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Discussion Starter · #1 ·
my set up is:
mugen 4-2-1 header,
decat,
mugen catback,
AEM cai,
type R TB,
skunk2 IM,

readings are from the flywheel.



does this seem about right for the mods ?
 

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Wow I have like...-24whp. :D Nice!
 

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your setup is fighting itself... and you've got a very bumpy torque curve to show for it.

that header and CAI like the lower revs, the IM and TB like the upper. pick a powerband location goal and run with it.
 

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DaBoyNBlu on Mar/31/04 said:
your setup is fighting itself... and you've got a very bumpy torque curve to show for it.

that header and CAI like the lower revs, the IM and TB like the upper. pick a powerband location goal and run with it.
Not to get off topic, but how can you tell which component likes which part of the band when all are in place during the run? I'd like to learn something here. Thanks.
 

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The design of the particular components. Check out the header design article.
This should answer your question about the header.
This should answer your question about the intake.
This article should help with your IM questions.
 

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I've read those articles, but do you guys just know every design like the back of your hand, or what? That just amazes me if so. I've made room in my brain for some car knowledge, but not that much.
 

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Discussion Starter · #13 ·
so i would be better off with a 4-1 header.

but i didn't realise that the AEM cai so only good at lower rpm, i thought a cai was the best for making power.

please explain.
 

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cai are better for low to mid-range power. For an upper rpm powerband, you would want a short ram intake. also a 4-1 header, or a hybrid 4-2-1 (longer primary and secondary runners) would be better for a high rpm powerband.
 

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From one of MD's posts in that link:

Longer pipes shift the max. filling efficiency to a lower rpm and shorter pipes or no pipe shifts the maximum filling efficiency to the upper rpm's.

It makes scientific sense from a fluid dynamics point of view :

A bigger diameter tube allows more air to go in but at a slower speed (more cross sectional area). The air flow speed needed to make peak volumetric efficiency occurs at a higher rpm compared to a smaller diameter tube.

A longer tube creates faster air flow compared to a short tube (i.e. more pressure differential from the opening to the TB end) and peak volumetric efficiency will occur at an earlier (i.e. lower) rpm. This is why a longer CAI has an advantage in the midrange over a short ram, regardless of intake temperature differences.
 

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Discussion Starter · #16 ·
"However, does a CAI make more power than a short ram with the same diameter and filter material? For folks with single stage runner intake manifolds and mega cams that can rev up to 9000 rpm or more, the AEM/Injen- style CAI actually stops making more power after 8000-8300 rpm . The gain in power for AEM that is quoted in the ads occur at the famous "AEM hump" and not in the upper rpms after 7000 rpm."

is it really going to effect me as im only reving to 8000 rpm ?
 

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i think my post has been covered by the previous.

i'd only add:
yes, i do know where different parts' designs move the power band off the top of my head. when you've been playing around with this stuff for 4 years, it just becomes second nature.


rules of thumb (take with a grain of salt, but they give a general idea):

--long [skinney] pipes help flow velocity, at the expense of quantity; extra high flow velocity does the most good in low rpm's, but chokes off in when high-flow is necessary (ie, high rpm).

--short [fat] pipes help flow quantity, at the expense of velocity; extra high flow quantity does the most at higher rpm's, but "floods" in the lower rpms.

these blanket statements work on both sides of a motor--header, intake, whatever. they're probably in an article somewhere on here.

so you've got the long skinney CAI pipe feeding the short fat "pipe" of the big TB and short-fat runner IM; they're working against each other.

and 4-2-1 headers have always been notorious for helping midrange, with the exception of the high-dollar new funky designs.
 

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if you've been following along in the "Which 1 is the Fastest?" series of quizes which pulls together all the ideas taught in the COMMoN TOPICS and Articles, you'd know that having "low end" power is absolutely a waste of time with small displacement inline 4 cylinder N/A engines using short gearing. The fastest combination is the one that co-ordinates the location of the powerband with the gearing that one has (assumning weight, aerodynamics, and traction is the same). If you get that idea and understand it as the first step in engine building, it really gives you a framework or structure to center your planning around.



so the second step in anyone's "education" in engine building is to know "off the top of their head" what designs and what specs do to the location of where the most power will come in. The other thing you pay attention to is how much flow you need to make a certain level of power (assuming cylinder pressures and ignition timing are adequate) and what specs or dimensions deliver those. Focusing in on intakes won't do it.


You don't learn these facts with short sound bite replies on honda forums. You learn it through digging through a lot reading and looking at power curves and trying them yourself. Those who work at it, get it. Those who don't won't. It's like anything in life: the people who work harder but smartly without cutting too many corners end up ahead of the herd.


I really didn't want to get into this guy's dyno too much since he needs a bit of timing and fueling cleanup and to open up his exhaust, if you look at the way the curve jiggles around and dies after 7000 rpm. But for the most part, the reason he's getting killed up top is because he has chosen parts that "give up" up top in exchange for a "better low-midrange".

The engine is a series of compromises that you choose based on your priorities and driving habits. The compromises are between breathing versus burning. You improve breathing and this hurts burn efficiency at some point. You improve burning and this hurts breathing at some point. You can't get aroung that fact even at the F1 level. The best compromise between those 2 is usually the most powerful engine (assuming equal frictional and pumping losses).


PS we have learned from the quizes that there is more than 1 definition of "fastest". Is it the 1/4 mile? Is it top speed? Is it how fast you accelerate while rolling in gear? Over what distances are we talking about? So if your priority is to have quick street car (over distances < 1/4 mile) and can accelerate well from 3rd or 4th gear while rolling along the highway to pass that truck in front of you on a 2 lane highway, the way you choose your specs (powerband) and tune is different than someone who wants a 1/4 mile or straightaway road racing car. And a person who is aiming for top speed may be slow at the 1/4 mile & street but win when it comes to having his car run at the Salt Flats or Desert.
 

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last point: if anyone is impressed by the 209 peak number and is basing their impression of the engine performance on a certain number WITHOUT HAVING A BASELINE COMPARISoN, then you've learned NOTHING from this website.

As we all know each dyno shop will calibrate their dyno differently. So 209 at this place may be 200 at another place (even if they both use SAE correction).

When looking at dyno sheets and making judgements on whether the parts package is good for you or not, always compare the AMOUNT OF CHANGE FROM BASELINE. Don't get suckered into being impressed by the absolute number which the beginner forums all do (and get into a droolathon).
 
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