Civic VX: Headers vs stock exhaust

[Bow]

Just because it is a VX model...

Is the stock exhaust manifold actually different from the standard model?

I agree with NIKY, on the backpressure thing as well. an engine is an air pump... the more efficent it flows, the more efficently it makes power...

Keeping the right foot off the floor will save more gas than anything else.


It seems his VX model has a VTEC-E

VTEC-E

VTEC-E is a variation of SOHC VTEC which was used to increase efficiency at low RPM. At low RPM, one of the two intake valves is only allowed to open a very small amount, increasing the fuel/air atomization in the cylinder and thus allowing a leaner mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient mixture. A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve. The engine runs at normal performance using the second cam position that would typically be tuned for high-RPM performance in other two-stage VTEC designs.

I'm thinking a header is not going to hurt him....

[Ryland]

Originally Posted by Bow

I'm thinking a header is not going to hurt him....

Do you have any testing to back that up tho? any math used in exhaust design that does not contradict your statement? the rules used for exhaust design are closer to those of musical instruments then that of designing plumbing or a fire hose and all of you who say "a header shouldn't hurt" are treating exhaust like it's a constant stream, not pulses, pulses create a note or tone and to make that flow smoothly the exhaust pipe needs to be tuned close enough to that tone, if you don't you get distortion, feed back and that means back pressure, all because it's to big.

[mcrews]

Originally Posted by Bow

Just because it is a VX model...

Is the stock exhaust manifold actually different from the standard model?

duh,,,,,,uhhhhh.......hummmmm.....ohhhhhh......pic k my nose.........
I'm thinking a header is not going to hurt him....

Again,
READ THE FRIGGIN THREAD>>>>ALLL OF IT!!!!!!
then get back with us.


or pull your head uot of your arse and then get back with us.

these 'wondererings' and 'maybes' are just starting to get anoying in the face of factual comments.

[Bow]

Wow, nice personal attack...

Obviously, you know everything about the Honda Civic VX...

You probably also know that the first choice for home-brewing Honda Civic Turbo systems on the cheap is to get a VX Exhaust manifold.

I'm sure that is do to its highly restrictive flow properties.

If you want to read something, I'm sure the Honda guys know a thing or 2 about Hondas.

http://www.hondaclub.com/forum/artic...ere-first.html

If you are lucky and/or good, some stock header sections can be made to mate with a turbo (the D16 manifold from the Civic VX is one such manifold). The key thing here is if you are cheap and buy a pre-built manifold, buy one that is made of cast iron. Tubular manifolds look cool and offer more power, but are prone to failure. The tubular manifolds that are not failure prone are very expensive (they are worth the price of admission. On some engines a properly designed and built tubular manifold can be wroth 30 hp!). Iron is heavy and ugly but does not break and is also quite cheap.

But I digress, you obviously know everything there is about I4 engines and designs, you drive a 340hp/333 ft/lb 4.5L V8, 3800 lb, fuel sipping ecno car.

[CigaR007]

A correctly designed exhaust headers can increase fuel economy provided you don't step on the gas pedal due to the increased torque/power. The OP could check if the aftermarket headers are in 4-1 or 4-2-1 configuration. The latter would provide the most benefits due to the increase in low to mid-end torque. Again, if they are optmised for the car in question, to which some aftermarket headers are.

Now, who knows what headers he has on the civic. My advice would be to test things out with the current setup and log the fuel consumption.

[some_other_dave]

Originally Posted by Joe1234

can you use MS paint to circle or point to where that is in the following pictures?

Circled in red:




-soD

[Bow]

Originally Posted by CigaR007

A correctly designed exhaust headers can increase fuel economy provided you don't step on the gas pedal due to the increased torque/power. The OP could check if the aftermarket headers are in 4-1 or 4-2-1 configuration. The latter would provide the most benefits due to the increase in low to mid-end torque. Again, if they are optmised for the car in question, to which some aftermarket headers are.

Now, who knows what headers he has on the civic. My advice would be to test things out with the current setup and log the fuel consumption.

Agreed!


Manufactured of mass-produced cookie cutter cars do not use Cast iron for its extremely outstanding characteristics of flow, heat retention, and weight savings... they use them because they are CHEAP. Engineering design great vehicles, bean-counters turn them into good vehicles...

I have yet to see a I4 engine that does not respond well to a 4-2-1 header, which is what my truck would have, if there was one available, the only option I had was a 4-1 and it reduced the low end torque.)

[Joe1234]

I just bought another VX instead. This one was adult owned, well maintained, doesn't have a tranny bearing problem, the RPM gauge works, has the stock exhaust, has the stock aluminum wheels (175 tires though instead of 165), has less miles, CD player and aftermarket 2-way speakers (instead of no speakers and cassete player), has a 5-wire o2 like the old one but this time the sensor isn't bad, and cost pretty much the same. Now I just need to put the clear coat on the old one, put thicker oil in the tranny, and sell it for what I paid for it.

[niky]

Originally Posted by mcrews

again, I'm trying to understand how this post, while well intentioned, really pertains to the ops. How is he chasing 'theoretical lost mpg?"
Remembering he has the VX model.

And I have yet to see, ANYBODY telling me that they ABA tested their mods.....
come on......at least AB?????

I've owned several cars that have been modified. If the modifications are too aggressive, fuel economy goes down... badly. But mild exhaust mods have no appreciable effect on fuel economy in the long term and can sometimes have a positive effect. It's when you start mucking about with the other end that you screw with the EFI.

Note: Mild. If the car has a fart can the size of a trash bin, then there's a lot of economy going out the window because of the poor flow.

I know quite a bit about pulse tuning and pipe sizing. Most common aftermarket headers are tuned on the mild side, so they can fit the stock exhaust... gives them a broader sweep of midrange torque. This is why they're quite inadequate for racing purposes but leave many customers happy with the "better" fuel economy (simply because they accelerate to cruising speed quicker with the same pedal input). Other customers get noticeably worse economy simply because they drive faster.

I agree with mild sizing. Hell.. for best economy, get a mandrel bent set-up that's exactly stock size, with extra-long primaries for better low-end. I built my entire system around a relatively mild size of pipe with minor step-ups throughout and a relatively small muffler. It's not economical, mind you, but that's not because of my exhaust, but because of my overly aggressive cams. Likely to change them in the future because the overlap is too aggressive for use with propane.

The lost MPG is "theoretical" because we don't know exactly how it compares to the car in its stock condition. Here we have no AB or ABA test data, either. So to buy a stock exhaust, which is an additional cost and slap it on because of possible lost MPG due to this part is a little premature.

Of course... even better: buying a VX in better, unmolested condition and selling the riced-out one... which I thoroughly approve of.

[Ryland]

Originally Posted by Bow

Obviously, you know everything about the Honda Civic VX...

You probably also know that the first choice for home-brewing Honda Civic Turbo systems on the cheap is to get a VX Exhaust manifold.

And do you know why that manifold is popular for turbos? not because it has large internal runners but because the Catolitic converter sits right under the O2 sensor, about 4" from the head

This allows the turbo to be mounted to an off the shelf part while keeping the turbo up closer to the head, in other words the VX manifold is used because people are lazy and cheap.
I'm on my 2nd Civic VX and have owned a hand full of other super fuel efficient Honda's and they tend to fallow the same design ideas and I think it's great that we have another Civic VX owner here, I've made small mods to my own civics and undone some bad work that other people have done to my cars.