Truenotch's-Old-Man's MX5 - MX5RacingNZ

[Truenotch]

I've been back in this thing for the last 3 rounds of Winter racing at Manfeild. The competition has really heated up! The current top guys have been doing 1:23's and the new lap record is a 1:23.3 - that's over a second faster than my previous lap record! 

We're running on the new Toyo R888R tyres and they appear to be a lot faster. Most cars have had their engines refreshed too. 

I jumped in for round one and went ok, but the car didn't feel right. It was pushy in the mid corner. Turns out the left front shock was toast! 

Despite that I still managed to get down into the low 1:25's and was mid pack. We've had a decent turnout this year, with 13 cars at each round so far. 

Bit of footage: 

 

[Truenotch]

Because of that it got brand new suspension for round 2. We had to replace the springs too as the previous setup wasn't going to work with the new Bilsteins and the desired ride height. That left the question of spring rates. 

I prefer my car to be a bit harder in the rear than most, so am running 400lb in the rear and we chose the same spring rate as everyone else for the front - 550lb. 

Looks good with a bit more slam: 

Got it to the race meeting and had a bit of action: 

This one was totally my fault. It's been a while and I'm a bit rusty - didn't expect Derek to be in my blind spot. 

Jumped for 6th to 2nd at the start of this race, but didn't finish there. Good close racing though! 

The car felt much better than the previous round, but still not completely right. It felt too soft and roley in the front, so my theory was to go harder in the front. A bit of research showed that the Spec Miata class in the USA runs 700lb in the front and the same tyres as us. So we landed on 670lb as a rate to test (12kg). 

[Truenotch]

Round 3 took place on August 6th and the new spring rates were proving to be working! I qualified a second faster than any lap from Round 1 or Round 2 with a 1:24.3 which put me in 4th - not bad. The front two guys qualified at a blistering 1:23.3 and 1:23.5! Madness. 

Race 1 came around it was GREASY. I started 4th and jumped up to 2nd on the start but ended up slipping back to 5th after running wide and getting wheel spin on the exit of the last corner. Not to worry though, two people fell of ahead of me so I still came home in 3rd. 

Spin: 

Full race: 

I also managed to stuff up when trying to record the other two races... So this is the only race on camera. 

 

So the setup is getting better! I'm planning to run my AE86 at the next round, so probably won't be campaigning the MX5 at the final. 

[Truenotch]

And a few pics from Round 3: 

[Truenotch]

I gave the MX5 a rest for Round 4 of the winter series so I could blow up the AE86's engine instead... So the next outing was at the New Zealand Grand Prix in February. 

Here's a quick clip of some action - I'm in #105 with the racing stripes. 

 

I'd managed to qualify well in greasy conditions and achieved P2. Unfortunately, the track was dry by the start of Race 1 and a few of the others managed to pass me, so I ended up 5th. 

The rest of the weekend ran along the same lines. 4th in race 2 and 5th in race 3 in the rain... 

 

Now, remember, a poor craftsman always blames his tools.... So.... 

It was definitely the car's fault. 

Here's the incar from race 1. You can see the difference in straight line pace, but I was also unhappy with the handling. 

 

[Truenotch]

The quick guys were beating my lap times by roughly 1 second in all of the dry races, so there's definitely work to do on the car. The top 4 have all had their engines refreshed, so our car is the quickest of the original-motor crew... So the logical thing would be to  get the engine rebuilt, right? 

 

WRONG 

 

It would be far more satisfying to catch them without doing the engine... I think... So we had to make a list of things to improve. 

The clutch is starting to slip, so that's due to be replaced. 

Next: inspect engine mounts. They were really bad! And wouldn't be helping the situation. 

Next up - cold air! Dad's added a bit of length to the filter pipe and made a box around the filter. 

Next - exhaust ports. They were pretty daggy! 

After: 

 

Next up: suspension..... 

 

[Truenotch]

I'd noticed that the rear suspension was bottoming out when hitting small bumps while under load and there were NO BUMP STOPS at all, so it was a pretty harsh feeling to reach full travel. This was a new phenomenon since installing the Bilsteins... Further research was required! 

I dug out the old KYB's and a couple of standard shocks (same length as the Bilsteins). That might explain the lack of rear travel! 

The KYB's are about 35mm shorter in the body and even shorter in the shaft. 

After a bit of research it also turns out that the Bilsteins have a HUGE amount of rebound damping compared to bump. This causes the shocks to "jack down" or "ratchet down" as the load increases because the rebound force over powers the compression force. I got in touch with Anthony at Alignment Specialists in Penrose to see if he could shorten the bodies of the bilsteins and re-valve them to suit the new heavier spring rates. He was happy to help, so I dropped the shocks off to be modded. 

More research outlined that droop travel is another key part of the suspension on MX5's - especially when bouncing off ripple strips or hitting tight cambered corners. I ran the shocks through their travel with no springs to find the perfect lengths. This ended up being around 20mm shorter bodies in the rear and 10mm shorter in the front.

These measurements took another important component into account - bump stops. 

These are fancy 300lb bump stops from 5Xracing in the USA. They are supposed to be the bees weasles and can be a very important aspect of racecar suspension. 

The next item on the list was helper springs. These are commonly used in the USA and can make a big difference when the suspension is unloaded / when doing jumps. Obviously it's important to do jumps! So I found a set of 70lb keepers to try. In the states they use 150lb but I couldn't find any for a reasonable price in NZ. 

The springs had also never located onto the tophats properly, so I had my friend Jonathon from Kinex 3D print a few locators to knock into the tophats:
 

A new issue became apparent when reinstalling the springs... The keeper springs pack down to a height of 20mm, meaning the shock would be 20mm taller than it used to be... And there wasn't enough thread left to wind the shocks down. 

Enter new component number 43512: 

\

6" springs front and rear. 650lb front (12kg) and 400lb rear (7.2kg). 

Assembled: 

You can see how stubby the rears are in this pic. They're so cute! 

Front installed: 

Rear installed: 

There's a decent bit of travel left too: 

 

[Truenotch]

Round 1 of the Winter Series complete. We had a decent turnout, with 12 cars on the grid. 

The changes seem to have worked! The car felt great in testing and I was on the pace with the top guys again. Feelsgoodman.jpg 

Race 1: Started P3 and managed to pluck off the two cars in front. Made a pass for the lead on the last lap and it wasn't settled until after the last corner. Great race and stoked to get a win! 

Race 2: Reverse grid, so I was off the back. Pushed hard through traffic throughout the race and ended up in 3rd. 

Race 3: Handicap - started last and had a great race. Made it to up to second place, but couldn't quite challenge for the lead. 

I also had the quickest lap of the weekend with a 1:24.623... The next fastest was a 1:24.739 so there's not much in it! I'm pretty impressed with the lap times considering the track was ice cold all day. 

 

Here's a couple of pics: 

[Truenotch]

I forgot my camera, so borrowed a Gopro for the weekend. I definitely prefer my sony! The angle wasn't great and it's a bit wobbly, but you get the idea .

Camera didn't work for Race 1 (gutted), but here's race two from the back of the grid: 

 

[Truenotch]

A few more pics have popped up. This was just after passing the pink car. He's had the best pace for the last couple of seasons, so making the pass is a good achievement in itself  . 

And this one is the last corner of race 1 - I'd passed Bryce on the back straight, then he fought back in the last corner and I crossed the line 1/100 of a second in front. 

 

[Truenotch]

Race 3 - handicap. Started last and 20 odd seconds behind the lead cars. Finished 2nd. 

 

[Truenotch]

This video is from Scott's car during race 2. He had a prime view of the multi-lap battle between Tim and I. 

 

[Truenotch]

A bit of a teaser from Round 2. Bump drafting is fun! 

 

[Truenotch]

Round 2 went well again, starting with a P2 in qualifying behind Bryce in the green #22. It rained overnight, so the track was greasy which posed a bit of a challenge in some corners. 

Race 1 was awesome fun! We had a great tussle in the front group and I managed to hold on for second place. Another half a lap and I could have had him! 

 

Race two was busy! I started from near the back of the grid (reverse grid race) and managed to make my way up the order, eventually making it to the front for a win! 

And the Race 3 handicap was pretty hard to overcome... The four of us were given a pretty huge gap to try and close! We didn't make it, but that doesn't mean it was a bad race. We had a great battle for most of the 6 laps. 

 

So that all boiled down to a very close finish for the round overall! I ended up with 187 points, giving me the win for the round above Bryce, who reached 184 points.

 

Two rounds to go! 

 

[Truenotch]

Round 3 was another action packed weekend! 

I qualified second, so started on P2 in the first race. I had no answer for Bryce who'd started on pole. He made a gap and held it for the whole race. 

Race 2 was a bit more interesting. I started from 10th place as it was a reverse grid. Managed to make a good run through the traffic and ended up finishing in 1st! It was a great battle with Bryce all the way to the finish. 

 

Race 3 was intense! Bryce and I started from the last 2 grid spots. It was a handicap race and we started with a considerable gap to make up. On the last lap we were catching a bunch - I made a move down the inside and got a good run down the straight. It was anyone's game right until the last corner. I chose the low line behind Scott's dark green MX5 and Bryce went high. Unfortunately Scott had a slow run through the corner, which allowed Bryce and Tim to leapfrog past me... End result, I finished 6th and Bryce finished 3rd to extend his championship lead. 

So that's another round done and dusted. On to Round 4! 

[Truenotch]

The final round was another cracker! We had changeable weather conditions which left everyone guessing about what to do with their setup. 

I qualified P2 again behind Bryce. We had an epic battle for the full 6 laps in Race 1 and I managed to come away with the win (just). This was a really fun race! 

 

The reverse grid in Race 2 was trickier for me. I started from last place and Bryce made a few early moves to put a gap between us. I made my way up to second, but wasn't able to catch him. 

 

Race 3 was WET. Jeremy Hoskins lent me a set of brand new tyres to cope with the conditions and the car was handling well, but I couldn't do better than second. Visibility was very limited during this race! 

 

So that's the series done for 2018. I ended up in second place for the series, 35 points behind Bryce in #22. The racing was close, clean and fun all season long, and proves that MX5 racing is still a super fun and affordable way to get your motorsport fix . 

 

[Truenotch]

I took this car out for a race weekend back in September and had a goal in mind of winning an MX5 race. The car was quick and I managed to put it qualify in P2 for the first race. 

Bryce managed to get a good jump from the start and went from 3rd to 1st during the first lap. He pulled a bit of a gap, so I stuck my head down and chipped away at him for a few laps. The last couple of laps were good - I managed to get ahead of him and we were battling right up to the last corner. We crossed the line side-by-side and he won by a nose. 

Race 2 is reverse grid and it was busy as always! I got caught behind a slower car at the start and had to catch the other fast guys through traffic. Bryce and Matt pulled ahead and were battling hard all the way until the last corner.... When Matt overcooked it a bit, caught the grass on the inside and ended up spearing off the outside of the track into the tyres! This promoted be to another 2nd place finish. 

For race 3 I was set to start in P2 again and it was my last chance to get a win for the weekend. Unfortunately the car didn't make it to the start line because the diff let go! This was the original diff and we'd never opened it up. So it had lived a full life on the road (140,000ks or so) and has had 10 years of track abuse before letting go. It was a bit disappointing not to compete in the last race, but the weekend was still good fun! 

I whipped the diff out the next day and Dad pulled it apart. 

 

Yep, she's chooched! 

It's now been rebuilt by the local gearbox shop along with a solid spacer kit to get rid of the crush tube. I think the crush tube had squashed after 10 years of limiter launches . 

 

Oh yeah, we also fitted a window net to comply with the Mazda Racing Series rules for our summer racing: 

 

 

[Vintage Grumble]

Window net, but no roof? Wat? Puhuhuhu

[anglia4]

Whats it cost you to run a season roughly??

[M.H.]

Are they faster with the roof on?