I have noticed a reduce in fuel economy on my b3 engine

[lancerevo]

I have noticed a reduce in fuel economy on my b3 engine. I have a cone air filter & removed the rear muffler & replaced it with a resonator to make the exhaust flow more. Also recently, I have removed the pcv valve & the top cover ventilation tube & plumbed the two of them to the atmosphere. Also does the charcoal canister reduce fuel economy by sucking the fuel vapors to the intake?

[TominMO]

Did you notice the change in fuel economy right after these changes? Did you make all the changes at the same time?

I suspect removing the muffler is the problem; too little back pressure. That might be the price you pay for better exhaust flow. Have you noticed that the car has more power? Does there seem to be less torque?

[batstiva]

I have noticed a reduce in fuel economy on my b3 engine. I have a cone air filter & removed the rear muffler & replaced it with a resonator to make the exhaust flow more. Also recently, I have removed the pcv valve & the top cover ventilation tube & plumbed the two of them to the atmosphere. Also does the charcoal canister reduce fuel economy by sucking the fuel vapors to the intake?

The charcoal cannister, near as I can remember, recycles vapors and returns them to the carb. Kind of agree with Tom on the resonator vs. the muffler. The system is designed to recycle fuel vapors as many times as possible. Anything done that interferes with vapor recollection basically ends up being wasted fuel. I'm curious, with the PCV and the vent tube plumbed to the atmosphere, how you hold vac in the engine.

[lancerevo]

I'm curious, with the PCV and the vent tube plumbed to the atmosphere, how you hold vac in the engine.

I plugged the intake manifold so no vacuum leaks.

[FestYboy]

that PCV is there for a reason, and decommisioning the vapor canister will result in higher fuel consumption.

[lancerevo]

I installed the pcv valve again. to see how it gets on fuel economy, I installed the stock exhaust muffler. All that I have not stock is the cone air filter. If I put the stock air box will it increase fuel economy? or it will decrease economy because it has a small air opening to get air to the engine.

[mechanicaldj]

how is the VAF installed with the cone air filter????

if it is not horizontal(like stock) it can cause issues

[lancerevo]

how is the VAF installed with the cone air filter????

if it is not horizontal(like stock) it can cause issues

see attachment pic. The stock air box will give me good or bad mpg?

[TominMO]

I installed the pcv valve again. to see how it gets on fuel economy, I installed the stock exhaust muffler. All that I have not stock is the cone air filter. If I put the stock air box will it increase fuel economy? or it will decrease economy because it has a small air opening to get air to the engine.

It doesn't matter whether you have the stock airbox or the cone filter. Except that at higher RPM the cone filter will let more air in, so more fuel will also be used. But for normal driving, shifting below 4000 RPM for instance, there is no difference.

[Mike McKown]

I don't see any baisis for claiming the modifications you made would drop fuel mileage.

[Banana Bonanza]

PCV is one of the actual real true improvements in pollution control and good for the engine too. On old pre-pcv engines where crankcase was vented with open pipe, you got lot more sludge buildup in the engine. If I were driving such an old vehicle, I would add my own pcv system, its that worthwhile and wont cost a nickel in lost gas mileage. And this from somebody not terribly impressed with lot modern pollution systems. Most are to reduce some small segment of offending exhaust while turning a blind eye to fuel economy and thus the total amount of pollution produced. Burn more fuel, produce more TOTAL pollution and green house gasses. The less fuel you burn to accomplish a job, the less TOTAL pollution you produce.

As to pipes, if you like noise then by all means do away with muffler. You will hurt low end performance and thus fuel economy, but you will get a smidgen more high end power and lot noise. What you want to think about is exactly how often do you rev the engine past 4000rpm? If you do so often, this more open exhaust will help you slight amount on power, but such high revs will also lessen life span of your engine significantly too. Each to their own, I'd prefer power on low end unless I'm going to the races. I am the sort that gets biggest kick out of getting 50mpg and 300,000 mile engine lifespan while interior of car remains relatively peaceful. Yep, I'm getting old.....

[lancerevo]

Hi again. Today I put back the stock air box with the stock filter and when I test drove it, I noticed nothing different in performance. Makes 0-60 in 13.85 seconds. I will see if it will increase the fuel economy. Also when I removed the intake hose, I saw some engine oil in it. I think it is coming from the top cover vent hose (blow by) There are two vent hoses on the top cover. One is this vent near the oil filling cap & the other is the pcv valve hose. If I plug that vent hose to eliminate the oil problem and leaving the pcv valve vent only, will it do any damage?

[blkfordsedan]

When you say your mileage dropped, how much are you talking? 1 to 2 MPG? 5 MPG?
It would not surprise me if you lost some economy with the changes you made. I drove my '93L for several years with a blown out muffler and rusted out converter and intermediate pipe. When I finally replaced the exhaust with an entire factory system in good shape (from a parts car) it felt like an extra 5HP! The improvement in off-idle torque was amazing. I can actually accelerate from a stop light faster than surrounding traffic if I wanted to and can pull hills @ 65MPH without slowing down much. My mileage went from averaging around 39 to 41 MPG to around 45 to 48 MPG.

Maximum HP is great for the Dyno or the track where the engine can stay at or near the RPM where max HP is made. On the street, an improvement throughout the largest RPM range (area under the curve) will produce the results that make you smile! This applies to exhaust, cams, intakes, heads, whiskey, women, you name it!

To paraphrase Tim Allen, "Women are like cars. We all dream of a Ferrari and occasionally need a truck, but we all settle for a station wagon".

[lancerevo]

My mileage is 36 uk mpg. Here where I live there are no highways so most of the time is city driving.

[Mike McKown]

I saw some engine oil in it. I think it is coming from the top cover vent hose (blow by) If I plug that vent hose to eliminate the oil problem and leaving the pcv valve vent only, will it do any damage?

I wouldn't plug the vent hose going into the air intake. Rather, I'd get a longer hose, clamp it to the nipple and drop it down below the engine. Cap the nipple on the intake tube. You'll use less oil and get rid of the oil in the intake tube. If you just plug the valve cover nipple, you might get some oil leaks out of it.