Civic VX: Headers vs stock exhaust

[Ryland]

Sure looks like you can still buy the parts new.
Honda Automotive Parts

The VX does have a smaller exhaust then the other civics, if someone made a civic header that was sized for a 1.5L engine running at 1,500RPM then I would buy it, but race headers only hurt your gas mileage and put more stress on your engine, if you do a back pressure test (gauge threads in to your o2 sensor port) you would see that larger is not better and that with a properly sized exhaust you see very little if any back pressure, back pressure is a myth used by ricers to excuse their poor choices.

[Joe1234]

Originally Posted by Ryland

Sure looks like you can still buy the parts new.
Honda Automotive Parts

Cool. For the price of an entire second engine I can get a stock exhaust...

[Joe1234]

can't I just use a back-pressure meter and put discs or something in the exhaust to simulate the stock exhaust and cat?

[Ryland]

Originally Posted by Joe1234

can't I just use a back-pressure meter and put discs or something in the exhaust to simulate the stock exhaust and cat?

The idea behind a tuned exhaust is not adding resistance to get the "right" back pressure, because a small exhaust should have very little if any back pressure, so why would a larger exhaust have back pressure when a smaller does not? because the exhaust is moving in pulses and it takes time for each pulse to travel down the exhaust pipe, if you have a larger pipe then it will take longer for that pulse to travel to the end, to large and it will bounce around enough that it will start traveling backwards, causing back pressure, so no, closing up the hole at the end of to large of an exhaust pipe will not help.

[some_other_dave]

Originally Posted by Joe1234

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.

Input shaft bearing. If it's like the one in my 1990, it requires disassembling the transmission and removing the input shaft seal to replace. Not immensely difficult, but it does take some time and effort.

-soD

[Joe1234]

Originally Posted by some_other_dave

Input shaft bearing. If it's like the one in my 1990, it requires disassembling the transmission and removing the input shaft seal to replace. Not immensely difficult, but it does take some time and effort.

-soD

can you use MS paint to circle or point to where that is in the following pictures? (You can use imgur.com to upload it)

[hondaguy72]

It's the units that are on the ends of the main and countershafts. Main shaft comes out to the clutch, countershaft is in between the differential and main shaft. The one bearing that is in the case in the last picture should be staked in with a center punch once replaced.

full write ups are on d-series.org

http://www.d-series.org/forums/trans...ng-change.html

[niky]

Originally Posted by Joe1234

I thought the problem was back pressure. The stock setup has the correct back pressure while aftermarket headers with no cat will not have enough back pressure.

You never want backpressure.

Originally Posted by Ryland

The idea behind a tuned exhaust is not adding resistance to get the "right" back pressure, because a small exhaust should have very little if any back pressure, so why would a larger exhaust have back pressure when a smaller does not? because the exhaust is moving in pulses and it takes time for each pulse to travel down the exhaust pipe, if you have a larger pipe then it will take longer for that pulse to travel to the end, to large and it will bounce around enough that it will start traveling backwards, causing back pressure, so no, closing up the hole at the end of to large of an exhaust pipe will not help.

Basically this. Restricting the end of an over-large exhaust does nothing but cause problems. Those of us who've used exhaust silencers on large mufflers could tell you this. It just adds lag and saps power without any benefits in fuel economy.

Even the best stock manifolds of that era are nothing compared to a properly designed mild mandrel-bent aftermarket header set-up. They're cast iron with poor interior flow and surfacing and often the galleries are too restrictive.

Best thing to do: take a picture of your manifold and compare it to whatever you can find on Honda forums. If it's a cheap knock-off with crush-bends, it's hurting power and losing you MPG. Try to find a secondhand performance header that will fit your engine instead, if you can't get a stock manifold.

A well-designed set of breathing modifications will often increase fuel economy, unless it interferes with MAP function on your Civic (and they usually don't... not as with MAFs) or O2 sensor function. I had a full set-up on my car that didn't affect fuel economy one bit. And it got even better after we tuned the ECU.

That car being a Honda, instead of chasing theoretical lost MPG that you're not sure is lost, it might be better to add something that can gain you MPG, for sure. Lots of cheap tuning solutions for Hondas, from ECU-swaps to chips to Hondata (pricey though) systems... just check for legality in your particular state...

[Joe1234]

Originally Posted by niky

You never want backpressure.



Basically this. Restricting the end of an over-large exhaust does nothing but cause problems. Those of us who've used exhaust silencers on large mufflers could tell you this. It just adds lag and saps power without any benefits in fuel economy.

Even the best stock manifolds of that era are nothing compared to a properly designed mild mandrel-bent aftermarket header set-up. They're cast iron with poor interior flow and surfacing and often the galleries are too restrictive.

Best thing to do: take a picture of your manifold and compare it to whatever you can find on Honda forums. If it's a cheap knock-off with crush-bends, it's hurting power and losing you MPG. Try to find a secondhand performance header that will fit your engine instead, if you can't get a stock manifold.

A well-designed set of breathing modifications will often increase fuel economy, unless it interferes with MAP function on your Civic (and they usually don't... not as with MAFs) or O2 sensor function. I had a full set-up on my car that didn't affect fuel economy one bit. And it got even better after we tuned the ECU.

That car being a Honda, instead of chasing theoretical lost MPG that you're not sure is lost, it might be better to add something that can gain you MPG, for sure. Lots of cheap tuning solutions for Hondas, from ECU-swaps to chips to Hondata (pricey though) systems... just check for legality in your particular state...

no, it doesn't have crush-bends in it. I don't think modifications will help much in my case. It is already a VX. It is basically factory modified for high MPG. Those exterior aerodynamic mods will just make it look like ass. I'd be happy if it got the 40+ mpg it is supposed to get. Right now I'm prepping it for paint.

[Bow]

Your best bet is to leave the header... it will flow better than the stock manifold, as stated above.

If you want to get rid of the aftermarket exhaust, join a Honda forum and see if anyone is willing to SWAP you exhaust for a stock setup from the model you need... I'll bet guys will jump at it... even up, with no money except shipping costs, I'll bet you could get them to pay shipping both ways.