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Eliminate EGR?

2K views 14 replies 7 participants last post by  mike p 
#1 ·
Eliminate EGR? Your thoughts?


i don't have anything against EGR and what it does; i mainly wanted to clear up some space and clutter.

What are your thoughts on eliminating the EGR valve? If, in fact, it really does help the engine last longer (supposedly) then i don't have a problem leaving it. It's a stock transportation engine so i'm not necessarily wanting to remove it for any performance benefit.

Again, it's mainly to clear up some space.
 
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#2 ·
It's function is to lower emissions at idle so a car engine will pass the test at idle. Once you are off idle the valve is next to useless. If you live in a state without annual emission, or safety testing like Florida where there is no law against driving a top fuel car on the street, I would remove it permanently by installing a non-EGR aftermarket manifold that also is without carb heat.

Big Dave
 
#3 ·
Like above, EGR allows leaner mixtures.. leaner mixtures means more advanced timing...
The issue with egr over time, and this has not been resolved in the 40 yrs it has been around, be it carb/ injection/ monitored whatever... deposits build up on the inlet eventually causing loss power and issues... ESPEC if oil changes and regular service is not done... but still occurs.
It was because of the introduction of EGR that high voltage electronic ign systems where introduced (HEI) Leaner mixtures have higher resistance across the plug electrodes that require a higher voltage for consistent healthy spark....
Also with EGR manifold ported vaccuum for VA is used , where as non egr manifold ( thu some applications pre egr also used ported, usually non performance)
EGR timing tends to have far less cent and alot of VA advance......which generally means increasing the cent to around 22 degs and if need be simply by stops, reducing the VA to around the 8 to 12 deg ballpark.
initial timing non egr is made up of initial +the VA

Changing is no biggie, basically means re dialing in the engine for new tuning specs....generally no need to touch the carb... maybe slight sec butterlies adjustment an mixtures... filing/rounding .5 to 1mm off the cent counterweight tails.. and a couple little scraps of sheet metal with a hole to mount on the VA screw mounts as stoppers for the arm movement.... thu some VA are adjustable and may be adjustable enough with the screw inside the VA.
 
#4 ·
Those damn valves did teach us all a lesson though. They taught us that exhaust gas re-circulation, as was done in the mid '70's and beyond to reduce oxides of nitrogen emissions (photo chemical smog) is better done with a large overlap cam shaft. And a lot more fun too.
 
#5 ·
Maybe we better explain that a little??
As a mixture is leaned out... (economy etc after the 1st world fuel crisis of the early 70s....from memory the 7 day war??? ) one has to increase advance due to slower burn times across the chamber... but increase advance also increases NOx emissions dramatically
Was a bit catch 22 situation....

But Fred could u explain the 'how' with overlap increase? I never got my head around that.
 
#7 · (Edited)
The intake opens sooner to let in its fresh charge. The exhaust is still going out. The intake charge mixes and captures part of the exhaust that is also open longer. Make sense? Sure sounds good.;)
(edit; EGR, exhaust gas recirculation, does the same thing to cool combustion temps)
 
#10 ·
Along those same mysterious events, here's one for you Steps.
Last year I was new to my second set of Mickey Thompson Super Scavenger headers. (I might have told you this story) Anyway, with open headers and no other exhaust system installed I was turning consistent 10.90's at the strip. One day I refitted my 3" exhaust system with X pipe but didn't have time to remove it before race day, sooooo,,,,, the car ran through mufflers and was 80 pounds heavier and turned 3/10's quicker. No other changes. No other changes except turning it back into a street car. That meant new stereo speakers and stuff like that. To this day it's a 10.50 car. How's that for your weird-meter?
 
#11 ·
No weird meter m8....years ago.. the 80s went down the headers route, yeah bit overlap on the cam.. and the overlap issue happened to be on my mind from experience a good decade before.
Anyway ran a curb and cracked the headers,.. another story... that was when I threw on the old set truck rams horns and dropped near .75 of a second off and ran faster...
I knew before the plugs showed marginally lean on the centre cylinders....now the showed text book with the rear 2 cylinders doing the normal marginally rich
Basically stopped the scavenging.
Still run the truck rams horns, next off the shelf cam had a little more over lap, slightly better... this cam I designed myself , custom.. think over did the overlap/ duration slightly, but not enough to hurt anything , just a bit more lumpy idle

From memory it was from some of Smokey yunks note/ books back in the very early 70s that initially put me onto this overlap/ scavenging stuff....crap thats over 40 yrs ago!!!
 
#12 ·
Have a member on Team Impala that built a 383 that looks like a 1964 327 that he put on the engine dyno.

He ran both headers and then bolted on 2-1/2 inch ram horns cast iron Chevy exhaust manifolds feeding into 2-1/2 inch header pipes and mufflers. Below 4,600 RPM the engine made more power and more torque with the cast iron manifolds on the motor than it did with open full length 1-5/8th inch primary tube headers.

Above this RPM the headers won hands down but how frequently are you running your engine above 4,600 on the street? Tachometers on one of these cars are as common as head lights. But I sometimes wonder if any one ever looks at them.

Big Dave
 
#14 ·
2-1/2 inch ram horns cast iron Chevy exhaust manifolds
I have seen 1 set of those in my lifetime....
Below 4,600 RPM the engine made more power and more torque with the cast iron manifolds on the motor than it did with open full length 1-5/8th inch primary tube headers.
Above this RPM the headers won hands down but how frequently are you running your engine above 4,600 on the street?
Hell yeah....then throw on a smaller carb.. lot more torque there to....
Any related thoughts on long tube headers vs. shorty headers? (lower rpm torque, etc)
Yep......oh u want them to? lol
For a cruise car, doing the odd show off.. its all about torque.. throw the HP out the window... headers espec off the shelf, they are more higher end HP up around the 6000+ rpm range... and screw everything below.
Bottom line it works like this .. a unmonitored (ECU) non injected , carbed engine has at best a efficient power range of around 2500 to 3000 rpms.. higher the performance the narrower the power range.
Every now and they some guty pops up with a car, nothing to fancy and it goes like a bat out of hell.... WHY?
Because ALL the 'go components' are designed to work in a given power rpm range .... no compromises or brag component BS.....And the cam , dynamic compression ratios at given loads match the octane of the fuel at a given load and rpm.
So its not hard and rather cheap to get a basically stock sbc with the right cam to pull high 13s in mid 90s under 5000 rpms, and still run rather economically.. on todays stds.
Torque is what gets u moving quick
HP is what gives u a lot of speed when things, like wind resistance becomes a factor over 90/ 110 mph

Thats a far different 'mind set' right...
 
#15 ·
Thanks, Steps, you and others have given good info on long headers vs manifolds.

I've seen some debates recently on long tube vs short headers, with some saying that shorty is closer to exhaust manifolds in performance.

I've never used short headers, so was just wondering if anyone else here had.
 
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