Lotus Europa 16V Gordini

[MRN I J]

A K series has an 80mm bore & one is on its way to me to borrow
MX5 or Miata's are plentiful in the breakers, available in 78mm bore as a 1600 cc and one is in the Mrs's Miata's so time to put a tape measure on them

[GavinT]

I recall Richard Hill did a K series conversion . . using the whole engine.

Probably a good start is to offer up the head gasket of the potential donor head. It's often found that head bolts and water jackets aren't far out because the same engineering determinations for similar engine sizes apply across the board.

Toyota 4A-GE cylinder spacing is 89mm (same as the Renault) and has an 81mm bore.
Head capacity is 36cc
(pics below)

Most of the later 4A-GE's come with TVIS (Toyota's variable valve timing) and there's also plenty of aftermarket stuff available for these things.
Need to figure out the ignition, BDA and oil delivery/return - perhaps a dry sump.

Not a weekend project or for the faint hearted but people do this stuff all the time.
Lots of grist for this mill.

[MRN I J]

I recall Richard Hill did a K series conversion . . using the whole engine.

Probably a good start is to offer up the head gasket of the potential donor head. It's often found that head bolts and water jackets aren't far out because the same engineering determinations for similar engine sizes apply across the board.

Toyota 4A-GE cylinder spacing is 89mm (same as the Renault) and has an 81mm bore.
Head capacity is 36cc
(pics below)

Most of the later 4A-GE's come with TVIS (Toyota's variable valve timing) and there's also plenty of aftermarket stuff available for these things.
Need to figure out the ignition, BDA and oil delivery/return - perhaps a dry sump.

Not a weekend project or for the faint hearted but people do this stuff all the time.
Lots of grist for this mill.

The K series is a jewel of an engine once built properly & there are still so many parts available for them, 1.4 through to 2 ltr, 230 bhp is easily acheivable.
The KV6 is presumably as tunable, QED have built some

[Mecky]

The final test for my modifications and improvements to the car took place last Thursday in Zolder, Belgium, and what can I say? I finally have a racing car. The car now accelerates, steers and brakes for the first time to an extent that does justice to the premises of 162 hp, 740 kg and 225 mm wide semi-slicks.

Accordingly, I was able to break the 2-minute barrier for the first time on the brake-killing track in Zolder. I am relatively sure that there is still some room for improvement for me. A pro could certainly get more out of it, but I also see room for improvement on my side. Maybe even a whole second. I have the feeling that I'm still braking too early and too much in some places.

The only downer was a very abrupt spin right on the braking for the first corner, which I couldn't avoid. Before I knew what was happening to me, I was only a passenger. Just as I was thinking about turning in, the inside rear wheel apparently locked up and I immediately lost control. Here is a video of this spin: https://youtu.be/V-YlW0TTYUc

At first, brake balance came to mind as a possible cause. But if you look at the wear of the brake pads, it's clear that the front brake is working much more than the rear. I don't want to adjust the bias more towards the front axle, if I can havoidelp it. The front pads are about 3/4 worn after 34 laps in Zolder. The rear ones, on the other hand, just about 1/4.

Two further approaches to combat this unpredictable danger of spinning under braking:

1.) Change the damper setting so that the car dives less drastically at the front. To do this, the front axle in particular would have to be set up harder. If necessary, I will also soften the rear a little.
2.) A limited slip differential, which prevents the rear wheels from having too great a difference in rotation speed.

I will first adjust the suspension and then - if necessary - also the brake balance. A limited slip differential is still a far away at the moment.

Here are a few pictures:

[Mecky]

Today I investigated the brakes. I had mistakenly thought that the front and rear brake pads had the same compound. However, at the front I had the brake pads supplied by Banks from England (manufacturer Juratek). These are about 80% worn, whereas the Ferodo DS3000 on the rear axle are only about 30% worn. The Banks pads are much cheaper than the Ferodo pads, so I assume they are of lower quality. I'm optimistic that the Ferodos will last longer.

My conclusion (in the last post) about the brake balance was based on the assumption that I'd have had the same pads on the front and rear. If the same pad compound wore much more at the front, that would be evidence that the brake was doing more work at the front. But the pads were not the same compound, so I guess it does make sense to adjust the balance. Now I have adjusted the brake bias slightly forward after all. I'm also going to adjust the suspension to make the dive of the car a little bit less drastic when braking.

Regarding the spin: I analysed the video frame by frame and my first steering movement on the way to the left-hand bend was to the right. So you can say that I wanted to correct the spin even before I turned in. In other words, the left rear wheel locked, although it was not yet unloaded by the turn-in. A very dangerous situation. In the race, I probably would have wiped out three other cars. Fortunately, it went well this time. So now I'm going to work on it by adjusting the brake bias and the damper settings.

[jbcollier]

Even with the same compound, you will not get the equal amounts of pad wear front to rear.  The front brakes do most of the work due to weight transfer.  The rears do very little.

[cazman]

Which kind of rear brake set up do you have?

[GavinT]

Agree with JB - I wouldn't expect pad wear rates to indicate anything much.

Looking at the video, the rear right seems to have lost traction on the ripple strip of the two right handers prior to the spin. And by that, I mean lost traction for longer than I would have expected.

I reckon moving the brake bias forward is worthwhile from what you say.
If this was my sons 1/10 scale RC car I'd also be looking to harden up the front or soften the rear . . but one thing at a time.
Brilliant video, though - well done. 

[Mecky]

Hi guys,

of course you are right. The front brakes should do the main work. As the Europa is quite light at the front, I aimed for a 60:40 ratio between front and rear, when I designed the rear brake. This is round about the dynamic axle load ratio, which I estimated under braking. With front engined cars, it would be more in the direction of 70:30 or maybe even 80:20.

After checking the brake pads thoroughly, I found that the wear is really as follows:

   - Front pads (Juratek / Banks): 70 % - 80 % worn
   - Rear pads (Ferodo): 10 - 20 % worn

I have now gone through my braking system design calculations from last year and I found that I have not taken the brake pad area into account. I have just assumed that the front pads would have a bigger friction area compared to the rears. Of course my front discs have a bigger effective radius (5 % bigger), but the pad area of the rears is bigger (about 10 %). That means that the bigger pad area at the rear overrides the bigger radius at the front. Nonetheless, I have given the fronts the smaller master cylinder (0,625 "), which makes the hydraulic pressure higher than in the rear master cylinder (0,7") (slave cylinders are same dimensions). Bottom line, the fronts should still work more compared to the rears. But as the spin has shown, the bias needs to bet set even more to the front. Maybe, I'll also have to go for a bigger rear master cylinder (0,75"), in order to decrease hydraulic pressure inside that one. This would shift the bias even more to the front brakes. Before the next race, I'll definitely purchase a 0,75" master cylinder to play it safe. And I will also adjust the shocks. The fronts are very soft right now.

@jb: You are right. But I was thinking, the compounds were the same. That made it even more useless to try and evaluate brake bias based on wear of pads.

@Gavin: That's right. I lost traction, because I don't have a limited slip diff.

@cazman: I use an Opel Kadett front brake for my rear. You can see it on the photo below.

[GavinT]

I have now gone through my braking system design calculations from last year and I found that I have not taken the brake pad area into account. I have just assumed that the front pads would have a bigger friction area compared to the rears. Of course my front discs have a bigger effective radius (5 % bigger), but the pad area of the rears is bigger (about 10 %). That means that the bigger pad area at the rear overrides the bigger radius at the front.

Hi Stefan,

Brake pad area doesn't matter; it's the piston area that determines braking force (among other things).

Richard H, a member here, who has brake system design experience put together a spreadsheet for calculating this stuff.
You may be interested to see how it compares with your existing calculations.

Here's a link to the thread where you can download his spreadsheet at Reply #4.

http://www.lotuseuropa.org/LotusForum/index.php?PHPSESSID=1hqntqdies05g3mo4d8eobio00&topic=2437.0

I wonder if a proportioning valve might not be a consideration even with a tandem MC set up.

[jbcollier]

Brake pad area may not matter with regards to braking force but larger pads will take a greater heat load than smaller pads.

Racing set-ups with two master cylinders should have adjustable balance.

[Mecky]

You are both right guys, I had just found a formula in a book and interprated it wrong. The pad area is not important for the braking force directly. It's important for heat transfer, which determins the friction coefficient.

I have now gone through the theory one more time and calculated the set-up how it should be. I have just done a rough estimation, when I did the rear disc conversion, with a target braking force distribution of 60:40, so that it can be fine-tuned with the balance bar. I calculated now, that my result in reality was 57:43, which was enough to let me spin heavily. In a race, I'd maybe have crashed into several other cars. So, the test day brought me a lot of important information and may have saved me a lot of money.

Now I have calculated a braking set-up, which should be exactly equivalent to the (estimated) dynamic load distribution of the car under braking (63,5:36,5). This time, I'll give it a bit of safety margin in favour of the fronts, in order to avoid such a spin in the future. If the rear is still unstable under braking, I have two more alternatives, which I'll bring to the race track: a bigger master cylinder for the rear circle and a pad compound with lower friction coefficient for the rears.

[GavinT]

Stefan,

Does your balance bar have a cable system allowing adjustment on the fly?

Also, just curious but are you able to induce understeer when exiting a slower corner?

[Mecky]

Unfortunately, the balance bar has no adjustment cable. Under the regulations, which I used to race, it was not allowed. Today it is allowed, but I don't have the resources to change it right now. The balance will have to be replaced for this. I guess, I'll do this, when I go for a top mounted racing pedal box from AP Racing or Wilwood.

Understeer was almost never an issue with this car. The only time, the car tend to understeer, was after my crash at the Nürburgring, when the lower wishbones were slightly deformed. With proper wheel alignment, the car steers very neutral with a very slight tendency towards oversteer.

I'm not saying that it's impossible to induce understeer out of slow corners, but I have not experienced it recently.

[Mecky]

I was in Zolder last weekend for the first round of the BELCAR Historic Cup 2022, and what can I say? The car may have been on the race track since 2011, but it became a serious race car this year. It's still far from perfect, but finally the basics are right: engine, cooling and brakes are consistently powerful and reliable, even under heavy stress.

After the test on 21 April on the same track, I knew that lap times below the 2-minute barrier are repeatedly possible. In both qualifying sessions I only achieved 1:59 times, although the sector times were sometimes good for more. Unfortunately, I didn't get the lap together. So I qualified for grid positions 36 (race 1) and 34 (race 2) out of 47 participants. For the fact that the Lotus Europa starts in the smallest displacement class and is one of the oldest cars, I thought that was OK.

The first race was started on Sunday morning at 10:15 AM with already bright sunshine and almost 20°C. It went well from the start. I was able to fight my way up the order out of a group of four against much more modern cars and pull away from this group. Then the race went on for a while until a Mercedes 190E went off the track in turn 1 and the safety car came out. This brought the field back together and suddenly I was within striking distance of the class leader, who had started the race from 27th position. After the end of the safety car phase we drove right behind each other, but both had to fight with lapping cars from behind, so there was no real fight for the class win. But at least I was able to finish the race within striking distance in second place in class. In the overall classification, I moved up to 22nd place. I even managed to leave the two Ford GT40s behind me. I only overtook one of them in the third last corner of the race. My best lap times were 1:58.1 min, which is eight seconds faster than my fastest lap in 2021.

The second race took place in 27°C and blazing midday sun. Unfortunately, I completely missed the start and immediately lost connection to the field. I also quickly noticed that the cars that I had been able to overtake in the morning were getting away from me this time. My best lap time was 2:00.8 minutes, almost three seconds slower than in the first race. The reason for this is not yet clear to me. On the one hand, I was worse myself, on the other hand, the tyres were perhaps not in the optimal window. So I came to terms with the situation and went on with my race. The Porsche 911, which I only saw briefly in the rear-view mirror on lap 1 of the first race, was now my opponent, but I couldn't get past. After about 8 or 10 laps of fighting, however, he made a mistake and spun in front of me in the small chicane. From now on I tried to just nurse the car to the finish, but it turned out differently. On the last lap I got slight vibrations under full load on the back straight and before the last corner the engine lost power completely. The temperatures had been stable until the end. So there was no severe engine damage to worry about. Only the fuel pump stopped working. So I stranded in the last chicane in 29th place, within sight of the finish line. Hence, I was completely eliminated from the classification, even though the 30 minutes of racing time had already gone past. C'est la vie. At least no serious damage and I still have a fuel pump in stock.

I'm already registered for the next race on June 26th in Spa-Francorchamps (Spa Summer Classic). After this race, the car will probably get a limited slip differential to be faster on tight courses like Zolder in the near future.