R34 Gtt With Serious Power?

[SKY 34]

The most you can get with any RB25 engine NEO or not is 400rwhp...which works out to be slightly under 300rwkw...with bolt on modification..

also note that this power is only for dyno...can't run at this condition for road use, prolly blow your engine to chunks...~~

gotta spend abt $20,000...

GTT now cost abt $30 000 + $20 000 = $50 000

GTR abt $90 000 mark

same thing you gotta spend quite a bit on mods to get up to your 500kw mark...

[Abo Bob]

I've estimated that just to get the gearbox prepared to handle 300rwkw, that alone will be around 10k

<{POST_SNAPBACK}>

My transmission is built to handle AT LEAST 300rwkw (that's long term tested on other cars) and cost $3300 from MV Automatics.

[satanic]

What was done to the gearbox Adam?

The estimate that I posted was based on a conversation with one of the mechanics; mentioned stuff like replacing most of the gearbox components with much stronger stuff. At the end of the day, he said the gearbox has very much not been "re-built" but "replaced"

You reckon he was pulling my leg?

[Sydneykid]

I don't want to turn this into an auto discussion, this threrad is not about gearboxes. This is a post I made in the Stagea Autogearbox thread, pop over and have a read there;

I am far from an auto box expert, I leave that to the profesionals. The following assumes some level of knowledge of how an automativc geabox works. If you don't know, then this is the best thread I have seen for a while, please read it first;

http://www.ukcar.com/features/tech/gearbox/AUTO/

The auto in a Stagea is made by Jatco, and is basically the same as Z32 and R33GTST (+ a 4wd transfer case bolted on the side) and several other larger 6 cylinder Nissans, 4wd's, utes, trucks etc. So parts and knowledge are not hard to find.

If you need higher rpm for launch (so you have boost) then a high stall speed torque converter is the answer. You pick the stall rpm to suite the boost build characteristics of the turbo. The standard torque converter has around a 2,000 rpm stall speed, but as you increase the torque output from the engine the stall speed climbs a bit. At around 150 rwkw mine was at 2,250 rpm. Since you have the engine producing kinetic energy and the car going nowhere this energy has to be converted (Newtons Law, see, high school physics is sometimes usefull), in this case into heat. Think 60 or 70 of those 1 kw bar heaters, that's a lot of heat. That heat goes into the transmission fluid, hence the need for a big tranmission cooler.

An example, if you have turbo that produce boost at 3,500 rpm then you get a 3,500 rpm stall conveter. Bingo, boost at launch. The problem is (you get nothing for nothing) it is always a 3,500 rpm stall torque converter, so the car won't move until the engine is doing pretty much 3,500 rpm. That's bad for economy, emmisions etc

The Stagea auto uses a band for 2nd gear engagement, this can be upgraded with a stronger band (sometimes kevlar) which gives higher grip (to handle the extra torque) and tolerates more slip and heat.

The 3rd and 4th gears are engaged by clutches (wet clutches, like the ATTESSA), these can also be upgraded to handle the extra torque.

The bands and clutches are controlled by valves switching hydraulic pressure, so a "valve body" upgrade can be used to speed up the band/clutch engagement (sometimes called a "quick shift kit"). This lessens the wear on the bands/clutches and makes the gear change quicker/sharper. As usual you get nothing for nothing, this means slightly harsher gearchanges, not as seamless, less smoooooth. Good oil temperature control is necessary for tight gearchanges, hence the need for a big transmission cooler.

How much does it cost? Well the full upgrade (torque converter, bands, clutches and valve body) seems to be around $3,500 (excluding gearbox R&R). The first step is a big tranmission cooler (~$200), then a valve body upgrade (~$300), then its inside the gearbox time.

How much power will it handle? Damn tuff to answer as the weight of the car and its traction (Stagea = 4wd and 1700 kgs) has some bearing. It will most certainly handle as much as the standard engine internals are capable of supporting (ie; ~300 rwkw).

That's about the limit of my research so far, hope it was of some help. MV Automatics in Adelaide seem to be the Skyline auto experts. There was a valve body exchange arranged on the Group Buy section a while ago with them.

cheers

Edited January 31, 2006 by Sydneykid

[Abo Bob]

Yup. The planatary gearset and the valvebody are the major parts and they remain. The VB gets modified with valving and machining. The gearset remains unchanged. It's extremely tough from the start. What is weaker are the clutches and bands which get replaced with kevlar parts and the servos which get replaced with larger heavier duty items.

MV Automatics is the only place I would send an R34 box to in Australia. I have spoken with most of the big name auto modification places and they don't know this box at all.

[chops]

An example, if you have turbo that produce boost at 3,500 rpm then you get a 3,500 rpm stall conveter. Bingo, boost at launch. The problem is (you get nothing for nothing) it is always a 3,500 rpm stall torque converter, so the car won't move until the engine is doing pretty much 3,500 rpm.

<{POST_SNAPBACK}>

Great post SK, but the bit I've quoted is not entirely true.

A well built modern day converter should still retain sufficient efficiency to drive nicely on the street.

Although it's not a Skyline, I have a 3000rpm converter in my car, and it is efficient enough that it will still creep at idle if you do not have your foot on the brake. When you accelerate lightly, it "flashes" to a higher rpm than it would with a standard converter, but not to full stall speed. Stomp it and of course it will flash all the way.

I love my converter, but my advice to ANYONE considering this modification is to drive a car equipped with one before deciding - they are definitely not for everyone, as they change the characteristics of the car greatly.

As for the recommendations for MV Automatics, I live in SA and know a number of people who have had trans work done by them in a range of cars. I'm yet to hear a bad story.