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E Production Rx-7 Build
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I'm turning a 91 Turbo 2 into an NA SCCA E-Production Rx-7. The car previously made 407rwhp with a GT35R and a 13B-RE, but I got tired of driving it on the street and am ready to start racing on a regional level.
Minimum weight, with driver, is 2300 lbs with the stock transmission. I would like to either swap another synchronized 5 speed box into it (can't change the number of gears) that has better ratios for circuit racing than the stock turbo 2 trans, or put a dog box in it, but that is down the road... I'm open to suggestions for that. Here are some pics of the fuel cell. It is a 12 gallon ATL bladder from a NASCAR with the NASCAR anti rollover devices. I fabricated the cover, fabricated the aluminum cage, and modified the can to include a flange for a removable cover. The can (not the cage) is being powder coated red, more pics of that and the fuel plumbing later. https://www.rx7club.com/attachment.p...1&d=1259525251 https://www.rx7club.com/attachment.p...2&d=1259525251 https://www.rx7club.com/attachment.p...3&d=1259525251 https://www.rx7club.com/attachment.p...4&d=1259525251 https://www.rx7club.com/attachment.p...5&d=1259525251 |
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Per the 2009 GCR, the minimum height of the fuel cell is 6 inches from the ground.
https://www.rx7club.com/attachment.p...7&d=1259525432 https://www.rx7club.com/attachment.p...8&d=1259525432 |
Looks pretty baller.
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Looks like a fun project. Better be sure the T2 stuff is legal in any form. IIRC its not. The diff and axles might be a problem. The T2 intake manifold won't fly either.
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Originally Posted by jgrewe
(Post 9648968)
Looks like a fun project. Better be sure the T2 stuff is legal in any form. IIRC its not. The diff and axles might be a problem. The T2 intake manifold won't fly either.
Copied from the 2009 GCR: o. Final Drive 1. Drive shaft(s) are unrestricted. 2. Final drive ratio is unrestricted. 3. Internal differential components are unrestricted. Electric control of the differential is prohibited. 4. Substitution of the differential housing is only permitted on front engine/front drive or rear engine/rear drive cars through the use of an alternate transaxle. 5. Axle shafts, bearings, bearing carriers, hubs, and universal joints/CV joints are unrestricted. 6. Transverse engine cars can rotate the engine about the crankshaft centerline to align axle shafts/constant velocity joints. On rear engine/rear drive cars the engine/drive train can be relocated vertically upward, to a maximum of one inch, to allow alignment of suspension and driveline components. |
#4 is the kicker, I've never had a T2 but they have a different rearend housing right?
Just don't open your hood with anybody else around. lol The stock NA intake manifold is the problem when keeping the EFI. And you're right, nobody will care until you beat them. |
But his car is a TII that has the turbo removed. The car was a TII as well, not just the engine.
I wonder if that effects anything. |
They don't care about VIN numbers in Production. Its all about the indivdual parts. Many of the T2 parts can be used because there are a lot of parts that are unrestricted in the rules.
Tha main parts that need to come from an 86-92 NA are the engine, brakes, diff housing, hood design(no scoop, but can be alternate material). Just about everything else can be replaced with an alternate material or alternate part performing the same function. |
I can use t2 brakes, they were also used on the GXL. The NA differential does use the same aluminum housing as the t2 diff; however, I'm not sure if the nose is the same.
Also, the control arms are unrestricted (but not suspension mounting points), so I could make tubular steel control arms if I desire. I am considering that option to lower the unsprung weight of the suspension system. |
The spec line is implied to apply to the NA cars only. The TII diff will not be legal. You won't need it anyway. The NA diff will hold the power of an EP car just fine and is lighter than the TII. You will want a 5.12 gear set for an EP car. Be prepared to shell out big money for this custom made gear set. A stock 4.10 will be horribly over geared.
You will need a high end dog-box to be competitive. The TII box should be legal, as alternate transmissions are legal, but the ratios will be terrible. The NA trans is fragile and the ratios are not ideal either. A Miata gear set in an NA case would have better ratios but will still be just as fragile. In the end you'll want/need a dog box. I would suggest beginning your racing in IT instead of Production. Will allow you to dip your foot in a much shallower pool (ie. less expensive, less demanding of expertise). You can build the car as an ITS car and upgrade to EP specs later on. There will be more competition in IT as well. Mid-Ohio often has 20+ cars in ITS at a normal regional. There might be 2-3 EP cars at the same race. Contact me through PM if you would like any advice on getting pointed in the right direction. |
Originally Posted by C. Ludwig
(Post 9650147)
The spec line is implied to apply to the NA cars only. The TII diff will not be legal. You won't need it anyway. The NA diff will hold the power of an EP car just fine and is lighter than the TII. You will want a 5.12 gear set for an EP car. Be prepared to shell out big money for this custom made gear set. A stock 4.10 will be horribly over geared.
You will need a high end dog-box to be competitive. The TII box should be legal, as alternate transmissions are legal, but the ratios will be terrible. The NA trans is fragile and the ratios are not ideal either. A Miata gear set in an NA case would have better ratios but will still be just as fragile. In the end you'll want/need a dog box. I would suggest beginning your racing in IT instead of Production. Will allow you to dip your foot in a much shallower pool (ie. less expensive, less demanding of expertise). You can build the car as an ITS car and upgrade to EP specs later on. There will be more competition in IT as well. Mid-Ohio often has 20+ cars in ITS at a normal regional. There might be 2-3 EP cars at the same race. Contact me through PM if you would like any advice on getting pointed in the right direction. The T2 diff is legal, as the differential is unrestricted. The reason I want to use it is that I already have a KAAZ in there. However, a concern of mine is the higher rotating mass, as well as the higher fluid friction forces due to the larger diameter ring gear. I'm not 100% sure about the nose. If that is different, then I'm not going to run it, and will end up selling it. The T2 trans sucks. I won't run it for long. I am looking into a mazda factory race transmission as an alternative, but there are (i think) fairly affordable T5 dogbox conversions that can be readily adapted to rotary bolt patterns. I am going to start by PDXing for a season to get my braking zones in tune, then hopefully move up to competition. Who knows, I may change my mind by the time that happens anyway. |
Originally Posted by shm21284
(Post 9650540)
The T2 diff is legal, as the differential is unrestricted. The reason I want to use it is that I already have a KAAZ in there. However, a concern of mine is the higher rotating mass, as well as the higher fluid friction forces due to the larger diameter ring gear. I'm not 100% sure about the nose. If that is different, then I'm not going to run it, and will end up selling it.
The S4 clutch type diff is a good for racing when properly setup. There are a couple shops that can do it for you, or it's very easy to put the parts together yourself. Getting the right combination of clutch thicknesses to properly set the break out torque can be an important part of the setup though and having someone's experience to lean on is nice. If you build it yourself Mazda Speed has various thickness clutches available. IMO, the Torsen from the Miata (while popular in racing), is a poor choice. |
Thanks a lot for the info! I'll look at selling the KAAZ then...
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seth, this is some nice work. I would give anything to be done with college and down there hanging out right now.
all in good time. cheers bro! |
^ Who even are you. Look at me NATEFRAME, that man with the caps lock!!! Pfffttt... have fun in Flint.
BTW, hows teh 7 running Nate? |
I bought the tubing bender and flare tool today. Need to get some aluminum tubing and the Toyota Supra fuel pump, fab up a bracket for the pump, make the surge tank, and bracket for the external pump and filter this weekend. Probably won't all be done.
I'll post up some pictures of the powder coating tomorrow if I remember to take my camera in. Ludwig, I think if I raced ITS first I would have to run a larger diameter roll cage. I don't want to order 2 die sets and make the cage twice... |
Originally Posted by shm21284
(Post 9653538)
Ludwig, I think if I raced ITS first I would have to run a larger diameter roll cage. I don't want to order 2 die sets and make the cage twice... |
Either way, the ITS rx7 is 2800 lbs, so it falls out of the weight range set forth on the contradicting tables.
Honestly, I like the level of build that is presented by E production. Being a mechanical engineer, I probably enjoy the build and design process more than the competition aspect. If my car turns out to be kickass, maybe someone else will drive it! |
Originally Posted by shm21284
(Post 9654476)
Either way, the ITS rx7 is 2800 lbs, so it falls out of the weight range set forth on the contradicting tables.
Honestly, I like the level of build that is presented by E production. Being a mechanical engineer, I probably enjoy the build and design process more than the competition aspect. If my car turns out to be kickass, maybe someone else will drive it! If you need a coach/driver I know a guy that's won a race or two. ;) You got anyone working with you on the engine and engine management? |
I'm getting some advise from Carlos Lopez as far as rotors go. The immediate concern is to just get the RE going so the car is running, but eventually a dog box and a 6 port engine is in line.
I plan on using carbon apex seals, so a solid tune is a MUST. Got any suggestions for engine prep and tuning? I plan to do all the porting and assembly myself. I don't have the $$ to pay for an engine prep. I understand most people don't like to share secrets, though... |
Carlos will point you in the right direction. I did notice poking through the rule book that rotors are free. That should allow you to run the aluminum rotors from E&J. Certainly expensive, but when you look at what it costs to get a pair of rotors setup from Carlos they're not too far out off the ballpark. I would imagine, given the promising results the aluminum rotors are seeing, they'll become THE thing in Prod before long.
The scalloping that Carlos does will work well with the street port requirement of Prod. Again, he's a wealth of knowledge and will point you in the right direction. When you get ready for engine management give me a shout. Would love to work with a Prod car. We've had a lot of success in ITS. Would be nice to step up to the next level. |
^ I will vouch for C. Ludwig.
He was definitely helpful when I sent him 10,000 emails about setting up my Haltech. He even responded to one on his Honeymoon, much to his wife's dismay I am guessing. |
farberio? what kind of a screen name is that. something tells me we have met before.
I bet i know where. my seven is dead in the ditch. too much homework to finish wiring it. |
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Originally Posted by NATEFRAME
(Post 9655206)
farberio? what kind of a screen name is that. something tells me we have met before.
I bet i know where. my seven is dead in the ditch. too much homework to finish wiring it. Shm, it looks pretty sweet in red! |
red? I expected white or black knowing your car. How did you pick red?
Looks kick ass, going to do your suspension too? Havefun! |
Why do the suspension? Costs too much for things that are prone to be heated up and bent straight when you crash the car. I will admit, it would look nice, but this is no show car....
Red is traditional fuel cell color. |
your not supposted to wreck the car. yes it is possible. hopfully it wont happan.
10.5 hrs of homework today, a new record! |
It WILL happen, its racing.
The fuel pump came, and the tubing bender and flare for the fuel lines should be here this week. Also, the pipe bender came for the roll cage. I will have lots of pics around christmas time! |
dude, gotta stop taking everything I say so literally.
I guess I should have said dont wreck your car and dont kill yourself, then i would have no one to talk about rx7's with. hopfully your sweet roll cage will protect your cranium, going to share any of the cad pictures? |
Originally Posted by NATEFRAME
(Post 9663718)
dude, gotta stop taking everything I say so literally.
I guess I should have said dont wreck your car and dont kill yourself, then i would have no one to talk about rx7's with. hopfully your sweet roll cage will protect your cranium, going to share any of the cad pictures? |
Originally Posted by NATEFRAME
(Post 9663718)
dude, gotta stop taking everything I say so literally.
I guess I should have said dont wreck your car and dont kill yourself, then i would have no one to talk about rx7's with. hopfully your sweet roll cage will protect your cranium, going to share any of the cad pictures? Should I post the CAD pictures tonight, or should I wait until I get the cage done before I post anything? FEA too? |
Just got some tools in
Well, selling parts off my old setup has helped fund some new goodies: TOOLS!
I bought a JD Squared tubing bender for the roll cage (the die was not installed at the point of this picture): http://i916.photobucket.com/albums/a...ingBender1.jpg Which put a very nice test bend on this piece (sorry for the crappy photo - cell phone): http://i916.photobucket.com/albums/a...4/BentTube.jpg And I bought a few Rigid tools for the fuel lines and oil lines on the engine. You wouldn't believe how much cheaper and lighter it is to run 6061 aluminum hard line, even after the purchase of a $100 flare tool and $100 bender. The nuts that bolt the flare to the male AN fitting are like $2-$3 each, plus $2 for a sleeve. Instead of $25-$50 for each hose end. http://i916.photobucket.com/albums/a...igidTools1.jpg SAE 37 degree flare tool. This works for JIC fittings (AN - Army Navy fittings is JIC) from 1/4" OD to 3/4" OD tubing/hose (that's 4/16" or -04 and 12/16" or -12 for the AN guys): http://i916.photobucket.com/albums/a...igidTools5.jpg Rigid Tri bender this thing was only $35 - parts of it are made in china >:-( BUT, it will get the job done just fine. It handes 1/4", 5/16", and 3/8" (-04, -05, -06) http://i916.photobucket.com/albums/a...igidTools3.jpg And last but not least, the behemoth of a bender, the Rigid bender for 5/8" OD (AN -10) tubing. This thing will handle stainless, mild steel, copper, and aluminum tubing of various thicknesses. Its like 2 feet long and 15 pounds with a 2.25" CLR, which is sort of large, but it gives the flexibility of putting multiple bends in a small area. I'll be using this for my oil lines on the engine and possibly to and from the oil cooler (with a flexible line from the engine to the chassis, of course). http://i916.photobucket.com/albums/a...igidTools2.jpg |
More Fuel Cell Pictures
Here, you can see the kevlar bladder, the high quality foam, and the corner trap door pickup.
http://i916.photobucket.com/albums/a.../FuelCell3.jpg http://i916.photobucket.com/albums/a.../FuelCell7.jpg http://i916.photobucket.com/albums/a.../FuelCell6.jpg http://i916.photobucket.com/albums/a.../FuelCell4.jpg |
Roll Cage Preliminary Design: CAD and FEA
In my quest for light weight, low center of gravity, and high torsional rigidity, I spent some time on roll cage design. I took some rough measurements of the stripped interior of the vehicle, located some good mounting points, and started designing.
I used Unigraphics NX to design the cage. The main purpose of the CAD work was to visualize the structure, then set up a geometry in which I could FEA (Finite Element Analysis) to further analyze high stress and high deflection areas of the structure. One of the highest stress areas of a cage, under normal racing operation (what I call racing forces), are joints. This is an area where forces must turn a sharp angle and transmit themselves along (possibly) poor moments of inertia, such as the base of a cantilevered beam, or simply a 90 degree joint. This creates stress risers and raises deflection. To counteract this effect, one applies gussets. To simplify analysis and engineering time, I did the finite element analysis on a selected 90 degree joint in the structuer and studied the differences between various gusset designs to find the best comprimise of weight vs. stiffness. Unigraphics NX will can calculate the volume of material used; and hence, a mass. And if you know the exact density of the material, a weight. The following pictures depict my design and analysis of the roll cage structure. The design is not complete. I have picked up a paper illustrating the energy absorbing characteristics of tubular structures, which I plan to incorporate into my design to make not only an ultra stiff and ultra lightweight structure, but also an ultra safe structure (think 1959 Chevy Bel Aire compared to Chevrolet Malibu - they achieved all 3). Thanks to NATEFRAME for locating and printing the article for me! CAD and FEA of Gusset Designs, and comparison to a joint with no gusset: Joint with no gusset http://i916.photobucket.com/albums/a...No_Gusset1.jpg http://i916.photobucket.com/albums/a...No_Gusset2.jpg http://i916.photobucket.com/albums/a...eflection1.jpg http://i916.photobucket.com/albums/a...setstress1.jpg Joint with tubular gusset - the common roll cage design. The 2nd heaviest and the 2nd most stiff (not by much) http://i916.photobucket.com/albums/a...be_Gusset1.jpg http://i916.photobucket.com/albums/a...be_Gusset2.jpg http://i916.photobucket.com/albums/a...eflection1.jpg http://i916.photobucket.com/albums/a...et_Stress1.jpg Joint with plate gusset: http://i916.photobucket.com/albums/a...te_Gusset1.jpg http://i916.photobucket.com/albums/a...te_Gusset3.jpg http://i916.photobucket.com/albums/a...eflection1.jpg |
More Roll Cage CAD and FEA
Joint with dual plate gussets - slotted (Heavies - not by much. And stiffest - by a fair margin)
http://i916.photobucket.com/albums/a...t_Slotted1.jpg http://i916.photobucket.com/albums/a...t_Slotted2.jpg http://i916.photobucket.com/albums/a...t_Slotted3.jpg http://i916.photobucket.com/albums/a...t_Slotted4.jpg http://i916.photobucket.com/albums/a...t_Slotted5.jpg http://i916.photobucket.com/albums/a...t_Slotted6.jpg http://i916.photobucket.com/albums/a...t_Slotted7.jpg Preliminary roll cage design: http://i916.photobucket.com/albums/a...ollCageV11.jpg http://i916.photobucket.com/albums/a...ollCageV12.jpg http://i916.photobucket.com/albums/a...ollCageV13.jpg http://i916.photobucket.com/albums/a...ollCageV14.jpg http://i916.photobucket.com/albums/a...ollCageV15.jpg |
More Roll Cage CAD and FEA
Roll cage with gussets added - slots not modelled - took too much time to model those things.
http://i916.photobucket.com/albums/a...llCageV110.jpg http://i916.photobucket.com/albums/a...llCageV111.jpg http://i916.photobucket.com/albums/a...ollCageV18.jpg http://i916.photobucket.com/albums/a...ollCageV19.jpg |
great work!
i cant wait to see this project when its done |
How tall are you? You may want to bow the "harness" bar to allow for more room there. Other than that, looks nice. The stress analysis is interesting. Make sure to consider what you're running through the firewall to triangulate the front end and how it fits with the rest of the design.
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Originally Posted by C. Ludwig
(Post 9671218)
How tall are you? You may want to bow the "harness" bar to allow for more room there. Other than that, looks nice. The stress analysis is interesting. Make sure to consider what you're running through the firewall to triangulate the front end and how it fits with the rest of the design.
Also, I haven't had time to measure the dimensions through the firewall. The analysis on the entire cage won't happen until the basic structure is finished. I am trying to optimize gusset location, thicknesses, and dimensions. If I had an entire CAD model of the car, this would be a lot easier! |
whats the latest on this?
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Final exams have been crazy. I'll be starting back on this project tomorrow. I'll be plumbing the fuel system and starting on the roll cage; but I have a dilemma - I am not sure how I'm going to get the base plates for the roll cage cut since I don't have a bandsaw.
Cheers. |
You can save weight and time and make a stronger cage if you skip the NASCAR door bars on the passenger side.
FEA is fun to play with but remember you have a car attached to this cage. There is a lot of extra weight in the form of overkill in your design. The chassis really only needs to be about 4 times stiffer than your suspension is capable of loading it. The focus should be on drivers side crush protection(move your seat over to the tunnel) and top of the windshield. The top of the windshield is where every sedan takes the hardest hit if it goes over. Here is mine in the cage thread, posts 319 and 323. https://www.rx7club.com/race-car-tech-103/show-pics-your-cages-please-395960/page13/ |
Originally Posted by jgrewe
(Post 9683800)
You can save weight and time and make a stronger cage if you skip the NASCAR door bars on the passenger side.
FEA is fun to play with but remember you have a car attached to this cage. There is a lot of extra weight in the form of overkill in your design. The chassis really only needs to be about 4 times stiffer than your suspension is capable of loading it. The focus should be on drivers side crush protection(move your seat over to the tunnel) and top of the windshield. The top of the windshield is where every sedan takes the hardest hit if it goes over. Here is mine in the cage thread, posts 319 and 323. https://www.rx7club.com/showthread.php?t=395960&page=13 The extra x-bracing bars are 1"OD x 0.049 wall... By the way, nice looking cage, I may have to use some features from your cage for ideas on my design, weight permitting. It seems as though my cage is most lacking the roll over protection. |
Also, I especially like your use of the passenger compartment for increasing lateral and torsional rigidity.
However, I'm not quite sure what you mean by "the chassis really only needs to be about 4 times stiffer than your suspension is capable of loading it." Do you mean that the chassis should yield at 4 times the load of the maximum lateral g's encountered in cornering? Or should it fail at 4 times that load? Or is it either one of those but instead of just lateral g's, is it the combined loading of spring forces and lateral g's? Stiffness (more properly, the modulus of elasticity) is the stress (force/area) vs. the strain (% deflection). The steeper the slope on the stress-strain curve, the stiffer the material. It makes no statement about the factor of safety regarding yielding or failure. You can see why I'm in a quandary over your statement. |
Your looking for resistance to the twisting of the chassis. A full tube frame chassis will come in around 12,000lbs/degree, I've seen them come in at over 14K/degree but you would never be able to tell the difference on the track.
With FEA you would pin down the back using the spring perches and put a load on the front spring perches to twist. Its been about 16 years since I played with UAI NASTRAN( I think its MSC NASTRAN now?) I would have to dust off the nodes and elements department in my brain to converse at your 'final exams-crammed skull' level. |
Yes, it iss MSC Nastran now, but there are other ones that are just as good, such as ABAQUS. I am using unigraphics integrated solver, structures PE, which works fine for linear statics solutions. I am not looking at yielding, over-loading failure, or fatigue failure.
My design goal is to have the maximum stiffness for the minimum weight. If there is a marginal, say 5% loss in stiffness for a 3% loss in weight, I would apt for the lower weight, as the car is light, and as you say, you may not even notice it on the track. I will most likeley incorporate some features of your design. I had a smiliar idea for the tubes passing through the firewall, but I didn't model them. Also, I had the same idea, but didn't model it, for the diagonal bar that goes from the right front corner of the cage back to the left rear shock tower. The thing I tried to keep in mind is that lateral forces in the rear are passed through the subframe, not the shock top, so I am attempting to use that as the point to stiffen for torsional rigidity. I may lighten up my rear "strut tower" for this reason. |
Surge Tank
Niagara Foot Shear
One of my new tools in my arsenal. This thing makes life much easier. Its probably older than my age*3... http://i916.photobucket.com/albums/a...agaraShear.jpg National Box and Pan Hand Break Another new tool in my arsenal. Again, makes life easier. Here's the setup I had to use to make a box: http://i916.photobucket.com/albums/a...rgeTank004.jpg Surge Tank Fabrication Breaking the plate into a box: http://i916.photobucket.com/albums/a...rgeTank002.jpg http://i916.photobucket.com/albums/a...rgeTank003.jpg Tack welded together http://i916.photobucket.com/albums/a...rgeTank007.jpg Welded the seam. This one was OK. I went back over the welds without filler rod to ensure that it didn't leak. Normally, I wouldn't do this, but its fuel, and it could be under pressure if there's a failure in the fuel system (nominally, its not under any pressure). http://i916.photobucket.com/albums/a...rgeTank008.jpg Fabricating the baffle inside. I wanted to make sure there was no possible way for the engine to be starved of fuel, even if the tank was low and I was mid corner, then powering out. http://i916.photobucket.com/albums/a...rgeTank010.jpg http://i916.photobucket.com/albums/a...rgeTank011.jpg http://i916.photobucket.com/albums/a...rgeTank012.jpg http://i916.photobucket.com/albums/a...rgeTank013.jpg There will be more pictures tomorrow of the finished surge tank (forgot to take pictures today) as well as the mounting of the surge tank, and the plumbing of all the lines. |
Surge Tank and Fuel Line Plumbing
Finished up the surge tank and mounted it
http://i916.photobucket.com/albums/a...urgeTank16.jpg http://i916.photobucket.com/albums/a...urgeTank17.jpg http://i916.photobucket.com/albums/a...urgeTank18.jpg http://i916.photobucket.com/albums/a...FuelCell27.jpg Started plumbing the fuel lines This is my first attempt at hard fuel lines. I was attracted to these for both price and weight. They are much lighter than the stainless braided line, and somewhat lighter than the nylon braided line. http://i916.photobucket.com/albums/a...FuelCell28.jpg http://i916.photobucket.com/albums/a...FuelCell29.jpg http://i916.photobucket.com/albums/a...FuelCell30.jpg http://i916.photobucket.com/albums/a...FuelCell31.jpg http://i916.photobucket.com/albums/a...FuelCell35.jpg http://i916.photobucket.com/albums/a...FuelCell36.jpg http://i916.photobucket.com/albums/a...FuelCell37.jpg |
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