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Registered
2000 Forester STI
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89 Posts
Discussion Starter #1
Hello guys.

My actually SF STI ´00 AT forester is doing fine his job holding its structure integrity with my hard sand dune driving.



But now i will change the car because i need a turbo MT to have better torque at lower speeds. (want to put a SF dual range NA gearbox)

I can choose between JDM SG XT or JDM S/tb.

Need your advices about:

Which has better Chassis stiffness
Which has better Wheel clearance for bigger tyres
Are the SG 2002-2003 more complex in electronics???

So the basic platform will be a turbo forester (suppose to be 4.44 diffs)
The Dual range would be come from a NA SF (4.11 ????)

If so, i will need change the front dual range gearbox dif for a 4.44?? it will fit???)
What about axles, clutch end other details??

Thanks for the help



"this is me wondering when a Dual range gearbox will be in my fozzy"
 

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Registered
08 Forester N/A Manual
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263 Posts
I wouldnt bother to be honest - the Dual Range (at least the one in my Oz spec SH) isnt all that low -essentially it drops the ratios roughly one gear 2low is roughly equivalent to 1hi etc

also - i believe the dual range G'box isnt used on the turbo models as they will eventually break stuff with the extra power.

if i had the money, i would get a turbo engine, 6speed STI box (with DCCD) and have a set of different gears put in, 1st similar to 1lo on my SH and 2-6 equivalent to 1-5hi (probably a Dog Engagement with straight cut 1-4 and Helical 5-6 too - but thats a different story)
 

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Registered
1999 Forester S Turbo 5MT
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1,965 Posts
As said above, the dual range box can't handle the torque from the turbo engine. As far as chassis stiffness goes you might have to manually brace the underside of the car yourself and a rear strut tower bar of some sort too, might this compromise/strain the chassis though?. I've heard that the 6 speed DCCD has a lower overall final drive ratio than the OEM 5MT but you might need to check this out yourself and if this is the case, then it should suit you perfectly. They are a bit expensive though, even s/h and only the FSTI came out of the factory with this box. With the Forester you have one of the best permanent AWD systems on any car around and the only thing you don't have is the ability to lock the diffs. The stock Forester MT diff is 4.11:1 but the JDM car is different I think running the WRX 4.44:1 AFAIK. The overall setup and drive will be a good bit different with the MT though. Transmissions are not my strong point so maybe go into that section and ask the guys what is involved.

The JDM s/tb had more Horses out of the factory than the EDM/USDM models (2L models) so a good starting point. You could try tuning the engine for more power although the stock JDM TD04 turbo spools up at lower engine speeds (bigger turbos produce more power but spool up late and would require a remap) and can give maximum boost as low as 2500rpm with a few mods like a decat down pipe and maybe an outboard boost controller and 3 port BCS. This makes the car good for creeping but this turbo in stock form runs out of steam quickly after 5K which isn't so useful when blasting across loose sand which requires foot to the floor/maximum power/revs. However, a TD04-19T (stock blower has the smaller 13T compressor) can get around the loss of top end power, I've posted plenty on this turbo (look for my posts in the 2L turbocharged section if this sounds interesting). With the 19T compressor you keep the low spool up but it has a larger compressor which can produce more boost and hold on to the red line without loss of pressure. A rempa would be advised if you change the turbo even to a TD04-19T seeing as you are going to be flogging the car (in sand anyway) although we've seen at least one fella from the Uk with a 97 JDM s/tb 4EAT running higher boost via an outboard EBCS without any side effects and lots of power on the stock map (check out MYKPs older threads).

It all depends on whether you intend to buy a 2L or 2.5 as well, I assume the NA 2.5 engine won't have the power you need? It is worth noting that you will have a lot less power off boost then with an NA motor at the same engine speed/throttle load, is this an issue? I know there are a lot of guys in the US who off road fairly seriously in both formats (all 2.5 motors), maybe they can help. One last issue is your location. What is the elevation of your play ground? Turbo engines suffer more at higher altitudes than non turbo types, AFAIK, but this might not be so apparent with an AT.
 

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2004 X20
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19 Posts
One last issue is your location. What is the elevation of your play ground? Turbo engines suffer more at higher altitudes than non turbo types, AFAIK, but this might not be so apparent with an AT.
I don't know much, I am here to learn (in my case about the improvements of a hypothetical dual range swap), but, within my ignorance, I confidently intuit it is the opposite on this regard. Turbos and superchargers suffer LESS at high altitudes, as the inducted air pressure compensates for the lack of atmospheric air pressure. In my city, La Paz, situated at 4000 metres above sea level, most combustion engines lose a fair amount but turbos less so.

Cheers
 
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