Increasing EGR flow for better mileage

[Christ]

Originally Posted by MetroMPG

Well, another option might be feeding the exhaust into the intake tract, upstream of the throttle.

Though that might mess things up because of the intake air temp (IAT) sensor ...

The IAT is usually a nominal distance from the TB... one of the "spare" vacuum lines on the TB could be used to "pull" exhaust gasses from the exhaust for a less technical approach... more vacuum = more exhaust pulled.

[moonmonkey]

would extra egr flow be helpful in an engine that has vvti (toyota echo 1.5) i read in another forum where they said it was different methods of achiving the same thing, (the extra egr flow compared to (varible valve timing) . i dont understand them being the same, as was suggested.

[Christ]

Originally Posted by moonmonkey

would extra egr flow be helpful in an engine that has vvti (toyota echo 1.5) i read in another forum where they said it was different methods of achiving the same thing, (the extra egr flow compared to (varible valve timing) . i dont understand them being the same, as was suggested.

The ECM has the ability to close the intake valves early if it feels like it, or leave them open longer, to allow the engine to have lowered dynamic displacement.

Usually, they leave the valve open longer. The piston starts on compression stroke, and pushes some of that air back out into the plenum, so another cylinder on intake can use it.

The EGR flow accomplishes the same thing, only using a different method, by reintroducing spent gasses (which are mostly inert at this point) into the combustion cycle, allowing for less fresh air and fuel.

[Daox]

Originally Posted by tasdrouille

Won't your MAP think more air just went in and the ECU would adjust the fueling accordingly? Your o2 sensor would pick it up though, setting the record straight trimming the fuel, but maybe that would throw a MAP fault code.

That is quite possible. We'll just have to see if it does or not. I have no idea how much fuel trim I have available to play with.

Originally Posted by tasdrouille

Here's an interesting article on EGR control strategies.

Good article. Its good to see the OEMs are using EGR the same way I am thinking of using it. It just makes me wonder how much headroom I have to play with before I start running into problems.

Obviously, I'll be a bit more aggressive with using EGR than they are. However, I still see myself running into the same two limits as I posted earlier in the thread:
1) EGR diluting the mixture so much that it causes misfires.
2) EGR making the intake too hot and causing pinging.

#2 is being addressed by using the EGR cooler though. So, I think #1 is going to be the main problem.

[RH77]

Originally Posted by Daox

#2 is being addressed by using the EGR cooler though. So, I think #1 is going to be the main problem.

Would a higher-octane fuel help with the detonation (or be cost-effective)? I run 91 octane with the higher coolant / IA temps, and advanced timing -- usually 20/cents more per gallon can be a good investment.

(I'm still trying to figure out if the Integra has an EGR valve -- the shop manual is contradictory).

Great research so far -- I look forward to more results

RH77

[Daox]

Thats a good point. Higher octane fuel would definitely help the pinging problem.

[Daox]

I went to the EV club's build day this weekend and ended up bringing up this project with a friend there. I told him about the two limits that I might run into and that I thought it would probably be the dilution problem more than the pinging. He suggested something I hadn't thought of. Ethanol apparently is more combustible and able to be run leaner than gasoline. So, he suggested that if I run into this limit that I try increasing the ethanol content of the fuel to run a richer EGR mix. So, I now have an option should I find that I can dilute the mixture too much for gasoline (E10 in my area).

I am going to have to do more research on ethanol though. I really don't know much about it.

[Christ]

It has a higher octane level, thus can handle more pressure/heat than gasoline without autoignition. Not sure about other information.

You can make your own methyl if you have consumable wood around. There's recipes for it online all over. IIRC, it's part of the soap making process. Methylene has slightly different characteristics from Ethylene, but is similar.

[Daox]

Yeah, but I believe methylene is a lot more corrosive and can eat rubbers and some metals.

[Christ]

Used purely as a fuel, yes.

I think some gasoline mfgs still use it in the formulation, though. I don't have the "recipes" handy anymore, and they've changed, surely, since the last ones I had, but it used to be in there in small amounts.

If you use it straight, it will corrode aluminum.