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CR-X SiR K24 build from Australia

40K views 78 replies 28 participants last post by  raffaelli 
#1 ·
Hi all from Australia, welcome to my build thread for my CR-X I've been working on for a while now. I used to do track events in my old DC5 Integra Type R, but decided to move back to an earlier model and modify it a bit more extensively. Here's what my Integra looks like:



The car started life as a glass top SiR, but I've since un-picked the original roof and welded in a steel roof. The car was in pretty rough condition when I bought it, so I did a couple of track events, and then decided to give up on the B16A and move to something I was a bit more familiar with that would offer a bit more power. I actually started on the project a couple of years ago, but got distracted by other things and haven't made much progress.

Here's the car as it is now heading to the paint shop:



Planned setup is pretty simple, here's a run down of the main things:

Stock K24A3 (Similar to the K24A2 you get in the US)
K20A oil pump and pan with clockwise motion baffle
RBC intake and ASP 4-1 header
50° VTC
Kpro and E85 (E85 is fairly commonly available in Melbourne where I live)
DC5R transmission (Have freshly rebuilt this with Synchrotech carbon synchros)
Koni Race shocks with GC coilover sleeves, will start with 18kg/mm front rates and 14kg/mm rear
Fresh OEM rubber bushings through, with sphericals in some locations
ASR rear anti-roll bar, OEM front bar
Custom built traction bar
EHPS using a pump from a Holden Astra
Various size 949 Racing 6ULs (8s,9s,10s)

The goal is to make a nice street registered car that I can do plenty of track events in without issues, and run a bit quicker times than my Integra. More updates to follow.
 
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#68 ·
Sorry for the lack of updates, busy month and a bit, but a few things have been happening on the CR-X.

In the lead up to World Time Attack I decided to tackle a handful smaller jobs that I'd been putting off. Budget and time constraints meant no major upgrades for this years event, but there was still time to refurbish the front end and correct a couple of other issues. I find reliability is essential for a fun weekend at the track.

I had a spare set of CR-X SiR front knuckles sent to me by a Japanese gentleman, after having no luck sourcing any locally. Despite me only wanting the knuckles, the kind fellow carefully packed up the whole front suspension bar the shocks and springs, so I've got spares of everything now. As a bonus these front knuckles are from an ABS model complete with sensors, useful for a traction control system if this build escalates that far!



To freshen up the knuckles I'd ordered a bunch of parts, including OEM hubs, bearings, lower ball joints, ARP extended studs and a set of Hawk DTC60 pads.

The previous pads still had plenty of life left, but with the single piston sliding calipers the pads always get tapered wear. Even slight pad taper with the dinky little stock calipers results in a long pedal lacking confidence, and a fresh set of pads and discs before heading to a high speed track like Sydney Motorsport Park is cheap insurance against brake issues.



I gave the knuckles a coat of paint, and pressed the ARP studs into the hubs. Then I got the knuckles all assembled, taking great care to preserve my fresh paint job since no-one's got time for a 48 hour cure time.



Front knuckles installed in the car, with the correct quantity of spacers beneath the tie rod end on our tie rod end kit to correct the bumps steer, as I measured last time I was working on the car.



The front tow hooks would have to make way for the splitter brackets, so I added a tab on the forward face of my "traction bar" to allow me to bolt on a tow strap that found in the corner of the workshop. I don't remember buying it, but that's not the first time that's happened.



While I had the TIG fired up I welded the hexes on to my radius rods for easier caster adjustment without having to resort to vice grips. They copped a fresh coat of paint while I was there. Once I stop cutting and welding things in the front suspension, if ever, I'll pull it all off again and get it powdercoated.





With all that boring stuff done I moved on to the most exciting job on the list; fitting up the new OEM hatch struts I'd acquired at great expense. My days of getting hit in the head with the hatch are over.



Last on the list I constructed a splitter to suit the earlier manufactured brackets. This is just Version 1, but the blade is 6mm marine ply, with a doubled up section along the forward edge and some 40x25mm aluminium channels added for transverse stiffness. The end result is quite lightweight, and while I wouldn't call it quick release, it's an easy process to get it on the car, just requiring some contortion and patience.



Next update I'll give a bit of a run down of the WTAC event.
 
#69 ·
World Time Attack

After doing all the work in the previous post I had a good nights sleep then headed up to Sydney for World Time Attack. I gave the car a wash before we hit the road, it's pretty photogenic when the bonnet is not in the picture:



The drive up was about as enjoyable you'd expect in a car with a 3" exhaust and no interior, but it was uneventful and we made it to Sydney in time to get rejected by security at the gate to Sydney Motorsport Park, since they didn't get the memo about letting competitors park up the night before. No big deal though, I just headed to the apartment where we were staying and parked there. Can't imagine what all the other guys that trailered their cars there did, since Sydney roads are a nightmare.



Thursday

WTAC is a 3 day event for most, with a dedicated practice day on the Thursday, with plenty of time on track since half the competitors are usually elsewhere fixing their cars or doing whatever it is that non-Honda drivers do.



The first session was spent bedding in the brakes and getting familiar with SMSP again, it went well and the car seemed to be more stable than last year with the newly fitted front splitter. In the second session I was just starting to get up to pace, then after heading through pit lane for a quick check of tyre pressures, gave it a bit too much throttle re-entering the track and the resulting wheel hop popped the slip join apart in the exhaust which meant a missed session while I fixed that.



Finally in the last session I'd built up a bit of confidence in the car, and nothing had fallen off in the previous session, so started to push a bit harder which resulted in the fastest lap of the day of a 1:49.6. This was already 5 tenths quicker than last years best time and a promising early result.

Friday



Friday is the first day of the main public event, the pits are noticeably busier with the addition of all the spectators in their flat brimmed hats and fake Takata or Bride backpacks. I knew that the morning session was going to be our best opportunity to set a good time with temperatures warming up compared to the day before. I managed to improve in a couple of areas, getting down to a 1:48.9.

The afternoon sessions were marred by other competitors with either poor situational awareness, mechanical issues, or impacts with solid track side items, so I just focused on improving in sections of the track where I could, particularly the high speed T1 to T2 section, and staying out of trouble everywhere else.

Then it was beer time:



Saturday

I took it pretty easy in the first session just wanting to get back up to speed after maybe a few too many beers the night before. In the second session I went out at the rear of the pack, ran a lap to search for some space on track, but running into plenty of traffic I came in to the pits to wait for some clear track. The strategy worked well, and I was able time it so I exited the pits with nothing but open track in front of me bar one back marker that I managed to sneak past without losing a lot of time. With a clear run at it I managed to put together the best lap of the event a 1:47.7. 2.5 seconds faster than last year with basically no performance upgrades to the car, bar the splitter, on the same beaten up set of AD08R so I was pretty happy with that.



Our goal for next year will be to take another 3 seconds off and run a 1:44.X lap. For reference the winner of my class in an EK Civic with a Rotrex'ed K24 on 295/225 tyres put down a 1:39 lap time, so I've still got a way to go, but I'm in reach of being the fastest naturally aspirated car in class.


2015 vs 2016 Best Lap Comparison

Below is a comparison of the data from the fastest laps of 2015 and 2016. Click the image to get the full size graph.





Looking at the data comparison, there's a few things I've noticed:

- T1 minimum speed is up 10km/h to 175 km/h and the braking point has been pushed back 25m to beyond the 100m mark, though there's definitely gains to be made in the braking zone here by braking a little later and trailing the brakes further into the corner.

- The exit and run through T2 to T3 was better this year, picking up nearly 10 km/h before braking into T5. I chose to short shift to 4th and focus on positioning the car as far to left of track at the exit of 2 as possible to improve the line through T4. Mid corner speeds through T4 and T5 are improved, but the exit from T5 isn't much better probably due to running out on to the south circuit pit exit and unsettling the car.

- Speed over corporate hill (T14) has improved, and a bit more bravery at T16 has resulted in better speed there.

Track map for reference:

 
#70 ·
World Time Attack
Thanks charger, for that very interesting track weekend report :)!

Then it was beer time:
Wow, you have German beer from Munich (also known as München or MUC), where I lived over 9 years during my studies and research work. The origin label is Hobräuhaus München, what was the label on that bear mug you had?

With a clear run at it I managed to put together the best lap of the event a 1:47.7. 2.5 seconds faster than last year...take another 3 seconds off...but I'm in reach of being the fastest naturally aspirated car in class
Very attractive goal man :D! Did you already analyze in datalog's, driving method/style, tires, or any other part of the race car system or harmonization of parts should be pushed to reach your goal?

Anyway, exciting and challenging things here...I am looking forward to see your next steps.

Markus
 
#72 ·
Another belated update. Late last year I packed a change of clothes and my toothbrush into the CR-X again and headed 700km across the state border to Wakefield Park circuit in New South Wales. NSW has a bunch of excellent circuits, and Wakefield is a great little track. It's built into the side of a hill with quite a lot of elevation change, and has a compact but flowing layout.

No time for any changes on the CR-X since WTAC bar some fluid changes and a quick wash to remove 2000km worth of dead bugs.

After a quiet drive up, the track day dawned with cool but sunny and conditions. Perfect for some quick lap times. There were only 25 drivers at the event, which guaranteed heaps of track time. I skipped the first session to help out running the event, and made use of the spare time to bolt on the aero bits and give the car a brief check over before heading out for the 2nd session.



Within a couple of laps I dropped down into the 1:08s, improving from a 1:09.0 best lap at the same event last year. A great start to the day, but it was clear there was more in it. Maybe the front splitter made all the difference, but to be brutally honest I'm only now becoming comfortable in the car, and more familiar with the power and handling. So the I'd put the bulk of the improvement down to the imperfect device between the seat and the steering wheel.



The CR-X is fitted with small 205 width front tyres so I can't do more than one or two fast laps before the tyres overheat and understeer becomes terminal. So my strategy is to go out and complete one warm up lap and then go straight into flying laps





Putting it all together I laid down a 1:07.7 lap, an improvement of more than a second since my last time at the track, and 1:06s are in reach. To put it in perspective the top 3 places in the Neova Challenge earlier in the month were all within the low 1:05s, and 2 of those cars ended up in the top 3 at World Time Attack.

Here's a video of an earlier untidy 1:08.5 lap, unfortunately no footage of my best lap. There's plenty of work to do on my driving, watching this video back I can see that my transition from braking to turn in needs work, and in general my steering inputs are messy.



Overall it was a great day, and it was good to dip into the 1:07s. With every event I'm getting closer to the cars potential, and I feel like I'm starting to improve a bit as a driver.

Below is a speed trace and min/max speeds for my best lap, and track map for reference.





Click it for the full size:



Unfortunately I don't have any good data from my last visit to Wakefield, but there is a couple of points for me to remember for next time:

- I'd be better off bouncing off the limiter in 5th at the end of the start finish straight rather than shifting to 6th, as my max speed of 180km/h is still just before the rev limiter in 5th
- When comparing to other laps I can negotiate T9 with a later and shorter lift off the throttle and maintain better mid corner speed and speed down the following short straight, which should be worth a few tenths
- As usual, I still think the car needs more tyre. It might be a bandaid to correct an issue that could be improved with suspension setup, but I've always fundamentally believed that staggered tyres on FWD is the right way to do it.
- I'm starting to get more comfortable with the brakes, but I'm still finding that the pedal feel is not as progressive as I'd like resulting in some locked tyres. We're developing a brake booster delete kit with correct pedal ratio and master cylinder diameter designed for track use not hard-parking and I'll be setting it up on my car soon, which should greatly improve feel under brakes.
- My shifting is a bit slow and clunky, I think I need to tweak the throw of the clutch pedal, and I'd like to make a spacer plate to re-position the shifter a bit
 
#73 · (Edited)
A few weeks after the Wakefield event I headed up to Winton to see if I could crack that elusive 1:35 lap time. 1:35 isn't all that fast, about what a pro will do in a 997 GT3, but it's not bad for an old hatchback. The changes since last time at Winton were:

- Front end refurbish including hubs, bearings, lower ball joints, Hawk DTC60 pads and discs
- Front splitter
- Rev limit increased to 7,800RPM

Conditions were good, with a top of 19°C and a bit of cloud cover to keep track temperatures cool. After spending most of the morning helping out the guys running the event, then stuffing about fitting my splitter I headed out for a few laps.



Out of the 7 laps I did, the best for the day was a 1:37.2750, about a second off my best pace here. As always I've got a ready supply of excuses though: Without being balked I would have been comfortably into the 36s, and if I can drive the first half of the track as well as I had in the past the 35 second range should be within reach.

Here's a video of the best lap, watch to the end to see R33 Skyline skids.



Unfortunately no data this time due to GPS problems, but comparing the sector split times from this event and my previous best a couple

- Holding 5th gear on the front straight is consistently worth 3 to 4 tenths improvement in lap time, part of which is better entry to the S as with less shifting I've got more time to focus on braking and turn in.
- The tyres may be past their best. The mid corner and exit understeer was noticeably worse this time out. At the next event I'm going to increase the rear anti-roll bar stiffness from it's current softest setting.
- Even with the increased rev limit I'm still running out of revs so I will be further increasing the rev limit to 8000RPM before my next event at Winton and crossing my fingers that it holds together.

The car will get a short holiday now to fix and tweak a bunch of things before this years events get underway. Also doing a bit of work on my ex-daily driver EF2 so I can do some track events in that:

 
#76 ·
Now I'm up to the stuff I'm actually working on now. As I complained about in an earlier updated, I've never been happy with the brake pedal feel in the car. It doesn't feel progressive with plenty of flat spots on my tyres as a testament. I'm not a great driver, but surely not that bad and I haven't had this issue in my other cars.

So it's time to attempt to fix the issue before I run out of tyre. I've decided to remove the brake booster using a prototype of a kit we're making. Here's the basic shape of the idea: an adapter plate, finished in a fetching anodised satin black to match the rest of the engine bay scenery, plus the pushrod and master cylinder:



The master cylinder I'll use is a 13/16" from an ED6 Civic hatch, replacing the original CR-X SiR 15/16". The 13/16" diameter should hopefully give a good balance of pedal feel and travel with the smaller 262mm braking package on the CR-X, and it was something I had lying around anyway. I did a similar brake package on a friend's Toyota Starlet with a 7/8" master and the pedal was just a little too firm for my taste.

First up I removed the original master cylinder, booster and brake pedal and in the case of the master and booster, relegated them to the bin. Then I needed to grind out a small area of the firewall to give clearance for the bit that protrudes out of the back face of the master cylinder:



Next task was to drill a new hole in the pedal to correct the pedal ratio. The new hole is gives a pedal ratio of 6:1, whereas the stock pedal measures out at about 4:1.



With everything suitably drilled, ground and hammered it was time to start reinstalling everything. First up the booster delete plate itself, with some studs that I scrounged up fitted to it to make the install a bit easier than using bolts. I guess as easy as working on anything under the dash of a CR-X is ever going to be.



Then master cylinder, pedal and pushrod in:



Then I made some new hoses to connect to the proportioning valve, I'm still using the stock prop valve relocated to the firewall out of the way of the motor. Created some templates for the hoses using some filler rod, and got all the tools I'd need together:



After a bit of cutting, flaring and bending here's the finished result. I'm getting less bad at making these things. After a few more revisions I'll attempt re-making the hoses to the rear brakes to get rid of the ugly joins in the engine bay.



Then all that remained then was to fit up the hoses, fill up the reservoir with some Motul RBF600 and give the brakes a quick bleed.



Will report back with on track impressions as soon as I can, but on the street it feels good. Still plenty of stopping power at moderate pedal effort, but feels a lot easier to modulate.
 
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