My current setup consists of the 1820 turbo with associated mods, ecutek, and a DR500 FMIC. This is all on the stock block and stock 5 speed transmission.

The car was tuned to 320whp a few months back. It performs pretty well on the highway compared to other stock cars out there, but as we all know, after a while, one starts looking for even more out of the car.

My question is with regard to my next mod. I was thinking of either going with a six speed trans (with associated spindles, diffs, etc etc), or going with an even bigger turbo (GT30r). I don't run race gas or anything like that, and don't plan on running anything over 19-20 psi with such a setup. I just like the fact that one can get some really nice power levels out of the turbo without needing to run really high boost pressures.

My dilemma is that of whether I would get more of an improvement in highway performance (say from 40mph - lets say 120mph) by going with an JDM STi-RA 6 speed gearbox as opposed to keeping my 5 speed and just slapping on a GT30 kit and getting that tuned for more power (which can be done hwile running less boost than my current turbo).

From my research on the Subaru 6 speeds, they appear to be geared very low and close, which means that a lot of shifting would be required. What I am not sure though is if my car will be outright faster from a roll with 320whp and a six speed as opposed to maybe 340-360whp (this is what I am aiming for out of the GT30r) and the 5 speed.

Your opinions would be greatly appeciated guys...

Thanks in advance.

Someone correct if I am wrong, but I don't think the GT30R is in it's efficiency range at 19-20psi. It wants a lot more than that. Don't know if you will achieve the power you want.

If that is true, then you definitely want the shorter gears. I have heard the shorter RA gearset takes a tenth or two off in the 1/4 by itself.

I would personally put money into a full sti drivetrain and motor. Read my thread here:

http://forums.nasioc.com/forums/showthread.php?t=670037

It's not as expensive as you think, and it will make a much better foundation from which to build from.

More HWP pulling power= BIGGER TURBO, and good gearing, but bigger turbo first!

Someone correct if I am wrong, but I don't think the GT30R is in it's efficiency range at 19-20psi. It wants a lot more than that. Don't know if you will achieve the power you want.

If that is true, then you definitely want the shorter gears. I have heard the shorter RA gearset takes a tenth or two off in the 1/4 by itself.

Gruppe S has a GT30r kit on the way which drops over 300whp with 17psi and 91 octane... Ultimate Racing's stage 5 package also produces 114mph trap speeds running 18 psi of boost on the stock block and tranny.

More HWP pulling power= BIGGER TURBO, and good gearing, but bigger turbo first!

This was my thinking as well too... Even with my current turbo, the car pulls quite nicely on the highway in 4th gear... But I would like even more pull in that speed range.... What I was unsure of is if it is more a gearing issue than power? or if it is more a power issue than gearing...

I am *trying* to cap off my mods to the car to enjoy it, so I was thinkin to go out with one last mod! :rolleyes:

4th gear is godawful when approaching 120, my vote still goes to better gearing.

When I lost my 5MT I swapped to a JDM STi engine/6MT. Matter of fact I got lucky cause my swap ended up being a Spec-C :banana: We had thought is was just a JDM STi but, I can say this. I love the JDM 6 speed, I just had to swap it out for a USDM 6 and the 5th & 6th are to hi for the 2.0.

So if you can pick up a RA 6 speed go for it. It keeps you in the sweer spot much more even if you still have to shift a lil more. On the turbo I have a Green but, am already looking to swap up to a GT30 :devil:

you could try the ra 5 spd gearset. alot cheaper and can def hold the power.

i say you go with ver 7/ver8 motor and slap a green on.

i do a lot of 40 to 120 in my wrx

but i run 26 psi on a fp green and a jdm tmic and c116


you got a good turbo jest turn it up to 22 or 24 i wood

I second the JDM 6 speed swap. The gears really do make a huge difference. I no longet have to downshift when passing in 6th gear. It does 80mph at 3750rpms, plus the tranny feels great when shifting. And eventually youre gonna need one, so why not get one now.

2.5l= torque = power

The RA 5 speed ratios are much too short for highway driving. Get the six speed... and while your at it, a deadbolt superzilla. ;)

4th gear is godawful when approaching 120, my vote still goes to better gearing.


hmmm yes, I founbd especially with the stock turbo that this gear was too long. with my 1820, it is actually a gear I can work with, but I still get pulled by 380whp turbo civics in that gear though.

Yes I know that there is a massive whp and gearing disparity there.. Just again trying to figure out what it is more of ya know...

Does anyone have any experience with the 6 speed type RA gearbox?

I fell kind torn because I like how the engine feels relatively relaxed in 4th and 5th gear at 'brisk' speeds, but I still want a lot more pull in that 4th gear.

I would have gone the route of the 5 sp RA gearset, but it appears that nobody ever has them

Does anyone have any experience with the 6 speed type RA gearbox?

I fell kind torn because I like how the engine feels relatively relaxed in 4th and 5th gear at 'brisk' speeds, but I still want a lot more pull in that 4th gear.

I would have gone the route of the 5 sp RA gearset, but it appears that nobody ever has them
I have experience with both the 6 speed RA and the USDM 6 with the same engine tune. I was thinking the USDM was gonna be better cause of the higher 5th and 6th but I was wrong :(

With the 2.0 it almost bogs a bit in 5th and I have to downshift to 4th to get the car back into boost. The USDM and the JDM 6's have the same 1st-4th gear ratios then the USDM 5th and 6th are higher. Rallispec had all the ratios listed but, I can't find them right now.

My recommendation would be a RA 6 speed! With this you are looking at a trans that always seems to be in the right gear ;)

I have an RA 5-speed, and as I said, it is too short for the highway. If you have a huge turbo you wont want to be limited by gearing, you want to be limited by fear. Get the six speed.

I was in your shoes earlier this year, but was looking to upgrade from a VF24. I got a VF30, and now I need more! I'm thinking 18G or 20g and different gears.

The WRX gear are too tall ! One can try to overcome the gear issue by stuffing in more and more boost. Unless you want to have top speed bragging right, lower gearing is the way to go with less stress to the engine vs running higher boost.

I would personally put money into a full sti drivetrain and motor.


I'd just put my money into an STI period.
If you like the WRX and want more power, start with the STI and go from there.
Or for about the same price find a nice 2002 Corvette Z06 that was owned by an older man who didn't race it.
For about $35K you'll have all the highway passing power you'll need.

I'd just put my money into an STI period.
If you like the WRX and want more power, start with the STI and go from there.
Or for about the same price find a nice 2002 Corvette Z06 that was owned by an older man who didn't race it.
For about $35K you'll have all the highway passing power you'll need.

I think those are both good ideas but if keeping your car definately get a 6 speed whether USDM or JDM you'll be happy and so will your motor.I have a US STi so i like the taller gearing myself for 5th and 6th the 2.5l spins them fine and i'll want the gear when the bigger turbo goes on.6th in the STi at 7000rpm is like 182.5mph. I'd like to add a little rpm and a taller final drive i think that will make it faster in the 1/4 with high hp and obviously make 200mph top speeds possible.

does anyone know with the ra 5 speed gearset what kind of rpms its will turn in 5th at 80 mph. plus how much would that gearset cost me?

does anyone know with the ra 5 speed gearset what kind of rpms its will turn in 5th at 80 mph. plus how much would that gearset cost me?
Rallispec (http://www.rallispec.com)
Look at the gear ratios on the Rallispec web page. All the RPM/MPH are listed to give you an idea so you don't have to do the math ;)

Jigga,

I wouldn't recommend going with a GT30 if you are only running 19-20 psi. I have one and I know that running that amount of boost isn't even putting it into its efficiency range yet. Don't get me wrong, I love the turbo to death. But running that much boost will only yield a small gain in power going with a GT30. I would definitely go with a new trans, that will help make your car more of a highway monster. I think that a RA 5 speed or Possum Bourne 5 speed would be one hell of a set up with your current mods. My friend down the street has the Possum Bourne and it is the nicest 5 speed I have ever seen.

Here is the LINK (http://www.possumbourne.co.nz/index.html)

Craig

I'd just put my money into an STI period.
If you like the WRX and want more power, start with the STI and go from there.
Or for about the same price find a nice 2002 Corvette Z06 that was owned by an older man who didn't race it.
For about $35K you'll have all the highway passing power you'll need.
I disagree. The JDM sti 2.0 liter motor is much strong that the 2.5 liter USDM counterpart. Since he wants a big honking turbo the stronger block is the better option. USDM sti owners have to worry about what size turbo they put on, I don't.

Jigga,

I wouldn't recommend going with a GT30 if you are only running 19-20 psi. I have one and I know that running that amount of boost isn't even putting it into its efficiency range yet. Don't get me wrong, I love the turbo to death. But running that much boost will only yield a small gain in power going with a GT30. I would definitely go with a new trans, that will help make your car more of a highway monster. I think that a RA 5 speed or Possum Bourne 5 speed would be one hell of a set up with your current mods. My friend down the street has the Possum Bourne and it is the nicest 5 speed I have ever seen.

Here is the LINK (http://www.possumbourne.co.nz/index.html)

Craig

Hmmm Thanks for the advice... I think the real reason why I wanted the GT30 kit was partly because of the trap speed figures that Ultimate Racing get with theirs on pump gas (94octane - which is available at the pumps around here). I also looked at Gruppe S' kit which was good for just over 300whp while running 91 octane gas and a relatively tame amount of boost, so I was thinking that on 94 octane and a little more boost, it would jump to way more than the 320whp that i am currenty playing with.

I am aware that the stock blocks are not really built to take the massive boost numbers (20 psi +) that quite a few people are running, and I am not sure that I feel comfortable running that much boost either...

As mentioned before, my car drops 320whp, but that is at 19 psi on my 1820 turbo on 94 octane. I was thinking that a GT30 would make even more power than this on 94 octane gas, while running less boost as well too...

That turbo Civic that I was referring to earlier that made 388 whp was running some T3/T4 turbo at only 15 psi of boost, which was quite eye-opening... I would think that such a turbo would not be running in its efficiency zone yet either..

When I called the guys at Ultimate Racing, they mentioned that their kit runs a max of 18psi on the stock block, and that is was good for the 114-115 trap speeds that we see on their website, on the stock gearbox...( I would guestimate that the stage 5 package makes around 360-380whp on 94 octane gas.

Now, they were not privy as to exactly how much power the kit was making at the wheels(since they road tune their cars), but I can bet that it is MUCH more than 320whp is needed to push a wrx to a 114mph trap speed.

Now I have done some searching, and I can't quite figure out where my car should in theory be stacking up in the trap speed department... I don't track the car either, since i feel i have too much mechanical sympathy.. :o

I can tell you this, Junior tuned my car. It's a Spec-C so yes I have a rock solid foundation to abuse. I went with a FP Green, QuickTime Header DP/QTEC and pulled 380WHP on 93 and 405 on C16.

So then he went and pulled almost the same amount of HP from a USDM 2.0. However the power curve was small as he was afraid of detonating the cast pistons and the rod strength :confused:

My engine pulls almost 405 flat from 4k to 8500 rpm with 385 ft lbs peak on C16. Next we are looking at going GT30 and trying for 500whp. Before I do that I need to get a clutch that will hold and put the JDM 6 speed back in. I am staying away from the USDM engines and the cast pistons there are limited with. Plus the 2.0 will let you wind it up higher and stay in gear longer as I am going through the traps in 4th with my 6MT ;)