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Automatic, Solo II, 12A

Old 12-13-02, 12:41 PM
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aheadau
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Automatic, Solo II, 12A

I am starting a project car for Street Prepared. Does anyone have any experience with racing an "automatic" 12A 1st Gen? Solo or drag.
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Old 12-14-02, 08:34 AM
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I autox'd once in my POS 85GSL auto. It's was dog *** slow. My advice is to shift it like a manual. I wish I had done that in hindsight.
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Old 12-14-02, 08:58 AM
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The "new" part of the project is a modified torque converter, to keep it spinning faster. Thanks.
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Old 12-14-02, 04:44 PM
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Is there a reason for keeping the auto?
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Old 12-14-02, 05:46 PM
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Left foot breaking. I have "worn" a RX-7 for 21 years, well over a million miles, and 350+ autocrosses. I am pretty good at "heel and toe", but have never been able to do it to "perfection". Nor have I found left foot breaking with a manual to be the perfect solution on every course. I have never driven an automatic RX-7 but for 2 years I drove a HS 85 Dodge Charger with a 2.2 automatic. The only options were a "Shelby" front bar and fully externally adjustable shocks all the way around. I was able to balance the car very well and did LFB 100% of the time. Even though the car was underpowered, and an "auto", I won every event in 2 regions in class, AND was the fastest on the index at one event each year. (This was the St. Louis and Southern Illinois Regions) It was NOT the fastest or best car in the class, but I became convinced that LFB (and balance) was far and away the way to go. I am curious if I can improve my results in the RX by going "auto". I intend to overcome the "no low end torque" aspect by mod. to the torque converter. So I am looking for any insight others may have into that area and the transmission itself. 1st Gens have become almost extict at the "Nationals" and I want to see if I can change that! I don't think anyone has tried that route in Solo (?) so I wanted to seek out "Drag" folks as well.
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Old 12-15-02, 08:13 PM
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Well one problem is that the auto is heavier than the manual. Since I wont have time to do a auto to manual swap anytime soon, and I refuse to haul my IT car to anymore SOLO II's, I might drive my auto in any autox's I attend. What kinda mod you planning on doing to your converter? You want my personal recipe for a national SOLO II contender in CSP? An SE built to the limit of the ITS rules. More ponies than a 12A, and killer handling. From what I've seen the nat'l courses are power courses. You need hp and handling to win. Course a good driver dont hurt either.
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Old 12-15-02, 08:14 PM
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WHy is Mr.Importguys face in my post?
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Old 12-17-02, 01:45 PM
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""the auto is heavier "",""An SE built to the limit of the ITS rules. More ponies than a 12A, ""

I don't think an "auto" is any more heavier then what the driver could stand to loose by diet!?? I also don't see the corner wieghts changing unreasonably either?? You think that a 13B prepared to ITS will generate more power than a 12A built to Steet Prepared??? Are not IT rules more restrictive than SP???

""a good driver dont hurt ""

Well, I can always use the car as an excuse then if needed! This IS an experiment to be sure. I have way more experience in Soloing RX-7s than I need to see your points (((I have "worn" a RX-7 for 21 years, well over a million miles, and 350+ autocrosses))), but I have wanted to try something different for a long time. After passing along 35 - 40 "7"s over the last 20 years, I finally have an automatic to play with. The plan is really simple really,,, eliminate any problem and excuse for not "left foot breaking" successfully 100% of the time, and eliminate the "problems" with an automatic in a car with no low end torque. The actual "mod" will no doubt be done by a shop with experience in converters (drag racing). I am posting to see if anyone out there has some insight into the mechanics of such a "mod", and / or racing experience with a "AUTO7" that they can share. What my hope is, is that I will have a "stall speed" high enough to get the car into the meat of the power band quickly after it gets moving,,,,gearing that allows the car to remain in one gear throughout 99.9% of Solo courses,,,,and engine preps that allow for good power well past 7,000 rpm (I have always been willing to "bury the tach"!). If I can find the "balance(s)" I should have a setup that will allow for quick acceleration and long legs at the high end. There are virtually NO 1st Gens at the "Nationals" in CSP and I want to see if there is another (successful) way to approach that,,,,What do I have to loose??? I have enough confidence in my driving ability to make a fair showing, IF this experiment works at all. It's a damn shame, I'm sure you will agree, that the most inovative sports car in hisory, gets shut out of competition. In the mid 80's I ran for 3 years uncompetively in ASP before SCCA finally gave it a break and moved it to "C". Of course, the car isn't getting slower, it's just that there has been so much improvement in newer cars.
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Old 12-17-02, 07:54 PM
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Oh Im not saying its not worth trying. And I'm not doubting your driving abilities, after all I dont even know you LOL. My reasoning for going ITS is that you automatically get more hp, stay in CSP, tkae advantage of being able to re gear the car, and gut it to drop some weight. But your idea may be a good way to go too
Good Luck and keep us posted on your progress, experieinces when you get it on the course.
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Old 12-18-02, 07:35 AM
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How much HP could you get with 13B in ITS???
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Old 12-18-02, 08:06 AM
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Well this is an educated guess.
ITA (12A) around 150hp, up from 105 stock- 50% increase.

ITS (13B) 135 stock, add 50%, 200hp?
Now you are wheel/tire width limited in IT, but you can re gear the car all you want. Couple that with bigger brakes and a G-Force suspension setup and you'll have one killer AutoX car.

Last edited by Rx7carl; 12-18-02 at 08:08 AM.
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Old 12-18-02, 10:41 AM
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##@$##@@# I'VE TRIED 3 TIMES TO DO THIS AND I KEEP LOOSING POWER!!
I'm going to shorten the post so maybe it will get in before the next PF.
You compared ITA to ITS but what we really need to compare is CSP to ITS. When I ran the 650 and front to back RB exhaust, the "guys" said I was at 160-165 HP. But this was NOT tested directly so,,??? Can you really gain 50% under ITS rules??? I didn't think you could , but I don't KNOW?? The tire/wheel limitation is a greater concern in Solo than road racing, yes/no??? So Street Prepared is a better deal?? If you COULD get 200 HP, could you get it to the ground effectively in Solo (under ITS rules) where you would be "digging" out of corners more with tighter turns and slower speeds??? Suspension should be about equal I would think??? Bigger brakes should not matter on a RX-7 in Solo, in fact I've seen some screw-ups on course when the metalic "racing" pads were not warm enough to work well. Brake fade would not be a concern without "LFB", and with it, I think the F & R discs are good enough, WITH the better pads of course.
So that leaves gearing.
No doubt that more selection is a plus. However, an automatic would have better range per gear (especially with a modified torque converter). At the lower end the converter would take up the slack (like slipping the clutch). At the high end, I would hope the engine would pull through a higher RPM. I routinely "trusted" the engine to go 8,000 or better, and with the "old" set-up I did not feel it was dropping off any in power at that speed. So that means that a single gear (2nd) would pull strong from 3,000 or so to 8,000,,,,5,000 RPM range. Below the stall speed the converter takes up the slack. As long as there is SOME choice in tire diameter for "fine tuning" I would hope to get the "proper" gearing.
Although I bring this up here recently, I've asked around many places for a long time, and have yet to find anybody that has tried this ANYWHERE. So maybe I'm really off base, or, this might be a novel approach?? I don't think I'm going to find out without DOING it. I find it hard to believe that no one has drag raced this way though, SO , HEY OUT THERE, ANYBODY?????
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Old 12-18-02, 11:11 AM
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I have never Autocrossed my auto (FD3s) but I have time trialed at Streets Of Willow Springs & Buttonwillow, I use LFB to allow me to keep the turbos spooled. The biggest DISADVANTAGE of the auto is the very TALL first gear +Rear end ratio, = to second in a 5 spd. That and the fact the the Trans always wants to shift up to second or third at 3500rpm for anything less than WOT. You HAVE to use the Hold feature and manually select the gears to hold the lower gears at part throttle.
I would recomment getting the lowest ring & pinion you can to allow a better launch onto the course (critical in Autocross) in first, and out of the slower corners in second.

Last edited by maxpesce; 12-18-02 at 11:14 AM.
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Old 12-18-02, 12:02 PM
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The truth is what I REALLY hoped to do, was to prepare a manual AND an automatic to identical specs (where possible of course) to truely get a good comparison. That's a little out of the budget though! My plan is to put the car together completely with no TC mod, and then select a target stall speed based on THAT experience, then, change or adjust other items as needed because of the mod....

As far as gearing, because of a higher stall speed, I think I MAY not need a lower ratio??? Also, I am a big believer that many people hurt themselves by going to too big a tire. The idea that you want the biggest "patch" on the pavement can be wrong. You want your tires to reach the best opperating temp. as soon as possible, and spreading the friction to accomplish that over a larger area, delays the proccess. Also "shorter" tires lower the center of gravity or roll center and that is always better.

maxpesce, and especially Rx7carl, what is YOUR stock stall speed??? The car I'm starting with is a '85 GSL (has the overdrive "auto") Do you happen to have the curb wieghts of a manual vs. auto???
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Old 12-20-02, 08:43 AM
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Ok, lets break this up by catagory.
ITA= 150hp approx
ITS= 190? approx?
CSP 12A= your approximating 160-165?
CSP 13B= lets guess 200-205?
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Old 12-20-02, 08:48 AM
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Suspensions would be roughly equal yes.
Wheel/tire limits in IT will hurt you I agree.
Bigger brakes will give you better pedal feel and modulation, so an SE based car WILL be better.
And running the proper pads for SOLO II will eliminate any heat related issues ( I use Hawk HPS).
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Old 12-20-02, 09:18 AM
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Ok, gearing. Thats where the IT rules win. Gearing with tire diameter is tough for us cause of our lack of low end torque. Big wide 15 rubber would be nice (CSP), but you'll lose all your torque. If your idea can compensate for this, then maybe your onto something, I dunno.
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Old 12-20-02, 09:27 AM
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racermike, wish I could help you on the weights, but I dunno. My auto is a daily driver POS, and I'm not hip on automatic trannys. What is stall speed and how do I check it?

I agree and disagree on your tire comments. I think a skinny enough tire to get to operating temp in a short solo II lap would not give max grip. And one thats too wide will not get sticky at all. It's probably a compromise between the 2 that is best.
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Old 12-20-02, 10:26 AM
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Yeah, the "compromise" on tires is what I was getting at. Often folks will go with the most possible rubber (patch) they can, and where as that may be good for track, it may be too much for solo. Even the "stickiest" tire won't get up to the "working temp" on some courses and on some cooler days. At a Divisional once I was using a wide and 50 series tire. When I had convinced myself that they were not working well (too low tire temp after run) I went back to a 175 70, and the car was much better, and I was back to picking up all the debri This was the same tire model, just in different sizes.
For wieght, I was just going by "feel" with it out of the car, compared to manual. I can't say how much different with out a scale, but it did not seem like much. Plus you need to take into account the flywheel and clutch.
Stall speed I believe can be checked by: with brakes on to prevent ANY tire rotation,,,floor the throttle. The highest tach reading, rpm, would be the stall speed.
When I got the test car running well enough to drive home (not well,, just well enough to drive!) (85 GSL) It seemed like the stall speed was about 1800 - 1900. It has been a while so I may not remember it right, and the car was not running well so it may have been a little different. It MAY have even had some issues WITH the TC and transmission. Obviously even 2,000 is not high enough to get into the real power, but how about 3,000 or 3,200? On course, no matter what gear you were in or what load, the engine would not get BELOW that stall speed. With left foot breaking, instead of lifting (all the way off) you can keep the engine "spooled" to that rpm, and have the meat of the power curve close at hand. At least thats what my thinking is. Drag racers use high stall speed TCs for the same reason, lots of power out of the hole (automatics instead of manuals). When the trans shifts gears, it starts at a higher rpm as well.
I want to see if butlips will chime in here. He may not know anything about automatics, but he may have a more informed opinion about the power available in each of the 4 class/motors we are comparing. I WILL be limited to the 12A for the "experiment", but if it works, the 13B might be next phase. I also want to get his list of prefered componants for 12A IT. I have 4 good bodies with no titles out back,,,,,,,lets see,,,,,IT, ClubRally, RallyCross, and a spare!
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Old 12-20-02, 11:26 AM
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Damn racermike! Long posts but good reading.

Ok, ill try that and tell you what my stall speed was. I think I see what your trying to do now. If I autox that pos this year I'll post findings.

LOL, dont give me any ideas. I already have 4 too!
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Old 12-20-02, 11:31 AM
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If you think it's long to read,,,,,I don't type,,,it's REALLY long to write!
mdb
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Old 12-20-02, 02:51 PM
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you need to spend more time here then

Anyway....Not fully warm, but almost, she stalled at 2400. This is a stock 12A engine, no mods 'cept CAI and no emissions.
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Old 12-20-02, 03:21 PM
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Interesting! I guess I need to find the factory spec on that. I don't recall seeing it anywhere before.
ANYONE?
So I guess you can see that if it were 1,000 or so higher you would move away quicker??
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Old 12-20-02, 03:55 PM
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Since Mike asked me to chime in, I'll add anything I can.

First of all, I've seen a lot of autoX cars with auto trannies. IMHO, the auto tranny is a mechanical hinderance (due to more lost HP in the drivetrain, not weight) but if you are more comfortable driving that way (and obviously a lot of folks are) then what you do behind the wheel will more than compensate for whatever is lost in the tranny.

I think that Carl's HP guesstimates may be a tad optomistic on the the 13B motors. My guess (and it's just that) is that a 13B prepared to CSP rules would closer to 190hp.

I'm not too familiar with the SoloII rules, but I can assure you that an ITA RX-7 doesn't have a prayer in CSP. My Dad has a great SoloII resume. He is a 4 time National Champion in the highly competitive CP class, and was named SoloII driver of the year after one of his National Championship drives. We took his ITA car (that he has well over 30 wins in) to a Divisional SoloII, and he got SPANKED by a GSL-SE that was prepared to CSP rules.
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Old 12-20-02, 03:58 PM
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2400-2650 per the FSM
Also they caution that you have to perform this test within 5 seconds, and allow sufficient cooling time between tests. I guess they arent that confident in their transmission? I dunno, maybe theyre afraid youll burn up the fluid?
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