EGR and the renesis
 

This is from the Mazda SAE paper on the Renesis when it first came out.


https://cimg7.ibsrv.net/gimg/www.rx8...a2d8f93fe2.jpg


Thing is .......... I think it grossly underestimates the EGR present in an REW engine .I don't think they can be considering the gas that will turn around over the apex as it passes the port.
My reading suggests that up to 40% EGR can be tolerated in a piston engine .
Only 10% in the Renesis seems like way too little .
I think there is an opportunity to get some free efficiency .

Anyone else looked at it ?



For Reference:
http://www.autospeed.com/cms/article...eback&A=112612

https://cimg1.ibsrv.net/gimg/www.rx8...5e3edce589.jpg

A whole lot to think about there.

Worth having a play I think .......

I'm more than willing to try it, but I don't have an easy way to make it happen. I could in theory tap off of the exhaust pipe, then use an EGR cooler of some kind and put it back in the intake. Do you have a better idea?

I'm getting a small bridgeport put in this next engine to see if I can find a good internal EGR setup. The full width one i tried last time was too much and necessitated a richer idle/cruise . Going to see how that performs with an open wastegate at idle/cruise .

Other than that you would need a cooler and a variable rate valve to get a decent external system. Maybe there are cars in the junkyard that already have this equipment ....

Ok, I had an idea for how to test this at idle. It will involve a long length of hose and look kinda like a suicide in progress, but it will work.

Haha .............. wont that void your warranty ?

So ........ the engine is running and my initial testing seems to be pointing in the right direction . Hard to quantify though. Will need to do a few tanks at cruising speeds to really see . Which is kinda hard for me to do.

I have a smaller bridge. It does behave a little weird, and has close to 80k miles... I wonder if this could be part of the reason? Even at a high speed cruise with a fair amount of load I get between 16~20 MPG with very little tuning. I know it's running really rich.

Got any pics of the bridge ?

First full tank test done today . Covered 250miles on 13.42 us gallons = 18.6 mpg

50%cruise at 110km/hr ish and 50% windy up and down country roads mixed with the odd foray into boost , so was certainly not an economy run. The impressive thing about it was i was running E30 which is approx 10% economy penalty .

I think what i'm seeing is a definite improvement ! Somewhere around 10% .

This is the only one that I could find really. I had a lot more, but that memory card was eaten by my dog...

https://cimg3.ibsrv.net/gimg/www.rx8...a7930f96f5.jpg

Here is mine . Little bit later in the timing but wider (plus mine has cuts in the housings). So about the same size overall.

So RD , do you think overall you are seeing improved economy over stock ?

https://cimg0.ibsrv.net/gimg/www.rx8...d0e839e996.jpg

My housings are notched too. Honestly, with it being tuned so rich I get about the same as I did stock, so I would say there may be room for improvement. I wrote it off as a fluke because you wouldn't think that a power adder would improve efficiency.

At 22:1 AFR, before we tuned it at all, It was getting high 20's low 30's MPG... lol That was just one day though.

What timing were you running at 22:1?

For reference : I did an almost identical drive as above on E50 a while back . Same road but to a town not as far up the coast.

E30 with bridgeport and fully open wastegate at cruise - 18.6mpg
E50 stock porting and closed wastegate at cruise - 14.7 mpg

so ...21% improvement . Approx. 8% of that can be put down to the switch from E50 to E30 . The effect of the open wastegate at cruise would be negligible but could be worth a small portion of the total. So most of the rest (13%) can be attributed to the EGR from the bridgeport.

Having WG open in cruise was worth a couple of MPGs for me, but that was on a very restrictive turbo. Haven't tried a back to back test with the new turbo.

I did do a crusie test of open vs closed back to back measuring , maf, throttle position , load , afr etc .
I could see no difference at all , but didn't try measuring fuel consumption . Mainly because I didn't think it would be measurable given the above test .

I did notice that the average pressure pre throttle was lower , so that could result in better mpg , but I would have expected to see something in the above measurements as well.

May just be the difference in back-pressure from the turbo sizing. I doubt I would see as drastic a difference with the current turbo.

Just did more of an economy test consisting of 80% highway cruise and 20% city . Driving sedately with no boost but keeping up with the general traffic flow .
Wastegate open to simulate N/A driving.
got 19.6mpg . Taking E30 into account makes equivalent to approx. 21.4mpg

Was actually expecting better but still ..... not too shabby.

Very nice - again I wonder why active EGR wasn't studied unless the reburn adds more carbon buildup to the engine/cat/exhaust; something not easily studied short term unless you can analyze the exhaust components using a GC-MS.

Quite possible that Mazda was worried about engine longevity . They would have had plenty of time to study the effect of EGR on previous engines .

It would be great if Mazda externally-sourced research on a new rotary upgrade/design. Winner get royalties and Mazda gets the IP. We win!

It was just the first start up and drive around to make sure it was running correctly. The ECU was pretty freaked out at first.

Just did a 160 mile round trip which was 10% city , 50% flat highway , 40% hilly highway . So again , not ideal conditions for mpg but I was driving carefully and keeping up with traffic.
This time I had put a stopper on the ssv valve to stop it ticking . I noticed straight away that vacuum was lower at idle with this in place so thought maybe it might help with mpg as well .

result ........23.4mpg or 25.7mpg if factoring in the E30 !!!!!!!

Maybe I should do an economy run at 100% gas and 100% highway ...............