rv93

ok, crazy idea, i know. i tried learning how to heel and toe shift, and its not working out. ive heard its difficult on the car, but it seems impossible for me. the only way i can do it is by using my toe to brake. thats not exactly what i want when my life depends on that brake pedal being pressed down hard. I definitely plan on learning at some point, but in the meantime...do you guys think it would be possible to somehow have a button that makes the cruise control actuator blip the throttle, allowing me to shift without losing traction on the rear wheels during hard braking?

shoebox

The cruise disengages with the brake, so I don't know how that is going to help you. I actually don't understand what it is you are trying to do. Are you trying to shift without the clutch? That's hell on transmission synchronizers. Get an automatic if you don't want to use the clutch.

TD95Z

I think he's looking to replicate the functionality built into some exotics that run sequential gearboxes. During downshifts, the engine speed is increased, bringing it up to match what it would see when actually in that gear. The result is smoother downshifts and decreased tendency to break the rear tires loose. I actually like the OP's idea, but I think it would be difficult to control via vacuum.

rv93

well, to clarify, during heel and toe shifting, you brake, shift, and use the gas the match the revs. generally done before a sharp turn that requires a downshift. since my foot wont reach from the brake to the gas to be doing the rev matching, i was hoping id be able to make the cruise control actuator do it for me. i was also under the impression that it was electric, not vacuum activated. if it works on vacuum, i have no chance of making it work, unless i use a solenoid valve from a vacuum line...

shoebox

Got it now. You are racing your "essentially stock" car on a road circuit. I don't see how the cruise could be configured to do this (btw, there is no vacuum involved). Perhaps some creative reprogramming with the PCM (idle follower, maybe?), but it would not be something you could turn on/off.

rv93

no, im having fun with my essentially stock fast car on roads with turns. and i was hoping there might be some wires right at the motor that controls the cable that i could splice into or something

TD95Z

The problem I see with this is that the engine speed would need to change based on corner entry speed and/or gear being downshifted to. To my knowledge, there is nothing that tells the PCM what gear a manual trans is in. For this to work, the PCM would need to know vehicle speed (VSS has that covered) and desired gear. Basically, you'd need to come up with a way to tell the PCM that you intend to downshift, and there would need to be some sort of lookup table that calculates the rev match based on vehicle speed vs. desired (downshifting to) gear,while also taking into account the trans ratios and rear axle ratio. Without these inputs, you'd be stuck with only one RPM that you can "blip-the throttle" to.

It's a great idea, but I don't see how the cruise control could accomplish this effectively. Too many inputs are required to run this without a computer.

EDIT: Here's a link some info on how this is done on the Nissan 370Z.

http://www.zimbio.com/Automobile+Mak...h+transmission

This pretty trick. I'd love to see someone design a system like this for our cars. Apparently such a thing exists on newer automatic-equipped Corvettes, too.

shoebox

So rv93 can buy a car already so equipped.

rv93

the 370z is where i got the idea. i have no intention of making it work like that. all i hope to do is a button that opens the throttle as quickly as the cruise control actuator can for as long as the button is pressed. it wont be perfect by any means, but a hell of a lot better than nothing.

shoebox

Study a wiring diagram of the cruise, disable the brake cancel feature and use the accel button circuit to raise engine RPM. Though, I don't know how you are going to find time to press a button when you are shifting, steering and going into a sharp turn. Might just be easier to hone your driving skills.

rv93

and where might i find such a diagram?

shoebox

Factory service manual.

lackneramanda

Hi!

I have a beautiful '98 K1500 4 x 4 5.0 auto w/83K

Any clue why my cruise control would work sometimes and not others? It also has been known to kick off when you hit imperfections in the road.

Thank you in advance for your feedback.

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93 Formula Mods: 383, LE2 Heads/Intake, 226/230 cam, 52MM TB, Magnaflow cat back, LT headers, cruise control kits, CAI, SFC, Strut Brace, Adj LCA, Adj Panhard, Relocated Torque Arm, Progressive Rate Springs, Short Throw Shifter

rv93

this is just a guess, but theres a button on top of the brake pedal that is pressed when youre not touching the brake. when that button is no longer pressed, the brake lights light, and the cruise control disengages. so if for some reason your brake pedal isnt staying up quite as well as it should, it could cause the symptoms you described.