Red tint on the plugs and o2 sensor is caused by additives that they now use in gas.

 

A couple of things of note:

1- 14.7:1 is the stoichiometric air/fuel ratio, which is the ideal ratio for complete combustion. Personally, I'd like to be in the 12.5:1 range for FI application and 14:1 range for NA application. IIRC, many Nissan motors (at least older ones) were designed to run lean (i.e. over stoichiometric) in low rpms. Reason being, is that "light" detonation, although risky and dangerous, produces quite a bit of power.

2- I can't imagine how a freer flowing exhaust system would create a lean condition. Afterall, the engine is a 4-stroke motor and each piston follows this cycle: intake stroke (down stroke), compression stroke (up stroke), ignition/power stroke (down stroke), exhaust stroke (up stroke). It is possible that during the intake stroke, the exhaust valve remains open for just a hair (valve overlap), but as the piston moves down, it will suck both air and/or exhaust gas.

Michael.

 

I just had a brain fart! Doesn't the ECU in the Z constantly adjust the amount of fuel under specific conditions. Even if you put mods in your car, the ECU technically should not allow the car to run lean. Although I maybe completely wrong, I always thought that the ECU would adjust itself under many types of conditions to prevent lean conditions (not including forced induction).

In my opinion, no way cats, crawford plenum, CAI, or exhaust are going to lean out your fuel mixture enough to where the ECU cannot compensate for detonation.

 

Someone should Call Randon Tech or Nissan for their opinion. Maybe the Stock ECU can not accomodate all these mods to the car or maybe the cats burn so completely to results as sampled by an tail pipe external sensor will read lean.l

 

Thanks! I did not know this. This makes me feel better!

 

I love reading your extremely technical posts Michael-Dallas, I really wish you would post more. Like I said I am at 11.5 with headers and dual. The only thing I am changing is cats and I think I will be OK. Someone made a good comment about TS getting a better variety of setups to create a better variety of fuel maps and I couldn't agree more. Well know he has a Pro Charger map, a Crawford map, a P.E.TT map, he's getting there little by little and the car has only been out one year!

 

TS worked with Me for 3hours on a NA /RT Cat map and he has that now too.

 

It is certainly possible the high flow cat leaned you out a bit.....reason being is that the ecu is reponding to what the 02 sensor says it is seeing. If you install a totally decatted exhaust, the 02 will heat up faster and reach a higher peak temperature than it will if there is a standard cat in there. As such, the 02 heats up slower, and reaches a lower peak temp (since the stock cat is acting as a heat sink). However, I don't think that installing test pipes and a header is enough of an opening of the system so as to cause the car to run truly "lean"...just leaner than it does stock (which is generally a good thing). As stated, the factory ecu on this and every other car can adjust itself over a certain span for differences in temperature, humidity, altitude. This is done by Nissan (and every other manufacturer) to provide as consistent of a performance level as possible regardless of where in the country you are.

You absolutely do not want to run the car at 14.0:1 or anywhere near that in the upper rpm ranges (over 4k) at WOT..that is SCARY lean and you are creating lots of knock, timing retard, and the net result is preignition and detonation, not to mention lots of excess heat in the combustion chamber. hell, on race gas you don't even want to be tuning to 14:1. No amount of knock is good.....no amount of knock produces power. Quite the contrary..knock KILLS power, as the ecu immediately responds with a retardation of timing...and nothing kills power (not to mention torque) quicker than retarding timing on an NA motor.

Basically when tuning, you want to run as lean as you can (reduced emissions and better fuel economy), while still retaining 0 knock counts (thus the stock ecu gives max timing advance). I will be datalogging my car this weekend again, but I would suspect this range is going to be in the mid-high 12's at WOT in the upper rpm ranges. It's like this for just about every other NA car out there. This range gives you good consistent power (important), but is not so lean that one miffed tank of gas could be catastrophic (it happens, especially in winter time).

You guys in CA are at a distinct disadvantage here as you get basically tap water for gas, and ave warmer average temperature than we do in the East.....really reduces your margin for error and makes it more critical to run it a bit on the "fatter" side to stay safe. It also makes a HUGE difference where you are measuring the A/F ratio, and what you are measuring it with.....a reading taken from the muffler will be different than one taken at the test pipe or in the midpipe.

This is one of the primary reasons though that the ecu mods really need to be done on the car, and not via the mail. Everyone's car is different, like a fingerprint, and as such, the maps for 2 cars are rarely the same in all aspects.

For all we know at this point, there may even be more than one software revision for the factory ecu - we have seen this many times with Japanese cars (WRX's have quite a few different ecu's from the factory, even though they all are 100% physcially interchangeable).

Lastly, how TS or anyone else leans the car out or richens it up is important...if they are clamping MAF voltage (or offsetting it), they are also intrinsically changing the timing as well. If they are simply raising or lowering injector on time (IOT, as measured in milliseconds), then there may not be as dramatic of an effect in timing. Point being, yes as time goes on they will get better and better at mapping the ecu's..........though the real key to this is datalogging a very large sample of stock ecu's from various production dates, as well as various areas of the country...and the only way to do this is to datalog it on the subject car.

 

The reason why we have 2 pairs of cats is that the first pair heats up quickly for cold-start emissions. IIRC, catalytic converters need to heat up to a very high operating temperature in order to perform. If the cats were heat sinks and dissipated heat, then there's no guarantee that they'll ever reach operating temp and stay there. Therefore, if anything, I would think the opposite would occur -- the o2 sensors would heat up slower w/ the cats removed. And if the o2 sensor need to heat up to operating temp and stay at operating temp to perform, then this may cause the ecu to respond slower to a/f adjustment until the o2 heats up.

I know that the detonation sensor stops working at around 3500rpms for the VG motor. I do not know if it's the same for the VQ motor, but if it is, then you will gain power with detonation (consider that detonation increases cylinder temps and pressures) until the ecu adjusts for a/f ratio. Of course, motor longevity will be inversely proportional to the amount of detonation incurred.

If you can tune your motor (for NA application) for 14:1 under WOT and for all driving conditions, seasons, habits, etc., then you should be "golden."

Michael.

 

My RT's are installed. I love them and my guages read the same. They really make the Borla headers and true dual come alive. Highly reccomend RT and Performance Nissan both. Better clearance than I expected, better sound, and no smell like I have smelled before woth no cats. CARB certified too. My stock cat was bad on the driver side from my drive way abottoming out anyway, now I don't scrape anymore and no, I am not lean. Thanks for the education!

 

Hmm... I need to find a a big speed bump ,then maybe Ca. and my wife will let me replace 'em with RTs too.

 

12 sec Z I was just wondering your average fuel economy is on your car guages now. I guess 18's Im still at 20.4mpg in mixed street and freeway driving. The cats actually helped the fuel economy after the TS Re flash tune.

Guys the TS Ecu will pay for itself over the years in fuel economy alone. Not to mention the ego pleasure of the fuller sounding exhaust.....

 

My gas mileage also improved. I got 400 miles on a tank before refuel (all freeway) coming back from So Cal to Nor Cal but even around town it has improved. I don't have a precise number other than from 280-300 a tank to 340-400 a tank. It hasn't been long enough to really calculate but I will.

 

P.S. this was before the RT cats I wonder if it will improve even more?

 

Your engine will have more power when the RT cats are installed so then it wont have to work as hard to do the little acceleration burst's done before.

As far as gas mileage. How are you all figuring it? Not from the on board computer I hope.

Get gas, Fill it all the way up till it stops, drive, see mileage, go back to the same pump, same pump number, pump gas till it stops, devide number of gallons into miles driven. Thats your most accurate MPG figure you can get.

 

I just filled it up and then cleared out the trip meter and drove the tank, best I saw was 400 all highway.

 

I dont trust that gauge very much...

I have driven home with it saying 100 DTE on my whole 40 mile drive home from work.

:-/

 

Hmm yeah I suppose you are right, the DTE is calcualted by the computer but I don't think the trip odemeter is. I think the reserve tank is 2 gallons?

 

That is because it is measured in distance. The only way for it to do that is to base it on throttle postion, gearing, speed, etc. All variables. That doesn't make it a bad estimate. But it will constantly change based on what you are doing as a driver. If you floor it the number will go down dramatically. It is saying that you have 100 miles to go if you keep doing what you are doing at that moment. I think it is just fine.

 

yes I understand that, but, how often have you floored it and seen that number drop dramatically.

I havent... Ive seen it drop a few miles at most once...

Its not like the MPG needle on a beemer... (those are anoying)