8.5:1 CR to 9:1 CR with JWT ECU, reflash? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

180Sil · 08-09-2008, 10:51 PM

I just had oil shooting out of the dip stick, major blow by, and oil on a couple of spark plug so time for a rebuild. But I'm running a JWT ECU with 740cc nismo and m62 maf with a 2871 .64 gtrs style. Right now I'm trying to decide between an OE rebuilt or a full rebuilt, reluctant for full due to $$$ issues. My goal is 400whp or 20psi with this setup, but reliable for track (2-3 times a year) and it's my daily driver. Maybe anything close to those goal is acceptable with an OE rebuilt.

Something like this is to be expected from these older sr20det motors under these extreme condition but I really don't have the $$$ for machining the block for oversize and pistons and rods and bearings and seals, etc.

One reason I was told my rings might have failed is because the car runs rich (10.5 a/f) at idle but is normal once boost hits (11.25 a/f). I don't know why this happens but it could be a bad O2 sensor, didn't check yet.

So the question is, do I need to send in the ecu for a flash due to increase in compression? I don't want the downtime as this is a DD. Will I be able to use afc, emanage blue to adjust the jwt ecu for the difference in compression and what will happen from the different in compression?

*1QUICK4* · 08-09-2008, 10:55 PM

If you would have gotten an Enthalpy Ecu you wouldn't have any down time.

But the only nice thing about JWT is you can just call them up and ask.

180Sil · 08-09-2008, 11:06 PM

Quote:

Originally Posted by 1QUICK4

If you would have gotten an Enthalpy Ecu you wouldn't have any down time.

But the only nice thing about JWT is you can just call them up and ask.

unfortunately my situation is with a JWT and they're not open tomorrow so I figure someone on the forums might know something while I do some research and gain more information to better help me make the right decision.

l20bdime · 08-10-2008, 04:31 PM

If you tell JWT what your compresssion is they can optimize the tune. Do it. I have lower compression in my KA-T and they tuned it to compensate for the sluggishness related to lower compression. mainly timing.

*fliprayzin240sx* · 08-10-2008, 05:27 PM

Hate to say it but do it right, do it once. Pretty sure the blow by is coming from the piston rings going bad. You cant exactly just expect to slap some new rings and everything will be dandy. You will probably need to rehone (not bore out) the block to make sure the new rings will seal properly. Then since SRs are notorious for having crappy rod bearings, you might as well replace them with some new ones, specially since youre gonna have to pull the rod caps off to get the new rings in.

If your really in a bind, you honestly, might be better off looking for another bottom end/block. Its usually still the cheaper alternative to all that work. Get another engine and just swap everything over.

08-09-2008, 10:51 PM	#1
180Sil Zilvia Junkie Join Date: Feb 2007 Location: LI, NY Posts: 419 Trader Rating: (9) Feedback Score: 9 reviews	8.5:1 CR to 9:1 CR with JWT ECU, reflash? I just had oil shooting out of the dip stick, major blow by, and oil on a couple of spark plug so time for a rebuild. But I'm running a JWT ECU with 740cc nismo and m62 maf with a 2871 .64 gtrs style. Right now I'm trying to decide between an OE rebuilt or a full rebuilt, reluctant for full due to $$$ issues. My goal is 400whp or 20psi with this setup, but reliable for track (2-3 times a year) and it's my daily driver. Maybe anything close to those goal is acceptable with an OE rebuilt. Something like this is to be expected from these older sr20det motors under these extreme condition but I really don't have the $$$ for machining the block for oversize and pistons and rods and bearings and seals, etc. One reason I was told my rings might have failed is because the car runs rich (10.5 a/f) at idle but is normal once boost hits (11.25 a/f). I don't know why this happens but it could be a bad O2 sensor, didn't check yet. So the question is, do I need to send in the ecu for a flash due to increase in compression? I don't want the downtime as this is a DD. Will I be able to use afc, emanage blue to adjust the jwt ecu for the difference in compression and what will happen from the different in compression?

08-09-2008, 10:55 PM	#2
1QUICK4 Stop or I'll Shoost Join Date: Aug 2007 Location: ND Age: 40 Posts: 648 Trader Rating: (0) Feedback Score: 0 reviews	If you would have gotten an Enthalpy Ecu you wouldn't have any down time. But the only nice thing about JWT is you can just call them up and ask. __________________ -383 RWHP & 407 RWTQ- Review Thread= http://www.zilvia.net/f/showthread.php?t=201106

08-10-2008, 04:31 PM	#4
l20bdime Zilvia Member Join Date: Aug 2005 Location: san diego Posts: 177 Trader Rating: (1) Feedback Score: 1 reviews	If you tell JWT what your compresssion is they can optimize the tune. Do it. I have lower compression in my KA-T and they tuned it to compensate for the sluggishness related to lower compression. mainly timing. __________________

08-10-2008, 05:27 PM	#5
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	Hate to say it but do it right, do it once. Pretty sure the blow by is coming from the piston rings going bad. You cant exactly just expect to slap some new rings and everything will be dandy. You will probably need to rehone (not bore out) the block to make sure the new rings will seal properly. Then since SRs are notorious for having crappy rod bearings, you might as well replace them with some new ones, specially since youre gonna have to pull the rod caps off to get the new rings in. If your really in a bind, you honestly, might be better off looking for another bottom end/block. Its usually still the cheaper alternative to all that work. Get another engine and just swap everything over. __________________ If you think Zilvia has too many assholes... CLICK HERE!!!