[BabyDiesel]

Originally Posted by Arragonis

I would still be careful, but you have the knowledge and the instruments so you should be fine

I most certainly will good sir! I'm proceeding slowly, trying to learn all I can, as fast as I can I do appreciate the positiveness and reassurance. It gets hard when your friends and family doesn't understand what and why you duct tape your car, and most seem to refuse to understand. My own mother called my getting gas at the same pump at the same place bull**** today even after explaining why I do that. It is a never-ending battle it seems. And to be told repeatedly that I need to focus on more important things other than fuel economy when I try to discuss achieving 75 mpg. I know I'm having a hard time getting a job fresh after graduating college and that a job is important! However, a useful hobby is good for the soul as an outlet, of sorts. That is a reason I love Ecomodder and the crazy things we all do, it provides a sense of accomplishment when other things in life go sour. And it is the right thing to do IMO.

Wow. Glad all that is out. Rant over gentlemen

I want to post what is known as the "Lean Burn Dissertation" by Tygen1. I found out a lot of useful info from him, and it seems fitting to take it from TeamZX2 and put it here

Heres the problem, I’m just not satisfied with tasting lean burn. Now I want to eat the whole thing, and get some desert! All that I've done has really allowed me to push the lean limit a little higher. However I have been studying up on how lean burn works and believe there is a lot of potential here. However it will take some investment to get there. There are two things that I believe will make crazy lean possible. Tuning and Turbo.

Let’s first establish how lean burn makes for better mpg, or at least establish what I believe to be how lean burn makes for better mpg. (I’ll probably look back on this and laugh at how little I understood) The epiphany came as I was watching the LOD on my Scan Gauge II increase by 5-10 percent every time I entered lean burn and then contemplating how this would look on the BSFC chart. It’s already well understood that lean burn greatly decreases power and you have to open the throttle more, this reduces pumping losses because if you need 12hp to run down the road, then you have to increase the throttle angle to increase power and maintain your speed/hp. So If we look at the BSFC chart for the Zetec:
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The dark line along the top of the chart is WOT Torque or 100% Load. This chart is read like a topographical map so the most efficient use of fuel occurs in the 245 zone. You can easily see that it is about 80-90 percent of maximum load between 1500 and 3000 rpm. More accurately we could aim at the middle of the zone, assuming that they did not map below 245, so we can presume that the absolute most efficient use of fuel occurs about 85% Load at 2250 RPM. It’s not reasonable to drive around at 85% Load because you’d have to be pulling a heavy load. So at 50-55mph I’m around a 45 LOD, as displayed on my Scan Gauge II, at 2000rpm. So that places me at the Red Spot on the chart. Enter Lean Burn and it jumps up to 55 LOD, that places me at the Yellow Spot.
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So you can clearly see that the engine is operating more efficiently. BSFC is how we express the efficiency of the motor and is calculated as: fuel consumption rate in grams per second divided by the power produced in watts: http://en.wikipedia.org/wiki/Brake_s...el_consumption or, Lean means less fuel being used to make the same power.
All this mumbo jumbo is making my brain hurt…So to sum it up, By leaning out the mixture, the engine is becoming more effcient. So if you lean it out further, you make it even more effcient…perhaps the 19.0:1 AFR could yeild an effciency near the Blue Dot?
Wow! That’s pretty incredible…if it is possible?

Please keep in mind that I fully understand that I am simplifying this concept, we don’t simply move up the chart, the chart would need to be re-ploted for each move, this effectivly expands the zones and opens up new ones as the engines effciency raises. Typically the BSFC charts are used by ecomodders to determine the correct load and rpm to accelerate under. So if you got an MTX ZETEC, then you’d want to open your throttle to about 75% (or 85% LOD) and shift just above 2250 rpm to get the most effcient use of fuel during acceleration. The hypermillers use this for Pulse And Glide (P&G) to get crazy mpg numbers…they accelerate up to 42mph then cut the engine and coast down to 18mph, restart and repeat and get 80+ mpg. I’m simply using this chart to get an idea of how changing parameters, changes effciency/mpg. Sooo, theroetically, if I were able to lean out the motor enough to move the load up to 85% at 2250rpm, I’d be getting the best possible mpg with a ZETEC….I have no idea how much mpg that would be, but I’d guess it would be a little more than 120mpg with an AFR near 30:1. Imagine running down the highway with your throttle almost wide open and you are only able to go 50mph on flat ground To give you some idea of how this relates, a fellow on Ecomodder has Aeromodded his first generation Honda Insight to the MAX. He is now able to get around 130mpg at 30-40mph. The Insight runs around 25:1 AFR’s, so this is relativily close to what I’m talking about. The Insight uses all sorts of Honda trickery to make 25:1 possible, our ZETEC’s do not have this trickery…

So how is it possible achieve a 19.0:1 AFR on our ZETEC? I’ve tried leaning mine out that much but it can only tolerate a LOD around 45, any higher and it starts to misfire. However I can push it up to 18.0:1 without misfiring, but loose so much power that the LOD goes up to over 70 when climbing a hill and this causes misfires. This is where Tuning and Turbo comes in. The charts above can be found in an MIT Thesis: Predicting the Behavior of Lean-Burn, Hydrogen Enhanced, Engine Concept by Ziga Ivanic, written in 2004: http://dspace.mit.edu/bitstream/hand...pdf?sequence=1 In this study he enhances lean burn on a ZETEC by using EGR and Hydrogen Gas. He also expirements with high compression ratios, turbos and superchargers. Combine that understanding with the work done by PGFPro on Gassavers: sons civic. He has created a Pre-Chamber “Torch Ignition” to ignite very lean mixtures and has done a little work without pre-chambers. Both his work and the MIT paper show how extra comprssion via Turbo/SuperCharger aid in lean burn operation. One theory I read says that the droplets of gasoline being pulled into the motor by vacuum have a more difficult time being atomized than when under positive pressure, even just a small amount of psi. Add this benefit with the negation of pumping losses and the improvement in volumeteric effciency and you are again moving the effciency zones on the chart out wider. How far is the real question? A while back I created a chart showing how, based on MAF output, going leaner benefited mpg. The chart is based on my observed MAF readings at 50mph, then using this formula: MPG = (AFR * 6.17 * 454 * VSS) / (3600 * MAF) I calculated the two lines shown.
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The Blue Line represents the heaviest load possible to maintain 50mph and the Purple line represents the lightest load possible to maintain 50 mph, we will use the purple line. At 14.7:1, the chart suggests that 65.5 mpg is possible, I have observed this at around a 40 LOD. At 16.5:1 we should see 73.5mpg, which I have observed at a 45 LOD. I’ve confirmed several points on this chart with my car. So at 19.0:1 we should see 84.6mpg, I don’t know what the LOD would be, becaue I can not get there, but If what I have read is true, then I should be able to make enough power at a 50 LOD to maintain this AFR and Speed.

So if the Turbo makes it possible to achieve these crazy mpg numbers, then why isn’t every Turbo Car getting crazy good mpg by running lean. Part of it is reducing the load on the motor enough to achieve a low enough load not to misfire and the other part is tuning to do this is not so easy. To make the load on the engine low enough you need to reduce your Aero Load, Road Load and Parasitic Load. I don’t have specifics on how these factors effect the overall load on the engine, but the general idea is that less is more. I would like to study this a bit more, but it is pretty complex. Basically, if I push it up to 19.0:1 and the load is too high causing misfires, then I need to reduce the load. Simple…right, maybe oversimplified? This may not even be a factor because the load for my car is pretty light already.

What would a turbo set up look like for this? I haven’t really nailed this down yet, but have a good idea what it might look like. PGFPro has suggested that only 1.5psi is needed to receive the benefit for lean burn, so a turbo capable of producing 1.5 psi at 2000 rpm is all that’s needed. Just that simple, no need for 30 psi at 8000 rpm. So it’s kinda difficult to figure out which turbos are capable of this because most maps don’t deal with this end of the spectrum, maybe someone more versed on this could give some input... So I am making some assumptions…perhaps the Garrett GT15 would be good, it’s on some similarly sized motors and makes this sort of psi at the rpm’s that I need. I have a TD04 that needs rebuilt, I’d hate to think that it’s too big I believe it will be appropriate if I can not find a GT15. I believe that I would keep the max boost to 4psi, so it would not need to be intercooled, which would greatly simplify the set up. I’d probably use the Focus exhaust manifold and weld on a T-3 flange…bla bla bla…I really need tuning before I can invest any more thought into this….so…

Now let’s talk about tuning. There are a few options out there: SCT Pro Racer Package, Sniper, Tweecer and Moates. There is also Mega Squirt which can be done as a Piggy Back or Stand Alone. They all have Pro’s and Con’s. SCT seems to be the most well developed and has the most support, but you are locked into one PCM and there seems to be issues with re-licencencing after a laptop dies and you gotta buy a whole new system if you want to change cars. Sniper is pretty close to SCT, but you can’t get a switch chip and support is not quite as good. Tweecer and Moates are pretty much open source type tuning and are not nearly as well developed as SCT or Sniper. Moates is a bit cheaper than Tweecer, but Tweecer has a switch chip available. Tweecer seems to be the best choice, at this moment, because you can change everything that SCT can, you can datalog and have the software suggest changes to the datalogs to smooth out iregularities, you can make live changes as you drive and the switch chip would allow some flexability I would like. So I am investing some time and effort in learning about this tuning stuff now, to see if it can get me where I want to go. If not, then Mega Squirt will be the only option left because you can tune and drive off a wideband.
The challenging part of tuning is that there are no known or established parameters for this lean of operation. The few folks that I’ve talked to or read about suggest ignition advanced well above 40 at cruise sometimes as high as 52 degrees!!! This is where live tuning and a switch chip will come in handy and why I am leaning towards Tweecer, and if I totally screw it up, I can just switch it back, on the fly, to the stock tune. I would have to be tuning in Open Loop as well, because this is an AFR that is well beyond the ability of the narrow band sensor. I would probably ditch the narrow band and just use the narrow band output of my LC-1 Wideband.

This is all exciting to dream about, but the reality is that I don’t have money to burn and the cost of living is going up way faster than my paycheck. Tweecer cost’s $450 plus you need some other software to make it more user freindly and that costs $130, so it would cost $580. It would take me nearly two years to pay that back with fuel savings. The Turbo setup I am estimating at $400, so I am way beyond the ROI on this stuff. Now it’s more about doing it than just purely saving money.
I’ll chip away at it over time and save a bit here and there and time will pass quickly

I'll correct the pictures at a later time. Need to put this here to remind myself!