Civic VX: Headers vs stock exhaust

[mcrews]

'the exhaust pipe" is the pipe that starts after the the exhaust manifold. usually there is a muffler somewhere in the middle or near the end.
the 1.5inches od refers to the entier section of piping.

I don't. read what the other poster said uptop.
BUT that's my last post until you measure your friggin pipe. Which I would have thought you would already have done............

[redyaris]

I have installed headers & high flow muffler on my 2007 Yaris, In discussions with my engineer family and friends, after the fact, I have come to the conclusion that headers will have no affect on FE in the rpm range used by ecomodders [2000 rpm to 3000 rpm]. When the throttle is closed there will be an very small reduction in pumping loses of no use to anyone, at WOT and high rpm you will use more fuel than stock exhaust, hence more power... I would suggest that there is no good reason to take them off or put them on for FE.

[oil pan 4]

My friend with a 2.7L 2000 toyota tacoma put a header on after his exhaust manifold cracked and he failed inspection. After trying to get a used manifold for 2-3 weeks his fail sticker was about to run out.
The dealer wanted $440 for a new manifold and pacesetter had headers that fit his truck for $160.
He does not like to modify his truck at all, for what ever reason he belives in keeping vehicles 100% stock (other than tires and rims) even tho he is a mechanical engineer and always complanes about how manufactures cut corners to save a dime.

His results were he picked up about .5mpg after switching to headers.
The factory manifold wasn't a bad design, it looked alright to me.
I modified the header and extend the O2 sensor harness, it had the same setup where the O2 read off one tube. We agreed this would not be ideal for fuel economy. So I plugged the sensor hole on the tube and installed an oxygen sensor bung in the collector.

[Joe1234]

Originally Posted by redyaris

I have installed headers & high flow muffler on my 2007 Yaris, In discussions with my engineer family and friends, after the fact, I have come to the conclusion that headers will have no affect on FE in the rpm range used by ecomodders [2000 rpm to 3000 rpm]. When the throttle is closed there will be an very small reduction in pumping loses of no use to anyone, at WOT and high rpm you will use more fuel than stock exhaust, hence more power... I would suggest that there is no good reason to take them off or put them on for FE.

now the question is whether the O2 sensor location matters when on the cylinder 1 exhaust port vs farther down the exhaust where all the pipes meet.

[PaleMelanesian]

Consider this: The VX has smaller manifold pipes than the other Civic models of its generation. It's also the high-mpg version. Why did Honda choose to make a different manifold instead of using the same one for all models? Because it's more efficient for this specific car, that's why.

[Joe1234]

Originally Posted by PaleMelanesian

Consider this: The VX has smaller manifold pipes than the other Civic models of its generation. It's also the high-mpg version. Why did Honda choose to make a different manifold instead of using the same one for all models? Because it's more efficient for this specific car, that's why.

damn it... that's a good point. I can't find that manifold and cat though. Where can I buy them?

[CigaR007]

I'd be more concerned about the transmission than the exhaust setup considering the car was riced up. Just my 2 cents.

[redyaris]

Joe1234
Run it the way it is for now, then look on ebay or local auto wreckers for stock exhaust and intake parts. One of the problem with after market headers is that they use non oem conections between header and the rest of the exhaust system, so look at what is there and consider getting the whole system so that you can avoid problems. I had to re-machine the aftermarket header flang on my header so that I could use the oem parts and set up. As others have said if you want FE then the stock set up is the best starting point, and any real improvement on the stock setup would take more time and money than the average person has. I alway remember seeing a picture of a Honda engine development center that had over 100 dynomometers... and that was only one of many Honda engine development centers!

[California98Civic]

Originally Posted by PaleMelanesian

Consider this: The VX has smaller manifold pipes than the other Civic models of its generation. It's also the high-mpg version. Why did Honda choose to make a different manifold instead of using the same one for all models? Because it's more efficient for this specific car, that's why.

Does anyone know how the sixth gen HX or CX exhaust system compares with other trim levels of that generation as to PD and BP?

[Joe1234]

Originally Posted by CigaR007

I'd be more concerned about the transmission than the exhaust setup considering the car was riced up. Just my 2 cents.

It's funny you mention that. The tranny makes a rapid tapping sound even when it is in neutral. It goes away when the clutch pedal is pressed down. I'm guessing it is one of the bearings in the transmission.