EGR and performance questions

-
gliderider06

gliderider06

FABO Gold Member
FABO Gold Member
Joined
Oct 21, 2011
Messages
2,479
Reaction score
1,695
Location
Delaware
So on my bone stock 318, 87 Ramcharger, I am going to be adding dual exhaust W/O cats from stock manifolds back very soon. I will also be changing the intake to a spreadbore from the 2bbl. The lean burn system is being changed out for a recurved distributor with a HEI set-up. My questions are, if I am doing all of this (intake and carb swap last) do I need to keep the EGR and smog pump hooked up?
Will I not gain some performance? My main goal is better MPG. I expect about 1mpg swapping to the HEI (going by past experience) and should be about the same with the dual exhaust. I have a cast intake and Holley spread bore that I might change to, but uncertain since it runs fine with the 2bbl.
I would love to hear your thoughts.
Thanks!
 
I think I would disconnect the smog pump, but leave the EGR. The EGR actually lowers combustion temperatures. If the engine is otherwise stock from the addition of a four barrel, I think the EGR has some benefit.
 
Agreed. EGR aids fuel mileage (lets the motor take in "burnt" air with no oxygen, so there's no leaning out, but still filling the cylinders). Properly functioning, the EGR closes at WOT so there's no impact on full-throttle performance.
 
EGR is like eating your own ****....

Why waste valuable cylinder space with old gasses that won't burn again, when you can fill them with fresh air/fuel mixture that will and give you a little more power.... The more air/fuel you pack into a cylinder, the more power you can get out of it...
 
If not worried about octane( & smog legality) issues,& detonation ( read: possibly 89 or premium pump swill..) ,eliminate the EGR.. Depending on your tuning ability & patience, it can be worked around. It will be a PITA...
 
I always get rid of the EGR system, but I'm on the KISS (Keep It Simple Stupid) System. They do have merit in a working system, but why contaminate your intake charge of fuel and oxygen?
 
jos51700 said:
Agreed. EGR aids fuel mileage (lets the motor take in "burnt" air with no oxygen, so there's no leaning out, but still filling the cylinders). Properly functioning, the EGR closes at WOT so there's no impact on full-throttle performance.
Click to expand...

This is correct. Google it. I used to be anti-EGR but now I leave it in place.


EGR is evil on diesels though.
 
Engines ran just fine before EGR came along. Odd, my 70 RR never had EGR, and for some reason, I NEVER found it necessary to drill holes through the bottom of the intake manifold, LMAO

29w4wtz.jpg
 
Since EGR only operated at idle and cruise, it probably won't affect WOT power. BUT if your engine passes ANY oil at all down the intake valves expect massive carbon deposits on the valves (you'll get some from the PCV) . This is not so great for any aspect of performance.

This is even worse on a diesel. One of the reasons VW put the "cheat code" in their engine management software deactivating the EGR was to reduce the amount of intake manifold cleanings under warranty. The side effect is increased NOx emissions.
 
There is a side benefit to running EGR at part throttle. And that is the way it affects compression. With the inert exhaust in the cylinder the cylinder pressure can be artificially increased. Since the gas does not chemically react with the fresh gas, it's just occupying space. What does that mean?
Firstly, let's say you have teener with an Scr is 8/1. Well Scr means squat to a running engine so let's convert that to Dcr. With a 240* cam that works out to about 7.0/1 Dcr . That 7/1 means,it might at WOT, be squeezing just 560 cc, out of a theoretically possible 650cc, into a 93 cc space...
Well let's say you are tooling around at 2200 rpm, or some close rpm on the highway. Your throttle-blades will be nearly closed. Your engine will be ingesting a fraction of it's maximum capacity.
Let's say it might be ingesting only 30%, maybe less, so let's estimate .3 x 560 = 170cc. So you are only squeezing 170 cc under this cruise parameter, and your running Dcr is only 170/93 = 2.1/1!
What? you say? Well if you've never stopped to think about this, this is a hard pill to swallow, and no wonder the LC teener can be a slug when it comes to fuel mileage! You just have to wonder how the factory ever got fuel mileage out of them in the first place.
Okay, so the key to better fuel mileage is more compression, right? Every body knows that. But let's say some VIP nixes the hi-comp idea.What can you do?
Well lets put something into the combustion chamber to momentarily take up some space. That would do it, wouldn't it? Enter EGR. let's say you could put 30% EGR in that chamber under cruise conditions. That would be .3 x 170 = about 50cc. now you are compressing 170 + 50 into a 93 cc space. That calculates out to 2.37/1 Dcr
Big deal you say! That's only a quarter of a point.
And you'd be right, it is a big deal,cuz it's about 13% more than without. So how does that translate to fuel mileage? I have no idea. But considering as how a lightweight 69 Dart-without EGR got maybe 17 to 19 mpgUS, and a heavyweight 84 NewYorker-with EGR got 20ishUS lugging around some 1000 more pounds; I'd have to say EGR works.
Just hook up a scanner to any modern EFI vehicle and watch what the computer is doing with the EGR valve. They are dumping huge amounts of EGR into the mix, and Fuel economy is ever increasing......And this is just one effect of EGR.
Now this bs talk is overly simplified in all kinds of ways, but I think it's pretty easy to understand as presented.Keep in mind this works very well on LC engines. I don't think I'll be engineering it into my 10.7Scr, 360, anytime soon.As mentioned elsewhere, EGR is eliminated at WOT and at(usually) Idle. So power and idle quality remain unaffected.
All figures are estimates and conservative, and no small animals were hurt by the results.
Your results may vary
 
Well Sir-- gliderider06 --
I am gonna let this 'marinate' for a while before I chime in...
Great topic & thx added :D
 
only problem to an EGR is it recirculates hot exhaust gas! HOT AIR!! We all know cool air is more dense and therfore has more oxygen molecules. hot air less. That is why there are intercoolers on turbo engines. To keep intake air as cool as possible. Hot air in., Bad.
 
I used to think that way too. And at WOT, full power/full load you would be right. Absolutely.
But you have to think part throttle. With say 10%,or 20%,or even 30% hot air going into the cylinder along with the fresh charge it drives the mixture into a state of excitement, and homogenizes the mixture into a frenzied state where all/most of the charge will participate in the combustion process. Remember at part throttle/low rpm, and without EGR, the fresh charge is not very dense, and the molecules are/may be, spread all over the place, and they may not all be willing to burn in a 2/1 CR state. Perhaps some gas molecules will be trapped in places where they cannot find oxygen. Perhaps some will be stuck to relatively cool surfaces. With the hot EGR agitating all the molecules, the gas ones are more likely to find the oxygen ones, with which to react, and drive the piston down.
And the fewer unburned gasoline molecules passing out the tailpipe, the better. I mean, somebody paid good money for those molecules.
 
mech1nxh said:
Well Sir-- gliderider06 --
I am gonna let this 'marinate' for a while before I chime in...
Great topic & thx added :D
Click to expand...

Helps if you know vehicle weight,gearing carb calibration actual mechanical compression & camshaft overlap.I originally remember this,to reduce NOx... High temp combustion temps raise this, overlap /egr actually cool it down. In actuality ,egr can richen an over lean OEM carb set up., The government & lack of compression & driveability makes it a necessity on non F.I. cars.https://www.google.com/url?sa=t&sou...GIwlCJdR_vJKyqzOg&sig2=sjNR3qlIO8qGJuHIA1hJcg
 
AJ/FormS said:
I used to think that way too. And at WOT, full power/full load you would be right. Absolutely.
But you have to think part throttle. With say 10%,or 20%,or even 30% hot air going into the cylinder along with the fresh charge it drives the mixture into a state of excitement, and homogenizes the mixture into a frenzied state where all/most of the charge will participate in the combustion process. Remember at part throttle/low rpm, and without EGR, the fresh charge is not very dense, and the molecules are/may be, spread all over the place, and they may not all be willing to burn in a 2/1 CR state. Perhaps some gas molecules will be trapped in places where they cannot find oxygen. Perhaps some will be stuck to relatively cool surfaces. With the hot EGR agitating all the molecules, the gas ones are more likely to find the oxygen ones, with which to react, and drive the piston down.
And the fewer unburned gasoline molecules passing out the tailpipe, the better. I mean, somebody paid good money for those molecules.[/quoteInteresting...
Interesting description... Nice.
Click to expand...
 
WOW! Thanks guys. This has been a learning experience on EGR for me. I think that I will leave it on the 2 and 4bbl intakes (if I do change to 4bbl). I never thought that the EGR would actually add compression with its process. I thought it's sole purpose was to reburn the exhaust to further lower tailpipe emissions.
 
RustyRatRod said:
I think I would disconnect the smog pump, but leave the EGR. The EGR actually lowers combustion temperatures. If the engine is otherwise stock from the addition of a four barrel, I think the EGR has some benefit.
Click to expand...

jos51700 said:
Agreed. EGR aids fuel mileage (lets the motor take in "burnt" air with no oxygen, so there's no leaning out, but still filling the cylinders). Properly functioning, the EGR closes at WOT so there's no impact on full-throttle performance.
Click to expand...

I've been saying this chit for years and getting roasted for it.
 
This is funny... I take a cast EGR intake to machine shop to have cleaned/checked and when I pick it up he says, "Hope you don't plan on using EGR, cause the ports have been plugged."
$70.00 into an EGR intake that is not EGR. Wish I noticed that before having them work on it. I could have saved $25.00 on their service fee.
Now what to do? Try another intake, or try to get the plugs out, or use it as is?
 

Attachments

  • 001.jpg
    39 KB · Views: 135
  • 002.jpg
    74 KB · Views: 134
gliderider06 said:
This is funny... I take a cast EGR intake to machine shop to have cleaned/checked and when I pick it up he says, "Hope you don't plan on using EGR, cause the ports have been plugged."
$70.00 into an EGR intake that is not EGR. Wish I noticed that before having them work on it. I could have saved $25.00 on their service fee.
Now what to do? Try another intake, or try to get the plugs out, or use it as is?
Click to expand...

use it as is, they plug up under normal operation over time. KISS principle. One less thing to keep clean and working properly. If your engine is set up properly, it will run great and get good mileage.
 
Abodybomber said:
Helps if you know vehicle weight,gearing carb calibration actual mechanical compression & camshaft overlap.I originally remember this,to reduce NOx... High temp combustion temps raise this, overlap /egr actually cool it down. In actuality ,egr can richen an over lean OEM carb set up., The government & lack of compression & driveability makes it a necessity on non F.I. cars.
Click to expand...

Spoken for truth Mr Tim San !!!
So,as to the egr increasing fuel mileage observations, Yes, & I have done
5 Gas analysis on long term driven vehicles since ...mmm...'92.
(various Mfgr's engine sizes,& powertrain options, all egr equipped :D)

& Mr AJ/FormS, your 'hypothetical' #'s are NOT far from reality !!!
Go to bridgeanalyzers.com punch in the #'s & ck !!! all the dizzying
real world math You want :iconbigg:
Mr Schrader is a Genius with 5 Gas analysis.

Again I am gonna let this topic 'marinate' before I get into CAFE ratings, Production
costs, EPA emissions standards, Diesel, GDI, & etc...etc...etc...

Apologies gliderider06!!
Long winded I be !!! too excellent topic to pass up !!!
 
Shall we say six gas analysis?

I farted.
 
You must log in or register to reply here.
-

Back
Top