VincentHill
Needs a life
Posts: 6520
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posted July 18, 2007 09:09 AM
DM, you should know! But I know that cam timing / Cams can put a big hole in the Power Curve amd from moving the timing around, I have changed a Hole to a Dip !
Torco Race gas seems to be more stable over time than VP
Karl, I have yet to taste any gasoline that I liked!  (Trust me I have sucked enough in my life to know!) 
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Made History @ Daytona and still one fast old man!!
  
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entropy
Moderator
Posts: 8671
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posted July 18, 2007 09:36 AM
quote:
...Trust me I have sucked enough in my life to know!)
quick!!!!
i gotta quote Vince and preserve this shocking admission before he realizes what he "said" 
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This moderator uses moderation in moderation
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tcchin
Zone Head
Posts: 867
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posted July 18, 2007 12:04 PM
The flat spot is caused by resonance in the ports, airbox and exhaust. Changing spark timing or fuel mixture won't have any bearing on the acoustics of the motor. Two stroke kart applications used to employ an adjustable expansion chamber to address a similar problem, but short of that and/or an equivalent device on the intake side and some kind of variable valve timing to compensate, there's no way to change the resonant frequency of the engine.
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted July 18, 2007 12:27 PM
It's the nature of the 4 into 1 on a flat crank four. There's always a spot (or two if you can rev it to the next spot) where the exh flow plugs itself up. That's why 4-2-1's, duplexes, 2-1's etc. are used.
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tcchin
Zone Head
Posts: 867
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posted July 18, 2007 02:17 PM
Exactly. Even within the various configurations (e.g., a 180 degree 4-2-1 and a 360 degree 4-2-1), there are dips and lumps that are a function of the design and interaction of the exhaust system components.
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psycho1122
Pro
Posts: 1608
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posted July 19, 2007 06:27 AM
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You say PSYCHO like it's a BAD thing!!
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TRNorBRN6001
Needs a job
Posts: 2021
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posted July 19, 2007 06:49 AM
 Edited By: TRNorBRN6001 on 19 Jul 2007 08:00
Too funny Karl! I'll have to remember that one when Andy says that.
I did get to hang out at Andy's shop and listen to a few stories before
having to head out to my seminar.
If it stops raining today I'll be taking it out for a ride with my bro
on his 1397 Busa. We might drop by Bike Night and visit with
JC's VTX and Victory crew. They always seem to be there with
more and more mods. One of them has a small home grown
hairdryer on his twin, I think it puts out around 170 HP.
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TFA 200MPH CLUB MEMBER!
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VincentHill
Needs a life
Posts: 6520
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posted July 19, 2007 09:47 AM
Karl, You have been Hanging with "Harry" too much!! We all know he needs help but we thought you were better Off! Now we know!!
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Made History @ Daytona and still one fast old man!!
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supra5677
Pro
Posts: 1279
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posted July 19, 2007 10:29 AM
I'm not convinced you can't get that dip out of there.. why don't you just take Ridgeracers ECU go that specific spot and twicke the fuel and timing in that spot..
supra
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tcchin
Zone Head
Posts: 867
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posted July 19, 2007 10:56 AM
Because fuel mixture and ignition timing don't address the root cause. Unless the internal pressure, temperature, density or physical layout/dimensions of the intake, exhaust or head can be changed on demand, there's no way to change the dynamics of the flow in and around the ports in the cylinder head. If the exhaust hits a harmonic at half redline that stuffs the combustion chamber full of exhaust gases, there's no way to add more oxygen to the mix to bring the energy density back up.
It sounds like this is not a street motor anyway, so if the rider is spending much time down at 6k, he's already lost the race.
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supra5677
Pro
Posts: 1279
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posted July 19, 2007 01:35 PM
variable valve timing!!
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tcchin
Zone Head
Posts: 867
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posted July 19, 2007 03:03 PM
Edited By: tcchin on 19 Jul 2007 16:04
See text nine messages up. Also note that installing VVT may be more involved that replacing an exhaust system.
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted July 19, 2007 03:55 PM
You may remain unconvinced Supra. It's your perogative.
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supra5677
Pro
Posts: 1279
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posted July 20, 2007 06:51 AM
well it was proved that the 2000 zx12r ecu is cuts fuel, ignition, and ram air 700 rpms before the limiter...
something tells me that 103/106 will get that dip out of there...
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Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
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posted July 20, 2007 07:31 AM
Edited By: Y2KZX12R on 20 Jul 2007 08:35
supra, have you ever turned on and off the garden hose very quickly and saw the hose jerk back and fourth? Ir sometimes if the pipes in the house arnt seccured as well as they should be you hear the same thing in the house, and its called water hammering.
Well, moving air in a pipe does the same thing but with lwss force because the moving body has less mass. but in principal its the same effect.
If you had a pressure gauge on the hose and had a way to control the opening and closing rate of the hose nozzle you would see pressure spikes and also negative pressure spikes. These would vary in intensity depending on the rate that the hose nozzle was being opened and closed. But the mass of the water doesnt change but its mean velocity does.
So as you played with the opening and closing rate and watched the gauge you would see that at certain opening and closing rates the water would still be trying to move thru the valve while the valve was closing and opeing. At some point the valve would cycle open and closed before the water could respond fast enough. You would see different oscillations at the pressure meter at different opening and closing rates.
Well the samething happens in both the intake and exhaust columns of air. They have mass and inertia and take a certain amount of time to start to move and to stop moving.
Its great when the air column moving towards the back of the intake valve is still trying to move past the valve while the valve is closing. This causes an increase in volumetric efficiency like supercharging. But at certain rpms the column of air is slowing or has just stopped moving just at the wrong time and is out of phase with the valve timing. And were not talking a few degrees of camshaft rotation. The net result is loss of VE and in extreme cases port reversion. Port reversion can do several things. It can, on carburated engines cause a "double" (not really double) fuel charge. It can show up as rich or lean areas on a fuel curve map. however adding or subtracting fuel does very little. Why? because the improper a/f ratio you see is just the symptom, not the problem.
Reversion can also cause exhaust contamination, over scavenging, under scavenging, and a few other oddball issues.
The good thing is that this phasing in and out of the intake and exhaust tracts only causes problems at certain rpms and the engine revs right thru quickly.
The real problem is when on a street or race engine the "problem" rpm area is in a spot where you need smooth power. Like coming off a corner or cruising on the highway right in a bad rpm spot.
This is exactly why the manufacturers have been putting on these fancy computer controlled (or not) valves in the exhaust. It reduces these bad spots in the tuning of the intake and exhaust systems. But the real reason they do it is for emitions. not only does the rider feal a flat spot in the torque curve but the federal government sees it as bad emitions areas and has mandates them removed to pass emitions. The problems were always there but the manufacturers never cared and didnt put the valves on there untill they had to.
So, the bottom line is that some pipe designs make better power at different spots with more or less reguard for the places where they dont work well.
If someone is buying a 4-1 sidewinder then that person doesent (or shoudnt) care about a flat spot at some lower rpm where the pipe doesnt perform well. It wasnt designed to work well at that rpm.
So timing and fueling cant always mask an issue with a certain pipe or intake tract design.
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Y2KZX12R
CompetitionCNC.com
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TRNorBRN6001
Needs a job
Posts: 2021
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posted July 20, 2007 07:39 AM
It actually is a street bike that will get to see a little Texas Mile action and maybe a
couple periodic runs at the 1/4 or 1/8 Mile strip. Even with all the rain it has seen a good
500 miles so far. It has been rather cool here lately only in the 90's so no over heating
problems. I do have a custom radiator I wil be slipping on soon to handle the usual Texas heat.
I believe the cams are not that far off from those numbers and what Muzzy recommends.
PS: Special thanks to Johnny Cheese for the build and tune, Mr. Hill for parts I wanted to
put on my mantle instead of in the bike, Mad Mike, Ryan "Osti", Karl "Entropy", Muzzy and
the rest of the BikeLand crew.
Hope to hit 200 in October with all the other 12's
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TFA 200MPH CLUB MEMBER!
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supra5677
Pro
Posts: 1279
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posted July 20, 2007 03:12 PM
got it Y2 
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psycho1122
Pro
Posts: 1608
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posted July 21, 2007 06:48 AM
Good Job Y2K!!
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You say PSYCHO like it's a BAD thing!!
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Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
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posted July 21, 2007 01:19 PM
quote:
Good Job Y2K!!
Just trying to help.
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Y2KZX12R
CompetitionCNC.com
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VincentHill
Needs a life
Posts: 6520
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posted July 21, 2007 06:44 PM
quote:
It actually is a street bike that will get to see a little Texas Mile action and maybe a
couple periodic runs at the 1/4 or 1/8 Mile strip. Even with all the rain it has seen a good
500 miles so far. It has been rather cool here lately only in the 90's so no over heating
problems. I do have a custom radiator I wil be slipping on soon to handle the usual Texas heat.
I believe the cams are not that far off from those numbers and what Muzzy recommends.
PS: Special thanks to Johnny Cheese for the build and tune, Mr. Hill for parts I wanted to
put on my mantle instead of in the bike, Mad Mike, Ryan "Osti", Karl "Entropy", Muzzy and
the rest of the BikeLand crew.
Hope to hit 200 in October with all the other 12's
ME Too!! Now have you done the Gas Tank Mod so there is room for "YOU" on the Bike?? Trust me, doing that will not beautify you bike to the eye, but to the Air it will be slippery!
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