Shift light + relay = RPM activated switch?

[Tony Hanna]

Maybe one of the electronics gurus can answer this one for me. I'm wanting to build a 2 stage electronic boost control with a vacuum solenoid. Pretty standard stuff.

Here's where it gets interesting. I'm considering picking up a cheap shift light off of Ebay.
One of the stand alone units that doesn't require a connection to a tach and has it's own dial to set the rpm when the light comes on.

What I'd like to do is pull the bulb out of the shift light and wire in a relay. The relay would run the solenoid for the boost control so that below the set RPM boost would be on the low setting and above the set RPM the shift light would energize the relay and send power to the solenoid switching to high boost. I might even throw a full throttle switch into the mix as well.

Does this sound like it would work?
If so, does this shift light (http://cgi.ebay.com/PRELUDE-CIVIC-ACCORD-240-S13-S14-RPM-SHIFT-LIGHT-SILVER_W0QQitemZ180090822021QQihZ008QQcategoryZ336 79QQrdZ1QQcmdZViewItem) look like it would a good starting point for the conversion?

Before anybody starts with the "just buy an rpm activated switch, MSD makes them...", I'll explain why I don't want to do that. For starters, purpose built units are expensive. Also, most of them take pills to set the RPM and I don't want to mess with having to order a bunch of pills just to make adjustments. I know you can buy a box that replaces the pills with an adjustable dial, but they're almost as expensive as the switch itself... You get the idea.:)
If this works, I'll have about $30 shipped in the shift light, $4 in a relay, and a few minutes of time to put it together vs. $70+ for an MSD unit that I'll have to buy pills for anyway.

Any thoughts?
Thanks,

[Anonymous_User]

Yes, it should work.

Are you getting too much boost at low RPM? I want to spool the turbo as soon as possible, not wait until high rpm, but that's just me.

I could understand low boost until WOT then switch to high boost, but all that would require is a micro switch on the t-body.

[Tony Hanna]

Yes, it should work.

Are you getting too much boost at low RPM? I want to spool the turbo as soon as possible, not wait until high rpm, but that's just me.

I could understand low boost until WOT then switch to high boost, but all that would require is a micro switch on the t-body.

That's it exactly. I'm running an intercooled mitsu for now, and planning to shoot for 18-20 psi with it. Problem is, from past experience it will get there at really low rpms. Low enough to be rough on rod bearings. Add to that the fact that it's on a 2.5 and will rip the tires loose from a roll at near stock boost levels and you can see where I'm coming from.
I figure with the rpm switch I can hold the boost back until slightly after peak torque to make for a more gradual transition instead of an immediate surge and the resulting loss of traction.:thumb:

[Anonymous_User]

Well, in that case I say good idea.

Yes, that shift light should work. Now, hopefully it is an incadescent lamp OR a 12v LED lamp. I don't know if it would have a 5-volt circuit to run a low voltage LED lamp. Either way, you will need a relay whose coil is rated at the proper voltage.

[Tony Hanna]

Well, in that case I say good idea.

Yes, that shift light should work. Now, hopefully it is an incadescent lamp OR a 12v LED lamp. I don't know if it would have a 5-volt circuit to run a low voltage LED lamp. Either way, you will need a relay whose coil is rated at the proper voltage.

Gotcha.:thumb:
So in that case I may be making a trip to the electronics store (does Radioshack even still carry relays?) instead of buying the $4 fog light relay from Advance...
Thanks,

[Anonymous_User]

Yeah, radio shack still carries relays. Just wait until the shift light comes in and see what kind of lamp they use.

[Tony Hanna]

Yeah, radio shack still carries relays. Just wait until the shift light comes in and see what kind of lamp they use.

Cool! I wasn't sure if they did. I know they've dropped a large part of their selection of components over the last few years in favor of stuff more marketable to the general public like cell phones, etc. Seems like if they keep going at this rate they'll end up as a Best Buy or Circuit City clone.:( Oh well, at least there's a little independant outfit nearby that stocks the right zener diodes.:thumb:
I need to check my bank balance to see if I've got the spare $ right now. If so I'll buy one of those lights and see how this idea works out.:)
Thanks for the help!

[JDAWG]

relays from advanced are more like $10. I bought a lot of them off of ebay, like 10 or so for like $20 or something and they even came with pigtails. I use them for alot of stuff

[ShelGame]

Hmm, why not get a custom cal with switchable boost levels and/or limited boost below X rpm or mph?

I use the boost vs. mph curve to control wheelspin on launch in my race car. It works well. I only allow 5psi below 20mph, and then ramp it up to 15psi by 30mph. If you really wanted it to be RPM activated, you could do that easily as well (even the stock cals limit boost by rpm).

[Shadow24]

or you could contact an electronics vendor like Mouser once you know the volts and amps for the light. i called them to find a fan relay for my megasquirt application, funky specs, primary was 12v@500mA and the switched side was 12v@14A IIRC. it was like 3 something for the relay and a buck or two shipping, totaled like 6 bucks. thing is i KNOW its the right one :) id say give em a call

[Anonymous_User]

Hmm, why not get a custom cal with switchable boost levels and/or limited boost below X rpm or mph?


Sure, that would be the ideal way to do it. Burn your own and you can set whatever you want.

But.... this guy is on a serious budget - he has to see if he can afford the $15 for the light. I imagine, then, that the calibrated ECU is out of the question.

[turboshad]

The selnoid for the boost controller essentially is a relay and will probalby draw close to the same current. You should be fine skipping the relay and hookin the bulb outputs directly to the selnoid.

DJ

[Tony Hanna]

relays from advanced are more like $10. I bought a lot of them off of ebay, like 10 or so for like $20 or something and they even came with pigtails. I use them for alot of stuff
The one I'm talking about is exactly $3.97 at the Advance here. I just bought one a couple days ago for another project. It's part # A715 and packaged as an aftermarket fog light relay. I've just been using female spade connectors to make my own pigtails.:thumb:


Hmm, why not get a custom cal with switchable boost levels and/or limited boost below X rpm or mph?
I use the boost vs. mph curve to control wheelspin on launch in my race car. It works well. I only allow 5psi below 20mph, and then ramp it up to 15psi by 30mph. If you really wanted it to be RPM activated, you could do that easily as well (even the stock cals limit boost by rpm).
I've been playing around at trying to do that and I think I've got something that would work. You answered a bunch of my questions about it remember?:) Problem is I don't have the burner yet and I'm a little short on cash for the +40's and 3 bar map. In time though...:nod: Sooner if I can use a set of 450cc DSM injectors instead of the +40's.:confused:


Sure, that would be the ideal way to do it. Burn your own and you can set whatever you want.
But.... this guy is on a serious budget - he has to see if he can afford the $15 for the light. I imagine, then, that the calibrated ECU is out of the question.
I've got a birthday coming up tomorrow and have been dropping hints about wanting a burner.:thumb: I can afford the chips and socket, it's the injectors and map that are killing me. Funds are a bit tight for everything that's not absolutely essential atm because I've been staying out of work to fix up this house, and I hate spending Tiff's money on my toys.
Springs coming, so the work will pick up and I'll have some spare cash before too long.:thumb:


The selnoid for the boost controller essentially is a relay and will probalby draw close to the same current. You should be fine skipping the relay and hookin the bulb outputs directly to the selnoid.
DJ
If it turns out to have a 12v incandesent bulb instead of lower voltage leds, I might just do it that way. I just figured the relay was cheap insurence against overloading it or having problems from inductive lash from the coil in the solenoid.

[Anonymous_User]

If you learn to burn your own chip, you can set it up for ANY injector size and ANY MAP. You can change one or both ANY time you want.

So, get set up to burn and program your ECU to run the way you want it to on the injectors and MAP that you have. Then when you can afford a 3-bar MAP, install it and change the ECU. Then do the same later with injectors.

You can run a TII up to 20 psi with good gas on +20's. Do you have the bottom end to exceed that? Do you NEED +40's? You will get (slightly) better idle/driveability from the +20's (or so I have heard).

[Tony Hanna]

If you learn to burn your own chip, you can set it up for ANY injector size and ANY MAP. You can change one or both ANY time you want.
So, get set up to burn and program your ECU to run the way you want it to on the injectors and MAP that you have. Then when you can afford a 3-bar MAP, install it and change the ECU. Then do the same later with injectors.
Right, it's just that with the stock map, I won't be able to get near my target boost without a zener and then the stock boost control setup becomes useless because the cal can't control boost at 18 psi if it's blinded by the zener at 14. That has me back to running a MBC which is what's giving me the problems in the first place. :confused:
If I had the 3 bar map, I could set up a cal for a 3 bar with stock injectors that would handle boost control and add the extra fuel manually with my fogger nozzle rig...


You can run a TII up to 20 psi with good gas on +20's. Do you have the bottom end to exceed that? Do you NEED +40's? You will get (slightly) better idle/driveability from the +20's (or so I have heard).
I think the bottom end is up to the challange. I guess I could go with +20's but the little mitsu will be leaving in favor of a Holset HX35/Bullseye turbine housing and a ported head/manifolds sometime this summer. I figured I'd just go with the +40's (or equivalent) now instead of running the risk of needing to upgrade to them later.
Thanks,

[ShelGame]

I've been playing around at trying to do that and I think I've got something that would work. You answered a bunch of my questions about it remember?:)

LOL, sorry I forgot.

[Tony Hanna]

LOL, sorry I forgot.

It's all good man, I appreciate the help.:thumb: