HarleyTechTalk

Gofast,
AFAIK a master engine builder is way more than a guy who can effeciently assemble an engine. You mention you search out facts and recommendations of the knowledgable people you trust, admire, and have confidence in their opinions. I believe these are the masters, the guys who break new ground for power, understand airflow, laminar effects, etc, and have the equipment to prove out theories and ideas and introduce new concepts to the industry.
Not saying you aren't a great assembler, but I'm not sure that "master" is the correct term, that's all.
JMHO, Bob

This looks like it's turned into a pissing match and an ego trip over simple terminology, the use of the word Master.     If this thread doesn't get back on track discussing throttle bodies, I will personally go in and delete every post not on the subject or better yet delete the entire thread and you will lose all the decent info(if there is any). Stop the pissing and moaning, Barry go to your room for a time out and chill.  Enough said.

Mike

I'm going to order the 55mm from HP inc today for my 103" build...I'll get it dynoed at the end of the month....(back on track)

A "peace offering" :>)

http://www.revtronix.com/techinfo/calculators/throttlebody.php

Keep in mind that the calculated airflow if you choose the CFM option is in SCFM, i.e. no test pressure is associated with it. The CFM is as one would see when measuring airflow on an engine dyno equipped with an air turbine. While not the best estimator I've ever played with, it's close enough to be usable. You have to be HONEST with your input data, unrealistic VE values will skew the results all out of proportion. Most street ridden HD builds will be doing *extremely* well if they get anywhere near 100% VE .... BWTFDIK, I'm not a master :>)

EDIT: Also the HP shown is CRANKSHAFT power. When calculating TB and injector sizes one must remember that the TB and injectors must supply the fuel and air for the *actual* power being developed, which is at the crank. The power wasted in the drivetrain ... well, your mission Mr. Phelps ...

Tireater, if (and that is a big if) I go with a bigger TB this winter, it's going to be the 51.  That already will be a big jump from my stock 46, plus the fact that the design is better than HD's (the better design alone will flow better, not just the bigger size).
Me thinks going too big might negatively affect the ranges where I spend most of my time (based on the experience of some of the other posters).

Ed E, Nice calculator!  Thanks for posting it, I will save it for when I can better figure out what values to add in the appropriate boxes. Don't look like anything I can guess at, and still be accurate.

Quote from: tireater on November 19, 2008, 12:44:27 PM
I'm going to order the 55mm from HP inc today for my 103" build...I'll get it dynoed at the end of the month....(back on track)

tireater what is the build sheet on your bike again

 <<BWTFDIK, I'm not a master :>)   >>     
 
Ed you gotta start posting more.....and what were the reasons that you don't like the grooves???

Quote from: tireater on November 19, 2008, 12:44:27 PM
I'm going to order the 55mm from HP inc today for my 103" build...I'll get it dynoed at the end of the month....(back on track)

I think most 103 which is where most guys are going to be running are going to fall into the 51mm to 55mm. The diffrence will be in the amount of flow in the heads and the selection of cama

Hmmm ... that's interesting. Makes one wonder how other motors seem to be able to produce comparable power outputs with TB's that would appear "small" compared to what most seem to be advocating here. For instance:

GM LT4 5.7 litre (350 CI) motor. 330 HP @ 5800 RPM, 340 TQ (I don't remember at what RPM off the top of my head). Uses a dual 48mm TB setup.

That setup flows about 620 - 650 CFM. And the HP/CI (.94) is pretty much in line with the "average" HD build as well as the estimated VE's.

If we cut the 350 motor displacement by 2/3, that would be about 116 CI ... how big of a TB do you folks think we would need if we kept the VE and power levels the same? Unless the GM engineers are using "different air" than us HD guys ... think about it.

 

Remember, the TB is only an air valve used to contol the amount of air needed by the motor to produce the power needed to move the vehicle at the speed desired. It should do that with the least restriction possible for *maximum* power across the entire powerband. In theory, you should be able to use a TB the size of a trash can lid if the runners/ports/valves are sized correctly and the ECM can meter the fuel correctly for a given area change of the TB!

Quote from: ederdelyi on November 20, 2008, 07:18:19 AM
Hmmm ... that's interesting. Makes one wonder how other motors seem to be able to produce comparable power outputs with TB's that would appear "small" compared to what most seem to be advocating here. For instance:

GM LT4 5.7 litre (350 CI) motor. 330 HP @ 5800 RPM, 340 TQ (I don't remember at what RPM off the top of my head). Uses a dual 48mm TB setup.

That setup flows about 620 - 650 CFM. And the HP/CI (.94) is pretty much in line with the "average" HD build as well as the estimated VE's.

If we cut the 350 motor displacement by 2/3, that would be about 116 CI ... how big of a TB do you folks think we would need if we kept the VE and power levels the same? Unless the GM engineers are using "different air" than us HD guys ... think about it.

 

Remember, the TB is only an air valve used to control the amount of air needed by the motor to produce the power needed to move the vehicle at the speed desired. It should do that with the least restriction possible for *maximum* power across the entire powerband. In theory, you should be able to use a TB the size of a trash can lid if the runners/ports/valves are sized correctly and the ECM can meter the fuel correctly for a given area change of the TB!

I do not know if compairing Chevy engines to Harleys. A 330hp to me is on the small side in the area of heads and cam so just like a Harley that engine will not be able to take advantage of a larger TB. The acid test is dynoing it with one and then another and this thread has plenty examples of the increases gained by the larger TB with the builds that can take advantage of because of greater heads and cams

My bad! I tried to keep it simple ... which of the big words don't you understand? :>) As Roseanna Danna would say ... never mind! There are some folks out there who will understand what I was getting at, and that's all I intended the post to accomplish.

Quote

If we cut the 350 motor displacement by 2/3, that would be about 116 CI ... how big of a TB do you folks think we would need if we kept the VE and power levels the same? Unless the GM engineers are using "different air" than us HD guys ... think about it.

Doing the same to your quoted HP/TQ numbers would be 110/113, not a bad target to shoot for.
It seems that a single 48mm would be more than enough in this example? (only had two on the whole 3/3rds)

Are you by any chance a "master"? 

>>It seems that a single 48mm would be more than enough in this example?>>

At these power levels, yes. If you use the link to the calculator that I posted and use VE's in the 87 to 90 range you will see that there is only a 1.5 HP loss and a .97 kpa pressure drop with a single 48mm TB. Even at 100% VE the power loss is only 2HP and the pressure drop is 1.17 kpa. Will a bigger TB hurt performance? Not really. There will likely be a diiference in throttle response and tuning could be more involved depending on how much bigger the TB really is.

*IF* you have a motor that is capable of high VE's at higher RPM's and you intend to use that capability then a large TB will certainly allow one to get the "last drop from the grape". If you have a 95, 100, 103, 107 ... whatever displacement motor that is like most street driven HD's out there then a large TB will likely be of little value. It depends on what your expectations are and how you intend to use the motor. The upside to this is that unlike a carb that is too big, too large of a TB will likely only hurt your pocketbook! :>)

Quote from: ederdelyi on November 20, 2008, 02:58:17 PM
>>It seems that a single 48mm would be more than enough in this example?>>

At these power levels, yes. If you use the link to the calculator that I posted and use VE's in the 87 to 90 range you will see that there is only a 1.5 HP loss and a .97 kpa pressure drop with a single 48mm TB. Even at 100% VE the power loss is only 2HP and the pressure drop is 1.17 kpa. Will a bigger TB hurt performance? Not really. There will likely be a diiference in throttle response and tuning could be more involved depending on how much bigger the TB really is.

*IF* you have a motor that is capable of high VE's at higher RPM's and you intend to use that capability then a large TB will certainly allow one to get the "last drop from the grape". If you have a 95, 100, 103, 107 ... whatever displacement motor that is like most street driven HD's out there then a large TB will likely be of little value. It depends on what your expectations are and how you intend to use the motor. The upside to this is that unlike a carb that is too big, too large of a TB will likely only hurt your pocketbook! :>)

You elequently took the words right out of my mouth, Ed.

QuoteThere will likely be a difference in throttle response and tuning could be more involved depending on how much bigger the TB really is.

Slower revving (one poster had mentioned). Not having been thru an overly large TB experience (and for a year now tempted to buy one), this point is nagging me.

While I spend most of my time cruising (aggressive cruise is common), I also like the best blast I can get from my babycam set-up.  IF I do go up in TB size, it will surely be the smallest step up.
Either the 51mm or possibly just reworking my stock TB.   Hel, I might still leave it alone.

In case you aren't familiar, I have an 08 103", 54's Mild port (1.9 intake stock exhaust), Fatcat, SERT.   I likely don't need a bigger TB.

Thank you for sharing your knowledge.

Been reading these posts for a while now, and I have come to the conclusion that no one will ever have the same opinion, so I am just going to use facts.  I've checked out dyno runs from several sites, Wood Performance, T-man Performance, Horsepower Inc., Joe's Cycle and have found nice gains using larger throttle bodies.  I have also talked to some of these performance shops, and have found that they do not recommend a larger throttle body when not needed.  They have all done comparisons and know what they are talking about.  I called Horsepower Inc. today and was told that based on what I have done so far to my bike, that I would not benifit from a larger throttle body at this time and to call back when I changed a few things.  Thought that was pretty cool considering they manufacture them and they weren't just looking to make a sale.  Try finding that elsewhere. I think this topic should end, I think we should call the experts before guessing whether it is needed or not.   

"I think we should call the experts before guessing whether it is needed or not." 

I believe this was covered well.
Ask the tuner! MAP pressure is their sign.

Quote from Grock
MAP almost always will start to drop from anywhere from 4100 to 4700 on a decent 95 and higher build with the Delphi. BUT.... the difference in HP is maybe 3 to 4 HP with a cam like the 37. And some of that may be caused by front to rear fuel reversion at high R's. So not a big deal on the TB size. Remember that you aren't hanging around in the 4000 to 5000 rpm range for very long anyway. The most that you can bore out of the stock Delphi is about 3mm MAX, and although that will move your MAP drop up a few hundred R's, it doesn't completely solve the issue you are having. Again, I'm not calling it a problem because it really isn't on a cam like the 37. This is for up to 2005 models. The 06's have their own problems in this arena, but some of those are influenced more by the smaller injector size that simply will not support high HP engines because of the limited pulse width. This, COMBINED with the TB bore, WILL cause problems on 06's that are trying to make big power.

Quote

I called Horsepower Inc. today and was told that based on what I have done so far to my bike, that I would not benifit from a larger throttle body at this time and to call back when I changed a few things.

Perfect!  
Now if you can elaborate on "What was done so far to your bike", it would be helpful to some of us less experienced folks, to help gauge whether we need one, or are in the same boat as you (not needing one).  This type of banter is why we are all here. To gain from others experiences.

Aw heck,....  I believe that I have already learned enough from this string to realize that a larger TB would not benefit me enough to justify it.

QuoteI think this topic should end, I think we should call the experts before guessing whether it is needed or not.   

I guess we really don't need a message board then, we'll just call our local indy with all of our question.  LOL

Hey Brian (Valley Racing), I hope you have a LOT of time on your hands.  I am gonna quit posting and start calling you everyday!

07 Street Glide with Vance and Hines, TW6-6 cams, Air cleaner and stock compression.  Told me to call back if I gain some head work, a larger cam and added compression.  They didn't even recommend reworking the stock throttle body for this build.  But check out their dyno run on the 2005 88 ci Dyna.  www.horsepowerinc.net/products/dyno-testing.  Wow!  Who's posting numbers like that?

ED
I suspect both Valley and or Larry can give you a definitive answer. The MAP pressure readings at sustained high rpm would tell the story. BTW same sort of scenerio holds true for small injectors (not saying yours are I have no idea...just saying) when the duty cycle becomes very high at high rpm and a proper mixture can not be accomplished.

Quotefront to rear fuel reversion at high R's

What causes that?

>>What causes that? <<

It's a "benefit" of the odd-fire configuration (45 deg. V-Twin) and has to do with the pulse width needed at higher RPM coupled with the "Y" manifold configuration. In essence, one injector is still spraying fuel that will interact with the other cylinder. Wouldn't happen in an individual runner setup.

Quote from: ederdelyi on November 20, 2008, 04:34:20 PM
It's a "benefit" of the odd-fire configuration (45 deg. V-Twin) and has to do with the pulse width needed at higher RPM coupled with the "Y" manifold configuration. In essence, one injector is still spraying fuel that will interact with the other cylinder. Wouldn't happen in an individual runner setup.

Ah, I see, sort of! In this higher rpm range, with regard to induction pulses, is the rear cyl seeing a "peak" while the front cyl sees a "trough", and the injector is trying to "fix" the situation?