| MIATA BUILD |
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 | | October 26, 2009 - I've been doing some testing on the suspension of the car.
As usual! This time, I'm running some very stiff 750 lb front springs with 450 lbs in the rear. Usually I'd run a higher rear spring rate with that much in the front, but it was a matter of what was on hand. The car works surprisingly well on the road, even though that front rate is exactly double what we ran in the race. It's going to be a lot of fun on the track this weekend for sure, with some very quick reflexes right now. In fact, the rear rate seems to be working pretty well. Well enough to make me wonder what I should run in the next Targa. I'd been leaning towards 450/375.
While under the rear of the car swapping in a larger sway bar to keep the handling balance with that "soft" rear spring setup, I saw fresh shock fluid on the right rear shock. That wasn't there when I swapped the springs a few days back. Interesting...
entry 713 - tags: suspension | | | October 28, 2009 - Time to see if the fuel pressure changes did anything!
Background: there's a big dip in the car's torque curve between 3500 and 4500 rpm. Massive, actually. It's about a 10% drop. The theory was presented to me that the B (1999-05) injectors are designed to run at a higher pressure, so they weren't atomizing properly. Thus my work of late to raise the pressure.
Unfortunately, it did nothing. Nothing at all. After a bit of tuning to deal with the different fuel curve that's a result of the fixed fuel pressure, the car didn't change a bit. I spent some time playing with timing and fuel, just to prove that naturally aspirated cars have a pretty big sweet spot. Adding an extra 3 degrees of ignition advance didn't do anything, so I took it out again.
Dyno chart
Okay, so that didn't do anything. While the car was on the dyno, I decided to mess with the intake cam timing because that's quick and easy. I advanced the cam by 5°. This should theoretically help the bottom end while hurting the top. And it did. Kinda. The bottom end got stronger and there was a bit of a taper above 6700 rpm. Pretty good tradeoff. The weird thing is that the dip was unaffected. All the gains were on each side of it. It's obvious that there's something that's just not working in that rpm range, but what is it?
Dyno chart
Next, I retarded the intake cam 5° from my original setting. More overlap, should be a bad idle, a weaker low end and more up top. These are fairly big changes, but I was trying to see trends. Oddly, the car purred at idle. It's always had a very grouchy idle, lumpy and a bit tricky to launch. Not any more. But the car really didn't like the cam settings, losing a huge amount of power down low and only gaining a little bit way up top.
Dyno chart
So, not a terribly successful day really. Although it was educational. The cams in the car are Stage 2 cams from Integral Camshafts, and they say that for some reason their 1.8 hydraulic lifter cams just don't work well. The 1.6 ones do, as do the 1.8 solid lifter cams. Just not these. So the next step is to play with a few different cams. It's the second set I've tried, but I have at least three other options to stick in there and see what happens. Once that's done, I'm going to play with a couple of intake manifold options that are available to me. What I'd really like is a VVT head, as I've seen a very similar engine to mine make big torque right where I have my dip. That engine is in the FM shop, not far from where the Targa car is parked. And the boss is going on vacation...
But still, the engine's getting stronger. Here's a comparison between what it looked like when it first hit the dyno and now. Since then, I've altered the intake pre-throttle, built the header and changed cams.
entry 714 - tags: dyno, fuel pressure, cams | | | October 29, 2009 - A quick engine comparison.
Before Elvis - a 2002 Miata at Flyin' Miata that should be fitted with velcro motor mounts - was fitted with a V8, it had a naturally aspirated motor that was broadly similar to mine. The car had a set of roller barrel throttle bodies and a Racing Beat header but more importantly, it had a VVT head. The dip is missing!
Dyno chart
entry 715 - tags: dyno | | | November 2, 2009 - Track day time!
The new 750/450 springs worked quite well, pretty much eliminating body movement but allowing the suspension to still soak up those berms in the chicane. The car was fairly quick as well, allowing me to match my best-ever time of 1:04.7 despite a cold day and slow times for most people. Janel also liked it, posting a personal best and getting down into the 1:10 range. She's not a big fan of the feel of cold race tires on the warmup lap. There was actually ice on the start/finish line when we arrived in the morning, I'm not exaggerating about the cold!
The shocks are dealing very well with the rates, even keeping the car comfortable on the street. It's lost that very smooth ride it had for the Targa, of course. Bumps are dealt with without upsetting the car, but it doesn't seem to repave the road the way it did. I'm still playing around with what the best spring setup for the race would be in the event that we get to go back. 450/375 and some good ride height? Probably. For track use, these heavy springs are obviously the way to go.
entry 716 - tags: suspension, testing | | |  | November 4, 2009 - Temptation.
Okay, I was really just doing some suspension work on the car and the plastic V8 mockup happened to be used for something else. But wouldn't these two work well together?
entry 717 - tags: V8 | | |  | November 4, 2009 - Time for some intake manifold testing.
Since the big torque dip wasn't affected at all by the cam change or the fuel pressure change, I'm thinking it's something with the intake manifold.
The 1999-00 intake manifold I'm using has VICS, which stands for something like Variable Intake Control System. It doesn't change the length of the intake runners as you might expect, but opens and closes a resonance chamber in the manifold that's placed about halfway down the runners. It's been proven to be fairly effective on the dyno, and the butterflies flip at around 5200 rpm.
The manifold is in two pieces. The lower contains the butterflies and the upper has the chamber - you can see it here with a nice tan color. The passage inside the chamber is for the EGR gases, which are routed from the back of the manifold to be injected just behind the throttle body.
entry 718 - tags: intake, engine | | |  | November 4, 2009 - Based on some things I've read, I've cut out the wall between the plenum and the resonance chamber.
With this setup, the plenum is effectively much larger - but more importantly I now have variable length intake runners. With the butterflies closed, the air will follow the same route as before. But when they open, a short intake path will become available which should benefit high-rpm operation. I also removed the EGR ducting because I don't run an EGR system, and this cleans up the flow near the throttle body. While cutting out the EGR ducting, I did manage to break through into one of the bolt holes, but that was patched up with some good two-part epoxy (ie, not JB Weld). I also modified the gasket that sits between the two halves to match my modified manifold.
There are nice bellmouths on the long runners and ideally I should shape some on the new short runners, but not until I've done a preliminary test to see if the modifications have any effect. It's quick and easy to change the upper half of the manifold. If the testing looks good, I'll go a bit further with cleaning everything up inside both the top and the bottom halves.
Gary at Track Dog Racing has tried removing the bellmouths for the long runners as well as bellmouthing the short runners. He reports power gains on cars with forced induction, but not much without boost. It's worth a shot though.
entry 719 - tags: intake, engine | | |  | November 16, 2009 - I'm proud of this one.
Grassroots Motorsports (GRM) magazine just celebrated their 25th anniversary, and as part of their big issue they named "Our 25 favorite cars from the last quarter century". It should be no surprise to GRM readers that the Miata topped the list. They also highlighted 10 milestone Miatas, "The most important examples of a very important car". And guess what one of them was?
Yup, the Targa Miata is in the company of SCCA National runoff winners, the very first Spec Miata and a winner of the 25 Hours of Thunderhill. One of the 10 chosen examples of GRM's most important car of the last 25 years. August company, and we're flattered to be included. As an added bonus, we're on the front of the GRM website.
If you're interested, GRM has released the issue in digital form for free. It's not just the print copy in PDF, it's got extra content such as video. In fact, you can watch us run the Clarenville stage as part of the Targa Miata mention. It's a beefy download but has lots of good reading and watching inside.
Digital GRM
entry 720 - tags: grassroots, magazine | | |  | November 17, 2009 - Ta daaaah!
Okay, it doesn't look like anything. But that's the hollowed out intake manifold. I'll take the car to work tomorrow and hopefully get the chance to put it on the dyno and see what difference it makes, if any.
I've got two other options sitting on the workbench, both a bit more radical. This is going to be interesting.
entry 721 - tags: intake manifold, engine | | | November 30, 2009 - No dyno charts yet, but the new hollow intake did nothing.
Nothing at all. This matches up with what a couple of other good engine builders have seen. There are some indications this modification is beneficial for boosted cars, but not naturally aspirated.
On to the next step!
entry 722 - tags: intake | | | January 11, 2010 - There hasn't been an update in some time - because I haven't worked on the car in some time.
The combination of a very, very cold December, a bunch of snow and other projects such as Janel's MG have kept me from working on the Targa car. I have a set of rebuilt shocks ready to install and some plans to try something different on the intake.
We'll be at the Miatas at Mazda Raceway event again this year. Janel and I will both be driving, and I'll be giving rides. We're both looking forward to it.
As for Targa 2010, we're considering it. It depends on being able to find some sponsors, and we're working on it.
entry 723 | | | January 29, 2010 - There's a huge change in the factors for 2010.
I've discussed this with the event organizers and it appears it's become public now so I can talk about it. You might remember the discussion of last year's factors. Basically, a base time is set for Class 9 Modified Large. This time is multiplied by the factor for other classes to provide the handicapping. The point is to try to make it an even race so the best team can win, regardless of car.
Naturally, it's the subject of some controversy. No Modern (roughly, 25 years old or less) car has ever won overall although it's been a lot closer than you might think a few times. Some classes seem to be more strongly penalized than others. And of course, there was the very public complaining by the Stillen team, who did not win the event - due to the quality of the navigation in my opinion. The other Targas don't try to handicap the Modern cars, and the Newfoundland organizers have been paying attention.
The end result? A few more classes in Classic, as mentioned earlier, to try to spread the field out a bit. And more fundamentally, the abolition of factors for the Modern division. Awards will still be given for the winner of each class, but given the number of classes this doesn't have a lot of meaning. There's still a 135 kmh maximum average and a 200 kmh maximum speed, so the Modern winner will be the person who can come closest to that average on every stage. The Classic division will be given their own first place award, so the race hasn't changed for the older cars at all.
The result is that Modern classes really don't matter. It's going to come down to the fastest Open Class car, and the rule book is pretty wide open. Worrying about things such as "will my 1999 head put me into Class 8, level 3 and is it worth 10 hp?" is irrelevant. Very few of the older cars are going to be competitive, it'll come down to a race between rally refugees like Subarus, Evos and the GTR with 600 hp and all wheel drive. Should be a dramatic race.
This is going to have an effect on a pretty large number of competitors. I'd say between 1/3 and 1/2 of the teams are suddenly going to be like us, completely out of the hunt because they're less than 25 years old and not equipped with the firepower of the latest supercars.
If I wanted the Targa car to be even close to competitive for a win, I'd have to do something dramatic such as install a V8. Had these rules been in place when we ran, it would have been cheaper and easier to simply stick an FM II turbo system on a stock engine instead of building up what I have. But I ended up with a pretty fun car, so no regrets there. The turbo engine wouldn't have been as operatic to drive as this one is.
It's a big change. Will it be enough to bring Stillen back? That team would have won last year under the 2010 rule set, as they expected to. Word is that Sprongl is preparing his Group B Audi to run as a 1981 classic with Level 3 preparation. Yowza.
There have been a few other tweaks. Cars with 14" or smaller stock wheels (we could do this with a different brake setup) are allowed to run R compound tires if they take a time penalty of 12 seconds/day. Race octane fuel is also allowed for 2010 only with a 10 second/day penalty. Nothing too exciting there.
So, if I was prepping the Miata for a competitive run for the win in 2010, I'd drop in one of the cammed LS3 motors we're using at Flyin' Miata. 480 horsepower and a total weight of around 2300 lbs would give it a decent turn of speed. It would be a fun (and terrifying) car to drive, but would require a fair investment. With the right driver/navigator combo, I think it would work. Unfortunately, that's unlikely to happen.
entry 724 - tags: rules, 2010 | | |  | February 13, 2010 - We made the cover of Forever MX-5 magazine!
Along with the cover is an 8-page article about the race. They've kindly given me permission to post it here.
Read the article
You may remember the magazine published an article about the car nearly two years ago, before we ran the race. Well, they'd asked me for a followup article about the race itself, so I sent something in to them. And of course, magazines started failing left and right right about then. Instead of just shutting their doors like many titles did, the publisher kept trying to bring the issue to press. They were ultimately unsuccessful, and eventually decided to go digital instead. So the long-lost issue has surfaced!
I really enjoyed reading it. Of course, I wrote it. But it's been so long since I've seen it that I forgot how it went. It's not a perfect article but I think it's pretty well done - and it brought the memories flooding back. You can tell it was all pretty fresh in my mind.
The issue isn't just about our Targa adventure. There's also a report on the Miatas at Mazda Raceway Laguna Seca event from last year that Janel and I attended - and will be attending again in April. Add in some Miata club event reports, a road trip article and various other stuff and it's well worth the $1.99 purchase price.
Buy the issue
I've been lucky enough to rate a fair bit of magazine coverage for my various cars over the years, but this is the first time I've taken over the cover.
entry 725 - tags: announcements | | |  | February 26, 2010 - Time for a new intake test!
This particular one is designed for a 1994-97 head. Well, I have a 1999-05 head. The ports are the same shape, but they're higher in the head on my setup. Usually this involves cutting and welding the manifold to move stud holes.
This very cool adapter comes to the rescue! Bolt it to the head with counter-sunk screws, then slip the manifold on. It needs just a little bit of porting to be a perfect match, but I'll do that if the intake shows promise.
entry 726 - tags: intake, testing | | |  | February 26, 2010 - The new intake moves the injectors into the cylinder runners.
The factory ones are in the head. So the holes need to be plugged. When I discovered this, I spent some time looking at various options to solve the problem. I'd honed in on the creative misuse of a specific oil pump plug. I just needed to drill a hole in the top so I could screw something in to yank them out in case I needed to relocate the injectors to their rightful home.
But when I was looking for something else in the various bags that came with the intake, I found four of these little guys. They're specially made pieces for just this purpose, and are an absolutely perfect fit. Nice!
Too bad I didn't go looking further, it would have saved me some work.
entry 727 - tags: intake | | |  | February 26, 2010 - That's starting to look like a race engine.
It took a fair bit of work to get to this point - I spent all day Wednesday as well as a couple of hours on Thursday and Friday - but I've added at least 50 visual horsepower.
The biggest problem was a fuel rail that had holes 10.50mm in diameter. The stock Miata rail is 11.00mm. I couldn't get the injectors to seat without tearing an o-ring. I tried various o-rings from the shelves at Flyin' Miata, but all they had were stock or oversize. A trip to NAPA yielded the perfect thing - injector seals from a Geo Metro! Kudos to the NAPA counter guy who nailed them on the first try.
The red lines are running to a mount for the idle speed control valve. This gives the throttle bodies a bit more civility than you often find with this sort of setup. The ones on the Seven don't have this, and I have to keep that car alive with the throttle until the engine warms up. Not here!
I haven't had it on the dyno yet, I'm hoping to do that this weekend. On a short test drive, the car ran very rich on partial throttle, but felt very good wide open. I'll sort that out in the Hydra programming. It makes a very characteristic noise, with a distinct growl for each cylinder. The return springs on the throttles are pretty stiff so that will take some practice when matching revs - but overall, considering the amount of work to install, it behaved pretty well.
I'm looking forward to see what this has (or hasn't) done to the power output.
entry 728 - tags: intake, testing | | | February 27, 2010 - That was worthwhile.
Overall the throttle body setup shows gains over most of the range with no real losses anywhere. The peak gain is probably around 15 hp at 6000 rpm. Based on some post-dyno tuning, I know I'll be able to pick up a bit more in the 3500-4000 range as well.
Dyno chart
The dip is persisting, though. I've seen it with both headers, two sets of cams, three intake variations and some cam timing changes. I've looked at a number of other cars with similar engines, and while they don't have as big a dip, they also have less torque on each side so the change in output is downplayed. They never actually make more torque than my setup.
The two exceptions were a well-tuned 1.8 CSP engine and another high-compression 2.0. What did they have in common? Variable valve timing. In the case of the 2.0, there's a massive difference. I'm trying to get my hands on a 2001-05 head, preferably one that has some work done to it so it's equivalent to my current one.
Before I go that far, however, I'm going to try some different cams. Why? Because it's easy and I have them!
When I compare this dyno chart to the first time this car hit the dyno, it's come a long way.
entry 729 - tags: dyno, intake | | |  | 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 | | |
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