeking long right now it's beyond "back burner"

 

 

 

 

Derek 

 

 

 

[Dan Juday]

I hate to say it, but I'm thinking from looking at the geometry of that bellcrank, it's not going to take very much movement to make a pretty significant change in throttle position...

 

You can minimize, or even negate motor/throttle position movement by extending the link from the bellcrank to the butterfly arms. This can be done by connecting at the #3 or #4 TB rather than the #6. Simple trig, lengthen the "a" side and reduce the COS error.