We tested different spring rates on an alternate Acura Integra before we purchased struts or springs for our project car, and found that soft lowering springs and OEM struts resulted in a pretty mean lean through the corners.

After we found our Honda Challenge project car for $500 at a tow yard, and then had Autopower put a roll cage in it, we were ready to start improving the car’s performance. We decided to begin with the suspension, because the guys at TEM Machine Shop were still building our B18A1 engine, so we had nothing better to do than start playing with the chassis.

 

TESTING

As we were trying to decide on the best bang for our bucks as we built our budget Honda Challenge car, there was a lot of debate about which direction to go. Talking with a bunch of Honda Challenge racers, we found out that everybody has a lot of opinions about car setup, and about springs and struts. We wanted to test a few theories with brake and suspension choices just to be sure we get the best performance possible from our project car. While we were waiting for our cage and engine to be completed, we slapped some stickers on a very stock Acura Integra and went out to see how competitive the car would be and to test some different components. Our testing resulted in some pretty obvious answers. 1. We needed to upgrade the suspension. 2. We needed to upgrade the brakes. 3. We desperately needed to get our blueprinted engine from the machine shop because a tired motor with 220,000 miles resulted in the following finishing position: not first, which you all know is last.

Somebody replaced the left front spindle on our DA Integra with one from a DC Integra before we bought the car. The two pieces are almost identical, but they are different enough to cause alignment issues, and using the DC part in the DA Integra is not allowed per Honda Challenge rules. We upgraded our stock studs with ARP long studs for longevity and for using wheel spacers.
Somebody replaced the left front spindle on our DA Integra with one from a DC Integra before we bought the car. The two pieces are almost identical, but they are different enough to cause alignment issues, and using the DC part in the DA Integra is not allowed per Honda Challenge rules. We upgraded our stock studs with ARP long studs for longevity and for using wheel spacers.

 

SUSPENSION

After testing and before we went crazy and started buying a bunch of crap on Ebay, we read the NASA Honda Challenge rules to ensure we didn’t waste any time or money on something we couldn’t legally use in the class. What we learned from the rule set was that other than coil-overs, we really couldn’t do a lot to the suspension. The parts needed to be stock and they needed to be mounted to the stock location with one special dispensation: parts that allow for camber adjustment can be added to the car. So, by process of elimination, we could replace the upper control arms with nonstock pieces because they allowed for camber adjustment. The same applied to the rear of the car and for rear toe. We picked up adjustable pieces from Hardrace, which allowed for camber and toe adjustment. Those pieces were stronger than stock and came with spherical bearings, which was an added benefit to our upgrade.

There is no rear camber adjustment on an Acura Integra until you swap out this part. We used a piece from Hardrace because it came with spherical bearings from the manufacturer, which saved us the trouble of upgrading them.
There is no rear camber adjustment on an Acura Integra until you swap out this part. We used a piece from Hardrace because it came with spherical bearings from the manufacturer, which saved us the trouble of upgrading them.
Honda Challenge rules allow for upgrading a rear toe-adjustment piece. We did that with an adjustable unit from Hardrace, which came with solid bushings. These are easy to use and can be adjusted while the car is on the ground if you have the right shorty wrench.
Honda Challenge rules allow for upgrading a rear toe-adjustment piece. We did that with an adjustable unit from Hardrace, which came with solid bushings. These are easy to use and can be adjusted while the car is on the ground if you have the right shorty wrench.

For bushings, Honda Challenge rules allow for any type. We have used polyurethane in the past on other Acura Integra racecars with great success, but talking with the top Honda Challenge guys in the country, they were all unanimous about spending the extra money on getting spherical bushings throughout the car. With the sticky Toyo Proxes RR tire, which is the spec tire for HC, the car can really get some side load and begin to push the limits of bushings, causing the geometry of the car’s suspension to change, which is a bad thing. Solid spherical bearings fix that issue for maximum adhesion. We pulled the trigger and ordered a complete set for the entire suspension.

If you look online for suspension parts for Hondas, you will find yourself in a sea of lower control arm choices. Don’t bother buying any of them because they aren’t legal in Honda Challenge 4. Stock is your only option, but you can swap out rubber bushings for spherical bearings.
If you look online for suspension parts for Hondas, you will find yourself in a sea of lower control arm choices. Don’t bother buying any of them because they aren’t legal in Honda Challenge 4. Stock is your only option, but you can swap out rubber bushings for spherical bearings.
Here you can see the stock lower control arm with the spherical bearing placed into the unit by Kingpin Machine Inc. They did an excellent job upgrading the piece.
Here you can see the stock lower control arm with the spherical bearing placed into the unit by Kingpin Machine Inc. They did an excellent job upgrading the piece.

Then came our biggest debate: struts. This is where our Honda Challenge build started to be less of a “budget build.” We bought the car for $500, but it was looking like we would spend more than $500 per corner on struts. We knew we wanted to go with a coil-over shock setup because that was allowed in the rules, and it would allow us to adjust the ride height to the minimum 4-inches. It also would allow us to corner-balance the car. Remote reservoir shocks are cool, but they are not allowed in H4 — and cause a 75-pound weight penalty in other classes — so that was off the table. We knew we wanted adjustability in rebound and compression to help dial-in the car, but in talking with HC racers, nobody could really agree on the “best” strut for the money.

Honda Challenge 4 rules don’t allow for a remote reservoir strut, so you need to find a single-canister, dual-adjustable strut that can handle high spring rates. The Motion Control Suspension set is lightweight and has 14 adjustments for rebound and compression. Additionally, this is a coil-over system, so we could adjust the ride height and corner-balance the car.
Honda Challenge 4 rules don’t allow for a remote reservoir strut, so you need to find a single-canister, dual-adjustable strut that can handle high spring rates. The Motion Control Suspension set is lightweight and has 14 adjustments for rebound and compression. Additionally, this is a coil-over system, so we could adjust the ride height and corner-balance the car.

Then we saw the new NASA prototype car, the Elan NP01, was using Motion Control Suspension units. Talking with Honda Challenge 2 National Champion Jeremy Croiset, who ran MCS struts on his CRX and his new NP01, he recommended the units. A check of the Motion Control Suspension website showed they built a set for the DA Integra chassis, which was a nice thing to see.

Honda Challenge rules don’t allow for swapping suspension parts, but they do allow for adding camber adjustment. Therefore, you can swap out the upper control arm if that control arm adjusts camber. Hardrace makes a tubular A-arm, which is stronger than stock.
Honda Challenge rules don’t allow for swapping suspension parts, but they do allow for adding camber adjustment. Therefore, you can swap out the upper control arm if that control arm adjusts camber. kin makes a tubular A-arm, which is stronger than stock.

Throughout this project we have found a lot of aftermarket companies only build parts for the DC chassis Integra (94-01) and not our DA chassis (90-93). Essentially the DA just doesn’t feel the love from the aftermarket and it has made our project more challenging. Not having to get a set of struts modified to fit the DA chassis or be revalved for a certain spring rate saved us time and money. That meant MCS got our business.

The Motion Control Suspension’s 2WNR dual-adjustable strut has 14 adjustments for compression and rebound, adjusted separately, to get the car dialed-in perfectly. Another thing I liked about the struts was that the location of the adjustment was on the top of the strut. This way the strut can be tuned quickly for different tracks, rain versus dry conditions, etc. I like easy, and these were easy.

One of the nice features of the Motion Control Suspension 2WNR strut is that the rebound and compression adjustments are on the top of the unit, so they are easy to access to change settings. These handy labels remind you which way to turn the adjustment knob and to push down on the knob for rebound and pull up on the knob for compression.
One of the nice features of the Motion Control Suspension 2WNR strut is that the rebound and compression adjustments are on the top of the unit, so they are easy to access to change settings. These handy labels remind you which way to turn the adjustment knob and to push down on the knob for rebound and pull up on the knob for compression.

We needed springs to go on our MCS struts, which put us back into debating the perfect spring rate. The choices are as endless as the debate. Again we looked to the Honda Challenge guys who are winning for advice, and they said to go with a 1,000-pound spring rate in the rear and 700 pounds in the front. With that stiff a spring, we won’t even need a front sway bar, which saves weight off of the nose of the car, a nice benefit.

To make these front-wheel-drive machines rotate, a nice stiff rear end keeps the car loose. The numbers on the spring “0800.250.1000” indicate the spring is 8 inches tall, with a 2.5 inch inner diameter and a 1,000-pound spring rate.
To make these front-wheel-drive machines rotate, a nice stiff rear end keeps the car loose. The numbers on the spring “0800.250.1000” indicate the spring is 8 inches tall, with a 2.5 inch inner diameter and a 1,000-pound spring rate.

While we were working on the chassis, we decided to replace our wheel bearings and install some ARP long studs on the hubs. The long studs allow for us to safely add wheel spacers to give ourselves maximum track width for stability while still keeping the 225/45R15 Toyo Proxes RR tires under the fenders per the rules.

 

BRAKES

Next we decided to upgrade the brakes within the class rules, and like the suspension rules, there wasn’t much to work with. The Integra comes stock with a cross system where the left front and right rear brake lines are connected and the right front and left rear lines are connected. This system is a safety design in case of a brake system failure. The problem is that the stock proportioning is biased too much toward the front for racing. The rear brakes aren’t used enough, which is asking the front brakes to do too much of the work.

To fix this issue, we had to reroute the brake lines to separate the front and rear brakes. It wasn’t difficult. We ran the front brakes off the leading line of the master cylinder, split the line with a tee fitting and then went to the front brakes. We ran the rear brakes off the rear line of the master cylinder directly to an adjustable proportioning valve next to the shifter where the driver could reach it while belted. Then we split the line with a tee to the rear brakes. It worked great and is allowed per HC rules.

We rerouted the entire braking system to lose the cross-braking design — left front/right rear and right front/left rear — and went with a front/rear setup with an adjustable proportioning valve from Chase Bays to add more rear brake bias.
We rerouted the entire braking system to lose the cross-braking design — left front/right rear and right front/left rear — and went with a front/rear setup with an adjustable proportioning valve from Chase Bays to add more rear brake bias.
A $5 brass tee fixed our brake line routing issues. The bottom line comes from the master cylinder, then tees to both front brakes, deleting the stock cross system, which was too biased toward the front. We didn’t even have to add brake line. We just shortened the lines, flared them, bent them, and hooked them up to this tee. Easy and cheap.
A $5 brass tee fixed our brake line routing issues. The bottom line comes from the master cylinder, then tees to both front brakes, deleting the stock cross system, which was too biased toward the front. We didn’t even have to add brake line. We just shortened the lines, flared them, bent them, and hooked them up to this tee. Easy and cheap.

We replaced the rotors with a cryogenically treated set and added Carbotech Performance brake pads to the car. We installed steel braided brake hoses and filled the system with Prospeed RS 683 brake fluid to ensure the pedal stays stiff and the fluid doesn’t boil. To keep the front brakes cool, we added heat resistant tubing from I/O Port Racing Supplies routed to the front rotors. Why didn’t we upgrade the calipers? Rules don’t allow it. And honestly the Integra brakes, once upgraded with Carbotech pads, do the job just fine.

In Honda Challenge, the brakes that came on the car are the brakes you are going to race with. Our only upgrade is Carbotech Performance Brake pads — XP10 up front, AX6 in rear — cryogenically treated stock rotors, Prospeed RS683 brake fluid, steel-braided brake hoses, and cooling ducts and hose from I/O Port Racing Supplies.
In Honda Challenge, the brakes that came on the car are the brakes you are going to race with. Our only upgrade is Carbotech Performance Brake pads — XP10 up front, AX6 in rear — cryogenically treated stock rotors, Prospeed RS683 brake fluid, steel-braided brake hoses, and cooling ducts and hose from I/O Port Racing Supplies.
We tested different brake pad compounds on an alternate Acura Integra. In this photo you can see the weight transfer going to the front as the brakes were applied. In the end, we decided to use the Carbotech XP10 compound up front and AX6 in the rear with more pressure going to the rear calipers through the proportioning valve.
We tested different brake pad compounds on an alternate Acura Integra. In this photo you can see the weight transfer going to the front as the brakes were applied. In the end, we decided to use the Carbotech XP10 compound up front and AX6 in the rear with more pressure going to the rear calipers through the proportioning valve.

COMING ALONG

So now our car has a cage, it has brakes, it has springs and struts, but it is still missing an important part: the engine. In our next installment of the Honda Challenge Budget Build, we will detail the work TEM Machine Shop is doing to our B18A1 engine, standalone engine management by AEM, and the rebuild of our transmission by Synchrotech with a tasty limited slip differential.

 

To read more from Rob Krider or to contact him go to www.robkrider.com.

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