stock internals

[UnderPressure]

ok i searched and im not a n00b, so chill guys and girls

i read that someone was running 15psi of boost on stock internals. is this safe? i like it! what is generally accepted on stock internals? would a thick head gasket help to drop compression- or is it pistons/rods that just cant handle it?

i want about 350-400hp, my only limitation is what i trust pump gas on. recomendations?

(Im gettin an s13 ka-t in the next month or two, anyone wanna buy a jeep wrangler?)thanks guysChris

[fo0manchu]

i hear that the ring lands on the pistons are one of the weakest parts of the motor when boosting and tend to break but not I'm not sure as to what horspower beating they can take before they go. Anybody shed light on that? But I would recomend getting some forged pistons anyways if your gonna run 15psi.

[C-Kwik]

If the ring lands break, then you are probably experiencing detonation. Ringlands are usually the first thing to go an forged and cast pistons. Detonation usually occurs near the ringlands. Forged pistons will hold up to detonation better than a cast piston, but will still fail under sustained detonation. Tune the motor so there's no detonation, and you will have little to worry about.

[UnderPressure]

sounds pretty straight foward. i was wondering if there was any understood or norm max pressure on stock internals. anyone have any guide lines?

[TrunkMonkey]

sounds pretty straight foward. i was wondering if there was any understood or norm max pressure on stock internals. anyone have any guide lines?

the only guideline you'll hear is to avoid detonation. as far as limits, no one's reached it yet...

but i have heard things start sounding weird around 17 psi .

-demetrius

[im two techno]

I think if you have a machine shop grind 3 rings around the landings to hold fuel around the crown you will have less chance of blowing a land. And chrome rings will also help.

http://www.dsm-performance.com...6c85b

Also notice the anti-detonation grooves around the top ring land of the JE.

[WDRacing]

Kill detonation...its realy that simple. Don't forget to have your timing maps retarded on boost. Eventually you'll run into metal fatigue limits, but not till over 400. A good lubrication/cooling system with some good tuning will generate good numbers.

WD

[rco8786]

it is Dennis(d240t) that runs 15psi daily on a stock bottom end. like WD said, detonation is what you need to worry about. The ring lands will be fine unless you have detonation. I think that w/ our compression somewhere around 16-17psi is the practical limit on pump gas.

BTW - Dennis dynoed at 352whp w/ a T3/T04 I believe so that should be about in your range. Maybe w/ a straight T4B and some 70lb injectors you could hit 375-400 on stock internals. I dunno that I would run that daily tho...you probably won't even want to, that is god awfully fast.

[t4 mr2]

Boost shoudln't be your concern. The ringlands on a DE piston aren't any thinner than on a Saturn, D16z or any other motor that didn't come with a turbo. Internal combustion engines are just that they all operate on teh same principle. People who say that running 15 psi is max on a KA motor typically won't know what they are talking about and are probably speaking from someone elses experiences. (Oh I heard so and so blew up there motor at 15psi, so now we know a KA can't do more than that) I know this because thats what rumor starts in every web board/community. I was told 4 years ago that a stock mr2 turbo motor could not sustain more than 350rwhp before the rods start to fail, and no less than 3 years later I proved them wrong. Same with teh SR motors, S.S. proved that they can push that sucker to the limits as well. I help push 310whp on a bone stock SOHC 1.6 honda motor. Its all in the tuning, keeping detonation in check. Not only detonation though, you must also remember preignition. These two things shock the ring land and cause motor failures. I would say 80% of KA-T's that blow up are due to timing and rarely fuel related issues. Everyone always remembers the fuel but never the timing. Timing IMHO much more important than that of fuel. Though you need them both. Timing is the killer. I am willing to bet money with a good HG and ARP head studs, a bone stock KA bottom end can handle atleast 20psi or more. With the right turbo (sized properly), superflorous intercooling, EMS, and good flowing head, I would say 500rwhp is very attainable. Tuning is the key.....

My next project is proving just that, I have a 96 KA motor and will be pushing it to the limits.

[rn240sx]

t4 mr2 wrote:I am willing to bet money with a good HG and ARP head studs, a bone stock KA bottom end can handle atleast 20psi or more. With the right turbo (sized properly), superflorous intercooling, EMS, and good flowing head, I would say 500rwhp is very attainable. Tuning is the key.....

Proper tunning is very important I agree, but I seriously DOUBT that our stock rods will hold that much pressure...Now since we are discussing this, a buddy of mine had a turbo civic pushing 7 psi on whatever size turbo he had. They had it on the dyno, ran about 6 runs, each run adding more boost and more fuel and a/f was reading fine thru all runs until they got to 13 psi on the 6th run, Rod # 3 snapped and broke thru the block..It wasent a timming issue, wasent leaning out, just too much power for those rods....

[t4 mr2]

I still don't think so. RPM tends to kill rods not pressure. again this is my own opinion. We will see. Since my goal is 500rwhp no bottle. To be honest KA24DE rods are thicker than 2nd generation 4g63 rods (they take a crazy amount of punishment). And its highly doubtful that the metallergy is different. Rod ratio is different for sure but the piston speed shouldn't be too dramatic. Especially since I don't plan on keeping the revs up for too long a period. Only time will tell.

[C-Kwik]

I'd like to see the rods that broke myself. The piston too. I have doubts that it was the pressure that caused the rod to fail. At 13 psi, the cylinder will likely see a less than 50% increase in peak cylinder pressure over an atmospheric motor. I'm not sure which motor you are reffing to, but if it's a high revving one, then the rods will likely be beefy due to the fact that rods need to be able to handle the tensile load(the inertial pulling during the piston's upward movement in the cylinder) much more than hey need to handle the compressive load. Compressive load failures will be abrupt. Tensile loads promote fatigue. So an engineer designing a motor will need to make sure the rod is able to handle the tensile load. Probably even overdoing it some. And since tensile load is higher with RPM, High RPM motors need some relatively beefy rods. The side effect is that the rods would be stronger overall as well. And a change in power does not affect the tensile load as tensile load is highest during the exhaust stroke at TDC.

[t4 mr2]

My sentiments exactly.. Much better stated by you of course. And after looking at the numbers of the KA's rod ratio and width, with a ratio of 1.71 I definately do not see a problem. When rods fail when boost pressure is increased its most likely to preignition, too much timing advance. Explosion happening before the down stroke begins causing the rod to fail due to "shock". I am almost guaranteeing that the rings of that piston (attached to the rod that failed) are compressed into the ringlands (sandwiched if you will). And no longer free moving.

Earlier you stated:They had it on the dyno, ran about 6 runs, each run adding more boost and more fuel and a/f was reading fine thru all runs until they got to 13 psi on the 6th run, Rod # 3 snapped and broke thru the block..It wasent a timming issue, wasent leaning out, just too much power for those rods....

A/F has nothing to due with timing... I can be runnning a dead fat 9.9 a/f and still kill my ringlands. What was his timing on his boost runs? Stock? What sort of timing retard did he have? What engine management was he running? What was his max timing value at "X" boost pressure. What gas was he running on. Because if he was on pump and his boost was over 15psi with more than lets say 30degress of timing at 7000rpm, this would be a combination to kill any NA-T motor...

[C-Kwik]

When rods fail when boost pressure is increased its most likely to preignition, too much timing advance. Explosion happening before the down stroke begins causing the rod to fail due to "shock". I am almost guaranteeing that the rings of that piston (attached to the rod that failed) are compressed into the ringlands (sandwiched if you will). And no longer free moving.

Actually, combustion is supposed to start during the upward stroke. Of course, if it starts too early, the rapidly expanding gasses will cause too much pressure and heat and lead to preignition/detonation. Most motors make peak pressure at about 20 degrees ATDC. And in most cases, detonation occurs on the downward stroke. Detonation does create a shock. But if it's enough to break a rod, the piston would likely be in very bad shape. Pistons are the weakpoint in most motors.