Looking for opinions on whether a properly functioning EGR valve will increase your fuel mileage, everything else being equal like driving style, type of driving (city/hwy), etc.

Right now the vacuum line to the EGR valve is disconnected and plugged. Supposing the valve itself is not stuck closed, would hooking the line back up the way it's supposed to be increase fuel mileage? If so, how much?

This is on a bone stock 86 D100.


Thanks in advance!

_________________
1970 D100 "Dude"
SL6 / 3 speed manual

EGR is not a bad thing, contrary to early urban legend, and thoughtless reactions of early owners. The purpose of the EGR is to lower combustion chamber temp. At least one of our members has used it as a port for water injection. Plumbed in the stock fashion it will work, and will allow higher ignition advance numbers, however it needs to stay closed until the engine is warmed up. In the stock configuration there is a vacuum switch in the radiator which opens when the engine gets up to temp. If opened when the engine is cold, it will kill the engine. You will need to make some arrangement to keep the vacuum off it until the engine is warm. You might be able to find an original switch if you still have a radiator with a port for it in the top tank.

Sam

_________________

The EGR's purpose is to manage emissions; lower combustion temps lowers NoX emissions. Having it working is not likely to help mileage; I would expect the opposite as combustion pressures are lower and that almost inevitably lowers effieciency in the the PV cycle (thermodynamics for pressure-volume cycle). But since it is open mostly at cruise type conditions, where mileage is high to start with, it probably won't make a lot of difference in overall mileage.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That statement, all by itself, is correct.

However, a functional EGR allows you to advance a few more degrees of timing during cruise conditions if you choose to, and that helps mileage.

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

^^^ Good info; tnx Erik. I guess I would wonder if the extra advance may cause any knocking issues while lugging on heavy grades with the trannie in a higher gear? My recollection of the mids 70's slants was that the ignition timing was retarded a bit, but I never knew if that was for emissions or to avoid knokcing issues with the hotter engine temps (hotter t'stat also for emissions).

Yes it will, I know first hand... Removed the EGR off of mine, and yes under a steep climb or under hard accel it would ping, sometimes really bad if it was a hot enough day outside. I did overcome it a little bit by making the power/cruise circuit in the carb a little richer. Still not as much timing as Id like it to have but not too bad for a stock curve in a Volare wagon with highway gears and auto trans...

_________________
"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

I ran the stock EGR for years on my 74 and it would ping a lot when hot especially going over the mountains.

I run 55 to 60 degrees at cruise (recurved distributor) for max mileage which I could never do with the stock distributor and as a result rarely ever get it to ping.

I have done the following things to stop the pinging....

1. No EGR or excess heat at the carb.
2. Heat deflector under carb. to reduce heat
3. Did SL6 Dan's fuel line mod - no more boiling fuel, less heat
4. Fresh ram air for the carb for a cooler charge
5. Water injection after 2000 rpm which lowers temps as a replacement to the EGR.
6. 2.5" exhaust to wick away heat
7. Two 10" electric fans for cooling the engine and carb after shut off.
8. A nice 6" wide air dam to force more cold air into the radiator. I remove it in the winter for more heat. This makes a big difference!
9. A 180 degree Stant Super stat for the spring and summer months, 195 or 205 in the winter.
10. lower idle speeds (550 to 600 in gear) in the summer months to reduce overall heat when stuck in traffic jams for hours.

All the items add up to make a significant difference and allow more timing to be dialed in for better fuel mileage. Click on the red link below my name to view pictures.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG