Expected mpg improvement from EGR etc cleaning?

any idea what you're mpg's used to be?

he is correct, many things can affect gas mileage, but you should get some improvement.

honestly, that's a dealers price, but at least he understands it and will hopefully be conscientious.

and wouldn't you need it to stop chugging to sell for max dollars?

 

I would possibly spend $400 to $500 to clean the intake manifold and EGR circuit. $1000 is really high. I don’t think this would improve your gas mileage either, that is more of a battery issue when the car age.

 

IIRC, @jerrymildred said EGR cleaning (through Tampa Hybrids, Florida) was $600 USD, for a comparison.

EGR cleaning is not about mpg improvement; it's about saving your bacon, specifically: head gasket integrity. You're mechanics are right; 100K miles is the latest I'd do it.

 

If the clogging is bad enough to noticeably affect the way the engine runs, cleaning will decrease fuel consumption, at least a little. However, as Mendel says, that's not the most important reason.
If you don't want to spend the $1000, at least have the manifold passages cleaned, or do it yourself. That's the easy part of the clean-out, and possibly the most critical, if one manifold EGR port is badly clogged but the cooler isn't yet.

 

$1k is a little steep. As @Mendel Leisk said, Tampa Hybrids charges $600. But if you've made it to 150k with an intact head gasket, you're doing pretty well. I would definitely advise cleaning the system.

We do 6-12 a week. Sometimes as many as 15.

As others said, cleaning that system will have little if any effect on fuel economy.

It is easy to confuse misfires with a blown head gasket if you don't know what to look for. They feel similar, but the HG has some very clear telltales like various combinations of white exhaust smoke, steam cleaned piston tops, lost coolant, and/or milky oil.

Cleaning the EGR won't heal a blown gasket, but it is necessary for the protection of the new gasket and it will prevent a blown HG if done before it gets too bad.

 

I experienced no mpg improvement after several egr cleanings. Plus no mpg drop prior to egr cooler cleaning even when the egr was completely clogged. The primary purpose of egr systems is to reduce emissions. Some think it may help to slightly reduce combustion chamber temperatures. Gen2 had no egrs and the latest Toyota hybrids have no egrs.

An egr that is causing sluggish slow speed operation is stuck open without egr cooler clogging. Normally the egr valve is closed in low speed operation. The "Car Care Nut" youtube channel has a video (EGR) with a quick way to check for this. However this is rare compared to egr cooler clogging. Cleaning the cooler is a labor intensive job.

However, a marginal hv battery will reduce mpg and cause sluggish off the line acceleration. But not as much as you are reporting, maybe 4 or 5 mpg. That is what I lost when the hv battery was weak and regained after the hv battery was replaced with new Toyota cells.

Dragging brakes or really bad wheel bearings could cause additional mpg loss. Poor gas or high ethanol gas will reduce mpg as the system backs off the timing.

A few isolated cases of extremely bad 12v batteries have caused lower mpg as the charging current became excessive for long periods. Usually the 12v battery will fail to start the car before this happens.

EGR Kit mentioned in video

 

I noticed higher MPG after cleaning the EGR, Intake manifold, and throttle body. Maybe mine was really dirty and clogged prior to cleaning hence the higher MPG and better acceleration.

 

While it may be fair to say that was originally and still the primary purpose, especially on diesel engines, it hasn't been the only purpose on spark-ignited gasoline engines, not since the engineers figured out the extra efficiency gains it could bring to the table for them. Ever since, they've been designing for those too.

It really does reduce peak temperature of the burning mixture inside the combustion chamber. There's no question on that; the whole point of EGR for emissions is to bring that peak temperature down lower than where oxides of nitrogen form.

Where there has been more discussion (on PriusChat anyway) is by just how much that changes the temperature of the combustion chamber, say, the upper cylinder walls and the head, which are bathed in thermostat-controlled coolant. By bringing the peak burn temperature down, EGR isn't releasing less heat from the fuel, only releasing it more slowly, over more of the power stroke.

I've missed that news. Which ones?

 

ChapmanF got it right, as usual.
As far back as the early 1980s, Nissan, for one, was advertising reduced fuel consumption from the way they used EGR.

 

Petrol hybrid available with new Toyota Crown Crossover
2.4-liter turbocharged petrol hybrid engine producing 341 hp with four-wheel drive.
Water cooled rear electric drive with separate inverter allows greater power to rear.

T24A-FTS turbo I4 (TZSH35)

 

There's an impact on flame speed AND less heat. 20% reduction in oxygen contents (%EGR according to Toyota) results in 20% reduction in fuel due to the ECU targeting a stoichiometric air/fuel ratio. Less fuel = less heat & lower temperature of combustion gasses

 

I always accelerate slowly and keep the gas over half full

 

That's if you are comparing the engine at full output and no EGR to the engine at 80% output with 20% EGR, but that isn't realistic. If you were able to drive with 20% less fuel burn, that would be because you needed 20% less engine output, and if you didn't have EGR, the ECM would achieve the same result by further closing the throttle, and injecting the same 20% less fuel.

In other words,

The engine will produce a varying amount of output power depending on what the car needs in driving, up to its rated 105 kW maximum. Adding EGR doesn't change anything at that maximum load, because no EGR is used at maximum load. At max load, using a round 40% for engine efficiency, the engine is burning gasoline at a 263 kW rate (7.7 gallons per hour or so), making 105 kW usable mechanical output and 158 kW of heat.

Intermediate loads are where EGR is used. Say you are driving in conditions that require 30 kW of output.

With or without EGR, the engine will be producing 30 kW of output, because that's what the car is calling for. It has no choice.

Using the same round 40% for engine efficiency, that will require it to burn gasoline at a 75 kW rate (around 2.2 gallons per hour), with 45 kilowatts being lost as heat.

Without EGR, the ECM will achieve this reduced burn rate by reducing the throttle opening so less air/oxygen enters the engine. It will be the right amount of oxygen for 2.2 gph of fuel, and the ECM will inject 2.2 gph of fuel.

With EGR, the ECM will be able to use a larger throttle opening, but also admit exhaust into the manifold, reducing the manifold vacuum, so less oxygen-bearing air enters. The rest will be exhaust gases, which (to first approximation) don't burn. The resulting mix still has the right amount of oxygen for 2.2 gph of fuel, and the ECM still injects the same 2.2 gph of fuel, which is still a 75 kW burn rate, producing the same 30 kW of usable power and the same 45 kW of waste heat. However, because of the effect on flame speed, this same amount of heat is released over a longer portion of the power stroke, and the peak temperature is lower.

Less fuel = less heat and less engine output power. The ECM doesn't control how much output power is needed (the power management control ECU tells tells it how much is needed), so EGR only gives the ECM another way of reducing power to match the amount demanded. There will be no difference in the fuel burn rate or the total heat produced, except for any small difference in engine efficiency owed to the EGR itself.

That's where I simplified slightly above. I used a round 40% for engine efficiency to simplify the math. But in the non-EGR case, the intermediate output is achieved with reduced throttle opening, higher manifold vacuum, and higher pumping loss, pulling the efficiency down. When EGR is used instead, there is less vacuum, lower pumping loss, and the efficiency will be closer to the magic 40%.

Because of that slight efficiency edge, there will be slightly less fuel being burned in the EGR case, and therefore slightly less heat (just in that same proportion). Because the output power needed is determined by the driving conditions, and the only way to change the amount of fuel burned to produce the same output power is by changing the engine efficiency, there is no magic reduction in fuel consumed or total heat produced, except what you can chalk up to the marginal efficiency gain the EGR gives you.

I also, as this post was long enough anyway, didn't go pulling efficiency factors at different engine loads from the BSFC graphs (which can also be found on this site). Of course the published graphs for the 2ZR-FXE show its efficiency with functioning EGR.

 

My yields 65 mpg per tank since occ install. Been posting actual photos of mdf trip meter on here for years

 

I wish it would be possible on a gen 2!!

 

Is there an explanation for this? How would having an oil catch-can improve MPG?

 

Cooled EGR shows benefits for gasoline engines

”EGR (exhaust gas recirculation) systems now in use on diesel engines were used to meet emissions regulations. In gasoline engines, we think they are an ideal way to meet stricter fuel economy standards,” explained Martin Bauer, Development Director for engine-mounted components at Mahle Behr USA, in an interview with Automotive Engineering.”


I noticed MPG improvement. After cleaning 51MPG (2000km with 54kmh average speed). Never reached that before

 

I wouldn't expect too much mpg improvement after cleaning. To me, a clogged egr causes mpg loss over hilly and mountainous roads. Specifically, when you are going up a hill, the car will blow less exhaust out due to gravity and it ll cause more stress on the engine

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