This site is finally back up! Well ... sort of.

For those of you who couldn't care less, and just want access to the old tech articles, rants, and various wanderings, you're in luck because we have decided to re-post all the old information along with some new stuff just to keep you from getting bored.

And finally, if you came here looking for Motec products, we are still a Motec dealer, but we do pick and choose our projects as Injector Dynamics is still our main focus. If we can't help you, we will be happy to refer you to a Motec dealer that can.

So what can you expect to see here in the future? As I mentioned, the old tech articles will be re-posted, and aside from that this will become a repository for various technical wanderings.

To those who have sent emails ranging from nice to downright nasty, thanks for the shove. I didn't realize that my writings were viewed, much less appreciated by that many of you. Without your harassment over the last year I would probably not have re-activated this page.

This new page will be a blog type layout focusing on whatever vehicle I am currently using for testing and development of Injector Dynamics and Motec products.

It may also occasionally feature one of our pet Motec projects, like the RX-7 seen here.

This is Glen Jung's RX-7 currently powered by a naturally aspirated peripheral port 20B. I have always had a thing for this car, and since I got the call to sort out the Motec system for the 2008 SCCA Runoffs, I have been licking my chops waiting for the switch to a 3 rotor.

The car got the extra rotor for the 2010 SCCA Trans Am season, and I admit to having way too much fun noodling with the engine management.

Here's a shot of Glen and I in the garage at VIR. At first glance, it looks like two guys having a discussion over a race car. Presumably discussing super secret Motec trickery known only to an enlightned few.

Upon closer inspection, it is a study in human evolution, or maybe devolution if such a word exists. Note the posture of both participants and ask yourself which of the figures below provides the closest match...

Somehow this race car had taken us all the way back to cro magnon man where our only thoughts are: "Should I kill it, eat it, or try to hump it?"

BTW, this car sounds really cool.

More Later - Thanks for tuning in.

PY

October 19, 2010 - The First Post

So here it is, the first post on www.yawpower.com version 3.0. As I mentioned above, the subject matter will be technical in nature, and mostly related to my current test vehicle.

So what's the current test vehicle/guinea pig? A 2002 Mazda Miata.

Why? I've answered that enough times now that I'm getting pretty good at it. It goes something like this:

Joanna decided that her beloved Miata with it's rough ride, mediocre air conditioning, and crappy stereo was too small to take both dogs to the vet at the same time, and so she needed an SUV.

Lucky for us, the federal government and their partners in crime (Otherwise known as "The News") were busy ass raping Toyota over some bullshit called "Sudden Acceleration" and so the dealers were practically paying people to take them off the lots.

After the shortest negotiation ever, we left the dealership with a Toyota RAV4 which will carry both dogs, groceries, a cooler full of beer, a tandem bicycle, and do it with ice cold air blowing in your face and gas mileage that is only marginally worse than the cute little Miata.

As it turns out, all 6'2" 220lbs of me fits comfortably in the Miata, so I started driving it to work. And bitching about the rough ride, mediocre air conditioning, and crappy stereo. I also started bitching about the vibratey no power making 4 cylinder lump under the hood.

Now you can say that I'm being ultra critical, but when my RX-7 delivers more off idle scoot than this piston powered 2350lb car, something's in need of improvement. Or at least deserving of constant ridicule and belittlement.

While using the car as a daily driver and pretending to hate everything about it, I bought a set of used Rota wheels from a friend, updated to all the latest underbody bracing, bought 2 sets of Bilstein shocks, (One set to drive around on while the other set was being analyzed/revalved) dug up all my old notes and spreadsheets from a several year old SCCA EP suspension project, and dyno'd the stock shocks to figure out why the car had such poor ride quality.

In the process of road testing some updated shock valving, I decided to put the top down and an amazing thing happened. All the shakes and rattles went away. And I mean all of them. Suddenly I was driving a solidly built rattle free car, and realized that I had been trying to "fix" the convertible top with the shocks.

Wanna guess what happened next? Yup, I ordered a hard top. For what I had spent on this car already, I could have made a down payment on the Lexus IS350 I had been eyeing. But what fun would that have been?

And so now it all comes to a head. After a couple of failed attempts at a good color match (Mazda delivers their hard tops in primer) and a lot of time wasted determining what latches and hardware I needed, I drove to the paint shop and installed the hard top for a drive back to the shop.

Holy Shit! Suddenly I liked this car. The rattles and shakes were gone, the AC worked much better, and the reduced wind noise made the stereo listenable. And I haven't even mentioned the cars finer attributes, like the fact that it is the most pitchable car on the road.

Fact is, you can drive this car like an absolute lunatic at nearly any speed and it will always do exactly what you tell it to do. No surprises, just a substantial amount of grip and superb predictability.

So why does this car deserve to be the latest test mule? Well...the addition of the hard top did nothing for the measly power output and a quick browse on the internet showed that 2002 was the first year for variable cam timing.

And how often does any tuner get to fully sort variable valve timing? C'mon, be honest, do you really have a customer that's going to pay you to optimize cam timing beyond full throttle and maybe a brief foray into idle and cruise quality?

More importantly, I finally have a reason to use the 4D fuel and ignition mapping available in Motec's V3 software.

Before we get to 4D mapping, lets take a look at the shocks. Specifically the OE, and Bilstein HD shocks.

But first I need some rest, so the cool graphs that I generated earlier tonight will have to wait until tomorrow, or maybe even the weekend. (Cliff hanger...)

More Later - Thanks for tuning in.

PY

October 20, 2010 - Does Someone at Mazda Have a Broken Calculator?

I mentioned above that the perceived poor ride quality was mostly due to the convertible top shaking and rattling uncontrollably.

Still, the shock valving felt less than ideal, and it seemed that the majority of the disturbances came from the rear suspension. So much so that I felt the rear shocks were stiffer than the front. At least in the high speed compression range. At crazy as it seemed, the butt dyno was pointing me in that direction.

No matter how they were valved, the stock shocks had to go, and so I needed a reasonably priced shock that I could play with.

As many on the internet have already pointed out, Bilstein makes an inexpensive shock that can be revalved easily, and as long as you can deal with the limited piston choices, you can do a lot with them for very little money.

They also have a rubber bottom mount which is nice for noise reduction, and the upper stem fits directly into the stock rubber upper mounts, also nice for noise reduction.

And it's worth noting that the Bilstein build quality is exceptional, much better than the brightly anodized crap coming from China.

I ordered 2 sets of Bilstein HD shocks, and bolted one set on the car with the stock springs. On the drive home a few things were apparent.

First was that there was more rebound damping, especially in the low speed range and this made the car feel more planted and controlled. A little more like a go-kart. It also felt a little overdamped, but all in all it was an improvement in feel even though the ride seemed a bit more harsh.

The most noticeable thing though was that the rear stiff character of the car had not changed at all. If anything it seemed more noticeable. At this point I would have bet money that the rear shocks were stiffer than the front, but I could not imagine that both Mazda and Bilstein would offer the same strange valving.

The next day the second set of Bilsteins went on the dyno so that I could see if I was crazy or if Mazda and Bilstein were crazy. The chart below shows the shock dyno results.

As you can see the rear shocks have considerably more low speed rebound damping and the compression has a steeper slope which will be more noticeable at high velocities such as those seen hitting sharp edged bumps, making the car feel harsher and more abrupt at the rear.

As is usually the case, there is more to the story, and as I like to remind everyone around me, a little bit of 5th grade math will normally paint a clearer picture.

Very few cars have the same motion ratio front and rear, and the Miata is no exception. According to my notes, this car has a front motion ratio of 1.51, and a rear motion ratio of 1.36. This means that at the rear for instance, the wheel will move 1.36" for every inch that the shock/spring moves.

This motion ratio is a product of the shock mounting points and overall suspension geometry, and the result is that the wheels have substantial leverage over the shocks and springs. Most interesting in this case is the fact that the front wheels have more leverage over the shocks and springs than the rear wheels do which makes the rear of the car considerably stiffer than the front for the same spring rate/shock valving.

So how do these numbers from the shock dyno translate after we consider the difference in motion ratios?

The chart below shows the force and velocity at the wheel as compared to the first graph which showed force and velocity at the shock shaft with no suspension "leverage" taken into account. In other words, this is what you really feel, and is descriptive of how the shocks actually affect the car.

There's not much left to say as the graph illustrates that the rear shocks are in fact considerably stiffer than the front.

And while there may not be much left to say, there sure are a lot of questions to be asked. For instance "What the fuck were they thinking?" At least that's the first thing that popped into my head.

So now we go to the stock shocks for an even bigger surprise. I tested all four on the dyno and guess what? They're all the same. As in the front and rear shocks have exactly the same valving.

Since we already know how the motion ratios affect the installed rates, I plotted the stock shocks as force vs wheel velocity skipping over the meaningless shaft forces plot.

I have no idea why Mazda did what they did. Maybe it was to give the car a more responsive feel, maybe it was to offset the poor front steering geometry and get it to point in better, who knows.

Considering that the front and rear shocks are EXACTLY the same I suspect it was just convenient, and the results did not interfere with any of their major design goals.

How Bilstein got there is not hard to figure out either.

With all the shocks in their catalog, they cannot possibly take the time to plot the cars geometry, masses, rates etc and then arrive at an engineered decision. It would be too expensive.

At the end of the day it is much easier to dyno the stock shocks, and make a few global changes that are sure to be well received without changing the overall balance of the car.

The chart below compares the Bilstein and OE shocks.

The trend is clear. Increase total low speed damping for a more direct feel, increase rebound damping about 50% to allow for a range of stiffer springs while maintaining similar rebound and compression slopes, and put it in a box

I have no real insight into their design approach, but it's hard to believe that both Mazda and Bilstein put serious effort into this and came up with the same ridiculous results.

And before you fire up your email program to send me a "Stop Bashing the Miata" email, relax. It's just a car. A car I happen to like a lot in spite of a few flaws.

Fact is, almost all cars are built to a price point, and compromises have to be made. In my opinion Mazda made the right compromises and came up with a very cool car.

And if the car was perfect none of us would have anything to play with right?

OK, enough of that.

I could go on and on about shock valving until my fingers cramped but it's late, and I will revisit this topic at a later date.

The next post will cover what I found while monitoring the cam timing under various driving conditions.

More Later - Thanks for tuning in.

PY