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

[se]

my 58 with my build runs flawless . as far as putting thru parking lots what about drag cars and drag bikes i beleive it has more to do with the rider knowing his bike.
now if you were to say that builders should watch what they sell to their customers because they might try and sell  you a t/b too big that wil be diffrent.
if you have a parts pusher  for a builder well then you will learn soon enuff that the parts you are buying are $hit.

[txtech]

I think ya'll two need to meet up and put the boxing gloves on and get it outa your systems.Lol  
 

i"ll put a hundred on bob, somebody said he keeps a ninja suit in his dyno room.

[Sonny S.]

They buy cams too big because they want to make the big #'s so it just stands to reason that they wll do the same when it comes to throttle bodies. Always overbuild 'em then try to get them to be drivable AFTER they have that dyno sheet in their pocket. I've been trying to steer people away from the 'bigger is better' principle since the early 70's when I was working on cars. Even then they would buy the 850 to try & make their car go faster when a 650 was all it could handle. The years roll on but the thinking still hasn't changed: If it's bigger it must make more power.

AMEN !! 

[Bruno]

A few months ago it seemed like the same core group was preaching that a bigger TB could not hurt anything (but the gains might be limited).  Now it seems that a bigger TB runs like crap in parking lots.  Interesting.  What has changed?  Is it something to do with astrology and the angle of the planets?   

[Deye76]

This thread should say bigger is not always better. I have about 350 miles on the 107 WT build. Everything about this build turned out perfect. The 55 hpi with Se 4.89 injectors works flawless, Starts easy, Idles great and make that Wild Thing build flat get it on all the way up to the 6200 revlimiter.

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.

I have a 51mm HPI, that I had on a 95" w/HTCC CNC heads and a WT46G cam set. Doug L tuned it, perfect street manners at all throttle positions, made good power (110hp/107tq) IMO. When I went to 113" a/c lifter failure, same heads, but now a S&S .625 cam. With a different tuner, initial tune had terrible low speed manners (surging etc.), took it back and he then spent the appropriate amount of time tuning, instead of just getting me out the door, and all was good.
What does all this =?
I can only conclude, (being very far from an expert) that
1. The heads flowed enough for that TB at both 95" & 113"
2. It's tuning, tuning, & more tuning.
What am I leaving out?
Thanks.

[Don D]

Good thread very entertaining
Anyone remember Hilborn? Same driving characteristics to the extreme.

[hdtuner23]

My thoughts are you size the TB for the max. CFM the engine is capable of.  This allows the TB to be nonrestrictive, yet keep the velocity maximized for the engine size.  This assumes you use a well designed TB and not a hogged out stock one done without consideration for the flow and velocity behavior of the TB

--------------------------------------------------------------------------------
They buy cams too big because they want to make the big #'s so it just stands to reason that they wll do the same when it comes to throttle bodies. Always overbuild 'em then try to get them to be drivable AFTER they have that dyno sheet in their pocket. I've been trying to steer people away from the 'bigger is better' principle since the early 70's when I was working on cars. Even then they would buy the 850 to try & make their 

Couldn't Have said it better!

[Don D]

Bob
The motors go up in size and need bigger TB and there is an appropriate choice for any of them but what about the software. Big high torque motor larger TB and the same programming parameters and hardware. The algorithms don't change
So the 124" SERT 58mm equipped motor has the same TPS / MAP / RPM profile as a stocker. My point this is not completely a hardware gear choice problem is it? What in the software can be adjusted to tell the ECU that a much smaller throttle opening makes a lot mor happen a lot faster??

[Bruno]

The core group I believe you are referring to never addressed the parking lot cruise, just running on the highway and WOT.

Wrong. Low end cruising was adressed and it was clearly stated that "with proper tune the low range would not be affected". I am sure the threads are still floating around. People can change their minds and opinions, but machines using the same components don't change their behavior unless the tuner doesn't tune it correctly.

I still think it is an astrology thing. LOL   

[Deye76]

Bob, to answer your question if the 51mm, got me more than the stock, I can't answer with proof, such as a before and after graph. This is a 2004 where the stock manifold constricts down to 38mm IIRC, so if there was an increase in power it likely was up over 4500 rpm. For those with differing opinions, the distinction between built and relatively mild build must be referred to so confusion is avoided. I take the original post as referring to, say a 95" big bore with stock heads, pipe, and a mild cam and then bolting on a 51mm TB. Is my assumption correct?

[ederdelyi]

It all boils down to what the goal is. Unfortunately, for many the goal is clouded by many influences, this and other web forums included. Many have not learned the lessons that others have as this may be the first "hot rod" they have ever had anything to do with ... and then there are those that never will.

Rule #1: Don't hot rod your grocery getter/transportation. Mild performance enhancements are O.K., but a strong reality check is advised, even for those that have played the game before.

Rule #2: If you want to build a fire breathing monster, expect to spend a lot of money, spend a lot of time tuning/fixing stuff, and be prepared to learn a lot about the care and feeding of a high performance engine and how to drive same on the street.

It's really that simple ... don't put a Ferrari motor in a garbage truck unless the goal is to get to the dump before everyone else does :>)

[nightmare7306]

I can't comment on this subjet from experience on bikes but I have played with injection on 5.0L mustangs for years.  A strong street/strip motor would respond well with an increase from 60mm stock to 70mm or 75mm. There was a company that came out with a 90MM TB. It has its place, but on a street car it wasn't real civilized. As soon as you crack the throttle on that 90mm it would be moving a pile of air. Properly tuned the car would do exactly what it should, lurch forward. Very touchy throttle. You may be able to tune this so it would not do this but I would not call that properly tuned. As with any motor, when it gets a big gulp of air properly mixed with fuel, its going to take off. Again, I have no idea how big is to big for a Harley, but 90mm was pushing the limit for a street car with good part throttle drivability.

[ederdelyi]

You've got it about right. In the HD world it gets even worse when a big TB is coupled with a cam with a super tight LSA, "high velocity" ports, smallish valves, and super high compression all geared toward making lots of low end grunt and a TQ curve that resembles a light switch (on/off) ... be careful what you ask for, you may get more than you can handle :>)

EDIT: Or find out that the chassis can't handle it and end up replacing lots of broken $hit if you try to use it.

[Zambini]

Ed, that's hilarious, and so true.  The same thing plays out with those 3-engine cigarette boats.  Crazy, man!

[roadglide65]

I just got done riding my 107 all over Denver. In the parking lot and then in a funnrel for a outlaw that was stop and go with about 100 bikes Because of this disscussion I put it through all the slow paces and it works great.   I am sure there are some issues with larger TB on some bikes. I am sure it is like everything else. There are somethings in a build combo that push it over the top. Maybe a 57 mm would have caused it on mine. Also the Tmax might react diffrent than a Sert on a bigger TB.

Hey if you are happy with it let it go!!!!!!!!! 

[Bruno]

I just got done riding my 107 all over Denver. In the parking lot and then in a funnrel for a outlaw that was stop and go with about 100 bikes Because of this disscussion I put it through all the slow paces and it works great.   I am sure there are some issues with larger TB on some bikes. I am sure it is like everything else. There are somethings in a build combo that push it over the top. Maybe a 57 mm would have caused it on mine. Also the Tmax might react diffrent than a Sert on a bigger TB.

It sounds like your auto-tune is doing a great job, considering that the experienced tuners are having so many problems tuning for bigger TB's.
If I ever change throttlebody, I'm going with an auto tuning system. The tuning money that I save will pay for the unit. I sure am glad there is a solution for the TB parking lot issue!

[nc-renegade]

However if you feel you need to replace your entire engine management system, and save money? to get your bike to run properly that would be fodder for another thread. 

Bob,
You think you would be above these statements by now?  This is such a ridiculous statement, everytime you make it......What is the Delphi sacred? (If so, I will erect a shrine for my old one.)

Is this the one component on a HD that is above discussion (for replacement) on this technical board?

[Bruno]

Where did you get the idea tuners were having problems with large TBs? This thread was started discussing the drivability issues as applied to overly large TBs for builds.

Where did I get the idea that tuners were having problems with large TB's?    From you, on this thread.

However if you feel you need to replace your entire engine management system, and save money? to get your bike to run properly that would be fodder for another thread.

It seems that the auto-tune guys don't have the same issues with the bigger TB's. (Again, from this thread). It sure would be nice if some of the other experienced tuners would weigh in on this subject.

[redmtrckl]

Yamaha has solved the bigger is better problem in the V-max (aka Harley Nova) engine with the variable inlet that changes from 54mm to 150mm on the new 09's.
Estimated to be near 200hp this year.
All we need is dual or triple TB's with chip controlled activation above certain RPM.
And more leg room:)

[ederdelyi]

Variable or progressive TB's aren't new ... many superbikes use that technology with great success. Both active intake and exhaust tuning are also used. Much tougher to do on a low RPM motor like the current HD V-Twin. Maybe when the water pumper/V-rod style motors finally enter the model line one might expect some of these things to manifest themselves ... they pretty much had a start on all this with the Nova project. I could get interested in a good V4 water pumper ... always liked the V-Max, wonder why? :>)

[Don D]

HDI has active exhaust and Intake control but these are not performance enhancement hardware.

[ederdelyi]

>>HDI has active exhaust and Intake control but these are not performance enhancement hardware.<<

What HD has is NOT what I (and most others) would consider active intake exhaust tuning ... as you said, performance was not the goal. The Buell active exhaust actully does help a bit, as stated, this stuff is tough to do given the real estate constraints and RPM range of the present HD motors.

On topic: The tuning "issues" with large TB's are not (IMO) an auto tune vs manual tune issue. There is much more to it than that. It's a given that a large increase in throttle blade area wiil result in a much larger percentage increase in area change for a given throttle blade angle. The ability of the system (auto or manual) to cope with that change depends largely on it's maps and the granularity of same. If the system lacks resolution or does not have the ability to adjust the map properly it won't make any difference if the method used to adjust is auto or manual. In some cases, the manual adjustment may be able to come up with a better solution. Why? Because (hopefully) a human with experience is at the helm rather than a program with limited options/artificial intelligence.

Auto tune is a nice thing to have if you have no other way to get 'er done. It is not, in it's present state of development, the end all solution, and for some applications it may never be.

[redmtrckl]

Ok, how about variable ratio throttle cables?

[ederdelyi]

>>Ok, how about variable ratio throttle cables?<<

Old dirt bike racing "trick". Change from a 1/4 turn throttle to a 1/2 or 3/4 turn or the other way around to vary the throttle feel. The new FBW TB's also might help if the software throttle response is played with. Depends on whether or not the aftermarket will step up and support a true FBW TB. I've used the FBW adjustment on cars with large FBW TB's and it does help tame the "beast".

[wfolarry]

Variable or progressive TB's aren't new ... many superbikes use that technology with great success. Both active intake and exhaust tuning are also used. Much tougher to do on a low RPM motor like the current HD V-Twin. Maybe when the water pumper/V-rod style motors finally enter the model line one might expect some of these things to manifest themselves ... they pretty much had a start on all this with the Nova project. I could get interested in a good V4 water pumper ... always liked the V-Max, wonder why? :>)

Rumor out of Milwaukee is that's what we'll be seeing.