2007 Lotus 2-Eleven
Discussion
With time ticking before the first track outing of the year, I got on with some finishing touches.
Hoovered my mats.
"We" washed it.
..and spent some time measuring the final bit of calibration for the ABS. The Wheel circumference.
The SCS recommendation is to rotate the wheels 10x times, measure the difference travelled and then divide by 10 to reduce any measurement errors. I did this in steps of 2x rotations, as I didn't have a 20m tape measure!
Spent an hour or so of the delightful BH weekend to do some final checks on the ECU, ABS and Dash configs. I spotted one problem with the calculated gear ratios, so the dash doesn't quite know what gear I'm in with the new wheelspeed data... small job to fix when I get time just to run it up and down the road in all gears.
Then that's it, off to the races!
Hoovered my mats.
"We" washed it.
..and spent some time measuring the final bit of calibration for the ABS. The Wheel circumference.
The SCS recommendation is to rotate the wheels 10x times, measure the difference travelled and then divide by 10 to reduce any measurement errors. I did this in steps of 2x rotations, as I didn't have a 20m tape measure!
Spent an hour or so of the delightful BH weekend to do some final checks on the ECU, ABS and Dash configs. I spotted one problem with the calculated gear ratios, so the dash doesn't quite know what gear I'm in with the new wheelspeed data... small job to fix when I get time just to run it up and down the road in all gears.
Then that's it, off to the races!
First track outing as ever was to be at Blyton Park. My Local track, and a great one for shaking down winter tweaks.
Would be a little different this year though, as it was a Javelin Sprint Series taster day with a morning of open pit lane trackday, and an afternoon of timed sprint runs.
Not an ideal environment for testing so many changes to the car, but I'd had every intention of doing a "normal" OPL day before this... just the garage works put a stop to that.
Arrived to a rather crisp morning, but was forecast dry for the day. All good.
Plan was to go out on the old AR1 tyres for a couple of sessions and just check I wasn't locking brakes up left right and centre. Didn't want to ruin the A052 if so!
First session I went as hard as I could onto the brakes on T1 after the start just to get a feel of how well the car would stop on the sprint laps later when everything is cold. The answer was, not well. I got lots of ABS triggering and the car just about hauled itself up, but it wasn't a great feeling.
As the laps piled on and the tyres ballooned in pressure the car felt quicker and quicker and by the end the brakes felt great. Really strong pedal feel, good modulation and was quite intuitive as to when ABS would trigger. On warm pads/tyres, the ABS triggering was few and far between. Fair amount of traffic on this session, so hard to measure anything useful - but the brakes didn't fall off, so there's that.
On the second session, I reset the hot tyre pressures and managed to get a few clear laps.
I had no inclination to play with brake balance at all, because the car felt 'right'. Stable in braking and seemed to be hauling itself up just fine. I did back the ABS off a bit, if 1 = Fully Wet, most intrusion and 10 = Fully dry, most allowable yaw I ended up running a setting of 7.
This gave me just a bit of movement in the car on turn-in when still trailing the brakes, and the odd chirp of a locking tyre (but nothing sustained with tyre smoke everywhere). If I dialled it closer to 10, the car was noticeably less stable on the brakes, but I imagine on a properly warm day where I'm really pushing on this will be a great setting.
I knew grip would be compromised in the afternoon due to cold tyres, so I kept it at 7 for the rest of the day.
On this second session, I was already matching the best times I'd ever done at Blyton which was rather promising. The car didn't feel anywhere near as close to the edge either to hit those times, in fact I still felt like I was warming up.
The noticeable difference with the car compared to last time aside from the brakes is the changes I made to engine mapping. Previously I had a "slow" map of 260bhp, and a "fast" map of 300bhp. But I was scared to use the 300 one in fear of smashing the gearbox.
Now I have a slow of 260, and a fast of 280. As such, I'm now using the fast one on trackdays and in effect, am up on power from previous visits.
There's "a line" that gains a lot of time at Blyton, and involves somewhat straight lining over a curb at "The Ump". Figured I'd see if I could clear it in case I got a bit competetive in the afternoon...
Turns out the answer is "sort of". Splitter catches it, get a lovely smell of smouldering sawdust for a few more corners but the chassis-proper remains unscathed. Free time, woo!
Now that I felt I had a decent baseline, I came in and swapped over for the A052 tyres which seem to have generated legend status.
First outing would be a 'scrubbing' one, bring them up to temp and just get a feel. Immediately I noticed that the sidewalls felt softer and more forgiving. This gave the car less of a 'racey' feel compared to the AR1 but no question the grip was there in return.
Slowly ramped up and was pretty much on the pace from earlier sessions by the time I came in with once again, ballooned tyres.
https://www.youtube.com/watch?v=nTCfnwJ_pQQ
Video of a lap from that session. Front end not quite where I expected it to be on a couple of corners which sent me for a nice bumpy ride over the finish line. Interestingly this lap is within fractions of my best ever at Blyton but looks considerably slower. No doubt I was leaving lots on the table at the weekend, but it's promising to know the car has some core performance unlocked within it.
I Reset pressures to go out again and then was hit with a red flag which would keep the track closed right up until just before lunch. Annoyingly with some oil down on the Bishops corner and a load of cement dust really compromising the track and stopping me from getting a proper session in on the 52s.
Onto the lunch break and was still not sure exactly what I thought about the 52s. No doubt they have more grip to offer, but they feel noticeably more "road-like" in their steering response. That's not to say it's a bad thing, just what jumped out at me on a back to back test.
Going into the sprint afternoon and we'd have one untimed practise run, then 3 (turned out to be 4) timed runs depending on how quickly they rotated the field. Cars were numbered in an approximate class system, not the proper classes they use for championship events but just to roughly get us in performance order. I was granted #12, so in the first group to launch.
Practise run went 'Ok'. Was aiming to do fairly gentle launches, 3-4k RPM then slip the clutch out to let the clutch take the beating rather than the gearbox, but the TC was far too disruptive and bogged me down a bit when trying to get on full power. Still, it got away well and the rest of the run went without drama. Brakes and tyres performed better than I expected after cooling off over lunch so that was reassuring.
The cement dust at Bishops was still really unnerving though. Not sure how other participants attacked it but I'd say I was 6/10ths at best through there for the rest of the afternoon.
First timed run came round very quickly, so off we went. Launch went even worse this time, TC to blame but I eventually spluttered away and got on with it.
Car felt great through the back half of the circuit, and my sector times concurred. Came across the line with a 1.10.X, which matched by previous best time at this event on my Exige - so decent start. P3 overall.
I knew the car had loads more left in it, so the competitive bug started to nibble away at this point.
Next session came around and I disabled the TC. Plan would be to disable it for the launch then flick it back on down the first straight. I wouldn't say the car is traction limited, but the TC is very useful at arresting the spinning inside wheel I get on some corners courtesy of the open differential, so I quite liked to have it in place.
Launch was LOADS better, no stink of clutch, no hopping of the drive train, just a nice smooth amount of slip and launched me on my way. This brought my 0.60ft time to within 0.2sec of the AWD cars that occupied the times ahead of me. In all of the overthinking of the TC settings though, I forgot to switch to my faster map - so when I crossed the line with a 1.09.X it felt like a wasted opportunity.
Next session came around, and was the final scheduled one. I completely fluffed the 1st-2nd gear change off the launch and then was just distracted for the rest of the lap. Still, another 1.09.X and had slipped to 4th in the overall table as some faster cars started showing up.
I went in for a brew to calm myself down at this point and get ready for the trailer loading operation, but then the WhatsApp group pinged to say we did indeed have time for a fourth run.
I got lined up, map definitely in the 'fast' one. TC definitely switched off. All good.
Set off, another good launch and fired down the start straight. This car really does fly off to 70-80mph insanely quickly even when fortunate enough to have an EV and a V12 Ferrari on the drive to compare it to.
I distinctly remember getting to T1 and being way to cautious. Probably just bottled it a bit knowing it was the first run, but hey ho that's the way it goes.
Got round the rest of the lap without much drama, generally felt very conservative but the stopwatch didn't lie as I came in to a high 1.08.
https://www.youtube.com/watch?v=nCoQH8Tpyuw
Happy to at least keep improving on the day, but I know there's an easy second or two still in the car!
All in all, a really successful day. The ABS was almost completely transparent in its contributions which is exactly what you'd hope for. Not playing with brake bias was probably a missed opportunity based on what I've since learned in data logs (looks like I'm still over biased towards the rear, so losing some brake performance due to that. ABS is hiding the implications a treat, but is robbing me of ultimate performance).
The ability to turn into T1 really early whilst still heavily on the brakes was novel. Not sure if it's quicker, but it really opens options up for corners like that where you feel like you're compromised no matter how you approach it.
The only niggles with the car were the gear ratio calculations being wrong on the dash, and I think my brake pedal sensor needs backing off a bit as it occasionally came on whilst the car was parked.
Oh, and a niggle resurfaced from the end of last season which I totally forgot about. The Clutch pedal occasionally feels slow to return to the top of its travel. I'll stick my head in the footwell and make sure all is well with the return spring etc, but open to other possibilities/suggestions.
I'm back to Blyton in a couple of weeks for a good old fashioned OPL day, so really hope to spend more time with the brake bias and the A052 tyres for that.
Two notable observations from the data logs:
1) Only using around 40bar of brakeline pressure when on track. Can generate 90+ when static in the garage.
2) Rear brake line pressure is fluctuating on really heavy stops, which correlates with ABS triggering so I *think* the rear is still over braking. Ideally it's the front that locks/triggers first. That said, the resolution on the data logging is not quick enough to really tell me for sure so I've made some config tweaks to hopefully get more granular data next time out.
Would be a little different this year though, as it was a Javelin Sprint Series taster day with a morning of open pit lane trackday, and an afternoon of timed sprint runs.
Not an ideal environment for testing so many changes to the car, but I'd had every intention of doing a "normal" OPL day before this... just the garage works put a stop to that.
Arrived to a rather crisp morning, but was forecast dry for the day. All good.
Plan was to go out on the old AR1 tyres for a couple of sessions and just check I wasn't locking brakes up left right and centre. Didn't want to ruin the A052 if so!
First session I went as hard as I could onto the brakes on T1 after the start just to get a feel of how well the car would stop on the sprint laps later when everything is cold. The answer was, not well. I got lots of ABS triggering and the car just about hauled itself up, but it wasn't a great feeling.
As the laps piled on and the tyres ballooned in pressure the car felt quicker and quicker and by the end the brakes felt great. Really strong pedal feel, good modulation and was quite intuitive as to when ABS would trigger. On warm pads/tyres, the ABS triggering was few and far between. Fair amount of traffic on this session, so hard to measure anything useful - but the brakes didn't fall off, so there's that.
On the second session, I reset the hot tyre pressures and managed to get a few clear laps.
I had no inclination to play with brake balance at all, because the car felt 'right'. Stable in braking and seemed to be hauling itself up just fine. I did back the ABS off a bit, if 1 = Fully Wet, most intrusion and 10 = Fully dry, most allowable yaw I ended up running a setting of 7.
This gave me just a bit of movement in the car on turn-in when still trailing the brakes, and the odd chirp of a locking tyre (but nothing sustained with tyre smoke everywhere). If I dialled it closer to 10, the car was noticeably less stable on the brakes, but I imagine on a properly warm day where I'm really pushing on this will be a great setting.
I knew grip would be compromised in the afternoon due to cold tyres, so I kept it at 7 for the rest of the day.
On this second session, I was already matching the best times I'd ever done at Blyton which was rather promising. The car didn't feel anywhere near as close to the edge either to hit those times, in fact I still felt like I was warming up.
The noticeable difference with the car compared to last time aside from the brakes is the changes I made to engine mapping. Previously I had a "slow" map of 260bhp, and a "fast" map of 300bhp. But I was scared to use the 300 one in fear of smashing the gearbox.
Now I have a slow of 260, and a fast of 280. As such, I'm now using the fast one on trackdays and in effect, am up on power from previous visits.
There's "a line" that gains a lot of time at Blyton, and involves somewhat straight lining over a curb at "The Ump". Figured I'd see if I could clear it in case I got a bit competetive in the afternoon...
Turns out the answer is "sort of". Splitter catches it, get a lovely smell of smouldering sawdust for a few more corners but the chassis-proper remains unscathed. Free time, woo!
Now that I felt I had a decent baseline, I came in and swapped over for the A052 tyres which seem to have generated legend status.
First outing would be a 'scrubbing' one, bring them up to temp and just get a feel. Immediately I noticed that the sidewalls felt softer and more forgiving. This gave the car less of a 'racey' feel compared to the AR1 but no question the grip was there in return.
Slowly ramped up and was pretty much on the pace from earlier sessions by the time I came in with once again, ballooned tyres.
https://www.youtube.com/watch?v=nTCfnwJ_pQQ
Video of a lap from that session. Front end not quite where I expected it to be on a couple of corners which sent me for a nice bumpy ride over the finish line. Interestingly this lap is within fractions of my best ever at Blyton but looks considerably slower. No doubt I was leaving lots on the table at the weekend, but it's promising to know the car has some core performance unlocked within it.
I Reset pressures to go out again and then was hit with a red flag which would keep the track closed right up until just before lunch. Annoyingly with some oil down on the Bishops corner and a load of cement dust really compromising the track and stopping me from getting a proper session in on the 52s.
Onto the lunch break and was still not sure exactly what I thought about the 52s. No doubt they have more grip to offer, but they feel noticeably more "road-like" in their steering response. That's not to say it's a bad thing, just what jumped out at me on a back to back test.
Going into the sprint afternoon and we'd have one untimed practise run, then 3 (turned out to be 4) timed runs depending on how quickly they rotated the field. Cars were numbered in an approximate class system, not the proper classes they use for championship events but just to roughly get us in performance order. I was granted #12, so in the first group to launch.
Practise run went 'Ok'. Was aiming to do fairly gentle launches, 3-4k RPM then slip the clutch out to let the clutch take the beating rather than the gearbox, but the TC was far too disruptive and bogged me down a bit when trying to get on full power. Still, it got away well and the rest of the run went without drama. Brakes and tyres performed better than I expected after cooling off over lunch so that was reassuring.
The cement dust at Bishops was still really unnerving though. Not sure how other participants attacked it but I'd say I was 6/10ths at best through there for the rest of the afternoon.
First timed run came round very quickly, so off we went. Launch went even worse this time, TC to blame but I eventually spluttered away and got on with it.
Car felt great through the back half of the circuit, and my sector times concurred. Came across the line with a 1.10.X, which matched by previous best time at this event on my Exige - so decent start. P3 overall.
I knew the car had loads more left in it, so the competitive bug started to nibble away at this point.
Next session came around and I disabled the TC. Plan would be to disable it for the launch then flick it back on down the first straight. I wouldn't say the car is traction limited, but the TC is very useful at arresting the spinning inside wheel I get on some corners courtesy of the open differential, so I quite liked to have it in place.
Launch was LOADS better, no stink of clutch, no hopping of the drive train, just a nice smooth amount of slip and launched me on my way. This brought my 0.60ft time to within 0.2sec of the AWD cars that occupied the times ahead of me. In all of the overthinking of the TC settings though, I forgot to switch to my faster map - so when I crossed the line with a 1.09.X it felt like a wasted opportunity.
Next session came around, and was the final scheduled one. I completely fluffed the 1st-2nd gear change off the launch and then was just distracted for the rest of the lap. Still, another 1.09.X and had slipped to 4th in the overall table as some faster cars started showing up.
I went in for a brew to calm myself down at this point and get ready for the trailer loading operation, but then the WhatsApp group pinged to say we did indeed have time for a fourth run.
I got lined up, map definitely in the 'fast' one. TC definitely switched off. All good.
Set off, another good launch and fired down the start straight. This car really does fly off to 70-80mph insanely quickly even when fortunate enough to have an EV and a V12 Ferrari on the drive to compare it to.
I distinctly remember getting to T1 and being way to cautious. Probably just bottled it a bit knowing it was the first run, but hey ho that's the way it goes.
Got round the rest of the lap without much drama, generally felt very conservative but the stopwatch didn't lie as I came in to a high 1.08.
https://www.youtube.com/watch?v=nCoQH8Tpyuw
Happy to at least keep improving on the day, but I know there's an easy second or two still in the car!
All in all, a really successful day. The ABS was almost completely transparent in its contributions which is exactly what you'd hope for. Not playing with brake bias was probably a missed opportunity based on what I've since learned in data logs (looks like I'm still over biased towards the rear, so losing some brake performance due to that. ABS is hiding the implications a treat, but is robbing me of ultimate performance).
The ability to turn into T1 really early whilst still heavily on the brakes was novel. Not sure if it's quicker, but it really opens options up for corners like that where you feel like you're compromised no matter how you approach it.
The only niggles with the car were the gear ratio calculations being wrong on the dash, and I think my brake pedal sensor needs backing off a bit as it occasionally came on whilst the car was parked.
Oh, and a niggle resurfaced from the end of last season which I totally forgot about. The Clutch pedal occasionally feels slow to return to the top of its travel. I'll stick my head in the footwell and make sure all is well with the return spring etc, but open to other possibilities/suggestions.
I'm back to Blyton in a couple of weeks for a good old fashioned OPL day, so really hope to spend more time with the brake bias and the A052 tyres for that.
Two notable observations from the data logs:
1) Only using around 40bar of brakeline pressure when on track. Can generate 90+ when static in the garage.
2) Rear brake line pressure is fluctuating on really heavy stops, which correlates with ABS triggering so I *think* the rear is still over braking. Ideally it's the front that locks/triggers first. That said, the resolution on the data logging is not quick enough to really tell me for sure so I've made some config tweaks to hopefully get more granular data next time out.
I've just spent almost a week going through this from start to finish whenever I've had 10 minutes spare.
It's made for a brilliant read, the detail you go to not only with the car but on here too is exceptional. I'll admit I was completely lost whenever you were talking about electronics and reading the same paragraph 2 or 3 times didn't help, but I've never really understood that side of things at all. It's been fascinating though, looking forward to your next update.
It's made for a brilliant read, the detail you go to not only with the car but on here too is exceptional. I'll admit I was completely lost whenever you were talking about electronics and reading the same paragraph 2 or 3 times didn't help, but I've never really understood that side of things at all. It's been fascinating though, looking forward to your next update.
FTW said:
Cleaning the footwell matts before a trackday is impressive prep!
Great update on the ABS, good luck not getting too lost in all the settings and bias positions!
How much current does it draw during big interventions? Do you have a PDM or using a traditional fuse?
Honestly not sure on the draw during interventions but it has a dedicated feed to the battery via a fuse - all included on the SCS Wiring loom. But more on that in a bit...Great update on the ABS, good luck not getting too lost in all the settings and bias positions!
How much current does it draw during big interventions? Do you have a PDM or using a traditional fuse?
Carl-H said:
I've just spent almost a week going through this from start to finish whenever I've had 10 minutes spare.
It's made for a brilliant read, the detail you go to not only with the car but on here too is exceptional. I'll admit I was completely lost whenever you were talking about electronics and reading the same paragraph 2 or 3 times didn't help, but I've never really understood that side of things at all. It's been fascinating though, looking forward to your next update.
Glad you've enjoyed, plenty more to come I hope!It's made for a brilliant read, the detail you go to not only with the car but on here too is exceptional. I'll admit I was completely lost whenever you were talking about electronics and reading the same paragraph 2 or 3 times didn't help, but I've never really understood that side of things at all. It's been fascinating though, looking forward to your next update.
I try to keep the electronic bits to a minimum because it's both pretty dry/boring but also I don't actually know much about it myself - so the more I say, the more chance there is that I'll be exposed
I investigate the slow to return clutch pedal between events, and guided by John @seriouslylotus I retrieved the clutch line from the slave cylinder.
Where the plastic bit is, this separates with the removal of the clip and can then be rebuilt without the centre part.
The centre part has a restrictor in it with a pinprick hole. Got it plumbed back in and bled, will see how that goes.
Whilst under the car, also adjusted the handbrake cable up a bit.
I took a look at my front camber shims too to see if I could sneak a bit more camber. This is in response to the very unscientific indicator that I'm starting to scrub the wear markers on the tyre shoulders a bit. Unfortunately nowt' doing now without going aftermarket, or machined arms. (the 2-Eleven ones are already different to allow the camber I've got).
It was then time to get trailered up to head back to Blyton. Clocked off work on a nice warm Friday evening and got ready for the quick 20min job to load up.
...Until I found the 2-Eleven battery to be completely flat
It's a LifePO4 one, and charger was no longer recognising it so it was proper dead. Luckily had a spare, but meant the seats needed to come out so I could do the swap.
This is all down to the new ABS unit (I suspect). The 2-Eleven has no parasitic draws in factory trim, what with no alarm, immob, radio, etc. It has an isolator, but the ABS power feed connected directly to the battery.
For now I'll keep the spare battery plugged in between use - but next time I get seats out I'll extend the ABS power cable a bit and connect it to the isolator switch instead I reckon. Can't always have it on trickle especially when it's hiding in the trailer.
20min trailer load turned into 2 hours.
Onto Blyton again, good old fashioned trackday and was excited to just settle into a rhythm of messing with the brake balance.
Another change I'd made was a digital one. My ADU dash/data logger has a limited quota for how much data it can log per second across all channels. It logs a LOT, and so I was able to reduce the log rate of some less important channels and in return increase the granularity of the wheelspeed sensor and brake pressure sensor data considerably.
Wheelspeed and brake pressure got bumped up to 250hz, and Longitude G force up to 125hz. My hope was that the logs would clearly tell me which axle was triggering the ABS to help guide my adjustments. (Having the ABS output a message to say which solenoid is firing would be too convenient...)
I won't do the usual blow by blow account of the day, but the summary is that it all went very well and without drama. Enjoyed some laps with a passenger (ages since I've tracked the car with one it seems) and made plenty of bias tweaks throughout the day.
Example of a log prior to my config changes from a single braking event:
Main observations are that the brake pressure traces (red = rear circuit, blue = front circuit) closely follow each other, and wheel speed traces show that the rear sensors (purple and blue) show a couple of drops, perhaps indicating that rear is trying to lock.
If I compare this to another log (same corner, different day) with my new logging settings I get this:
As you can see it has the desired effect and the log data is much more granular. I can now see pressure spikes on the rear circuit which correspond to the wheelspeed drops. Rear axle is definitely trying to lock!
Also note a drop in longitude g-force as this happens, showing an observational lack of deceleration as ABS is triggering.
Impressive stuff, less so impressive is how bad I am at maintaining brake pedal pressure during heal/toe (TPS blip on the topmost graph) but we'll focus on fine tuning 0.0003% performance from hardware rather than on the 40% I could probably gain by not being crap.
Armed with this info, I gradually crept brake bias forward through the day and was feeling a notable improvement as a result. Brakes felt more responsive, particularly from cold and stopping performance ramped up nicely.
In hindsight I should have bumped the bias forward in much bigger increments, as by the end of the day I was getting much fewer ABS interventions but it was still the rear if/when it happened... so clear I'm still a bit overbraked at the back, I think?
I also played with the ABS adjustment knob to give me more or less intrusion. It had a notable effect on stability - probably not helped by the fact my rear is still the end moving around. I'll revisit this once I'm happier with the brake balance.
Aside from brakes, I was also testing out the A052 tyres properly. I'm still not sure what I think, to be honest. It's clear they have grip - and probably more peak grip than the AR1, but they don't feel as nice to me when accessing that grip. They feel much more like a road tyre, and I really miss the direct response of the AR1. Ultimately they didn't unlock me a heap of performance, felt worse, and are more expensive - so I'll make some efforts to do some back to back sessions on my next trackday before properly concluding. Might be some damper, alignment or pressure settings I can adjust to get more out of them but for now just feel a bit underwhelmed. Perhaps I just overhyped them in my head!
The car was notable slower through the exit of Port Froid (the fast chicane) compared to my last visit on AR1. I noted it on track, and data logs agree. Up to 10kph down on minimum speed.
An important factor in defense of the A052 is that I run narrower sizes of those compared to AR1 (225/195 vs 235/205).
Photographer got some nice shots:
Traffic was pretty gnarly most of the day, with some absolutely shocking driving standards. I even taddled to Javelin late morning because there were some repeat occasions of some pretty dangerous stuff. I've never ever felt the need to report somebody before, in 10 years of trackdaying - I consider myself pretty tolerant.
I wasn't the only one, saw them getting spoken to at least three times, but still were exhibiting similar behaviour in the final session of the day. No idea how many warnings you get...
Oh, clutch pedal return thing totally resolved. By all accounts the restrictor allows for a mechanically imposed slip of the clutch during launch control. I much prefer it gone.
One more graph, sorry.
Can use the same data to look at wheelspin on corner exit too. Where I've written #1 is the exist to bunga bunga which has always been one for spinning up the inside rear.
Back to the brake balance to finish off. I've still got adjustment range to move it forward incrementally during my next trackday, but I will start running out of adjustability soon - and I don't think it's ideal to be on the extreme end of a balance bar.
The fix for this may well be taking a revisit to my master cylinder sizes. I run 0.75" front and rear currently, and dropping front circuit to a 0.7" should in theory move the bias naturally forward a touch and also give me a slightly softer pedal - which honestly I think I'd like. I could barely walk on Sunday!
Where the plastic bit is, this separates with the removal of the clip and can then be rebuilt without the centre part.
The centre part has a restrictor in it with a pinprick hole. Got it plumbed back in and bled, will see how that goes.
Whilst under the car, also adjusted the handbrake cable up a bit.
I took a look at my front camber shims too to see if I could sneak a bit more camber. This is in response to the very unscientific indicator that I'm starting to scrub the wear markers on the tyre shoulders a bit. Unfortunately nowt' doing now without going aftermarket, or machined arms. (the 2-Eleven ones are already different to allow the camber I've got).
It was then time to get trailered up to head back to Blyton. Clocked off work on a nice warm Friday evening and got ready for the quick 20min job to load up.
...Until I found the 2-Eleven battery to be completely flat
It's a LifePO4 one, and charger was no longer recognising it so it was proper dead. Luckily had a spare, but meant the seats needed to come out so I could do the swap.
This is all down to the new ABS unit (I suspect). The 2-Eleven has no parasitic draws in factory trim, what with no alarm, immob, radio, etc. It has an isolator, but the ABS power feed connected directly to the battery.
For now I'll keep the spare battery plugged in between use - but next time I get seats out I'll extend the ABS power cable a bit and connect it to the isolator switch instead I reckon. Can't always have it on trickle especially when it's hiding in the trailer.
20min trailer load turned into 2 hours.
Onto Blyton again, good old fashioned trackday and was excited to just settle into a rhythm of messing with the brake balance.
Another change I'd made was a digital one. My ADU dash/data logger has a limited quota for how much data it can log per second across all channels. It logs a LOT, and so I was able to reduce the log rate of some less important channels and in return increase the granularity of the wheelspeed sensor and brake pressure sensor data considerably.
Wheelspeed and brake pressure got bumped up to 250hz, and Longitude G force up to 125hz. My hope was that the logs would clearly tell me which axle was triggering the ABS to help guide my adjustments. (Having the ABS output a message to say which solenoid is firing would be too convenient...)
I won't do the usual blow by blow account of the day, but the summary is that it all went very well and without drama. Enjoyed some laps with a passenger (ages since I've tracked the car with one it seems) and made plenty of bias tweaks throughout the day.
Example of a log prior to my config changes from a single braking event:
Main observations are that the brake pressure traces (red = rear circuit, blue = front circuit) closely follow each other, and wheel speed traces show that the rear sensors (purple and blue) show a couple of drops, perhaps indicating that rear is trying to lock.
If I compare this to another log (same corner, different day) with my new logging settings I get this:
As you can see it has the desired effect and the log data is much more granular. I can now see pressure spikes on the rear circuit which correspond to the wheelspeed drops. Rear axle is definitely trying to lock!
Also note a drop in longitude g-force as this happens, showing an observational lack of deceleration as ABS is triggering.
Impressive stuff, less so impressive is how bad I am at maintaining brake pedal pressure during heal/toe (TPS blip on the topmost graph) but we'll focus on fine tuning 0.0003% performance from hardware rather than on the 40% I could probably gain by not being crap.
Armed with this info, I gradually crept brake bias forward through the day and was feeling a notable improvement as a result. Brakes felt more responsive, particularly from cold and stopping performance ramped up nicely.
In hindsight I should have bumped the bias forward in much bigger increments, as by the end of the day I was getting much fewer ABS interventions but it was still the rear if/when it happened... so clear I'm still a bit overbraked at the back, I think?
I also played with the ABS adjustment knob to give me more or less intrusion. It had a notable effect on stability - probably not helped by the fact my rear is still the end moving around. I'll revisit this once I'm happier with the brake balance.
Aside from brakes, I was also testing out the A052 tyres properly. I'm still not sure what I think, to be honest. It's clear they have grip - and probably more peak grip than the AR1, but they don't feel as nice to me when accessing that grip. They feel much more like a road tyre, and I really miss the direct response of the AR1. Ultimately they didn't unlock me a heap of performance, felt worse, and are more expensive - so I'll make some efforts to do some back to back sessions on my next trackday before properly concluding. Might be some damper, alignment or pressure settings I can adjust to get more out of them but for now just feel a bit underwhelmed. Perhaps I just overhyped them in my head!
The car was notable slower through the exit of Port Froid (the fast chicane) compared to my last visit on AR1. I noted it on track, and data logs agree. Up to 10kph down on minimum speed.
An important factor in defense of the A052 is that I run narrower sizes of those compared to AR1 (225/195 vs 235/205).
Photographer got some nice shots:
Traffic was pretty gnarly most of the day, with some absolutely shocking driving standards. I even taddled to Javelin late morning because there were some repeat occasions of some pretty dangerous stuff. I've never ever felt the need to report somebody before, in 10 years of trackdaying - I consider myself pretty tolerant.
I wasn't the only one, saw them getting spoken to at least three times, but still were exhibiting similar behaviour in the final session of the day. No idea how many warnings you get...
Oh, clutch pedal return thing totally resolved. By all accounts the restrictor allows for a mechanically imposed slip of the clutch during launch control. I much prefer it gone.
One more graph, sorry.
Can use the same data to look at wheelspin on corner exit too. Where I've written #1 is the exist to bunga bunga which has always been one for spinning up the inside rear.
- 2 more surprisingly is the exit of Port Froid, a very fast chicane.
Back to the brake balance to finish off. I've still got adjustment range to move it forward incrementally during my next trackday, but I will start running out of adjustability soon - and I don't think it's ideal to be on the extreme end of a balance bar.
The fix for this may well be taking a revisit to my master cylinder sizes. I run 0.75" front and rear currently, and dropping front circuit to a 0.7" should in theory move the bias naturally forward a touch and also give me a slightly softer pedal - which honestly I think I'd like. I could barely walk on Sunday!
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