Chip / Fuel Map tuning?

[Talos Woten]

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!

[Drifter]

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.

[oil pan 4]

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.

[Talos Woten]

Originally Posted by Drifter

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.

Most lean-burn tunes only target very light loads.

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.

[oil pan 4]

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.

[Talos Woten]

Originally Posted by oil pan 4

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.

[Isaac Zachary]

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.

[oil pan 4]

Originally Posted by Talos Woten

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

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.

[Isaac Zachary]

Originally Posted by oil pan 4

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".

[Talos Woten]

Originally Posted by Isaac Zachary

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.

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.

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.