I've been reading about some people dynoing their cars after extensive mods and starting to get a lean condition going on their cars. What mods are the biggest threat to this? Is it after high flow cats or test pipes that the car starts running very lean? I'm going to be starting to mod the car, but I don't want to do something that may be very hazardous to it because I can't afford expensive ecu reflashes, downtime, and all that stuff. So I guess the question is.. is it ok to heavily mod a z n/a and not worry that it runs a bit leaner.. or is a ecu reflash mandatory after a certain point? Also, are cats/test pipes the primary cause of lean conditions.. and will they cause that even with little to no other mods?

Thanks in advance..

 

mine ran pretty lean after i installed all the bolt-on i/h/e, it was ~13.7-14.0 up till 5k rpms. not necessarily dangerous but it was retarding timing by the knock sensor. if you do cams i urge you to fix you a/f.

-this was done on a clayton dyno with an 02 style a/f using a stock o2 sensor location. i do not know if it was calibrated etc so others results may vary.

 

Wow.. did you do anything with your cats?

 

what cats? i have xerd long tubes that replaced them, i dont think it was the catless system that killed my a/f it was a combo of everything, you probably dont need to worry until you do a whole exhaust (head back)

btw i now use an safc2 to keep things in check

-alex30327 knows a lot about a/f might wanna give him a pm or search for some of his older posts

 

Oh so you got a safc2? Awesome.. How much did it cost to tune that thing? You have no problems making the settings stick? I'm only asking because a few people I knew that had celica's with tunes safc's in the past.. the settings reset after a while. No such problems with the z?

 

not that i know of, tuned it with a datalogger my friend borrowed from his shop which only read in karman but we made it work using its readings and the ones from the dyno. the settings are still in memory but i dont bother checking since all i did was add fuel. and its got a knock sensor on it and it never shows up any knock. car feels noticeably faster now.

 

cool man.. good to know. How much were you able to adjust the settings.. are the a/f setttings closer to stock again now?

 

its in the lower 13's not until above 4500 then it gets into the 12's. it goes all the way up to 50% +/- and it only required +5% at most so id say ive got lots of room to play with if i do more stuff. what mods do you have planned that you think will cause you to go lean? stock settings are really rich so i didnt quite go back to them completely, i was mostly worried about keeping it from pulling timing rather than getting it perfect. ill adjust it more when i get it dynoed again after my next batch of mods. oh and if you want to get it tuned just do it yourself while its on the dyno an safc is real easy to use and the dyno shop wanted 170/hr to tune it!

 

Oh wow.. ok good to know man. Well I already have an Intake (AEM), though I'm changing it to the JWT pop charger. Beyond that I'm looking for a plenum, y pipe, and either cats or test pipes very soon. Though the cats started concerning me because many people started saying they are getting too lean when they went with cats/test pipes..

 

Hey man,
Do you think i will run lean with:

1. Crawford cats
2. Crawford plenum
3. cat-back exhaust
4. jwt pop charger

Thanks?
Matt

 

I think I'm running pretty lean myself. Barely any residue on the exhaust after 1000+ miles of interstate driving, one road/track day, and 3 weeks without a wash... mods are in the sig.

 

We all talk about running lean but how does that affect the car. Sure it is not desireable for the engine life but does the situation in which you run lean actually take away a bit of the performance potential that the mods provide??

 

If run too lean then the ecu will retard timing causing you to lose power. I think the ideal a/f would be one where you're producing the most hp without causing the ecu to pull your timing.

 

hey guys sorry i was out for the weekend,

Do you think i will run lean with:

1. Crawford cats
2. Crawford plenum
3. cat-back exhaust
4. jwt pop charger

maybe i would say just pull your plugs to check if you think you are, or go to a dyno. its not likely that you are extremely lean though.


We all talk about running lean but how does that affect the car. Sure it is not desireable for the engine life but does the situation in which you run lean actually take away a bit of the performance potential that the mods provide??

it pulls timing like crazy, it doesnt hurt the engine much due to the knock sensor but its definitely not good. it takes away a lot of the performance potential the ecu will pull mad timing out and skew your hp numbers. when i dynoed with my mods listed i only got a max of 238 hp. i should be around 260. i noticed that the lines were extremely jumpy when the a/f was around 13.8-14.0 so i know it was pulling timing. then i tuned this sucka and i felt a big difference in performance.

 

So, if you had put in higher octane gas, would it have accomplished the same thing (as tuning) as a kind of band-aid?

 

not sure if the knock sensor pulls timing based on knock or a/f but it could work, i have 93 oct here btw