This is a question that has been brought up once before by yours truely, since then I have thought of many questions different from the first spectrum of the older thread!

First off with this setup... What LSD if any are you guys running!

What Trap Speeds are you getting in the 1/4 mi.

How is the drivability of the car!

With the new price drop of the APS ST and the delay of the rev-up ST I am looking into both options... as I am ready for boost NOW, I am having withdraw since the sale of my turbo MR2.

My main concern is loss of the daily driven ability of my beautiful Z!!!

Thanks,
Don

 

I seem to remember REDHOTZ having the 3.9 gears with a Turbonetics setup.

 

I spoke to the guy that is running the shorter FD w/TN ST.
The first gear is unusable either way. Otherwise he was raving about it.

I swapped a 6MT pumpkin into my car (I have a 5AT). Since there were no blown motors in the last few days I am once again growing receptive to boosting on stock internals (at least until another one blows) and I am very confident about running either APS ST or a TN ST on shorter gears.
FWIW, when I drive 65-70mph in 4th my tach is right on 3500-3600 and as soon as I touch the throttle tharrow just flies to 4K. I think that this is a good mod for an ST user.
The whole gearing deal, it is a bit amusing. Everyone gets a ton of power, but then needs taller gears, but then needs more power. Come on, what do you wnat to do, hit 80mph in 1st? Shorter gearing means greater acceleration with same hp.

 

That leaves out the most important element of the equation - traction. Your car will actually be slower with the shorter gears due to lack thereof. That, and you will have to shift sooner, which means less time actually accelerating. With a higher power FI car I think it's actually a performance downgrade... but that's arguable.

Oh, and I'm talking 6mt here. I have no clear idea of how it would effect 5AT performance.

 

It is a downgrade if your prime objective is to make an X amount of hp (then you wonder how the hell to keep the car driveable). That is why I would rather do everything else firts, squeeze the last drop of power from the stock powertrain, and then see how much power I would need to add.

That's true. But the 5AT car benefited greatly from this mod.

 

I understand the idea of traction!

But my ideal ride is a highway car with about 400whp and call me Happy!

My favorite thing is the ability to stay closer to that boost and then able to still shift safely at 7000 rpm! My rev-up motor is such a different beast from all my buddies Zs w/ 287. The Idea is moving my usable rev-range where I sit at during cruise and race per gear is closer to my peak power!

But I am patiently waiting to see the new rev-up TN kit, where as the APS is sitting at an applicable kit already! minus some re-tuning!

:edit: I wanted to add a few more notions!

theoretically the shorter the gear the less power you need to achieve the same trap speed! Correct me if i am wrong! With a goal max trap of 120 I am sure that a race gas map and some sticky wide tires and 420ish rwhp will yield such a speed.

 

Look at many High HP Supras their 1st gear is pretty much useless unless the boost is set lower for that gear! But even then there isnt enough time for 1st to even spool some of those huge turbos!

I never use first gear and drag racing isnt my thing! Ill leave that up to Alberto but me being able to hang with/ and or beat my friends C6 and all the Cobras around the Cincy area will be thrilling enough for me! Not to mention I have a complex building by this constant beating I take from all the quick SRT4s... Damn them its cost them less than $1,000 to run 12s. And they can carry 3 people to laugh and point at me!

 

Pushing the 60-1 turbo that comes with this kit isn't a problem. You reach full boost faster than most single turbo supras even begin to see it. It's hard to really compare, as it's a whole different beast. Besides, many high hp supra owners are not interested in running from a dig, and therefore change out the fd to a 2.9 or 3.1.

Once you're in boost you don't want to have to shift and lose it, which is what you're achieving with shorter gears. With longer gears you'll be staying in boost longer and likely will be able to finish the 1/4mi in 4th gear as opposed to 5th.

So, to me there really is no upside to going with a 3.9fd on a turbocharged 6mt z. If anyone tends to agree otherwise I'd love to hear your opinions.

 

the 3.9 worked out great with my vortech and with my setup have 100% traction, but the vortech is totally different from a ST.

I make about 355 tq at 4000
380 tq from 4600-6300
and 370 at around 6600

IMO withh a ST, the 3.9 FD would add some more fun factor to the car for 4th-6th gear and also when going WOT shifting at redline. But 1st and 2nd gear would become tricky

 

I don't suppose that in the Z's even with stock gearing the rev fall past the peak boost rpm when shifting, so comparesment with huge turbo Supras that hardly make any power below 5K is not the best example.
This would help going through higher gears a bit quicker and the lower gears will be hardly usable anyway.
From personal example, when going 65-70mph my revs are at 3500 and above, before it was about 3200. So with a singe turbo setup I will constantly be in boost. I don't suppose it would be much different for a 6MT car.

But it's all speculations. The only way to find out is to put 2 identically modded Z's with stock and shorter gearings next to each other, and do a real life test.

 

Turbo spool isn't based on RPM's, like a supercharger, it is based on engine load. Therefore if you're cruising on the highway at a steady 3500rpms, you won't be in boost.

 

Oh yeah, I keep forgetting, load...

 

I should have said *unlike* a supercharger, for better clarity, but you get the picture...

 

I still got the point...
BTW, from your post in another thread, the APS ST price drop is temporary?

 

Per Peter's post over at motoring:

It is temporary, but you've got a good 4 months.

 

oleg, you sure when you're in your 4th gear at 70mph that you're at 3500-3600 rpms?

depending on your tire diameter, with your 3.5 FD, you should be at 3100-3200 rpms @ 70mph

well according to http://www.f-body.org/gears/



anyway, it's a totally different ballgame with a 5AT vs 6MT. A 5AT with a 3.9 FD would still not quite be as short as a stock 6MT as far as how short the gears are only it wouldn't have a 6th gear

 

I've got to man up by December... Let's hope that no engines will pop before then.

 

I have a 5AT w/6MT pumpkin. My rear tyres are 275/40/18

 

in 4th gear at 70mph you should be close to 3100 rpms then

if you had a 3.9 FD, you'd be at about 3450 rpms @70mph in 4th gear

a stock 6MT Z would still have it's first gear be 7.1% shorter than your 5AT with the 6MT pumkin.

however because you have 1 less gear, when you shift at redline you'll be a few hundred rpms lower in the powerband which actually kinda takes advantage of the broader torque curve of a ST since the hp curve kinda plateaus off

 

I am going to take her out this Thurs.
I'll try it and post it.