Just curious....What would happen if I were to rev an EA82T pass the redline? Or what I mean is what kind of damage can I expect if I were to rev the engine too high (what are the weak points)? How high can I rev a stock EA82T without any damage?

 

-Mark

i seem to recall many people talking about 7000. I personally have only had it up to redline. I have enough problems as it is.

Why would you want to? 4 grand is hish enough to grab the peak of the next gear/ hold the powerband. Unless you just like fixing things.

NorthGuy.. You obviously don't have a Turbo:lol:

 

Mine doesn't do much past 6500.. runs out of breath.. with the stock air intake, it would run out about 5800. Shifting at 5500-5800 gives me pretty good reponse. How high you can safely rev a stock EA82T really depends a lot on the condition of the motor.. remember.. these things are 15+ years old.. too much, too often will spell disaster.. its only a matter of time.

YEah, with the EA82T you gotta keep it near 3000-4000 to make power. Not sure what will happen if you run past redline, but as long as you dont do it every day for a prolonged amount of time i dont think much damage can come of it.

 

Dont quote me on that tho.

 

-Brian

I shift my EA82 (non turbo) at 5500 most of the time

I've ran it to 6500 rpms in 2nd and 3rd.. still good power, but it starts droppin at about 5800 rpms

redline isnt so much the motor wants to fly apart, but rather its the valvetrain cant keep up with the rpm, floating and bouncing...

 

its not going to hurt to touch redline, but gouing in the redline has no benefit. but you can take up to 7000 rpm shifting all day if u like

 

the point at which you shift is the rpm you want it to be in for the next gear

I can think of a few scenarios. One, you float a valve, and a piston comes up and smacks it, breaking it off at the stem. the next time the piston comes up, it smashes it into the cylinder head. If you're lucky, just the piston and head are destroyed. Or if the valve hits on the edge of the piston, the piston is smeared into the cylinder wall, scoring that up. If you're not so lucky, the connecting rod breaks in two. The big end is still connected to the crank, at least until it swings around and gets wedged somewhere, ventilating the block in the process.

The next scenario involves the connecting rod bolt, a classic weak link in many engines. You go over redline, and you exceed the tensile strength of the bolt. Bearing crush is reduced, allowing the rod bearings to start moving around. eventually they spin, damaging the crank and the rod. If this continues long enough, the bearing welds itself to the crank, the connecting rod breaks in half, and goes though the hood of your car. Sometimes the con rod bolt simply breaks, and the rod is sh-t right out of your oil pan.

lastly, pistons are only designed to travel so fast. exceed the maximum speed limit, and things like piston skirts crack, or break off, setting off a chain reaction of connecting rod failure and big oily messes.

 

My suggestions for wringing the snot out of any engine: Get good quality connecting rods with good hardware in a longer-than-stock length. This reduces piston speed at certain times during the stroke. It also reduces thrust loads on the pistons. You might need shorter pistons to keep a negative deck height.

Second, invest in some quality valve springs. Finally, make sure things are getting oil like they are supposed to.

Thank you. That is all.

Originally posted by snotrocket

I can think of a few scenarios. One, you float a valve, and a piston comes up and smacks it, breaking it off at the stem. the next time the piston comes up, it smashes it into the cylinder head. If you're lucky, just the piston and head are destroyed. Or if the valve hits on the edge of the piston, the piston is smeared into the cylinder wall, scoring that up. If you're not so lucky, the connecting rod breaks in two. The big end is still connected to the crank, at least until it swings around and gets wedged somewhere, ventilating the block in the process.

The next scenario involves the connecting rod bolt, a classic weak link in many engines. You go over redline, and you exceed the tensile strength of the bolt. Bearing crush is reduced, allowing the rod bearings to start moving around. eventually they spin, damaging the crank and the rod. If this continues long enough, the bearing welds itself to the crank, the connecting rod breaks in half, and goes though the hood of your car. Sometimes the con rod bolt simply breaks, and the rod is sh-t right out of your oil pan.

lastly, pistons are only designed to travel so fast. exceed the maximum speed limit, and things like piston skirts crack, or break off, setting off a chain reaction of connecting rod failure and big oily messes.

 

My suggestions for wringing the snot out of any engine: Get good quality connecting rods with good hardware in a longer-than-stock length. This reduces piston speed at certain times during the stroke. It also reduces thrust loads on the pistons. You might need shorter pistons to keep a negative deck height.

Second, invest in some quality valve springs. Finally, make sure things are getting oil like they are supposed to.

Thank you. That is all.

 

 

...And sometimes the bearings go to hell just from starting the motor up..Sorry snotrocket.. couldn't resist.

Can't bust a valve off - it's not an interferance engine.

 

The aircraft guys run the EA81's at 7500 RPM's all day long.

 

I think a long time ago on the old board it was mentioned that the short stubby rods in our engines would most likely make it well beyond 10,000 RPM's before bursting.

 

GD

it was mentioned that the short stubby rods in our engines would most likely make it well beyond 10,000 RPM's before bursting.

 

I have a pic of an EA82T that belongs to another local North TX soobhead that might make you think otherwise.. A 3 inch hole in the top of the block can be very convincing.. If I can't find a pic, I'll just have to go over there and take another.. I hear he's thinking of keeping the block as a reminder...

 

And GD.. those aviations EA81s are a little bit different beasts than the EA81 in your car.. gets rebuilt a hell of a lot more often..

 

.. And besides.. the motors in question (pursuant to the original post) are EA82T's

Caleb- laugh it up, buddy. j/k I laughed too.

 

I know it's not an interference engine, but picture this. A weak or broken valvespring. An engine running way too fast. The cam launches the valve off of it's lobe, and it stays out there, dangling, long enough for the piston to smack it. Like a bungee jumper with too much rope.

 

Obviously, more of a problem in different engines.

 

Hmm, the first time i saw a subaru connecting rod, I was also looking at a jaguar connecting rod, which is nearly twice as long. I wasn't very impressed. I guess these guys don't have much as far as stroke is concerned?

I have had my EA81's to at least 7000, with no problems. And the aircraft guys use a lot of stock internals too. But I do see your points. I think that rod breakage has a lot to do with the age of the motor. 7000 is nothing for a new engine of this design.... I think that was my point really.

 

GD

i don't know about the turbos, but i know on my old 1600 the valves started floating at about 6600 to 7000. haven't ran my new motor anywhere near that. not planning on it. and don't need to the power band's peak is around 5500 to 6000.

my ea82t wouldnt make it past 7000 under acceleration, but it was a pos car. But it had 370 000km on it, with an on and off headgasket problem, actually most likely cracked heads and I had it around 6500-7000 for probably 30sec to a minute with no damage to the enginee. The motor went after I filled it with water and let it sit for a week, then restarted it and went burning around The main problem with high rpms is wear which increases alot with rpm. Also I could see a weak oil pump giving out, or dropped valves, broken timing belts if they are old and fatigued.

Snotrocket:

 

Changing the conrod length will not alter the average piston speed. The stroke has to be changed to do that, and that is determined by the crankshaft. Yes, I understand you reckon that at some points the piston speed will be different, but it's a minimal gain. Plus, a longer rod is likely to flex more.

 

More revs needs stronger valve springs - as mentioned above somewhere. AND balanced conrods and pistons. No more than one tenth of gram difference please

 

Of course really high revs will require lighter pistons to ease the stress on rods...which ideally would be made of titantium if you plan on 10,000rpm on a daily basis.

 

Pistons spend most of their time standing still, it's the getting from TDC to BDC that's stressing them :-p

Originally posted by Rooinater

i don't know about the turbos, but i know on my old 1600 the valves started floating at about 6600 to 7000. haven't ran my new motor anywhere near that. not planning on it. and don't need to the power band's peak is around 5500 to 6000.

 

Valves floating? explain?

Things get going so fast that the valve spring can't supply enough pressure to close the valve before its time for it to open again.

When the piston is in the middle of it's stroke, it is moving at it's highest velocity. This is also the time that thrust loads are highest. A longer rod would help alleviate these thrust loads.

 

Alright, i'll accept that longer rods could flex more. However, a Subaru has the shortest connecting rod I have ever seen. I think you could lengthen them SOME. All other engine can't possibly suffer from their longer rods flexing. Besides, that's what 4130 grade steel is for.