jameswwt

Hi Guys,
ive planned to go for a re-tune next monday and what should i do before the re-tune?
1) Boost Leak Test (As my friend told me its not necessary when im running on wastegate)?
2) The tuner has set my fuel pressure to 2.5bar and is it sufficient?
3) Currently im having a very lean issue and 4 of the plugs tip was whitish and will it bcos of faulty Plug cables, coils, Cam sensor?

Lastly, will running a GSC S2 cams will caused the car to run more leaner?

Thanks

211Ratsbud

iTrader: (1)

Firstly cams change the efficiency of the engine to another area. This means u could be hitting less refined areas of your timing and fuel maps.

Always boost leak test. You didn't tune for performance if you have a leak.

Base fuel pressure can depend on your individual car needs.

jameswwt

Thanks 211,
as what i got to know is my tuner has done a compression test and the reading is 12 bar but only cylinder no.3 is 11 bar...
Is it serious on the variation?

Lastly, i hope Greg and others kindly advise why during high rev 7,000rpm my car run lean and mis-fire?

Even til now my car knocks very regularly.
The knock shown from my pfc commander shows 30~75 ok know whenever i full throttle.

Will it be my Cam Sensor, 02 sensor, Coils or Air flow sensor problem.

211Ratsbud

iTrader: (1)

That is out of my area of peak knowledge . i know that there is a certain percentage a compression test across all cylinders would range in. I know a few PSI is acceptable, but at 1 bar difference, I am inclined to think you have an issue, and it is progressing due to the lean condition. The consistancy of your knock count does not sound good. I would do a leak down test to compliment your compression test.

As far as running lean, if your maf/honeycomb is contaminated, i would believe you to run more rich from that condition. If a MAF draws more voltage because the contaminants are acting like a sink, you would run closer to your higher load cells, which are generally more rich. (on a proper tune)

How severe is the mis fire? does the car studder? Bog? or are you determining this soley by your knock count? Exactly how lean does it go? 12.5?

My evo IX RS stock turbo with HKS 272's runs into a peak of 12.5ish in the 5-6000 range. i am waiting on a reflash adapter to fix this up. And the Idle is poopy.

Liqquid

Have you ever been tuned for the S2 cams yet?

240Z TwinTurbo

iTrader: (25)

2.5 bar is approximately 37psi and just to be clear base pressure is set by pulling the vacuum line off the regulator and referencing atmospheric pressure (0psi on gauge).

Understand that when the car is idling this will bring down fuel pressure so if you idle at 20in this will bring your fuel pressure to approximately (37psi - (20/28)*14.7= 26.5psi). So the real question is this, does the injector generate the appropriate spray pattern for proper idle at that pressure.

It has been many years since I looked at this, but from what I remember you want the injector to see at least 38psi to generate the proper spray pattern. On my old TwinTurbo 240Z I would set base pressure at 43psi and because of the porting and cam I think I idled at about 12in so my idle fuel pressure must have been something like (43psi - (12/28)*14.7 = 37psi).

So long story made short, contact the manufacturer of the injector and find out what minimum pressure is recommended to create the necessary spray pattern at idle. Keep in mind this is all rule of thumb and perhaps you can get away with running the lower pressure...I don't know.

UPDATE: As a reference, my car stock with Walbro has base pressure of 47.5psi (3.23 bar) and my buddies car with Walbro has a base pressure of 46psi (3.13 bar). With 18in on the boost gauge my fuel pressure is ~39psi.

R/TErnie

iTrader: (32)

compression test
leakdown test
boost leak test
Install fresh plugs that are properly gapped (should discuss with tuner)

come to dyno with the undertray off and the spark plug cover removed.

I would also advise cleaning your air filter and cleaning your MAF sensor using the proper sprays.

milford

iTrader: (18)

check for exhaust leaks and rattles.

jameswwt

Thanks you so much guys for your kind sharing.
Btw, what is a leak down test?

Will keep you guys update when i meet my mech & tuner later.

Dont know why the car was running so lean??? The plugs tip were soo whitish...

Have A Wonderful & Blessed New Year Ahead Guys...

My03evo

iTrader: (1)

I assume you got this figured out already but a vacuum leak will also make it run lean, if you do a boost leak test you will find any boost and vacuum leaks also.