| MIATA BUILD |
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 | |  | February 15, 2012 - Maintenance time for the Targa car.
I'm changing it over to track spec, and pulled the rotors off for a peek. And what I saw looked very familiar. The pad wear is even on both sides, it's just that the inner face of both front rotors is heavily worn. Interesting. I'm guessing it's related to heat, as the inner face has a dust shield on it while the outer does not. I'm going to do a bit of research here. I do know that the Performance Friction PFC 97 pads can be rough on rotors when cold, but I would expect that to affect both sides.
A new set of rotors is going on, of course. The pads are about 40% worn by eyeball measuring, which isn't bad considering how much I used the brakes this time. Faster car with worse tires means more braking.
entry 1014 - tags: brakes | | |  | February 15, 2012 - Time for an oil change.
Yes, that's 7 quarts of Redline oil you're looking at. And it's quite an adventure getting all the oil lines emptied out.
entry 1015 - tags: maintenance | | |  | February 20, 2012 - Fun with springs.
The new 750 lb front springs are stiff enough that they don't compress much under the weight of the car, so that means they go loose at full droop. So I decided to start playing with secondary springs again. I've done this in the past, but I had new parts and new info.
The secondary springs available through AFCO start at 300 lbs. A couple of years back, I tried this very setup but found that it was tricky to set the damping and there was too much initial roll. After talking to AFCO, I discovered that they had an extra part that would have helped: a stop that takes the secondary spring out of play after a certain point.
Here's how it works: when both springs are active, you get a lower overall spring rate until the softer secondary binds up. So you adjust the stops so that the spacer between the primary and secondary spring can't move any lower when the car is at rest. So when you're moving in compression, only the big main spring is active. Once the wheel starts to drop below the normal ride height (or wherever else you set that stop) both springs come in to play. Clever.
But also designed for cars with much different suspension than a Miata. With my stiff 6" primaries and 4" secondary springs, I simply couldn't get enough adjustment to drop the car down below rally heights. I might have been in luck with tubular front upper control arms, but I don't have any of those.
So I moved on to a more traditional secondary spring. For a lot of coilovers, that means a super-soft spring of 5-10 lb rate that is fully bound at standard ride height. That keeps the main spring from rattling around at full droop, but it's not strong enough to help extend the suspension when you're actually driving the car - especially if your rebound damping is set for a 750 lb primary. I wanted something closer to 100 lb.
Luckily, I had a set of those on hand - the purple springs in the picture. They were very slightly too small in diameter to fit over the perches on the AFCOs, but a bit of noisy die grinder time took care of that. Voila, 100 lb secondary springs that are in bind at rest.
In the rear, I'm running 550 lb springs without secondaries. I may add some later, we'll see what needs to be done for ride height. 750/550 is more rear spring bias than we usually run on Miatas, but it's actually about the same as I ran during the race. I'll also run with very little (or no) rear sway bar so I maximize my drive off the corners and this spring rate will cut down the understeer. Turn-in understeer will be managed by compression damping, I had it too high during the race.
Fun stuff! Although I am getting a bit sick of pulling the front shocks out.
entry 1016 - tags: suspension | | |  | February 24, 2012 - Change in plans.
The 550 lb springs I had on hand were 8" long. Well, that meant a very high minimum rear ride height. Too high for my current purposes. So I swapped them out for some slightly more compliant and shorter 450 lb springs that were in the garage. I'll see how the rate feels and possibly order in some 550s if I prefer those. One nice thing about the softer rear is it means I have a bit more latitude for tuning the balance via sway bar. I don't have secondaries on the rears, although I might add some later.
With all the spring tomfoolery done, the car's back on the ground. It's low compared to the Targa stance! Right about 2" lower. Definitely not ready for Newfoundland.
entry 1017 - tags: suspension, springs | | |  | February 26, 2012 - There's a two-page article about the Targa Miata in the March 2012 issue of Banzai magazine.
It's basically the whole story of the car, from the initial build to the finish of the 2011 race as well as the 2011 fundraising. That's a lot to cover in two pages, but luckily the British use larger paper than in the US!
It might be a bit hard to find in North America, I'm not sure how well the magazine is distributed on this side of the pond. But it's worth a look.
entry 1018 - tags: magazine | | |  | March 2, 2012 - The air dates for the Targa TV show have been posted!
This is for the official event show, not the special project involving the FM team - there's exciting news to come on that front shortly. Still, it's an hour of hot Targa action so you know it's going to be fun.
These times are for the Canadian TSN and TSN2 channels. It will be shown on SPEED around the world, but the dates for those have not yet been released.
In case you're wondering, that's a screenshot from the 2008 show, taking the rally line around the Brigus hairpin...
TSN
March 22, 2012
12:00 am EST / 1:30 am NST
March 23, 2012
1:00 pm EST / 2:30 pm NST
TSN2
March 10, 2012
10:30 am EST / 12:00 pm NST
March 11, 2012
1:00 am EST / 2:30 am NST
March 12, 2012
3:00 pm EST / 4:30 pm NST
April 5, 2012
7:30 pm EST / 9:00 pm NST
entry 1019 - tags: tv, media | | |  | March 2, 2012 - Dyno time!
Before the Targa, our dyno was down for an extended period so all of my tuning was done on the road. And in a car with this sort of power/weight ratio, that's pretty difficult to do. It doesn't spend much time in a particular rev range before leaping on to the next. The car was running really rich which is safer than running lean, but definitely not ideal. So this visit was overdue.
My goal wasn't to determine the maximum power, it was to get the fuel delivery calibrated a bit more intelligently. So I set the dyno up to hold the car at a given RPM. By working the throttle, I could then move the car through all of the load ranges at that engine RPM with lots of time to let the computer zero in on a good mixture. Then I moved on to the next RPM band 400 rpm higher, and do it again. From 2800 to 6000 rpm, it was a long and noisy procedure. By the end, however, I had a tuning map that was a pretty big step up from the hacked-up one I'd started with.
Heat was a bit of a problem. Obviously, holding an engine at 5000 rpm at full throttle against its will does make a bit of heat. The coolant and intake temps would rise over the course of one of my runs, making the numbers a bit less accurate. But still, it helped.
Of course, I did a power run at the end, just to find out. With a very hot engine, the car pulled over 350 hp at the wheels. Not quite the 400 we'd been quoted for the engine, but still pretty darn healthy. There might be a bit more in it when tuned by someone with more experience with these engines.
Thanks to the inopportune arrival of a bunch of snow, I haven't had the chance to feel what it's like on the road. With the leaner mixture, it should have better throttle response. I'm really looking forward to getting the car back down to sea level again.
entry 1020 - tags: dyno, tuning | | |  | March 2, 2012 - I mentioned there was some heat involved.
This is what the hot exhaust did to a piece of stovepipe being used to extract the exhaust. In fact, the pipe blew some of the exhaust back out again and melted the bumper - despite having a big suction fan on the other end.
entry 1021 - tags: heat, dyno, testing | | |  | March 2, 2012 - With the car off the dyno, I took advantage of the fact that I was at the FM shop to hijack a lift.
Step one was to clean up the front aerodynamics a bit. Previously, there was nothing between the air dam and the skid plate. I did have ducting around the radiator so that air was well used, but otherwise it was just plain messy from an airflow point of view. Not anymore!
The plate can easily be removed if I need to get in there - it's held in with a few machine screws around the bottom of the air dam and four bolts at the back. You can just see some rivets in this picture for one of three stiffening ribs that keep it from flexing, and I also did a bit of work at that corner by the wheel to add a lip for more strength. Since it's made of thin aluminum, it weighs very little. But it should do a lot to clean up the airflow.
One downside is that the airdam is no longer flexible - and the car is also much lower than it was at the Targa. So it's going to be more prone to damage. I'll have to behave myself over drops from now on.
entry 1022 - tags: aero, air dam | | |  | March 2, 2012 - I'm also looking at adding a splitter up front.
Made of 0.090" aluminum, I'll probably make it adjustable so I can fine-tune the amount of front downforce on the car at speed. The green tape shows the approximate outline.
I've been doing a lot of aero reading and picking of various people's brains. Jeff at Slick Auto (who donated the carbon fiber headlight lids to the car) has been particularly helpful. His suggestion was for a full belly pan to smooth out the airflow under the car from axle to axle. I'm not sure I can pull that off due to my exhaust, but I'm going to spend some time looking and thinking. The front undertray was really the low hanging fruit. I've got some ideas that will be fun to play with, too.
entry 1023 - tags: aero, splitter, air dam | | |  | March 2, 2012 - The Grassroots Motorsports article about our 2011 race is now available online.
While you can no longer get a copy of the February 2012 issue on newsstands, you can probably buy a back issue from GRM directly. And, of course, they're happy to send you a free trial issue.
Read the article - 4 MB PDF. Thanks to GRM for providing the digital copy!
entry 1024 - tags: media | | |  | March 8, 2012 - Hopefully the front splitter will see some high loads - that means it's working.
So I gave it a bit of support with these turnbuckles from Longacre. The splitter is fairly solid without them, but since it's bolted to a flexible airdam and a fairly thin undertray it could be better. And now it is.
entry 1025 - tags: aero, splitter | | |  | March 10, 2012 - I'm working on a range of updates to the Targa car right now.
Now that the splitter is done, the whole nose is off. Consider this the "before" shot.
For some reason, this looks like an older Celica to me.
entry 1026 | | |  | March 11, 2012 - And voila: the new intake.
After some prodding from Dave, the owner of the current V8 under construction and some measurements on a new Corvette, I figured that the intake for a C6 Corvette would be pretty darn close to perfect. I picked up this Z06 intake from a local Corvette tuner as well as an aftermarket Airaid. This is the factory part.
It fits fairly well under the bodywork, but some modification is required. The radiator crossmember needs to be reshaped a bit and the bumper support had to get chopped right in half. I welded a new pipe across the front just in case there was any structural loss from that bumper support, but it was made of very thin steel so I don't anticipate much of a problem. The hood also needed to be cut away a bit further. But when it's all done, it does clear!
The Airaid is just a little bit thicker and has slightly different geometry. I'll try once again to see if I can make it fit, but it's looking as if the slightly smaller stock unit will get the nod.
entry 1027 - tags: intake | | |  | March 11, 2012 - Here's the intake in place.
The filter is just above the mouth opening in the nose, visible if you get down to squirrel level. It will have no shortage of cold air there! I'm missing one piece of bodywork in the nose here, the one that seals around the front of the rad. I'll cut it to clear the intake next.
This should provide a comfortable power gain under hard use. The GM engine computer pulls timing starting at 80F intake temperature. And I was well, well above that. All of my ductwork on the driver's side won't be needed anymore, so it's possible I'll pull the NACA duct headlight cover off again and reinstall the turn indicator in place of my mesh unit. There's no advantage to ramming air in behind the radiator.
entry 1028 - tags: intake, aero | | |  | March 12, 2012 - Here's a view of the filter from squirrel level.
Cold air? Yes.
entry 1029 - tags: intake | | |  | March 12, 2012 - The finished intake.
I made a flat plate to cover the MAF sensor hole and glued it on with some RTV. The bellows have a flat spot on one side to clear the drive-by-wire throttle - flipping that piece over gave me a nice flat spot to poke a hole for the air temperature sensor. A piece of rubber gasket that used to be around the front of the filter does a nice job of sealing the cutout around the blocking plate at the top of the nose.
I'm pretty happy with how this turned out.
entry 1030 - tags: intake | | |  | March 14, 2012 - I'm almost done preparing the car for Laguna Seca.
I've swapped the plain headlight cover and stock turn indicator back in. That's a bit of a shame, it really did look cool. But aerodynamically they're all wrong now, so they had to go.
I also cornerweighted the car last night. I disconnected the sway bars, rolled the car back and forth and bounced to to get rid of any binding on the wheels. And it came out at 50.0% cross weight. Well then, my work here is done! The front/rear distribution ended up at 55.5 front (without driver/passenger weight) and 50.0% left/right balance. In the race, it has an extra wheel and a tool bag in the trunk which would pretty much bring that back to 50:50.
All I have left to do now is a check of the alignment and then to clean it up. Then I get to scrub in the tires at a track day in a week and a half, and it goes on to the trailer for California!
entry 1031 - tags: preparation | | |  | March 23, 2012 - Can you change the air filter on your car without even opening the hood?
I can! It's easy to reach through the mouth of the car.
This Attack Blue air filter arrived today. That's the stock one beside it, imitating a roll of blue paper towels. The stock unit filters well, and if you want lots of flow the stock LS9 unit (used on the supercharged ZR1) will drop right in. This cone filter flows as well or better than the LS9 part according to some dyno tests. I wanted it because it's tucked back a bit further inside the housing and gets the filter out of direct insect strike range. You can no longer see the filter surface unless you're lying on the ground looking up.
The retainer that holds the filter in place would be a good place to put a coarse mesh, something to act as a strainer for bugs and the like. If I see any signs of that being a problem, I'll do something along those lines.
I have to give TKO Performance a mention here. They weren't able to ship my filter right away when I ordered it, which meant that I wasn't going to have it in time for Laguna Seca. I made a call to them asking what was going on, and they volunteered to bump it up to 2-day shipping so I'd have it in time. The fellow on the phone also knew his stuff, discussing the installation process without having to think about it. Nicely done.
entry 1032 - tags: intake | | |  | March 26, 2012 - Time for a quick track test before Laguna Seca.
With the number of changes to the car, I had to get at least an idea of what to expect even though I had a pretty good idea. Besides, the tires needed to be scrubbed in.
Overall, it went pretty well. The track is a short tight one, not like Laguna Seca at all. But it's got one long 70 mph sweeper that I use to evaluate overall balance. Through there, the car seemed fairly well balanced with a bit of a bias towards oversteer under power - of course, the power level could have something to do with that, as I'm right in the meat of the powerband in 3rd as I try to balance the car in the turn.
Elsewhere, the car felt good with a quick turn-in. I'll probably leave it as is for the big track, or possibly drop in a slightly softer rear sway. The new front aero could be causing a bit of high speed oversteer due to increased front downforce, it'll be an interesting experiment.
Overall, the car felt just a bit low on grip. RA1s are like that on their first day out, they don't seem to develop maximum grip under after a heat cycle. My times in the first session were very consistent, which is usually a sign of a good handling car. As the day went on, they dropped with just about every lap. My last lap was my fastest, with a 1:03.388. That's a personal best in this car, and next time out the tires will be ready for more. The fact that there were cones on the apexes in the chicane meant I had to take a slower line than usual through that section.
So, a good day. A very short bug list of problems to deal with, and I'm ready for Laguna Seca. One nice side note is that the car's light throttle behavior seems improved, with less snatching than before. I'm thinking this is a result of the new intake. I like it.
entry 1033 - tags: track, testing, suspension | | |
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