Wideband O2 calibration

According to the manufacturer, the operating range of the NGK AFX is an AFR of 9.0 to 16.0 (0 to 5V linear).

So based on the manufacturer, the transfer function should be:

AFR = Vactual/((Vmax-Vmin)/(AFRmax - AFRmin)) + AFRmin

AFR = V/.714 + 9

To start with, I plugged in a transfer function that I found in the HPTuners forum posted by DStreck.  Sadly, without re-reading the post that I got it from, I do not know how he derived this value...I'll have to dig that up

V/0.709 + 9.068

The more that I think about this, since I am using AFR % error to do all tuning, it would make a lot of sense to calibrate my wideband to match the narrow band O2 sensors on the car since they're designed to be extremely accurate at stoich.  Currently, I have followed the manufacturer's directions and calibrated the wideband against open air, which should be accurate, but wouldnt it make more sense to have the calibration be relative to the car itself since the sensors present on the car will dictate the fueling correction when the car is in closed loop?

The manufacturer also assumes that Stoich is 14.57AFR.  Stoich is 1Lambda regardless of fuel type, and the sensor really reads deviation from Stoich, so wouldn't the display show 14.57 if you were running a different fuel at stoich, even though its true stoich AFR value is significantly different?  If this is the case, then converting from registered and commanded AFR to registered and commanded Stoich, would be a much simpler way to look at the %error without having to worry about differences in fuel octane, fuel type, etc.

For a lambda calculation, the manufacturer says that the unit operates between .62 and 1.10 lambda
Lambda = Vactual/((Vmax-Vmin)/(LambdaMax - LambdaMin)) + LambdaMin
Lambda = V/10.4167 + .62

...i'll add more to this post when i get time

Good reading

I picked up both of Greg Banish's books from Amazon.com.  I am about half way through reading Engine Management: Advanced Tuning and it has been great.  So far, we have covered a lot of the "why".  How engines work.  What all of the relevant terms mean.  The fact that, at its core, the PCM simply tries to guesstimate what mass of air is entering the engine so that it can add the appropriate amount of fuel to hit a commanded AFR.  So much "mystery" vanishes when you look at the core function of a product....inputs and outputs.

I am also spending a lot of time reading:
HPTuners forum
EFI Live forum (I do not own the product, but the theory is identical, so its good reading)

I have also read through Marcin's blog which covers some great topics from a mathematical modelling perspective trying to figure out exactly how something works.

How I love running wire...

Last night I worked on getting my NGK AFX Wideband O2 kit installed. I have an appointment later today to have a bung welded into the exhaust for the sensor, so I wanted to have everything else taken care of ahead of time that way I can get it installed and not have to get the car up on ramps to take care of the sensor installation at home.

I did some digging online and found that there is an unused switched spot in the fusebox behind the passenger footwell kickplate...I never even knew that was there! Pull back the floor mat, and the plate just pops right off. Very cool. I wound up going to CarQuest to get something that fits over a fuse lead that allows you to add a circuit without having to do any cutting on the car's stock wiring.

I never found a good writeup on where to find a good ground location. I had just about resigned myself to running the ground wire into the engine compartment and grounding it near the battery, but with having that fuse block and the BCM right there, I knew that there had to be a ground terminal nearby. I pulled off the plastic door sill trim piece and found it. There is a pretty hefty connector bolted to the frame that has around 8 ground wires all going to it. I figured that was a safe bet ;o)

To get the O2 harness into the engine compartment, I took pictures and then took the pins out of the connector. With the battery out of the car, I just pulled the electrical tape off of the large wiring harness that passes into the passenger compartment. A foot of electrical tape, a snake, and a little cursing later, I had the wiring harness pulled through. I reconnected everything, reinstalled the battery, and put the O2 sensor harness connector back together. I hung the harness from the corner of the hood and plugged in the sensor so that I could do the "free air calibration".

It came right up and the calibration was easy. I left it hanging/on for 30 minutes to ensure that the calibration was accurate.

After the bung/O2 sensor installation today, all I need to do is pull the extra harness back into the passenger compartment, button up the fuse box, figure out where to mount the AFX's display box (probably the biggest thing...its fugly, so I am tempted to mount it in the glove box...realistically I will just be using it for data logging, so once I have HP Tuners configured to match the displayed AFR on the AFX box (tongue twister?), I shouldn't need to have the box out and visible.

The only other thing that I want to do before I consider this wideband O2 and HPTuners installation complete (other than the tuning, of course), is detach the ODBII port from the stock location and do a semi-permanent installation of the HP Tuner's ODBII cable that runs to the glove box...I want everything out of the way and not visible. I can't say that I am a fan of doing data logging while driving with the ODBII cable dangling between my knees.

My poor dog, Wesley probably felt abandoned last night. His 'Mom' is out of town and I was down in the garage for several hours. I'll make it up to him later this week once I have this out of the way :)

Sore hands? Check. Upset pet? Check. Magically functional car voodoo? Check.

Feels like a real car project to me.

Scratch that two step idea

After some more reading, it looks like the two step idea is a bust...something about the computer triggering the rev limiter every time you hit the clutch, which is bad juju for...you know...shifting...

HPTuners arrived!

HPTuners arrived on Friday. I had waited until Friday for my paycheck to place my order for the wideband O2 sensor, but I thought that I could get a start on it before that arrives. I had found a particularly good writeup on how to get a good base tune (ve tables and maf). I downloaded the current, stock, tune from my car and dived right in. I got all of the way through configuring it to run SD (speed density...basically it turns off the MAF sensor and does all of its fueling calculations based on the MAP sensor reading) only to realize that I truly had to have that wideband O2 sensor in order to move forward with the writeup.

Crap.

Ok, back to reading through the HPTuners forums to see what nuggets of information I could find.

One thing that sounded interesting was the ability to essentially create a software 2-step for manual transmission cars. Once I get through my base tuning I may revisit that since it would probably be a lot of fun :)

I also looked through all of the things that I could adjust. I set it up so that the fans would run after I shut the car off if the temperature was high enough to have the fans running in the first place. I disabled CAGS (computer aided gear selection) in the computer, so I can remove the hack/fix pigtail that I had installed right after purchasing the car. I also raised Maximum Net Engine Torque to it's maximum value (640ftlbs). I don't think that the last one will affect me much since I am at a relatively stock power level, but it seemed like a good idea at the time.

Now I'm going to go flash it to the car's PCM, set up black box logging (so that I don't have to have my laptop with me all the time) and do a little driving before I go to the gym.

HPTuners vs EFI Live

So I knew that I needed to buy a tuning app. I knew that I wanted to do it right this time and have a wideband 02 sensor connected to it so that I could really dial everything in properly. The two big players for tuning hardware/software for my car are HPTuners and EFI Live. I would have to get the "pro" version of either one in order to use a wideband O2, so naturally the price point jumped. EFI Live is significantly more expensive than HPTuners. I wanted to go with EFI Live, however due to a few features that I liked about it, but I just couldn't justify the cost. Also, it feels like there is a larger user base and more forum support for HPTuners, so I placed my order.

I want to use the blog as a way of keeping track of the things that i notice, learn from, etc as I learn how to properly tune my car.

There are a few places that sell literature and offer classes on how to tune, but they're all pretty pricey and I would rather do the research and learn it on my own...although I may break down and buy a generic book if I cant manage to make it on my own ;o)

A little automotive history...

So a little history...I picked up my 2004 Corvette Z06 last March. I love the look, I love the feel...its just a great car, especially for the money.

I dumped a LOT of money into my old Buick Regal (supercharger kit, cam, fuel injectors, PCM programming software/hardware, torque converter, 2 transmissions, 1 engine, pushrods, etc.). I definitely learned a about cars and what makes them go vroom. I made a few good friends in the process. I also managed to blow up my transmission twice and then grenade a piston...so that was the end of modding that vehicle. I couldn't afford to fix it all when the engine let loose, so I sold off my aftermarket parts to buy a new longblock.

In the process of having my car down for a couple of weeks, I decided the responsible thing to do was get a second vehicle that I wouldn't want to modify. The Buick made a bit over 300hp at the wheels, so, naturally, getting a LS1 Camaro was the sensible thing to do...they make more power and the power curve is much wider. So that's exactly what I did. I picked up a Black 2000 Camaro Z28 for cheapish and managed to wrap it around a power pole before my 30 day tags had expired. I replaced that with a Black 2001 Camaro SS a short time later.

Now, the idea was that I would have a "powerful" car so I wouldn't have the itch to modify it. Well, that lasted maybe a year. Diving headfirst into doing some engine work is a great way to make a car powerful enough that it starts breaking everything else, unless you do the right supporting modifications first. In the case of these cars, the normal order was to replace the rear end/differential, transmission, and then start in on the engine. Since I was still paying off my Buick bill, I skipped that route and went with suspension mods at first. I put on a pair of Sam Strano's sway bars and a set of Koni single adjustible shocks. That made all the difference in the world...that car handled amazingly well. That lasted for a while and then I had the itch again so I gutted the interior of the car, wrapped the entire thing in Dynamat Xtreme, and put in a pretty substantial stereo (which I still miss). That was great for a while again and then I got a great deal on some chromed Z06 wheels, so, next thing I know I've done wheels, tinted all of the taillights/sidemarkers, customized the front bumper, replaced all of the badging on the car with mirror polished stainless steel, etc...

Then, shortly before paying the Camaro off, the AC died. It also was to the point where it needed a clutch. The Buick needed AC work as well. It also had a number of other "quirks". Looking at a 5k+ repair bill for both vehicles, I traded them both in for my current car. I picked up a Millennium Yellow 2004 Corvette Z06.

Damn that is a nice car. It has a fair amount of power. It drives like its on rails. The fit and feel of it are just head and shoulders ahead of everything else that I had driven to that point. I had test driven a C6 before buying the C5Z06. It was definitely a nice car. The interior finish was better. The one that I test drove had an LS3 in it, so it had a bit more pep, but I just didnt like the driving experience as much. It felt like a bigger car because you feel like youre a 5 year old sitting at the big kids table.

This one had it all...great power, great handling, respectable sound system (not great, but sound equipment is heavy, defeating the purpose of driving a lightweight sportscar)...so after a few cosmetic items (lettering fillins for the front and rear bumpers, a partition divider, etc), I called the car "done".

...until I found a used (500 miles) Vararam intake and air bridge set up for dirt cheap. Cheap enough that I could sell off the Blackwing intake that came on the car and only be out $50 (never mind the fact that the Blackwing is still sitting in a box at my apartment because the Vararam fits so "well" that I wasnt sure if I was going to keep it).

The Vararam installation was a bit of a pain in the ass. The fit was borderline unacceptable, but I managed to get it in there with only the minimum of cussing and busted knuckles. It had a noticeable improvement in power, especially when driving at highway speeds. The downside (another one anyway), is that I started to get a lean condition check engine light pretty consistently. I had read that this was a possibility before purchasing it. At first I thought that a few driving cycles would make it go away, but that didn't happen. I pulled out the bridge, maf and couplers checked it over, but I had performed the installation correctly. I put everything back in the car and tightened the band clamps down pretty tight. I doublechecked those 2 days later and they were still good.

I had found a procedure for making the computer relearn the expected air flow online one day, so I went through that and it was good for 2 days before the check engine light came back. Then I bought one of the MAF honeycombs from Halltech, which supposedly addresses this, but it was great for a couple of days before the SES light went off again. I knew that I really needed to tune it. I didn't want to shell out the money for it, but I knew that tuning was the "right" answer for my problem....