The Official "RX8 in DSP" Thread
02-14-2015, 09:45 AM
#201
We have to work within the allowances of the class rules. Trying to do everything I can in that regard, but there are some conflicts between min weight and things like heat/airflow management (fan shroud vs just a small fan on the radiator shroudless), reliability (lighter S1 glass-box vs stout but heavier S2 trans), etc. The very first post of this thread discusses the allowances which there are many factory parts we either can't modify/change or they're hard to modify/replace without also making them heavier.
That said, lighter may not be better. It's a game of trying to figure out when the change will make the car faster regardless, like larger/heavier wheels & tires. When it's said and done, pulling weight from the front if an RX8 is much harder. Some of the bigger things were already allowed in the previous class like front brakes, exhaust system etc. So the biggest front weight reduction items now are clutch/flyweel, AC removal, emissions removal (air pump system, etc),radiator/fan/shroud system, engine oil/cooler system, etc.
But to give some more examples, we're allowed to change radiator but the replacement has to maintain the minimum width/height/thickness core dimensions as OE and attach at the same mounting points as OE. The only way to have a crossflow 2-pass radiator is to shorten the core width to fit the end tanks within the width of the frame rails/undershroud sides. So thats out. Then you're looking at just the conventional top/bottom end tank radiator just like OE. I never had cooling issues for what we do. Since the OE radiator is both dead light and adequate then IMO it doesn't make sense to change it.
We're allowed to modify the engine oil system externals so if you start looking at the oil cooler system the first thing you see is Mazda already made all the lines dead light. I'm not feeling like just one cooler in the OE front bumoer corner position is adequate. Not allowed to cut the OE shrouds/front bumper, so where can you put a large enough single cooler and vent it? It would have to be in front of the radiator. Scratch that. Unless you can find an oil cooler that's lighter than OE and also either as or more efficent than OE then IMO it doesn't make sense to change much there either.
and so on ....
Edit: oh wait, that was a joke about the missing engine trans, lol ...
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That said, lighter may not be better. It's a game of trying to figure out when the change will make the car faster regardless, like larger/heavier wheels & tires. When it's said and done, pulling weight from the front if an RX8 is much harder. Some of the bigger things were already allowed in the previous class like front brakes, exhaust system etc. So the biggest front weight reduction items now are clutch/flyweel, AC removal, emissions removal (air pump system, etc),radiator/fan/shroud system, engine oil/cooler system, etc.
But to give some more examples, we're allowed to change radiator but the replacement has to maintain the minimum width/height/thickness core dimensions as OE and attach at the same mounting points as OE. The only way to have a crossflow 2-pass radiator is to shorten the core width to fit the end tanks within the width of the frame rails/undershroud sides. So thats out. Then you're looking at just the conventional top/bottom end tank radiator just like OE. I never had cooling issues for what we do. Since the OE radiator is both dead light and adequate then IMO it doesn't make sense to change it.
We're allowed to modify the engine oil system externals so if you start looking at the oil cooler system the first thing you see is Mazda already made all the lines dead light. I'm not feeling like just one cooler in the OE front bumoer corner position is adequate. Not allowed to cut the OE shrouds/front bumper, so where can you put a large enough single cooler and vent it? It would have to be in front of the radiator. Scratch that. Unless you can find an oil cooler that's lighter than OE and also either as or more efficent than OE then IMO it doesn't make sense to change much there either.
and so on ....
Edit: oh wait, that was a joke about the missing engine trans, lol ...
.
Last edited by TeamRX8; 02-14-2015 at 09:48 AM.
02-14-2015, 03:34 PM
#202
Another wheel question
The ebay hub (yeah hush I know...) wouldn't fit with the clock spring still on. So we removed the clock spring, as seen in the pics attached I'm unsure if I can plug the resistor into this guy or do I need to plug the resistor into the airbag harness that comes off the clock spring?
She doesn't like how far out it comes, so we'll be getting a new hub and ngr slim quick release anyway. Hopefully the new hub will work with the clock spring still on (plugged in)
Thanks in advance for the help!!
The ebay hub (yeah hush I know...) wouldn't fit with the clock spring still on. So we removed the clock spring, as seen in the pics attached I'm unsure if I can plug the resistor into this guy or do I need to plug the resistor into the airbag harness that comes off the clock spring?
She doesn't like how far out it comes, so we'll be getting a new hub and ngr slim quick release anyway. Hopefully the new hub will work with the clock spring still on (plugged in)
Thanks in advance for the help!!
02-20-2015, 07:57 AM
#206
we reset the ecu and did the 21 brake thing when done.
only light on is airbag..
we do have trac control. idk about any sensor but the car seems to be working properly. at first it would start up, rev around 1400 for a sec, drop to 500 ish, then catch itself and hold at 900 ish
she hasnt complained so im assuming its working well. just too close to her she said, so a shorter hub adaptor will be ordered and possilbly a slim QR if the shorter hub still makes it come too far out
only light on is airbag..
we do have trac control. idk about any sensor but the car seems to be working properly. at first it would start up, rev around 1400 for a sec, drop to 500 ish, then catch itself and hold at 900 ish
she hasnt complained so im assuming its working well. just too close to her she said, so a shorter hub adaptor will be ordered and possilbly a slim QR if the shorter hub still makes it come too far out
03-02-2015, 12:18 AM
#209
FYI, back in Post#1 I had the 2009+ triangulated front strut bar listed as an applicable update/allowance. However update/backdate requires the part to bolt in and attach without modification to any attachment points. The rear bolt-in point for the 2009 tfiangulated strut bar is an additional bracket that attaches to the upper firewall/cowl. The problem is that to install this bracket on an S1 requires drilling the firewall/cowl to mount it. This isn't allowed, so in turn IMO the S2 3-point strut bar or equivalent replacement can't be used on an S1 chassis .... so I deleted it from the list at the beginning of the thread.
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03-11-2015, 01:00 AM
#210
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Fellas, I have a curiosity, I'm not in DSP this season but am thinking about it, I was looking at spring rates and reading Autocross to Win online and was focused among other things on this natural frequency thing and wanted to see what you guys thought about it or had heard.
Basically he says that for cars without Aero on slicks you want natural frequencies of 2.2F/2.5R there or thereabouts, which on the RX8 would be about 10k/11k assuming the car weighs 2900 and a fat driver like me is 270.
According to what Ive seen some guys run in street prepared and such that seems like a soft wheel rate, but when you consider that when those rates are coupled with the sway bars, you're looking at a roll stiffness of over 7000#ft/degree. Now Randy Pobst recently said that generally speaking your car will lean 1-3 degrees under max cornering with 1 degree being too stiff and 3 sacrificing some responsiveness, but with that 7000#ft/deg roll stiffness you'd need to corner at over 3 g's just to get the 2 degrees of lean!
They say a suspension has to work to work, and if everything is too stiff then its akin to using a solid chassis and relying on your tires to do alot of the shock absorption, which is good I guess if its cold and you need to work them but it seems like youre best off being a little softer.
I dunno I'm rambling at this point, I'm not trying to upset any conventional wisdom on spring rates but I'd love to be regaled with tales of what sort of trials and tribulations moved to establish the conventional wisdom. Hopefully something more than Mr XYZ did it and he's fast so we do it too, although that would be refreshingly honest to hear if it's the case.
Basically he says that for cars without Aero on slicks you want natural frequencies of 2.2F/2.5R there or thereabouts, which on the RX8 would be about 10k/11k assuming the car weighs 2900 and a fat driver like me is 270.
According to what Ive seen some guys run in street prepared and such that seems like a soft wheel rate, but when you consider that when those rates are coupled with the sway bars, you're looking at a roll stiffness of over 7000#ft/degree. Now Randy Pobst recently said that generally speaking your car will lean 1-3 degrees under max cornering with 1 degree being too stiff and 3 sacrificing some responsiveness, but with that 7000#ft/deg roll stiffness you'd need to corner at over 3 g's just to get the 2 degrees of lean!
They say a suspension has to work to work, and if everything is too stiff then its akin to using a solid chassis and relying on your tires to do alot of the shock absorption, which is good I guess if its cold and you need to work them but it seems like youre best off being a little softer.
I dunno I'm rambling at this point, I'm not trying to upset any conventional wisdom on spring rates but I'd love to be regaled with tales of what sort of trials and tribulations moved to establish the conventional wisdom. Hopefully something more than Mr XYZ did it and he's fast so we do it too, although that would be refreshingly honest to hear if it's the case.
03-11-2015, 10:53 AM
#212
Nathan, you're overthinking it. No amateur racer has enough tire data (not to mention stiffness & compliance data for the vehicle) to arrive at "ideal" spring rates using math. The natural frequencies (and the roll angle thing) are a rule of thumb that take the specifics of the vehicle out of the equation. It'll get you 75% of the way there, but cars--and especially production cars--are weird and you'll still have to tune to get it right.
Do you want to arrive at a particular roll rate using more bar or more spring? Do you understand why you'd pick one over the other? How does it affect what your shocks are doing in roll versus in pitching or ride motions?
For that matter, how did you arrive at your roll angle numbers? They change depending on where your roll center is, and the geometric roll center isn't actually where the car rolls around either. And how do you know that a certain amount of suspension travel is good? Compliances are going to play a much bigger part than you might think, and they could swamp out any well-intentioned calculations that you try to tune with.
I guess what I'm trying to say is that this stuff is complicated. For almost everyone, the answer is to start somewhere that is proven to be close and then take a lot of time to tune and tune and tune. Even the automotive OEM's with all of their engineers and simulation power rely on a few well-calibrated butts to dial in their vehicles' chassis characteristics. I think the story that you're looking for is that a lot of people tested and tuned to make their cars fast with certain tires, and a statistical analysis showed that they ended up within a certain range. It's unfortunately not very glamorous or straightforward.
Do you want to arrive at a particular roll rate using more bar or more spring? Do you understand why you'd pick one over the other? How does it affect what your shocks are doing in roll versus in pitching or ride motions?
For that matter, how did you arrive at your roll angle numbers? They change depending on where your roll center is, and the geometric roll center isn't actually where the car rolls around either. And how do you know that a certain amount of suspension travel is good? Compliances are going to play a much bigger part than you might think, and they could swamp out any well-intentioned calculations that you try to tune with.
I guess what I'm trying to say is that this stuff is complicated. For almost everyone, the answer is to start somewhere that is proven to be close and then take a lot of time to tune and tune and tune. Even the automotive OEM's with all of their engineers and simulation power rely on a few well-calibrated butts to dial in their vehicles' chassis characteristics. I think the story that you're looking for is that a lot of people tested and tuned to make their cars fast with certain tires, and a statistical analysis showed that they ended up within a certain range. It's unfortunately not very glamorous or straightforward.
03-11-2015, 05:35 PM
#213
in DSP the aero will impact it as well, the rear spoiler more so since the rule allowances favor it's handling impact more on an RX8 than the front splitter. In short, you will need a higher rear rate to compensate for a big rear spoiler. In fact, you probably won't want to make it as big as the rule allowance permits.
03-11-2015, 09:59 PM
#214
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Hmmm, DSP is a big can of worms :-P
I was using the public Fat Cat site to get the roll stiffness number so that's in question, I also had my fat-*** progress bar numbers in there which really raises that number alot.
also I was assuming I had a cg height of 17 inches (~18.5 stock, and I was lowered about 1.5" in STX trim) to get the roll angle as a function of lateral g.
The Nat freq. and roll angle thing like you had said was just rules of thumb yes, but I guess I was thinking if I came into DSP and there's not alot of shared data those rules of thumb could get me close.
I hadn't thought much about aero (probably cause I went to a Baja SAE school and not an FSAE school heheh) but I'll have to read up on that some more.
Man, there is so much tuning I would do if I had gobs of data acquisition stuff, I dont trust my butt entirely yet, maybe you guys are more sensitive than me haha
Here's a tire question for an R-comp newb, do you think a set of 275/35/17 A6's would last a whole season (10-15 events) with a codriver? I can find lots of widespread testimony on this but not so much that is RX8 specific.
Also any thoughts on the A7? it's supposed to last a little longer and drop off more gradually
Thanks fellas
Oh one more thing, I'm looking to source 17x10 +45..50 wheels for this, if anyone has an extra set they could part with, I'd be happy to purchase them. Additionally I'd like to offer an opportunity to buy them back at the end of the season in case you cant bring yourself to part with them permanantly, so I can sort of rent them so to speak just in case DSP isnt for me, just a thought.
I was using the public Fat Cat site to get the roll stiffness number so that's in question, I also had my fat-*** progress bar numbers in there which really raises that number alot.
also I was assuming I had a cg height of 17 inches (~18.5 stock, and I was lowered about 1.5" in STX trim) to get the roll angle as a function of lateral g.
The Nat freq. and roll angle thing like you had said was just rules of thumb yes, but I guess I was thinking if I came into DSP and there's not alot of shared data those rules of thumb could get me close.
I hadn't thought much about aero (probably cause I went to a Baja SAE school and not an FSAE school heheh) but I'll have to read up on that some more.
Man, there is so much tuning I would do if I had gobs of data acquisition stuff, I dont trust my butt entirely yet, maybe you guys are more sensitive than me haha
Here's a tire question for an R-comp newb, do you think a set of 275/35/17 A6's would last a whole season (10-15 events) with a codriver? I can find lots of widespread testimony on this but not so much that is RX8 specific.
Also any thoughts on the A7? it's supposed to last a little longer and drop off more gradually
Thanks fellas
Oh one more thing, I'm looking to source 17x10 +45..50 wheels for this, if anyone has an extra set they could part with, I'd be happy to purchase them. Additionally I'd like to offer an opportunity to buy them back at the end of the season in case you cant bring yourself to part with them permanantly, so I can sort of rent them so to speak just in case DSP isnt for me, just a thought.
Last edited by Nathan Atkins; 03-11-2015 at 11:26 PM.
03-11-2015, 11:52 PM
#215
Not the lightest, but cheap
ROTA Wheel RT5-R2 17x10 (5x114.3+50mm, 73 Hub, Hyper Black)|Rota Racing Wheel
ps: those who can't search, always are dependent on someone else ...
ROTA Wheel RT5-R2 17x10 (5x114.3+50mm, 73 Hub, Hyper Black)|Rota Racing Wheel
ps: those who can't search, always are dependent on someone else ...
03-12-2015, 07:02 AM
#216
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I looked up the Rota after I read you had mentioned you could buy three sets for the price of your modular wheels :-) I thought that was the wheel to get for my budget build! Rota seems to carry a very negative reputation from what I read though, i thought Id ask if anyone had a used set to sell for a similar price but higher quality.
Ive committed to CS for the season on encouragement from my buddy Danny who seems to think I could walk that class locally, but DSP seems alot more fun. I suppose as this season goes by I'll do as much learning as I can and try to come out swinging for 2016. Hopefully I'll have the knowledge the budget and the execution to not be totally embarrassing!
I'll be watching here to see how you guys develop and for videos and stuff
Ive committed to CS for the season on encouragement from my buddy Danny who seems to think I could walk that class locally, but DSP seems alot more fun. I suppose as this season goes by I'll do as much learning as I can and try to come out swinging for 2016. Hopefully I'll have the knowledge the budget and the execution to not be totally embarrassing!
I'll be watching here to see how you guys develop and for videos and stuff
03-25-2015, 06:18 AM
#218
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I was looking into cost of materials and workmanship to copycat the BHR long tube header and determined that their asking price is actually pretty damn reasonable. Any of you guys going with it? I'm curious what kind of results you see...
03-25-2015, 11:06 AM
#219
Building my own short tube to replace my worn out header that was built in 2006. Otherwise my thoughts on it are elsewhere on the forum.
If you already have a Racing Beat header and 3" midpipe then cutting the collector/OE flange off, fitting a 12* 3-way 1.75" x 3" race collector from Burns etc on it and then mate it to your 3" midpipe will get you very close. No additional tube length is necessary, but you can do that too if you believe in the tooth fairy ...
slip joints and clamps are cheaper and lighter than flanges too.
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If you already have a Racing Beat header and 3" midpipe then cutting the collector/OE flange off, fitting a 12* 3-way 1.75" x 3" race collector from Burns etc on it and then mate it to your 3" midpipe will get you very close. No additional tube length is necessary, but you can do that too if you believe in the tooth fairy ...
slip joints and clamps are cheaper and lighter than flanges too.
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Last edited by TeamRX8; 03-25-2015 at 11:10 AM.
03-25-2015, 03:34 PM
#220
If you can wait, 949 Racing is bringing back their 17x10's, supposedly this spring, but they have a history of pushing back release dates. The other option is Forgeline F14's, which come in a 17x10 with custom offsets for $335 each. Each option is apparently under 18lbs. There's also the used 17x10 6ULR option, if you can find any for sale.
03-25-2015, 06:12 PM
#221
ROTA supplies OE wheels for many manufacturers, the supposedly bad reputation is mostly intrawebz clowns parroting BS they know nothing about. Not to say they haven't had any failures. Rather, I have seen failures and bending in many wheel brands that nobody gets the least bit fracked out about.
Also a while back they released a notice about some copycat manufacturer in China selling fake ROTA wheels with the ROTA logos, markings, etc on them, so sometimes a bad wheel may not even have been made by them
Also a while back they released a notice about some copycat manufacturer in China selling fake ROTA wheels with the ROTA logos, markings, etc on them, so sometimes a bad wheel may not even have been made by them
03-27-2015, 08:28 PM
#222
What happened with mine, as far as I can tell, is that they took a wheel designed for a 4 bolt pattern and drilled it for a 5 bolt pattern for a small run of a special size (15x8, 40mm offset, 5x114.3). This meant that there were pockets in the back side of the hub (where they stamp or cast information) that had sharp corners within a couple mm of two lug holes in each wheel. Upon checking lug nut torque between sessions, I noticed one wouldn't tighten, so I investigated further and found a crack from one of those pockets through the lug hole. I took them all off at that point and swore off Rota.
I bought them back in 2007 from what I thought was a reputable vendor, so I'm pretty sure they're real Rotas, but it was a bit of an unusual situation. BUT they should NEVER have allowed those wheels off the drawing board, never mind out of the factory with such a design flaw. That's what really made me upset with them.
I bought them back in 2007 from what I thought was a reputable vendor, so I'm pretty sure they're real Rotas, but it was a bit of an unusual situation. BUT they should NEVER have allowed those wheels off the drawing board, never mind out of the factory with such a design flaw. That's what really made me upset with them.
03-28-2015, 12:00 AM
#223
I wasn't referring to your situation and don't doubt your story. Sometimes sh-t happens with any manufacturer ...
So I was just getting ready to put my engine back in and the friend I borrowed the engine hoist from needed it back due to a dropped valve on his car. So it will be another week or so for that, but I still have a ways to go regardless. Some things going on ...
Bought a Miata steering shaft adapter and quick disconnect from MiataCage.com. It requires some machining to work with the RX8 steering shaft sensor (not required in s true race application that deletes the sensor/turn signal assy), but is worth it for the low cost.
Installed the Racing Beat primary fuel injector Renesis dummy plug kit since those injectors and rail aren't going to be needed. Working through the rest of the engine bay fuel supply setup now.
Putting an S2 fuel pump in the RH saddle as the engine supply pump and extending the OE wiring to power it using the OE low/high speed strategy. The S1 pump wi be wired and plumbed separately to supply fuel from the LH saddle directly into the S2 fuel pump cup on the RH side. My goal is to wire it with a relay and a trigger tied to the LH level switch so that it turns on/off based on fuel level detection. Also a manual forced-on switch to transfer fuel to the RH saddle after dumping a 5 Gal fuel refill jug. The siphon strategy is completely eliminated as well.
Eliminated the OE oil fill and vacuum tank assembly from under the UIM. Decided to hold off on some more radical UIM mods until after I get the everything up and running ok first.
Having custom arms made for the front speedway bar setup I need with the deep offset/wide wheels I have. Can't get the new S2 rear arms installed until the engine is in, after which I can then move the car out of the back corner where it'll be easier to get to. Also bought a 4.77 S2 diff, but can't get my S1 diff out for the same reason and drop the OSGiken LSD for a refresh before slapping it in.
Laying out the radiator shroud & fan assembly this weekend along with the header pipe routing.
Don't really expect to have the car in competition until maybe late June/early July fue to being out of the country for 4 weeks ...
So I was just getting ready to put my engine back in and the friend I borrowed the engine hoist from needed it back due to a dropped valve on his car. So it will be another week or so for that, but I still have a ways to go regardless. Some things going on ...
Bought a Miata steering shaft adapter and quick disconnect from MiataCage.com. It requires some machining to work with the RX8 steering shaft sensor (not required in s true race application that deletes the sensor/turn signal assy), but is worth it for the low cost.
Installed the Racing Beat primary fuel injector Renesis dummy plug kit since those injectors and rail aren't going to be needed. Working through the rest of the engine bay fuel supply setup now.
Putting an S2 fuel pump in the RH saddle as the engine supply pump and extending the OE wiring to power it using the OE low/high speed strategy. The S1 pump wi be wired and plumbed separately to supply fuel from the LH saddle directly into the S2 fuel pump cup on the RH side. My goal is to wire it with a relay and a trigger tied to the LH level switch so that it turns on/off based on fuel level detection. Also a manual forced-on switch to transfer fuel to the RH saddle after dumping a 5 Gal fuel refill jug. The siphon strategy is completely eliminated as well.
Eliminated the OE oil fill and vacuum tank assembly from under the UIM. Decided to hold off on some more radical UIM mods until after I get the everything up and running ok first.
Having custom arms made for the front speedway bar setup I need with the deep offset/wide wheels I have. Can't get the new S2 rear arms installed until the engine is in, after which I can then move the car out of the back corner where it'll be easier to get to. Also bought a 4.77 S2 diff, but can't get my S1 diff out for the same reason and drop the OSGiken LSD for a refresh before slapping it in.
Laying out the radiator shroud & fan assembly this weekend along with the header pipe routing.
Don't really expect to have the car in competition until maybe late June/early July fue to being out of the country for 4 weeks ...
03-30-2015, 02:13 PM
#224
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Installed the Racing Beat primary fuel injector Renesis dummy plug kit since those injectors and rail aren't going to be needed.
Oh Nice, are you going with the Formula Mazda style intake manifold then and a couple injector throttle bodies?
That should get you 20+ hp based on the old rotaries/manifolds and what I have seen of Renesis Formula Mazda power charts.
Glad someone is going to take the fight to the BMWs with some HP. RX-8 chassis far outclasses the BMWs, just let down in power.
Having custom arms made for the front speedway bar setup I need with the deep offset/wide wheels I have.
Aww, bummer its not as easy as the FD where you can put in a shorter torsion tube.
03-30-2015, 07:34 PM
#225
The Pro Formula Mazda Renesis engines use the UIM with the same underpart removed, but only a single throttle body like OE. It's cable controlled rather than electronic with a MoTeC ecu. I still intend to use the Adaptronic because it needs the factory TB to work with the OE OMP.
I've been running my own custom speedway bar for years, but it has an interference issue with the wide high offset wheels. So I am going to a shorter tube, but this time chose to have someone else make the necessary arms to my specs to take some of the custom load off myself. It will use roller bearings rather than brass or urethane bushings. Also may run a rear speedway bar too.
Didn't make as much progress this past weekend as expected. In the short term I decided to order the RB header and modify it initially and pursue the custom header longer term. The custom header will incorporate a custom engine mount bracket already being fabricated this week which opens up the pipe routing possibilities quite a bit.
For future reference the S1 OE radiator core dimensions I measured are 25.50" wide x 14.13" high x 1.00" thick. Any aftermarket radiator must meet or exceed these dimensions to be SP legal (total weight too). The core can't be smaller in any dimension or the radiator itself can't weigh less. Still trying to confirm S2 radiator dimensions, which is an allowable UD/BD part. If anything it is bigger rather than smaller so likely not relevant.
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I've been running my own custom speedway bar for years, but it has an interference issue with the wide high offset wheels. So I am going to a shorter tube, but this time chose to have someone else make the necessary arms to my specs to take some of the custom load off myself. It will use roller bearings rather than brass or urethane bushings. Also may run a rear speedway bar too.
Didn't make as much progress this past weekend as expected. In the short term I decided to order the RB header and modify it initially and pursue the custom header longer term. The custom header will incorporate a custom engine mount bracket already being fabricated this week which opens up the pipe routing possibilities quite a bit.
For future reference the S1 OE radiator core dimensions I measured are 25.50" wide x 14.13" high x 1.00" thick. Any aftermarket radiator must meet or exceed these dimensions to be SP legal (total weight too). The core can't be smaller in any dimension or the radiator itself can't weigh less. Still trying to confirm S2 radiator dimensions, which is an allowable UD/BD part. If anything it is bigger rather than smaller so likely not relevant.
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Last edited by TeamRX8; 03-31-2015 at 06:51 PM.