midpipe - new record?

[S800Racer]

I just replaced the mid-pipe on my Si. 2.25" crush-bent from cat to stock muffler. I may have the record for "best deal" - $67.80 :D
I have done business with this exhaust shop before and they always do great work at a great price.

On the plus side: I like the new sound. It's a nice, sporty note that is not at all loud or obnoxious. For anyone that wants a better exhaust note but not a loud one, the midpipe is a very good, dirt cheap way to go.;)

The "butt dyno" didn't notice any difference in performance. I tried it out on my test hill (see my post "The 0 $ Dyno") and was mildly surprised to see no gains - same times and performance as before. Those Honda engineers are too good - the stock systems are always a challenge to improve on! Maybe the stock muffler is too restrictive? I am considering a good straight through style of muffler to replace the stock unit but I don't want to get too loud.

Overall, I am happy with it - it sounds better and it's not slower.:)

[kenis138]

Sounds to me like you need a header.....

[modern-perf]

The stock exhaust manifold IS a 4-1 header. What you need is a performance muffler!

[ssvr6]

I disagree. The stock muffler is fine for a 2.25.

Steve

[S800Racer]

Originally posted by modern-perf
The stock exhaust manifold IS a 4-1 header. What you need is a performance muffler!

I agree. Someone else has posted excellent dyno numbers with a stock header, CAI, midpipe and performance muffler. The next mods on my list include a muffler, heatshield gasket & a hondata upgrade.

PS - I really wish I had a K20A2 -- you suck.

[JSIR]

The stock header is a 4-2 design, based on the collector shape. I don't find it all that free flowing based on its design of the primaries and collector, but it does do a fairly good job with the other stock components. It dumps into a single 2 inch I.D. downpipe that is attached to the cat. conv. , so effective making that pre-cat exhaust system a 4-2-1 . I am now using an HP header, it is a true 4-1 header based on it's collector design. I think I still have pics of the two collectors if anyone is interested.

The stock muffler is not very restrictive at all, it is the same part used on the CTR, so it supports over 200 hp. On my engine I did a test dyno run where we pulled the muffler off , and we did not find any increased power without the muffler. That was with an intake, header, midpipe upgrade.

You have to remember these k20 engines respond quite differently than Honda engines of the past when it comes to mods. They are more about getting the perfect flow rate, rather than the maximum flow rate, there is a difference between the two. In other words getting the correct combination of aftermarket parts is more important than having the largest number of aftermarket parts. I think exhaust velocity is more important than exhaust flow rates on these engines.

It seems that an intake, stock header, and full cat back exhaust modded car performs the same as an intake, header, midpipe and stock muffler modded car. I believe they are both achieving the same flow rates using different mods. Thus that doesn't mean that adding a full cat back exhaust on the second example will necessarily increase power. It all depends on what happens to the flow rates when you add that full cat-back exhaust, is the exhaust gas velocity speeded up or slowed down by a cat back exhaust ?. Hard to say without actual testing, but I still think a good midpipe with stock muffler combination can flow as well as other more expensive combinations.

Right now I am running a 2.25" crush bent mid-pipe with the stock muffler. I am willing to bet a good mandrel bent 2.0" midpipe would perform even better on our cars than the larger 2.25" pipe as it should provide even better exhaust flow characteristics. It's a gamble I am going to take in the spring months, I think it will pay off. I have found out that a 2.5" midpipe performs worse than at 2.25"midpipe at all rpms on our cars. So you never quite know what works until you test it out.

hth.

Joey

[!@#$%]

what about a 2 1/8'' midpipe? any theories how this would work out? shouldnt lose as much tq as the 2 1/4, but might flow smoother when running through the connections.

would this size maybe show some good gains? or do u think2 1/4 will still be better?

[JSIR]

Can you find 2 1/8th inch piping, I don't see that much around here, but if you could that may be a perfect midpipe size when used with our stock muffler if you can get it mandrel bent. Our stock muffler piping is 2 inches (50mm) ouside diameter on the piping leading into the canister. So it would be a good match. If you are going with a crush bent mid-pipe then 2.25" is best because it necks down to 2 inches in some of the bends at the narrowest point. If you are going with an aftermarket muffler then you would really have to test different midpipes to see what works best.

[02blksi]

"I agree. Someone else has posted excellent dyno numbers with a stock header, CAI, midpipe and performance muffler"


I believe you are reffering to me, i posted my dyno numbers with just I/E and they were really impressive IMO.
I dont think that the stock header is all that bad at all. As far as qualtiy and fittement, well its an OEM piece so we wont have any issues like the DC sports version. The gains posted by people with a header were minimal if any. I have yet to see a header combo that puts them away from a OEM setup with similar mods.

Side note: something to think about.
I dont know if anyone is aware but the Type R owners all rave over the JDM OEM header for their DC2 chasiss. Reason, they are well designed oem pieces, similar to any aftermarket piece, SS, and less $$ (used) ..... They also flow a little better than the USDM piece therefore making a bit more power. That says alot for Honda header. Personally I like the OEM piece its not the "cast iron" door stops of the past that were on the D series engines. Man anything would be an upgrade compared to that piece. The stock header as posted in pics, looks very nice, it doesnt look all that bad, sure it can be improved a bit, but is 300+ dollars worth 1 hp? IMO use the stock unit , or try to resource a used header from an A2 (probably a bit better than our unit, but thats just speculation), save some money do the basics and then the hondata flash... IMO -Joe :)

[JSIR]

well you really can't say adding a header will give you 1 hp, or 5 hp or 0 hp, the final power numbers only start to manifest themselves once you have a series of mods like an intake, followed by some form of exhaust upgrades all combined together -whether that is just a midpipe, header, or full cat back exhaust. That is how you achieve an optimum level of flow through the engine on these k20's.

The reason I say this is because of what we have observed, consider these results:

Stock Civic with just a cat back exhaust makes 0 hp, if not a loss.

Stock Civic with just a mid-pipe (stock muff) - makes 0 - hp.
Same Civic then adds a header - makes 0 - hp.
Same Civic then adds an intake - makes 12hp all at once.
Same Civic then removes muffler and runs open pipe - 0 hp gains.

Stock Civic adds an intake - makes 4 hp
Same Civic then adds mid-pipe & header - gains a further 15hp !

Then we have Joe's Civic that makes good power with an intake and cat-back exhaust, similar to a Civic with intake, header, and mid-pipe (stock muffler)

Magazine info:

HCI magazine found 4 hp gains with just a header upgrade to stock Civic.

Import Tuner found less than 2 hp gain with cat back exhaust on a stock Civic.


As you can see there is no rhyme or reason as to "which" part adds "how much" hp. The numbers only start to make sense when you view them based on a group of mods. They don't really make much sense when you view individual mods. Hence the theory that power is maximized when you achieve an optimum level of flow. Whether that flow is achieved with a header or full exhaust may not matter (on a car that already has an intake). But you can get an inexpensive header and midpipe for less than the cost of a full cat-back exhaust and if you prefer quiet exhausts (like myself) this may be a better choice
With Joe's Civic making good power without a header, that combination may just be achieving a very good quality of flow, adding a header to that mix might not add any power, probably not needed.

The stock Si header is okay, I agree that it is an improvement over past b-series cast iron headers, but she still isn't pretty if you get a close look at the collector and primary connections. I am surprised it flows as well as it does with the odd selection of tubing sizes and piping connections at the colllector and head flange. The RSX-S header is an improvement over the Si header, in how it is sized and assembled. The RSX Type R JDM header is an improvement over the RSX-S header in design. But I think you need the RSX k20a2 engine to take advantage of these better headers as the k20a2 flows more air with higer rpms.

I think that is enough rambling.:confused:

[natesi]

Excellent points.

[JSIR]

yeah we still need to see some more combinations of parts. It would be nice to see someone do an intake, cat-back exhaust, and header mod in that order with dyno testing in between. That would give us a good picture of how the parts affect performance as they are added in sequence.

[Jeremy R]

Nobody ever mentions that Comptech got 11 WHP out of just a
header and a cat-back for our cars. And if you look at the Dyno,
it seemed to get more power throughout the whole RPM range.
Now I know Comptech cost out the wazoo but still.
Since, I don't know much about this stuff, or have access to Dyno's and testing other midpipes, it might be my best bet just
to save up so I can get it right the first time.

[ssvr6]

Originally posted by Jeremy R
Nobody ever mentions that Comptech got 11 WHP out of just a
header and a cat-back for our cars. And if you look at the Dyno,
it seemed to get more power throughout the whole RPM range.
Now I know Comptech cost out the wazoo but still.
Since, I don't know much about this stuff, or have access to Dyno's and testing other midpipes, it might be my best bet just
to save up so I can get it right the first time.


I'd like to see independant tests of comptech's products. In fact, I'd like to see the same for a large portion of what's out there.


Steve

[JSIR]

I dont believe Competch header and exhaust will net you 11whp without some type of intake upgrade. In their testing they must have opened up the intake system somehow even though it isn't mentioned. After opening the intake, adding the header and exhaust could get you close to 11whp in some testing , but that can be said of other more inexpensive brands as well.

I am anxious to see their icebox intake which is supposed to be out in the next two months.

[myeverlovinsir]

I agree fully with realizing gains when all of the components (I/H/E) are installed, each part is crutial. Otherwise don't expect any gains when you run to the dyno after only putting on an exhaust. But that should be clear now. Joey, I hope your shop mod of the stock intake flops, so I can see the Icebox on the dyno. j/k

Glen

[JSIR]

he, he ,he, that is a possibility, I don't expect my home made icebox to dyno quite as good as the short ram intake I was running, so it just depends on how much hp I am willing to sacrifice for a simpler intake system. If it sacrifices to my hp then the Icebox may be on its way , and of course it will get dyno'd.

[TrippZ]

I wouldnt say its a new record. I can get it for $65 no tax, and if i bring about 2 more people iget a 10% discount. Tee hee. Anyone in dallas wanna go get a midpipe with me?