| MIATA BUILD |
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 | |  | December 19, 2007 - Time for a fun job.
The engine just isn't performing the way it should. At higher rpm, it's choking off. So it's time to replace the Racing Beat header (designed for a 110 hp car) with one a little more robust.
I had a very interesting conversation with an E Production racer, and he shared his header specifications with me. Yes, I know, they should be scientifically matched to my cams and port lengths and everything else. But an E Production Miata is the closest thing out there to my car, so I figured I'd take advantage of their knowledge base and see if uncorking the exhaust does anything at all. If so, I'll make another with a little more specificity.
31" primaries with a 1.75" tube size, right then. The first step is to get a collector. These are expensive - but a bit of searching turned up this beauty. Edelbrock makes merge collectors with 1.75" inlets for only $90 or so, street price. Sure, they're not as pretty as the $300+ units, but I can cope with that. Especially when it turns out the $90 price is for a pair!
Nice. Now all I need to do is figure out how to stuff all those big pipes underhood. The EP guys gave me some ideas there as well...
entry 350 - tags: header | | |  | December 19, 2007 - The last time I built a header was for my little Seven.
I used pool hose to work out the basic routing, then improved on that with some welding rod. It worked out well, but that car did have a lot of space available to work with. You can read the whole saga starting here, you'll have to skip over a few days worth of installing side panels and the like as I procrastinated.
This time, I have the advantage of a very cool tool. This "header Lego" from icengineworks is exactly what it sounds like - 1" pieces of tube that snap together into whatever shape I need. I have 2", 3" and 4" radius bends as well as short bits, and they're all beautifully marked up to make fabrication of the final product easy. Well, easier. This is going to be quite interesting to play with. I'm going to have some fun. Although I do think the pool hose might have to make a comeback to get me started on layout. Where did it go?
entry 351 - tags: header, other cars | | |  | December 20, 2007 - The starting point.
Except for a lapse in 1999-00, Mazda used a nice 4-1 header on the North American naturally aspirated cars. Overseas, some models got a long 4-2-1 design. It's actually a reasonable setup, much better than most stock exhaust manifolds.
I'll cut this up and use it for the flange, just as I did on the last header I made. The iceengineworks parts are designed to be fastened to a stub of round tube.
entry 352 - tags: header | | |  | December 22, 2007 - Step one complete!
A Sawzall made short work of the stock piece.
entry 353 - tags: header | | |  | December 22, 2007 - A couple of other Miata headers.
The complete one is the Racing Beat unit I pulled out of the car. It has 1.675" primaries - only 0.125" smaller than I'm planning to use - but they're much shorter. There's a bit of inconsistency in their length, but I'm coming up with about 15-16". Really, this header is tuned to work best at very high rpm according to the math.
The other pipe is from a Boig Motorsports header, one that had a great reputation in the Miata world for a while. It's for a 1.6. 1.75" primaries that are about 29" long. I'm going a little bit longer - about twice as long as the ones in that Racing Beat unit! Packaging is going to be a concern.
entry 354 - tags: header | | |  | December 22, 2007 - In order to sort out general packaging, I pulled out the blue pool hose again.
The collector is duct taped to the steering column as it fits well there. That means that I have about 10 feet of tubing to deal with, mostly in the engine bay.
The tubing is stuffed into the flange and duct taped into place. Since it slips into the collector, it's relatively easy for me to explore basic configurations - does the #4 runner go in front or behind of the #3? - and get an idea of how complex this will be. It seems that the first three tubes are simple enough, but that #4 is going to be a bit of a pain. Let's just hope I can make it a little bit artistic as well.
entry 355 - tags: header | | |  | December 26, 2007 - In order to attach the header design bits to the head, I attached some little expandable plugs to the header flange.
They're all set up so the base of the first piece of header is 1" from the port.
entry 356 - tags: header | | |  | December 26, 2007 - Because the #4 runner was the one that I was most worried about, I started there.
Here's the first version of the first three tubes - unfortunately I don't have enough of the right curves to finish off the #1 primary. While this configuration looks fairly simple, the tubes are more complex that you'd think. Plus they just don't look all that good and #1 is going to be a challenge.
entry 357 - tags: header | | |  | December 26, 2007 - All of the pieces of header Lego are marked not only with the radius of the bend, but with witness marks.
This makes it easy to make sure you're not cheating by twisting a bend to make it work for you. It also makes it easy to recreate the bends later.
I used these to document the current tubes so I could take another try.
entry 358 - tags: header | | |  | December 26, 2007 - On the second try, the #3 and #4 runners worked out really well.
They're basically the same shape and stay nice and close to the block, but with enough clearance to get at the various header nuts. They're also a bit lower for more hood clearance.
The long straight sections at the bottom are not only easy to fabricate, they also make it easy for me to adjust the length of the tubes if desired. By putting a couple of slip joints in there, I could set it up so I could tune the header. Hmm.
entry 359 - tags: header | | |  | December 26, 2007 - And now it starts to get crazy.
This #2 tube looks brutal to fabricate, but it will actually involve fewer pieces than the previous design did. I suspect I could also make that big loop with a single radius, but unfortunately the combination of being forced to work in 1" increments and a lack of remaining 3" radius pieces made things a bit awkward.
I've figured out how the #1 runner will go, I just don't have the parts to build it. The good thing is that I've managed to keep everything almost perfect in terms of matching lengths.
entry 360 - tags: header | | |  | December 26, 2007 - I didn't just work on the header today - although I certainly did spend most of my time on it!
This fire extinguisher got mounted in place. Okay, it's not a big job. But it's an important thing to have on board!
entry 361 - tags: safety | | |  | December 29, 2007 - The header will be constructed out of mandrel-bent tubes - and lots of them.
I've been looking around online and pricing them out, then decided to stop by my local muffler shop. They had most of what I needed in stock, for the same price as the best online stores! I've said it before, but if you're ever looking for exhaust work in Grand Junction you want to stop by Scotty's Muffler.
I'll know on Wednesday (hopefully) if they can source 2" radius bends as well as the 3" and 4" I have now. If not, I'll order them in. Until I have 2", I can't build any of the pipes yet.
entry 362 - tags: header | | | January 2, 2008 - Well, my local shop can't source the 2" radius bends I need.
So it's off to Summit Racing for them.
I've also been chatting with the engineers at AFCO. The shocks are off getting a tweak to the valving, based on shock dyno tests of a few other options that did well on the comparison drives. I feel like such an amateur when talking to them, but every time I learn something and the shocks seem to come back a little bit better. This should be the last iteration.
entry 363 - tags: header, suspension | | | January 8, 2008 - A big box of pipes arrived yesterday.
Janel didn't seem to understand my excitement. Oh well. Now I just need to get up the nerve to start cutting and tacking tubes. It's a big step, but I know from last time that a solid day's work should show good progress. Last time I didn't have the cool design tools I do now...but I also had a much simpler header to build.
In other news, the shocks are revalved and should be heading back this way shortly. Not that I can drive it right now, the diff is gone and of course the engine bay is full of blue snakes.
I've also been talking to the new technical director for the Targa. As you may remember, the cage I'm using is an SCCA Spec Miata cage. I was given the okay to use this, but it doesn't meet the Targa rulebook. Well, apparently it does meet the approval of the new tech inspector with the exception of door bars. They're putting an emphasis on door bars for 2008. I'm going to have to find space to stick another one in there on top of the one I have now. I think I know how I'll fit it in place. Hopefully I won't have to disassemble the car too far to weld it.
entry 364 - tags: header, suspension, safety | | |  | January 8, 2008 - So, I didn't have any work I could do on the Targa car last weekend.
So I worked on something else. We seriously considered this little guy as a potential Targa car. It certainly would have been fun.
entry 365 - tags: other cars | | |  | January 10, 2008 - Okay, time to start building this header.
The first step is triple-checking the fitment of the #4 tube. I made sure all of the witness marks on the icengineworks "header lego" were marked so I didn't twist anything, then removed the #4 runner. I'm going to build this header from the back forward.
When designing the tubes, I was careful not to cheat and have every piece of lego twisted at a different angle. So it was easy to break the runner up into pieces that were chopped out of my pre-bent tubes. The hardest part is making sure the cut is straight across the tube and not at an angle.
entry 366 - tags: header | | |  | January 10, 2008 - The #4 runner is broken down into four tubes.
I cut these by hand with a hacksaw. A good bandsaw would have been faster, of course, but I don't have one. I used a bench grinder to clean up the ends - again, a belt sander would have been better but I don't have one of those either.
There are three different radii across these four pieces of tube. I transferred the witness marks over from the plastic pieces and grabbed the welder.
entry 367 - tags: header | | |  | January 10, 2008 - And voila!
The first runner. They're almost a perfect match, with a very slight difference in one angle (not visible here) that I think comes from a cut that's not 100% straight across the tube. From this angle, they're identical. The reason they look a little different is because of the way they're sitting on the ground.
So far, so good. I have to admit I'm cheating a bit and doing the really rewarding, fast work first. But that's part of keeping motivated, isn't it?
entry 368 - tags: header | | | January 10, 2008 - An unfortunate turn of events.
Due to personal reasons, Eric's not going to be able to take part in the Targa Newfoundland for at least several years. It was his enthusiasm that got us committed to this race in the first place, and it's a real shame he can't make it to the starting line in September. We've been friends for a long time and this was going to be the realization of a dream.
The effort isn't going away, though. I'm still going to drive in the race. I'm not sure who my codriver is going to be at this point. Eric is still going to be involved as much as he can, and who knows what will happen eventually. But for 2008, someone else is going to be in the codriver's seat.
entry 369 - tags: announcements | | |
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