WOT switch

[Mopar_Nutz]

If I was to go with a dual stage boost controller for hi-low boost settings, how would I go about setting it up to automatically switch to high boost at WOT?
I've heard of people doing it, but never knew how.
It would be nice to even have a toggle switch to allow WOT to trip it too. So you can roll along the highway without having boost jump to 18-20 psi as soon as you were to hit a hill! Not to mention, I'm sure traction at 12 psi and 18+ are 2 very different concepts

Thanx, Ian

[lametec]

3 ways of doing it come to mind:

1. Attach a switch to the throttle body and let the throttle cable "pulley" (in lack of a better word) push on it.
2. Use the AC cutout relay signal (if you have AC).
3. Make a simple comparator circuit and hook it up to the TPS signal wire.

[Mopar_Nutz]

Quote:

Originally posted by lametec 3 ways of doing it come to mind: 1. Attach a switch to the throttle body and let the throttle cable "pulley" (in lack of a better word) push on it. 2. Use the AC cutout relay signal (if you have AC). 3. Make a simple comparator circuit and hook it up to the TPS signal wire.

How reliable is #1?
I don't have a/c so I guess #2 isn't an option.
How exactly do you do #3? I'd thought myself that something to do with the TPS would be how it was done. What would I have to buy and how would I hook it up?

Thanx for the quick reply "thumbs up

[lametec]

I guess #1 could be made pretty reliable, but personally I wouldn't do it.

#2 might still be possible. Find the AC cutout relay connector over by the ASD/Starter/Fan relays. If it's there, put a test light on it or something to see if it's active. Consult a wiring diagram for wire colors.

#3 would involve using an op-amp as a comparator, and drive a transistor off its output. This transistor could then drive a relay, or drive the load itself if it can handle it. You might even be able to drive the transistor directly off the TPS signal, using a variable resistor to set your turn-on point. Bad thing about that would be no hysteresis, causing the transistor to switch quickly between on/off if you hold the gas right around the turn-on point.

[Mopar_Nutz]

Man #3 sounds confusing to a non-electronics guy! hahaha Off to scour the net so I understand what all this stuff is. I like the idea of it running off the TPS so I can get it to go on at a certain time (when I want it to), instead of something else telling it when, if that makes sense? And I'd like to somehow mount a toggle switch in the car to activate or deactivate it? So when the switch is off, I have single stage low boost setting. Then switch it on so it'll be ready to use the hi boost stage at WOT.
Or am I getting too complicated for a newbie?

[lametec]

Nah, that's not hard at all.

Search for comparator circuits using op-amps. I'm sure some of them will have relay drivers on them too, especially if they're for use in automotive areas.

I wish I could tell you exactly how to do it, but I haven't really messed around with that stuff since I went to school for it! I remember how stuff works, but not enough to design the circuit.

[Mopar_Nutz]

So would the difference between #2 and #3 options pretty much be that using the AC cutout relay would just mean using something the car already has set up instead of starting from scratch? Maybe that would be a better option cuz I just spent the past couple hours figuring out what all those little parts actually DO. I think I'd be lost trying to find out what types to use!!

Also my car always sems to throw a code 33, which is A/C cutout relay. Does that mean that the relay is working but not getting a signal? Or does it mean that the computer is looking for a signal thats not there because the relay doesn't work?

I would go out and check but I'm far, far away from my car right now. I'm tryin to get all this stuff straight so that I can get to work on it when I get home. Do 90% of the thinking ahead of time while I can't actually get my hands dirty. It gives me the illusion of still working on my cars anyways

[lametec]

Since you're getting a code 33, chances are your ECU tries to control the relay.

Since your relay isn't there, it senses the open circuit, and throws the code.

Failing that, I attached a circuit diagram of a small relay driving comparator. It's based off another diagram I found, but should work. No hysteresis, though, so the relay would flick on and off quite a bit if your manage to hold your foot just at the switch over point.

[Mopar_Nutz]

well I don't think I'd have a problem with it cycling on anf off if I had the toggle switch, cuz then I'd be on low boost all the time unless I was racing, right? And I don't see any reason why I'd be at anything other than WOT when racing .

I guess the question is, what would be easier to wrap my poor little mind around. building that curcuit and running it off the TPS, or getting the AC cutout relay working and running it off there? Is it possible to pull a few minor things off a junkyard car to get it working? Or not worth it? Electronics have always been my weakest point

[lametec]

Well, see if the connector for the AC cutout relay is there. If it is, put a test light or volt meter on the dark blue wire with a red tracer. Put the other side of the light/meter to grey wire (+12V).

Start the car and let it run for a few seconds, then floor it. If the light comes on/you read +12V, your AC cutout circuit works.

The AC cutout wire goes to cavity 56 on the SMEC if you can't find the AC relay connector.

If the connector is there and working, all you have to do is get a relay, connect one side to +12V (grey wire in the connector) and the other side to the control wire (dark blue/red). Once you go WOT, the relay will click on.

[Mopar_Nutz]

so what I'm looking for is the AC relay connector over by the fan relay and all that with a dark blue wire with a red tracer and a grey wire? So this is what the relay would plug into if it was there? What exactly does the connector look like?
Once I find it I just connect a relay to it and wire that up to kick the high boost on? Do I run a toggle switch before the relay so it doesn't see any power unless the toggle is on?

[lametec]

Yes, those are the wires you'll need. The connector is just a black plug with 4 wires coming out of it. It should be the only free connector in that area, apart from the diagnostic connector.

Measure the wires first to make sure they're active. Would be a waste to hook up a relay if the wires don't work.

If you want to you can hook up an extra switch, but it's not needed. The switch would enable you to turn high boost on/off.

[Mopar_Nutz]

Wow it actually makes sense to me! hahaha Thanks for all the help man. I can't wait to get home and dig into it now. "thumbs up