Fuel injection - Snail Shell

O.K. here goes my second post and its a strange one. I need to slow down the throttle opening of a fuel injection set up. There are eight throttle bodies and they are opening to quickly. I remember a throttle lever set up where a cam action or what was called a "snail shell" was used to open the throttles slowly and then progressively open them quicker. A variable rate opening device that used a throttle cable, not linkage. Any help on this would be appreciated.

John

 

Cable wrapped around a wheel with decreasing radii as it turns?

 

Yes, are there any commercially available? Thank you for responding, you are the smartest person I know here.

John

 

Howell EFI sold one to fit Holley Projection. His was a Nautilus shaped 1/8" plate with two 1/16" plates 1/8" larger on either side and a notch that held a barrel shaped sinker on the end of a throttle cable. The radius was large at idle, decreasing to smaller at WOT.

 

Phil1934, thank you for responding, knew that I had seen that plate before.
Unfortunately, when I called Howell E.F.I. the tech person I spoke to didn't know what I was talking about. Probably too old for him. He suggested I contact Lokar (?), I'll give it a try.

Anybody else have any input, please chime in. Thanks, John.

 

Is it silly for me to ask for more info?? Why not add more fuel faster - to match that instantaneous opening rate?? My injector works fine when I mash the pedal.

Otherwise - think about a bellcrank - normally we try to make everything "symetrical" and balanced to optimize travel - by doing the opposite you can achieve what you are looking for. If that doesn't make sense - think about a steering arm and pretend it is the big hand on a clock - when it travels from 11 to 1 - it has "X" distance of travel from left to right. If it travels from12 to 2 it has less.....from 1 to 3 less yet again. It's a poor man's "cam" all depending on how you look at it.

 

Ford uses them on their 4.6 Modular motor.

 

the efi computer should meter the fuel to match whatever throttle plate opening there is, but if the surface area of the throttle plate isn't sized to match the overall displacement of the cylinder bore, there could be an issue with tip in... you end up with full ambient manifold pressure at way less than full throttle plate opening.

maybe try grafting a stock porsche 944 throttle cam onto your efi linkage:
http://www.dietersmotorsports.com/tech/2001/944_throttle_cam.htm

 

To all that have responded to my post. I posed this question on behalf of a man named Dwayne who posts regularly on www.cadillacpower.com/forums. He has built an early Stude with a F.I. 535 Cadillac. The thread is under Studillac Rebuild Progress in the BIg Block Cadillac section. He had problems w/ the F.I. while on the dyno and I thought that the nautilus would help. It might, might not. Don't know him, never seen him. Trying to be of service.
Again, I hope I haven't stepped on anyones toes. Check it out. It shows what time and patience can do.

John

 

Levers are a good idea...look over all the junk that makes up a progressive 3-2 setup, lots of pieces to play with. To fiddle with angular effects, get a board and some cardboard...make carboard levers and links, tumb tack levers to boards for their pivot points, pivot moving parts with thumbtacks pointing up. I find this allows visual thinking that is easier for me... You could even have split linkage like when a 3-2 picks up the slack to start the secondaries moving.
On the nauitilus...how about a pulley, cable goes over pulley and anchors to it. Experiment (cardboard again!) with attachment point of cable, attachment point of pull rod from pedal, and eccentric placement of axle of the pulley. This hurts mt head, but I think it would make sense mocked up in cardboard.

 

PS...look for an outfit called "Small Parts, inc."
They make mechanical bits for experimental engineering and mockups. Stuff you need and stuff you didn't know existed.

 

I had the same proiblem, what worked for me was on line with what Bruce said about levers. The accelerator arm that the pedal moves has its first contact near the pedal pivot which moves the throttle slow but as the pedal is presed on down the top of the pedal contacts the arm moving it fast. It uses the slow movement at highway speeds making it a smoother speed transition and town driving a lot better. Its in a '31 coupe with injection on a flathead (4x2's).

Vergil