As it sits now it is an 85 gsl-se with turbo 2 series 5 engine and trans, full swap, haltech e6k ect...The motor has bad oil seals and I am about to take on a 4g63 swap into it..I would have never guessed a 4g63 block would bolt right up to the mazda trans but from what I hear, it does..Same bellhousing as mightymax

 

Are you 100% sure?? What year trannys? What about the clutch? Will you use a dsm motor or evo motor? More info please!!!!

 

lol the 2nd gen mazda trans works with the WIDE block 4g63 block or 4g64 from what I have heard..Pop in an ACT2600 dsm clutch and you have gravy I'm personally looking into a 4g64 block, possibly do a minor build to it and run a borg warner turbo (low compression high boost)..Very budget style and make up a NICE rear end (sheetmetal in the trunk) with some nice grabbers.

 

I'm really interested in this combo. Sounds like a fun car.

 

hey, i'll buy your series 5 motor if you do the swap, i'm rotary all the way!!!

 

best post in here. last sentence is the best one.

Here's an example that most of the mustang guys will attest to. A stock foxbody car (1987-2002) runs the 1/4mile at 14.0 at 98 or so mph. Stock configuration puts the rear-end ratio from 2.73-3.08 to 1 ratio. Swapping out the ring and pinion to a 3.73-4.10 to 1 ratio (along with a sticky tire) drops the car down to mid 13's @ 95 or so mph. The mph is lower because the car gets to the line quicker, not based on any drop in power. Keep in mind that the stock gearing allows you to complete the 1/4mile in 3rd gear. Moving up in gearing forces you to use 4th gear to complete the run. An additional shift still yielding a lower et.

 

Taller gear ratio's help if you have tractive limitations. There are several SAE papers on this (it's been beat like a dead horse) Reduces the amount of drive thrust and helps get the car out of the hole better.

Also you have to match your gear ratio to your powerband (not torque), and account for your aerodynamic drag. Then you can match your gear ratio to suit your needs.

There are very common spread sheets that show this.

To take 1 example where a shorter gear ratio helps, is no where near proof that your thoughts are correct. You can easily do the math to come up with the correct gear ratio to suit your engine/trans combination.

 

in above example I will do some math for you. I am rounding off so as to not spend too much time.
shift to 5th takes .5 seconds. goes from 123mph to 122.5mph. (exaggerated. doesnt look like it looses even that much)

if car didnt have to shift it would have gained more speed. estimate at end of .5 seconds = 125.5mph(from red line going from 14-15seconds)

123mph car is traveling 180ft/sec, at 125.5 mph car is going 184ft/sec. the distance traveled is average of those two numbers. or (.5) 182ft/sec = 91 ft.

now lets look at the car when it shifts. it looses speed.
123mph travels 180ft/sec. at 122.5mph car goes 179.7ft/sec.
average speed for that same .5 seconds is (.5) 179.85ft/sec = 89.925 ft.

so if we had two identical cars. both door to door at 123mph and one car has to shift to fifth and the other does not. the car that has to shift will loose 1.75ft of distance during his shift. so he has to travel that additional 1.75 ft to catch up.

so how long does it take to go 1.75ft at 179.666ft/sec (122.5mph) ???

.0097 seconds

 

I don't think anyone here would argue that in some cars/conditions, shifting to 5th will make for better ET's and better MPH... that's obvious, but are you trying to claim that's always the case?

 

actually you are wrong. if I asked a random 100 people on this forum how much time their ET suffers having to shift to 5th 90 of those 100 would say they loose 1 to 2 tenths. the other 10 would say they loose even more than that. the math says you loose .0097. thats not very close to 1/10 of a second. its closer to 1/100 of a second.

and the really sad part is this mis belief that a shift to 5th hurts your ET has 100s of people converting their evo9 trans to evo8 3rd and 4th gears. now their car accelerates slower in 3rd and 4th. just like driving uphill. so their new ET is slower not faster. the evo 9 trans has better gear ratios for track times. even with the shift to fifth that will be needed in most setups.

 

So you think if we posted a pole asking:
“In some cars and conditions, does shifting to 5th give you a better ET's and better MPH?”
that all of the people would answer “No”?...

Certainly many would answer “Yes”, but it’s funny how insightful you think you are lol. So what exactly was I wrong about?


Anyway, here's an exaggerated example of what you seem to be missing:
Let's say two people are both driving a car with the power curve shown below. They both shift to 4th, and land around 7k rpms. Driver A has a longer fourth gear and doesn't need to use fifth. Although you are correct, Driver A doesn't accelerate as fast as B, B has to shift to 5th and lands at 4K where he's making A LOT less power.


You can't simply generalize whether shifting to 5th is better than a longer 4th

People have said this repeatedly in this thread and you just don't seem to get it.

 

Carloverx, sorry to be rude but you have no logic whatsoever...I am not missing anything. I have explained my theories quite well, then backed them up with data to prove it. you on the other hand come to the thread with statements like this:

car B has to shift to 5th and lands at 4K where he's making A LOT less power.

was this a real example or made up? cause I see it as idiotic statement... no one shifts to 5th and lands at 4000 rpm. especially with the power band given. that guy should shift at 10,000rpm. which will land him at ~8500rpm for 5th.

I will not reply to any more of your posts. maybe someone else can help you.

 

Lmao, it's an exaggerated example so you'd understand that your power curve plays a role in wether a longer 4th is a better setup. The fact that you still can't grasp the concept is honestly pretty pathetic, so I'll let you wallow in it and move on. Good luck champ

 

The argument of shifting to 5th isn't so much an issue of time to complete a shift, but ideal gear ratios for drag racing. The op's point of view is, you do not lose much time during shifting and using the shortest gearing possible to accelerate faster. This theory is correct to a point... The problem I have with this theory is, the extensively long 5th gear does not seem to be taken into account in the calculations at all. What doesn't make sense is, a strategy of using shorter gears only to force a shift into the longest gear possible on these cars, 5th. Even the EVO 9 5th gear is drastically longer then the EVO 8 4th gear. I'd be willing to bet, the average gearing in the 1/4 would be shorter with an EVO 8 4th gear then an EVO 9 4th gear and shifting to 5th. As I said, the theory is correct to a point, but unfortunately in the real world 1/4 mile, it just doesn't work out perfect as it does on paper like many other things that you would think should.

 

This pisses me off, had I known of this thread before I bought my 411 FD, it would have never been purchased nor installed.... This was an expensive learning lesson that could have been avoided....


This thing killed my cars acceleration, I ripped it out and sold it.