Bonneville America Forums Forums Technical Forums Performance Mods Jetting Chart, need input here

When I first started thinking about pipes/jets/airbox modifications, I thought a jetting chart would be great. Each air breather mod would get a value in corresponding jet size. I have never seen such a chart, but here is mine based on my own guestimates. The reason for the negative numbers is that all mods are cumuliative and may offset the others. I.E. TBS needles allow more fuel at half to WOT (yes?), slightly offsetting the need for larger jet size. Keep in mind that the precision of these values is based entirely on WAG theory. (Wild-Assed Guess)

Jump in guys and gals. I need input here. Don't be afraid. (I know you won't) Also, what values have I left out. Does anyone take exception? The exhaust pipe values are just a gut feeling based on what I have read in these forums over the last three years.

In deference to the old wise ones (you know who you are), I understand that the interplay of the variables here is almost impossible to predict; like predicting the trajectories of 3 co-orbiting stars....all but impossible. But it might give the newbies a base to work from. It might get you in the right parsec.
(This was my little attempt at humor, because as all Trekkies know, a parsec of space is a pretty big place.)

----------------------------------------

Base OEM Jet +120
Stock OEM pipes +0
Pull AI +0
Pull snorkle +5
Drill airbox +5

Remove baffles +3
TORs +2
Bubs +7
Epcos +8
S Spares +7
TPipes +4
Septres +10
Staintunes +5

TBS needles -2
Thrux needles -2
.5mm washer -1
45 pilot -1
48 pilot -3
Freak +30
Ea. 2000 ft above sea level -1
-------------------------------

Example:
Base OEM Jet +120
Pull AI +0
Pull snorkle +5
Drill airbox +5
TORs +3
-------------------------------
Jet Size +133 (or closest)


Example:
Base OEM Jet +120
Pull AI +0
Staintunes +5
45 pilot -1
Freak +30
--------------------------------
Jet Size +154 (or closest)

Nifty idea... great starting point in my opinion. Obviously (as you've already said) it's not definitive and would require further testing to get it perfect but this should get you into the right ball-park.

I'd guess gutting standard pipes would give about the same value as TOR's (+3). What value for a freak kit then? +10 since it's similar to a drilled 'box + removed snorkle? Maybe a little more... +12 perhaps? I like that you've included a 0 for the AI, would stop the constant repitition of "what value is the AI?"

With a little input from the "old & wise" this should go into the tech vault, in my humble opinion.

Matt

Sandman,
I edited my post and added your suggestion for drilled out baffles. At first thought I would have guessed a higher value than +3. But then I followed this logic: Triumph probably made some attempt to tune the stock pipes for scavenging and pressure drops. Drilling the baffles would corrupt any factory tuning and actually negate what you are trying to accomplish. It's true that you free up the exhaust path, but scavenging and other tuning methods are just not there.

Cody

I'm thinking further about the baffles. It occurred to me that some are drilling holes in the baffles, and others are removing the baffles entirely. What would be the difference?

Drilled +3 ??
Removed +5 ??

I'm just guessing here. I have no real experience about this.

Cody

Maybe do a -1 for each 1500 - 2000 ft altitude.

Thanks Greybeard. I edited the entry for altitude. I don't know how long I can edit a post. I might have to turn this over to a moderator.

Cody

I think this is an excellent idea. In fact we could make it into a simple program, like the Dinkulator, or a spreadsheet and this would simplify a lot of the guess work. Once I get over my current disease, feels like bronchitis now, and my head works again, I'll look into writing a program for it.
Definetly worth putting into the tech vault too.

Would that then make a UNI [+5]? seeing that I and most have 130 mains when they are

-desnorkled, UNI, TOR's. Also does that mean when you go to 45's for pilots that you should go down in the main by 1 point. Or am I not understanding this.

BikerT

0pps, I meant +2 for the UNI

-desnorkled +5 , UNI +2, TOR's +3 = 130 Mains

BikerT

Just as I thought. My mains too big. Thanks for sharing your research.

Would D&D pipes be a +10, or more?
Would you add +30 for the Freak & +5 because the snorkle is gone?

Of everyone that is running TBS needles, does everyone need to shim them at least twice to make up for the lenght of them? If so, and figuring for instance, 2 shims is a standard when using TBS needles, maybe these needles could be a +0 because you would count a -2 for the two shims you put on. Otherwise, TBS needles would be a -4 right away.

Great Idea, I'd like to see where this thread goes.