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Vr1203
| | Posted on Friday, November 08, 2002 - 08:53 am: | 
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Lets say I built a engine with a really heavy FW ,use lead plugs or something. Balanced of course.Now at the start line in a drag race I'm going to see a lazy revving thing but who cares I'm just staging. The light turns green(really yellow ,go at the yellow!)I have all that inertia in the FW to get me through the flat spot/turbo lag, after that the turbo takes over and hold on! Will it work?
I'm asking because I'm getting into a rebuild this winter and was thinking about making the FW lighter but now I'm wondering. |
X1glider
| | Posted on Friday, November 08, 2002 - 10:57 am: |
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The inertia stored in the flywheel is only of use while maintaining a constant speed, the only use. Or if you're coasting to the next gas station!![:]](http://www.badweatherbikers.com/buell/clipart/proud.gif) It helps the rmp stay where it is. It will not help you get thru your turbo lag. The best way to get thru turbo lag is either always keep the rpms above the lag point or use an impeller vane that will afford boost at a lower rpm.
If you want to accelerate the bike, you have to accelerate the heavier flywheel too. In doing so the power created in the cylinders gets transfered to the flywheel not the rear wheel. A combustion engine is only about 60-65% efficient. Think about how that power is lost: friction, heat, vibration and the power robbing inertial masses. Cut and dry, if you want quickness, reduce those factors. |
Timbo
| | Posted on Friday, November 08, 2002 - 11:34 am: |
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Vr,
It sounds to me that you would want lighter flywheels to be able to spin the motor up past it's turbo lag. Heavier FW would likely cause the lag to last longer. I must say however that I have no personal experience with turbos though, and if I were you I would consult with those who do. If you can't find the info here, look to see what the automotive world does to overcome turbo lag. |
Jssport
| | Posted on Friday, November 08, 2002 - 12:11 pm: |
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I had always thought turbo lag had a lot to do with the length of the intake tract.
I've heard comments that the Aerocharger units for XL motors have no noticible lag as compared with units built in the 80's. |
Peter
| | Posted on Friday, November 08, 2002 - 12:27 pm: |
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Jim,
I think the closer that you can get the turbo to the heads, and the shorter you can make the boost tube, the less lag you will have.
If you look how they are setting the Japanese bikes up in this pic, you'll see that the turbo is very close to the exhaust side of the head.
PPiA |
X1glider
| | Posted on Friday, November 08, 2002 - 01:35 pm: |
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Peter I think the unit is so close to the heads is because there's nowhere else to put it.
Lag has more to do with the effectiveness of the impeller and velocity and pressure going into the impeller. The turbo doesn't work unless there are exhaust gasses turning it. The more air you push thru the exhaust and the faster you push it thru, the more effective the turbo is. If you can spin the impeller with lots of air in the lower rpms, you can remove some of that lag. The short stroke 12000 rpm bikes have a lot of lag, a long stroke big inch v twin pushes a lot of air and has less lag. Also, exhaust scavenging doesn't work in a turbo setup. There's a turbo unit in the middle of the pipes slowing the flow down. The lack of scavenging is overcome since the intake is pressurized with turbo boost. The best way to decrease lag is to use an impeller that turns easier with less air flow and a turbine on the intake side of it that sucks in air efficiently at that rpm. Either that or just keep your rpms up.
Turbos are desined to create HP. HP is a byproduct of rpm. If you are not riding in the upper rpms to begin with, you've wasted your money on a turbo setup. |
X1glider
| | Posted on Friday, November 08, 2002 - 01:37 pm: |
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Peter, how is your turbo S1 coming along? |
Peter
| | Posted on Friday, November 08, 2002 - 02:23 pm: |
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Bob,
My point was about the difference in location of the same turbo on the same bike. If the distance to the turbo is shortened, then so is the response time for it to react. Obviously then, if the boost tube is also shortened, then the time it takes to bring the inlet plenum up to pressure, is also less. Jim's bike has a long exhaust and a long boost tube, due to the turbo's location under the primary, hence my comment.
I think you are wrong about them only being mounted there because that's the only place they fit. I've seen them in a lot of places. I think that location, close to the head, is the most effective place for them in relation to lag.
Mine is going well. I've got about 600 miles on it now, so I'm starting to gently open it up.
PPiA |
X1glider
| | Posted on Friday, November 08, 2002 - 03:17 pm: |
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I see now. I figured since a UJM has so much plastic on it, that was the only place for it. I guess the only problem I have with the exhaust runner being so short is the extreme heat being pumped into the turbo. Not good for the bearings.
Exhaust gasses travel pretty damn fast. Do you really think 120 cm less will make a noticeable difference in the amount of time it takes to pressurize the plenum? 10 ms?
Glad you haven't been simply admiring your pretty guages and hoses. It probably takes some getting used to all that sudden power. Pics?
Cheers mate. |
X1glider
| | Posted on Friday, November 08, 2002 - 03:19 pm: |
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BTW Peter, do you think all that extra intake air cools off your plugs faster or too much? Maybe a hotter plug would work better in a turbo? MAybe dual plugs?  |
Peter
| | Posted on Friday, November 08, 2002 - 03:55 pm: |
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Bob,
The intake air is hot, that's why they run intercoolers, to try and cool it down. The turbo heats the intake charge a lot. That heat then contributes to detonation problems. The ignition on a stock Aerocharger setup needs to be retarded a bit. I'm using an intercooler, and I've twin plugged the heads, to give me more scope with the timing. I'll set that up when I've run the engine in.
Think of the pipework in terms of volume. Increasing pressure in a small volume takes less time than trying to increase it in a large volume.
Also the time it takes to respond is relative. Fractions of a second can seem like an eternity when when you want it to react NOW. |
Vr1203
| | Posted on Friday, November 08, 2002 - 04:13 pm: |
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Pete,I know my exhaust is long, but my intake tube is just about as short as you can get.
Bob, You want as much heat in the turbo(exhaust side turbine) as you can get ,that's what makes it spin, heat.Its the hot expanding gases that are delivering the energy to the turbo impeller.We need to keep the exhaust as hot as possible not to waste our energy.
 |
Vr1203
| | Posted on Friday, November 08, 2002 - 04:28 pm: |
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As far as the FW goes,with standing starts I believe a HFW has a advantage. Think of those poor F1 car drivers stalling their engines all the time coming out of a pit stop. I think that is attributed to a very quick revving,very light FW type engine. |
Peter
| | Posted on Friday, November 08, 2002 - 04:40 pm: |
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Jim,
I think your boost tube is longer than mine, but my bike's not here at the moment, so I can't measure it 
I would stick with the lighter flywheel. Once you've launched, the extra weight will just cost you power. |
Jim_Witt
| | Posted on Friday, November 08, 2002 - 06:31 pm: |
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Cheers,
Anyone ever heard of Carl Pelletier (I haven't). Seems he sells turn-key blue-printed turbo motors for HD's.
S'later,
-JW:> |
Vr1203
| | Posted on Friday, November 08, 2002 - 06:47 pm: |
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Pete, At least mines way shorter than the orginal Aerocharger setup.And also I think it's shorter than the "improved" kit that mounts in the front. |
Richieg150
| | Posted on Saturday, November 09, 2002 - 03:55 pm: |
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TO WHOMEVER,what do turbos,and intercoolers.ect... have to do with the thread topic posted here? |
Buellistic
| | Posted on Saturday, November 09, 2002 - 06:27 pm: |
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ATT: Richieg150
"i" waiting for the BUELLschitt to clear up
to answer Jssport & Timbo. RIGHT ON!!!!!!!!!!!!
These BUELLers need to go to SACBORG and do posting on the wrong threads HEADING!!!!!!!!
In buelling
BLULLISTIC and/or
Hardley-Harley |
Vr1203
| | Posted on Sunday, November 10, 2002 - 08:59 am: |
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Sorry 'bout the off-topic,Richie
I thought the thread was kind of interesting. |
Flapjack
| | Posted on Sunday, November 10, 2002 - 11:54 am: |
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I twin plugged my previously owned iron head XL's and currently owned BMW's with excellent results. Both brands were more tollerent of the lower octain fuel available, less mixture sensative, and I was able to run less initial advance indicating more efficiency in the combustion chamber. I hadn't planned to twin my S1 in its present form because with its more compact chamber I felt it was not necessary. When time and inclination allow my current paper project for the S1 to become reality twin plugs are planned.
Peter and VR1203 start weaving a seperat turbo thread it is very interesting and I do have some thoughts I would like to share. |
Peter
| | Posted on Sunday, November 10, 2002 - 02:07 pm: |
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Richie,
You're quite correct. Sorry mate.
PPiA |
Timbo
| | Posted on Sunday, November 10, 2002 - 07:58 pm: |
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Back on topic Richie,
I know the Thunderstorm heads are an excellent design that really don't *need* dual plugging but, if I would have put Thunderstorm heads on my '98 1200S I would have dual plugged them even though most people I talked to suggested I not do it because *they* felt it wasn't needed. What those people fail to take into consideration is that, not dual plugging any '98 or later "S" model would more than likely require replacing the entire ignition system and wiring harness, or close to it.
So my advice to your friend would be to dual plug if he has the "S" model with it's unique ignition and electrical system. BTW, we kind of assumed your friend has an "S" when you started this thread. Correct us if we are wrong.
Timbo |
Richieg150
| | Posted on Sunday, November 10, 2002 - 10:30 pm: |
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Thanks Timbo,he has decided to go ahead and have the Thunderstorm heads duel plugged.This will save changing all the ignition system ect....Im sure he will be happy with the way it runs when its all said and done.By the way,I thought about an aero charger for my 2000 M2,before I built it,and my frame is different and it wouldnt work.I was told the aero charger was from 98 and earlier.I will check your torbo thread to see how yours are doing,thanks. |
Jssport
| | Posted on Monday, November 11, 2002 - 03:01 pm: |
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I know I'm in the minority on this, but IMHO;
ALL XL motors can benifit from dual plugging...
WHY ???
Because look at where the stock spark plug is, on the side of the cyl. This is a bad place to put it. Ideally it would go in the center. The flame front will arc out and reach the cyl wall all way around at the same time. In it's stock position on the side, the flame front hits one side first and it's reversion wave chases the flame front back across the piston and cyl to the other side.
Not a good thing,....
Dual plugging is not perfect but it's better than the stock setup.... |
Spiderman
| | Posted on Monday, November 11, 2002 - 03:29 pm: |
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If you index your plug and gap it properly you will see a better burn. |
Sarodude
| | Posted on Monday, November 11, 2002 - 03:45 pm: |
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Spidey-
I've seen different philosophies regarding indexing. How do you like the plug oriented? Do you notice different behaviors with different cumbustion chamber designs or cam profiles or ???
-Saro |
Spiderman
| | Posted on Monday, November 11, 2002 - 04:07 pm: |
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Well I have only done it on two motors one being a car and the other my Buell. With both I felt a definate increase in throttle response. And with the bike a cleaner burn. When you take the plugs out you can see a little white spot where the fuel is hitting the plug.
I have the open end of the gap pointing at the intake valve. |
Vr1203
| | Posted on Tuesday, November 12, 2002 - 09:32 am: |
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Had Mister Jerry Branch do dual plug heads on my XR1000 in '85. I did not see any diff.I could pull one set of plug wires off and not notice anything.I believe there are better ways to spend your horsepower money. I think alot of the dual plug stuff today is driven by emissions, big ,wide compression chambers need help. |
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