FWD vs. RWD in the rain?

A recent comment from an old post sent me down the path of attempting to quantify the difference between FWD and RWD in the rain. How much faster is FWD? A little? A lot? Here’s my first quasi-quantitative attempt at answering that question. I’ve taken a bunch of graphs from SpeedHive from the Lemons Thunderhill event in 2019 where it rained suddenly on Sunday. In the images below, you can see the lap times get slower as a “swell” in the graph. If there’s a big difference between FWD and RWD, the swell for FWD should be much smaller than RWD.

FWD Acura Integra

RWD Mazda Miata

RWD Lotus mongrel

FWD Hyundai Elantra

RWD Mazda Miata

RWD Porsche Boxster

RWD BMW E30

RWD BMW E30

FWD Dodge Neon

RWD BMW E30

RWD Mazda Miata

RWD Toyota Celica

AWD VW Vanagon

FWD VW GTI

FWD Hyundai Accent

RWD Mazda RX-7

I don’t see much difference between the swells of FWD, RWD, or the one case of AWD. This is just a random selection of graphs though, and maybe with a larger selection I’d see the trend. Here’s the last graph showing our Toyota Yaris. Note the Y-axis! We had a 35 minute stop, which has the effect of making our rain laps look better than they were. But of course we did rock in the rain, as evidenced by the video linked below.

Post-race analysis: drivers

Let’s take a look at some of the telemetry traces of the Triple Apex Racing drivers from the last race.

Danny vs. Danny

The first thing I want to discuss is Danny. I’m usually a couple seconds faster than Danny. I was on Saturday. Then we switched tires on Sunday and everyone went faster. But was it really the tires? In the speed trace below, Saturday is black and Sunday is red. I’ve displayed the top 3 laps each day. Saturday he was doing 3:39-3:40 while Sunday it was 3:36s. What I see here is that he’s driving differently. On Sunday (red) he started backing up the corners. He gets his braking done earlier and gets on gas earlier. Most of the time, his minimum corner speed is higher despite the change. The fresh tires may have contributed a little to his higher speed, but I think it’s mostly because he’s getting better at driving a low powered FWD car with an open diff. His usual car is 911 GT3, so yeah, it’s a little different!

 

Danny vs. Ian

Due to yellow flags, I didn’t get many fast laps. I did a 3:38 and 3:37 back to back. You can see these starting at the 10:00 mark in my video from the last post. In my 3:38 lap, I lose 1 second passing an E36 in T2 when it changes line mid-corner. Then I pass the yellow Miata in T5, messing up my T6 entry, causing another loss of a second on the run up to 9C. The 3:38 could easily have been a 3:36. On the 3:37 lap, I lose a little time making a pass in T2 and then 1 whole second in T3W while I wait for a fast E36 to get around me. So that too could have been a 3:36. Had I gotten a bunch of clean laps, I’m pretty sure I would have been doing a bunch of 3:36s. Could I have broken into the 3:35s? I don’t know. For the most part, Danny and I drive pretty similarly. Below, the red lines are Danny’s fast laps (as above). The black is my 3:37 and the blue is 3:38. This is a speed trace from 7W to the SF line. We have a slightly different way of doing 1W, but the rest is similar enough that you might think it was the same driver.

Randy vs. Danny

So I’m sure everyone wants to know how fast Randy was (green lines below). Faster than Danny (red lines). Where is he faster? You might expect it’s the fast corners, but it’s the slow ones. He gains nearly 1.5 seconds in T9C alone! And he was only 1.8 seconds faster than Danny. T9C is on the far left of the graph. But he’s also faster in T7W and T11. How? Mostly by running over curbs. As the car owner/builder, I don’t really approve of that.

Randy Pobst is a sweetheart

The Lucky Dog race at Thunderhill was good fun. Ultimately, we didn’t place particularly well, but as we’ve found out over the years, it’s more fun racing for giggles than trying to win. So we were leisurely about pit stops and put some guest drivers in the car. One of those drivers was the Internet celebrity pro driver Randy Pobst. Randy has a reputation as a fast driver but there’s a lot more to the package. He’s very approachable and knowledgeable, and he listens as well as he talks.

FUUUCK. I only had one camera working on Sunday when Randy was driving and it was pointed to the rear.

When Randy got in the car I told him to “bring it back whenever”. Given that he drove it until the end of the race (~60 min), I think I believe him when he said he was having a lot of fun. Apparently the Yaris reminded him of his old 80s Golf. Randy wasn’t the only person who had a great time in the econobox of doom. Lemons veterans “Crazy Mike” and Steve “Chotus” Warwick also drove and loved it. Mike was an “official” Triple Apex Racing driver this race and Steve was a stud driver, piloting some 4 or 5 cars on the weekend. That reminds me of a quote.

I never had a 10, but one night I had five 2s… and that ought to count for something.

— George Carlin

Every time I race the Yaris, it reminds me of why I built it. I love driving and hate wrenching. Despite appearances, the Yaris is a great driving car. It’s also cheap to run and tougher than it looks. It got side swiped twice during the race and just shrugged them off. The one annoying feature of the car is inside wheel spin from the open diff. That’s something I may address in the off season.

Look for some video and telemetry posts in the near future.

Aero Thoughts

I haven’t looked at the data yet, but here’s my seat of the pants impression of what it did.

  • The wind deflectors on the A-pillars did something. There seemed to be less noise in the cockpit. Did they improve top speed? I think so. In the last Lemons race we lost a few mph on the main straight and I think we got that back.
  • The wing probably added useful downforce in T1 and T8. I always take T8 flat out, but this time it was a really boring flat out. In T1, I usually brake lightly, but this time I would just breathe the throttle off for a heartbeat and then go right back on. No brakes needed. That allowed me to make some passes on higher powered cars.
  • The interior of the car still smells a little of catalytic converter, so I think some fumes are getting in from the rear. I want to fix that somehow.

I won’t know if these impressions are correct until I check the data. I’m fully prepared to be wrong!

Thunderhill Ready

Before the last race, I did a lot of lightening. The biggest win was getting an extra set of doors and gutting them to metal skins. While they weigh 50 lbs less each, they leave a larger hole and have no mirrors. That probably negatively affected our drag as top speed was off by 5 mph. Lap times were about the same though, probably due to better acceleration. Since there wasn’t much to do to get the car ready, this weekend we added some features that may improve our aerodynamics.

In the picture below, you can see a white piece of plastic on the A-pillar. This bulges out a little which we hope will deflect some of the air outward, so that the window doesn’t act like a parachute. The plastic is very heavy and shouldn’t move even with high air speed.

I also added a wing to the rear. This is a present Mario gave me that we had at one time installed on the front of the car as a sight gag. Now it’s installed in the correct place with mounts I hacked together. It’s more sturdy than I would have thought. No idea if it works, but even if it doesn’t give much down force, maybe it helps prevent air from the tailpipe going back into the cabin. Or maybe it creates lift and gives us carbon monoxide poisoning. Who the hell knows?

The last piece of our “aero package” is an air dam that I will attach once we get to the track. It will be interesting to compare data from the May Lemons race to see if top speed improves on the main straight and if we get any extra grip in the fast corners.

The only thing I’m concerned about at this point is the rear tires. The 8″ rims aren’t fully covered by the wheel wells. I guess I’ll order some fender flares.

Race Prep: Lucky Dog Thunderhill

The last race of the year for me is just 1 week away. I love racing on the 5 mile track and I love Lucky Dog Racing League. I just checked the supps and was met with a bit of a shocker. At some point I believe this race was advertised as running the second day in the reverse direction, but somehow that changed. That’s a real bummer. I was looking forward to that. Or maybe I’m mistaken and that came to me in a dream. Sometimes I confuse dreams for reality. I have a funny story about that…

I don’t follow politics at all, but early in the Obama presidency I remarked to a friend that I thought it was a really smart that Obama’s VP was blacker than he was. That way people wouldn’t assassinate him for fear of the next guy in line being even more threatening (or whatever). That was something I dreamed because apparently Joe Biden is actually white. Back in the 70s, Saturday Night Live used to do skits where Garrett Morris played Mondale as VP. The joke was that Mondale was so easily overlooked that nobody realized he was black (Garrett Morris). Anyway, I had somehow confused Garrett Morris, Walter Mondale, and Joe Biden. Then again, there are people who would say that Obama is actually whiter than Biden… so maybe I had it right all along. I try to steer well clear of political content on this blog, so apologies for this short political interlude.

Speaking of dreams, wouldn’t it be awesome to get Randy Pobst to drive a stint in my car? Well, it turns out, he’s going to be at the race and he’s going to be driving various cars. I immediately sent an email to HQ to sign up for this, so it may happen. That would be a dream come true. If it does, I’ll be sure to post some video and telemetry analysis. I’d love to see how much better Randy drives.

Prep

As it turns out, the Yaris requires minimal prep, and there really isn’t much to do between races. The car is amazingly robust and simple.

  • Change oil and filter
  • Change front brake pads
  • Swap doors (I keep the ones with windows on when parked)
  • Reinstall fire bottle (I just had it recertified)
  • Reinstall window nets (I had them out for the Lemons race)
  • Pack

So what’s the packing list look like? Some things are large and bulky, like tires, but I also have lots of “kits” that aggregate related items, which makes packing and storing simple. I can generally get everything ready to go in a half hour.

  • Stuff
    • Jack, jack stands, wheel chocks
    • Fuel jugs, fire extinguisher, splash pan
    • Chairs, table, ice chest, EZ-up
    • Tires (see below)
  • Kits
    • Tool box (sockets, box wrenches, gloves, etc)
    • Power tools (impact, drill, air pump, light, vacuum)
    • Spill kit (absorbent litter, brush, scoop)
    • Brake kit: pads, fluid, catch can, brake tool
    • Service kit: oil, filter, funnel, paper towels, glass cleaner
    • Radio kit (UV-5R radios and accessories)
    • Race kit (tire pressure gauge, pyrometer, log books)
    • Telemetry kit (RumbleStrip, AiM Solo DL, Yi cameras, memory)
    • Fix kit (nuts, bolts, tapes, adhesives)
    • Electrical kit (multimeter, fuses, wires, crimper, etc)

Tires

The Lucky Dog Racing League is now sponsored by Hankook, and part of that arrangement is that the Hankook RS-4 is THE tire for the racing series. In order to get on the podium you have to run that tire. Ultimately, this is a fine thing, because it saves money on average. The RS-4 is a great endurance racing tire that has a combination of grip and longevity that is hard to beat. In very rough terms, they are a couple seconds slower than the cheater 200s like the RE-71R, but last 2-3 times as long.

Given that my car isn’t 15 years old, meaning I may get classed in Super Dawg, and is slow even for a C class car, it’s unlikely I will get anywhere near the podium. So the tire rule doesn’t really impact me. That’s good because I have several tires to burn through. This is what I’m bringing to the race.

  • 2 Federal 595 RS-RR 225/45/15 on 15×9 rims
  • 2 Federal 595 RS-RR 225/45/15 on 15×8 rims
  • 2 Hankook RS-3 225/45/15 on 15×8 rims
  • 2 Bridgestone RE-71R 205/50/15 on 15×8 rims

 

The most important corner

Which is the most important corner on the track? Every track has one, and it’s not always obvious. YSAR reader Eric recently shared some AiM Solo data with me that got me thinking about this. The event was last month at Oregon Raceway Park in the Lucky Dog Racing League. While I’ve never been to ORP, I have driven it in simulation (rFactor2) and it’s at the top of my bucket list due to its mixture of elevation, camber, and corner geometries.

Take a look at the track map below and try to figure out which corner is the most important one. While ORP can be driven in either direction, let’s consider the clockwise direction, which follows the black turn numbers from 1 to 16.

The common logic is that the most important corner is the one that leads onto the longest straight. By that logic, T16 and T2 appear to be pretty important. What if I told you that it’s actually T4? Why is a slow corner followed by a short straight the most important corner? After T5, the track goes uphill and is basically straight until T7. So really, what we have here is that T5 is the critical corner that precedes a long straight. T5 is also complicated by having a slightly blind entry. But regardless of the particulars about T5, there’s no way to take it optimally without throwing away the exit of T4. Which makes T4 the most important corner on the track (clockwise anyway).

One of the reasons I was eager to look at the telemetry data was because the team had Randy Pobst drive one stint. I’ve never examined the data from a pro driver, so I was eager to see what he’s doing differently than us amateurs. The difference between Randy and the team hotshoe was about 1 second, and the specifics of those differences are mostly about backing up the corner, a topic mentioned on YSAR plenty of times. When you look at lap times that are 3-5 seconds off, it’s some mix of the following:

  • Mashing brakes
  • Mashing throttle (causes understeer and a lift at the exit)
  • Coasting into brake zones
  • Crabbing into an early apex
  • Sub-optimal line through compromises (the main topic of this post)

Randy is a professional driver, and I don’t expect anyone on my team to match his lap times. I’d be over the moon if someone was within 1 second. Heck, 3-5 seconds off is fast enough on my team.