Chip / Fuel Map tuning?
 

Howdy all!

Does anyone have any personal experience with chip or fuel map tuning? I came across this video:
https://www.youtube.com/watch?v=keGz_1BwcdQ
and from what I can gather they are reprogramming the ECU to change fuel / air mixtures in specific situations (i.e. speed and load). In this case, they significantly improved the fuel economy at highway speed, while leaving the low speed and high load performance the same.

This seems like a legit strategy. More google searching has found stuff by both performance enthusiasts (i.e. making the engine crank out more HP but worse FE) and conservationists (i.e. get better FE at cruising speed). In the latter case, chip tuning appears to be forcing cars into going into "lean burn" mode, even though the engines weren't originally designed or intended to do so. And lean burn has an established history of trading better fuel economy for worse emissions / wear on the cat.

Apparently this is much harder to do on hybrids because the chips are more sophisticated and harder to fool. But I've come across products to just replace the chip:
https://www.magnumtuning.com/en/deta...p/toyota/prius

Has anyone tried one of these? Once again, it seems like a legitimate way to improve fuel economy, but I would have a *lot* more confidence if someone on here has actually used such devices / done chip tuning / could relate their personal, firsthand experiences.

By the way, I've found other stuff that gets better mpg by feeding false information to / from the sensors... but I personally would avoid those even if they work. They do stuff like saying the engine is warmed up even though it isn't, etc. I'm leery of anything that falsifies sensor info, because I don't know what else is being calculated from the data. Tweaking the fuel map seems much safer in that it only changes the air/fuel mixture, and only in the regime(s) we want (say, cruising at highway speeds).

Thanks! :D

Disclaimer: I haven't done any tuning in nearly 20 years and aside from a little time tuning freeway fuel economy and around-town driveability, my main concern was making durable power for track days.

That said, ideally you want to adjust both air/fuel ratio & timing at every conceivable rpm & load combination. In practice, you had a hardware limit where you might be able to adjust the tuning at maybe 20 different rpm points and 20 different load points and you'd rely on the software to extrapolate between. And that was for relatively simple EFI cars from the 80s & 90s.

Today you'd probably also want to be able to tune the electric throttle body, EGR, valve timing/lift, etc. To get the most out of tuning it a bit leaner, you would probably adjust all of those other parameters until you were able to make the required horsepower at that particular rpm with the minimum amount of fuel.

Tricking the computer into thinking the O2 sensor is reading richer than it is (so it will lean the mixture) will affect these other parameters. Toyota leaves lots of margin for safety, but you would be eating into that margin blindly. You would also be shifting the afr readings across the entire operating range of the engine (at least while in closed loop feedback). Most lean-burn tunes only target very light loads.

To do what I did with 4bbl carburetor appears to require pretty advanced tuning capabilities.
If you want fuel economy on the low end with no sacrifice of power on the highend.

Howdy Drifter! I get that lots of things need to change in addition to the AFR. There's apparently a complex relationship between peak combustion, ignition timing, cam shaft angle, emissions mixture, and whether Jupiter's moons are ascending or descending. :) I'm not actually interested in learning or doing all that. I'm interested in getting a known reliable product of some sort that has done all that hard work for me.

I'm only interested in the lean burn under a light load, namely highway speeds. Champrius spends 75%+ of her time in cruise control at 65mph, so changing the fuel map / other parameters between 55mph and 75mph with peak efficiency at 65mph would be perfect.

To oil pan, I'm only interested in getting better fuel economy, and would actually be happy to *trade* HP / performance in order to get it. But it seems like most of the things I would get assume that performance is the priority, with mileage an afterthought. I haven't been able to find a dedicated "fuel economy" product, only "performance" chips.

Not really. I turned the carb only, I don't think I touched the timing and got a 20% mpg boost over a proper carb tune.
The only way to detune the top end is intentionally screw up the ignition timing which would just make it run less efficient or put in a smaller cam or use something like Rhoads hydraulic lifters that are extra leaky from the factory and make it seem like you have a smaller cam at idle for sure and slightly smaller below 2,000 to 2,500rpm then they pump up to full lift by 3,000rpm.

The 2009 Toyota Prius is a fuel injected vehicle. It doesn't have a carburetor.

I have done a carb and timing at the same time. I got a digital timing distributor for a 1972 Super Beetle and a bunch of jets. The idea was to get it to run lean at low loads and then rich at high loads. Then the timing is set to where it makes the most torque at each load (vacuum) and RPM combination without any pinging. Torque was hard to measure without a dynanometer, but some cones and a timer kind of worked. If it pings it's important to set the timing advance back at least a couple of degrees to prevent pinging. The results were I got right at 30 MPG average with mixed driving.

Yeah. If I can get a 20% boost with a carb you should be able to do much better with fuel injection if you can control it and blow way past 70mpg.

I don't know. For one, because fuel injection is already tuned. You can go leaner at the expense of more NOx, but other than that, you usually don't find some car with a fuel injection system that's all out of whack going way too rich and/or way too lean.

Also I don't believe there's a huge difference between fuel injection and carburetion in terms of fuel mileage or performance. You can be more accurate with fuel injection, but I don't see how you can get huge gains going from "already pretty close" to "almost dead on".

I'm okay with that tradeoff. I had a problem with my old cat going bad, which got blocked, then blew the seal to the engine. So I had to replace the whole assembly. I'm pretty certain even if I run a lean mix and ruin the cat... something else on the car is going to fail before the brand new cat does. :D

By the way, the stuff that I've read about stoichiometry always points out that what every car manufacturer does is a compromise. Because of emissions regulations the engines are tuned not for peak performance nor fuel economy, but a happy middle ground that gives sufficient amount of everything with minimal emissions. Just small tweaks richer or leaner can give significant power / mileage, but throws off the sweet spot of the three-way cats.

In any event, I'm already convinced of the reality of lean burn to reduce fuel economy. I am also confident that if I go to a tuning shop with a dyno and fork out $1,500 they'll get me at least +5% increase in mpg. What I'm not convinced of is whether I can buy an off the shelf product like a chip for $150 and get similar results. That's really what I'm asking about whether anyone has experience with.

How did the original catalyst die? Did it plug up with carbon, ash or did it melt?

Lean burn is the way.
The Honda vx series used lean burn in the 1980s and got hybrid mpg without the hybrid stuff. NOx is only bad where NOx is a problem. For about 99.9% of the land area of the lower 48 crank up the NOx and up the MPGs.
Fuel injected cars are tuned to run as close as possible to 14.7:1 that's were the lowest NOx and lowest HC are.
Peak torque is achieved with about 12.6:1 air fuel ratio.
Peak Horse power is achieved around 13.2:1 air fuel ratio.
Peak fuel economy is achieved with 15.4:1 air fuel ratio, leaner mixes are used to reduce isobaric losses.

You can drive the same distance on 16 to 18:1 air fuel mix no problem and burn that much less fuel.

Historically Toyota ECUs were nearly impossible to crack which meant aftermarket tuners could not rewrite fuel & ignition maps without changing to a standalone. From a cursory search, it looks like today some Toyota ECUs have been cracked, but I'm not seeing the Prius listed anywhere.

The problem with $150-$500 piggyback tuners is that they're almost universally against the law (they affect emissions in violation of the Clean Air Act). The EPA fined Bullydog $300,000 and forced them to perform millions of dollars in remediation. So there is a pretty big disincentive for capable people to make such tuners.

Of course, there are millions of people who want more horsepower and hundreds of thousands of them are willing to pay a fair bit for small gains so there is still a big carrot motivating tuners. And they can somewhat plausibly claim that their tunes are meant for off-highway use on race tracks.

There aren't a whole lot of people willing to pay a lot more for small mpg gains and tuners can't exactly claim that highway fuel economy tunes are meant for off-highway use.

Prius chat has a few DIY circuit modifications to fool the ecu into thinking it has warmed up sooner, but I don't know of any that attempt lean-burn. If I were going to attempt it myself, trying to shift the O2 sensor's output to a richer reading would probably be my first attempt. But I'd want to monitor everything else to make sure it isn't causing problems and I'd want it to turn off automatically at moderate and high loads.

No sooner do I post that then I find this article from Julian Edgar about tricking ECUs out of closed loop for tuning. But this was for a gen1 prius with narrowband O2s (I presume Gen2 uses wideband):


https://www.autospeed.com/cms/a_2388/article

Haha. The law. It's not like the prius is going to roll coal.

The Prius line is notorious for burning oil. They burn 1 qt of oil per 10k miles when new, and it isn't officially considered a "problem" until it's burning 1 qt of oil per 2k miles. On my 240k miles car, it had eventually just burned enough oil to gunk up the cat. The mechanic actually cut it open and showed it to me... it was basically one continuous black carbon mess. You couldn't see any mesh, honeycomb, or even the side walls. It constricted airflow so badly it blew out the seal to the exhaust manifold.

So I replaced the cat, seal, etc. and installed an oil catch can. It still loses oil at ridiculous rates... but it's no longer burning all of it. I just dump it out of the catch can every oil change.

By the way, I think every car should have an oil catch can. An unexpected benefit is that it also catches a bunch of grit that makes it past the air filter, and metal shavings that comes from (gulp) places I don't even want to think about. Even if that would come out each oil change, it has to be better to catch it early so it doesn't recirculate in the engine itself.

That sux. Yeah the only thing that's going to fix your converter problem is a hammer drill.
Luckily it blew the exhaust manifold seal and not a head gasket or burned valves.
There's likely still a concerning amount of oil going out the exhaust.

Simultaneous Failgasm
 

I agree. The fundamental problem wasn't fixed, merely forestalled. We can even ballpark when it should crop up again. It took 240k miles for the first cat to fail. Integrating my rate of oil loss, if it all burned then I should expect the new one to fail in around 80k miles. But the oil catch can has significantly reduced the burnt fraction, I'd say by at least half. So I'm probably looking at another failure in 160k-ish miles.

I'm 40k miles into the new one, and looking at another 120k miles before I expect another cat problem. Realistically, the rest of the car may not survive that long. I'm already seeing the harbingers of other major problems (radiator, timing chain, transmission, etc.) So there's a good chance something else is going to catastrophically fail before the cat does. I mean... the optimal scenario is to try to get them to all fail at the same time, right? :p

How often are you changing oil? How much are you burning between changes?

As you noted, Toyota low-tension rings sometimes get clogged with carbon and start burning oil. Additives and flushes can do a decent job of freeing up sticking rings, but if the oil return holes in the piston get clogged they pretty much have to be cleaned out mechanically (brush/pin vs chemical solvents).


Here is the piston from a 270K mile Highlander hybrid that still had pretty good cylinder crosshatching but showed signs of burning oil. This was taken after the piston & cylinder were soaked in WD40 overnight:
https://ecomodder.com/forum/attachme...2&d=1655360836

This next photo was taken after the piston was soaked in a jar of Kerosene overnight and then in jar of Simple Green the night after that. I also spent a few minutes brushing the ring lands with an old toothbrush before starting to use the old ring to scrape the carbon:
https://ecomodder.com/forum/attachme...1&d=1655720195

^Note that the oil return hole is still plugged even after I used a ring to scrape the carbon from that section of the ring land. Ultimately I had to use a needle to poke a hole through the carbon and then use a tiny pipe cleaner to brush away the remnants. Here is a picture from the underside of the piston of the oil return hole as it neared the end of the cleaning:
https://ecomodder.com/forum/attachme...1&d=1655720213

That engine had 4 holes per piston, 3 of which were 100% blocked. The 4th was partially blocked, but appeared to respond favorably to flushes/solvent soaks so I think there is some hope if you act before the oil burning gets too bad.

Excelent post! I have the same problem with my Prius and am not looking forward to it. First I want to scope the cylinder walls to see if there's anything left to save. Then it's either pull it apart like in this post or look for another engine.

I drilled additional oil return holes in the Pistons for my 6.5L diesel engine. The old 6.2L diesel had 8 holes and the 6.5 had 4. So I made more.

I use synthetic and change oil every 10k miles. When I first got the vehicle it burned 1 qt every 6-7k miles. That steadily increased until it was around 1 qt every 2-3k miles, then the cat blew. I check my oil every gas fillup now, and top off as needed.

I did a bunch of things to try to combat the oil burning. I did an engine flush and holey hell did it pour out black. The car stunk for weeks after that. Then I did a full cleaning of the air intake, MAF, throttle body, and tops of the cylinders. As mentioned I also installed an oil catch can, and by taking the difference of what I put in vs what I pour out I can get an estimate of how much its burning. It's still losing 1 qt every 2-3k miles, but I think it's only burning at a rate of 1 per 5k miles.

This last oil change I used Lucas Stop Leak and it worked for the first 7k miles (i.e. it halved the rate of oil loss) but then went back losing 1qt per 2-3k miles. So I could theoretically slow my oil loss / burn by using Stop Leak and changing oil every 7k miles.

I only use Top Tier gas and have considered using some kind of detergent like Sea Foam. Anyone have experience with that?

By the way, I have yet to dismantle the engine, and want to avoid doing so if at all possible. I've read nightmares in Prius Chat about the FIPG (Formed In Place Gasket) and how it takes a lot of practice to get it right. I'd have no worries about disassembly if it just used normal gaskets.

If I did take it apart, I could make some major preventative repairs. I'm certain the timing chain tensioner is getting loose, which means the timing chain is going. So I could replace all that. I could do a thorough cleaning of any oil deposits lurking about, and possibly replace some gaskets depending. I've put replacing the water pump and timing chain tensioner on the list of things to do, assuming Champrius survives her latest repair.

Abandon hope, all ye who enter here. :D

I thought the 1NZs didn't burn oil as badly as ZZ/AZ engines? 1qt per 2k miles is pretty low IMO, my 1ZZ-FE burned 2 qt in 2000 miles :P (cat was basically gone at 140k miles when the engine blew)

I wouldn't put Seafoam in the crankcase if that's what you asked, it has a lot of isopropanol. I don't think any fuel additive will help you because you probably have stuck rings. Some people use AutoRX or Marvel Mystery Oil but those really are not much different from kerosene (they have Stoddard solvent). If your engine is on its way out, maybe it's worth lightly running the engine with a little kerosene in the oil, or AutoRX (I think it has some additives that make it less bad than just thinning out oil).