Convert USA Corolla 7A-FE to lean burn?
 

I have a 97 corolla with the 7A-FE engine, and from my research the Toyota Carina (not sold in the US) had a lean burn version of the 7A-FE engine. Does anyone know a bit more about this being a possible "upgrade" for my engine in terms of FE.

From my little bit of research, I will need to buy parts overseas, which might kill the effect of trying to save money, or atleast having a fun project.

From my understanding the only differences in the engines are...

ECU
Head/intake/fuel rail
wide band O2 sensor
Pistons *might* be different, havn't confirmed yet


The only down side to this is that the better FE seems to be quite limited. I can get ~40mpg driving the car "normal", and according the Wiki, the Carina gets around 41mpg, but compaired to the us model, it rates at 31mpg (32 with manual trans). If it is a true 25% increase in mpg, I would be at 50mpg+ with a nearly unmodded car. Throw in a manual trans, areo mods etc and should be able to pull 70mpg I would think, if taken to the max.


My motive behind this is the fact my engine is getting high miles on it (242k) and from my research, typically they don't hit 300k before they use a ton of oil and starve the engine out of oil. So I will need to either replace or rebuild the engine, and this upgrade would be the prime time to do it.

Another thing I should note, I have no emision tests in my state, and my consern is more with MPG anyway.

You are getting pretty good MPG. Just take good care of the engine with an oil that has molybdenum, zinc in it and very little wear should occur as the miles add up. Body or transmission should wear out before engine does. But that is in general. If there is a manufacturing defect then that's different.

I don't think it's worth it to attempt to modify it for lean-burn. You probably couldn't pass emissions and the $$ probably wouldn't ever break even.

If you've got the space and mechanical know-how, you may want to consider getting a used engine and rebuilding it to the specs you want, that way when yours goes you've got one ready to swap in. That's exactly what I'm doing with mine.

You may also want to look into an Air/fuel converter. I'm currently running an apexi VAFC on my Acura and am in the process of programming a "lean burn" mode into it. The older models (for our older vehicles) can be readily found on eBay/forums for a third the cost of a new one.

You can bias the pump on the wideband o2 sensor to fool the ecu and run near 18:1 FAR.

I use mobile 1 synthetic, never really looked what is actually in it.


@nbleak21

My dad works on cars for a living, and I work on computers/printers for a living, so between us we can rebuild it etc. I'm also keeping an eye out for a wrecked low milage one since it would be cheaper.

@arcosine

I would love to learn more about forcing a lean burn, more research is needed :). 18:1 sounds almost too lean, but then again, I'm not sure what the hondas run at durning lean burn.

The Insight has been known to run up to 25:1. No amount of lean-ness is too lean. :) Its just the leaner you get the harder it is to get complete combustion because the fuel molecules are farther apart and the whole thing burns cooler.

When you say ONLY the head, intake, and possibly pistons changed, those are very major changes. Without them you will not be able to run anywhere as lean as the lean burn engine. Lean burn engines are designed to be able to cope with that cooler combustion by swirling the mixture up better so there aren't any lean/rich pockets in the chamber. This allows running the engine leaner than normal. I think it is around 16.5 or 17:1 is where you get peak NOx emissions, so you at least want to go beyond that so that NOx starts to come back down again. This is the stuff that causes acid rain, smog which causes lung cancer, and asthma as well as probably more junk that is pretty nasty.

That is pretty crazy how lean they can run. I havn't been able to spot very good sources to compair parts side by side, the only reasion the head is a must is because the injectors are mounted in the head instead of the intake tubes. I read a post that the pistons might be different, but no photos or any kind of confirmed details. I beleive the compression ratio is the same in both engines (9.5:1), just not sure if the head/pistons have a different design for the lean burn.

I read in other areas that lean burn takes out the cat over time. That could be a problem as well since I read mine has 2 cats, I have only noticed one though while not really looking for them.

It would be really neat if all I had to do is get the head (for the closer injectors / head design), ecu, and the wide band o2 sensor to make this work, but I have a feeling it is more complicated than that.

For cost effectiveness of the mod, if I go to rebuild the engine, the extra parts wouldn't be much more. Of course buying a low miles engine would probably be the cheapest way out, and cheap is good :).

Only danger with this is that the ECU "trims the fuel" (probably the wrong term) to 18:1, and then when it hits open loop, it'll drop that down to perhaps 14-15:1 and with the high temperatures you could destroy something.

Ideally the ECU should be reprogrammed. If there's no emissions testing, maybe you could look into a Megasquirt II system with wideband sensor...it's not that expensive, although it could take a while to recoup the cost.

I guess if you go with the fooling the ECU route, you can install a crude water/methanol injection system that is activated when you floor the throttle, to cool the engine down a little.

I just want to chip is as I actually own a lean burn Toyota and also someone who has swapped motors before. I have a 99 Corona Premio E with an automatic.

First off, I don't get anything near 50 mpg us. In fact, sadly to say I haven't even broken 40 yet. Personal best is 38.9 and I average around 33. Japan's fuel mileage rating system is worse than the EPA's by a mile. It bases cruise speeds at a MAXIMUM of 44 mph, so anything resembling freeway speeds that Americans are used to will decimate the fuel mileage.

Secondly, you can't just swap the intake manifold and ECU, you need at least the harness for the manifold and then need to pray that the wires themselves are not shielded in such a way that you can't splice it together. If that's the case, you'll need the entire harness for the engine (remember the J-spec ECU probably wont be able to interface with the US versions of the cooling fan relays, mass air flow sensor, coolant temp sensors, etc). So, at least you'd need all of the relevant sensors to go with the intake manifold, and likely all of the other sensors as well and the accompanying wiring harness as well. In short, it's not plug and play and from the actual fuel mileage standpoint, not worth it either.

Since you don't have emissions where you live, I'd just get a standalone ECU, rebuild the motor with a higher compression ratio, run it on premium, advance the timing and run it as lean as it'll go. I have a Nissan 180sx that I swapped a non turbo motor in from a 240sx and that's exactly what I did, except that I added a 3 inch radiator for cooling. The EPA rates the 240sx at 21 mpg and I am touching 30 at almost every fill up and have almost 170 horsepower at the wheels. Might be something to consider.

Good luck

I watched a video awhile back on Australian dudes who go to Japan, cut a car in half and jam the important end into a shipping container. It was for a drifter swap out of a Cressida or something. You could scour Australian or even Japanese Ebay, then get the front half of the car shipped, rebuild the engine and swap everything over. Very expensive, but you wouldn't miss anything. Then you could go all RHD on us and baffle tuner kids' minds.