| MIATA BUILD |
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 | |  | March 1, 2010 - I'm not done with the intake yet, but first I need to play with some springs.
Why? Because the 750 lb springs on the car are borrowed, and they have to go on to a V8 Miata instead. And just today, I got a package from AFCO with my dual spring setup!
With the stiff springs I've been running, I don't get much spring compression with the car's light weight. This means that the spring will unload before the shock is fully extended. Most people think this is bad because the spring can rattle around and they imagine it means it can land crooked. That's not the problem. The problem is that I lose suspension travel. Once the spring unloads, there's nothing to open up the shock except the weight of the wheel fighting against the fairly stiff rebound damping.
The solution, then, is a helper spring. A short, relatively soft spring that is usually fully compressed but helps supply that extra push when the main spring is fully extended. I've run into two problems with this setup. First, most helper springs are just a little bit undersize in their inner diameter. AFCOs are set up for 2.625" springs but can run 2.5". I haven't found a helper spring from another setup that will fit. More importantly, most helper springs are wussy little things that just keep the main spring from rattling around. Rates like 5 or 10 lbs/in. That's nowhere near enough to extend my shocks when they're valved for the big springs.
AFCO sells 4" springs with a 300 lb rate. It's about double what I'd prefer, but it's the best I can find. The potential problem with this is that it won't fully compress at rest, so the light spring is still active until the car hits a bump or rolls. The weird thing is that the spring rate of the two springs combined is less than either of them. So I'll have a fairly soft rate until all of a sudden it spikes up. How will this work? I have no idea. But I'm willing to give it a try in my science experiment of a car.
My other problem is that because the helpers are 4" long, I need a fairly short main spring. That's a front shock with a 7" 600 lb main spring. I'd prefer a 6" (like the 750 I just removed) but it is not to be. At the lowest ride height I can manage, I'm running relatively high - the front wheel-fender measurement is 12.75". That's about where I was when I got back from the Targa, and I suspect this setup might actually work well.
It's not so pretty in the rear. I have a 7" 450 lb spring back there, but even at a perch height that's a bit lower than I can really use, the car's an inch too high. I'll need a shorter main spring. I have my eyes on a 5" that's 425 lbs. These spring rates (once the helpers are compressed) should give me a similar handling balance to the Targa spec. We'll see.
Fun stuff!
entry 730 - tags: suspension | | |  | March 16, 2010 - I started the day planning to do some dyno testing on some intake variations.
But first, I had a couple of parts to install. First was a couple of springs for the rear, so I could get the ride height into a reasonable range. That was quick and easy.
After that, I decided to put on an ATi damper. Since the car's seeing a lot of constant high rpm use on track, I figured I'd like a bit of extra margin of safety for the oil pump. Besides, it makes the engine feel smoother and the guys at Flyin' Miata suspect there might be a bit of power in it. We'll see.
Unfortunately, the install of the damper and a few other jobs ate up my spare time so the dyno didn't happen. Soon, though.
I did take the car out on the road for a bit of a test drive with the new intake setup. The Hydra was able to autotune itself into a happier place - I suspect I never set up the part-throttle tuning after the fuel pressure change, and so it's running really rich at anything but wide open. Before the changes to the fuel system, the fuel pressure was tied to manifold pressure so I'd see a drop in pressure under vacuum. Anyhow, a half hour drive later and the car's much happier. And pretty fun, once you get used to the heavier throttle pedal. The dual spring suspension is working pretty well - it's quite comfortable on the highway and on smaller bumps as the softer spring takes the hit, but you can tell there's some real stiffness behind it. I think, on track, it's going to have an initial bit of lean and then the car will take a very solid set. Would it be a good Targa setup? I don't know. I need some more seat time.
I did think of one potential problem, however. The Laguna Seca weekend that's coming up in a month or so has a very high 102 dB sound limit - almost unheard of at Laguna. Janel's also going to be driving on Friday with another group to get some private instruction from our friend Rick Weldon. Well, that group probably has a 92 dB limit, and with the current intake setup I suspect the car isn't going to meet that limit.
entry 731 - tags: suspension, intake, damper, engine, sound, laguna | | | March 18, 2010 - More thoughts on the dual spring suspension - this is interesting.
Just for fun, I pitched the car into a couple of the right angle bends on the way in to work. I figured I'd dance with the tail a bit. Now, I haven't been behind the wheel of this car for a while but I've been driving a number of other Miatas. And the car seemed to grip much harder than it should. We have another car at Flyin' Miata right now running a completely different dual-spring setup, and it's showing similar characteristics. Mechanical grip seems to be way up there.
It's going to take more investigation, but I am quietly optimistic. We'll see what happens on the track in a few weeks. Will I go back to the stiff single springs, or keep this dual setup?
entry 732 - tags: suspension | | | March 26, 2010 - I drove the car home from the shop tonight and took the interstate to see how the car felt at higher speeds.
The answer: sketchy. This may have had something to do with some fairly extreme winds, of course. I pulled off at the first exit and tweaked the shocks a bit, and that might have solved it although I wasn't able to test at over 40 mph after that. I want to do more testing - the car feels a bit darty. I'm not there on the shocks yet, I know that. I'll take the car up the Targa Simulation Road tomorrow if the weather is good and see how it behaves.
Ah, the weather. I drove home in spitting, then light rain. Then the rain drops got a little viscous and started building up on the wipers. Just the sort of weather I'd feared during the race. The good news is that the defogger system works and the car felt pretty sure-footed.
Speaking of the race, the airing of the 2009 TV show is on Speed tomorrow at 6 pm Eastern. It'll be shown again once or twice. Plan your day accordingly!
entry 733 - tags: TV, shocks, springs | | |  | March 28, 2010 - One of the first things we wrote on our "things to do differently" list after the Targa was "get a better video camera".
The little Canon DV camcorder we used actually took some very good video, but after a couple of years of track use it was starting to malfunction. The biggest problem was that it would decide to start zooming in, and combined with the wide angle adapter this meant we lost focus. I wish I could watch the entire Leading Tickles stage, but alas all I have is the audio.
I'd been thinking about a pro-level unit like a ChaseCam, but they're expensive. When we do go back to the Targa, I might bring one along. But for the time being (and for the big event at Laguna Seca in a couple of weeks), I decided to try one of the cheaper options. Meet our new Flip Ultra HD. Because it's 100% solid state, I'm hoping it won't fall apart like the Canon did. It takes some decent footage as well, and is very affordable.
The biggest problem is that it's got a fairly narrow field of view. But with an inexpensive wide angle lens and a bit of superglue, that can be changed. The lens screws into a threaded ring, so I can go back to the normal Flip lens easily.
entry 734 - tags: video | | |  | March 28, 2010 - Here's a before-after peek at the wide angle lens, taken up on the Targa Simulation Road.
I think I need to move the camera up a bit in the car, but the wider field of view helps a lot with the sensation of speed. My other concern with the camera had been the lack of image stabilization, but that's not a problem. In fact, the video was rock steady even on this very bumpy road. So that's a big winner then. I'll post the video soon - that's another advantage to the Flip. Very easy to post video to various hosting sites.
I was up on the Simulation Road to see how the new dual-spring suspension worked. Pretty well, I have to say. After a couple of stops to set the shocks (it never ceases to amaze me at how one click makes the difference between "hmm, it's okay but not great" and "wow!") the car seemed pretty happy. This is a tough stretch of pavement and the car was certainly pitching, but it was stable and well-connected to the road. I doubt it would have worked as well if I'd been running the main spring rates alone - 650 and 425 lbs, I think. That's a lot of spring! I'll take it out on the highway later today to see how stable it feels at speed without the massive headwind and with the shocks set up.
entry 735 - tags: video, suspension, testing | | |  | March 28, 2010 - Time for some more dyno testing!
One nice thing about the individual throttle body setups is that I can change out the air horns and alter the intake runner length. In theory, a short runner should trade off low rpm torque to gain high rpm power - and a long one should do the opposite. But if they're way off, then you just plain lose. Since I have a collection of horns, I'll simply do some back-to-back testing and see what happens. It's always interesting to simply install a pipe that's 1" longer and see a power bump.
I had the chance a while back to talk with Bill Schenker, a national-level CSP autocross competitor about his engine. It makes very good horsepower - similar peak power to my engine, but with less torque - and it's all come from hundreds of dyno runs, testing one slight change against another. One thing he told me was that the length of the intake tube running from the stock intake manifold to the filter had a big effect. Again, a 1" change made a notable difference. Of course, he was talking about naturally aspirated power so it wasn't a 15 hp difference, but if you can find 10 places to gain 1.5 hp, there's your 15 hp gain.
So, bring on the air horns!
entry 736 - tags: testing, intake, air horns, IRTB | | |  | March 28, 2010 - Here are the air horns I have to work with.
The silver one is what came with the throttle bodies, the others are some Titan units that I found in the shop. At least, I think that's where they're from. I have some TWM units around as well.
The first dyno runs were with the silver, "stock" horns. I followed that up with the longest of the black ones, just to see if they'd actually fit. The answer is yes, but the filters I was using won't fit over the end of them.
Dyno chart - the red trace is the medium-length silver horn, the black is the long one.
Overall, it looks like a big win for the long tube, with a solid gain from 4200 to redline and no real loss anywhere else. Unfortunately, it's not an apples-to-apples result. The biggest change is that the long tubes had no filters. Now, these are some pretty open filters with a large surface area, so I don't expect they have much effect. But I do need to test them back-to-back to confirm.
There's also a difference in the design of the bell mouth on the air horns. Note how the silver one has a simple horn shape, while the black ones have a more complete radius. This entry is fairly important, and it could be that the black ones have a better design.
The internal diameter of the horns is also a bit different. The black ones actually match the diameter of the throttles, while the silver one is a bit oversize. Interesting, given that it's the one supplied with the kit. The lip of the throttle bodies has a small chamfer in it that steps the diameter down, but basically there's a step change in the size.
Luckily, I have a black air horn that's almost exactly the same length as the silver one, so I can do comparative unfiltered tests between them to see which is the better design.
I only had the chance to do two different runner lengths today. I'll spend more time on the dyno this week and test all four options in the same session. Hopefully.
entry 737 - tags: dyno, IRTB, intake, engine, air horn | | |  | March 28, 2010 - Dyno run video.
It's not exciting, I know. Really, this was just an excuse to practice uploading video off the new camera and make the changes in the website code to use YouTube instead of the no-longer-accepting-uploads Google Video. But if you want to hear how the engine sounds with the new intake, well, it might be worth your time. Video
entry 738 - tags: video, dyno, IRTB, noise | | | March 29, 2010 - Another new video.
This is a run up the Targa Simulation Road to test both the springs and the video camera. I'm pretty happy with both. We'll see how the springs do on-track this weekend.
Video
entry 739 - tags: video, testing, suspension, video | | | March 30, 2010 - Results for the intake runner length testing.
This was interesting. Not because of what happened, but because of what didn't.
Each engine setup was dynoed three times in quick succession, because I found the first one tended to be erratic. The second and third would be almost exact copies of each other. When I was done, I went back to the beginning to test both the silver runners and the filtered option.
Here's the biggest difference: Short (blue) vs long (red). The shorties did indeed suffer in the midrange, with the biggest difference right around 4500. They didn't gain much up top though, which is a bit odd. Cam limitations? The medium and short runners were basically identical. The silver runners and the black ones of the same length were identical despite the difference in lip design.
But here's the really telling test: Filtered (blue) vs unfiltered (red). That's where my high-end gain came from last time. I'm a bit surprised by this, because the ITG filter I use on the Seven makes no difference at all. It's a big boy and apparently very free-flowing. Something will have to be done - read on for more.
So, the long runners were the winners. Everything else was the same. The short runners make the same power as the ones that came with the throttle bodies.
I need to quieten this car down for a 92 dB day at Laguna Seca in a bit less than two weeks. Ideally, I'd build a plenum to enclose those long runners and see what happens. But there's a way to cheat. A friend who runs a business selling parts for Titan race cars has a nice Pipercross 600 plenum I can use. I'll have to stick with the short runners to fit it, but it's a quick and easy way to quieten the car and bring in cold air. It should be here on Thursday and I'll fit it then.
entry 740 - tags: dyno, intake, IRTB, plenum | | | April 1, 2010 - Spent a long day working on the intake.
And of course, I didn't take any pictures. The Pipercross plenum showed up. These are made in either left-hand or right-hand configurations, with my application being the right-hand version. Naturally, I was only able to obtain the opposite.
No worries, all I had to do was to fit the base plate on upside down. But that interfered with my fuel rail. After some poking and prodding, I figured out that the plenum was made in a couple of pieces. I separated the two, flipped one over and voila, my left-hand plenum was now the right-hand version! I had to epoxy everything back together, so that meant I wasn't going to be finishing today.
In the meantime, I cut the base plate to match my runners and installed the short air horns. Due to the shape of the plenum, I also had to relocate the idle speed control valve and reroute some wiring. The latter needed to be done anyhow, it was kind of rough looking. Since I knew I wouldn't have time to test the car any more before the track day on Saturday, I unshackled the car from the dyno.
Over to a lift, I swapped out the current exhaust midpipe (with an empty cat) for anther one that we'd been using for testing. I also needed to find a place to fit an air filter. One of the problems I'd found with the IRTBs on the road was that my intake air temperatures were quite high. The new plenum will not only hush the car (important for Laguna Seca on Friday!) but will give me the opportunity to pipe in fresh, cool air. I decided to try a filter mounted behind the front bumper. It's not the best place if I decide to ford a river, of course, but for normal use it should do just fine. After a bit of thinking, I decided to bolt the top of the filter to a handy flange. Three bolts with big backing washers going through a top that's about 3/4" thick (really, I was amazed at it!) and it's solidly mounted. I'll run the air hose in it tomorrow and the car will be ready. I'll also take some photos.
Is it going to be quieter? Oh man, I hope so.
entry 741 - tags: ITRB, plenum | | | April 4, 2010 - No pictures of the new intake yet, but I have track videos!
Fastest lap
Smoother fast lap
The track day went pretty well. It was a fairly cold one and I only got about three sessions in the Targa car (along with the chance to drive a 350Z, a BMW M Coupe and a couple of FM Miatas), but my best time was a 1:04.959. That's about 0.2 seconds off my best in the car, nothing to be ashamed of. There was a time when simply dropping below 1:06 in any car was unusual!
The dual spring setup does allow for some body roll, but the lap times would indicate the car isn't suffering too badly. It absorbed the berms well and was very stable under braking. I'm trying to decide if I want to keep this setup for Laguna Seca or if I want to pull the secondary springs so the car corners flatter and has quicker reflexes. Tough call. If it can still hustle around our little autocross track here this quickly, I'm thinking the dual setup is working.
The engine felt good. For the first time, I noticed a lack of pick-up coming out of one of the hairpins at 4000 rpm - that's the dip in the torque curve. The heavier throttle pedal (due to a stiffer spring) took a little getting used to in order to be smooth, but I adapted pretty quickly. Nobody noticed that the car was particularly loud, so I'm hoping that's good for Laguna Seca sound levels. Hoping hoping hoping. I did have one person ask me if it was a V8 because it didn't sound like a four-cylinder!
Pictures of the intake are at work, I'll put them up tomorrow.
entry 742 - tags: video, GJMS, testing, track, IRTB | | |  | April 5, 2010 - Time for some pictures of the new plenum!
First, I had to drill a backing plate for my intake setup. In order to clear the fuel rail mounts, it has to sit a bit low.
entry 743 - tags: intake, plenum, IRTB | | |  | April 5, 2010 - The plenum clips on over the base plate.
I had to notch the edge of the plenum slightly to get clearance for the fuel rail, but here it is in place.
You can see the relocated IAC back by the fuel pressure regulator. It's a tight fit wiggling this on!
entry 744 - tags: intake, plenum, IRTB | | |  | April 5, 2010 - Now, I have to get cold filtered air into that plenum.
I have a conical filter that fits into the inlet, but I need to do some dyno testing to see how well that works. The ideal plumbing here would be to put the conical filter in, then run straight to a hole in the hood. But not today.
So instead, I used some flexible 4" hose and ran it down to the filter. It's a tight fit and I'm not excited about the tight radius bends from an airflow standpoint. But it's critical I get this car as quiet as possible.
entry 745 - tags: intake, plenum, IRTB | | |  | April 5, 2010 - The filter is a monster.
I needed one with a 4" inlet to match the inlet on the plenum, so I grabbed the same filter we use for our V8 Miatas. It's Honda sized! A 90 degree piece of silicone and a slightly-fudged adapter into a piece of 4" tube, and we're hooked up to the hose.
entry 746 - tags: plenum, IRTB, intake | | |  | April 5, 2010 - The filter is pretty exposed to road muck and goo thrown by the tire in this location.
And the weather forecast for the trackday on Saturday was looking sketchy. So I took this plastic cover from a 2005 Mazdaspeed and did a very quick and dirty installation. Very quick and dirty - note the use of tape! That's what happens when the track day is Saturday morning and you're still working on the car on Friday night. As it was, the day was dry so it wasn't a concern.
The first day at Laguna Seca has a 92 dB limit. I'm hoping to get past that. The next two days are 103 dB, so I might just pull the plenum off and stick the sock filters back on for maximum roar! Because I'm a child.
entry 747 - tags: intake, filter, IRTB | | |  | April 14, 2010 - Welcome to California!
Three days of track time with two drivers, mixing it up with faster cars. It's a good thing this little car is tough.
The first day was sunny and beautiful. The track day was run by the Checkered Flag Racing Association, which is basically a grown-up version of the Red Rock Racers I run in Grand Junction. Sessions were 30 minutes long and full of some very serious machinery. Even the novice group had a Porsche GT3, a fast little Caterham and a couple of Nissan GT-Rs. The Nissans were being driven extremely quickly, and were really in the wrong group. Overall, a very experienced bunch that were good to share the track with.
The goal for the Friday session was for it all to be about Janel. She's spent so long hanging around as I run around at the track it only seemed fair for her to have her own track day. So our friend Rick Weldon offered to give her personal instruction, and I was pit crew.
We started off doing a sound check. The limit was 92 dB, and we went by the meter at 93.3 dB. After a certain amount of chaos on the part of the organizers who all told us different things, we found that by holding 4th gear through turn 5 we tripped the meter at 88 dB. So there's that solved then.
Rick was running behind, so I went out with Janel for the first three sessions. We had a good time and everything seemed to be working fairly well other than a car that was very grouchy when cold. The biggest problem was dealing with the traffic.
Rick showed up just as we left for the third session, so he only got to ride with Janel for a couple of sessions. She was all warmed up and ready to go, though. He's a fantastic instructor and not only helped her with her lines, but also with how to deal with traffic. She's a great learner, and if you tell her to go full throttle through a certain corner without lifting, she'll do it!
I was running a stopwatch, and we saw her times drop by about 12 seconds per lap - partly due to the way that she dealt with faster cars passing her. The big grin is from her last session, when she spent two or three laps holding off a 911 GT3 (really!) before the monster power on the straight finally proved to be too much for the little Miata. She was putting down consistent 2:00 laps with only a few tenths of a second of variation, plus one solid 1:59.28. You can see her session on the video page. After seeing the times, Rick commented that she'd be a great endurance driver. On the way to dinner a couple of nights later, she asked me how you get involved in endurance racing...
Does she look happy to you?
entry 748 - tags: janel, laguna seca, track | | |  | April 14, 2010 - After Janel had so much fun on Friday, it was time to meet the hundreds of Miatas that had come for Miatas at MRLS.
The plan was for me to drive the car in the fastest A group and take people for rides, and Janel would drive in the C group. However, when I first jumped in the car, I discovered that it was very unhappy under part throttle. It was too late for me to do any more tuning on the car, but spending a single session with a laptop jammed under a seat would have made a big difference. Still, it was easy enough to drive around. I also discovered that while my spare rubber was up to pressure, I had the tires on the car about 7 psi low. Whoops. So the car should have been faster on Friday for Janel if I'd been able to take a quick test drive. Sorry!
For the rest of the weekend, the car pounded around and around the track. The other cars from Flyin' Miata were under orders not to run at 10/10ths to ensure they'd last, but that didn't apply to the Targa car. So I ran it pretty hard, and I know Janel did as well. This is one solid little critter, and so much fun.
The new suspension wasn't a big hit with Janel, and it certainly did allow a lot of lean. Still, it put down the power well and seemed friendly enough. I wanted just a bit less understeer but didn't want to mess with it after Janel had spent so long honing things with Rick.
I spent a lot of my time staying out of trouble with the A group, populated with winged beasts and drivers that were considerably faster than me.
Janel had a different problem. She was much faster than everyone in her group, and so she spent most of the time waiting for the slower driver to point her by. It was frustrating. She really should have been in the B group.
Sunday started off cold and looking like rain, and it started to sprinkle fairly early. Janel came into the Corkscrew with the back end of the car quite loose and almost looped it, and I found the grip level changing on every corner. So we parked the car, and shortly afterwards the skies opened. The track was closed early due to the deep water, and we packed up to go home.
A pretty good weekend.
entry 749 - tags: laguna seca, track | | |
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