So i have a question...
 

Its a techy question but not related to Subarus so I decided to put it in here.

One thing that always has seperated STis and Evos is how easily Evos can make massive power numbers. The thing I am wondering is why is that.

What makes them so easy to get ridiculous power out of? I mean the run smaller displacement, which allows there motors to spin up to a higher RPM but thats the only thing i can really think of. Anyone have any thoughts to answer my question?

Cast iron block that can take 30 psi. Not to mention it can spin to 7k or higher.

Cast-iron block, old-school motor.

4G63's hail from the glory days of inaccurate engine management, crappy gas, and less educated consumers. I'm not saying that as a bad thing. These are motors more akin to 1J/2JZ's, RB25/26's, hell, even the old EJ22T's (which were closed-deck and had forged internals, on a motor that only made 6 pounds of boost stock). They're built to take abuse, which means with proper management you can make serious power on stock bottom ends. Iron blocks that take heat without deforming and flexing, forged internals, etc. A motor that has to be able to handle bad gas and hamfisted driving and a management solution that has orders of magnitude less resolution than modern cars means they're overengineered in a big way. Same reason 1G DSM blocks are stronger then 2G blocks. Overbuilding costs money, adds weight, etc, so when you're able to engineer solutions to a more refined endpoint, you have tighter tolerances and don't overbuild.

The new Evo is a completely new motor, with an all-alloy block; and you're not seeing numbers like the old cars for a reason. Even with all the engineering int he new GTR, you're not seeing 1200hp street-drivable cars like you saw with R32-R34's with RB26's. There's a reason many JGTC Toyotas still run 3SGTE's (GT4/MR2 Turbo motor), same idea - old school iron block that can take abuse, and has a much higher performance envelope when you can take advantage of it.

Nope, not really. For one thing, the EJ205 spins to 7200 stock. The basic difference is manifold length, plus a less undersquare bore/stroke ratio. The Evo is no easier or harder to push to higher RPM- look at the v7 STi Spec C RA. 8200 stock warranteed redline.

The long intake runner length and the VERY long distance from the exhaust valves to the turbine is the main culprit. It's also why the Subarus tend to make better torque at low and midrange RPM.

The bore and stroke are also more conducive to right-shifting powerbands in the Evo. To be honest I grasp the differences well enough to agree with them, but not well enough to clearly explain. Rod/stroke ratios have a lot to do with how your VE works out at a given RPM, and how much force is acting on the pistons at a given engine speed.

Mitsubishi makes the stock Subaru turbo, which they intentionally sabotage to create lower output numbers for Subarus.

Or what the above guys said.

Thanks sybir. That explains a lot. And Nick stock revlimiter is at 7800 :) 8800 capable with new cams springs and tensioners.

Is the 257 not a closed deck? I know its aluminum so that limits it but even with forged internals it would seem that the aluminum block is the limiting factor then? does the horizontally opposed setup pose problems as well?

257's are semi-closed; they're braced a few points around the cylinder liner, but are still subject to more misalignment than a closed-deck that basically has a few holes for the waterjacket instead of a pool. Kevin's right, too, in that the ranges you see for high-power evos are all top-end - you don't see the same type of power delivery on a Subaru, for better or worse. High-powered Scoobies seem to make better DD's to me.

Ej257 is still semi-closed. There hasn't been a fully closed ej motor since the ej22 iirc. The newer semi-closed motors, though are nearly as strong (strong enough for production) and offer vastly better cooling. Better every day performance/value for the average consumer at the expense of insane (unusable) numbers for the 3 people would do it.

Or, "No Senator... our Germans are better than their Germans" -Right Stuff

This could just as easily go in the Pontiac thread...

err, what?

:?::?:

Another mistu related question. What exactly is crank walk, and why do the older 1g and 2g DSMs have problems with it but the new 4g63t in the Evo 8/9 not have it?

Sorry to semi change topics but it seems to better be put in a single mistubishi thred on a subaru forum than to upset the old farts *cough* Dean *cough* haha just kidding :)

Why U.S. automakers can't make a car anybody really wants to buy and other manufacturers can...

Stop derailing my thred???

You just ranted about it so why do it?

I remember reading something from AMS that says they think the new motor is better than the 4G63 and they see no problem making the power they used to...doesn't sound plausible to me what, what do I know...

Thanks Kevin, I guess I was just referring to the high revving motor as able to spin the massive turbo's that evo owners run. Which is sort of irrelevant because Subies run big turbos, but I just figure it a GT35R spools at 4k then it should hold that power all the way to the 8k rev limiter vs the STi's 6.5k. But the subies flow more air with a 2.5l so i guess its a trade off.

I think I am going to leave this thread before I prove my incompetence...

The only thing you're doing wrong is assuming the Evo is "high-revving" and the EJ is not. Physically, both motors have around the same rev limits for a given level of mechanical improvement, it's just that the Evo responds better as you slide your powerband to the right and go to larger turbos. A well thought out Evo motor that has a power band up near 8k RPM will generally speaking make more horsepower than a Subaru with the same basic powerband, but wouldn't necessarily be faster. You're on the right track about the displacement making up for a lower rev limit though. Airflow is airflow; think of the turbo as the sole determinant in how much air will flow through the engine. The larger the engine, the slower it needs to turn to generate that peak. So when you flow X air through an engine with 2.0 liters of displacement vs. one with 2.5L, you should make roughly the same peak torque. But since horsepower is a function of torque and engine speed, the smaller engine will make more horsepower because it's making that torque at higher revs. There's a TON of other stuff that goes in to tipping the power in favor of one engine or the other, but if all things were theoretically equal, Turbo X would make Y torque on any engine of any size, but horsepower would vary linearly with the change in size. More motor, less revs for a given turbo.

I'm meandering a bit but I think that covers the very basic idea of what we're talking about.

Crankwalk is the excessive thrust bearing play of the crankshaft. It's caused by the combination of improper bearing fitment, misalignment of the main caps under forced load, overturned mains on the crank, and overall sloppy assembly procedures. While factory and improperly built 7-bolt 95-99 2g engines are more likely to experience this problem than the '90-92.5 6-bolt and '93-94 7-bolt 1g engines, any engine can develop it. There are ways to remedy this manufacturing flaw in the 2g motors, but all will warrant a rebuild; Ie: Main cap dowels, correctly sized main bearings, stronger rods, proper assembly.

Crankwalk isn't unheard of to the Evolution crowd. I wouldn't be surprised if crankwalk becomes a larger issue when the majority of hard driven 8's and 9's start pushing into higher mileage ranges.

What irks me is the general belief that EVO "make more power" because they have a higher peak hp number. A 500whp EVO can be much slower than a 400whp STi because the EVO's power tends to be less usable out near red-line.

As was touched on earlier by sybir and Kevin, it's really about area under the curve. Just because a dyno-queen EVO can make a crap-load of peak power easier than an STi can, doesn't make it the faster car. And I'm not saying that the EVO can't be tuned for area under the curve. It's just that it's much easier to make peak power numbers on the EVO than it is on the STi, which is where this incorrect assumption that it's easier in general to make more power on the EVO motor. In reality, a 350whp STi should be about as fast as a 450whp EVO around a race track because they have similar area under their torque curves.

I am also learning from this thread. Scott, is this^^ also attributed to the displacement?or am I wrong to assume?