Mx5, Chapter 2

[Daffy]

This must be close to sitting on the bump stop?

Great shot! I’ve saved this one

[The American]

[The American]

It’s been a long time with little to report for the White Mouse, but there may be a little bit of excitement on the horizon.

1. 18-20 May - Oakey Street Sprints. This is the one street sprint venue that I have not participated in. The event required ‘Racers’ licence which I did not have and a HANS device (although, they have moderated the HANS requirement so that only those with a very swift time require one). This event is a sprint, but also incorporates a ‘go-to-whoa’ and some cash prizes. Like Gatton (was), Wondai and Pittsworth, this event is set out in an industrial estate.
2. 14 July - Gold Rush Hill Sprint. The Central Queensland Motorsport Club are running a brand new Hillclimb on a section of the Burnett Highway between Bouldercombe and Mount Morgan (south west of Rockhampton). The track is set on about 2km of the highway that winds its way up the range towards Mt Morgan. Entries are capped at 100, and there are already another 40 names on the reserve list from the EOI. The google street view perspective makes this one look rather awesome.
3. 1-2 September, Gunnedah. There are two events in September that I’ve got an EOI in for. The first (Saturday) is an 800m runway sprint that replaces the Snowy Mountains 1000m. I don’t have anywhere near the HP required to be competitive, but it will be an experience! The second (Sunday) is a Hillclimb run on Mt Porcupine near the township of Gunnedah.

[The American]

The 2018 Oakey Street Sprints was a mixed bag. Allsorts, Jaffas, bananas and at least one jelly snake.



I didn't do this event last year because they required a HANS device, and I didn't have one yet. I do now, and they had changed the rules to require any driver to use a HANS if their times for the two-lap format were under 1:30 - so that was my target time. On my third last run of the second day, I managed a 1:29, and then a 1:27 on my second last run:



My last run of the day didn't go to plan...



I made two mistakes.
(1) I missed my braking point by miles. Pure error on my part. By the time I had realised, it was too late and the best I could manage was to get as close to the gap in the track side barriers as I could, and I didn't quite make it. I have watched the clip a stack of times, and I still wonder if I could have dríven through it somehow - it felt like I was going so slowly by the time I understeered into the tyre barrier.
(2) I am pretty sure I had pushed well beyond thermal capacity of the brakes in the car. This corner was at the end of the 5th braking zone, and I had pushed the brakes to the limit in the previous 4 zones, and had been on the limiter in 4th (3.63 diff and 6 speed - someone will tell me how quick that was) twice already in the run. The pedal was firm, and I was pushing them hard, but I couldn't even trigger the ABS - it felt like brake fade, and I felt like I was steering a billy cart down a steep hill.

Fortunately (for me!) another driver had also come off in the same spot when a steering arm failed. He had cleared out a significant stretch of chainlink fencing and poles that I would have hit, had he not cleaned them up first. The results of all these mistakes? A rather scuffed up White Mouse.



My oil cooler took a hit and broke free. Although it didn't rupture, I could not secure it, and was not able to patch up for a final run or two. I have yet to decide if the oil cooler will reappear in the front corner.

On the upside, I picked up first place in my class, 5th in the 'Street Car Challenge' and 21st overall for the event, and I came home with the sub 1:30 I was looking for.

The Noosa Hillclimb is 9th and 10th of June and things are looking good to have the necessary repairs done in time.

[Custardtart]

That should polish out ok!
I’m going to do the Summer Noosa Hillclimb as I’m off to Lakeside on the 10th June.

[The American]

Sunday afternoon two weeks ago:



Saturday 26 May

I collected panels and parts from Automotive Plus, and stopped for a quick road rescue on the way home:



The oil cooler has seen better days...



Torn down, there was no structural damage except for some annoying tweaks from the when the front wheel drove over the oil cooler and pulled on a few things.




By Sunday afternoon:



Today's effort saw it all buttoned back up (it will have to come apart again for paint):



The Winmax W3 brake pads in the front have been swapped out for W6.5s (broader and higher heat range, and higher torque capacity), the brakes have been bled, the engine oil changed and filter inspected and replaced. Ready for Noosa!

[Magpie]

The Winmax W3 brake pads in the front have been swapped out for W6.5s (broader and higher heat range, and higher torque capacity), the brakes have been bled, the engine oil changed and filter inspected and replaced. Ready for Noosa!

You will enjoy these pads!

[Daffy]

Excellent work

[greenMachine]

The oil cooler has seen better days...

Curious what you did/planning to do for the oil cooler?

I am about to start on a radiator mounted cooler for mine, having decided that the guard doesn't have enough room for a track-oriented turbo-sized cooler ...



PS - I reckon you should send a photo of that to Setrab with a letter of thanks for building them strong!

[The American]

You will enjoy these pads![/quote]

They are pretty good. Bedded them in this afternoon - took a little to warm up, but once they had some heat in them , they were very impressive! They provide the greatest stopping power I’ve ever had in a car.

[The American]

The oil cooler has seen better days...

Curious what you did/planning to do for the oil cooler?

I am about to start on a radiator mounted cooler for mine, having decided that the guard doesn't have enough room for a track-oriented turbo-sized cooler ...



PS - I reckon you should send a photo of that to Setrab with a letter of thanks for building them strong!

Hi Green Machine!
At this stage I think I will install a larger cooler where the a/c fan attaches to the radiatior. Setrab makes fan packs for some of their cooler sizes. I’m looking at whether a cooler and pack will fit between the cold side intake piping and the radiator. Clearance to the anti roll bar may also be an issue to work around.

It’s clearly very tough. As is the Speed Flow hose and fittings. Not a drop of oil spilled.

[greenMachine]

I looked at the fan packs. IIRC they need 100mm depth, 50 for the cooler, and 50 for the fan - not enough room on mine!

However if you mount it behind the rad, and seal the edges, you shouldn't need any more help to get a good airflow, assuming you have sealed the radiator ducting. On Dann's recommendation I am going to run a PWR 5931K.

[The American]

I changed a few things after the Oakey event.

The brake pads which I believe suffered fade at the Oakey event were Winmax w3. W3 are semi-metallic pad with a working range of 0 – 600degC which means they work nicely from cold and continue working after a regular street pad would fade. They have a 0.34 – 0.37 coefficient of friction rating. At the Oakey event, on day two I was hitting the rev limiter in 4th gear/160km/h a few times in each run, and I think this was simply too much for these pads at the front.

The W6.5 has a temp range rating of 50 – 800degC and a friction rating of 0.47 – 0.50. The first use when cold is not impressive, but after that they work incredibly well (I have no other race pad experience to compare however).

They wash off speed very quickly and will take some getting used to - I need to reset my sense of braking effort and distance. At the Noosa Hillclimb, I think I was over-braking and carrying less speed in corners.

The other thing I changed was the front and rear spring rates. The car needed a wheel alignment after the ‘off’ at Oakey, and so I decided to swap in the 10kg front springs I had and move the front 6kg springs to the back and then align to suit. The consequence of this: The car gained about 20mm at the front with the spring perches at their lowest point, and what had been 4 degrees of static camber became 3. I’m not happy with the new height or the resulting alignment numbers and so another change is coming.

These changes have prompted the beginning of a new learning curve with suspension.

Firstly, after swapping in the much stiffer 10kg front springs, at the Noosa Hillclimb the suspension felt SOFTER! If the car slid, it let go slowly, when turning in or braking hard it seemed to take longer than normal to take a ‘set’ or didn’t feel like it took a set at all. How could this be? The symptoms are what I would expect from a softer set up, but the spring rates are much higher.

The only idea I have so far is that I’ve been relying heavily on the bump stops under the soft springs, and I’ve become accustomed to laying the car on to them in hard corners and brake applications. I chatted with Josh at (**Spoiler alert**) MCA suspension, and he suggested that with R-compound tyres and 6kg front springs, I was probably spending a lot of time on the bump stops.

I don’t know what the effective spring rate of the bump stops is, but my guess is it will be a steep rising rate when reached, and probably much higher than the new springs. The new springs and slightly higher ride height have kept the car off the bump stops, resulting in a ‘softer’ effective rate.

I can’t think of another reason why the higher spring rates would feel so much softer. Ideas?

At the Noosa Hillclimb I was consistent, but consistently slower than past efforts. Five 69 second runs, a 71 and a 68.8. Compared to my PB of 65.15 - miles off. A combination of the changes made to the car, being unfamiliar with how the car handled with the changes, and being spooked after stacking it at Oakey, probably all contributed to my times being off. I didn’t think I had placed in my class, but another competitor contacted me a week later to point out that I may have…



The next planned event is the Gold Rush Hill Sprint in July at Mt Morgan. It’s 2000 meters of winding bitumen highway. Between now and then I will make some changes to get the car back to its previous height, realigned and hopefully spend some time driving it around.

Two years ago at the Noosa Hillclimb I chatted with the builder of this car:



It is based on a RIOT kit car and houses the remains of his Mitsubishi GSR Lancer including 4g63 and 4wd system. Interestingly, it also runs solely on natural gas.

He told me he was working on producing a kit car that would receive mechanicals from a donor Hyundai Getz. This year he brought it along to display. It is a GTZ which is a play on Getz but without the ‘E’xtra stuff.




It is really small and basic, and weighs about 550kg. Gauges, steering column and rack, engine, computer, exhaust brakes – it is all Hyundai gear and mostly from the donor Getz. The engine is rear mounted, but facing the same way that it is in the FWD configuration, which is how rear drive is achieved. It’s really quite a neat little creation, and it is road registerable.

[greenMachine]

I changed a few things after the Oakey event.

The other thing I changed was the front and rear spring rates. ... I decided to swap in the 10kg front springs I had and move the front 6kg springs to the back and then align to suit. The consequence of this: The car gained about 20mm at the front with the spring perches at their lowest point, and what had been 4 degrees of static camber became 3. I’m not happy with the new height or the resulting alignment numbers and so another change is coming.

These changes have prompted the beginning of a new learning curve with suspension.

Firstly, after swapping in the much stiffer 10kg front springs, at the Noosa Hillclimb the suspension felt SOFTER! If the car slid, it let go slowly, when turning in or braking hard it seemed to take longer than normal to take a ‘set’ or didn’t feel like it took a set at all. How could this be? The symptoms are what I would expect from a softer set up, but the spring rates are much higher.

The only idea I have so far is that I’ve been relying heavily on the bump stops under the soft springs, and I’ve become accustomed to laying the car on to them in hard corners and brake applications. I chatted with Josh at (**Spoiler alert**) MCA suspension, and he suggested that with R-compound tyres and 6kg front springs, I was probably spending a lot of time on the bump stops.

I don’t know what the effective spring rate of the bump stops is, but my guess is it will be a steep rising rate when reached, and probably much higher than the new springs. The new springs and slightly higher ride height have kept the car off the bump stops, resulting in a ‘softer’ effective rate.

I can’t think of another reason why the higher spring rates would feel so much softer. Ideas?

First, what are the 10kg springs length - sounds like yours are too long. If you are running helpers, try taking the helpers out. Otherwise you need new springs, maybe same rate but just shorter. My suggestion would be to calculate how much shorter (under load) they need to be with the perch where it is, add in however much you want to raise the perch, then add in however much the (say) 500kg they are carrying at 250/side has compressed them - that should allow you to calculate the free length. Don't forget to adjust for the motion ratio, and make sure you will have enough compression in them to avoid binding under bump. Or just ask MCA? You might want to check out the rears too, I don't know if a front spring will always fit a rear shock. Fix the springs, fix the alignment, and see how it handles then.

What do your bump stops look like - if they look shagged they probably are, and that might mean they have been heavily used. They aren't meant to be part of the 'normal' suspension, and they will add dramatically to your spring rate, so I wouldn't be too surprised at what you describe. You shouldn't be so high you never use them, but you shouldn't be riding them either when cornering on a smooth track. If you want to check what is happening down there, use a cable tie on the shaft to show how far it is travelling under bump.

[The American]

First, what are the 10kg springs length - sounds like yours are too long. If you are running helpers, try taking the helpers out. Otherwise you need new springs, maybe same rate but just shorter. My suggestion would be to calculate how much shorter (under load) they need to be with the perch where it is, add in however much you want to raise the perch, then add in however much the (say) 500kg they are carrying at 250/side has compressed them - that should allow you to calculate the free length. Don't forget to adjust for the motion ratio, and make sure you will have enough compression in them to avoid binding under bump. Or just ask MCA? You might want to check out the rears too, I don't know if a front spring will always fit a rear shock. Fix the springs, fix the alignment, and see how it handles then.

What do your bump stops look like - if they look shagged they probably are, and that might mean they have been heavily used. They aren't meant to be part of the 'normal' suspension, and they will add dramatically to your spring rate, so I wouldn't be too surprised at what you describe. You shouldn't be so high you never use them, but you shouldn't be riding them either when cornering on a smooth track. If you want to check what is happening down there, use a cable tie on the shaft to show how far it is travelling under bump.

The 10kg springs have 200mm free length, which is the same as the 6kg that came out. I had worked out that I'd need either 175mm or 150mm free length springs in order to reach the target height with some adjustment available. Maybe I would then need helpers to to keep the springs captive under droop.

The bump stops are in good condition, but you can tell from looking at the top and bottom, that they make contact very frequently (bear in mind that I've done about 3000km in 4 years in this car at this height, and the track time would be only a fraction of that). The cable tie is a good idea.