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exhaust port (Read 2594 times)
bill67
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Re: exhaust port
Reply #30 - 06/09/10 at 04:10:28
 
Earlytimz how must does that gain you in power and gas mileage?
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Re: exhaust port
Reply #31 - 06/09/10 at 05:19:10
 
Good info.

I just want to add one more thing.  Don't think of opening the exhaust port as a RACE mod, it is an EFFICIENCY mod.
It is as if you took off your header pipe and found a big rock stuck inside, which you would naturally remove becasuse it is interfering with the exhaust getting out and would certainly cause a decrease in efficiency; or power.  Remove the rock and the engine works better and makes the power it was really designed to do before all of those rocks were thrown in by "gov't b'crats" at the EPA.
Rocks in the carb, rocks in the exhaust ports & header, rocks in the muffler...etc.
When I did the first mods on my Savage I removed those rocks and  cleaned everything up a bit; the result was that power went up to 42-45 hp at the rear wheel.   A stock LS650 makes about 25 hp at the rear wheel.
I had more power AND torque everywhere... from idle to a maxed out redline of 6500 rpm and it still wanted to do more.

Everything I did to my engine was to increase efficiency, until this last rebuilt...this time I went beyond that, but point is that there are fairly easy things that can be done which enable to engine to work easier and will yield more usable torque with which to play or to use when passing that big truck on an uphill highway or mountain road.

You will really like the result.
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earlytimz
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Re: exhaust port
Reply #32 - 06/09/10 at 06:39:17
 
Hey Bill, I can't really put a number on it. I don't have a dyno or any fancy test equipment. It's just a matter of letting your engine work easier. I like the way Lancer described it with the big rock stuck in the way. You can also look at it like trying to blow through a coffee stir vs. a big straw. Your lungs are gonna force the same amount of air through both, but which one is faster & takes less force? Which exhaust port is gonna let your engine rev faster, with less resistance?

LANCER wrote on 06/09/10 at 05:19:10:
I had more power AND torque everywhere... from idle to a maxed out redline of 6500 rpm and it still wanted to do more.

-And I bet it revved to the 6500 redline a lot quicker too!!
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bill67
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Re: exhaust port
Reply #33 - 06/09/10 at 08:01:46
 
It will help the high end and get less mpg.And kill the low end power.
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william h krumpen
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Re: exhaust port
Reply #34 - 06/09/10 at 08:11:29
 
Okay, I'll bite...I'm thinking this might be fun. If I take the header off and use a dremmel to take the lip off the exhaust what do I need to look out for?
I've never come anywhere close to modding an engine like this and my wrenching skills are basic at best (but everyone else calls me a "mechanic"...not even close!)

"It will help the high end and get less mpg.And kill the low end power."
Bill, I'm wondering...how do you qualify that statement? Have you tried it?
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Re: exhaust port
Reply #35 - 06/09/10 at 08:17:24
 
Do it and you will know too.
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william h krumpen
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Re: exhaust port
Reply #36 - 06/09/10 at 08:23:20
 
Does that mean you've done it???
I'm a mile high here, I'm thinking I could use whatever extra air I can get but I don't want to lose out on the low end torque.
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bill67
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Re: exhaust port
Reply #37 - 06/09/10 at 08:27:14
 
I had a snowmobile professional ported it killed the low end, A little bit of help on the high end, I never did it again and wouldn't.It also killed the gas mileage.
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Re: exhaust port
Reply #38 - 06/09/10 at 08:42:20
 
Bill,

Was that snowmobile engine by any chance a two stroke engine?  
And jest for grins what sort of two stroke oil did you use in it, BTW ....

Grin   Grin   Grin  

I knew you picked up on Klotz from inside the two stroke world from somewheres in your past.




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Re: exhaust port
Reply #39 - 06/09/10 at 08:46:48
 
Your right on both counts.
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william h krumpen
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Re: exhaust port
Reply #40 - 06/09/10 at 08:47:35
 
Your snowmobile was probably a 2-stroke. 2-stroke engines use a finely tuned exhaust and are much more sensitive to mods... Plus they have no bottom end to start with, they are high revving engines. Think "Power Band"

We used to port the crap out of 2-stroke banshee & blaster heads. Did it help the bottom end?? Hell no, but when you open that sucker up and hit the power band you know you've done something good!
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Re: exhaust port
Reply #41 - 06/09/10 at 08:48:22
 
OldFeller beat me to it...
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bill67
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Re: exhaust port
Reply #42 - 06/09/10 at 08:57:45
 
My young fellow 4 cycle motorcycles rev higher than 2 cycle,I've had 3, 2 cycle motorcycles.
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william h krumpen
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Re: exhaust port
Reply #43 - 06/09/10 at 09:04:53
 
3 cycle?? or 3 cylinder?

EDIT: I re-read your post. I think you're saying you've had three, 2 stroke motorcycles... I see that now.

I'm gonna have to disagree that a 4 stroke engine is higher revving. 2 strokers only have 1/2 the revolutions to make a complete cycle. They rev twice as fast.
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Re: exhaust port
Reply #44 - 06/09/10 at 09:40:06
 
Too much of anything can cause a problem... Porting, jetting, intake air, unbaffled pipe... whatever....
But, from the look of that exhaust port, with that shelf obstruction across the top of the port,... I doubt it's possible to get too much flow out of there...
I softened mine up a little, years ago,... with little effect, but I think I'll go back in and do a proper job soon...
I don't touch intake ports,... roughness in there is supposed to be beneficial... (that's what I've been told,..and I always do what I'm told  Huh)...
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Ludicrous Speed !... ... Huh...
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