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  #241  
Old 07-20-2012, 10:57 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Someone else asked about how I wired up my brake system and basically trying to understand the vacuum switches in general. I thought now's a good time to finally write up my vacuum box in more detail as well as how to adjust Square-D switches. A lot of people have these switches but there isn't much out there on how to set the hysteresis.

Everything you will need: MDF for the box, tube, pump, vacuum switch, vacuum gauge, check valve, muffler, lots of $ worth of pipe fittings and clamps from your local ACE hardware, NPT die set, pipe thread teflon paste, and some ABS pipe if you are building a reservoir (recommended, I can pump my brakes 2, sometimes 3 times before the pump kicks on again). Note I was redoing my brake system so I already had a previous reservoir built (will rebuild here).


If anyone with the same equipment wants to build the same exact box, this fits perfectly in a CRX spare tire well. Here's my cut list:


Build the box, glue with wood glue, brad nails are extra credit.


While that was drying, I took apart my old reservoir and found the culprit for my inability to hold a vacuum. Don't buy this crappy AutoZone "universal" check valve. In my scan of the system below, I give the part name for a good valve.


Okay, here's what we're building:


The "left end" hooks to the brake booster where your old ICE used to supply vacuum. Note that my vacuum settings are pretty low, this is because I live at high altitude and after leaving my pump on for like a minute determined the highest it could hit was about 17.5" Hg, with time to reach that exponentially higher after 16.5", so that's where I set my high limit. Low limit was at about 11.5", the lower this goes the longer you can go without the pump going on after a brake, but you don't want to go too low or sacrifice brake performance. So I just found a good tradeoff in that the pump can pull it back to high level in a few seconds of pumping, and 11.5" Hg felt still pretty strong at the pedal. You'll pretty much never use the gauge for anything but setting it, since it's mounted in the box. You can always do a clear lid if you want, or mount the gauge outside the box, but I figured if I'm having brake issues, it's just a few screws to open the box and I like everything being contained in there and so I know nothing in the trunk can mess with the brake system. I listed the McMaster-Carr part numbers for the muffler, gauge, and valve on the schematic. Also note that you point the valve in the direction the pump will suck. It will be labeled, but you can always check it by sucking on one end of it (don't blow, some valves don't reliably work the other way to pressure vs. vacuum, I've found). The outlet of the pump has to come out of the box so the air has somewhere to go, so this is the part I put outside the box (since the box must be sealed). Then I ran that tube through a hole in the trunk, into a little nook behind my batteries and attached the muffler, then rolled that up in carpet padding to silence it more.

It's actually decently quiet. You can hear it when you sit in the garage and start the car - this is the most common time you hear it cause nothing else is on and there's (hopefully) not traffic in your garage. Also, the pump will always have leaked out by the time you get to it. I find the vacuum leaks so slowly I can sit for 15 minutes without hitting the brakes before it hits the low trip point and kicks on the pump. When you are driving or have the radio on slightly, you can't hear the pump. It's funny though, cause my wife and I were still shocked by how loud it *seems* but really it's because it's intermediate. For example, we make my pump go off, then started her Lexus to compare the noise and it's like her car was deafening. But we've been trained to think that's normal for a car to be that loud - so of course my car seems louder just cause the pump's not on all the time and you don't get used to it. Posting so I don't lose all this...

Last edited by notailpipe; 11-14-2012 at 12:58 AM.
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  #242  
Old 07-20-2012, 11:26 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Back to the system...

Build the reservoir out of 4" ABS from a big box store. Very strong, light, cheap, and when you buy the little black ABS "glue" it's completely airtight. Drill and then tap NPT threads for barbs. Another thing I learned from my first version: never use the ABS glue compound to glue in barb threads! For one, it may not actually make a great bond with metal. For two, you'll never get it out again without breaking something. For three, you don't need it, and that's what they invented teflon paste for! You just put a little on the threads and it will (over a long time, like days/months) gel more and more. It seals well right away and the advantage of this is that when you turn on the system, any leaks will pull the teflon paste in to the holes and kinda self-heal any minor leaks. Also you run less chance of dripping ABS glue clogging a hole (had that happen too). So just use the paste.


Rough placement of where the parts will go in the box (as drawn in schematic):


Now I take a brief aside and mention how to adjust these Square-D vacuum switches. My exact model is a GAW9016. Others should be similar, but make sure it's a vacuum switch, not a pressure switch! I know some people have figured out how to turn a pressure switch into vacuum... power to them, but I didn't do that.

First remove the cover of the little box part. There will be a dust gasket under the cover but things in here aren't actually under vacuum. The bottom right are the N.C./N.O. switch connections, either can be made. I forget which one I used, I guess it depends on what the switch makers considered "normal." Bottom left is where you adjust hysteresis. Top right ring with grooves is where we'll adjust the top vacuum point.


But first we have to hook it all up...

Here is everything connected and after I mounted the parts and lined the box with carpet padding for sound absorption. Just following the schematic I posted in the previous post. As for wiring, it's pretty simple. You have +12V coming from the Ignition signal. This wire needs to be able to carry a few (8-10) amps. Not shown but outside my box on the red wire I have an inline fuse carrier with this fuse in it. That you do want outside the box, so if it blows you can quickly check it. The other end of the pump goes to chassis ground. Anywhere in series in the circuit you insert the vacuum switch connections to break the circuit. For this part, you want to find connections on the switch that are closed, because you haven't hooked anything up and shouldn't have a vacuum yet, you want essentially the pump to be on right now. That closed connection should open when the vacuum hits the high point, which shuts off the pump. Once your circuit is hooked up you can test it with the current hysteresis points. Note that your high point may be so high your pump can't achieve it. If this happens your pump will run forever which it isn't designed to do, so if it runs more than a minute, disconnect the fuse. If it is able to achieve the level, you should see it pump up, watching the gauge climb, and then stop at some point. Then you should *not* be able to see a leak on the gauge, if there is one it should be so slow it lasts 5-10 minutes without pumping. Then sit in the car and hit the brakes a few times and it should kick on again. When this is working we can adjust it.
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  #243  
Old 07-20-2012, 11:58 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Once you are ready to adjust, you twist this ring with a screwdriver to set the high point. Try not to damage it too much, it can be hard to twist. I don't think you want to lubricate it though because you don't want road vibration to adjust your settings.



Then using a screwdriver, adjust the differential vacuum here. For example, if this was set to 5" Hg and your top end was 22", then it would turn off at 22" and turn back on when it dropped down to 17".



Put some more noise-absorbing carpet pad on the top, and some caulk to seal the top. (Also probably want to line the tire well with padding - these things are loud!



Put the top on and you're done!

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  #244  
Old 07-20-2012, 02:50 PM
swoozle swoozle is offline
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Yow, that's a $300 switch! There isn't an equally robust, more cost-effective solution?
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  #245  
Old 07-20-2012, 03:25 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

1. Mine was $100, and I'm seeing similar on eBay. $75 used, $150 new. Used is fine, they are very well made.

2. It would be worth even $300 for the reliability (hence safety) plus there is a lot of value to being able to adjust the hysteresis amount. I bought one of the $35 switches you see around here that has 3" Hg of hysteresis. My pump was on/off every 2 seconds, sometimes it was even unstable, flicking on/off at like 10Hz. If you don't want your EV ridiculed, you will want more than 3" of hysteresis. Learn from my mistakes!
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  #246  
Old 07-20-2012, 05:57 PM
swoozle swoozle is offline
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Thanks, that makes more sense. Note to self: Don't buy new switch from Allied. Don't know why I didn't check ebay, it isn't like I'd buy a new $500 IGBT...
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  #247  
Old 11-14-2012, 01:20 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

It's been a long time since I posted any updates, and I've been thinking about the car a lot lately so I figured it was time. I'll try to keep things short though. I've been driving the car since last December and most of the "updates" I'm posting are still things I did last year to it, just lagging far behind. The car has mostly been done except for a few minor things I'll point out later.

First of all, I wanted to post a picture of this tool that I used frequently toward the end of the conversion. I managed to live without one but once I had one any custom shapes I had to trace were so much easier. Basically you just make a template shape with the tool and then trace the shape onto the piece to cut. Pretty self-explanatory with a picture. Here's me tracing an (old) version of my brake pump solution. This was when I was testing out the Audi/VW brake pumps (loud):



Another thing that's since been added is clear plexiglass covers over all the battery packs to protect people from getting shocked and to protect the batteries from damage due to metal objects dropped on them or from liquids. Here is the rear rack, complete with stickers off eBay:



And similar for the front packs:



I also added an underbelly plastic cover underneath the car to reduce aerodynamic turbulence and drag. I templated it up with cardboard first. The holes go around the rear suspension pivot points and the slits align the underbelly pan to the rear battery box protection angle iron:



The template transferred to coroplast (would get something a little tougher next time around). Extremely slick!

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  #248  
Old 11-14-2012, 01:26 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Finally, converted the old gas fill neck hole to a 120VAC plug and had a little fun with the old "unleaded gas only" sign

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  #249  
Old 11-14-2012, 01:49 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Then work began on the body work and paint job. In the end we hired someone professional to do most of the work (repairing door/hail dings, sand, prime, paint) but we did a little prep work ourselves.

Taping off the car to restore the trim to OEM black (instead of sunfade black):


Door trim restored:


This picture represents everything that was wrong with the car cosmetically. Note the hugely cracked, barely intact windshield. It was already cracked several long cracks from highway rocks, but then removing/installing the dash we pressed against it several times, cracking it further. Inside, you can see the ghetto universal seat covers from Walmart. I eventually replaced these with some (expensive!) but nice looking seat covers made by a company right here in Colorado. Not sure if I have any pictures of the new one, but it's custom made by hand to stretch over a CRX seat perfectly (they sell all types of models of cars). In the end that was the way to go as I'd wasted enough time trying to put racing bucket seats or Honda Accord seats in there instead, but the seat rails never aligned and it was going to be a lot of welding. The custom covers were less work. Lastly, you can see the fading paint job, particularly on the roof.


Professional bodywork begins:


He pulled out the sheet metal where someone had backed into my rear fender panel. Unfortunately on the CRX the rear fender is one piece with the main body so you need to pull dents, you can't replace the panel alone. He was able to pull it, smooth it, and fill the rest. You can't even tell it ever happened. Amazing.






Finally, the aftermarket hood I bought is prepped and painted. This is the last picture I have of the work-in-progress painting.


That's all for tonight, I'll post some pictures soon of the final product!
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  #250  
Old 11-14-2012, 02:21 AM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

"Nice one brother"http://www.youtube.com/watch?v=CpgX1pxcizc, this is gonna look propa tidy when finished!!!
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