koprutzxt

let me just start by saying that im likely gonna put my n/a tranny in anyways and then put a t5 if somethin happens. im just so damn curious like that ..

i would like an answer from any one who has driven or owns a turbo swap with n/a tranny ....
Q1) i wanna know if the gear ratio is good for the turbo engine?? did the turbo have good spool up time ?? how did it perform??


any knowledgable answer here
Q2) on my tranny i believe the 3 and 4th gear are longest on my 80' zx, is this good for an l28et??

Q3)does the t5 bolt up to the drive shaft on an n/a model
i am so ready for this swap i have spankin new l28et and turbo donor car all for the first z i ever bought.. can u say over-due overhaul

NismoPick

Spool time has very little to do with gear ratio. It has to do with the size / efficiency of the turbo, and the engine's exhaust. The only reason gear ratio is involved at all is because the engine / turbo needs a load to create boost (revving in neutral won't create boost).

Click (hopefully the site still works, "webring" is blocked on my work comp): Transmission Calculator - Z Design Studio

The T5 driveshaft does not bolt up to the n/a drive shaft diff coupler. You need the T5 driveshaft diff coupler.

koprutzxt

wow this site is pretty cool for comparing notes @ nismo
and the link even had it filled out info with wheel size 245 i just put these on lol
ok so here are the numbers i got from the link

n/a tranny- 3.o63 ___1.888______ 1.308______1.ooo_______.745
T5 tranny- 3.500____ 2.114 ______1.375______1.000_______.780

there is no difference when i input the r200 diff or r180
what do these numbers ?? ima take a guess cause i like to learn by being corrected

Q1) do the higher numbers mean there will be more effort from the motor to turn those gears, meaniing that there will be more load on the engine, there for more boost..??

Q2) is the roughly .5 difference in first and second that big of a factor or no biggie ??

NismoPick

The differential R180 / R200 doesn't matter, it's the gear ratio that matters.
Click: Gear ratio explained


Boost is controlled by the wastegate. I think you need to do more research on turbocharging:

koprutzxt

Ok mr nobody knows nothin complex get over it..
I understand how turbos work.. And the waste gate is just an actuator only realeases excess air to maintaine boost level not a deciding factor in how the turbo spools or boosts
Like u said earlier sthe turbo can only positivly boost under a load.
so then then my concern is will the short 1 and 2 gears give me time to spool or will I have to shift to fast to get any good pick up from stock turbo ??
I also wanna know what the tranny numbers above have to do with performance relitive to turbo swap..

rogerz

put a five speed in an 81T. After reflection I think the auto was better off the line but I like diddling a gear box. Kinda personal what you like. Slush boxes are junk when I was coming up (50years ago). but today I am thinking I'd like to put a modern auto in my z31 if I could find one that fit cheap.

NismoPick

I answered the questions you asked. Perhaps proof reading your posts will make sure you are clearly stating what you mean.

That Trans Calc has a graph on it, but it only shows in Internet Explorer, not FireFox (if you didn't see it).

Anyway... The stock T3 reaches full boost around 2600 rpm. The L28ET peak hp is around 5300 rpm. So in the stock n/a trans, you can get to 33mph in 1st, then 54mph in 2nd. Unless you have 500hp, first gear will be worth while no matter what trans you have.

When I did my L28ET swap, I kept my 81 n/a 5speed trans and 3.9 diff. It was fine until ~400mi later when the 2nd gear synchros died. I swapped in the T5 and my Z31T 3.7LSD and never looked back.

Lastly, unless you are at the track every night, or constantly street racing, the difference in gear ratios will be unnoticeable.

koprutzxt

Ok I'm sold I wish I had local car friends that would talk me into swaps all day lol my car friends are lazy these days no action..
So ima swap in the turbo engine. Take lots of pics and write up a nice how to.. So hopefully we can get a nice sticky.
I just need to find a beater I can cruise for about 2 weeks unless yall think I can weekend swap

FricFrac

The T5 comes with a different diff (3.54 or around there) than the NA tranny (3.9). They come out close to the same.

A turbo needs a load to make a lot of exhaust to spool the turbo. People confuse this idea with needing to restrict the exhaust somewhat to cause more load. Doesn't work that way - as unrestricted an exhaust as possible for a turbo car is what you want. Not really part of the topic but it's important not to misunderstand that concept.....