Bigger is not better - Throttle Body that is.....

[GoFast.....]

Fuel management systems and build combos effect throddle response. My 55hpi on the 107" with the tmax is working flawless. Just had it out yesterday at a big outlaw funnrel yesterday. In the parking lot, stop and go percession with a 100 bike in stop and go. No surging no jerking at any throddle position. I couldn't be more happy with this 55hpi and oh my what a fire it builds when you twist the wick at WOT

[Deye76]

Fuel management systems and build combos effect throddle response. My 55hpi on the 107" with the tmax is working flawless. Just had it out yesterday at a big outlaw funnrel yesterday. In the parking lot, stop and go percession with a 100 bike in stop and go. No surging no jerking at any throddle position. I couldn't be more happy with this 55hpi and oh my what a fire it builds when you twist the wick at WOT

Isn't that a new motor? Funeral procession? How hot did it get?

[GoFast.....]

Fuel management systems and build combos effect throddle response. My 55hpi on the 107" with the tmax is working flawless. Just had it out yesterday at a big outlaw funnrel yesterday. In the parking lot, stop and go percession with a 100 bike in stop and go. No surging no jerking at any throddle position. I couldn't be more happy with this 55hpi and oh my what a fire it builds when you twist the wick at WOT

Isn't that a new motor? Funeral procession? How hot did it get?

it has 450 miles on it and it was only 60 degress out. Warn for us in Colorado

[flhtcu2007]

Wow this post is going to the extremes. I believe what Bob is talking about here is a "mild build" something that most on this post (although not all) build. Such as going from a 96 to 103 with mild cams. i don't believe he is talking massive builds with huge ci's. I had a post about going with larger injectors a while back and I'll share a story about working with a 251 cam build in a 103. The larger se throttle body seems like a good deal for the price and I know some of the larger throttle bodies seem very enticing and a quick way to get a few more hp on the dyno. What the dyno won't tell you is variations in cold weather and hot weather. It won't tell you about a hickup at low speed while you are pulling out of the driveway (And my friends let me be the first to tell you that's a heart stopping experience) Slow speeds in a turn are the worst time to have a hickup. I know there are great tuners out there that will argue that all of this can be tuned out but let's face it.....great tuners are generally few and far between and most don't live close to the folks who are reading this. I tune with a daytone and have a sert. While I am anamateur I've had the pleasure of tuning several bikes and have been several hundered miles to help others with there tune after someone paid $300.00 for a tune somewhere else that was considered a professional. All he is trying to say here for everyday driveability on a mild build....stock not only works fine....but is prefferred. I totally back him on this. BTW...after multiple tuning attempts on the 251 build with the se throttle body .....going back to the stock throttle body cured every ill and the customer was happy. I'll be honest...yeah he lost just a little on the top end.....but the drivabilty improved so much that he was ecstatic. Performance is great.....I love it......but sometimes you gotta remember the old lady is on the back too. You can look at my post about downgrading from the 4.89 injectors back to stock for another reference point. FYI.....I love the sert with the daytona setup...but I also love the tmax setup...so I'm not biased either way. Both have there pros and cons.

[Don D]

Yes exactly
That is what a stumble will do, a safety issue
Think about one of these high torque light switch on off torquers in a turn and a bump is hit in a lower gear (on the torque curve) and a little flip of the wrist, could also be a hazard.
I really like Bob/s approach to performance with a big lazy torquer that is build tough from the bottom up and has breathing potential but is not on the bleeding edge of anything.
Add nitrous to that and ......

[Admiral Akbar]

What makes you think the 55 hpi will not do that, I must have a more than usual perfect setup with the TMAX on this 107"

Still insist on baiting?

Bob,

It's not baiting, its the "mine is better than yours" syndrome.. Max

[ederdelyi]

Attitude ... err, altitude may have something to do with it :>)

[AllanW]

Its both 

[Dennis The Menace]

Good thread. I keep wondering what elevation has to do with this equation?  Barry and I live at 6k feet, so thinner air.  Would this maybe have an effect on the TB size and its strengths/weaknesses with respect to slow speed drivability?

I dont know, and not stirring things up.  Just wondering how this plays into it.  TIA

menace

[GoFast.....]

Good thread. I keep wondering what elevation has to do with this equation?  Barry and I live at 6k feet, so thinner air.  Would this maybe have an effect on the TB size and its strengths/weaknesses with respect to slow speed drivability?

I dont know, and not stirring things up.  Just wondering how this plays into it.  TIA

menace

Where do you live Menace. I want you to drive this big throddle body that run perfect and post a Big throddle bodies are better.

[Showdog75]

Woodshed anybody ?    

[Shadowdog]

Wow this post is going to the extremes. I believe what Bob is talking about here is a "mild build" ...but the drivabilty improved so much ...but sometimes you gotta remember the old lady is on the back too. ...

Hi Folks,

We need an icon of a a smiley face throwing gas on a fire. So many times people get lost in chasing numbers and loose sight of the actual goal, drive ability, a good, safe, fun ride that delivers the right performance to put a smile on your face. Go Fast, I'm happy for you, really glad you like your ride,  Bob, thanks for posting this,:beer:, you are right, IM Not so HO.

Best to all,

Shadowdog

[Bruno]

Quote from: FLTRI on March 13, 2009, 09:24:14 PM
Quote from: GoFast..... on March 13, 2009, 09:17:48 PM
What makes you think the 55 hpi will not do that, I must have a more than usual perfect setup with the TMAX on this 107"

Still insist on baiting?


Bob,

It's not baiting, its the "mine is better than yours" syndrome.. Max

It's obvious how buddies stick up for buddies.  Gofast was not baiting.  I saw nothing about "Mine is better than yours" either!  WTF!
Bob always claims somebody is baiting him.  (Paranoia mebbe?)  Surely a 58mm TB on a near stock motor might give symptoms that Bob described, but Bob really overstated the "too big" issues of Throttlebodies.

Thanks for the correction, but the issue isn't how much power you get from your TB it is the rideability in town as you roll over railroad tracks and the throttle gets a slight bump and jerks the bike. It's the ability to putt through a parking lot @ 1/32-1/16 throttle and have the engine be smooth as silk. It's the very small throttle openings that make it difficult to slow-putt when the TB is 51mm-62mm on a 95-103ci engine.
Sorry if I didnt make that clear enough, but it seems there are some that got it.

There are 51's, 54's & 55's all over these messageboards running on 95-103ci engines without issue.  Gofasts 107 is not dramatically bigger, not big enough to discount his statement.

I don't see why you guys are hammering Gofast for having the balls to post his problem free "too big" TB, other than your bias towards Bob.  These boards are about sharing info, from all posters, not biasing it all towards ONE posters opinion.  What a bunch of crap!   There was nothing baiting here (other than some of Bob's comments). LOL

Bob overstated the TB size vs Drivability issues. Admit it guys.  Max, you are experienced enough to know about how TB size works in the real world. I can't believe that you are going along with this sharade!

[uglyDougly]

   Bruno used the phrase 'core group', and FLTRI asked if anyone would like to share experience.

   As this discussion has progressed, the subject seems to have narrowed to include only much larger than necessary throttle bodies. If that's the case, nobody has ever built an engine with something like that.

  But, I've tuned lots of 120HP 95s and several 130HP 103s with the K brand 57mm (remember the discussion about 2.244" size? 0.006" less than an S&S 'B') and all of those exhibited excellent drivability and no tendency to lurch in parking lots.
  Everything Bob says about larger throttles is true. For the same throttle angle the amount of air is much greater off idle for a large TB.
  That means that it has to completely remapped down there.
  If the TB is way larger than necessary, the top line of the VE tables doesn't need to be touched.

  Harleys have and always have had tiny carbs (throttles). Every other type of motorcycle has much more throttle size for the displacement than any H-D and they all don't lurch in parking lots or going over railroad track (maybe wobble?)

  Whenever I put a customer on his own bike on the dyno after a calibration I notice that the Harley guys don't 'blip' their throttle for downshifts.
  Why? Because your weeny throttle doesn't rev the engine with a 'blip', that's why.

   So, I don't agree to anything except, if they run like crap at low throttle settings, they need more tuning.

  Is this the 'core group' you remember, Bruno?

   Doug

[Bruno]

So, I don't agree to anything except, if they run like crap at low throttle settings, they need more tuning.

  Is this the 'core group' you remember, Bruno?

   Doug

Thank you Doug.  LOL  No, I never included your name in the "core group" because you don't post frequently and you don't participate in the silly mud slinging. Your posts are always of the sensible nature.     Your comment "if they run like crap at low throttle settings, they need more tuning" goes right along with the real life examples of many who have posted here about using aftermarket TB's with success. I was hoping that somebody with your credibility would speak up!  Thank you!!

Many of our fellow HD riders come here to learn, and I hate it when the information gets twisted into "only one man's opinion, anyone who disagrees is baiting". LOL

Again, Thank you. 

[nc-renegade]

I don't see why you guys are hammering Gofast for having the balls to post his problem free "too big" TB, other than your bias towards Bob.  These boards are about sharing info, from all posters, not biasing it all towards ONE posters opinion.  What a bunch of crap!   There was nothing baiting here (other than some of Bob's comments). LOL

Bob overstated the TB size vs Drivability issues. Admit it guys.  Max, you are experienced enough to know about how TB size works in the real world. I can't believe that you are going along with this sharade!

Good response!

There are reasons for wanting the right size TB for the CFM flow of the engine, especially considering the resolution of the potentiometer of the TPS...but I too get tired at the "I'm stating facts and all others disagreeing are stating opinion...that's BS"

BTW, my 107" drivability is extremely good, but I'm running a 51mm with a T-Max.  I would of used a larger one on this build if I had not already purchased the 51 for my 103" build.

[roadrunner]

I would like to confirm what ugly-dougly said.
i now have over 14,000 miles on a 103" with a 57mm t-body. Before putting it on i had concerns about driveability. Not anymore. 04 roadglide pulling a trailer through the Rockies in colorado and the next year across Ontario to Niagara falls and back both trips were about 3000 miles. close to 40 mpg pulling the trailer. it is not a radical build but makes 122 horsepower and 118 for torque. absolutely no draveability problems what so ever as low as you want to go. the throttle response is excellent.

[Clintster]

Bigger is not Better, is the topic.  Have any facts been presented that Bigger has negative effects on performance.  Throttle postition sensitivity is that safe to say? Can that be tuned to be a non-factor,  I am only the layperson wondering?  I do know the 53 mm TB on my 95 was recommended/ ok'd by my builder.  Is it true that the larger TB's are more effective for horsepower rather than torque in the smaller displacement TC's.  I do know my bike is very responsive, not overly so and makes good power.  I will be able to use it in a larger motor and has no negative effects on this configuration.  

[hdtuner23]

Not to take credit away from Doug,  BUT It's TUNING, TUNING, TUNING.               

[fuzznut5197]

Why? Because your weeny throttle doesn't rev the engine with a 'blip', that's why.

Is it the weeny throttle or the 400 lb flywheels? 

[GoFast.....]

Good thread. I keep wondering what elevation has to do with this equation?  Barry and I live at 6k feet, so thinner air.  Would this maybe have an effect on the TB size and its strengths/weaknesses with respect to slow speed drivability?

I dont know, and not stirring things up.  Just wondering how this plays into it.  TIA

menace

Where do you live Menace. I want you to drive this big throddle body that run perfect and post a Big throddle bodies are better.

Hey GoFast,
Why do you think you have a "big throttle body" for your build? Other than baiting, you have not done anything but brag about how your bike runs perfect.....in your opinion.
Put a 62mm TB on that bike and see how well the T-max deals with tuning it and how easy it handles 1-2% throttle openings, then you can talk about having a "big" throttle body.
Don't be a "Master Baiter". :hyst

Bob the only Master Baiter is you because you and your Little fan club are the only ones that keep bring up this fetish of Baiting. If we spent all this time talking about big TB and that does not include 55 mm and is 62mm then I agree that it will probably be a problem. But I do think that's what a lot of us thought was a Big Throttle Body. I think large is 51mm and up. But large means diffrent things to diffrent people. But If you are going to try and convince people that a 51 or 55 will not run right then I am going to keep posting here as long as this thread last. Plus I do not have to end this post with the little smirk face or the guy laughing.

[ederdelyi]

>>Is it the weeny throttle or the 400 lb flywheels?<<

Both. On a carb bike a larger plenum can also affect throttle response.

Bottom line (IMO) is that the TB should be sized for the least restriction at WOT for best HP. That will usually give the best combo of power and throttle response. Remember, we are talking EFI, not carbs. The TB only needs to manage the airflow with the least possible restriction/turbulence as opposed to a carb which needs the pressure drop to get the metering signals it needs to do it's job. A carb must be a restriction to operate, a TB does not need to be.

I posted links to TB sizing calculators on here before ... it's what most of us car guys do when sizing TB's. The principles are exactly the same for HD motors ... last time I checked they use the same principles and physics as any other spark ignition, throttled motor. In theory, you could use a TB the size of a trash can lid, but it would be tough to control the throttle opening ... think binary control :>)

Ya know, there really is some science to this stuff, it's a shame that so many seem to think that it's all either BS or just not needed 'cuz "it's not rocket science, it's a Harley". I could not disagree more with that statement, BWTFDIK!

[05FLHTC]

Good thread. I keep wondering what elevation has to do with this equation?  Barry and I live at 6k feet, so thinner air.  Would this maybe have an effect on the TB size and its strengths/weaknesses with respect to slow speed drivability?

I dont know, and not stirring things up.  Just wondering how this plays into it.  TIA

menace

Where do you live Menace. I want you to drive this big throddle body that run perfect and post a Big throddle bodies are better.

Hey GoFast,
Why do you think you have a "big throttle body" for your build? Other than baiting, you have not done anything but brag about how your bike runs perfect.....in your opinion.
Put a 62mm TB on that bike and see how well the T-max deals with tuning it and how easy it handles 1-2% throttle openings, then you can talk about having a "big" throttle body.
Don't be a "Master Baiter". :hyst

Bob the only Master Baiter is you because you and your Little fan club are the only ones that keep bring up this fetish of Baiting. If we spent all this time talking about big TB and that does not include 55 mm and is 62mm then I agree that it will probably be a problem. But I do think that's what a lot of us thought was a Big Throttle Body. I think large is 51mm and up. But large means diffrent things to diffrent people. But If you are going to try and convince people that a 51 or 55 will not run right then I am going to keep posting here as long as this thread last. Plus I do not have to end this post with the little smirk face or the guy laughing.

AMEN 

[FLTRI]

No fan club, just some who I thought appreciated the input. Sorry for the comments. You guys are right I wasn't baited, just good input.
I humbly apologize,
bob

[Don D]

Bottom line (IMO) is that the TB should be sized for the least restriction at WOT for best HP

Ed, in your opinion can that be determined with a flow bench at 28" test pressure?