exhaust mods?

Hi coolcat-

Everyone here is trying to be so helpful!
-Rick Reece helped out moutwilfongtsi with a very relevant link. (Response 1)
-I tried to supplement Rick’s assistance with another relevant (much related) link (response 2).
-xcel (I think) tried to help us all out by pointing out my redundancy. (Response 3)
-I attempted to clarify why I believe my posting was justified. My reference to “link”
referred to an internet link. (response5)
-I assume that you interpreted my use of the word “link” to mean “relevance” and are trying to help me understand. (Response 6) Your response was very polite and on topic.

Relevant posters: In an effort to keep this thread “on topic”, if you have comments directed to me not related to exhaust modifications, (automobile, not personal :wink: ) please send me a personal message. (I have tried to be very clear, but I have learned that things are not always as they seem, and that it is easy to inadvertently step on toes here.) I do not want to be responsible for going any further off topic

Ok, have to respond here... I have seen too many get disillusioned by the "larger piping/less resistive exhaust is better."

The bigger the exhaust, the less backpressure and resistance there is. Resistance=bad and it is important to get rid of it as much as possible. Unfortunately, there is a downside to this. With a n/a engine, only one thing that pushes the exhaust gas out is the piston. The exhaust valve opens and the piston pushes out the fumes using some of the engine's energy.

When you have a smaller exhaust, backpressure is your biggest enemy. With a larger exhaust, you get rid of that resistance, however there is a problem... in your exhaust system, that piston gets a bit of assistance by a suction within the exhaust system.

You can best understand it by thinking about a straw with water. Something you probably remember from elementry school... imagine 2 glasses sitting on 2 different steps of a staircase. The glass that is higher up is full of water and the one on the lower step is empty. If you take a U-shaped straw and stick each end in each glass and you start the flow by sucking the water from the lower end, the water will continue to flow into the lower glass until the top one is empty. This is all done because a velosity has been created and gravity has chosen the direction of the flow. (If you still cannot imagine it, think about siphoning gas out of a fuel tank).

Back to the Insight, the exhaust system works in the same way, the flow of gases also has velocity within the pipes and therefore, there is a suction that literally pulls the exhaust gases out of the cylinders freeing up the engine of the old gases and taking some stress off the piston (and increasing efficiency). Now, a 1.0L can only create so much exhaust at a time (especially at low RPMs like the Insight runs), so if the exhaust is too big, the gases move slower (there is more space to fill) which means the velosity is slower and the suction is less (once again putting more stress on the piston). Also, if it is too big, there may even be some reverse flow going on within the pipes because there just isn't enough exhaust to fill up the pipe completely.

Take this into consideration when you think of doing mods of this nature to a n/a (normaly aspirated) engine. In the case of Willie's turbo Insight things are a bit different.

Just remember... it is hard to out-engineer the engineer (Honda). And for those wondering where I draw my knowledge from... I am an Aerospace Engineer with an emphasis in aerodynamics/flow. I am currently employed as a flow control systems design engineer.

If some of you have the need for speed... do what I did... invest in a weekend toy and leave the high-mileage Insight the way it is... engineered just right!

-Clayton

BlueInsight1595,
I understand your point. But... There's always room for tweaks. A good portion of the mods discussed here are pretty simple so the likelyhood of something seriously negative happening is pretty small. Plus the modders usually try to figure why the engineers went a certain way- so I don't think anyone is trying to out engineer honda, just adjust things to their personal liking which, most likely, won't appeal to the masses. Honda has the difficult task of building a car that is universally appreciated.

I overclock my pc(significantly). I get some major rewards with little downside. I understand why the engineers clocked the processor at a certain speed and I hardly think I'm trying to out-engineer them by running things out of spec. I know the issues I bring up by doing this and address them intelligently to maximize stability. As a result, I bet my PC is more stable than the majority of people on this board.
I don't think anything different is going on here.

I read through that post before... I have been on this board for quite some time (just changed cars so I changed my screen name).

All I would like to see is a verification of his claims of better mileage through a controlled test where the only variable is the exhaust bypass (before and after... a standard engineering controlled experiment).

I see it on this board and other boards... people that claim a mod makes a "significant" improvement when it can be determined through a controlled experiment that they drove the car just differently enough to induce the improvement. On a daily basis I am getting better than 75 mpg on surface streets with only a 5 mi commute to work (and at least 3 stops during that commute). These cars react well to how you drive them... just let it teach you. If the exhaust bypass improves mileage without a noise gain in the cabin, Honda would have incorporated that into the original design... I repeat... do not try to out-engineer the engineers.

The main problem that I have with this topic so far is regarding the notion of removing a cat from the exhaust system. I am proud to say that I drive a ULEV (and helping to do my part towards my city's pollution problem)... and removing a cat would increase pollutants out the tailpipe... not my idea of an "improvement" to an "eco friendly" car... just my $0.02.

bigtrouble77,



I understand that there is room for tweaks... if this was an American car we were talking about there would be a significant amount of room for improvement :lol: . I just post on topics of this nature so that people who might consider tweaks have an idea as to what they are tweaking (and what the downsides might be).

It is not the Insight community that is alone in this... the S2000 boards that I am involved in go through the same problems. Part manufacturers and individuals who purchase their parts claiming an improvement when controlled testing proves that the mod does nothing for the car (and in the case of most cat-back exhaust systems for the S2000 they hurt the low-end torque of the car... which it needs badly).

I am a CPU overclocker as well... have been for many years and do not down it... just make sure to warn others of the possible problems with doing so. I do not place electical engineering in the same category as mechanical engineering... we are still learning the capabilities of IC's and how far you can really push them. Most automotive technology has been around for long enough that we have enough data to make predictions about what the long-term outcome will be from tweaks to the system. I post infomation like I do so that someone reading through this can see both sides of the story... not just think that it is all gain with no downsides.

Hi BlueInsight1595:

BlueInsight1595 said:

The main problem that I have with this topic so far is regarding the notion of removing a cat from the exhaust system. I am proud to say that I drive a ULEV (and helping to do my part towards my city's pollution problem)... and removing a cat would increase pollutants out the tailpipe... not my idea of an "improvement" to an "eco friendly" car... just my $0.02.

Click to expand...

___If you are using the 180 ppm higher sulfur fuel from Texas, your 5-speed is a LEV. If you are using the 30 ppm low sulfur fuel from California, you are emitting as a ULEV.

___I agree with your thoughts about not trying to out engineer the Honda engineers but you don’t live in Chicago, Milwaukee, Duluth, Sioux Falls, Boston, or Augusta, Maine for that matter … Warm air mods are a fact of life for increasing fuel economy in the winter months and it’s a necessity or you live with the consequences of the Honda engineers shortcomings. I don’t know if the muffler bypass adds fuel economy as I have my doubts as well but not knowing it will or not is just that, I simply don’t know?

___In terms of OC, I used to be an avid OC’er … Anyone remember the infamous PII 300 MHz SL2W8 running at 504 MHz Anyways, I run my Celeron 1.4 on a TUSL2 at 66 MHz FSB for a 924 MHz final. Even at 1.4 GHz, the 1.4 Celeron uses less then ½ the power of a 2.0 P4 and has a smaller percentage loss in performance when considering MHz to MHz by comparison. Power isn’t free whether that be in your car or in your PC … I use what I need in my case.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:2jbwa2vq][email protected][/email:2jbwa2vq]

Wow didn't know that people felt so strong about this :!:

My $.02 for what it is worth. Honda engineers may be pretty smart :roll: but it took an American with to much time to come up with

• A turbo charged Insight

• Warm Air Intake

• Radiator block

Exhaust

I cut open the muffler (see my web site for pics) it looks to be very restricted. I would bet that the engineers :roll: never dyno'ed the engine with different mufflers. More along the lines of the quitest design.

I don't think I gained that much HP or MPG. Probably due to driving at higher speeds. Though my car hardly ever has a recal and I never use more than 2-4 bars off the main battery driving Georgia hills. Mostly 80+mph on the highway :shock: I did manage to slow down on a trip to Fla and I got 80 mpg which is lower than the 90+mpg some Insight owners get without ANY exhaust mod.

Another Exhaust MOD that I have done: Was to wrap the heat shield on the main cat and re-install. It help the CAT warm up, hold heat, keeps exhaust gas hot (flows faster), and LOWERS under hood temps. My main goal was to lower the under hood temp during the summer time. All of that heat 300+ degrees is just a few inches from the coil packs and engine block. I don't recommend taking the mod any farther IE wrapping the whole CAT. [/list]