1 Bar stock motor

[DammitBobby]

Current setup stock rebuilt motor, JWT, Z32 MAF, 740cc, Walbro, SAFCII, T3/T4 .48 AR turbine, Zeitronix wideband with electronic boost controller. I have been running this setup for over 500 miles at 12psi. A couple of days ago turned up the boost to around 14.5psi. The car ran strong with no issues. Today while installing my Altima fans I notice smoke coming out of my oil breather. I ran a compression test to find these results

1 1702 403 1704 170

I took the car out for a drive anyway noticed that the idle was eracted up and down. It stalled out a few times which it never did since I recirculate the new HKS BOV. My butto meter tells me that it was loosing power.

Now I have to figure a way to fix it.

1. Replace the bad piston and ring with one new stock piston.

2 Replace all 4 pistons with racing pistons.

Now I am just wondering what do I really need to replace?

[Florida240sx]

How many miles??? Could be a ring is stuck. Try some ring resealer. Run a day or 2 and see what happens. If ity doesn't work then your call. Either $10 for new ring or $500 by the time you get pistons and block bored.

[DammitBobby]

500 miles on rebuilt block.

[SeanC]

did you break it in easy? cause if you did that is probably not good.

[MarkEmark]

500 miles on rebuilt block.

Dammitbobby, that's not good...if you had it rebuilt, why did you go with stock pistons? The ringlands of those things are pathetic. Mine were blown after 10 psi from a small T3...

I'm also curious as to how you broke it in...mine's being broken in the "gradual" method...that is, nothing past 4 psi till after 1000 miles.

I highly doubt that if your #2 is only at 40 that ring re-sealer will do any good.

I say replace all 4 with racing pistons (lower CR) so you don't have to worry about them...if #2 went for no apparent reason (because it was tuned well), then any of the other stock pistons are liable to be destroyed unannounced as well.

I'm sorry to hear that though.

[HolyShiznit]

That sucks man. I had two stock motors survive 1 bar of boost and did the no-break in method. Sorry to hear, hope it goes all well.

[S14tat]

wow that sucks. what happend? i mean they're not suppose to blow at 1 bar. or atleast not in such a short time. we seem to be running very similar setups too. i see on reason in your car blowing a piston.

[DammitBobby]

When I first installed the engine and cranked it up with no turbo installed open manifold. I let it idle for probably 30 minutes total time to fix all the problems. After that I tried to boost but the turbo compressor wheel rubbed the compressor housing. After getting the turbo fixed I started boosting around 10 psi then bumped it up to 12psi. I replaced the knock off bov with a HKS bypass valve and had my ic hot pipe completely rebuilt. After getting all that fixed I had the wastegate dump to atmosphere. Then the boost design manifold had to be repaired for 2nd time because the wastegate pipe came loose from the manifold. Added a another support and rewelded the wastgate pipe. I think I have driven the car around 500 miles since replacing the new engine. This week I cranked it up to about 1 bar and boosted maybe 4 times drove it home no problems. Didn`t notice a problem until I saw smoke coming out of my oil breather while working on the Altima fans.

[DammitBobby]

Yea I think I am leaning towards replacing all 4 pistons with a new set of racing pistons. I am just wondering what else has to be replaced other then the gasket set. I purchased this engine rebuilt from somebody else so I am not sure what pistons they used. My guess it is probably stock or stock replacements.

Now I have to figure what needs to be replaced. I am just wondering if I can just reuse these parts again?

Main boltsRod boltshead boltsbearings

[Titan]

i mean they're not suppose to blow at 1 bar. or atleast not in such a short time.

For the last time people.

We are talking dynamic pressure here. PSI is worthless without airflow, CFM.

This is why air tools are not only rated in pressure, but in CFM as well.

This is also why 10 psi on a T25 is completely different from 10 psi on a T3/T4.

Simply 1 bar does not mean anything without mentioning the turbo being used.

[hannibal]

^ It wasnt too much airflow that caused the ringlands to go. It was pressure...

Its kinda ballsy to run 1 bar on a stock motor with JWT for management. Not saying its a bad setup, but youre pushing it to the limit. How does the 0.48 turbine do with that much boost? No falling off up top?

[DammitBobby]

No it seems to pull all the way to red line.

[S14tat]

For the last time people.

We are talking dynamic pressure here. PSI is worthless without airflow, CFM.

This is why air tools are not only rated in pressure, but in CFM as well.

This is also why 10 psi on a T25 is completely different from 10 psi on a T3/T4.

Simply 1 bar does not mean anything without mentioning the turbo being used.

i am very aware of that, but dammitbobby is not running a T25 or a T3 or even a T3 super 60, hes running a T04E 50 trim and the KA is proven to support that at one bar.

orion runs his that hard almost every weekend at auto X with his 57 trim, nissanfanatic runs over 20 psi with arp head studs and race gas on his 50 trim, and i run 1 bar daily with my 60 trim.

[Titan]

^ It wasnt too much airflow that caused the ringlands to go. It was pressure...

That is not the point.

As I mentioned earlier, you can make entirely different amounts of power at 10 psi with differing turbo's.

The amount of power generated is directly proportional to the stress experienced by the motor, which is consequently directly proportional to the pressure and airflow created by the turbo.

In other words, a KA will be stressed more at 1 bar with a T3/T4, then at 1 bar with say a T25.

Because they are producing the same pressure does not make them comparable.

Point being, simply stating 1 bar is no indication of stress experienced by the rotating assembly.

i am very aware of that, but dammitbobby is not running a T25 or a T3 or even a T3 super 60, hes running a T04E 50 trim and the KA is proven to support that at one bar.

I realize this. Since your post simply said "1 bar" and no mention of the turbo being used, I thought you had that idea.

[SeanC]

i think you may have severly hurt your engine by breaking it wrong. the first 20 min of an engines life directly effect the engines predicted life span. and going easy is the WRONG thing to do.

[DammitBobby]

I realize this. Since your post simply said "1 bar" and no mention of the turbo being used, I thought you had that idea.

My first post pointed out the current setup.

Current setup stock rebuilt motor, JWT, Z32 MAF, 740cc, Walbro, SAFCII, T3/T4 .48 AR turbine, Zeitronix wideband with electronic boost controller. I have been running this setup for over 500 miles at 12psi. A couple of days ago turned up the boost to around 14.5psi. The car ran strong with no issues. Today while installing my Altima fans I notice smoke coming out of my oil breather. I ran a compression test to find these results

[DammitBobby]

I really don`t think that was the problem. 170psi rating per cylinder on the other 3 cylinders sounds like the rings seated to me. I will be pulling the engine out in a couple of weeks to find out what the problem exactly is.

[MarkEmark]

i think you may have severly hurt your engine by breaking it wrong. the first 20 min of an engines life directly effect the engines predicted life span. and going easy is the WRONG thing to do.

Letting it idle for 30 minutes under no load is definitely not the best thing to do for a freshly rebuilt engine, but going easy (under load) is NOT the WRONG thing to do...As has been said before multiple times, there are two schools of thought for breaking in engines, and neither is the wrong way of going about things--Foster broke his in using the "boost right off the bat" procedure and made 430 whp at 20 psi...others, like me, go the "gradual" route for breaking in an engine, e.g., nothing more than 5 psi for the first 1000 miles

I've had 2 engines broken in the "going easy" route....after the first one blew up (unrelated to break-in procedure, it was due to the use of stock rods), it was amazing how well the engine had broken in, which was easy to see just by looking at the pistons and the cylinder walls.

But anyway, as Dammitbobby pointed out, 3 of his pistons/rings seemed to have seated very well...I just think this is an issue of the stock pistons not being able to handle that type of power; mine couldn't hold more than 10 psi on a small T3.

[Edub1]

Just to clarify the physics a little:

Boost pressure is the amount of air being moved by the turbo IN EXCESS of the air being consumed. So, while two turbos might both produce 1 bar at say 3000 RPMs a larger T4 might keep producing it at 5000 RPMs while the smaller one drops off or simply makes heat. Pressure can be made with more O2 or with more heat. The first is good, the second is bad, both can break a motor.

As for the problem at hand. I would do a leak down test to determine if it is your rings or a valve problem. Did you get any metal shavings or debris anywhere in your intake? This can get stamped into a valve seat and ruin your compression. Once you figure out the problem, tear her down and invest a little money into doing it right while you have it apart. I don't know about you but a rebuilt motor worth of my time is worth a lot more than a few hundred bucks in pistons & rods. You have a nice setup, may as well do it right.

Next time take it easy durring break in. Let us know what you find.

[DammitBobby]

Ring land on piston number 2 had cracks in it. Funny thing is that it didn`t come apart until after I inspected and moved the rings around. Then 3 pieces came off in my hand. Piston number 4 had one crack but did not come apart. The cylinder walls look good and still have the cross hatch pattern. I am considering just ordering piston, rods and rod bearings and leaving everything else intact. If any of you are interested I can try and upload the data file from the final tuning on my Zeitronix wideband.

[fiznat]

Im sure it had nothing at all to do with break-in. That's silly. It wasnt a problem with your rings not sealing, it was a problem of mechanical failure of the ring lands. Ring lands do not break in, people.

Anyways. Sorry to hear that Bobby! Seems this is not the summer for OEM KA-T builds. Odd how some people seem so lucky, while others lose compression seemingly instantly, huh? Oh well, live and learn. I say pull the motor out, and build her right. Rods, Pistons, bearings, ARP hardware and a gasket set should just about do ya. You're looking at about $1000-$1200 for the parts, and say another $700 or so in machine work if you do it right. It's a big expense, but at least at that point your motor *should* be ready for just about anything .

[KATwo40]

For the last time people.

We are talking dynamic pressure here. PSI is worthless without airflow, CFM.

This is why air tools are not only rated in pressure, but in CFM as well.

This is also why 10 psi on a T25 is completely different from 10 psi on a T3/T4.

Simply 1 bar does not mean anything without mentioning the turbo being used.

To further add to Edub1's comments on this, I'd like to point out that CFM means diddly squat when it comes to engine air consumption. CFM is a measure of volume, which is not effected by heat, altitude, humidity, etc. If you'll look at a turbo map, you'll find that it's rated in lb/min, which is a measure of air mass -directly related to heat, altitude, humidity, etc.

Additionally, I agree with Fiznat. If you're tearing it down to put forged pistons in there, you might as well go with forged rods, ARP studs (head and main) and do it right. I was in the same boat as you, in terms of rebuild options. I started out swearing I was only replacing the stock rings and bearings...now I'm a few more dollars in and I'm currently building a motor capable of handling up to 550whp.

I'm sorry your motor blew.

[mkory]

In other words, a KA will be stressed more at 1 bar with a T3/T4, then at 1 bar with say a T25.

I thought this was the other way around. I thought less stress is why a t3/t4 makes more power at the same PSI than a t25?

[crzycav86]

no. the bigger turbo makes more power because the intake charge is cooler and more dense, so it has more oxygen per unit volume.. which is more power potential.

[DammitBobby]

Yea I am going with AMS basic rebuild kit which comes with

PistonsAMS RodsMain and Rod bearingsFelpro gasket set

I will add the Arp hardware.

I am thinking I can just hone the cylinders and skip machine shop. All the bearings and cylinder walls look good. The engine only has around 500 miles on it since it was rebuilt.

[j-z]

i was just about to suggest the ams basic rebuild kit. thats what i went with, but i ordered the apr studs, and cometic headgasket as well which i suggest. i completed the entire build up yesterday. i went with stock bore to skip the machine shop. all the clevites checked out, and did a nice hone job. cept i went with the crowers. i was about to ask how the hell is your car running 740s on afc, but then i saw the JWT. i am so glad its over with now.

[DammitBobby]

I am going to go with the new rods unless there is going to be a long delay. I am also considering not replacing the main bearings but I don`t know if I can safely hone the cylinders and leave the crank in place. It would save me another 100 bucks in Arp hardware and another 30 bucks in bearings.

[j-z]

yup, cranks gotta come out to hone the cylinders. you def have to remove the oil squirters, and to do that you gotta remove the crank. itll be worth the extra $$$ for new bearings and such. and you dont have to go arp for the mains. i didnt, i used the stock ones and they went in just fine.

[DammitBobby]

I thought when you used your mains, rods or head bolts that you can not reuse the bolts again?

[j-z]

nah thats just mythical bs. FSM says nadda about that. believe me, thats been my bible for the past week. if nobody has one, youre a fool. should be the first thing you buy for your car.