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Last night I got the car back on the ground. It had been up on jack stands for at least a year. Removed everything that needed to come out and Aarkaah and I dragged it to the fabrication shop this morning.
I will be having all of those haphazardly drilled holes filled while also having the trunk floor sheet metal (spare tire well) removed. A 0.125" thick aluminum cover will be fabricated and fastened with rivet nuts to facilitate easy removal (to facilitate ease of access when working with the fuel surge tank and to also futureproof for a fuel cell installation if I end up needing one in the future) There will also an additional (removable) support that will brace the top of the fuel tank since that purpose is partially served by the spare tire well (which will be no more)
Earlier this week I reached out to the fabricator who I will have doing the cage fabrication(sorry guys. Had to let the cat out of the bag...)I will be using a different fabricator, (who is experienced in chassis fabrication and has very high standards of work) as the person I use to do my general work is smart enough not to do cages due to them being a huge PITA with very slim to no profit margins for the amount of work involved. We are tentatively planning for February of '24. Naturally this costs money, so you will more than likely see many classifieds listings from me in the near future.
Since I want to run NASA, SCCA, EMRA, and events sanctioned by other organizers, I concluded that the best practice would be to build to NASA specification as they have the most stringent requirements. (I also want to run Targa Newfoundland or Carrera Panamericana with it one of these days (hopefully in the next 10 years! ))
The basic specifications are as follows:
six point w/ triangulated anti-intrusion bars in footwell (so basically an eight point).
dash bar.
1.75x0.95" 1020 DOM tubing for main structures. (lighter and stronger than 1.5x0.120 tubing and I am unsure of what my weight w/o fuel and driver will be. Shooting for 2450-2540) (can I live without windows? )
gusseted a-pillars.
plinth boxes for mounting of forward hoops.
mounting bracket fabricated for pedal assembly and tied into firewall/dash bar, and mounting bracket for steering column.
FIA "X" style door bars (topmost part of door bar will be in line with door latch. Will be gusseted.
single diagonal bar bracing main hoop.
rear strut towers will be tied in together with tubing (reinforced by mounting plate) this section of pipe will not brace to the rear down bars.
rear down bars will go to the front of the strut tower (reinforced by mounting plate)
diagonal roof bar (or I could go straight across, will have to think about that one)
will more than likely be having a more sturdy (and maybe lower?) seat mounting solution.
I may also have a taco style gusset on the inner radius of the forward hoops (I hope that makes sense) to increase the rigidity of the a-pillar without having to add the FIA style supports.
Photo courtesy of gnx7. I may borrow the idea of bracing the strut towers to the firewall (not the forward section. (will need to run this by a NASA tech inspector as I am not permitted to drill holes THROUGH the firewall for tubing but am unsure of just welding to it. Photo courtesy of Sir20B from Ausrotary. I got the idea for the aluminum cover from his build. Also refer to the mounting of the down bars. Found this on a Super Taikyu team website (think it was the ww2 #78 FD). I really like how the main hoop and top of the door bar is gusseted. I will not be gusseting to the b-pillar.
Naturally, I will be running this by a technical inspector BEFORE any of the tubing is cut.
FAQ section Q: "SETaylor, what the heck is wrong with you? couldn't you just put a roll bar in it and be done with it like the rest of us reasonable folk?"
A: If I were just running HPDE's and track days with it, I might have been able to get away with just a roll bar and felt okay about it. The problem is that I want to run hill climbs and tarmac rallies, and trees will literally rip these (very fast and good looking) tin cans apart at the speeds we are seeing at these events. We actually lost a driver this past summer in a similar situation in an appropriately prepared car, so I want to do this the right way.
Back by (un)popular demand, I bring photos of my trunk floor solution. I will provide more photos once I drag the thing back from the fabricator.Disclaimer: the following photos involve large areas of sheet metal being removed. Viewer discretion is advised.
Above you can see the rather novel approach that was taken to allow me to retain the stock fuel tank while also doing most of the work required to facilitate the installation of a fuel cell. Not pictured is a 0.125" thick aluminum plate that is fastened with riv-nuts. The fuel tank support is also removable. Note how it supports the fuel tank in the same areas that the spare tire well does in the OE configuration.
I may also take advantage of the empty space (will have to check with the catback reinstalled) and add a water tank for auxiliary injection (thinking 8 gallons with a level sender that will go to my dash display). NASA CCR dictates that if I put it inside the passenger compartment, I will need a bulkhead regardless of what is in it, so this is likely the most advantageous place. (I could also use the additional rear weight distribution.
I also lucked out and picked up an excessive lower intake manifold from spintowinrx7 today and also got to check out his project. Cool guy! Never thought one of these would pop up for sale locally!
Once I get the car back from the shop, I can start cleaning up the remnants of the seam sealer. I'll use either the SEM or Eastwood product for the new stuff.
The semester has come to a close and by some divine measure, I have maintained all A's. Anyway, I figured I'd add some photos from my more recent developments.
Here's the aluminum cover I made reference to earlier. Happy with how this came out. I will be adding a bulkhead door for the (eventual) water tank that will be below it. Will also be drilling holes for the fuel pump wiring when the time comes. I might also be able to work out a solution for the damper reservoirs that does not further involve me further messing the chassis (I know this sounds hilarious coming from me at this point, but I'd still rather not if it didn't have to)
All of the self tap holes left by the PO's haphazard modifications have been welded shut. Would you believe that someone would drill into the rear fended wells to push out dents and not put anything there to cover it? Will deal with the corrosion left by a leaking battery when the time comes.
Got an angle grinder and some wire wheel attachments for my discount rotary tool. Made short work of the seam sealer. Also made a gigantic mess, but I have procured some coveralls that somewhat match the color of the vehicle, so that was pretty cool. The only reason I'm messing with this stuff is because it will be visible when completed and if I'm going through all this trouble, it should at the very least be nice. (It pays to be a perfectionist, or so I have been told and I do have standards )
I want to get this done before the car has to go in for the cage fabrication since my access to the seams will likely be restricted to some degree after it goes in. I will be using SEM beige 1K for the reapplication of the seam sealer later and will likely use lacquer thinner to smooth it. (did I mention I am a perfectionist when it comes to seemingly asinine stuff like this?)
I also took the time to reorganize the garage. While I don't have any before pictures (at least I don't think I do), believe me when I say it was not an enjoyable workspace, but this is much easier to work in and look at.
At this point, the only things left to do before I send the chassis off (planning around end of January or February) I will need to procure or do the following:
Window net. Robinson race cars makes a very nice solution that uses a Safecraft push button as a release mechanism.
Windshield has to be removed. (I want gusseted a-pillars)
Remove all seam sealer in interior where welding will be done (getting there, If I have time I'll just remove all of it)
Lifeline quick release. I don't forsee myself being able to enter and exit this thing without the steering wheel being removed.
Six point harness(es) and required hardware. Something with an FIA cert.
Thanks for reading. Really enjoying getting to do all of this as much of the experience gained has many other applications.
I finally read the thread Simon! I really can't wait to come over and see your car in person. Very excited for your build especially the brake system. You've inspired me to start my own build thread.
I finally read the thread Simon! I really can't wait to come over and see your car in person. Very excited for your build especially the brake system. You've inspired me to start my own build thread.
Thanks Aaron!
Starting a thread and keeping it updated will help you remember what (or how) the heck you did something (and why) when you're inevitably trying to change something. The more documentation the better! (this is usually the case for most things, unless if what you're trying to do is illegal, then disregard! )
The brake system design was quite the learning experience and I now know more about it than I ever wanted to . OEMs have design constraints (modularity and cost control, etc) that you don't necessarily have to follow (though there is usually a good reason they did what the did). Piston area, master cylinder bore, rotor annulus, line pressure and all that stuff can be used to calculate torque on the rotor (and axle) which is how "brake bias" is calculated.
The past few days were rather eventful. spintowinrx7 and I assembled his engine (well, we need to procure and torque the bolts on the front cover). I didn't really know what to expect since this was probably one of the only things (with the exception of engine calibration) that I haven't yet done to a third gen at this point . It was a lot less trouble than I thought it would be, which was nice. If this thing holds together and I am feeling up to it after preparing this chassis and the wiring, I might consider having my irons ported and reassembling the engine myself. I didn't assemble the side and corner seals so I will have to see how much fun that is next time.
We pressure tested the coolant system overnight and there was no discernable change in the reading, so at the very least, we know it won't leak coolant!
I also started some CAD modeling (cardboard aided, not computer!) for my (currently notional) water injection tank. I didn't want to put my (very wonderful) fabricator through it as the easier I can make his job the better the end result will be for both of us.
The tank will be of an abnormal shape due to the constraint of having to place all liquids behind bulkheads and my unwillingness to put it inside the car (and then make a firewall for the rear hatch) and also the design principle of mounting heavy things the lowest.
The section that overhangs the fuel tank will extend 7.5" from the top of the tank, leaving enough space for an air gap and heat shielding between the muffler which will more than likely be mounted with ceramic spacers. Given that I will only be using water (methanol and methanol blends have their own set of supplemental regulations) I think this should work well. This might be excessive but I am going to see if I can get muffler temperature data from people with (running) cars so that I can best hypothesize my heat management in the area. I will likely use a 0.125" sheet of mica or 304SS corrugated steel shielding (Or I could just use both)
If I have the space (which I likely will), I may elect to move my fuel pressure regulator all the way back to the hatch area so that I can set it up as seen pictured below. (I would think that I can rout a (ptfe/ss braid) line for vacuum all the way to the back of the car (under it) and also the wiring for the sensor, but It might also be able to do it inside the car if I group the sensor wiring with the fuel pump power and ground feeds coming out of the PDM.
An added benefit is fuel not being heated via having to cycle through the engine and less material will be require to plumb the fuel system.
Diagram courtesy of BLUE TII. Apparently this is how they do it on the 5th gen corvette.
I will need to check dimensions on the finished cardboard water tank model, but I think I might be able to place my rear remote reservoirs on a bracket that occupies the space in between the front of the tank and the frame section left following my removal of the trunk floor (I hope that made sense). I priced out Staubli dry break fittings and I would need an extra $900 plus the new hoses I will require anyway, so if this works, great! (also less holes in chassis with this setup. I actually decreased the amount of holes in the car in part by removing the trunk floor.) (I know that isn't how it works, but let me have my fun)
The water tank will also feature a welded bung for the fiill cap (2" dia cap from pro werks) and also (proabably) a -4AN bung for the injection pump and also a rollover valve to allow for venting. It will also feature a floatless level sender (in the lowest part of the tank) that will go to my dash display so I know how much water is in there. I will also likely use anti-slosh foam.
Watching this build with interest. Apologies if this has been covered, but how are you planning on dealing with chassis flex? I'm assuming the cage will all but eliminate any issues. FD feels like a wet noodle compared to modern cars.
Watching this build with interest. Apologies if this has been covered, but how are you planning on dealing with chassis flex? I'm assuming the cage will all but eliminate any issues. FD feels like a wet noodle compared to modern cars.
I have some ideas for chassis reinforcement (specifically, torsional rigidity), but I think I need to conduct more research before I go too far. So far, I have a few options:
Add a roll cage (and additional chassis reinforcements connected to it) This is likely the way I will go at the moment, but if I can determine to what degree stitch welding select areas will be beneficial, and it doesn't end up costing me an extra obscene amount in labor and materials, I will have it done in addition. (I should probably see if the guy I have do my general fab work can do it after the cage has been added, but I may pay more for the pain and suffering it is likely to cause )
seam or stitch weld the chassis
Add a roll cage and seam or stitch weld the chassis
This write-up I found shows us how it can be quantified in a decently scientific manner. https://wilhelmraceworks.com/blog/me...ssis-stiffness Interestingly enough while not an FD, it does show that OE reinforcement braces do what they're supposed to do.
If I ever get around to it, I'll have a fixture made so that I can determine the efficacy of additional bracing (quantified in the gain in percentage)
I'm not quite at the point where I can discern the difference in torsional rigidity between two vehicles (unless it is extremely obvious), but the resources I have found suggest that it will allow the suspension to work more efficiently and that the less deflection there is in the chassis (which can function as an undamped (read: uncontrolled) spring which is likely detrimental to performance).
It also looks like the folks at Porsche, among other manufacturers with customer racing programs do it too, and I would like to believe that by nature of what they do that there must be a measurable benefit to justify the expense and requisite labor of such a process.
I'm trying to see (well, I should probably just ask for clarification) if NASA will allow me to connect the front strut tower and dash bar without going through the firewall (mounting plates on each side to distribute load) because they don't allow roll cage tubes passing through the firewall despite it being beneficial from both a safety and performance standpoint, Which is really funny because FIA article 253 section J (the one that dictates methods for roll cage construction) permits it!
I had also been planning on having my suspension pick-up points reinforced too, as I have heard reports (and seen) them break on a circuit FD and some other cars that share similar designs. I may even have the headlight buckets modified to clear a 650mm tall tire(I can't find 280/645R18's anywhere these days) so that I can use take-off Pirelli and Michelin slicks for less monies than a set of R7's from the crazies that run in PCA GTB1 who have no issue spending $10K a weekend on tires and throwing them away at the end of it. Probably going to use Toyo RR's or Hankook Z214's until I really get a handle on this vehicle on a road course, however long that may take...
you might start with the SAE paper Mazda has on the Rx7 body stiffness.
that MR2 thing is neat, someone on here did it with an FC, in the race car section.
the other thing you can do is look at some old Japanese Rx7 magazines, they show some pretty in depth pics of some cars under construction, and if it was famous, sometimes it makes it to the internet
this is the FC2000 that i believe Team Rx8 found
This likely doesn't apply to a street-car based racecar like the FD, but...
In 1999 we added a chassis stiffener triangulation brace that tied my F2000 Pinto engine cylinder head to the roll hoop. This stiffened the overall chassis significantly. Unfortunately, with the suspension and dampers we were using, this noticeably reduced the cornering G-load capability and the car was slower. We couldn't at that time understand why this was happening, but after a short time being quite frustrated we removed the brace, and the grip came back.
Bottom line: every racecar is a system, and not every theoretically-correct change is beneficial.
...Bottom line: every racecar is a system, and not every theoretically-correct change is beneficial.
Another example:
Back when we did the "Longest-Day" 24-hour races at Nelson Ledges, one time our team was running 2 Ford Rangers (small pickup trucks) on street tires. One was entirely stock, and one had stiffer shocks and swaybars.
The modified one was easier to drive, but the stock one was faster.
Another example:
Back when we did the "Longest-Day" 24-hour races at Nelson Ledges, one time our team was running 2 Ford Rangers (small pickup trucks) on street tires. One was entirely stock, and one had stiffer shocks and swaybars.
The modified one was easier to drive, but the stock one was faster.
DaveW,
I appreciate you bringing this up, as many folks often fall into the "more is always better" trap when it isn't necessarily always the case. Like you stated, a system is only as effective as it design (and constraints) will allow it to be. It will be very interesting learning how to set this vehicle up and learning how to get the most out of a modern data acquisition system.
It has been very interesting (so far) taking a road car and attempting to design and fixture a (properly functioning) race vehicle out of it. As you are aware, most of the hard work was done by the engineers, so I don't have to go to such great lengths as others have been required to do so with different platforms. That is not to say it is easy per se, but the simplicity of the exercise does help. It is very encouraging to see the forum members who frequent road courses still posting up some very impressive lap times all of these years later, in street cars nonetheless!
I'll be fascinated to see how this will work, given that save for maybe Australia and New Zealand, third gens are not exactly being developed for this application these days, and all of the ones on this side of the world largely had been designed and constructed decades ago. I hope I'll be able to make good use of all of these fancy new technologies and all those years of development that we have at our disposal nowadays.
you might start with the SAE paper Mazda has on the Rx7 body stiffness.
that MR2 thing is neat, someone on here did it with an FC, in the race car section.
the other thing you can do is look at some old Japanese Rx7 magazines, they show some pretty in depth pics of some cars under construction, and if it was famous, sometimes it makes it to the internet
this is the FC2000 that i believe Team Rx8 found
Will definitely have to check out the SAE paper. I found one entitled "Development of Lighter-Weight, Higher-Stiffness Body for New RX-7". Is this the one you speak of?
I was able to find some photos from a car that was campaigned in the super taikyu series (believe it was diyman25's?) and it looks like they put rivets everywhere. If anything else, I will likely have front frame rails (the area where people add those braces) reinforced with seam welds.
I might also end up replacing my "SR Motorsports" branded strut bar for a custom job similar to the one that Logan from Defined Autoworks (GtoRx7) did on one of his cars, as I'd image it's a little more (probably a lot more) rigid than what I previously used. Photo courtesy of GtoRx7.
So I did some more research in the NASA ST/TT 1-4 ruleset and it looks like I just had an acute case of poor reading comprehension (It turns out that there is an exception for the aforementioned classes in the supplemental rules that supersedes what the CCR states.). I can do whatever the heck I want with roll cage attachment points. (at least that's what section 5.2 article 15.6 says)
A guy on the ausrotary forum (believe it was Graeme Smyth/SMS Fabrication) had this method of tying the strut towers into the cage. I really like how there was a "box section" welded to the towers where the tubing will be welded, as it also appears to place it (the tubing) in such a position that it has more surface area and a more direct load path to the anti-intrusion bar if that makes sense.
Greetings all. I am back with more rx-7-related nonsense. Today I had my roll cage fabricator (who also has an rx-7 problem) come over and scan the vehicle so the cage can be designed in CAD (Fusion 360) and sent to a CNC mandrel bending facility. In theory this will allow him to design the cage in w/ more intricate features and a better fit (or detailed, for that matter) than would be afforded with a manual tubing bender. I'll add more photos (screenshots from him) when the design has been completed.
I also ended up procuring a window net mounting kit from Bimmerworld and a mesh window net that they offer. Additionally, a safecraft window net has also been purchased to utilize as part of the driver restraint system. In theory, this should help stop me from moving around in the car during secondary and tertiary impacts should I run the stupid thing into something (this would be very inconvenient) and the harness has already stretched out.
We are planning on mounting these nets in a similar fashion as seen on the Grand Am Mustang pictured below. Note the heim joint at the end of the rod. I will be using this solution for the (square) window net.
The whole chassis stiffness thing I saw a bit in radio control racing, as I designed my own chassis, but generally outdoor (low grip) conditions called for a more flexible chassis, whereas indoor (high grip) called for a stiffer one, as conditions can actually induce traction roll.
I always learned that you'd ideally want a perfectly stiff chassis so that all of the movement is controlled by the dampers, but I guess that theory would depend on ideal/perfect damping and spring characteristics which you aren't likely to get in real life, so a bit of chassis flex does it's job... to a point.
The whole chassis stiffness thing I saw a bit in radio control racing, as I designed my own chassis, but generally outdoor (low grip) conditions called for a more flexible chassis, whereas indoor (high grip) called for a stiffer one, as conditions can actually induce traction roll.
I always learned that you'd ideally want a perfectly stiff chassis so that all of the movement is controlled by the dampers, but I guess that theory would depend on ideal/perfect damping and spring characteristics which you aren't likely to get in real life, so a bit of chassis flex does it's job... to a point.
Thanks Peter, it goes to show that there is often more than one way to get something to do what you want, especially when the desired characteristics are dictated by the application.
I had also been meaning to ask you how your MK60 ABS conversion was going, as I had been thinking about adapting such a system. (I am re-plumbing the entire system for the pedal box and PFC caliper craziness and now would be the time to do it) The MK60E1 (from the euro spec 4-cylinder BMWs) looks to be suitable, but I will need to do more research.
Do you know if the ABS sensors (iirc you are using the RX-8 ones?) and the toothed wheel on the hub need to be accounted for in the software with a re-flash or something of that nature?
I'm working on getting everything together for the install, so that it's basically a bolt in. Shop time quotes for this are expensive, so I want to minimize the custom work.
I will be mounting the unit next to the MC, where the Sakebomb coil mount was (relocating them under the UIM), and I'll be adding a second OEM hard line to the rear of the car with short custom flex lines to turn the three channel into a four channel (thats actually the biggest hurdle, the fluid plumbing. i have a design for a unit mounting bracket in mind, I need to draw it and get it to sendcutsend.
I'm using the E46 wheel speed sensors, and picked up a set of front/rear adapters by someone who's done the conversion and has it working. Once I have all the needed flex lines spec'd and built by HEL Performance, it'll be ready to head to a shop for the install.
One thing I've thought about is how stiff many of us run these cars, it's certainly costing us grip in some situations. For me, I run them to minimize roll. That roll is exacerbated by the low ride heights I/we like to run. With the A-arms in the positions they are in, the roll center is likely under ground, and the car rolls more. A properly designed set of drop spindles that would restore the arms to reasonable angles at the ride heights we run, would theoretically reduce the roll and allow less aggressive rates.
I'm working (slowly) on those too, having struck out for years to convince any place to build them for me.
One thing I've thought about is how stiff many of us run these cars, it's certainly costing us grip in some situations. For me, I run them to minimize roll. That roll is exacerbated by the low ride heights I/we like to run. With the A-arms in the positions they are in, the roll center is likely under ground, and the car rolls more. A properly designed set of drop spindles that would restore the arms to reasonable angles at the ride heights we run, would theoretically reduce the roll and allow less aggressive rates.
I'm working (slowly) on those too, having struck out for years to convince any place to build them for me.
agreed, if you were looking at the FD from scratch (or any car), you'd look at the suspension geometry and figure out how much roll you can have, then look at the tires/grip, and then decide on a spring rate that gives you the amount of roll you want at max grip.
my friend and i always do it the dumb way though, we just add spring until it slows down
part of that is, we've learned, if there is an adjustment, you need to try it and see what it does, that way if you need to change the handling of the car later you know what does what. takes forever though
One thing I've thought about is how stiff many of us run these cars, it's certainly costing us grip in some situations. For me, I run them to minimize roll. That roll is exacerbated by the low ride heights I/we like to run. With the A-arms in the positions they are in, the roll center is likely under ground, and the car rolls more. A properly designed set of drop spindles that would restore the arms to reasonable angles at the ride heights we run, would theoretically reduce the roll and allow less aggressive rates.
I'm working (slowly) on those too, having struck out for years to convince any place to build them for me.
Do you already have a design or drawing for the spindles? I might be able to get them manufactured (will have to run this by my (alleged) engineering and manufacturing department). I believe we have the means to scan it too (though I am not sure if it has been set up yet)
I did some looking for some wheel hubs that affix with four smaller bolts instead of being affixed with one large nut like we have on these cars, and I think that this may allow us to lower the complexity of this undertaking by some amount. I was able to find a website that catalogs vehicles with compatible center bores and PCDs and it looks like the wheel bearing from a Mitsubishi Lancer Evolution X (and outlander) could work, but I'll need to determine the correct height such that it is mounted in the same place as the OE bearing.
It seems like most places are making theirs out of 6061 (we could do T6 temper or T651) aluminum. I am currently on a 7075-T651 kick as it appears to be one of the best materials for the job (with what little materials science knowledge I do have).
Note how the spindles are designed to accept a wheel bearing affixed with multiple bolts.
I'd gone so far as to talk with Keisler Automation, who made similar spindles for Miatas that converted them over to the RX8 wheel hub. I'm working on an idea that will allow the mounting of a stub axle for the standard hub, or an RX8 hub. If for no other reason than I have a mount for the MK60 for the standard hub config, but the RX8 hub has the ABS ring/sensor internally contaibed, and AFAIK its not compatible with MK60.
It's in the scanning/concept stage, and will certainly reach out when its further along.
11-18-23, 06:22 PM
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