I was just curious as to why the wrx has a 2 liter engine when the 2.5 rs has a 2.5 liter. Since they already make the 2.5 why not use it to get some more power/torque ????

Don't qoute me on this but I believ that the fia only allow's a maximum of 2 litre's for the rally car's

Right, homologation rules.
--Adam

I don't think there are homologation rules anymore.

Probably its a 2.0 to reduce the number of parts they have to manufacture and keep in inventory since the rest of the world has a 2.0 turbo because in many overseas markets, especially Japan, there are major taxes on engines greater than 2 liters in diplacement.

They already have 2.0 turbos, but not 2.5 turbos. An easy do.

My guess is that our engines(the RS model) were once 2.0 liter engines bored to 2.5 liters. Subaru engineers, figured that turbo charging a 2.5 liter engine would be a mistake. Thinner walls would mean a higher chance of failure?

I'm no engineer. Just guessing. I could be wrong.

Maybe b/c of compression ratio's?

I was just in a Subaru Dealer and I asked the same question. Basicly they said what Snoopy said. The Blocks of the 2.5 WERE 2.0 blocks. And the thought is that if they turbo the 2.5 it wont be as relable and they wont get as much from the turbo. The 2.0 is what 17lbs? And you know you can get more. If they try runing that in the 2.5 It may work, but at some point the motor is going to die (sooner then a 2.0) All the after market I have seen run 9lbs at the most. I am sure that some one can push 17, but it makes you wonder how long it would last.

My understanding is that some places in Europe (which had the WRX before us) has a tax, or higher tax, on cars over 2.0L. So it is common to turbo 2.0 or smaller engines to get the power out of them. Maybe some of our UK members would be more knowledgable on this....

I've also heard of the 2.0 limit on rally cars, but what do I know....

The 2.5l engines in 1998 were bored 2.2l engines. EJ22 existed for many years now. But starting 1999 and onwards, Subaru made EJ25 from scratch hence it's a SOHC phase II and not the 1998 DOHC phase I engines.

It's mostly due to insurance regulations in Japan & Europe. In countries such as Ireland and the UK you get charged based on the size of your engine. Anything larger than 2.2L in these countries costs an exuberant amount of money to insure. Just look @ the size of Japanese or European V6, V8 or V12 cars, they don't have much displacement because they would cost too much to insure. Just look @ a Ferrari. A 2001 360 Modena has a 3.6L V8! Thats 1L less than a Ford Mustang!

I guess that's why import sports cars tend to use turbos, superchargers, advanced engine management, and tend to be more aerodynamic. Americans just throw a big block V8 with 500 something cubic inches in a car that resembles a rounded off brick and call it a day. (i.e. Dodge Viper & its 8.0L V10).

My source of information comes from some Irish exhange students. I got into this conversation with them last summer when they started asking me questions about my 96 Z28. They asked how many liters the engine was and almost passed out when I told them that it was a 5.7L. I guess in Ireland you have be over a certain age (24 I believe) to buy a car with a 2.5L or higher.

The car was designed to optimize the FIA rules for rally cars, which called for a 2.0 litre turbocharged engine. Whether those rules have changed since then I'm not sure...

-tim

There still ARE homologation rules, although I don't know all of them. That explains why Lancers, Focuses (Foci?), 206's, Corolla's etc., all use 2.0L turbo motors in the WRC.

I believe another stipulation is that 25,000 examples of the car must be built before it can enter the WRC. That prevents special, one-off cars (such as the Group B monsters) from being entered.

JD

All the rules are on the FIA web site. Group N (where Subaru competes with WRX STis) limits displacement to 2.0L.

That said, Subaru should absolutely build a larger displacement turbo for the U.S. Look at the success Saab and Volvo have had with torquey, larger displacement, low-boost turbo motors. I'll take 2.5L and 5psi over 2.0L and 14psi any day.

Overseas manufacturers typically choose a larger displacement NA motor for US use because of the torque curve, etc.

That is why we have a 2.5 to begin with.

They use smaller motors that rev higher in Europe and Japan for fuel and tax reasons.

Like I said, its a parts bin issue. Look at the turbos we get from VW - the 1.8T. Why not the 2.0? Because the 1.8 is turbo'd in Europe.

Volvo's turbos are mainly the 1.9T. Also available in Europe.

I don't think many overseas manufacturers are going to do a larger displacement turbo car just for the US. The market for such things is too small to redo the engineering.

WRC cars have no homologation requirement, and Group N allows up to 2.5l for a turbocharged engine.

If they make a turbo 2.5 for the Forester though, it could be happily transplanted in the North American WRX.

I don't think 2.0L is going to cut it for too long. Honda/Acura and Nissan are turning up the heat, and obviously large-displacement domestics aren't the slightest bit afraid of a (stock) WRX.

That's a big if.

Overseas turbo Foresters are 2.0's.

Right, but it's expected to grow a bit in the next generation and it will need something stouter than the low-pressure 2.0L turbo to keep pace with the class. A low-pressure 2.5L would work, as would the 3.0L H6.

The same (basic) 2.0 litre engine that's in the WRX powers the WRX car, which (I think) was making 400 hp when they brought it to the US for Subaru Team USA. This should show you that, with the proper tuning, Subaru's 2.0 liter is capable of an awful lot of power without an awful lot of displacement.

To give another example, look at Toyota. Most of the racing Supras in Japan didn't use the stock V6 twin-turbo engine. What did they use? A 2.0 liter engine from a turbo MR2, the same thing that powered the rally Celicas. Those things could be cranked up to 600+ hp if you knew what you were doing...

-tim

How many bone stock, U.S. emissions legal, 50,000 mile warrentied, mass produced cars make more than 1 bar of boost? OK, the Saab Viggen, but not many others. Why bother, when it's much easier and cheaper to bump the bore and stroke a bit and get better driveability as a bonus?

not quite that easy Tim.

of course racing 2.0L turbos can make tons of power-- they have extremely high maintenance and short service life. they also couldn't pass new car emissions, not to mention their price. oh, and turbo lag. it's one thing to be at WOT or full brakes 95% of the time, and an entirely different thing to drive the vehicle in frequent part-throttle, lower rpm situations.

I wasn't saying we'll be seeing a reliable and streetable 2.0 liter 400 hp monster of an engine coming stock with any Subaru (or Toyota, for that matter) anytime in soon, but it is possible, and with more turbo research, it will happen. I'd say within 5-10 years. I was just trying to demonstrate the potential of the engine.

Besides, if you take the 2.5 and beef it up enough to be reliably turbocharged, you'd probably add another couple hundred pounds of weight to the nose of an already obese car.

Bigger <> better (necessarily).

-tim

Subaru has been selling Legacy's with the 2.5 against the competition's V6's for a while, and it has worked. Mainly by selling them as Outbacks, where people expect slightly less performance from a Sport Utility - in this case, a wagon.

If Subaru needs to get serious as a sports car seller in the US, they just turn up the boil on the WRX, probably easiest by sending the STi.

If they are making the next Forester bigger, it will have to take the H6, which is going to have to breathe better or something to get into the 225+ hp range. And they'll have to reduce the price.

Either way, we aren't going to see anything that gives 2.5RS owners a quick, factory path to anything more exciting.

Blaster, good points. Still don't think the current EJ25 is going to match up well in the near future though. Perhaps variable valve timing will give it a nudge in the right direction.

Tim, the 2.5L doesn't weigh any appreciable amount more than the 2.0L in your WRX. Sorry to disappoint.

Well, it seems the concensus is that the 2.5 block is based on a 2.2 or 2.0 bored out to 2.5. If that's the case, Subaru probably wouldn't be happy slapping a turbo on there and giving it a 50,000 mile warranty against blowing a head gasket. They'd likely engineer a stronger 2.5 engine with thicker walls to handle the boost.

What's the current weight on a 2.5 rs, anyhow?

-tim

Tim, they are all open deck (so the bores are fairly free-standing) and the cylinder wall thickness is comparable no matter the displacement. There would be no more risk blowing a head gasket than a current WRX would have.

The only real problem is cost to market. The other 'problems' you've raised simply don't exist, and bigger is better when the block stays the same size.

Then why aren't the turbo'd 2.5 rs's running 14+ psi of boost?

(oh, and the curb weight of the new 2.5rs w/ manual tranny is around 2950 lbs, in case anyone's following along at home)

The reason the 2.5l turbos aren't running 14+ psi is because they're all higher-compression motors than the 2.0l in the WRX. If you put the 2.5l at 8.5:1 compression ratio (I think that's the WRX's CR, correct me if I'm wrong) then you could easily push 14+ psi.

Ahh ok... I thought it was a integrity issue. What's the compression ratio on the WRX EJ20?

-tim

why does the '02 2.5 weigh 130 lbs less than the WRX?

I'm guessing the majority of that comes from the turbo piping and whatnot... plus those fog lights must weigh a good 20 lbs :)

-tim

Subaru obviously believes in the 2.5 for the US market (I think Legacy's can be had with the 2.5 in Australia, now, too). They just opened a new plant in the last year strictly for that motor. With flexible manufacturing, etc., I am sure it can be retooled, but not for free.

The 2.5 is the base motor for US cars now - the 2.2 is no longer available in Imprezas or Foresters. It will continue to keep Outbacks and soon the STX in the sub-30k range.

Adding FI to the 2.5 will require new pistons, probably crank, maybe heads. Call it everything but the block on the engine. Plus ECU tuning. Plus certifying with the EPA. That's a lot of engineering.

Especially when they already have a "performance" motor.

I think they will massage the H6 and make it cheaper (think DOHC - > SOHC with the 2.5).

Why does US Impreza have 2.5???
This is the right question to ask. Nobody else (except CAN) in the world gets Impreza with 2.5.
Subaru put 2.5 because American loves bigger motor.
Why Silvia has 2.4 in US? Same reason, I bet.

List of engine Subaru has (except 660cc ones)
EJ15
EJ16?
EJ18
EJ20 NA
EJ20 turbo
EJ20 twin turbo (won't fit to LHD)
EJ22
EJ25
EZ30 (6cyl Outback motor).

Yes, Subaru only has EJ20 for turbo engine. I guess that the biggest reason WRX has 2.0. Why they don't develop EJ25 turbo?
I don't think it worth to do that for Subaru just for US market.