HSV MX5

punkoutnz · Post by **punkoutnz** » Sun Jul 15, 2012 8:23 pm

I ran Motul RBF600 which I got from BNT, apparently they have a new fluid which is pretty much the same stuff minus the branding which is a heck of a lot cheaper. I couldn't get my pads to fade in the WRX with that fluid and I was being pretty hard on them at Taupo.

Mad Kiwi · Post by **Mad Kiwi** » Sun Jul 15, 2012 10:40 pm

I would be in for some Motul 600 type fluid if it's cheap ish...

I can't bring myself to pay $32 for 500 mls of the motul 600....

Although I would if i had to....hopefully the new brake ducts will help out...

Euen · Post by **Euen** » Sun Jul 15, 2012 10:48 pm

I just use BNT's house brand in the TG. Have been using it on Targa and track without any problems. Its what they call their 300 Plus Racing brake Fluid.

But then I am not trying to stop a V8.

Born_disturbed · Post by **Born_disturbed** » Mon Jul 16, 2012 8:28 am

Donovan wrote:I got red flagged because apparently my brakes where on fire, personally I think the marshal was over reacting a bit.

Which one, 3 saw them burning up

dynofiend · Post by **dynofiend** » Mon Jul 16, 2012 9:02 am

I meant to say as well, I remember the TVR Tuscan race cars used to suffer from horrendous rear axle locking under downshift braking. Mostly the only way to counteract it was pinpoint perfect heel toe braking. It strikes me just how similar a V8 mx5 is compared to a Tuscan Challenge car in layout. Both FR V8s in a lightweight convertible shell!

Your driving on track looked great but I couldnt hear if you were heel toeing or not? If not, it's a great time to learn

Donovan · Post by **Donovan** » Mon Jul 16, 2012 9:20 am

Wasn't heel toeing out on the track. I usually practice when I am just driving around, but most of the time when I get on the track I completely forget to do it, plus I have never really had to in any other car that I have had. Also, sometimes the brain really goes out the window when I get the red mist on, especially when I have a Porsche lined up in my sites

(although I am pretty sure he was only going at 75%, well of the cars capabilities, not the drivers).

Too be honest, found that Porsche guys out there on Saturday to be real pricks, they were treating the track like a race day, and pushing in on the queues to get out on the track by getting their pit crew guys to come out and stop the other cars going, when everyone else had lined up for 5 mins or so. Passing people on the corners, ok if they were doing that to me, but they forget there are some people out there that have never been on Hamptons before, or even done a track day.

Donovan · Post by **Donovan** » Mon Jul 16, 2012 9:23 am

Born_disturbed wrote:Which one, 3 saw them burning up

The others were just being sheep and falling into the power of suggestions from the first one that thought they say them on fire.

Anyway, just had bought a front lip spoiler with vents that I can pipe up for the brakes. Actually the same sort I order from Flyin Miata with the original V8 kit, that "never turned up" and only just found out that it didn't when I went to pick up the car, so a bit late to sort out a replacement after a year and a half.

dynofiend · Post by **dynofiend** » Tue Jul 17, 2012 10:56 am

Donovan wrote:Wasn't heel toeing out on the track. I usually practice when I am just driving around, but most of the time when I get on the track I completely forget to do it, plus I have never really had to in any other car that I have had.

I think that a good heel-toe downshift technique will help no end with both the rear locking, and the brake overheating. It's quite likely that without confidence in using the engine braking, you were compensating with the brake pedal, adding to whatever problems you had with fluid or pads. Nothing at all wrong with practicing on the road either, finding the opportunities is the hard bit!

MX4000 · Post by **MX4000** » Tue Jul 17, 2012 8:53 pm

Simpler way to deal with the rear brake issue is just to fit a bias valve in the line to the rear brakes. Worked well when I was getting very sideways under brakes at Ruapuns. Tried heel and toe but in the heat of the moment it is far too easy to overcook it and end up backwards in the long grass

Donovan · Post by **Donovan** » Sun Jul 22, 2012 9:15 pm

Rightly, firstly a big thank you to Mad Kiwi for helping me work on the car getting things prepped for taking it down to Taupo on Saturday, we spent a couple of nights up to midnight sorting out things, took so long as we were fumbling around and talking shit.

So made up a couple of backing plates for the front brakes with, put a front lip spoiler on that allowed us to shove a couple of 50mm tubing to feed air to the front rotors via the backing plates, replaced the pads, which the original ones were toast, and had only done 1 track day in them!!! Flushed the existing brake fluid and replaced with the BNT branded stuff Euen had used, only cause that was the only stuff they had in stock of more than 1 bottle, which I thought I would need two to flush out, turns out I got away with 1 after all.

Just for anyones reference, from BNT Motul RBF660 is $43+GST, RBF600 is $28+GST and their BNT branded stuff (in exactly the same bottle as the Motul RBF600 with the same part numbers stamped on it) is $24+GST.

Last minute on Friday, got the mounting bracket modified to put a Jamex race seat in for the passenger side to take passengers out.

Went put the car on the trailer, and then found out it wouldn't get up there with the new front lip on it, even with the Suspension raised to the highest height. Quickly had to make up some ramp extension with 6x2 lying around the place, and managed to get it up on there and tow it down to Taupo.

Donovan · Post by **Donovan** » Sun Jul 22, 2012 10:04 pm

Taupo, so the day of reckoning, to see whether all the hard work had paid off, and whether my brakes would last. The plan was that this was supposed to be a testing day running an open pit facility, which would give me time to go out, do 5 or 6 laps, and then come back in and fiddle with stuff to see whether things go better or worse. When we turned up, found out that there was a single seater booked in for the test session as well, and the track wouldn't allow tin tops (wheel fibreglass in my case) and the single seater run on the track at the same time, so the sessions were split into 30mins for the cars, and then 30mins for this single seater on the track. So out the window with the major changing around just go out and have a play.

First session out and the brakes felt a bit strange, the first time I would hit the pedal it would go a lot further down than it normally would, and if I took my foot off the brake and then on again, they would be as they should be, and this was how it was for that complete time out, did about 9 laps or so with the brakes like this.

Next session was chasing down a GTR, which after a few laps caught him, but he was pretty quick in a straight line, so there was never enough of the straight for me to get past him, so decided I would try to outbrake him in one of the laps, got a crap exit out of the sweeper, lost a bit of ground on him, caught towards the end, and left my braking to as much as I thought I could get away with it, while still leaving a bit of a margin to pull quicker if I needed to. Turns out I needed to, as I figured he was going to possibly start thinking about turning in for the corner as I was still beside him, so I chickened out and pulled up quicker than what I was intending to, to drop behind him and avoid having and impression of a GTR in my drivers door. After that, my brakes were gone again, so did a cool down lap around the track and felt them coming back, but came into the pits anyway. Opened the bonnet to let things cool down, and found that the power steering fluid had boiled over and my nice clean engine bay was not longer clean, and was all covered in power steering fluid. Man that stuff stinks when it has been burnt, took the top off the bottle when it was cooled down and bit, and the smell of it when the lid came off just about made me puke. Topped it up again, and drove the rest of the time with lights up to try and force air onto the bottle which is just behind the lights to keep it a bit cooler. There is no cooling tube for it at the moment, I have one, so will need to get that setup to try and stop that from happening.

Third session out, and the brakes seemed to be premo, no further pedal travel on the first press of them and they never seemed to fade, so felt a bit more confident with them, but still never 100%. Enough to play with a race prepped M3 (the 3.2ltr Vanos model), that was until my tyres went off. Straight line grip was fine, and under braking was fine, but going around corners was mostly 4 wheel difting or hanging the butt out big time. Didn't help that the LSD had gone on my again, and I was just spinning up the inside wheel most of the time, so could never put down the power cleanly.

After that, my tyres never seemed to recover. Someone there suggested to try dropping the tyre pressure, which I did but that only seemed to make it more slippery. Turn in was fine, it was just mid to exit that was a bit hairy. Have discovered I know exactly jack shit about setting a car up for the track so I am really going to have to sit down and pick someone's brains at some stage to learn what things I need to change and what effect they have on the car to really get some good times out of the wee beastie. Best time of the day when the tyres were giving me some grip was 1.49.7 according to the GPS lap time I run in my phone, not sure how accurate it is, as never had anyone on a stop watch at the same time I have been running it.

Attached picture is at the Garage there, you will see the ducting pipes sicking out the front for the brake cooling, need to get a proper entry feeder to the pipe made up that should force more air to the brakes.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon Jul 23, 2012 8:15 am

My race pads needed to be bedded in for the first 200k according to the supplier so no heavy braking.

Must be time to go to a manual steering rack by the sounds of it as i find it hard to believe it could boil-over unless the engine is doing it...steering use shouldn't cause it even on a track.

punkoutnz · Post by **punkoutnz** » Mon Jul 23, 2012 8:29 am

It's not the steering use, it's the fluid being forced around the system by a high revving pump that causes it to over heat in this kind of situation.

Angreal · Post by **Angreal** » Mon Jul 23, 2012 8:36 am

I managed to get steering fluid spilling out everywhere after Saturday as well. Any simple way around this such as getting one of those oil coolers with a miniature radiator and a bit of a re-route?

Euen · Post by **Euen** » Mon Jul 23, 2012 8:59 am

As Angreal mentioned you may be better off looking at a proper cooler for the PS fluid if it is getting that hot. If my memory is right then I think the standard cooler is just an extra length of steel tubing that loops across the front of the car.

The other thing that may help your brakes a bit (and you may already have considered it) is to fit funnel or collector on the front of the ducts that fits the hole in the front lip to catch as much air as the hole will allow.

Donovan · Post by **Donovan** » Mon Jul 23, 2012 9:42 am

Have cooling tube from the NB that I am pulling apart, so will try and get that plumbed in before the next time I take it out on the track, hopefully that is enough to make a difference.

Yes, I know I have to sort out the feeding into the cooling hose, it was a quick fix as I knew I didn't have time to make up a decent set of feeders before the weekend, and figured that just having the hoses poking out the front was better than nothing.

Furai · Post by **Furai** » Mon Jul 23, 2012 10:21 am

Get some Mazda 787B front wheels, That'll sort your braking issue.

Out of curiosity what wheels are you running on the front at the moment?

Donovan · Post by **Donovan** » Mon Jul 23, 2012 11:27 am

these

Mad Kiwi · Post by **Mad Kiwi** » Mon Jul 23, 2012 11:36 am

Angreal · Post by **Angreal** » Mon Jul 23, 2012 11:47 am

Alternatively re-route your aircon to blow cold air onto the brakes?

Donovan · Post by **Donovan** » Mon Jul 23, 2012 12:04 pm

my air con is having the roof removed, so guess I already have it feeding to the brakes with the cooling hoses in place

Donovan · Post by **Donovan** » Thu Aug 02, 2012 4:11 pm

Cert process started, not much to really do. Need to put in a shield over the universal joint on the drive shaft, gearbox end (yes, was already told that I need to do that), wrap the exhaust as it is too close to the brake/fuel lines and have some sort of test done on the steering wrack, as I wasn't able to prove at the time that it was in exactly the same place it was before. Might get Flyin Miata to answer that one.

So not a lot really, otherwise all good, get those things done and it will be all road legal again.

However, when it was up on the hoist, and having a good look around, found heaps of cracks in the front rotors, so they are going to have to be replaced. Much to the dismay of Mad_Kiwi, I will be going to bigger rotors, currently 280mm, will see if I can find some 310mm. Certifier took on look at the rotors and said that I needed to go bigger as well for track use, said they were tiny.

Rear tyres are pretty much just about stuffed. Only done about 2,000km's on them, with two track days in there. Going to have to go a bit lighter on the old right boot methinks.

Donovan · Post by **Donovan** » Thu Aug 02, 2012 4:15 pm

Also have got some Redline 80W/140 Gear oil for the diff, to hopefully help it lock up better for track use. If this doesn't work, then I am going to have to start looking for a Holden mechanical LSD

Hate to think how much one of those are.

Donovan · Post by **Donovan** » Tue Aug 07, 2012 9:24 pm

Changed the diff oil, old stuff was black, running and very stinky, so thought it would have made a huge difference with the new stuff.

Didn't seem to on the track, still felt the inside wheel spin up. Sigh, looks like a Holden mechanical diff on the shopping list in the future, but it will just have to wait a while before I get to that.

Brakes better, but still not 100%. Worn the rears down to the metal in just two and a half track sessions. Not sure if the bias is all up the wack, or because the springs in the front aren't up to the task. Swapping those over before the next session and see how we go.

Pedal feel still not great, seem to be down on fluid after the last few track days, down about a 1/4. Can't see any brake fluid on the floor, or leaking out of the calipers. Someone has told me it could be a seal in the BMC causing that, so going to try doing the rebuild on that (or the NB on that I have just in case I stuff it up).

na6*dori · Post by **na6*dori** » Tue Aug 07, 2012 11:18 pm

you could happily fit a small transmission cooler to the return line of the powersteering without issues of pressure, may also help to have your pump stripped and make sure its not a pressure relief valve issue, just as an idea. and if it still does it then fabricate up a bigger resevior but keep fluid level the same, thus allowing for the expansion of fluid without sending it skyway

HSV MX5

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