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VOLUMETRIC EFFICIENCY FOR A HARLEY DAVIDSON 2
- Thread starter dbrow6272
- Start date
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1
- #2
BrianPetersen
Mechanical
*cough* Replace the bike with anything else ...
Seriously, the tuner that you describe is only an EFI calibration instrument. That cannot change the amount of air that the engine draws in. The amount of air that the engine draws in, is established by the "hard parts" ... camshaft, intake port and runner configuration, exhaust port configuration, etc.
And, VE is not a single number. It's one thing to get good VE at low revs. It's quite another to get it at high (for that engine ...) revs. The things that are needed to get good VE at high revs are quite likely to result in poor VE at low revs, so one needs to find an appropriate balance between the two, depending on what the engine is being used for. Intake runners that are tuned for harmonic resonance will add to VE at specific RPM points but equally take it away at other points. Again, the objective has to be changed depending on what you will be doing with the engine. Drag racers don't care about VE at 1500 rpm. Cross-country tourers normally don't care about VE at 6500 rpm or whatever your redline is. So, what's the objective?
The specifics of what needs to be done, you'll have to ask a H-D specialist. From my perspective, the engine configuration is all wrong (V-angle is too narrow, it's poorly balanced and prevents a good bore/stroke ratio from being used and that prevents high revs), the intake port configuration is all wrong, the valvetrain is all wrong, the cooling system is all wrong. Start over, with something having a wider V-angle (ideally 90 degrees so that no balance shaft is needed), wider bore shorter stroke, move the camshafts up to the head, use 4 valves per cylinder with a pentroof chamber and a shallow included angle, add liquid cooling, add individual tuned-length intake runners, and sort out the exhaust ... i.e. get a Ducati.
Seriously, the tuner that you describe is only an EFI calibration instrument. That cannot change the amount of air that the engine draws in. The amount of air that the engine draws in, is established by the "hard parts" ... camshaft, intake port and runner configuration, exhaust port configuration, etc.
And, VE is not a single number. It's one thing to get good VE at low revs. It's quite another to get it at high (for that engine ...) revs. The things that are needed to get good VE at high revs are quite likely to result in poor VE at low revs, so one needs to find an appropriate balance between the two, depending on what the engine is being used for. Intake runners that are tuned for harmonic resonance will add to VE at specific RPM points but equally take it away at other points. Again, the objective has to be changed depending on what you will be doing with the engine. Drag racers don't care about VE at 1500 rpm. Cross-country tourers normally don't care about VE at 6500 rpm or whatever your redline is. So, what's the objective?
The specifics of what needs to be done, you'll have to ask a H-D specialist. From my perspective, the engine configuration is all wrong (V-angle is too narrow, it's poorly balanced and prevents a good bore/stroke ratio from being used and that prevents high revs), the intake port configuration is all wrong, the valvetrain is all wrong, the cooling system is all wrong. Start over, with something having a wider V-angle (ideally 90 degrees so that no balance shaft is needed), wider bore shorter stroke, move the camshafts up to the head, use 4 valves per cylinder with a pentroof chamber and a shallow included angle, add liquid cooling, add individual tuned-length intake runners, and sort out the exhaust ... i.e. get a Ducati.
- Thread starter
- #7
Eric Buell left the Motor Company due to the Company not wanting to build his design. He did manage to get one of his machines produced by the Company, but for only one year. He then went on to start his own motorcycle company, thus the "Buell".
GregLocock
Automotive
Somewhat of a fair point. However your first post DID NOT say that, it implied you wanted to improve the VE - "I would like to get the absolute best VE out of this engine" is not even in the same ballpark as "My engine tuner needs to know the VE of this engine".
VE is the ratio of the mass of air drawn in per cycle to the displacement of the engine*air density. So if you can measure the mass flow rate at the intake you can work it out.
Failing that you can start to back calculate the VE at a given rpm if you know the capacity,torque, A/F ratio and the calorific value of the fuel. It'll be pretty flaky estimate as that ignores all sorts of losses.
At max torque it is likely to be around 100-110%, if the valves are big enough and open long enough and the rest of the intake and exhaust aren't overly restictive. The curve of VE vs rpm pretty much follows the torque curve.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
VE is the ratio of the mass of air drawn in per cycle to the displacement of the engine*air density. So if you can measure the mass flow rate at the intake you can work it out.
Failing that you can start to back calculate the VE at a given rpm if you know the capacity,torque, A/F ratio and the calorific value of the fuel. It'll be pretty flaky estimate as that ignores all sorts of losses.
At max torque it is likely to be around 100-110%, if the valves are big enough and open long enough and the rest of the intake and exhaust aren't overly restictive. The curve of VE vs rpm pretty much follows the torque curve.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
A few years back when I was designing ignitions for bikes, we played with adjustable timing on some of the Harleys. Adding +/- 10 degrees of timing did nothing for performance. On most other bikes, you'd see a change in timing as a change in power output. A better exhaust would help, 2-1 to try to get some scavenging.
One little trick that is useful in evaluating the aftermarket mods for these bikes would be to see if they have maps for a PowerCommander from DynoJet. DynoJet has a pretty standard AFR target for the bikes. So look at where their maps add fuel, and you can compare mods like exhausts and intakes that way. It isn't foolproof, but it is a useful tool. Only use the maps from DynoJet though, as they try to keep a standard. The maps produced by other companies may or may not have the same AFR targets, so wouldn't be a good comparison.
You should be able to download the PC software and maps from Dynojet for free.
MikeHalloran
Mechanical
I think I read in the SAE house rag a long time ago that carbureted Harleys get their unique sound from the shared intake cross tube, where the gas dynamics are, er, dynamic enough to make five of every twelve cycles a misfire. When they fitted EFI they had to reprogram the ECU to make some 'pretty good fires' to get the sound back.
Given that, I wouldn't be surprised if the ECU responds in odd ways to physical changes in its world.
I would be very surprised if any simulator correctly predicted the response of that ECU to physical changes in its world.
Mike Halloran
Pembroke Pines, FL, USA
Given that, I wouldn't be surprised if the ECU responds in odd ways to physical changes in its world.
I would be very surprised if any simulator correctly predicted the response of that ECU to physical changes in its world.
Mike Halloran
Pembroke Pines, FL, USA
------I have a 2010 Harley Davidson with a 96 cubic inch engine. I would like to get the absolute best VE out of this engine.-------
Other than a 650 Triumph decades ago, I've really no experience w bikes, but my long experience w/ drag racing tells me that you should pay attention to all above responses, that you should not only decide on primary use but do some -intensive- study re. stock air and fuel flows, get a solid baseline VE reading -- And then look to a strictly Harley professional w/ reasonable national fame. It is amazing what a balanced combination of piston design, head work, cam profile [and setting] and exhaust can do -- for the ride and pocketbook.
Too bad so many of the mature small custom cam grinders and header makers have gone out of business over the last two decades, but new ones arrive and gain experience.
Please be careful -- bigger is not always better.
John
Other than a 650 Triumph decades ago, I've really no experience w bikes, but my long experience w/ drag racing tells me that you should pay attention to all above responses, that you should not only decide on primary use but do some -intensive- study re. stock air and fuel flows, get a solid baseline VE reading -- And then look to a strictly Harley professional w/ reasonable national fame. It is amazing what a balanced combination of piston design, head work, cam profile [and setting] and exhaust can do -- for the ride and pocketbook.
Too bad so many of the mature small custom cam grinders and header makers have gone out of business over the last two decades, but new ones arrive and gain experience.
Please be careful -- bigger is not always better.
John
list of possibly helpful links --
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- #15
^ wow i wish there was an edit button, i keep pressing submit without finishing.
here are the mods for that engine:
Harley Davidson stock "Big Twin", note high crank area is dipping into oil level (poor design)
Stock "Big Twin" Harley Davidson heads ported by RHC
Custom Individual Runner Harley Davidson intake with 2 39 mm slide valve carbs built by RHC
Stock exhaust with Harley Davidson off-road mufflers with crossover. Each muffler flows about 150 CFM a 20.5" on flow bench.
Crane Cam hydraulic H304-2 for Harley Davidson. (Specs for valve train dynamics are approximate.)
here are the mods for that engine:
Harley Davidson stock "Big Twin", note high crank area is dipping into oil level (poor design)
Stock "Big Twin" Harley Davidson heads ported by RHC
Custom Individual Runner Harley Davidson intake with 2 39 mm slide valve carbs built by RHC
Stock exhaust with Harley Davidson off-road mufflers with crossover. Each muffler flows about 150 CFM a 20.5" on flow bench.
Crane Cam hydraulic H304-2 for Harley Davidson. (Specs for valve train dynamics are approximate.)
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