With a lighter flywheel, your pistons are doing all the work to keep the crank in motion. You need way more midrange and top end, then with a heavier flywheel.
Texas Two Step Taco
- Thread starter Texasstar
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A heavy flywheel helps to maintain the energy once it has been created, so for example at high revs it may just want to keep going where a lighter flywheel might allow it to run out of breath.. B U T a lighter flywheel takes less energy to build that inertia and also less total vehicle weight to accelerate so it should accelerate harder.
On a street bike a heavy flywheel can sometime be an advantage but on a drag motor you need to use what you have and that's power at higher revs. Check the torque and power curves from a dyno run and see where you need it to rev to. DOn't run it way into the red just because that seems like the way to go. It isn't. It is really important to rev it to the right moment and then change to keep it in the meat of the torque curve.
Make the most of what you have and keep looking for more. Reed valves can help at low to mid range by reducing blow back and so improve volumetric efficiency. More gas stays in the motor and that also raises the effective compression ratio.
You could also run the pipe and port numbers through Bimotion and MOTA or even EngMod2T to make sure pipes and ports are matched. Then add in all the timing advance and compression she'll stand. Make sure the squish clearance and width provide the target MSV at the revs you want to run. Too low, tighten it up. Too high reduce the width or thickness.
If allowed, try Methanol which will keep the motor cooler and add about 15% more power, and if it's not allowed look at using E85 and raising the compression to get the most out of it. Methanol doesn't have an Octane number but is equivalent to say 120 octane gas plus it carries more oxygen and combined with the extra fuel it makes more power.
If all that overpowers your ignition system start looking at a more powerful CDI system, but first try changing ignition timing on the dyno and plot the results to get the best result.
Ask BB to design and machine a billet torroidal head. Add extra transfer and exhaust ports. No shortage of things to try.
And back to the flywheel thing. If it's missing and breaking up, that's not the flywheel inertia but fueling or spark issues. Did I mention getting it on the dyno again with a sniffer? If your local dyno guy wont sniff a two stroke pipe, get an Air-fuel meter and Bosch sensor and log the results, even if you just get a video of the A:F and revs and look at the dyno charts and manually check the A:F.
On a street bike a heavy flywheel can sometime be an advantage but on a drag motor you need to use what you have and that's power at higher revs. Check the torque and power curves from a dyno run and see where you need it to rev to. DOn't run it way into the red just because that seems like the way to go. It isn't. It is really important to rev it to the right moment and then change to keep it in the meat of the torque curve.
Make the most of what you have and keep looking for more. Reed valves can help at low to mid range by reducing blow back and so improve volumetric efficiency. More gas stays in the motor and that also raises the effective compression ratio.
You could also run the pipe and port numbers through Bimotion and MOTA or even EngMod2T to make sure pipes and ports are matched. Then add in all the timing advance and compression she'll stand. Make sure the squish clearance and width provide the target MSV at the revs you want to run. Too low, tighten it up. Too high reduce the width or thickness.
If allowed, try Methanol which will keep the motor cooler and add about 15% more power, and if it's not allowed look at using E85 and raising the compression to get the most out of it. Methanol doesn't have an Octane number but is equivalent to say 120 octane gas plus it carries more oxygen and combined with the extra fuel it makes more power.
If all that overpowers your ignition system start looking at a more powerful CDI system, but first try changing ignition timing on the dyno and plot the results to get the best result.
Ask BB to design and machine a billet torroidal head. Add extra transfer and exhaust ports. No shortage of things to try.
And back to the flywheel thing. If it's missing and breaking up, that's not the flywheel inertia but fueling or spark issues. Did I mention getting it on the dyno again with a sniffer? If your local dyno guy wont sniff a two stroke pipe, get an Air-fuel meter and Bosch sensor and log the results, even if you just get a video of the A:F and revs and look at the dyno charts and manually check the A:F.
Texasstar said:
In the first video it fell flat when the clutch was let out too fast and revs dropped. And on the street take off, it looked/sounded like it was only running up to mid revs. It has to be jetted right to get the most out of it.
Assuming it is 84.5 * 64.0 it "should" be OK to 8000 or even 8500 if the rings are thin enough. Ring flutter will limit revs.
That huge bore needs to be fed well so take care to get both transfers to match (mirror) each other. A modern fat pipe should help overcome porting limitations to some extent and you may need a larger carb. A large bore H2 runs something like 40mm flat slide Lectrons, and may have a lower primary compression than you have but probably has more port time-area.
If it does make peak torque at say 7,000 and peak power at 8,000, try leaving the line at somewhere around 7,000 revs and don't let the revs drop. Then shift at 8,000 or so and cross the line at 8,000 to 8,200 i.e. just rolling over the top of the power curve. Invest in lots of clutch plates..... They may only last one use - getting off the line and if they start to slip, add a lock up and look at lighter springs. With say 4 runs of 1/8th mile, that's only half a mile of running in a day. How hard can that be on a bike? ;-)
My bike - it's "stock", so I don't need any of that stuff. Maybe I should drop on one of the full race barrels and design new pipes and see what the old girl can really do. But then I'd have to get a rider who knows how to drag race to get the most out of it.
Texasstar
Can't is a four letter dirty word
you hit the nail on the head...our dyno guy said it was worthless to use a sniffer...we need to go to BB’s dyno who understands two strokes.teazer said:
Both Bill and Jim our dyno guy said picking up the signal from the mag ignition causes interference with their machines to get the torque numbers but we will address that later.
We will use the heavier flywheel for now until we can address advanced tuning like methanol carb tuning , toroidal combustion chambers, Et al. Oh and AJT in Spain has plenty of upgrades... - 5 speed gearbox
- 5 transfers racing cylinder
- all new ignition with double map
- Wiseco specific AJR piston
And miles to go before I sleep...
I have two sets of extra clutch plates. Zeke has none. The funny thing about my competitors Ducati 900ss is that the dry clutch does NOT like to be drag raced. I have a friend that raced his in a straight line and lost a second each run in the quarter mile.
Thank you! Well it has been pouring rain in Texas since we started this project and we are not getting any testing time. Next Friday looks clear but I have an idea the turf racing will turn into mud racing.
My goals currently are to have fun and see how much we improve on last years time. Show up and finish! Lol!
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As a corollary, once you have your dyno information, you'll want to compare that to your gear ratios. The goal is to have as much torque going to the rear wheel at any given time. You should be able to calculate when the drop in torque at higher RPMs matches up with the same rear wheel torque values at a higher gear and lower RPM. On NA four strokes, you usually just take it to redline, but FI and two strokes are a different beast.
This doesn't make sense. If the goal is to tune for a lighter fly wheel, which is better for drag applications, then all of your other data will be off.Texasstar said:
Texasstar
Can't is a four letter dirty word
Oh don’t worry this will make sense and we will tune for the lighter flywheel later. No doubt. There are too many variables that need to be addressed first. Chassis set up and air shifter are first on the list. We have a brand new 1/8 Drag strip 5 miles from my home.irk miller said:This doesn't make sense. If the goal is to tune for a lighter fly wheel, which is better for drag applications, then all of your other data will be off.
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That's true, but there is also the element of time availability and sometimes we have to stop and make what we have work before embarking on the next step along the path of development.
Exhaust sniffing is interesting. We had a situation once with a Factory Pro eddy current dyno run on a 4 stroke where CO and CO2 levels looked normal and unburned HC levels were really high. What is was really telling us is that what burned was in the correct proportions but we had a lot of raw fuel going down the tailpipe. That was because we were using Primary (2 stroke) type needle jets which result in large fuel droplets and we needed to break that down and atomize it better to increase surface ares to be able to burn more of the fuel we were feeding it.
On a 2 stroke the churning through the crankcase adds turbulence and improves atomization but we still have unburned fuel and oil to confuse the simple sniffer on a Dynojet and its operators. The simple approach is to measure A:F and plot those against power/torque to work out what makes the most power and then tune for atmospheric changes to that empirical A:F target.
It's like looking at plugs. What should they look like? The answer is that they should be clean and after that they should look like they do when you make most power - whatever that looks like on your motor.
BTW, power and torque are the same. A Dyno measure torque (twisting action) and converts it to power using a simple formula. Where the dyno may suffer is its ability to read RPMs. On a more modern digital ignition that's easy to do, but our old noisy ignitions can complicate that.
Exhaust sniffing is interesting. We had a situation once with a Factory Pro eddy current dyno run on a 4 stroke where CO and CO2 levels looked normal and unburned HC levels were really high. What is was really telling us is that what burned was in the correct proportions but we had a lot of raw fuel going down the tailpipe. That was because we were using Primary (2 stroke) type needle jets which result in large fuel droplets and we needed to break that down and atomize it better to increase surface ares to be able to burn more of the fuel we were feeding it.
On a 2 stroke the churning through the crankcase adds turbulence and improves atomization but we still have unburned fuel and oil to confuse the simple sniffer on a Dynojet and its operators. The simple approach is to measure A:F and plot those against power/torque to work out what makes the most power and then tune for atmospheric changes to that empirical A:F target.
It's like looking at plugs. What should they look like? The answer is that they should be clean and after that they should look like they do when you make most power - whatever that looks like on your motor.
BTW, power and torque are the same. A Dyno measure torque (twisting action) and converts it to power using a simple formula. Where the dyno may suffer is its ability to read RPMs. On a more modern digital ignition that's easy to do, but our old noisy ignitions can complicate that.
No, that's the point at which the horsepower and torque are the same (due to the formula for calculating horsepower, which is just force over time).
In gasoline engines, torque changes over RPMs based on the volumetric efficiency of the engine at a given RPM and throttle setting.
In gasoline engines, torque changes over RPMs based on the volumetric efficiency of the engine at a given RPM and throttle setting.
In a word No.
That's just a factor in the calculation.
HP = Torque x RPM ÷ 5252
Your Honda twins made peak torque at 8 or 9000, many two strokes make peak torque at the same revs as peak HP. Typically though, peak torque is at lower revs than peak HP. Or put another way: Torque hits a peak but as revs rise, so does HP until the torque is dropping off faster than revs are rising and at that point HP peaks and starts to drop as well.
That's just a factor in the calculation.
HP = Torque x RPM ÷ 5252
Your Honda twins made peak torque at 8 or 9000, many two strokes make peak torque at the same revs as peak HP. Typically though, peak torque is at lower revs than peak HP. Or put another way: Torque hits a peak but as revs rise, so does HP until the torque is dropping off faster than revs are rising and at that point HP peaks and starts to drop as well.
Texasstar
Can't is a four letter dirty word
I see why BB has a dyno in his garage...for the dark arts of two stroke tuning.teazer said:
This is going to be fun.
I will know tonight if the shifter issue is addressed. I found out from Tim at Hughs that when he raced his taco he would go into a false neutral above the gear he wanted to be in because he did not roll off the throttle enough. Then he would have to tap it down to go into the correct gear. They fixed this problem in the Pursang by adding a spring on the shifter drum to add drag.
First to second was no problem but second to third put us in a false neutral. However nothing was welded rigid for the perch so I am eliminating the variables.
Called Pingel and found out the air cylinder for engine kill is set at 85 milliseconds and can be increase by extending the tubing. Don’t think that is the problem because it went into second no problem. Also was in a slight bind. Pingel said I may have to go to a longer throw cylinderI don’t know if that is the problem until everything is rigid.
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Texasstar
Can't is a four letter dirty word
Electro-Magnetic Interference (EMI) is a problem created when spark plug wires are not properly shielded by carbon suppression conductors. EMI is produced in the wires and can cause interference in certain electronic devices on the vehicle, including the engine management system, receiving false or erroneous signals.
Things you should not do like zip tying spark plug wires with other wires... we will start here.
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but you don't have an engine management system.....
But that HT lead may be sending noise to the coil or to the stator and if they are FEMSA or Motoplat, may include electrical components if not a lot of circuitry.
I'd start with a resistor plug cap and clip those zip ties. You could shorten teh HT lead too, to move it away from other leads. You are on the right track.
But that HT lead may be sending noise to the coil or to the stator and if they are FEMSA or Motoplat, may include electrical components if not a lot of circuitry.
I'd start with a resistor plug cap and clip those zip ties. You could shorten teh HT lead too, to move it away from other leads. You are on the right track.
Who gave you that name? Was that a BB reference to Henry who built a 136HP reed valved street H2 or someone else? Who built those pipes? Andrew Walms (WTF pipes) builds amazing pipes for Kawasaki triples that snake all around the place. There are a couple of guys building amazing Denco replica pipes but I don't know their real names.
