As for engine mods, I currently have the z-tube/pc and am considering installation of aftermarket plenum and y-pipe. Should I be worried about running lean after install? Also, what are the harmful effects of running lean?

Thanks.

 

High flow Cats will make you run lean in the mid range. This can be corrected with a ECU re-flash by Technosquare. But, the ECU will adjust to normal Intake / Exhaust mods, no problem.

 

What about the lean condition with stock cats, a Pop charger and a high performance exhaust? That would seem to flow more air than just a cat change (at least it seems to generate more power).

 

Only HIGH Flow Cats will cause a lean condition at mid range. All other intake/exhaust mods will be adjusted by the ECU to add more fuel. Also, the lean condition at mid range isnt that dangerous (at mid RPMs), it's the high RPM range lean condition that is deadly.

 

Yes, cats will be the largest contributor to a lean condition. You should be fine with what you have.

When you start getting more mods you should seriously consider an ECU reflash by TS, or the other option would be to install a piggy-back fuel management system. The GReddy eManage and A'Pexi S-AFC II are the best choices, but personally I feel that the eManage is a better option due to more functionality and a lower price. However you either need a laptop to tune it or you have to buy the Profec unit which allows you to modify the A/F without a laptop. I recently installed the eManage and it's shweeet!!!

-Chris

 

below.

 

The only other mod I'm thinking of adding is a plenum, and I believe that the plenum evens out the airflow (leans the front 2 cylinders to be in par with the back 4) rather than leaning out each cylinder, in effect. But...I have been wrong at least couple of times before!

 

Well, the plenum actually will increase the airflow to the engine which in all likelyhood will add to the lean condition. Here's a picture of the A/F ratios from my stock dyno run (Blue) and my run with all the mods in my signiture (Red). You can see how much leaner I am with the cats and plenum. The green line on the chart is what I am shooting for when I start tuning my A/F with the eManage.



-Chris

 

Just thinking out loud...
I'm thinking that the plenum will increase the overall airflow into the engine, but nearly all of that additional air will be targeted to the front 2 cylinders. The back 4 will be essentially the same. If that's the case, then the A/F measurement will look leaner, but the only thing that's happening is that the front 2 cylinders have been brought up to the airflow level of the back 4. Therefore, there's no true lean condition per cylinder.

Of course this might be hosed up, wishful thinking. Maybe the only causes for a lean condition is your car are the cats, intake.

OK, so this has probably been beaten to death already.

 

So just to comfirm what I think I am reading here.

aftermarket Intake + aftermarket Exhaust + aftermarket plenum = no lean effect at all

 

Actually I'm thinking that aftermarket plenum = no A/F that is too lean per cylinder (Though it will lean out the front 2 cylinders to bring them into par with essentially the stock A/F of the back 4.)

Aftermarket intake, exhaust, cats, headers will lean out all cylinders to the extent that the stock ECU cannot adapt to the additional air.

 

I was just wondering, during a dyno the A/F ration is measured after the catalytic converters. Do cats not work at WOT? It would seem that if cats still function at WOT, hydrocarbons (ie fuel) would be removed before it gets measured so the A/F ration would show to be lean. Am I correct or not? Has anyone tried a wideband sensor before the cats?

 

I know of one guy who did. His wideband sensor consistently showed an A/F that was .5 to .9 richer than what the dyno exhaust sensor showed.
Anybody else?

 

Well I just installed a wideband o2 sensor on my G35 because when I wen't to the dyno my a/f mixture was way out of whack, and after going to 2 different dynos and getting 2 totally different results I needed to know what was up. I can say that the dyno was right and wrong, it was right I am runing way to lean but like the post above said the numbers were off atleast by .5

F.Y.I.
I have DC Headers, Nismo Intake, Helix Test Pipes
& Greddy exhaust.

I am at a point of questioning do I really wan't to keep messing with my car or just put it back to stock so I dont have to worry about blowing the motor in a 38k car (easier to handle when I had a civic). Even if I wanted an ECU I have a 04 and Technosquare doesnt have an ECU available for me so I might go with an Apex AFC.

 

I am at a point of questioning do I really wan't to keep messing with my car or just put it back to stock so I dont have to worry about blowing the motor in a 38k car (easier to handle when I had a civic). Even if I wanted an ECU I have a 04 and Technosquare doesnt have an ECU available for me so I might go with an Apex AFC. [/B][/QUOTE]

With your current mods, what kind of A/F are you running according to the new sensor you've installed?