As posted here (http://forums.nasioc.com/forums/showthread.php?p=10754505&highlight=homologation#post10754505) Subaru will submit a homologation application for the new Impreza WRX STI spec C to rally as a Group N car.
STI's website has this news release (http://www.subaru-sti.co.jp/GRN/bulletins/050818.html) in regards to the homologation issue and changes in the new Impreza:

http://www.subaru-sti.co.jp/GRN/bulletins/050818_1.jpg


Main Equipment

1. 2006 model's progression:
Roof vane, large rear wing, and diffuser equipped: designed for improved high-speed stability.
New style DCCD: now with mechanical LSD which provides improved traction when accelerating through corners. Also, the standard 35:65 torque distribution has been modified to 41:59 in to provide optimized traction.

http://www.subaru-sti.co.jp/GRN/bulletins/050818_2.jpghttp://www.subaru-sti.co.jp/GRN/bulletins/050818_3.jpghttp://www.subaru-sti.co.jp/GRN/bulletins/050818_4.jpg

2. Improvement requirements met on 2005 model:
Lightweight body and addtional stiffener for increased frame rigidity
P.C.D 114.3
Higher caster in front suspension; Use of aluminum rear lateral links
Ball-bearing turbocharger
Large water tank (12L) for intercooler water spray
Air-cooled engine oil cooler


Spec Comparison:
(I listed only main differences)
...........................................2006 MY....................................2005 MY
Model...............................GDBF4FH-SLH...............................GDBE4FH-94H
Car length..............................4465mm........ .............................4415mm
Weight...................................1390kg... ...................................1370kg
Torque....................422N·m(43.0kg·m)/4400rpm..............412N·m(42.0kg·m)/4400rpm
Final gear ratio........3.900 (3.545 x transfer 1.1) *1........................3.900
Immobilizer................................Yes.... ........................................No
Power windows...........................All............. ...........................Front only

Rally Activity: In the case where an individual purchases this car, after license acquisition it is possible to participate in FIA Group N (as well as Group A ) regulated motorsport contests.


At the bottom of the page (http://www.subaru-sti.co.jp/GRN/bulletins/050818.html) there is a list of the 2006 Season Impreza Group N parts (intended for base cars).

Sweet.

So I guess the standard 2.5L STi's are not Group N homologated. :(


-Mark
MAPmotors.com

Rally I believe has required a 2.0L displacement, there are other differences besides that that are also different as well.

Rally I believe has required a 2.0L displacement, ...I doubt that Rally "requires" a 2.0L displacement.

FIA Group N specifies 2000cc. :confused:

FIA Group N specifies 2000cc. :confused:Show me the rule!

Yeah, thats why I asked. I always thought Gr. N homologation required a 2.0L motor

...:confused:


-Mark
MAPmotors.com

The FIA says that the WRC car can have a maximum displacement of 2L. For GrpA and GrpN the maximum supercharged displacement is 2.5L. However, the WRC car needs to use an engine based off a GrpA car, same with GrpN. To be homologated for GrpA/GrpN Subaru would just need to submit the info for the 2.5L car. It seems like that's all that would need to happen to be able to use the 2.5 engine.

There are weight restrictions based on adjusted displacement. 1.7*actual. At 2.5L it would stick the car into another weight bracket, it would probably have to weigh a few hundred pounds more.

I would think those cars would also come with various Group N bushings and mounts as standard.

Those alone make a drastic effect on handling.

Additional note here, as not only would there be the weight restrictions, but the turbochargers have a restrictor plate on them as well. It's not like you can run at any level of boost, etc, on those motors - you could make a *lot* of power if you were building a race 2.0.

So race teams in Group N would want a motor that is the best balanced for the amount of air allowed into the engine, and it's likely a 2000cc engine is the sweet spot for that setup. And then a 4-banger as it will produce more torque than a 6-banger of the same displacement. The air restriction would affect high-rpm power more than low-rpm torque.

That is a casual explanation of it, at least. :)

STi sells turbochargers for Group N that have the restrictor plate built in - I believe it is supposed to work a bit better than a turbocharger that has the plate added in afterwards.

Cheers,

Paul Hansen
www.avoturboworld.com | www.sevenphotos.com | www.scoobymag.com