Safe Rev Range

[deks69]

talking about my 98 legacy. Where is the peak HP on the 2.5's? I generally shift around 4000 grand, but it redlines at 6,500. And read somewhere the 165Hp is at 6400 RPM's, Is it safe to rev those babies up to about that? My 04 wrx (dealer said) reving that sucker way up is by design. Killed that car in a roll over. Due to the HG problem with the 98 I'd rather baby it, but it seems pretty doggy only reving it to 4 grand. Any thoughts? Many thanks to my stupid questions. HG problems or not, I still recommend subies over any car. And Im loven my 98 almost as much as my now gone WRX.

[Legacy777]

Redline is where it's at for a reason.....lugging the engines, and not revving them can sometimes be worse, because more sludge and junk tends to build up, and not be blown out by higher revs.

[86BRATMAN]

I'd recommend at least every once in a while "blowing" out the motor. You won't hurt the thing by getting up to red line. As 777 said its there for a reason.

[ericem]

I love redline, and have to do it quiete often to get it going past the ferrari beside me

[86BRATMAN]

I love redline, and have to do it quiete often to get it going past the ferrari beside me

 

Wow, there is a ferrari parked on your street...LOL

[WoodsWagon]

The rev limiter is at 6,750 rpms, or thereabout. As long as you're not bouncing it off the rev limiter, you're fine.

 

I think wear goes up as a square of speed, so having it wound out all the time will shorten it's life, but winding it out during acceleration is fine. Combustion pressures may actually be higher when you're lugging it at WOT at low RPM's, which is harder on the headgasket if anything.

If you like snapping the engine around it's rpm range, make sure the timing belt is within it's replacement schedule.

[Jimmyowensfan20]

Give it hell!

Blow it up!

Put in a 2.2L and give it hell and don't blow it up!

[ericem]

if you have a 2.5l not a good idea to love redline 2.2l can handle the abuse, and its non interference, and i can find a replacement engine fairly easy. 2.5l engine runs over $1000!

[nipper]

i redline Blu often. Its the only way to get on the highway. Its not so much redlining, but doing it with a full load that will hurt. the rev limiter kicks in before you hit valve float.

 

Here are the specs... 1998-1999

 

2.2L

 

Power: 102 kW , 137 HP @ 5,400 rpm; 145 ft lb , 197 Nm @ 4,000 rpm

 

2.5L

Power: 123 kW , 165 HP @ 5,600 rpm; 162 ft lb , 220 Nm @ 4,000 rpm

http://www.internetautoguide.com/car-specifications/99-int/1998/subaru/legacy/outback-wagon/1133/index.html

 

 

nipper

[Virrdog]

Combustion pressures may actually be higher when you're lugging it at WOT at low RPM's, which is harder on the headgasket if anything.

How is this possible? Combustion chamber pressure = horsepower. Nitrous, turbocharging, and supercharging all increase cylinder pressure... thus they increase the horsepower. That pressure pushes on the piston, which turns the crank, etc. etc. etc.

 

So I doubt lugging it will blow headgaskets because of cylinder pressure since that is no where near the peak horsepower of the engine. Now it might be something else, like higher heat, but I'm not seeing the increased pressure.

[jamal]

How is this possible? Combustion chamber pressure = horsepower. Nitrous, turbocharging, and supercharging all increase cylinder pressure... thus they increase the horsepower. That pressure pushes on the piston, which turns the crank, etc. etc. etc.

 

So I doubt lugging it will blow headgaskets because of cylinder pressure since that is no where near the peak horsepower of the engine. Now it might be something else, like higher heat, but I'm not seeing the increased pressure.

 

Actually combustion chamber pressure has a more direct correlation with torque and the load on the motor. So pressures might be the highest at peak torque, and they decrease above that. Horsepower is a function of torque and rpm, so even though a motor isn't producing the max torque above 4400 or whatever rpm, it's spinning faster and making more horsepower.

 

if you're lugging the motor detonation will occur which creates very high combustion chamber pressures.

[ericem]

So is it bad to rev my engine in my driveway sometimes? the H4 sounds great My dad said i will break a rod.

[jamal]

if the motor is cold, yes. Otherwise no.

[Scott in Bellingham]

[Andyjo]

The rev limiter on my OBXt is set to 7500

i'm not going to lie... it sees that on a regular basis.. and loves it!

but yeah, i think some people call that the 'mexican tuneup'

not to offend anyone or anything

[ericem]

if the motor is cold, yes. Otherwise no.

 

uh oh. A few times i might have reved it cold up to 2-2.5k rpms. But the only itme i felt like reviing it to 6,000rpm. was when it was warmed up.

[porcupine73]

Another reason for redline is engine balance. If you want much above that you need a blueprinted engine. Granted some other parts might be needed too.

 

Jamal has it right. Power is the cross product of torque and rotational speed.

 

What does the ECU do at redline, just not inject any fuel on some cylinder for one stroke?

[jamal]

The rev limiter on my OBXt is set to 7500

i'm not going to lie... it sees that on a regular basis.. and loves it!

but yeah, i think some people call that the 'mexican tuneup'

not to offend anyone or anything

 

I thought it was the Italian tune-up.

[nipper]

Another reason for redline is engine balance. If you want much above that you need a blueprinted engine. Granted some other parts might be needed too.

 

Jamal has it right. Power is the cross product of torque and rotational speed.

 

What does the ECU do at redline, just not inject any fuel on some cylinder for one stroke?

 

The ECU cuts fuel, as another consequence above indicated red line is emissions.

 

nipper

[jamal]

What does the ECU do at redline, just not inject any fuel on some cylinder for one stroke?

 

SVX and 1st gen Legacy automatics upshift.

[porcupine73]

Ah ok. What if you have it in 1 hold? In '00obw it runs up to the redline then just tap tap taps the redline. Like in scary movie n when that guy is driving that red sleigh like in narnia. Not that I do that all the time, it's just the thing is so eager to get out of first gear like it's the plague.

[ericem]

SVX and 1st gen Legacy automatics upshift.

 

yup even in manual mode it overrides it.

[jamal]

Ah ok. What if you have it in 1 hold? In '00obw it runs up to the redline then just tap tap taps the redline. Like in scary movie n when that guy is driving that red sleigh like in narnia. Not that I do that all the time, it's just the thing is so eager to get out of first gear like it's the plague.

 

When the Impreza came out, the TCU got fuel cut logic, but the 1st gen legacy and SVX kept the "upshift" logic.

 

Even with the selector in 1 it will upshift. In 2-manual mode (which only works in 2 and 3) it will still upshift to 3rd. When you slow back down it will downshift, sometimes rather abruptly.

 

Can you tell that I read endwrench articles for fun?

[firstwagon]

 

 

Cool, an oil pressure guage!

 

I've run the 2.2 in my 91 Legacy to the redline countless times. It's the only automatic car I have ever owned that will snap off perfect shifts right at the 6500 redline everytime.

[ericem]

When the Impreza came out, the TCU got fuel cut logic, but the 1st gen legacy and SVX kept the "upshift" logic.

 

Even with the selector in 1 it will upshift. In 2-manual mode (which only works in 2 and 3) it will still upshift to 3rd. When you slow back down it will downshift, sometimes rather abruptly.

 

Can you tell that I read endwrench articles for fun?

 

no, maybe you jsut drove your car, and tried hitting the manual button and experimenting like me