Engine blown what do you guys think

[troll's 240sx]

Hey guys this is another engine I have blown and just wondering what you guys think happened because this is the first like this I have seen. I tore apart my engine to find out that all the piston walls had cracked, no blown seals, piston rings or anything, just the walls between the rings. Was boosting at 10psi with a JWT ecu and SAFC.

[:: orion ::]

That's common on KA...cracked ring lands.

They break before the HG blows, before the rings go.

Looks like:



- Brian

[:: orion ::]

What adjustment did you have on the S-AFC?

The rest of your setup (MAF, injector size, turbo, boost, etc...).

[troll's 240sx]

Exactly like that picture. SAFC adjustments I dont remember well but setup was T04x turbo .48/.60 A/R 60trim, z32 MAF, 50lbs msd, boost was set at 14psi but only saw 10psi on the gauge, JWT ecu,

[troll's 240sx]

How fast should boost response be with this turbo, because I driven other turbo cars and theyre response is slower.

[klattr1]

did u ever get a wideband on your car (to verify afrs)?also, how did u set your base timing?and what octane fuel did u use?

[troll's 240sx]

No was hoping to run long enough for me to get a wideband but I had an AFR gauge hooked up and it reads rich everytime I start boosting and when I am not it goes ideal. Base timing was at 15 BTDC, and 91 octane.

[nissanfanatic]

You either:

Didn't set base timing correctlyRan too hot of a heat range plugGot bad gasor Ran lean.

That narrowband POS will read rich at 13.9:1 AFR..

Fuel pump setup?

And why did you use any correction on the SAFC? That should have set to 0% at all RPM on high and low throttle until you tuned...

[sunnys14]

geez! makes me kinda scared because im running 10psi also...

[nissanfanatic]

Why?

10psi or -5in HG vacuum... if you are detonating then you will end up with the same thing....

[Edub1]

I bet if you call JWT they can tell you. Did you consult JWT on using the SAFC? By the way, was this a JWT turbo tune or N/A? I think the N/A tune advances the timing.

How many miles are on those pistons?

[troll's 240sx]

Ecu was tuned for these specs, base timing was done tps disc. and everything. Anything could be a possibility, plugs were NGK iridium but I dont know if are the correct range though. Gas was freshly pumped in and yea I know the gauge is a POS, but better than nothing. My fuel pump was a walbro, and the reason for the SAFC was because it you ran it hard then engine wants to rev to redline when your coasting, until the engine cools down. Still didnt fix the problem but fixed the rich idle though, I figured it needs to run rich anyways at boost so I just adjusted it for idle.

[Edub1]

Well you defenitly had something wrong if it was running all wacked out. Trying to guess it back in shape with the safc probably wasn't the best idea. Oh well, what's done is done - get some better internals and have another go at it.

[scarboroughdub]

post your afc settings if you have time then we can see what you did wrong if it was at the afc point.

[nissanfanatic]

did you set timing like so?

http://www.ka-t.org/tech

[Jookmasta]

i think this couldve been prevented with a purchase or borrow of a wideband............gotta know where u stand. ur timing sounds very conservative as i would think u would leave base timing to stock with an upgraded ecu right? ya post ur safc maps.

[troll's 240sx]

Setting my timing was from that link and also I had the Nissan repair manual as well. I already disconnected my SAFC and all I remember was on the graph it was -20% all the way to 2500 rpm then 0% because I havent got that far into it. I ran it like this for about 2 weeks, and the only other problem I had was either clutch was slipping or no traction at full boost. The high rev during coasting happened twice but didn't last long though. Let me hook it back up to see if the settings are still there then I will post it.

[troll's 240sx]

Ok settings were

LO - 0%HI - 50%

Dec Air NE 1 - 2.5%NE 2 - 3.5%

Hi throttle-10% across to 2500 rpm

Lo throttle-25% across to 2500 rpm

NE points were 1000 increments

[Jookmasta]

yup u may have very well been running lean. the rumor or avg thing is for jwt ecu tunes to run rich but since u dont know ur a/f's, whose to say how lean u were? also ya ring lands are just something that varies from car to car. some people are lucky, others arent so lucky. when it went on u, were u in boost?

[Edub1]

You have no way of knowing what effect this had in combination with the JWT tune. Was the JWT ECU set up to correct for larger injectors? Then did you make another correction? This would cause a super lean condition and possibly cause the ECU to advance timing thinking it's in closed loop. Unless you know everything JWT did and figure it into everything you did, you'll never know.

Just forget about it and start rebuilding. Just don't use that combo untill you talk to JWT. They will probably be willing to re-tune for your new setup for not too much $$ and you can sell the SAFC.

[nissanfanatic]

I say that you didn't set timing correctly. Its so easy to do... I thought I set mine to 20* BTDC, borrowed Anthony's techtom and found out I was at 15*BTDC...

JWT ECUs aren't wrong very often. I know of only one person who has had a blown motor as a direct result of JWT...

10% across to 2500 meaning you didn't adjust any fuel settings past 2500rpm on high throttle right?

If so, then it wasn' a lean condition...

[troll's 240sx]

As of now it is just one more reason for me to rebuild the engine for boost, and get a better monitoring system. Oh and the engine didn't cut out right away, it was in boost until about a mile away from home. It felt weird after the last boost (gee I wonder why) so I decided to just keep it out of boost. I drove it home, parked my car in the garage and then it cut while the turbo timer was on. Cranked it and no compression then. I greatly appreciate all the comments.