lsd

I want to get a rear differential with lsd in my 91 n/a, so I am going to go to a junkyard and hopefully find one out of a 86-88 GXL, 87-91 T2, 88 GTU, or a 89-90 GTUs, luckily J-Rat was nice enough to list those in previous threads, but I was wondering if I needed to know anything else about the process of switching my rear diff at all other than bolt off, bolt on?? before I buy it. I'm kinda learning about mechanic type stuff currently on my own and if I've learned anything so far, its ask first if you have a question at all.

I just read on another forum that the lowest octane gas is better for rotaries, I was curious, what is the best fuel?

You have fun finding a GTUs in a junkyard... ;)

I want to get a rear differential with lsd in my 91 n/a, so I am going to go to a junkyard and hopefully find one out of a 86-88 GXL, 87-91 T2, 88 GTU, or a 89-90 GTUs, luckily J-Rat was nice enough to list those in previous threads, but I was wondering if I needed to know anything else about the process of switching my rear diff at all other than bolt off, bolt on?? before I buy it. I'm kinda learning about mechanic type stuff currently on my own and if I've learned anything so far, its ask first if you have a question at all.


If I remember correctly, the drive shaft (called the propeller shaft, in Mazda speak), will need to be modified. Should not be a big deal, nor should it be to expensive.


NOW, on to the octane... Here is a little something I posted on another forum a while back:


The fuel property the octane ratings measure is the ability of the unburnt end gases to spontaneously ignite under the specified test conditions. Within the chemical structure of the fuel is the ability to withstand
pre-flame conditions without decomposing into species that will autoignite before the flame-front arrives. Different reaction mechanisms, occurring at various stages of the pre-flame compression stroke, are responsible for the undesirable, easily-autoignitable, end gases.

and:

If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons ( reduce octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.

and:

Once the octane and run-on requirements of the engine are satisfied, increased octane will have
no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off, and is discussed
in more detail in Section 8.2. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane rating.

And:

If you use a fuel with an octane rating higher than what the engine can use, you are just wasting
money by paying for octane that you can not utilise. The additive packages are matched to the engines using the fuel, for example intake valve deposit
control additive concentrations may be increased in the premium octane grade. If your vehicle does not have a knock sensor, then using a fuel with an
octane rating significantly below the octane requirement of the engine means that the little men with hammers will gleefully pummel your engine to pieces.

Jarrett

so how do you know what the highest octane your engine can utilize?

In a non-turbo, you can burn pretty much anything. I'd use 89 octane because its cleaner and over time build less soot.

87 For N/As... 89 DOES NOT burn any cleaner. You use the LOWEST octane gas for your Car.

TIIs use the higher octane (91 recommended). This gives the boosted cars some detonation insurance.

87 For N/As... 89 DOES NOT burn any cleaner. You use the LOWEST octane gas for your Car.

TIIs use the higher octane (91 recommended). This gives the boosted cars some detonation insurance.


ok fine,.... whatever... (Good thing i can still get 94 octane in the shittiest state ever...)

I want to get a rear differential with lsd in my 91 n/a, so I am going to go to a junkyard and hopefully find one out of a 86-88 GXL, 87-91 T2, 88 GTU, or a 89-90 GTUs, luckily J-Rat was nice enough to list those in previous threads, but I was wondering if I needed to know anything else about the process of switching my rear diff at all other than bolt off, bolt on?? before I buy it. I'm kinda learning about mechanic type stuff currently on my own and if I've learned anything so far, its ask first if you have a question at all.


it really depends on what exactly you find in the junkyard, and how much it will cost..

For example.. if it is possible to buy a complete TII drivetrain... switch the whole thing from a new lighter flywheel back to the diff...

I bought a complete TII drivetrain from an 88 AE with 41K miles with no front for $200... a little on the cheap side.

IF you can dig up the GTUs, rear diff, that would be a rare find, and worth it.. I have an 89 GTUs in a barn i would like to restore someday..
(I have the TII and the RX-3 to contend with first)

I know of several LSD diffs out there to fit your application from 86-88 GXL's..

There is a complete parts car in a yard near me a friend of mine is buying for the "dog-house" to replace his... I am sure he'd give up the diff for cheap..

if you see any running 89-91 N/A engines (esp from an auto) please let me know!

Ok great, do you know exactly what kind of modification to the driveshaft I will need to make?
I really appreciate all of the info.

Oh yeah, and can someone tell me how I can get an avatar?

so what about once some mods have been done on a N/A, would it still use the same octane? and say you get a N/A at around 200hp would it make any difference the octane you use?

by the way, my state is the worst, we do have 92 octane like a mile from my house though so thats nice(or was untill I now found out that it isn't helping :disappoin )

so what about once some mods have been done on a N/A, would it still use the same octane? and say you get a N/A at around 200hp would it make any difference the octane you use?

by the way, my state is the worst, we do have 92 octane like a mile from my house though so thats nice(or was untill I now found out that it isn't helping :disappoin )


At a certain point, higher octane will be required. But unless you are ported, there arent any bolt ons (aside from Nitrous) that would require the use of anything higher then 87. We run 87 on a streetported S5 motor with full intake and exhaust with no problems.

Jarrett

Ok I've found a few T2's in some Junkyards nearby, if i get the entire drivetrain will it all just bolt right on, or will anything not fit, and while I'm getting parts, is there anything else I should snag? Just about all of the Rx7s I could find had significant damage to the front end.

Oh yeah, and is there any difference in the rear diffs of a T2 and GTUs??