WHY???????????

[Alphamazing]

Lunchbox only, I dynoed at 42HP. That's a 5% increase or more over a stock GS.

[TragicImage]

Lunchbox only, I dynoed at 42HP. That's a 5% increase or more over a stock GS.

but what was the increase over YOUR stock dyno?

[Alphamazing]

Lunchbox only, I dynoed at 42HP. That's a 5% increase or more over a stock GS.

but what was the increase over YOUR stock dyno?

No idea, as I didn't do a stock dyno, but show me a stock GS making more than 40HP.

[TragicImage]

well... what I was trying to say was


Each GS makes its own unique power.  One GS might make 39hp stock and the next makes only 37hp in stock trim, in the same conditions.... although I doubt the difference is that great.... no two GS's are making the same power.

[Wrecent_Wryder]

d4

[Gisser]

let's see what the other side has to back up their oft-stated position..  if anything.

Well, the best evidence is presented at the top of this thread.  The OP put the K&N lunchbox to the test and he got spanked by reality.  Dazed and confused, he is left pondering the question....WHY ? ? ? ? ?

IMO, the AlphaFire dyno run (41.7 not 42) lacks credibility.  The claim is that peak power now comes in a at 9500 RPMs rather than the sub 9000 RPMs of a stock engine which I find to be highly suspect based on other pipe/filter dyno runs I've seen which did not appreciably budge the power peak zone.  All this using a main jet (135) which I believe is at least 3 sizes lean. 

To further muddy the water, the Alpha run was also made with a 14 tooth CS sprocket. 

Alpha was advised to do before & after dyno runs but chose to forego that and is now perfectly satisfied to accept and defend numbers which validate his aspirations without question.  Of course. 

Hardly bears worth mentioning that 2 horsepower is within the margin or error between equipment and conditions.

As explained on previous occasions, the need to rejet significantly is not ample evidence of much better airflow.  That is the illusion that fuels the K&N myth. 

The significant rejet is necessary to compensate for the increase in air pressure in the intake tract, not an increase in air flow into the engine.  The increase in air pressure, caused by the removal of the airbox, significantly weakens the fuel draw through the main jet circuit--the Bernoulli effect as it applies to carburetion. 

After all, you didn't really think--all else being equal--that going up to 10 sizes larger on the main jet would only result in a net increase of--at best--a couple horsepower?  That's never made any sense.

I'm sure with careful tuning the OP can regain the acceleration that he has lost but there will never be the night & day difference that the "butt dynos" claim to achieve compared to a stock GS500.  Not by any objective measure.   

[Alphamazing]

IMO, the AlphaFire dyno run (41.7 not 42) lacks credibility.  The claim is that peak power now comes in a at 9500 RPMs rather than the sub 9000 RPMs of a stock engine which I find to be highly suspect based on other pipe/filter dyno runs I've seen which did not appreciably budge the power peak zone.  All this using a main jet (135) which I believe is at least 3 sizes lean. 

That's 41.7 with a lean jetting setup. If I got it dynoed now (with the 137.5) I'm sure the peak power would be higher. Also, it's know that removing the airbox tends to take away from the low end and add to the upper end of the RPM range, possibly producing a higher peak power RPM. With my 137.5 main my plugs are a very nice shade of lightish brown.

To further muddy the water, the Alpha run was also made with a 14 tooth CS sprocket. 

No it wasn't, it was done with a stock 16T sprocket. And even if it was that wouldn't change anything since the sprocket is simply a gearing change. Gearing changes simply change how the power is delivered, not how the power is made. You're still dealing with the same torque and HP curve, just the gearing is lower.

Alpha was advised to do before & after dyno runs but chose to forego that and is now perfectly satisfied to accept and defend numbers which validate his aspirations without question.  Of course. 

I'm sorry I don't have enough time or money to do comparisson runs on a bike. $40/dyno run is a lot for a poor college student on a budget. Couple that with taking the time to remove the filter, rejet the bike back to stock, dyno it, change back to the lunchbox, rejet again, and then dyno AGAIN, as well as having to drive for an hour and a half to get to the nearest place that will do a dyno run... Yeah.

Hardly bears worth mentioning that 2 horsepower is within the margin or error between equipment and conditions.

In every single dyno run ever performed on a stock GS that I've ever seen, in every magazine article, in every personal dyno run done by pretty much anyone on here, I have never, I repeat NEVER seen a dyno run of a stock GS that produced over 40HP.

After all, you didn't really think--all else being equal--that going up to 10 sizes larger on the main jet would only result in a net increase of--at best--a couple horsepower?  That's never made any sense.

I went up 3 sizes. Compensating for the naturally lean condition of the GSes jetting, that's actually pretty normal.

[Gisser]

That's 41.7 with a lean jetting setup. If I got it dynoed now (with the 137.5) I'm sure the peak power would be higher.

Shoot, you must up to, what, 45 horsepower now? 

No it wasn't, it was done with a stock 16T sprocket.

Sorry.  I was searching for your dyno results and came across an earlier sprocket change.   

In every single dyno run ever performed on a stock GS that I've ever seen, in every magazine article, in every personal dyno run done by pretty much anyone on here, I have never, I repeat NEVER seen a dyno run of a stock GS that produced over 40HP.

From my perspective, that speaks to the quality of your dyno source.  Dang HD dealers.  That far off, huh?

I went up 3 sizes. Compensating for the naturally lean condition of the GSes jetting, that's actually pretty normal.

No, it's not.  To jet for the K&N lunchbox, most of the pre Y2K GS500's are going up several sizes larger from a starting point 4 or 5 main jet sizes smaller than your stock main jet.

Any stock GS500's in the Dallas-Ft.Worth area you can race?  Take it from the OP, this is not the time to be racing for pinks!   

[Wrecent_Wryder]

[e4

[scratch]

The reason for having an airbox is to provide a still-air pocket for the carbs to draw on.  A still-air pocket is at atmospheric pressure and is not influenced by turbulent air causing the 'pressure' to fluxuate.  The carbs (or, rather the pistons pull) can flow a smoother and higher(faster) airflow from a still-air pocket than from turbulent air.

The increase of air pressure in the intake of a carburetor is caused by this 'turbulent' air, and interupts the smooth flow of fuel through the jet needle into the venturi.  It pressurizes the venturi instead of allowing a vacuum.  Stopping the flow of fuel.

I'm not sure if this is related, but doesn't a "Flowbench" check how much air can be flowed through the head?  Does it also check the flow through a carburetor?

[Alphamazing]

That's 41.7 with a lean jetting setup. If I got it dynoed now (with the 137.5) I'm sure the peak power would be higher.

Shoot, you must up to, what, 45 horsepower now? 

No, but I'd bet it is around 42. 3/10 HP is entirely possible by correcting the air/fuel ratio.

No it wasn't, it was done with a stock 16T sprocket.

Sorry.  I was searching for your dyno results and came across an earlier sprocket change.   

Regardless, even if I had it dynoed with the 14T the graph would have been the same. Gearing changes change just that, the GEARING. You're still dealing with the same power and torque curves.

In every single dyno run ever performed on a stock GS that I've ever seen, in every magazine article, in every personal dyno run done by pretty much anyone on here, I have never, I repeat NEVER seen a dyno run of a stock GS that produced over 40HP.

From my perspective, that speaks to the quality of your dyno source.  Dang HD dealers.  That far off, huh?

Harley dealers typically deal with low horsepower machines. Hell, most Harleys make under 100 HP, why should a 40HP GS be any different? Plus, it's a DYNO. It doesn't care about what type of bike it is.

I went up 3 sizes. Compensating for the naturally lean condition of the GSes jetting, that's actually pretty normal.

No, it's not.  To jet for the K&N lunchbox, most of the pre Y2K GS500's are going up several sizes larger from a starting point 4 or 5 main jet sizes smaller than your stock main jet.

Any stock GS500's in the Dallas-Ft.Worth area you can race?  Take it from the OP, this is not the time to be racing for pinks!   

And most of the pre-'01 (not pre Y2K) GS500s are probably running rich. Most people jet off what srinath says, and srinath jets rich.

And why would I go to Dallas/Ft. Worth? I live in Austin.

[rangerbrown]

FYI, my bike made 38 HP and 23 TQ peak at 9500 rpm, no mods what so ever


next time i am at the gap i will do another, i would bet 10$ i am making at least 40-43 hp and 25-28TQ

[CirclesCenter]

You say you jumped him off the line.  You probably didnt keep your rpms high enough.  You can just someone off the line but if you dont run the clutch long enough the rpms will drop after the jump and youll be going slow just with a fast jump at the beginning.  Thats waht I think you did because you said he caught you by second gear.  If he kept his rpms alittle higher but launched slower he could have still beat you cause he was higher in the rpm range and had more power, but you just jumped the bike and then had lower rpms which is bad for drag racing.  I say rider error.

I'm going with this theory.

BTW Gisser, do you even know anything about dyno's? It's not like HD made the damn thing, they just bought it.

Also, Gisser do you even understand internal combustion? Because you seem like you might need to go back to Auto I.

[bettingpython]

FYI, my bike made 38 HP and 23 TQ peak at 9500 rpm, no mods what so ever


next time i am at the gap i will do another, i would bet 10$ i am making at least 40-43 hp and 25-28TQ

You power hungry squid you 

[natedawg120]

faster in acceleration, slower in speed.

that makes no sence it would only have a smaller top speed and since you cant redline 6th that wouldnt mater

i think you may of stuffed up the rejet

As I understand it, which is usually pretty damn accurate..
You have a slower top speed PER GEAR... not just over all... Where as you can go 44mph in 1st gear with a 16t.... you can only go 39mph in 1st with a 14t.

+1 Tragic

[metallic5spd]

after reading through all the nonsense, any suggestions on what to look at first??  i will do the trade and ride and see how that goes to PROVE that its not rider error.  i already had that in mind.

[galahs]

I do not agree for 1 second that the Stock Airbox is better for peak power than a K&N RU2970 (Lunchbox airfilter)

Why?

Because the Stock Airbox has a tiny filter and only a small opening to allow air into the airbox.

The smaller the filter medium, the more resistance.

The smaller the opening, the less volume of air can be sucked into the engine (higher pumping losses).



But I do agree that the air box would probably flow better at lower rpm's, as the air would have to travel faster through the small airbox opening to fill the cylinder than from a low restriction filter like the RU2970.

But as the RPM's rise the sall opening would become more and more restrictive and the volume of air required to maximise horsepower would not be achievable.


Also, the air in an airbox is not stagnate air! Air flow in an airbox is linear, hence why the bike is so much quieter when fitted with an airbox.


The only other thing that could be a factor is heat soak. Exposed pods and lunchbox filters would breathe in more hotter air radiating off the engine block and cylinder heads than an airbox fitted bike. The hotter the air, the less oxygen it contains. Less oxygen to mix with fuel to burn equals less power!

but this really would only be a factor when the bike is not moving.

[TragicImage]

uhm.... I don't think it "Hotter Air = Less Oxygen"

I think its hotter air is "Less Dense"  i.e. Fewer of ALL gasses..... but yes, that would equal less oxygen, but in the same ratio as cold air....






YEA! I KNOW I DIDN'T SAY THAT WHERE ANYONE CAN UNDERSTAND IT! BLOW ME!

[plusultra]

Question:
Did you adjust the mix screws??  Not the idle screw, the mix screw.

[rangerbrown]

whats you 0-60 time mines about 3-4 sec but i dont knwo for sure. but it is fast as shaZam! with the 14t frotn sprocket but the shifts are very close together