s14 sr20 lean condition

[Kouks]

I have a s14 sr20 as previously stated. s15 spec r turbo(10 lbs.), Greddy FMIC/DP/3" Cat-Back, Free flowing Intake. 370cc stock injectors, stock MAF, stock computer.

Makes 250whp. My problem is between 2k and about 4k(basically just lower rpm), anywhere from half throttle to wot results in seriously lean condition ranging from 15:1 to 17:5 a/f ratio as seen on my wideband, as well as dyno sniffer that was just put into the exhaust, read the same thing as you can see...heres the dyno sheet for proof, as well as maybe some helpful insight...



It occasionally has a idle problem, holding various rpm to maintain a good idle, or upon decel might fall all the way to 500rpm and then bounce back to 1k. could be a different problem, i could see a vacuum leak causing both of these problems though, so it was worth noting....

What I want to know is where do I start looking for this problem...the a/f falls back down to around 11.5:1-12.0:1 closer to redline, so it doesnt seem to be starving for fuel up top, so why is it down low?

my compression was 125 warm across the board. going to check IC couplers in the morning for excessive cuts/holes etc...my vacuum lines are minimal, and a pretty clean thorough swap..I can check fuel pump voltage tomorrow as well...

Anyways, i could continue to stipulate various scenarios, my thoughts on this, but thats why im here, to here someone elses opinion, maybe someone sharing my dilemma, search didnt reveal anything prominent.

shoot!


Modified by Kouks at 7:43 PM 4/8/2010

[240_SeX]

Do you really have a bigger turbo, more boost, FMIC, exhaust with no tune?

On that turbo at 10psi you are likely testing the limits of the 370's and stock MAF.

It's running the leanest at mid range because that's where the turbo flows the most.

Please tell me yo at least have an SAFC.

[Kouks]

My car runs lean without even being in boost, and even idles too lean....this isnt the turbos fault.

o2 switches properly around stoic when maintaining speed/cruising but at idle any light throttle immediately runs to lean..

if you look at the dyno graph at 4500 when my turbo is pumping 10 lbs, the more and more the engine revs, the ecu adds fuel, and richens up the mixture.... maybe maxing out the injectors, but where max power is made, they are certainly still doing their job.

i will be adding tuning very soon, s-afc, and a nismo fpr, but if i have a vacuum leak, i doubt i can fully correct the issue.

[240_SeX]

If you had a vacuum leak it would became a boost leak under boost and would run rich, if its bad enough the car will buck.

A vacuum leak would however make it idle lean.

Has it always done this, or just since the mods?

[Kouks]

it has done this since i've owned it. i bought it from a friend, and im trying to make it right. this is my third 240, and he ran out of money/interest to keep going.

I recently bought the wideband, and had it dynoed to see what was going on with it. I am being very gentle on it right now, but i have to get this fixed.

It isnt loosing boost, and car goes like stink up top....maybe it just needs to have more fuel put towards it and see what happens. I am gonna hook up a nismo fpr, and s-afc to see if that will make a dent in the lean condition....

[240_SeX]

that's what i'd suggest.

If you suspect a vacuum leak, make a boost/vacuum leak tester.

zerothread?id=158784

[Kouks]

Thanks, I will be hooking up the s-afc tomorrow....i hope it helps, I am looking forward to being able to floor it down low, i drive like a super granda right now. Ordered my nismo FPR..

Vacuum reads 20-22 a idle, no signs of any leaks, i just think the computer isn mapping correctly.

I am going to try and build the tester too just in case, i have that saved to my computer...

Thanks for the help...