A certain Mr. Coleman took a spin in the car. Being the suspension guru that he is, he felt the suspension damping in Sport mode was too stiff for the bumpy sections of ACH. A quick turn of the Sport Chrono dial to my Individual mode put the suspension into Normal mode. The body motion became a lot more stable on the bumpy sections with the suspension damping softened up and Mr. Coleman worked the car right up to the highest lateral G the car has ever seen; the max I had hit previously was 1.22G. By the way, he loved the factory GT4 short shifter that comes in the T.
I don’t like magnetic phone holder things. And my Pixel 8 wouldn’t sit in the cup holder by itself without falling out, so I designed a phone holder that goes into the cup holder using Autodesk Fusion. It’s amazing what tools are available basically for free; there is the cost of your personal info. I used a nominal 0.1mm clearance all the way around, so 0.2mm nominal in X and Y directions. The phone slid in snuggly with this clearance. And then I charged the phone which made it hot and the phone grew. Then it didn’t want to go back into the phone holder until after it cooled back down.
Later, I dropped my phone and slightly cracked the outer shell. So then I bought a thin phone case and now the phone stays put in the cup holder as-is. At least I got some experience using Autodesk Fusion.
After having spent more time in the car, I noticed a higher frequency exhaust wail that I only hear when driving next to a wall. It reminds me a bit of external wastegate dump, but much lower in volume. I don’t think the stock exhaust tip sounded like this? You don’t hear distinct exhaust pulses, it’s more of just a constant jet noise. I attempted to capture the noise by driving through a tunnel using just my GoPro, so the sound quality isn’t great. The wind noise starts to get a bit loud halfway through send gear. This tunnel is up around 7000′ of elevation, so the car isn’t quite as quick up there.
I decided to do a reliability mod which is to plug the vacuum line to the water pump. Doing so will mean the car will always take longer to warm up as it prevents the shutter from closing in the water pump, but I was already doing that by always starting the car in Sport Plus mode. The failure that occurs is a seal failure between the coolant section of the water pump and the vacuum section which moves the shutter up and down. I believe one of the causes of accelerated seal failure is running the car in Normal mode which keeps the coolant around 101C-104C. Rubber typically degrades faster at higher temperatures. Sport Plus keeps the coolant around 85C. Once the seals degrade enough, applied vacuum to close the shutter can suck the coolant past the seals and into the vacuum line system.
8 comments
Khiem-
I have admired your many articles, and enjoy reading and rereading them. The title of this one sounded interesting, and the explanations, pictures, etc. were keeping me engaged, and then you casually drop that “a certain Mr. Coleman” drove your car. With you along for the thrilling ride, I assume. I’ve been onboard with Mr. Coleman’s writing, storytelling, and engineering prowess since I picked up my first issue of Sport Compact Car in late 1998. Yes, a 200-plus-page tangible magazine; remember those? I’m currently shopping for a car (a tree fell on the current ride), and that same certain Mr. Coleman is a major factor in considering the Mazda3 that I’ve been eyeing. Sorry to hijack the comments, Khiem, but I really wanted to give a shoutout to him. I hope that was alright. Thanks again for the always enjoyable and educating articles. Enjoy the drive!
I loved reading all things Dave Coleman as well! I wrote a question into SCC when I was in college and he answered it! I love Mazdas; I have a base model 2016 CX-5 that just turned 90k miles. I recently took it on a road trip with one of my dogs hitting up some of the best roads in California and it was still fun. I had to put the auto transmission in Sport mode on some sections and the transmission shift strategy was great for the twisty roads. Of course in manual mode, it has the proper sequential shifter orientation of downshift forward, upshift rearward. Lifetime average of 27mpg driving around LA. I literally just had a brand new Mazda3 sedan for a rental car and got almost 39mpg over 350 miles of mostly two-lane cruising. A lot of new cars have lane keep assist which is very annoying. Dave helped make the system be as minimally annoying as possible. The only thing that’s not optimal is the brake pad compound which doesn’t have a ton of initial bite. Though it is an improvement over a CX-30 I drove a couple years ago, but not as good as my 2016. Seems to be a bean counter change. Dave can’t fix everything. I’ll recommend anything in the Mazda lineup if you’re looking for a driver’s car.
Doing some research suggests these vanes improve front downforce and don’t do much for the rear diffuser.
https://images.squarespace-cdn.com/content/v1/5d7cfd7b13f6f06e8b55ed5c/1609096469910-BUNFCV10FN32JTZGA418/graphs.jpg
I’d found that before too. I do think it is vehicle/overall package dependent. The only thing I know for certain is that they direct air from the middle of the car outwards. I vaguely remember reading somewhere they also interact with the air swirl coming off the front tires which helps clean up the underbody airflow. I think acting as an air curtain to prevent the dirty air off the front tires from going under the rear.
This link is to an artist representation of the airflow under the GT4RS with the more extensive turning vanes array underneath the car. It does show the vanes redirecting the air outward right into where my rocker panels got hammered. Huh.
https://press.porsche.com/prod/presse_pag/PressResources.nsf/Content?ReadForm&languageversionid=1289808&hl=modelle-cayman-718_cayman_gt4_rs
My 718’s rocker panels aren’t as peppered with rocks like your is. But the under panel definitely is.
Never understood why my 718S water pump started leaking at 20,000 miles and 3 years. Makes sense. Thanks for your 718 articles, they’ve been great reading! PS I have the APR tune and wish I tried the AP…
If the car is bone stock, I think APR is a best option. It’s when you start modifying things where the pro-tune has benefits.
Very good article post. Thanks Again. Keep writing.