Looking for advice on my KA-T build...

[Nismo_Freak]

Bearing load is directly proportional to the amount of torque you are making. 350ft/lbs of torque is the same on 10:1 CR as it is on 8:1 CR. It is the same on 87 octane as it is on 116 octane. The real benefit of using lower CR pistons is so you can make more whp on lower octane fuel. I'd undoubtedly go with prolly 8:1 if I coudl find them just so it was easy breezy to make 400whp on pump.

For overboosting...http://www.ka-t.org/overboost.htm

True, but to really get a good picture of bearing loads you have to take cylinder pressure over the entire combustion event. Having 3000 PSI of pressure in the cylinder while the rod is at a wide angle does not put the same load as 3000 PSI at TDC. Likewise the pressure will not dissapate quickly at TDC due to the KA's dwell time whereas the pressure is momentary at the wide rod angle.

[AZhitman]

I ordered the 9.0:1 CP pistons, .020 over and the Crower rods.

[nismofly]

good call

people seem to be missing the "overbuild cause im on my 3rd engine" part

decided on what youre going to do ecu wise yet?

[AZhitman]

Not sure yet... Leaning towards a JWT, but open for suggestions.

I wanna get rid of this SAFC-II completely.

[Edub1]

AZ, any thoughts on why you have been through 2 motors?

[nismofly]

Greg if you want rid of the safc completely, JWT are very conservative tune...youll probably need the safc to pull it back

i think your best bet would be to get a tune from enthalpy

[sunnys14]

enthalpy is the best

[Arrow]

Understood.

Maybe I'll turn up the boost someday...

I honestly think this car will be an absolute screamer with the 5-speed, ACT S/S clutch, weight reduction, UD pulleys and 4.36 rearend.

Greg where did you find a 4.36 rearend?? and how is that going to affect your topend? seems to me like your car's going to be sick at accelerating with that rear but is going to lack in the top end... pretty much personal preference though... but man that does look like a great set up and I'm with you on the 'overbuilding' deal. That is also my plan but I won't be putting it into action until after college... and possibly longer as I might not be in the country for a while after graduation (possibility of me joining the peace corp or something).... but good luck on getting this thing finalized and I'm glad to see the progress!

[AZhitman]

AZ, any thoughts on why you have been through 2 motors?

1st one was original motor, 140K miles - Too much power on a tired engine. Rod bearing cracked.

2nd one was a fresh OEM rebuild in which the builder apparently has no clue how to orient rings... Bad compression across all 4. Never even ran right.

[AZhitman]

Greg where did you find a 4.36 rearend?? and how is that going to affect your topend? seems to me like your car's going to be sick at accelerating with that rear but is going to lack in the top end...

Local shop sourced it for me from Japan.

Bleh, I have a 5-speed. First gear will be useless, but I have no need for real big top-end power... Should be a BEAST in 2nd / 3rd / 4th gear, with 5th good for freeway cruising.

[Edub1]

I know a guy who installed a real low gear in a Mustang and lost his 1st gear. If you haven't installed it you might want to think twice.

[Edub1]

1st one was original motor, 140K miles - Too much power on a tired engine. Rod bearing cracked.

2nd one was a fresh OEM rebuild in which the builder apparently has no clue how to orient rings... Bad compression across all 4. Never even ran right.

Forget the second motor then. How hard were you pushing the 1st? 140K is not a young motor though. Perhaps if you expect 200K pushing past 200HP you might need all the aftermarket stuff.

It would be interesting to see how long the KA lasts under various boost. I'd be willing to bet that pushing near 300HP reduces the longjevity quite markedly.

[AZhitman]

The first motor saw 8psi but ran like a freaking raped ape with a cherry bomb in its arse for about 5 minutes...

Seat-of-the-pants tells me it was quite a bit faster than the 230rwhp S13 hatch I've driven countless times.

The #2 rod bearing snapped in half.

That motor is being further dismantled tomorrow...

Any thoughts on the KA oil pump? High performance availability?

[nismofly]

The first motor saw 8psi but ran like a freaking raped ape with a cherry bomb in its arse for about 5 minutes...

i dont remember if you came to a conclusion...but if you say it was a lot faster than 230, is it possible you had an overboost issue, and thats what killed it?

Any thoughts on the KA oil pump? High performance availability?

methinks you might try talking to devious on that one, but i believe the L28 oil pump fits and flows quite a bit more

[AZhitman]

i dont remember if you came to a conclusion...but if you say it was a lot faster than 230, is it possible you had an overboost issue, and thats what killed it?

Well, the boost gauge never exceeded 8 psi, but it IS possible that it ran lean for a short time. However, I'd think that would result in piston damage (there was none) rather than bearing failure.

I think it was just a tired motor, with some loose tolerances, and another 100+ hp was too much for the #2. Maybe some oil starvation as well...

[nismofly]

yeah, probably was just wear causing the bearing to go

im glad my sohc only has 81k, i plan on having it rebuilt by the time it hits 100k, im just going to have a lot on my plate car wise in the next few years and ill have to see where rebuilding this engine, or another one for that matter, comes into the picture

[DammitBobby]

think it was just a tired motor, with some loose tolerances, and another 100+ hp was too much for the #2. Maybe some oil starvation as well...

Yep same thing happen to mine except the bearing was intact just wiped out. Dam did it make a bad knocking noise!

I second the Enthalpy tune. I am running JWT(bought used JWT 740cc) I will let you know how well it works when I get my car back from the shop. Before I took it to the shop the car would stall out at every light and it was running lean after it warmed up at idle. I am replacing the knock off BOV with a HKS racing bypass valve and recirculating it. Having a shop do the install. This guy does really good work and knows his turbo stuff. I saw him fab a turbo on a big V8 truck and his welds looked better then anything I have seen on the internet.

[Edub1]

Are you trying to say it might have been from beating the hell out of a motor with 140K on it? LOL

Which brings up a good question - what kind of longevity should we expect from these motors once you slap a turbo on them?

I just created a survey about KA-T longevity. I think it would be helpfull to collect some good raw data on this subject.

I think I clicked on "create a poll" by mistake but whatever. Perhaps someone can fix it.

[smokey240sx]

Are you going to use ARP head studs? ARP have a new design for that require torquing after 2000 miles. I have 2 buddies that blew their headgasket because of it.

[Nismo_Freak]

Are you going to use ARP head studs? ARP have a new design for that require torquing after 2000 miles. I have 2 buddies that blew their headgasket because of it.

You are supposed to retorque head studs, even OEM ones.

[TurboChargedSE-R]

AZ (Greg), check your email.

[Florida240sx]

My #3 bearing went bad on me.Due to leaking injector.By time I realised it was too late. Slight knock so I just parked it. Goign to have that engine built

[nissanfanatic]

True, but to really get a good picture of bearing loads you have to take cylinder pressure over the entire combustion event. Having 3000 PSI of pressure in the cylinder while the rod is at a wide angle does not put the same load as 3000 PSI at TDC. Likewise the pressure will not dissapate quickly at TDC due to the KA's dwell time whereas the pressure is momentary at the wide rod angle.

I see exactly what you are saying. Peak Cylinder Pressure happening too early will put a lot of load on the bearings as opposed to it happening when its supposed to. But I definatly would not buy that bearings fail before ring lands do in this scenario.

More than likely, rod bearings fail due to previous owners not allowing the engine to warm up sufficiently before beating on the car. I always let my car run at idle for a minute after starting from cold, and then drive really easy for the first 15 minutes or so.

[Nismo_Freak]

I see exactly what you are saying. Peak Cylinder Pressure happening too early will put a lot of load on the bearings as opposed to it happening when its supposed to. But I definatly would not buy that bearings fail before ring lands do in this scenario.

An engine is intricate, failures are always a combination of events.

I'm willing to bet Greg's engine failure was due to poor oil pressure, and possibly overheating the oil as well. KA's are not a very tolerant engine when it comes to bearings. Strong, yes... reliable, thats up to debate.

[Iamjohnhayes]

i would have to say the KA is a very reliable engine. i have a friend of mine with a 90 240sx with just about 300,000+ miles on it and all he does is keep up with his oil changes and it still runs almost perfectly. although he has no intentions of using the car for anything other than transportation. I think if you turbo any motor with 100,000+ miles on it w/o doing anything to freshen it up you have to expect it to fail some time. I'm about to turbo my 89 pignose with just about 185,000 and i know its gonna blow up some time but im gonna run it strong until that happens.

[Nismo_Freak]

i would have to say the KA is a very reliable engine. i have a friend of mine with a 90 240sx with just about 300,000+ miles on it and all he does is keep up with his oil changes and it still runs almost perfectly. although he has no intentions of using the car for anything other than transportation. I think if you turbo any motor with 100,000+ miles on it w/o doing anything to freshen it up you have to expect it to fail some time. I'm about to turbo my 89 pignose with just about 185,000 and i know its gonna blow up some time but im gonna run it strong until that happens.

I meant reliable in a performance racing sense. If you putt the thing around and keep it maintained then yes, you will see long life just like most engines out there.

Also, can you decrease the size of your sig? There's alot of room being taken up and I am running on a large resolution.

[nissanfanatic]

Quote »An engine is intricate, failures are always a combination of events.[/quote]Given.

Quote »I'm willing to bet Greg's engine failure was due to poor oil pressure, and possibly overheating the oil as well[/quote]Could be. There's really no point to us speculating on what happened to it anyways. Its broken. End of story.

I stand by my KA as being reliable. It has been so far.

[AZhitman]

Ordered high-volume oil pump today as well - Added insurance....

[Edub1]

If you haven't already, you guys might want to contribute to the longevity survey. Once we have a good sample of data we might get a more acurate picture of how well these motors hold up under boost.

[nissanfanatic]

Look into shimming the pressure relief valve as well.