this is a newbie Question, but who can tell me what exactly does running lean means?

 

it means that their is more air and not enough fuel in your combustion chambers. this means that the engine runs hotter than it should and runs the risk of detonation. this can cause an engine to fail prematurely. is caused by freeing up the exhaust, or increasing the amount of air coming into the engine. can be fixed via ecu, piggyback, or fuel related methods. anything you want me to elaborate on, i am currently running lean with the mods in my sig and will be tuning this weekend.

 

how do u know if ur running lean?
from the dyno?
thanks

 

You'd need to have some sort of gauge to measure Air/Fuel ratio or Exhaust Gas Temperatures. Yes, you can find out if you're running lean on a dyno because most have an Air Fuel ratio monitor.

 

ic, and on the above, he has mentioned that there is a risk of detonation. how big of % will that happened?
thanks

 

The percentage of risk depends on the severity of the leanness(Is that a word?)

If you could expound on why you're worried about it maybe we can give you a better idea of whether it's a problem for you.

 

i have the amuse Ti exhaust + Ti y-pipe, + test pipe.
and from the web, it says this setup will need a a/f ratio tuening .
cuz it is running lean!

 

Hmmm...my guess is that you should not be running too lean with those mods. I've seen guys with those kind of exhaust mods, plus intake and have not seen lean conditions. Not sure if the addition of the plenum would change that, but I think you should be fine. You can do a search and find lots of dynos with A/F ratios that have also been posted on this site.

 

i thought search function is down?

 

What he means is wander around this forum for days on end clicking on links hoping to find the information you need. Search is down, and I wouldn't worry about being lean with just the mods you have. IMO, those are minor mods and shouldn't nearly put you in a lean condition.

 

your fine. i ran with the exhaust intake test pipes for over 4 months. you dont need to worry about running lean until you get onto headers and intake manifolds. thats when you really start to push out a lot more air. if your worried that your running lean go buy some dyno time it will ease your fears and give you some numbers to compare with. itll be fun!

 

loli was worried cuz amuse official website states that the it is running lean !
but , ya...since it is not a major mod, shouldn't put my engine in any bad situation!

 

i am running the amuse exhaust setup with popcharger, and planning to get a carbon air scoope.!will that do any bads?
i saw injen on ur sigs?
or did u have the amuse b4 the injen?if so , why did u change it?

 

Yeah, damn. I just got fired from my job today because I spent the last 2 work days searching for lean dynos. Boss man didn't understand that I have mods to look after...hey, what's more important?

 

Detonation and pre-ignition go hand in hand w/ high temperature. High engine temp increases the chance of detonation and heat (from high cylinder pressure caused by detonation) is a by-product of detonation. Lather, rinse, repeat. It's a vicous cycle that once you're in, it's hard to get out.

The extra fuel in a rich a/f mixture is what keeps the cylinder "cool" (pun intended). This is conventional thinking.

That said, it's ok to run lean as long as cylinder temps are under control. Running rich unnecessarily will only increase emissions, decrease gas mileage, and wear out the o2 sensors and catalytic converters sooner. Not to mention if you run excessively rich, then you'll end up w/ carbon buildup. This same carbon buildup can quite possibly reach temperatures high enough that it glows. Thus, it is possible to encounter detonation (or pre-ignition) w/ an overly rich a/f mixture.

Personally, I have a feeling the VQ is designed to run a lean a/f. Consider:

1- the engine consists of an all aluminum block and head (which not only is lighter than cast-iron, but also dissipates heat quicker);

2- the 10.3:1 compression ratio isn't what I would consider high -- a Z32 VG30DE runs a 10.5:1 compression ratio and other comparable high performance sports cars have even higher compression ratios;

3- there are flavors of the VQ that are direct injection (i.e. VQ30DD, VQ25DD). They are "ultra-lean burn" motors w/ an a/f ratio as high as 25:1!

4- the cooling system in the VQ is a helluva masterpiece. It doesn't take forever for it to warm up like the VG30DE or SR20DE and I can't get the temp needle to budge from it's normal spot even when I'm flogging the **** out of the 350 at the roadcourse in triple digit Summer heat!

Michael.

 

pull a plug take a picture of it then post it here then we can all scrutinize it to death and determine if you are lean. Running a dyno wouldn't be wise if you thought you were lean because it goes WOT and would amplify the problem if indeed it exsists.

I read lots of web pages, I don't take them as the bottom line though.

They said "all RT cats run lean" too but it wasn't the case with my car and I pulled the plug and took a pic and uploaded it to prove it. This is the FI section you should post in the General Modification section for a broader response.

And no Jesse leanness isn't a word and you should get a strike for that. Is everyone de-roboting now I am always the last to know (is deroboting a word?)

 

No, deroboting isn't a word and yes I did it. BAN THIS FOOL I always liked Hobbes better than robots and my robot kept trying to take over my computer so I decided it was time he went.

 

You don't need to be at a 12.5 A/F ratio in the Z if you are N/A. Anywhere from from 13 to 14 under WOT is fine N/A. You r car will spend most of its life running between 14.7 and 15 A/F ratio.

 

and what makes you think its fine to run 13-14 safely at wot? every tuner i have ever spoken to says that ideal a/f for n/a is high 12 to a low 13. anything close to 14 is dangerous. yes the car will spend a lot of time around perfect stoich but that is not under wot it is only during normal cruising. there is a big difference between the two. i noticed when i dynoed that my a/f was at a 13.7-14.0 under 4k rpms then suddenly dropped very rapidly till bottoming out at 12.2 at redline. since then i dont even mash the gas more than i have to bc i like my engine in one piece.

 

Because almost all N/A cars run like this. This is how they keep gas miledge and emmisions down. You are right that 12.5 A/F ration is ideal for power, but that is not how the Z comes running from the factory. This would be considered too rich and running you car with 12.5 ratio all the way through the rpm range on a N/A car will shorten the life of your cats and O2 sensors. I should have been more clear in my previous post: 13 to 14 A/F ration is fine and is not dangerous till at about 5K rpm and above where you want to be heading to the 12's for sure. Now I agree that running your engine at 6200 RPM at wot and you have a 14 A/F ratio is definitely lean, but your engine is not going to instantly blow up or detonate. Running A/F ratios in the 13.0 to 14.0 range is perfectly normal even under WOT till you get up in the higher RPMs (5K+), then you definitely want it to be low 13's or high 12's. SO basically, I think that we are talking about the same thing, just not communicating it efficiently.

my 2 cents