Increasing EGR flow for better mileage

[Daox]

Unfortunately, I still don't have the Aveo running right. I'm getting a P0300 random misfire code that I can't seem to find the cause of. It won't even run in closed loop mode until I fix it.

[eco86]

I haven't read through this entire thread yet, but AutoSpeed has some articles explaining how modern EGR systems can be used to increase fuel economy.

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I've actually installed the system mentioned in the AutoSpeed article in my Honda Accord, and seen the MPG of my car jump between 6 and 10% depending on whether I'm driving in the city or on the highway. I set up a potentiometer that is wired so as to add resistance to the lift sensor on the EGR system, which fools the computer into thinking that the EGR is closed more than it actually is. I've also wired in a switch to allow me to go between the stock EGR opening and the modified values. On the Honda ECU, the computer is set to apply EGR at light throttle loads (<50% or so), but not at idle speeds (to prevent the engine from stalling). I'm not sure about Toyota or other manufacturer's systems, but this means that on the Honda, drivability remains the same, but part throttle cruise fuel economy improves, and the coasting distance with the throttle closed increases.

[eco86]

And no, I have no idea why the articles I links say "Browser Warning". I guarantee its a legitimate site.

[EdKiefer]

Originally Posted by eco86

I haven't read through this entire thread yet, but AutoSpeed has some articles explaining how modern EGR systems can be used to increase fuel economy.



I've actually installed the system mentioned in the AutoSpeed article in my Honda Accord, and seen the MPG of my car jump between 6 and 10% depending on whether I'm driving in the city or on the highway. I set up a potentiometer that is wired so as to add resistance to the lift sensor on the EGR system, which fools the computer into thinking that the EGR is closed more than it actually is. I've also wired in a switch to allow me to go between the stock EGR opening and the modified values. On the Honda ECU, the computer is set to apply EGR at light throttle loads (<50% or so), but not at idle speeds (to prevent the engine from stalling). I'm not sure about Toyota or other manufacturer's systems, but this means that on the Honda, drivability remains the same, but part throttle cruise fuel economy improves, and the coasting distance with the throttle closed increases.

That site has good info IMO , I agree with most things he posts . On all the cars I have worked on that I notice EGR operation, they all work as you noted . nothing at all at low speeds near idle, then slightly above idle speeds the slowly open as long as its only part throttle (low loads).

I am afraid in stock config (EGR plumbing) , I don't think you can gain to much from increasing EGR flow as many cars I can hear a lite miss fire when EGR is fully open and in neutral .
I think the reason might be the distribution of EGR gas to each cylinder . Most just run a single EGR valve to the plenum and that might not give real even flow to each cylinder, if it had say a distribution piping to each runner I think it might get better results .
Other thing when EGR comes on full you need to raise throttle input a lot more to maintain power , some might not like this feeling (little less responsive ) .

[Daox]

I've decided to try and go ahead with this despite the Aveo still not operating properly. So, today I gathered the components and layed them out to see what would need to be done to get this setup installed in the Paseo. Here is the layout I figured out.





So, I need to weld a block to the exhaust manifold. I believe this is 409 stainless steel. Does anyone have any experience or tips for welding mild steel to 409SS?

[Christ]

Originally Posted by Daox

I've decided to try and go ahead with this despite the Aveo still not operating properly. So, today I gathered the components and layed them out to see what would need to be done to get this setup installed in the Paseo. Here is the layout I figured out.





So, I need to weld a block to the exhaust manifold. I believe this is 409 stainless steel. Does anyone have any experience or tips for welding mild steel to 409SS?

The exhaust manifold should be cast iron... you can braze to it much easier than welding. Welding will likely leave micro cracks which will enlarge over time and leak.

If you can find a fairly flat spot on the manifold, you can just drill and tap a mount location right into the manifold. Probably best to get a spare, though.

[Christ]

unless it's shaft drive... then its' a diff story.

[Daox]

The manifold is stamped and welded steel. I assume from it being a high heat area and rust resistant that its 409 SS. Heres a pic, you can see the weld beads on the sides and around the pipe.

[Christ]

Ah, ok, I see now.

Still, can you mount the tube directly to the exhaust manifold? Or isnt' there a spot flat enough? (Hammer? LOL)

I've never welded stainless, but one of my neighbors welded a stainless catalytic converter to my normal mild steel exhaust tubing for me. He said it would eventually break the weld, but it never did. :shrug:

Probably if it were me, I'd have someone either build up an area of weld, then drill/tap it to bolt the flange directly on, or weld a plate to the header and do the same. (or just some studs and drill a hole)

[mwebb]

why do you not
tap into the exhaust pipe , AFTER the cat converter

there would be less 02 so the EGR gases would be more INert then the gases at the manifold and
due to a longer length of un insulated connecting tubing
the gases after the cat would be cooler which will reduce combustion temperatures and NOX better than the hotter gases at the manifold .

and
it is relatively easy to weld a bung on the exhaust pipe .