Wald GS

iTrader: (1)

I decided to make this informative post just like the one johnee started regarding the motormounts.

Well today I replaced the alternator with a denso alternator which is the same exact one lexus sells, but without the lexus sticker. I also replaced the egr valve and the check engine light is gone. I have also noticed better mileage and the car running alot smoother.

gs300_r1

good info to know ill probly be changing those out soon thanx

Epik

iTrader: (7)

I hear ya on the alternator.. big difference there.

As for the EGR.. I just blocked mine off. And the JDM GTE head I'm installing in a week or so doesnt evn have a provision for it Lovin South Carolina!

BlazeGS3

I'm quite surprised you noticed a difference in mileage. Neither of those should have much if any effect on gas mileage, but I would be interested to hear if others experienced the same.

turbogs300

Not true!!!

The Exhaust Gas Return system was designed to reduce emissions, but that's not all it does. On the positive side, having a properly working EGR will give you about 10% higher fuel mileage than a blocked off EGR valve. The negative side is that the throttle body is easily fouled by carbon deposits left behind by the recirculated exhaust gases and these gases heat the intake manifold.
How does the EGR work?

The EGR valve opens under partial manifold vacuum and allows exhaust gases to recirculate back through the intake manifold and into the throttle body inlet. The EGR flow dilutes the oxidizing capabilities of the incoming airstream, thereby requiring more throttle opening to properly burn any set amount of fuel. Because of of the additional throttle opening, manifold vacuum is reduced, and pumping losses are lowered. The end result of this is a desirable increase in fuel mileage. When more throttle is applied, manifold pressure increases, and the EGR valve closes. Due to the large volume of incoming air when the throttle is opened, any heat build up in the manifold housing is released quite rapidly. Any heating of the intake airstream that could contribute to a performance loss is real, but short lived.
Why block it off?

The reasons that stand out the most are to reduce carbon deposit buildup in the throttle body and to reduce the temperature of intake manifold. The heat that builds up in the intake manifold is very minor but it is real and reduces some of the work your intercooler is doing. When at WOT the EGR is closed but the intake manifold has already been heated, the retained heat is then released into the intake air stream decreasing performance. A big reason why this mod would be done is because of carbon deposits in the throttle body. The deposits can get so bad that it could lead to the idle speed becomming unstable. You could easily waste money on new plugs, plug wires, and diagnostics to solve the idle problem when all it really needs is a good throttle body cleaning.

But is blocking off the EGR worth it? It will save you from having to clean out your throttle body every couple years. It will also give you quicker response when you gun it from normal driving and maybe one-hundredth of a second on the 1/4 mile. But the cost can be nearly 10% higher in gas prices. Doesn't sound like much until you run through a couple tank fulls. Another thing is that the engine light will come on in some California emmissions vehicles.
How do I block if off?

Two basic methods of doing this are common. You can make a block off plate by using the EGR gasket as a model or you can use a valve to close the EGR when necessary.

BlazeGS3

Can I get that in english? I get that it reduces the combustibility of the intake gases, and I assume that means that the o2 sensors alter the fuel delivery, but I don't see how it improves fuel economy directly. Can you explain that in layman's terms?

turbogs300

A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.

The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.

So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn't air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.

Now we understand why it is there. And we understand what it does. So what can go wrong with it and what are the symptoms??

It's really pretty simple - it can be open when it isn't supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn't open when it is supposed to open you will probably experience a symptom of "pinging" or "knocking" since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine).

There are a zillion different types of EGR valves some of which work strictly on vacuum, and some which work on a combination of vacuum and pressure. Some have electronic controls, some have mechanical controls. I won't go into detail here about all the different types but suffice it to say that most can be checked by looking inside to see if the plunger shaft is stuck open or doesn't move when the engine is revved up (after it is warmed up). Replacement is probably the easiest part since most are held in by two small bolts and have a vacuum line connected to it. The hard part is whipping out your Visa card to pay for it since most of them will drain your reserves in a hurry!!

BlazeGS3

Quote: "They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything!"

So my initial question was how a clean EGR improves fuel economy because I didn't see how it did. Based on this explanation, I still don't see how it does. Sorry to ask the same question again, but can someone give me a straight answer? I appreciate the history lesson and rather enjoyed reading it, but a simple explanation will be more than sufficient.

turbogs300

Obviously, if it's clogged or restricted it can't do it's job, resulting in higher combustion temps burning more fuel. Simple enough?

BlazeGS3

Whether the fuel is burned in the combustion chamber or purged out the tailpipe, the fuel economy is unchanged. Want to try again?

turbogs300

NO!! You're not reading and comprehending.

So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas

RA40

iTrader: (6)

Nice write-up turbogs300

I experienced similar with the 5M-GE when replacing the EGR valve and cleaning the pipe up. Didn't have a clue how it all functioned except for the simple part that the gases were recycled.

Now I know.