Then I logged it properly. The logs showed that the tyre produced its best acceleration at less slip than some of my more permissive modes allowed, the speed offsets could drive the final target below zero, and the integral term was storing positive torque while the car was below target. When wheelspin arrived, part of the PID was briefly helping it.

This is the latest iteration: what changed, what the evidence actually supports, and what still needs a warm, dry road before I call it finished.

The starting point

Status: Verified – Rear tyres are 295/30/19 Continental SportContact 7s.

The strategy has always had two halves. Feedforward predicts the engine torque the tyre should accept. Closed loop PID then corrects whatever the prediction could not know about: temperature, damp patches, surface changes, load transfer and bumps.

The torque model is normalised to third gear. The traction strategy itself is not normalised until the final gear scaler is applied. That distinction matters because a torque value in the base table is not the engine torque the car will necessarily receive in second, fourth or fifth.

The tyre peak moved the targets

Status: Working conclusion

The useful result from the earlier dry data was a tractive force peak around 9,500 to 9,800 N at roughly 5 to 6 percent slip. Once slip moved into the 6 to 8 percent band, median tractive force fell to about 8,860 N. More wheelspin felt more dramatic, but it accelerated the car less.

That immediately made two settings look wrong. Mode 7 allowed 7.9 percent straight line slip and Mode 9 allowed 12 percent. Both sat beyond the measured force peak. They were permissive, but they were not the fastest settings.

The later road test complicated the picture. It was cooler and the road was not completely dry. Maximum logged tractive force was about 7,982 N rather than 9,500 N. The road rose by only about 0.17 percent over the measured section, worth roughly 30 N on a 1,750 kg car, so gradient could not explain the difference. Tyre and road condition could.

That means 9,500 N remains a dry baseline, not a universal grip limit. The system still needs slip feedback because no fixed torque table can know whether the tyre is warm, cold, dry or sitting on a damp seam.

Rebuilding the rotary modes

Status Calibration loaded for validation

The rotary still selects the character of the car, but the straight line targets now have a cleaner progression. Mode 3 remains the chilled setting. Mode 4 is the normal fast road setting. Mode 5 is for a known dry road on warm tyres. Mode 6 allows movement, but no longer asks the SC7 to live well beyond its measured force peak.

The lateral G shapes were rebuilt at the same time. Both sides are now symmetrical because there was no evidence supporting different left and right targets. Every active road mode tapers as lateral acceleration increases, because the tyre has less longitudinal capacity available while it is also producing cornering force.

The speed offset was doing too much

Status: Calibration loaded for validation

The final target is the lateral G table plus a speed offset. The old high speed offsets were large enough to make the combined target negative in the conservative modes. Unless that is correcting a measured wheel speed bias, a negative slip target has no useful meaning.

The revised table keeps the low speed launch allowance, but reduces the 25 km/h addition from nine percentage points to five. The target now blends down towards the normal table by 45 km/h instead of falling off a cliff. Above 180 km/h the negative offsets remain, but they are smaller and cannot erase the underlying target.

That gives the same rotary a consistent meaning at every speed. Mode 3 remains conservative rather than becoming impossible at high speed, and Mode 7 remains the quickest dry road target rather than turning into an arbitrary number once the car passes 180 km/h.

A feedforward table built around tractive force

Status Current baseline

The largest architectural change is the main feedforward surface. Instead of treating slip error as the only description of available grip, the new table is indexed by modelled tractive force and engine torque before reductions.

The surface rises towards 9,500 N, then deliberately falls away. At a 950 Nm unrestricted torque input, the table returns 594.9 Nm at 8,000 N, 652.7 Nm at 9,500 N and 597.1 Nm at 10,500 N.

Apply the fourth gear normalisation factor of 1.263 and those become approximately 751, 825 and 754 Nm at the engine. The peak is therefore almost exactly where the warm, dry SC7 data said it should be. Above the peak, the table asks for less torque because the tyre has already moved onto the wrong side of its force curve.

This is still a model. Emtron tractive force is largely derived from engine torque and gearing; it is not a strain gauge measuring the contact patch. The table provides a gear aware first estimate. Slip feedback remains the part that discovers the road is wet.

The integrator was adding torque

Status: Verified defect

The most important log finding was not a lack of negative integral authority. It was positive windup.

With slip below target, the original controller allowed the integral output to climb to its positive 50 Nm clamp. One run held it there for about 1.3 seconds. Another retained the full 50 Nm across approximately 2.75 seconds. The tyre was not slipping too much, so the controller stored permission to add torque.

When overslip arrived, the proportional and derivative terms reacted immediately, but the integral term had to unwind before it could help. At the worst point in one event the contributions were minus 7.6 Nm proportional, plus 37.6 Nm integral and minus 0.9 Nm derivative. The combined PID contribution was still plus 29.1 Nm while the tyre was already beyond target.

The controller remained stable because the feedforward model, throttle reduction and ignition retard were doing the real work. That does not make the integral behaviour acceptable. A stable result can still contain two control terms fighting each other.

The fix was removing positive authority

Status: Changed awaiting full dry validation

The positive integral clamp is now zero. The negative clamp remains minus 50 Nm.

Below target slip, the integral term now sits at zero. Once the tyre exceeds target it can accumulate negative correction, up to 50 Nm. There is no positive value left to unwind and no stored torque waiting to oppose the first intervention.

I initially considered extending the negative clamp to minus 75 Nm. The logs killed that idea. In the later full throttle events the negative integrator reached only minus 4.3 Nm in one run and zero in the other. More negative authority would have solved a problem that was not happening while increasing the risk of a torque hole after the tyre recovered.

The proportional, integral gain and derivative tables therefore stay unchanged for the next test. Changing several control terms at once would make the result impossible to attribute. The positive clamp was the proven defect, so that is the change being isolated.

What the road logs now say

Status Verified for the logged conditions

Both runs used the conservative Mode 3 target. Neither needed ignition or fuel cuts. The car controlled the tyre with modest timing reduction and without the controller cycling torque up and down.

The lower 7,982 N tractive force result from the cooler, imperfectly dry run should not be used to rewrite the dry table. It is evidence that the available grip changed. That is exactly why the feedforward and feedback halves both exist.

The same session produced a roughly 4.8 second 100 to 200 km/h run without full boost at 100 km/h. The performance matters, but the cleaner result is the behaviour: a 914 whp pump fuel car remained controlled on a cool road without cuts or abrupt throttle closure.

Power mode and traction mode are separate decisions

Status: Verified

The torque request rotary decides how much engine performance is available. The traction rotary decides how much of that performance the tyre may use. Treating them as one setting hides useful control.

The high torque modes already allow enough demand to exceed the rear tyre in second and third, while effectively releasing full engine output from fourth upwards. Increasing those torque tables would not make the car faster. It would only give the traction strategy a larger error to remove.

For a dry road the useful combination is a high torque request with Mode 5 or Mode 6 traction control. Mode 3 is deliberately conservative. Mode 7 is now a permissive track setting rather than a 12 percent wheelspin setting dressed up as performance.

The current configuration (Emtron specific)

What still needs proving

The next valid test is on the same dry road, in both directions, with warm tyres. Running in both directions removes most of the gradient and steady wind error. Mode 4 should be tested first, followed by Mode 5, with full pedal held through the shift long enough to see the integrator unwind and torque recover.

The stop condition is simple. If slip rises beyond about 6.5 percent and tractive force does not increase, the tyre has crossed the peak. If force continues to rise at 5.5 percent slip, Mode 6 is doing its job. If the controller oscillates or leaves a torque hole after intervention, the PID still needs work.

Until that test is complete, the new force peak and the revised permissive modes remain evidence based working settings rather than finished calibration.

The lesson from this iteration

The first version was designed to prevent wheelspin. This version is being calibrated to maximise acceleration without making the car unpleasant.

That distinction changed the questions. How much slip is allowed is less useful than where the tyre produces maximum force. A larger integral clamp is less useful than checking whether the integrator is acting in the correct direction. More available engine torque is irrelevant when the tyre is already the limit.

The car already had enough power. The latest changes are about making the control system stop wasting it, whether that waste comes from excessive wheelspin, an over-conservative target or two parts of the PID fighting each other.

That is the point of logging it properly. The calibration stops being a table that looks sensible and becomes a system that can explain what the car actually did.

Huge thanks to Adrian at Emtron Australia for the pointers in this. It’s been invaluable.

The post What the Logs Changed in My Supra Traction Control first appeared on BlownByTwins.

The day started, as ever, at my local Shell garage, topping up the tank and driving as slowly to the port as possible, conserving as much as fuel as I could for the few days over there. The Isle of Man Steampacket takes around 2h 45m from Liverpool to Douglas and it’s about what you’d expect, but sailing past the front of my house is a nice touch!

We stayed at the Comis Hotel just outside Douglas, a lovely spot but on the expensive side; it was Manx TT build up week, so they’ve got you…

The first morning as a little misty, but what can you do. You can’t control the weather, so we set off for some exploratory runs on the roads, but it was too misty to really put your foot down until later in the afternoon. So, coffee it was.

In the afternoon it cleared and boy, was it worth the wait! The mountain road was still a bit misty at height, but the other roads, lower done. They. Were. Awesome. The Emtron KV12 Traction Control was .. epic! You can just hear it pulling some timing back in the video below. It was relentless. And the CANTCU controlled ZF8HP70 was superb up and down the gears, it made the pace effortless.

On the last runs of Thursday, up the north west side of the island, the bottom part of the rear wing decided to leave the chat at north of 140mph, and the bottom part decided it still liked me, but it was flapping too much for comfort! Off to the hotel, some hand tools I’d brought and off it came. It left the rear of the looking a little odd!

Fair play to Rival Worx, though. The issue was reported and a fresh wing, under warranty was made and sent out. They stand by their product. It was just one of those things. At least it never caused any other damage, other than to my sphincter.

This brings us on to the main issue with the Isle of Man. Fuel! Weak 97 RON and no E85. Nightmare. And considering the 3.4 at 2.1bar does love to consume fuel, it wasn’t ideal. Especially around 7-8000rpm. The full tank I brought from home lasted a day and a bit. So you’ll either need a standard car, or something that has the secondary maps for 97RON. There’s a resonable supply of fuel on the island, the bigger stations are near Ramsey and Douglas, but you will find them sporadically placed around the island and the price is comparable to home.

I think I’ll be bringing some octane booster with me next time. Given the VP Racing Octanium Unleaded will treat 38 litres of fuel per bottle, and improves by 7 points, I’ll probably end up putting 1.5 bottles in per tank full.

It’ll probably cost £100 extra over the course of a 3-4 day trip, but I don’t get to have 914whp on pump let loose than often! And on an engine build like this, protection is something you absolutely want.

Also, I’d just want to point out the new wheels, with Continental Sport Contact 7 tyres. Not as much outright grip as the A052, but it meant I wasn’t finding religion every time we found a little piece of damp or wet roads. A brilliant all round tyre, and ideal for extended trips where you might encounter some inclement weather.

The final morning was a couple of runs through the Mountains, and going back for the final one as a passenger in Eddie’s 718 Cayman GTS4.0 in Jewish Racing Gold, we found the road was closed. We waited for 35 mins before it was time to go back to the hotel, get our bags and head to the ferry to come home.

Isle of Man, we’ll be seeing you again. Soon. Very soon.

The post Mk4 Supra | Isle of Man 2026 first appeared on BlownByTwins.

13/11/2024: Current Specs for Supra VVTi

Overview & Quick Specs @ 13th November, 2024

• Engine: 2.6l I6, single turbo
• Horsepower (bhp) and Torque (Nm): 355bhp& 338lb/ft.
• Top Speed: 160mph
• 0-60 mph: 6s.
• Weight: 1530kg
• Transmission: A340- 4 speed

Detailed Specifications & Modifications

• Engine & Performance:
  • Intake: Stock
  • Exhaust: 3″ decat
  • Forced Induction: Stock twin turbos.
  • Fuel System: Stock.
  • ECU: Stock
  • Other: Stock
• Drivetrain & Transmission:
  • A343E tiptronic
  • Stock A02B differential.
• Suspension & Brakes:
  • Suspension: Lowering springs on OEM shocks -20mm
  • Brakes: OEM.
• Wheels & Tyres:
  • Volk GT7 – 19″
  • Michelin Pilot Sport 4S. 265/35/19 all round.
• Aero & Body:
  • Stock with rear wiper delete
• Interior & Tech:
  • JC Clubsport Rear Seat Delete
  • Stock interior and trim

The post Supra VVTi | Latest Specs first appeared on BlownByTwins.

I went down to JC Clubsport in Herefordshire to have my car templated as the first MkIV Supra that they’ve built a rear seat delete package for. Straight away, it was a doddle to deal with them. James, the founder and owner, was very commuicative. We set a time, and I went down (early start from the shores of the River Mersey) to their HQ, and thankfully it was a lovely sunny day once the morning fog had burned off.

The trim and carpet was removed to reveal the bare metal and boot surrounding trim in the car, and this is where the massive amounts of measuring started. Everything was measured, checked, trimmed and checked again before a cut was made – and at each point I was kept in the loop and given options and choices regarding how it could work based off their previous experiences in templating over 300 other makes, models and variations of cars.

Once the measurements were completed and the first cuts were made, each again was double checked and iterated on.

With the cuts all being in place, it was off for trimmings. I chose the OEM carpet match, despite wanting to be different, I don’t want to be THAT different. For the netting and the bar, I chose the carbon and the blue netting. Unfortunately, JC didn’t have a carbon bar in stock, so that’s coming up to me in the next few days, but suffice to say, it still looks great with the black temporary bar.

Another nice touch is the bungee fasteners on the netting, which gives me a nice little secure cargo space for anything that could go flying around the car!

I’m very, very happy with how this turned out, and it was great to meet James and his team and see their tireless measuring and iterating around to make sure things are perfect.

The post Mk4 Supra – Rear Seat Delete first appeared on BlownByTwins.

Saturday, 27th July 2024, what a long day, but totally worth it. I had to drop the R34 GTR at The Exhibition Centre in Liverpool for The Ultimate Show, then my mate Big Paul (ironic name) came to collect me and take me down to Nottingham to collect the Supra. We arranged a collection time of 4pm, and then I head south to Watford Gap to meet an old friend for a coffee and give the car a run before heading home for 10pm. 220 miles of blissful driving in my new toy. I forgot just how good they are, and how much stronger it pulls above 4000rpm. I can’t wait to start the modification route with SRD Tuning.

When I arrived at the previous owners house, I was immediately greeted with the extensive history, and the receipts for pretty much anything that has been done to the car in the UK ownership. We went through this when I went to view it anyway, but it’s reassuring to see. Although the sight of a certain “respected” tuners name in the file sent a shudder – although it was from the import and not for work. And it was a long time ago. Even though, their name is on the license plate. Suffice to say, a new plate was ordered immediately and is in the post as we speak. Wye aye, I’d not let that place tune my piano, pet. And I don’t have a piano.

Once we’d done the paperwork, and had a look around the old owners new car, it was time to leave. Or was it? No. Battery. He’d had it on trickle charge and forgot to turn the plug on! Mortified, but we got a laugh out of it. Jump leads to the rescue. 5 mins and it started first time. We left it running, shook hands and both agreed it was a pleasure to deal with each other – see, I can be nice!

I head off to Watford Gap to meet Peter, and found a Shell petrol station around 30 miles away. Plenty of distance to put a good charge in it. The fuel was low when I arrived at the Shell, and I totally forgot about the 70 litre tank. That was an expensive, but equally brilliant stop.

The 56000th mile clicked over on this journey and all was going well until the traffic built up just before the Watford Gap services turn off. That gave me 5 mins to play with the stereo. Yep. Definitely upgrading that.

After leaving Watford Gap, leaving the car there for just under 2 hours, chewing the fat, it was time to go home. Two words: very smooth. The car is only a 4 speed auto for now, with 390bhp. But it can delivery it nicely and it makes it a really nice motorway car, albeit quick and relatively thirsty. But it drives well, no noises, very few squeaks and rattles – nothing that some soundproofing won’t cure.

As night fell, the lights came on, I think. The stock bulbs in the Supra are ferociously crap. That’s already been remedied, with LED bulbs on order all around – thanks to Auto Bulbs Direct for relieving me of £295. But, I remember from my last car, just how much better night time driving became. And this will be the same – but it says a lot when I ordered the license plates first!

I got home and I was still giddy.

Isn’t she lovely. Side view, no license plate!

The post Mk4 Supra – It’s Home! first appeared on BlownByTwins.

I’m not sure what the initial plans are, or when, but it’s going to be a journey and make a car for life for me. The Supra is one of the cars I regret selling the most, so now I’ve got another, I’m so happy to restart that journey. Not sure where the destination is though.

One thing I do know is that I’m not making a “race car”. I’m making a fast, sensible, comfortable long distance GT car.

It will get more power, though.

Arriving here on the 27th July, so watch this space!

The post I did a thing … first appeared on BlownByTwins.