Tailpipe fuel consumption effect

[lancer5790]

does the tailpipe affect the fuel consumption? I had the tail pipe (about 8inches long protrutding pipe after the muffler) of my 97 honda city cut off then replaced with an aftermarket stainless pipe with larger diameter. since then i noticed the fuel consumption went up. could this be due to the replacemenmt of tailpipe?

[ghosthunter]

The car exhaust system is not a simple thing.

You have to balance the exhaust velocity with the size of the piping and the engine's performance & typical use.

Too small diameter of pipe will cause restriction.

Too big diameter of pipe will cause the exhaust gasses to slow down too soon and cause more backpressure than you want.

An exhaust system that has too many bends will also cause the exhaust gasses to slow down.

An exhaust system with pipes that change diameters is not that good for performance but it might help adjust the exhaust note.

To simplify the exhaust system, a single diameter should be chosen that will match your engine's performance. For a 1.6L engine, a maximum of 2inch pipe diameter is optimum for performance. For better fuel economy, the stock diameter is best (I think it was 1.5 to 1.7 inches).

[ghosthunter]

does the tailpipe affect the fuel consumption? I had the tail pipe (about 8inches long protrutding pipe after the muffler) of my 97 honda city cut off then replaced with an aftermarket stainless pipe with larger diameter. since then i noticed the fuel consumption went up. could this be due to the replacemenmt of tailpipe?

Was the tailpipe tapered (narrow to wide)?

[lancer5790]

Was the tailpipe tapered (narrow to wide)?

yes, the entire protruding pipe was replaced with about 3"dia from the original 1.7" i think. but the point is, the cut pipe was already after the muffler?

[ghosthunter]

yes, the entire protruding pipe was replaced with about 3"dia from the original 1.7" i think. but the point is, the cut pipe was already after the muffler?

In all of my past exhaust mods, the tail-pipe was always the same size as the rest of the exhaust piping.

Is the new 3" pipe the same diameter in it's entire length? Or is it like a cone inside?

[duskylim]

Dear Sirs:

In my experience most 1995 and up model cars have very good exhaust systems, with excellent balance between power and fuel economy.

One of the worst modifications that can be done is to fit an aftermarket tailpipe purely for visual and sound effect.

Some may believe they sound and look good (I for one do NOT), but they are terrible for your fuel economy and performance, both mileage and acceleration suffer from this modification.

My advice would be to stick to the stock system unless the installer can guarantee (on his dime) that performance will improve.

Of course, marami naman diyan na ika-mamamtay ang pagpo-porma.

[lancer5790]

In all of my past exhaust mods, the tail-pipe was always the same size as the rest of the exhaust piping.

Is the new 3" pipe the same diameter in it's entire length? Or is it like a cone inside?

the 3" pipe which is about 6" long has the same dia all throughout but then the connection (flared like a reducer) between this 3"pipe and the muffler is 1.5" in diamtere about 1.5" long...

[ghosthunter]

the 3" pipe which is about 6" long has the same dia all throughout but then the connection (flared like a reducer) between this 3"pipe and the muffler is 1.5" in diamtere about 1.5" long...

Believe it or not, that "flared" pipe is your constriction point in your exhaust.

The change in diameter is too sudden which suddenly changes the velocity and pressure of the exhaust gasses. This adds backpressure to your car's exhaust and will just increase as engine increases RPM.

[duskylim]

Dear Sirs:

The main problem here is that spark-ignition engines throttle the charge air in order to obtain an ignitable air-fuel ratio (ranging from 12.5 to 1 up to 16.5 to 1).

As such you have a situation where there is a vacuum on the intake side and higher than atmospheric pressure on the exhaust side during all engine operation regimes up to full throttle.

As gas flows from regions of higher to regions of lower pressure, the tendency of the exhaust gases is to flow backwards towards the intake during those periods when both intake and and exhaust valves are open - this is called 'flow reversion'.

Complicating this is the pulsating flow of the whole system, for example, as the exhaust valve opens, a high-pressure (sonic) pulse travels down the exhaust manifold through the mufflers and ultimately to the atmosphere.

That pulse then expands and pushes the atmospheric air out of it's path - and the atmospheric air then rebounds and pushes back - producing an opposing pressure pulse that travels back up the system.

If that pressure pulse appears when the exhaust valve is opening - it will oppose the outflow of gases from the exhaust system and choke the flow.

That is the reason for the loss of power and economy in badly designed exhaust systems.

Timing of these sound pulses is the key to good design - the fundamental frequency being matched to the engine rpm, with harmonics being super-imposed on them.

As you can readily see, this is a task for powerful computers and very good engineers.

Best Regards,

Dusky Lim

[lancer5790]

Believe it or not, that "flared" pipe is your constriction point in your exhaust.

The change in diameter is too sudden which suddenly changes the velocity and pressure of the exhaust gasses. This adds backpressure to your car's exhaust and will just increase as engine increases RPM.

i think you're right sir. im putting back the original tail pipe asap. thanks for all your comments!