Alright guys, I'm confused... I've noticed some members of the board running with plenum, cats, exhaust and intake, and they're not running lean (e.g. exhaust tips still black - no ECU flash)

on the other hand, others are running w/ plenum and cats saying that they're running lean

So... what's going on?

I'd like to know what the limit of intake/exhaust mods are that I can do without needing an ECU reflash, while maintaining a safe AF ratio... can I add cats, plenum and y-pipe safely? or what about just cats and y-pipe?

 

I believe that the high flow cats or test pipes is what causes the lean condition. I would imaging that the addition of a plenum would increase the condition due to the increase of air volume.

 

I think the problem is more with the G's than the Z's. People are saying that the Z's have a more radical mapping system, and the G's just don't have the maps to add much more fuel. Could also be by release date or coupe vs. sedan. I ran kind of lean 13.5:1 with injen CAI, crawford plenum and stillen cat back exhaust.

 

With the mods I have in my sig, I am idling at 14.7-15.1 AFR. Cruising speeds are also within this range. When I am heavy on the throttle,my AFR will dip into the 11s. Someone told me that this was not really abnormal for a NA Z with my mods.

Zach

 

I have a nismo intake, dc headers and a borla true dual, my tips still turn black, I guess it's still on the rich side. No numbers to support this, it's just an observation. I think our ecu overcompensates which causes our mods to do very little.

 

When I purchased my Plenium from Crawford Z Doug told me that the additives for unleaded gas resulted in the black soot.

 

That is an excellent questions - I guess it depends on what "lean" is. I keep hearing numbers from 11 to 15 and saying its lean, its not lean, its a bit lean but OK, etc. etc. I am soooo confused....

What is the A/F ratio of a STOCK Z?

How much can it deviate from that without any negative short or long term consquences on the reliability/longevity of the engine? (I guess this question is a bit subjective)

 

I also have the black soot on the inside of my exhaust tips.

 

I personally would keep it under 12:1 A/F (low 11's to be safe) on NA, and under 11:0 FI. Of course "safe" is also a function of ignition timing.

Cruising and Idle you are in closed loop mode, where the computer constantly corrects for fueling, so 14.XX cruising and at idle is totally normally. Generally, under full throttle acceleration is where the most load occurs and where you need fueling to be on the richer side. Although if you are heavily modified it might be a good idea to keep an eye out on partial load fueling also

Cheers,

Gary
Gruppe-S

 

Under 12:1 for NA, I think your facts are incorrect. A good loaded a:f is 13:1-13.5:1, FI should be sub 12:1. This recommendation is beyond safe and borderlining saturating the engine and injectors with fuel. I agree 100% with your second statement.

 

Here's my AF ratio chart. Mods in my sig. I suspect the 04 ECU is doing something funky to keet the AF in that range, because with as many mods as I have I would expect to be leaner than that.

 

that is a GREAT looking AF ratio considering your mods

when you did the dyno, where was the O2 sensor placed?

 

Here is my A/F graphs from my eManage tuning runs. The Red line is my base (unaltered) A/F with all the performance mods in my signature. After some tuning I am now running 12.5 at WOT across the board (purple line).

 

nice - did you tune it yourself using your emanage? how difficult is that to install/tune?

 

Yes, I installed and tuned it myself. I do 3rd gear WOT runs and log my A/F with the Zeitronix Wideband, then export it to Excel and anaylize the data to figure out where the map needs modified.

It's kind of a beeotch to install it the way I did which was to crawl up under the dash and do all the soldering there. If I had it to do over again, I would have bought one of the new wiring harnesses that patch makes and then do all the wiring in the confort of my house, then just plug it in.

-Chris

 

Very cool. You mentioned that the red line is the base. What's the blue line?

 

Doh!!! Thanks for pointing that out, jjellyneck. The Blue line is the base. The Red line was my first run after making some changes to the fuel map. Obviously it wasn't right

 

I have as much black soot after Nismo cat-back & CAI as I did stock. Either the ECU is correcting it, or it really is gas additives. Right after the cat-back & CAI install, I noticed a flat spot around 4300 rpm, but this smoothed out later for the most part (ECU remapping itself?)

 

Hey Chris, I noticed something in your stat's I sure am interested in, if you would kindly oblidge. It's concerning the Kinetix plenum. I noticed your note about the low dyno gains due to a cracked plenum, yet I thought the cracking issue had been resolved with the v4's. I sure would like to know . . . waiting on one to ship right now.

Also: I read where someone - maybe it was you - talked about how this plenum made the car sound wicked under WOT, and also how there's no de-acceleration when letting off the throttle anymore. This sure sounds like a cracked plenum/air leak to me. Had a similar experience with a 300 Z.

 

It's all going to vary on your build date guys...there are several generations of Z ecu's and they each have unique mapping. Not only thatm but there can be differences between cars of similar build dates as well. base timing figured I've looked at have varied as much as 2-3 degress on cars we have looked at. Wont make any significant change at idle, but could mean a substantial difference in the upper rpm ranges

Adam