engine start / stop button question

[lunarhighway]

has anyone ever tried to make a start-stop switch? mainly for use at stoplights but it could be handy for eoc as well. since i'm about to install a radio and speakers i'll spend some time under the dashboard and need to get some supplies anyway so i might as well try this in one go. i'll place two buttons on the lower dashboard in front of the gear shifter, so i don't have to move my hand behind the steering wheel to the ignition key wich is pretty inconvenien. i like the look on peoples face when my engine seems to start the very moment when the car takes of.( wich goes surprisingly smooth actually wich makes me wonder if for a second of to the starter acts as a sort of hibrid system) although every once in a while it won't start fast enough and i look a little stupid.

yet i'd like your oppinion on what i plan to do.
one start stop button would be the ultimate cool, but since i can't see how that can be done in a simple and reliable way 'ill settle for 2 push buttons. i'd like to retain all functions of the original start key.

the starter is pretty straight forward i think, i'll just place a switch parallel to the original key swicth

the stop key poses an aditional challange. i intent to stop the engine by cutting power to the ignition (how else), most push buttons i find are of the ?make? rather han the ?break? type (making an electrical contac rather than interupting one) so i figures the only option i have is to get an additional relay that will invert the action of the swich. this system will be in line with the original system so i'm a bit concearned about safety here. it's no rocket science but still,

i'll probably be getting this relay and these buttons

and here's something resembeling a schematic of what i want to build

[lunarhighway]

ok so i looked a little colser and it shouldn't be a problem getting both normal open en normal closed buttons. yet what's the best practice, use direct contacts of work with relais? appart form maybe eliminating some wireing i see no reason to use relais.

[GasSavers_Red]

You don't have to use a relay, might want to check McMaster for parts but there are switches that "break" a connection

http://www.kpsec.freeuk.com/components/switch.htm

I'd personally use a DPDT with a center off switch. Top could be starter, middle is normal driving usage, bottom is ignition kill.

[lunarhighway]

I'd personally use a DPDT with a center off switch. Top could be starter, middle is normal driving usage, bottom is ignition kill.

that was my first thought but than i'd still have to use a relay for the ignition, as that will have to be constant on, and only interupted when the switch makes contact.... i"m not sure if that's a good idea or not

[GasSavers_Red]

Originally Posted by lunarhighway

that was my first thought but than i'd still have to use a relay for the ignition, as that will have to be constant on, and only interupted when the switch makes contact.... i"m not sure if that's a good idea or not

True, forgot about that. How were you planning on tying into the ignition system? Could you use the circuit that trues off the car from the ignition cylinder?

[ffvben]

i know a few Buddy's who drag race , they have a switch to turn starter on then another for ignition. but thats on carburetors not todays fuel injected engs.

[skewbe]

I wonder if that is because the timing is so advanced that they need to build up some momentum before turning on the spark?

[Bill in Houston]

they turn on the ignition and then hit the starter.

[lunarhighway]

they turn on the ignition and then hit the starter.

i can't see a point in doing it the other way around, you'd just end up flooding the cilinders in the end no?

anyway i don't intend to build something that will allow for that, when the contacts of the starter shouldn't work either. right now i'm thinking of useing one DPDT (on)-off-(on) switch and one relay. it should be simple enough not to cause to much problems i hope. and it's be nice and ergonomic, up is on down is off. the only risk is to momentarely activate the starte while trying to shut things off.

does anyone know of a (safety) reason not to put a relay in line with the contact wire?

[skewbe]

Originally Posted by lunarhighway

i can't see a point in doing it the other way around, you'd just end up flooding the cilinders in the end no?

Yah, or make a nice backfire (not that you'd notice on a dragster) if you were dumping fuel the whole time.

Originally Posted by lunarhighway

...does anyone know of a (safety) reason not to put a relay in line with the contact wire?

It might be dangerous for someone untrained in your vehicle to be in it if they can activate the starter without the key. But the relay is just a good idea (I used some from a saturn for my ignition/fuel kill).