Free-flowing Intake and Exhaust for Fuel Economy

[rh77]

I went to the Honda North America Website, and they don't have an e-mail link, so we'll have to draft a letter as a collective site, or even better, use your connections if you can work them.

One problem -- they'll want you to buy OEM equipment because that's what they designed for the vehicle, and the dealer repair/parts network is important to the organization -- so it might get political.

RH77

[JanGeo]

Well guys it works in a couple of ways - there are equations that calculate the length of the pipe to give proper tuning as a function of the cylinder displacement and pipe diameter to get proper extraction effect. Valve timing can really affect how it performs because back pressure with intake and exhost overlap vs no back pressure and valve overlap can cause different amounts of discharge gases remaining and different amounts of fresh charge getting into the cylinder thus affecting efficiency. Best to have very little restriction and the valves set to not allow intake charge from getting out the exhost before it goes through a power cycle and gets burnt. Big thing is to have the length and diameter correct so that you get an extraction effect from the prior exhost pulse helping the next exhost cycle pull the gasses out of the cylinder. Of course at low throttle this does not matter as much Oh and you can tune it for RPM so pick your operating speed!

[SVOboy]

I think we could just inquire about the design choice and tie it into their environmental commitment and say we love your design, but we were wondering about a civic ex exhaust on our civic vx.

[rh77]

Originally Posted by JanGeo

Well guys it works in a couple of ways - there are equations that calculate the length of the pipe to give proper tuning as a function of the cylinder displacement and pipe diameter to get proper extraction effect. Valve timing can really affect how it performs because back pressure with intake and exhost overlap vs no back pressure and valve overlap can cause different amounts of discharge gases remaining and different amounts of fresh charge getting into the cylinder thus affecting efficiency. Best to have very little restriction and the valves set to not allow intake charge from getting out the exhost before it goes through a power cycle and gets burnt. Big thing is to have the length and diameter correct so that you get an extraction effect from the prior exhost pulse helping the next exhost cycle pull the gasses out of the cylinder. Of course at low throttle this does not matter as much Oh and you can tune it for RPM so pick your operating speed!

Right, but I don't plan on replacing the cams with the exhaust -- and Honda engines tend to have quite a bit of valve overlap -- especially with VTEC systems. That's why the some intakes are super-loud and require a silencer for the average user. So, do you just play it safe and stay stock? Is there an equation for the above? Hopefully SVOboy can get us hooked up. And for the non-Honda folks here, sorry, but they're really particular when it comes to emissions and efficiency.

RH77

[SVOboy]

Valve timing is a sticky wicket.

Unfortuneately I can't do much on the front of calculating exhaust unless were talking about turbos, however, I can find us something out about cam timing. I have actually been thinking about that a lot lately and that's my next area of research, so we'll see.

[rh77]

Originally Posted by SVOboy

Valve timing is a sticky wicket.

Unfortuneately I can't do much on the front of calculating exhaust unless were talking about turbos, however, I can find us something out about cam timing. I have actually been thinking about that a lot lately and that's my next area of research, so we'll see.

That I didn't consider -- you can adjust the cam timing. I've never done it, but it doesn't sound easy. I'll have to consult the Haynes manual...

RH77

[JanGeo]

AS I recall the VTEC opens valves more and with different timing at higher RPM so just quit reving it (yeah like that will happen) and you should be able to get good economy. Make sure your header pipes are the same length for each cylinder and are free flowing and pick your muffler to suit your noise lever. My firent with the F150 also has a Honda and used to work for Honda so I will ask him about exhosts. He has the VTEC in his Prelude.

[SVOboy]

You've got the concept of vtec pretty well. rh77 doesn't have it, , neither do I, though I will soon!

I'm excited, vtec is the shizzle, y0.

[rh77]

Originally Posted by JanGeo

AS I recall the VTEC opens valves more and with different timing at higher RPM so just quit reving it (yeah like that will happen) and you should be able to get good economy. Make sure your header pipes are the same length for each cylinder and are free flowing and pick your muffler to suit your noise lever. My firent with the F150 also has a Honda and used to work for Honda so I will ask him about exhosts. He has the VTEC in his Prelude.

Well, the exhaust system I need is for the non-VTEC in the garage. The VTEC V-6 sucks the fuel down when on the agressive cam, so I tend to stay away from that area of the RPM band, but it will haul when prompted (I do need a CAT for that one). It's the old-school VTEC where it it kicks-in at like 4500 RPM; the new i-VTEC varies the timing/lift based on a whole shload of conditions.

So my it's for the DOHC 1.8L Non-VTEC(B18B1) engine (Integra). So, there's the piping from the header, a CAT (which is still good -- gets to stay), a resonator, muffler, more piping. Smaller/larger diameter, replace the header (what style), muffler type??? I'd hate to spend the money on something that kills my gas mileage, because once it's installed, its in there until it breaks.

RH77

[rh77]

Originally Posted by SVOboy

You've got the concept of vtec pretty well. rh77 doesn't have it, , neither do I, though I will soon!

I'm excited, vtec is the shizzle, y0.

I believe the proper response is W00T? :-P My '99 Si taught me a lot about VTEC -- the modified intake was louder than the exhaust, and what a rush. But putting a free-flow exhaust on there (Greddy Evo) actually increased fuel consumption -- was it psyhological? Maybe. Was it mechanical? Possibly. Was there too little backpressure? Perhaps. Am I starting to sound like Donald Rumsfeld? Likely.

RH77