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CRX 2000: Turbocharged & Rear Wheel Drive

by Frank Ewald - with Aaron Weir

This 1989 Honda CRX Si has seen it all. Aaron purchased it in 1996 for his twenty-third birthday. It was stock with the exception of an Alpine Stereo. Then came an intake and exhaust - which started Aaron down the road of improving his ride. Highly modified stock engine. A 50 shot N20 system. A 1.7 engine swap. Then a turbo. After owning and working on the CRX for eleven years, Aaron decided that it was time to move on and in 2007 put it on the market. He was ready to move on to an S2000 project. However, the car did not sell and Aaron was not going to budge on his selling price. Sometimes we see car guys give their cars away and, usually, they wish they had kept them. Aaron didn't sell and still made his S2000 build come true.

 

There's no way I can wait to show an engine bay picture. It's absolutely amazing and there are so many custom pieces included in this car that I'm sure I cannot count them all. There's a conservative 470 WHP powering this 1989 Honda CRX Si - known as the CRX 2000.

Aaron drove me around the Hamilton area and I was amazed at the ride. I mean, it is an understatement to say that it handles like a go-kart on steroids. As we were on municipal roads there was not an opportunity to push the CRX 2000 even close to the potential that it has, but it was enough to make me grin – even though I was riding shotgun and not sitting in the driver’s seat. I was doing my best to feel every bump, how the car handled the typical road ridges, the way it reacted dodging the nearly unavoidable pot holes that dotted the roads, and how it pushed me back into the seat when the car hit boost. Mind you, just a little boost.

 

If you're like me, the next money shot that you wanted is this. The rear suspension. I guess I could've made you wait until page three or four, but that simply wouldn't be fair. Fabricated in his own shop, this suspension easily handled municipal roads when Aaron took me out for a drive.

You see, this is not your typical Honda CRX Si. I doubt that Honda Engineers, even in their wildest dreams, ever thought up a car as wild and extreme as Aaron Weir’s CRX 2000. He welded and fabricated a car that combined the best of the CRX with an S2000 drivetrain. Plus he turbocharged it. And it works! This car is one that Aaron has no problem putting his two kids in and taking them for a ride around town. I had no question about jumping in and setting off on a search for some winding roads for our photo shoot.

The car has been massively remanufactured to support this change of platform and it is an incredible build. This project to build the rear wheel drive CRX began in 2007 and has been tested through time. Aaron, sponsored by Vibrant Performance, is so confident in his CRX 2000 that he has entered it into the inaugural Ontario 1500, sponsored by the Canadian Automobile Sports Clubs, and which will take place in the fall of 2015. This seven day event will visit all of Ontario’s road courses and see the cars and drivers participate in 20 event stages (8 Time Attack, 4 Autoslalom, 2 Drags and 6 Transits) with approximately 1500 kilometres travelled between the venues. There can be no question about reliability and build quality when tackling an event like this. Aaron’s co-driver for this week long venture is Robb Smith, who has been a key resource in developing the suspension and improving the handling. Between the two of them, they will be well prepared for this adventure that will test both man and machine. Another key person in the history of this build is Frank Johnson, Aaron's father-in-law and business partner at WeirTech. His willingness to help out in all aspects of the build and frequent questions (such as, will it ever run!) helped keep Aaron motivated. I was in the shop with Frank and Aaron and saw a great team. There is no question, Frank's jokes about the CRX were good natured and he was proud of the build that took place in their shop.

 

There's a lot of talk and press about Stance. As far as I'm concerned, this car defines stance. Function and form, no extras, all business.
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Comments
8695Beaters
8695Beaterslink
Thursday, September 18, 2014 7:32 AM
WOW!

Nothing else needs to be said. Except maybe WOW again.
jeffball610
jeffball610link
Thursday, September 18, 2014 7:49 AM
Yes, yes, yes! More articles like this! Tuned cars and project cars are cool, but a tuned custom project car is the pinnacle of cardome. I'd love to finish my 4G63T Datsun 510 project and show it off like this. My goal is to do something similar to what Aaron is doing with the Ontario 1500. Great car and great article. Thumbs up.
sethulrich
sethulrichlink
Thursday, September 18, 2014 9:29 AM
Ep. Ic!
Maxzillian
Maxzillianlink
Thursday, September 18, 2014 10:25 AM
Amazing project! The rear suspension setup is particularly inspiring.

That said, wouldn't it be a rising-rate suspension? I'd never heard of anyone using falling-rate on a car, but it appears common on mountain bikes.
LowFlyin'
LowFlyin'link
Thursday, September 18, 2014 11:00 AM
Ah, I remember this build thread on HT. I think this was around the same time I was starting my CTR swapped CRX build. Glad to see this was a project that was seen through to the end. ...and what a nice ending beginning.
nissannx
nissannxlink
Thursday, September 18, 2014 6:40 PM
I cannot answer the technical questions about the rear suspension. It is a cantilever/pushrod design. The rocker ratio is 1:1. I know that other experts will join the discussion. I don't mind saying that I just don't know. I just know I like it.
ginsu
ginsulink
Thursday, September 18, 2014 8:07 PM
Great article, very inspiring!

In general, the triangle that the rocker arm makes is what determines if it is a falling/rising rate design. On this car the rocker arm makes more of a 'skinny' triangle like an isosceles triangle. If you wanted more of a rising rate you could make the triangle wider like an obtuse scalene triangle (see pics below). A rising rate is usually preferable with short-travel suspension designs, to keep the car off the bumpstops. Also, a lot of mountain bikes use rising rates to stop you from blowing through the travel.

Your Image


Your Image
ginsu
ginsulink
Thursday, September 18, 2014 8:14 PM
The design below would definitely have a rising rate.

Your Image
Boxed Fox
Boxed Foxlink
Thursday, September 18, 2014 8:26 PM
That does appear to be a falling rate linkage. I tend to avoid them on road race cars. Are you sure Mike wasn't pointing out a potential pitfall when he sent you that response?
Fabrik8
Fabrik8link
Thursday, September 18, 2014 10:18 PM
A triangle has nothing to do with it, unless you start out with very defined positions for everything where the damper is roughly perpendicular to the pushrod, etc. So if you start with roughly 90 degree mounting, you can talk about triangles that are rougly 90 degrees. But, in reality you can mount the damper at any place around the rocker's circular path that you want, and the motion will work exactly the same. Then the triangle doesn't work, and now you're very confused about rocker motion.

The pushrod angle at the pushrod attachment point (the angle between the tangent and the pushrod axis at that point) and the damper angle at the damper attachment point (the angle between tangent and damper axis) are the only things that matter. Everything else is just an expression of that, in the context of where the components are mounted and therefore where they attach to that circle. It helps to think about whether things are moving toward a tangent or away from a tangent if you're visualizing the rocker motion in your head. A big part of rising rate motion has to do with moving the damper axis toward tangential, for example.

It's all just a pushrod translating linear-ish motion into rotational motion about the center of a circle, and the damper just takes that same rotational motion from the same circle and translates it back into linear-ish motion. The damper really doesn't care where it is on the circle, nor does the pushrod. The only thing that matters are the angles of how things attach to the circle.

And where do I get that T-shirt on page 7? I really want one...
Maxzillian
Maxzillianlink
Friday, September 19, 2014 7:13 AM
The easiest way I've found to figure out the motion ratio is draw an imaginary perpendicular line from the pushrod/shock to the pivot point and measure that radius. Move the suspension and repeat. Normally this is done in CAD. ;)

In this particular case the pushrod starts at near perpendicular meaning it is at its maximum radius. Meanwhile the shock is slightly over-traveled meaning that as the suspension compresses, it will gain radius. (Dividing one by the other will yield your motion ratio. Comparing the ratios over the range of motion will yield your change in rate.)

As the suspension compresses, the radius for the linkage decreases and the shock increases meaning the shock is gaining mechanical advantage. I would consider this case as a rising-rate suspension.

Fabrik8
Fabrik8link
Friday, September 19, 2014 7:34 AM
I agree, I don't see how it could be falling rate given those initial positions at static ride height.
nissannx
nissannxlink
Friday, September 19, 2014 8:29 AM
Fabrics, You can get the t-shirt through Fabricationlife.com
Fabrik8
Fabrik8link
Friday, September 19, 2014 8:34 AM
Sweet, thanks. I saw the Vibrant logo on the left sleeve and figured it was an older Vibrant shirt.
nissannx
nissannxlink
Saturday, September 20, 2014 12:29 AM
Ginsu, thank you and you've raised some interesting suspension points.
Boxed Fox, Mike wasn't making any judgement. Just a comment on one snapshot.
Fabrik8. First sorry for the autocorrect error with your name. Thanks for the great insight.
Maxzillian, thanks also for that info.
Great discussion from everyone. Again, I'm not a suspension expert nor would Aaron say he is. He came up with a design to work within the restrictions he faced with this build. And with a couple of thousand street kilometres and one track day of use, it seems to be working. Keep the discussion going, I'm certainly learning.
nissannx
nissannxlink
Saturday, September 20, 2014 8:29 AM
Jeffball610, watch for my article in October. I think you'll enjoy it too.
Mike Kojima
Mike Kojimalink
Monday, September 22, 2014 2:56 PM
Once a rocker over centers, the wheel rate falls.
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