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Discussion Starter · #1 ·
Not to be spiteful but it was pointed out to me by another forum member that someone had Dyno charts of a stock Z400 and then one with the same Z400 with the only differance being the "peashooter" had been drilled out.

I am willing to admit that I am wrong if someone can post actual Dyno charts showing that this practice will GAIN Horsepower and not just Racket!
 

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I've drilled mine out and did not really notice any gains in the seat of the pants dyno. I did mine strictly so I could hear my quad while riding with other quads. It doesn't make it much louder, I definately wouldn't say "more racket". Not near as loud as an aftermarket pipe, but can hear it reving when near piped quads as long as they aren't too close.
Hey to each his own if you don't like it don't do it. Some of us may not want to turn loose with the cash for a pipe or haven't made up their minds which one to get.
 

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Discussion Starter · #3 ·
Corpsie was so kind as to point me to a thread on here that showed that someone had Dyno'd there Z after going to all the trouble of hacking out the "peashooter" only to find out that the guy had also removed the airbox lid, installed a Uni filter and rejetted the carb. He claimed that the Dyno showed a 3hp increase.

Well I thought that with the way my Z ran after just doing the airbox,filter and rejetting that it felt like it had increased the hp. Then I remembered this other site that Dyno'd a Z STOCK and then with the lid off and the stock filter and rejetting. Below is a link to the proof that you are pretty much wasting your time and effort as well as a possible fine if stopped by some ranger and he sees that you have hacked your endcap. For nothing but noise! Sorry if I offend any one but if we want to keep public riding areas open I think that it would be in our best interest to do things correctly and for a gain. Remember when you see the chart that they were using a stock filter and had the screen in the intake tube and with my set up I am running a K&N filter ,Outerwear, NO screen, NO lid and rejetted with a 155main. Enjoy!

http://www.off-road.com/atv/reviews/quads/...yno-report.html
 

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As long as the spark arrester remains in-tact, the ranger won't care. It's just the endcap, not the SA that's being removed. And as far as noice, I bet there's just as much noise added with the airbox removed than with the endcap.

It does help.. more free-flowing air out the pipe always helps, especially when you're letting more air in.

And where in this link does it show no affect? Or the ranger will get you?
 

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Discussion Starter · #5 ·
I'll try to keep this real simple.

They gained 2hp by just removing the lid and rejetting with the stock filter and the stock non-hacked exhaust.

Now, if they were to have used a K&N filter with Outerwear, which breathes much much more than stock and rejetted for it they might have seen 3hp or more without touching the exhaust! Since I have an open top airbox with K&N filter, Outerwear, and a 155 main jet I am willing to bet that I am seeing the 3 or more HP increase without hacking the exhaust.

Now, in the thread that Corpsie showed me the guy had done the filter, no lid and rejetted then he hacked the exhaust and he only Dyno'd 3HP! Seems that to the average person that this would show that hacking the exhaust had nothing to do with making the 3HP!

I never consider the theory "that they won't ever catch me" when it comes to being responsible in a area that affects the whole ATV community! Since you guys are using a holesaw and Dremel tool, I am sure that it would raise an obvious visable clue that the exhaust has been modified and therefore would be suspect.

The POINT that I have been trying to make is that you guys who think you are gaining anything by doing this are mistaking noise with actual Horsepower!

CAN YOU HEAR ME NOW? LOL!
 

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QUOTE
I am sure that it would raise an obvious visable clue that the exhaust has been modified and therefore would be suspect.[/b]
It's not going to be visable unless he's standing behind your quad inspecting it. The end-cap points downward and the pea-shooter is actually inside the tip of the end-cap. I ride in the dunes so mods like that wouldn't matter anyway.

? for ya. Where on the dyno does it say they did or did not use a stock filter for the dynojet kit? If you gained 3HP out of your K&N and no lid w/re-jetting...how? That's a 10% increase in HP. I've done the exact same mod you did(except I'm running a 152.5 main and a 25 pilot). I didn't notice that much. I noticed a very little increase....not 10%. I think maybe 1HP out of the mods we have. You have to remember, these results are going to differ by location regardless of the dyno used. I'm not trying to be a smart a$$ or anything...just trying to get some answers, because I've been thinking of doing this mod for a while.
 

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The mod is not noticable from the rear on mine. The smaller diameter pipe is spot welded on the inside to the larger one. I just ground the spot welds away with a rotary file and smoothed with a sanding drum. The noise increase is not much at all very little, just to where you can hear it with the helmet on. I don't want a loud exhaust either since we also have horses. The spark arrestor stays intact, that is all that is require where I ride at. That is one reason why I havent gotten a slip on yet, they all seem a little loud to me and where I ride at. If all I did was race or trail ride I wouldn't worry about it but I do use it quite a bit around here.
I just can't see taking the chance of running without an airbox lid in the places I ride at. If you run in the dunes, desert, all dry trails or on a track it would be a different story. I will keep my lid intact and on, where I ride at.
As far as you gaining any hp, yes maybe you are but I'm sure it isn't as much as what you think. It is true that you are creating an oppurtunity for more air intake and a smoother flow. But this will also be limited by how much air you can also move out the exhaust. The exhaust has a 5/8" dia hole for all that air to travel out in stock form. So you still have a restriction in your air flow. You would probably see a very large gain in hp if you would install an aftermatket slip on exhaust or full system. This would even out the flow by reducing restrictions on the intake and exhaust, creating a much freer flow through the engine. You would most likely see a decent increase by removing the restrictive pea shooter in the stock exhaust. Of course not near as much as if you installed an aftermarket system.
I think you may be confusing horsepower with $$ spent. :) But in all fairness you may be going a little faster since you lost a little weight in the change for that airbox. :wink: LOL.
 

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