Strange compression result sr20det RWD 5-speed - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Kingtal0n · 05-20-2016, 09:32 PM

Had a very strange result on a friends car
cylinder #1 through 4
dry test (no oil)

140
151
140
151

IS there something obvious causing this? I seem to recall seeing this before.
engine is mostly stock redtop, but i know somebody changed the cams.
something about valve seals? or maybe we need to degree his cam...

supersayianjim · 05-21-2016, 12:30 PM

bump for an answer??

Kingtal0n · 05-21-2016, 07:55 PM

Well. It is a friends car, he wants to go forward with the tuning despite the strange readings. I am not sure I can convince him to open the cover and degree the cams. I am still waiting for him to tell me if they did the valve seals while in there. I think we might need a leakdown test next step, but neither of us has an air compressor handy. Hmm. I do but in miami so... gota think about this. I just seem to recall from 5 years ago a similar thread, and they found something like this...

zombiewolf513 · 05-21-2016, 09:14 PM

Is that cylinder one through four, or four readings on one cylinder?

cotbu · 05-21-2016, 10:05 PM

If you did both dry and wet like you should, you would at least have narrowed it down to Rings or valves. You could even make it worse or better? By finding a 5psi increase from the wet test. Then where's the other 5 or 6psi???

I don't know if you performed the wet test or if you had all the plugs out, but I guess you searching for that related post

You have to verify timing if you are going to tune, and if you tune with a question on your mind, you're just like the rest of the cats in this game.

Kingtal0n · 05-22-2016, 06:34 PM

next time i see the car i will do the oil/ring test. I Dont think its the rings though. Very unlikely both cylinders have exactly 10psi worth of ring "loss" perfectly like that, its just very strange if that were true. I think it more likely that something with the valves/cams.

and fwiw I never had any reason to degree wheel any camshaft in an sr20det before. Must have tuned 50 to 80 of these engines. It usually isn't an issue, you get a tomei cam, install a tomei cam, and go to town right away.

05-21-2016, 12:30 PM	#2
supersayianjim Nissanaholic! Join Date: Jan 2010 Location: location X Posts: 1,815 Trader Rating: (10) Feedback Score: 10 reviews	bump for an answer?? __________________ http://www.240sxforums.com/forums/rb...ject-s-rb.html

05-21-2016, 10:05 PM	#5
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 50 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	If you did both dry and wet like you should, you would at least have narrowed it down to Rings or valves. You could even make it worse or better? By finding a 5psi increase from the wet test. Then where's the other 5 or 6psi??? I don't know if you performed the wet test or if you had all the plugs out, but I guess you searching for that related post You have to verify timing if you are going to tune, and if you tune with a question on your mind, you're just like the rest of the cats in this game. __________________ LoverTechnologies "Half Broken Things!"

05-20-2016, 09:32 PM	#1
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	Strange compression result sr20det RWD 5-speed Had a very strange result on a friends car cylinder #1 through 4 dry test (no oil) 140 151 140 151 IS there something obvious causing this? I seem to recall seeing this before. engine is mostly stock redtop, but i know somebody changed the cams. something about valve seals? or maybe we need to degree his cam... __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er Last edited by Kingtal0n; 05-22-2016 at 06:33 PM..

05-21-2016, 07:55 PM	#3
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	Well. It is a friends car, he wants to go forward with the tuning despite the strange readings. I am not sure I can convince him to open the cover and degree the cams. I am still waiting for him to tell me if they did the valve seals while in there. I think we might need a leakdown test next step, but neither of us has an air compressor handy. Hmm. I do but in miami so... gota think about this. I just seem to recall from 5 years ago a similar thread, and they found something like this...

05-21-2016, 09:14 PM	#4
zombiewolf513 BANNED Join Date: Mar 2011 Location: AZ Age: 37 Posts: 1,682 Trader Rating: (6) Rides Gallery: zombiewolf513 Feedback Score: 6 reviews	Is that cylinder one through four, or four readings on one cylinder?

05-22-2016, 06:34 PM	#6
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	next time i see the car i will do the oil/ring test. I Dont think its the rings though. Very unlikely both cylinders have exactly 10psi worth of ring "loss" perfectly like that, its just very strange if that were true. I think it more likely that something with the valves/cams. and fwiw I never had any reason to degree wheel any camshaft in an sr20det before. Must have tuned 50 to 80 of these engines. It usually isn't an issue, you get a tomei cam, install a tomei cam, and go to town right away.