Well, I got a big check from parents this Christmas (yes, I am 44 years old) so 20b is back on the table. I am just wondering if anyone has completed a 20b n/a and then wish they had done a turbo. It is not like you can just bolt on the turbo later and not be a bit concerned about the higher compression rotors. I am kind of digging the idea of staying n/a on the GTUs. I just don't want to get done and wish I had 125-200 more hp.

Also, what do you guys think would be a quarter mile time and 0-60 time for a FC 20b n/a, itb, 4.33, 2800lbs, 350rwhp?

I really need to ride in a higher hp FC. The fastest one I have had was about 275rwhp 88TII. The thought of taking the car as far as I am going to and still getting smoked by a stock Z06 still bugs me a bit.

 

go big or go home.......

TII tranny, aluminum flywheel, carbon fiber driveshaft version of Mazdatrix's TII tranny to NA rearend, 5.12 gears, torsen or clutch-type diff (probably the clutch-type in this situation), 20B with 9.7/10.0 rotors.



Hell, if you have cash to spare, lightened NA/RX-8 rotors, guru 2-piece e-shaft, rebalanced engine for 9k, 10k redline and transmission scatter shield to save your legs if your clutch lets go.

BTW, No one really goes NA for the straight-line/highway/drag performance......it's much better suited for a road course, where the lack of turbo lag allows you to get on the power quicker, as well as enter a corner harder.

If you care about highway pulls, go turbo, and be happy that your car's nickname can be "vette killer".

 

I got everything going there except the 5.12s. This is a street car.......Oh, I didn't get the carbon fiber shaft, just the regular one from Mazdatrix. I think that I had read GtoRx7 saying that he didn't see a difference with the rx8 rotors. We will definitely be lightening and balancing. Here is another chance to show my transmission find, 1991 original less than 1k miles.....notice the paper stickers are still perfect. Probably not going with the Guru e-shaft.

I like the simplicity and reliability of the n/a. There is an upside and downside to everything.

 

apparently, the 9.7 works better than the 10.0, but i think it's because of sealing issues.....the 9.7 produces better compression on the compression tester. If one can workaround those seal issues, then it should be all gravy.

If it's purely a street car, good thing you got the S5 TII transmission. .719 5th gear and a 4.33 rear end will be about 3200 rpms at 80 mph, which is acceptable.

If you're only interested in the 4.33 rear end, I would say, don't bother running an NA rearend, and convert to a full TII drivetrain. Mazdatrix has 4.33 gears for the 8 inch diffs (FD/TII). Since you're NA, you may want to gamble with the FD Torsen diff, since you won't be twisting the axles as much. Though, if you ever do break a diff, you can then switch to a S4 TII diff or a KAAZ/ATS/Cusco/OS Giken/etc.....

Then you could drop a cool grand for the Carbon Fiber driveshaft.

Since it's NA, a 10 lb aluminum flywheel mated to a street disc or 4 puck sprung clutch if you have the tolerance for it. Personally, if the car does the majority of the driving on the street, go with the street disc. That's just from personal experience and the two that I have now.

Hell, I'd say make sure the port will support breathing to 9000-10000 rpms and raise that redline! Make sure you install a scatter shield if you do that though. This is where I'd suggest both the guru e-shaft for less flex and the CF driveshaft in case you break a driveshaft. Maybe do chromoly axles too as another way to lighten rotational loads?

ooh....pretty transmission.

 

I have already purchased the 12.5 ACT Streetlite flywheel and ACT Street Performance Clutch from Corksport.

I think I will just beat on the rear and see what happens. I have talked to some people that have empirical evidence that the n/a rears can take quite a bit of abuse. I am not talking about 6000rpm drag launches but hard street driving. If it will stand up to my moderately hard driving I am just as well as not to have the extra weight of the TII rear.

Thanks for your input

 

why did you go with the NA rear?

It's not the rearend that's the weak point on the NA's, it's the trannies. An S4 clutch-type LSD can take a lot of abuse.

 

It is a 1989 GTUs. I comes with a 4.33 n/a differential from the factory. I will see how it does with the hp to come. If that doesn't hold up I will go with a S4 TII.

 

ic.....if you want to upgrade your diff, I would suggest either a Miata Torsen or TII drivetrain swap and use an FD torsen in your rearend.

I'm not fond of the stock viscous, even at 170 whp in my GTUs. I would much much rather have a torsen, or even a clutch-type on the track.

 

Rx8 Rotors are 2/3's the price of N/A Rotors. This is the way I would go, would like to see what it gives when done.

Personally, I would like to know what kind of a 20b N/A setup would deliver 350rwhp.

 

thats exactly what i was thinking...

NA 20b's with the stock intake manifolds and an open exhaust makes about 250whp... that's stock, with the 9.0 rotors and stock intake manifolds with the turbos removed.

i'm wondering how much power you would actually get from going to 9.7 rotors and ITB's. 100whp? seems like a lot.

has anyone actually dyno'd with a 9.7 3rotor with ITB's and a header/exhaust?

 

I don't exactly have that situation, but I wish I had just thrown the stock 20B-REW in the car rather than spending a lot of time and money messing with it first. The stock 20B-REW is the best bang for the buck, while converting to a NA or an aftermarket turbo takes a lot of time and money. I originally thought about running mine NA, but the porting required to get a decent amount of HP would have increased the exhaust noise to unstreetable levels. I don't think a NA 20B is a very good idea unless it is strictly for racing.

There are many drag racing calculators on the internet that will be a much better SWAG than random guessing from forum members. Examples:
http://www.slowgt.com/Calc1.htm#PerfHPWt
http://www.top-fuel-racing.com/tool.asp
http://www.pro-system.com/calc.html
http://www.golenengineservice.com/html/calculators.html

That would require bridge porting or peripheral porting.

 

Well I am more thinking:

Rx8 Rotors
ITB with Box Mated to tubing going to front bumper to NACA duct in the front bumper
Straight exhaust ofcourse with custom mani...

But I don't know, I wanna hear what people have to say because even @ 315rwhp region is seems attractive.

 

I put down 450hp to the ground and 444tq. I've broken 2 NA LSDs. I've had a S4 TII rear under my car for a year and beat on it everytime I pull out of the drive way. No noises yet. FWIW.

 

I am concerned about the noise. I just had a 6 port supercharged stock engine in and I thought it was loud with an Apexi GT exhaust.

I was thinking about Racing Beat Rev II presilencer and cat back, custom header and wrapping the whole thing. It seems that the fiber wrap would quite it down a bit. At least not so raspy.

I am definitely going drive a n/a before I pull the trigger.

 

how much for the tranny?

 

Not for sale......

I payed $500 for it.

 

Check out Defined Autoworks in the vendor section. You will see what GtoRx7 has done to his 3rd gen. It appears it is very possible to achieve.

 

I put my car on the dyno a few times over two years ago, 9.7:1 rotors, street port only, full custom header/exhaust, ITB intake setup. Made 310rwhp on mustang dyno with ECU issues, later 348rwhp problems fixed. So yes, its not too hard to do it. I sold my old ITB setup, and vs a stock intake, streetport, 9.0 rotors with header it gave him over 60rwhp on a dyno-dynamics.

 

I think you will like the power output, for some reason n/a always feels good. Turbo, the rush wears off, so you need more and more boost to get that feeling again.
Plus, a three rotor n/a wont even be phased by a 100shot if you still need more

 

don't I feel stupid =)

 

I think anyone who has completed a 20B conversion would just be happy to have the car finished and running rather than being a constant project (and drain on finances).

 

Word

 

http://www.youtube.com/watch?v=oEOHn7rspsk

I want something that sounds like this!

 

Nice... hadn't seen that YouTube video yet. Sweet. I want to see (and hear) more!

 

Evening,

You MAY want to consider the options with the Turbo on your 20B.
I personally would go that direction with one exception.

If I was making a road race 20B that was peripheral or Bridge ported, and completely 100 percent race. Then I would go N/A. (Like this car here http://www.youtube.com/watch?v=D8K9RGUF3Bo )

Otherwise, you should really take a ride in a FD that has over 450HP.. Not someone claiming to have that much. But actually that much to the wheels.

Sit in that car and let them roll into it gently in 2nd, and let it eat through 3rd 4th and well into 5th.

A friend Dewain used to have a FD that had 442 to the wheels, and I got to drive it back from palm beach after a Dyno-Tuning session, and let me say.. it was QUITE an eye opening experience. It really put into perspective the N/A VS Turbo differences to me.

I prefer the NA PP... but for the sensation of getting smashed to your seat when boost rolls in. Well. /shrug. It is what it is.