I was just reading a post on the SFAC II. What is the benefit or need for having one? In addition to the mods below, my Cattman headers and Y pipe will be arriving shortly.

Thank you. I appreciate a little education.

Trex

 

2K2+ ECUs seem to run super rich when airflow is increased via mods. An AFC is used to tune your air/fuel ratio during WOT by conditioning the MAF voltage to the ECU.

 

FYI: the Y-pipe is just a part of headers. So you ordered Cattman headers...period.

 

yeah 2k2-2k3 maxima ECUS suck!!!!
-J

 

So, with the headers, y pipe, catback and my intake, Is this a necessity? Or will my car run fine without it? Is it difficult to install?

My mechanic just told me that when he did a Stillen header install it set off the check engine light and the guy had to get some device to fool the ECU?

This is like trying to translate chinese.....

 

Yeah, if you need me to break down the acronyms, 3-letter abbreviations, I will.

Your car will run normal during everyday cruising, however during heavy foot driving and WOT, most likely you'll be running pig rich which means wasting gas and more importantly horsepower. So, with an AFC you can in theory correct this to a point, however the VQ35 ECUs are pretty smart and so you may need to go with a TechnoSquare ECU and AFC combo to eek out every last horsepower.

Stillen headturds don't relocate the rear 02-sensors, so you need 02-simulators to trick the ECU into thinking your cats are still in place. Some have this issue with headers and some don't. MY recommendation is to relocated the two rear 02-sensors behind the main cat on your b-pipe vs. simulators. Jime has simulators incase you choose that route.

 

Icey2k1??

So if i get an SAFC-2 i will need a new ECU in order for the changes to stay put??

-J

 

Thanks...I'm assuming with the Cattman headers and ypipe i won't need to worry about problems relocating the sensors....

Can I buy and Apexi safc II like the ones I see on Ebay? It might be a good idea to install it at the same time I do the headers.

Trex

 

ok cattman headers incluse y-pipe... so its jsut cattman headers ( sorry thats jsut very annoying)

anyway 2k2s are cali spec and have 4 02 sensors......so teh other 2 have to either be relocated or you can do what i did and jsut buy a dual output 02 sensor simulator.....and just hook that up and ur in biusiness
-J

 

Did I mention my middle name is "Ignorant"?

The catback I purchased from SW is supposedly federal spec. Is that going to be a problem? where can I buy the sensor simulator?

and I still need the safc?

Trex

 

yeah that is a problem....all 2k2-2k3s are cali spec
-J

 

[QUOTE=TrexMax001]Did I mention my middle name is "Ignorant"?

The catback I purchased from SW is supposedly federal spec. Is that going to be a problem? where can I buy the sensor simulator?

and I still need the safc?

Dual output universal O2 sensor simulator

http://www.o2simulator.com/24803.html

Is this what your talking about?

SAFC 2 ?

http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

 

I'm not 100% sure. Jime and Studman seem to be working just fine with their AFC and eManage(similar method). Ask them.

TS just seems to have figured out how to straighten out the ECU on some of it's dirty tricks like closing the throttle-body and compensation factor.

I'd go for the AFC first, if you're not interested in a raised rev-limiter, but for all those mods, I'm sure you'll need TS's help.

 

i was thinking of buying a s-afc too would i have to take that to some mechanic to get that tuned even though i dont have any performance mods in yet.

 

what does safc mean? something air fuel controller?

 

glemax01 - Honestly, if you don't have any mods yet, you should spend your money on a y-pipe. Once you get a y-pipe(best-bang-for-buck), intake, and catback. Then maybe an AFC.

5 spd - Most of the time it's pseudo for the Apexi S-AFC(super air flow converter, IIRC). Most people don't realize there are other AFCs like the Fields, Split Second PSC1, base eManage, etc.. In the end, they are all pretty much black boxes that condition the MAF sensor voltage to the ECU to adjust the air-fuel ratio, ie an air fuel controller.

 

I sent Brian an email last night regarding the o2 sensors and the SAFC 2. Here is a portion of his response.

"The header only has ports for the 2 "before pre-cat" sensors because there's no point in screwing the 2 "after pre-cat" sensors into the header since they'd just throw a CEL. You can experiment with a O2 sensor simulator, but we advise extending the O2 sensor wires, welding 2 O2 ports into the exhaust B-pipe just behind the cat, and screwing them in back there so that you're sending your ECU "real" data.

[I]The business about airflow-enhancing mods making the VQ35DE too rich is the opposite of my observations. Our dyno experience (with fuel:air monitoring) with the VQ35 is that exhaust mods make them run a little leaner and CAIs tend to make them run quite a bit leaner (and obviously any dyno run is entirely at WOT). This business about needing the SAFC2 or anything like it to run the exhaust mods you bought doesn't seem credible.

The technosquare ECU upgrade may be a good thing, but I think the jury is still somewhat undecided on that. Besides, if the upgrade is doing what it should, an AFC should be unnecessary - I mean, the whole point of an ECU upgrade is to properly manage the fuel in coordination with other aspects of engine operation and external factors. I'm waiting for the Jim Wolf version."

Brian C Catts
Cattman Performance

 

Cattman took the better approach in my opinion then Stillen. The FSM does say the rear 02-sensors are used if primary 02s degrade/fail, so that would make me nervous running 02-simulators.

Cattmans' comment is based off his 3rd party dyno, I believe, which he's now no longer associated with because they were so unreliable. TS and several members here have shown rich dynos by adding mods from SEVERAL different dynos. I haven't seen anybody go more lean.

Since the Search is not playing nice, I'll just give an example and point to more.

Blubyu2k2 dyno w/HS headers, bpipe, stock muffler, GAB, and UDP. Red is withOUT the air filter. Both AFRs are too low for max power NA. If this is from a couple horsepower increase in airflow, think about what an I/H/E would do?


Here is the link to more dynos you can compare ESPECIALLY studmans' battle/comments on the stock ECUs compensation algorithm:
http://forums.maxima.org/showthread....7&page=1&pp=30

Also, here is TS's comment after over a hundred dyno pulls on a VQ35 350Z about the ECUs compensation measures:
Fuel Map Adjusted
Stock fuel was set to detune the top end horsepower. We discovered that the car runs extremely rich after 5000 rpm. Air to Fuel ratio (A/F) of 10.5 was found right before the stock rev limiter kicks in. Cleary, Nissan was trying to detune the power output at higher rpm to discourage the driver from hitting the rev limiter. For the performance enthusiasts, however, this is unsatisfactory, so we set the A/F to 12.5 all the way to redline to provide adequate power gain while still maintaining a safe margin.



Along with everyone else. JWT is using Techtoms MightyMap software bought from TechnoSquare to hack on the VQ35 ECU for their G35 TT project car.

 

To make a longer story short, you'll need to dyno to figure out if you need the S-AFC II. The S-AFC II (along with the original S-AFC, Greddy E-Manage, and a few others that Icy mentioned) are basic piggy-back units that sit in-line with the ECU.

The ECU as no knowledge of these units. They interpret the signals coming from the sensors and alter them. Once they are altered, they leave the piggy-back unit and continue down their path to the ECU.

As for the units and their optional modules, here's how they work (not all options are available for all units):

1) Air/Fuel - The common mis-conception here is that the fuel is adjusted. This is not the case. When an aftermarket unit adjusts the air/fuel ratio, what they are really doing is intercepting and adjusting the readings from the stock air meter (MAF). This makes it so that the car's ECU will think that more or less air is beind inducted into the engine, based upon the adjustments made. The unit relys on the car's ECU to adjust the air/fuel ratio. The stock ECU adjusts it based upon the pre-programmed air/fuel map that came from the factory. The aftermarket air/fuel unit basically lies to the stock ECU about the amount of air in order to get the ratio where you want it to be.

2) Fuel injection - Most fuel injection units only add fuel. They cannot subtract fuel (in most cases). To do this, they tap (but do not intercept) the wires going to each fuel injector. As the aftermarket unit monitors the stock ECU delivering fuel, it adds additional pulses (which the stock ECU uses) after the stock ECU has stopped. This results in the fuel injectors delivering additional fuel.

3) Ignition control - This depends heavily based upon the type of car and aftermarket unit, but here's the basics. The aftermarket unit intercepts the ignition signal from the ECU, manipulates it based upon your settings, then passes it on to the ignition coils. This can be used to advance or detard timing. In Maximas, it has not yet been proven (other than theory) that you can advance timing, but you can definitely retard timing.

4) Boost control - This varies even more heavily based upon the type of car, turbo/SC equipment, and the aftermarket unit. Usually this helps increase fuel delivery while decreasing timing, but there's alot more involved than just that.

While other units may offer more features, these are the most common uses for the aftermarket piggy-back units.

Now... the difference between the piggy-back units and the TS ECU is this.... TS modified the maps inside the ECU. Basically speaking, they took the stock ECU and changed it to reflect settings that the aftermarket unit would make. However, unlike the aftermarket unit, TS was able to fix a couple of problem items, such as the throttle body not opening 100% under WOT, etc. No current piggy-back unit that I know of has that capability.

There are pros and cons to both. The only true way to get the maximum power out of your car is to have both. But TS will tell you not to do the ECU until last. That is why I'd recommend that you install the aftermarket unit first. But before you even do that, dyno your car to see if you even need one. I'd hate to have you waste $300+ on a unit that you didn't need.

 

Thanks...this is all really good stuff. When I first started modding I didn't expect to ever get to the point of thinking about ECU mods. But now that I've commited to so much. i might as well keep going.

At what point does all of this modding affect reliabilty? My ride has to start every day and get me home on several hundred mile trips.

Does the TS ECU still allow me to take my car to the dealership and have them hook it up to the computer?

Thanks again.

Trex

 

The Cattman headers do not appear to be designed with O2 specific placement in mind. The reason the bungs are placed where they are is because they were designed for Fed Spec vehicles which only have two O2 sensors. ANyone who puts these headers on a Cali spec Maxima wil quickly find out that they have to extend the wires of the precat as well as the post-cat sensors. This issue could easily be solved by adding extra O2 bungs closer to the cylinder heads for easy placement of cali spec setups.


As for the A/F, each car is going to be different. Some will run leaner and some richer. The way the MAF is designed casues it to be innaccuate once changes are made in front of and aft of it. In my experience you really need to re-tune your AF in EVERY instance where you change the setup of your intake. And the SACF-2 is the easiest, most cost effective way to do this. I would only recommend the eManage for more experienced tuners who're striving to do more with their vehicles.

 

Ok here is my take on the S-AFC II.

I got mine to alter the a/f for nitrous. However I had it for a year before I got a wideband. No wideband, no way to tell your a/f so therefore it sat there idle. I am not a believer in Dyno widebands because they don't load the same as real life, therefore I do my adjustments at the track or occasionally on a quiet road.

Oh ya before I forget about the o2 sensor thing, I use the simulators because I don't have a cat otherwise I would just extend the wires.

I decided to use one setting on the s-afcII for N/A and one for nitrous. So I started with setting up the N/A and was very surprised at the amount of fuel I had to remove to get the to 13.2-13.4 which I use as a N/A base. Currently it ranges from -6% to -11% which I feel is quite a bit for a set of headers and an intake for mods. I wish I had of checked it stock.

However with nitrous its another story I actually have to add fuel to bring the readings to 11.8-12.0, not much, between 1 and 3%.

If I was just running N/A I would buy a s-afc knowing what I know now. It actually took 2/10ths off my 1/4 time. What would it do stock, I have no idea but it would be interesting to find out.

Does the ECU alter the settings after I adjust them? No, the a/f has remained constant since first setting a few month ago.

End of rambling.

PS Would I buy a TS ECU? Not until someone convinces me it will make my car quicker. I ran a 12.5 @ 108 last sunday on a 30 HP shot of nitrous with the stock ecu and run consistent 13.5's n/a. If someone does better than that on the mods I have then I will certainly consider it.