GTUs and Efini (4.3:1) vs all the rest (4.1:1)?


I am sure that this discussion has come up before, but I am curious as to what the major difference is with these two gear ratios when it comes to performace, and why did Mazda elect to give a 4.3:1 to both the GTUs and the Efini only?

I am interested in doing a Turbo swap into a GTUs and was wondering if I should swap out the rear ends or cruise around in the GTUs rear end?

Thanks

 

FYI, the higher the ratio, the better the acceleration, but the poorer the top speed.

The Infini and the GTUs would therefore have better get up and go, but a marginally decreased top end (due to the rev limiter in 5th gear being at a lower speed).

On the other hand, you don't want too high of a ratio on a car that has a lot of power, since you'll spin the tires, so a lower ratio is better for a car with lots of power, since you gain the benifit of a higher top speed.

You'll also have to shift more with a 4.3 than you would with a 4.1.

 

Thanks for the information Valkyrie!

Mike

 

want the same effect for less money? find a pair of cheap 15" wheels, and put some short rubber on em'. Bam, shorter gearing; you can even get em' in "nice'n'sticky" formula and knock out 2 birds w/ 1 stone.

 

According to Isao Tohda [his first production car], the GTUs was orginially supposed to get a Non Turbo 20B. When the gas consumption and costs to retool the cooling system came back, Mazda pulled the plug and instead tried to mask the lack of power with the 4.3 rear end.

 

Damn, would have been awesome to see a factory N/A 20B.

 

Not more often, just earlier.

 

So the 4.3 was obviously faster to redline, and had more getup and go than the 4.1...

So let's say I infact drop a 13BT and tranny into a GTUs, would it be better just to swap out the rear end also? I will not be running a factory motor and turbo. I will be using a t66 turbo or larger, and the motor will be ported as well, along with the usual goodies fmic, stand alone, etc. etc.. So with that kind of HP gain I really don't want to reach my redline any sooner than I have to?

 

Well, with the 4.3, if you are going to 1/4 race it, will have a better time compared to the 4.1, but not much, but the 4.1 will have a higher top speed, but not much. The 4.3 will accelerate out of a corner slightly faster than the 4.1, but in all, there really isn't much of a difference. You can go either way, but leaving it in there would cost less. Why would you not want to hit redline as fast as possible? The faster you can reach it, the quicker the car will be through the gears as it is accelerating.

 

I wonder if there are a crap load of 20B's just siting around in solitude from this.

 

It is my understanding that the non turbo 20B never made it out of prototyping.

They would not have even started engine production if they hadn't got all the bugs out of the cooling system on the prototype cars.

But it does make me intrested in building a non turbo 9 port 20B

 

I guess when it comes to the two rear ends it comes down to the old saying "six of one half dozen of the other"

I'm not sure why I wouldn't want to hit the redline faster? An oversight on my part. =0)

 

Supposedly, according to the Mazda tech at the local dealership (well, this is what he told my dad), there was a very limited production of suped-up second generation RX-7s that were sold I think only to dealer owners, and within a few weeks of them being sold, 75% of them had been wrecked... Including the one that belonged to the owner of this particular dealership!

Don't know whether that story has anything to do with it...

I personally think he's full of crap, though.

 

20B N/A would be a first. Go for it.
That answers the question about the 200hp N/A thread that's floating around!

 

I would probbaly try and fit using the GTUs rear end unless you are dragging where the extra power handling of a Turbo rear end will come in handy.

 

Yeah, rough near stock estimates would put a non turbo 20B around 225 HP and 210 Ft/lbs

and 11 MPG

 

would the 20TT be a good canidate for an N/A? or would the time and effort to retool the ports and trying to get it wired up be too much?

 

i got 19.9 mpg with my 20b going down to sevenstock. granted in an s4 (small gas tank) you actually could watch the gas guage move when you're on it

 

Wait, whens the last time you saw a stock NA or even T2 hit the rev limit in 5th? (170+mph). Gas mileage might be affected but unless your pushing 350hp+ your not going to see the top of 5th.

 

The govern in your ecu wont let you get past 130

 

Reguardless, it effects the theoretical top speed, assuming you've got the stock rev limiter.

 

Huh? I've gotten over 145 (on speedo) with the stock ECU.

 

N/a ?

 

i dont think these cars are ecu limited on top speed seeing as how the ecu has no way of knowing how fast you going. the speedo is mechanical

 

Yes it does... and for that matter, the Japanese-spec FC DOES have a speed limiter (180 KM/H).