bored throttle bodies

pcs

pcs

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40mm throttle bodies smh, that is gsxr750 sized. even bored out, the gen 3 busa tbs are still smaller than the gen 2. plus 3mm doesn’t sound like much but x4 for the total area. that will open up extra breathing. im wondering if combined with shorter velocity stacks, the bigger tbs will allow the busa to continue to pull towards the top end. im sure some shops have already dynoed and have the info but i cant find anyone sharing.

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SS4Luck said:
Our conversation on this had me thinking about it and when I pull everything apart to put my turbo on I may send mine out.


That doesn’t do much for us with stock motor data, but I’m slowely changing my thoughts on bored TBs on this bike.
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If you are putting a turbo on, I wouldn't worry about modifying the TB's at all, unless you have already done EVERYTHING else you can think about doing to the bike.
 
Has anyone tried this yet? Ive been kicking this around a bit more and with the winter months coming ........

Anyhow I have a few thoughts / points Ive thought about. So Gen 2 and many other bikes that Suzuki make has secondary throttle valve in the way. Gen 3 does not. Less turbulent airflow and nothing in additional in the way. So 3mm is huge gain airflow wise. Also for those who go turbo secondaries tend to get slammed shut sometimes. So those who are either doing the TTS or a Turbo kit would benefit from better flow. Will this make huge gains absolutely not. Will it allow for that finishing touch on top of the build Id say you might get a couple hp on a big bore build or on a forced induction build. Theres a reason HTP made their own plenum and went to a different throttle body. I wonder if @powerfulone has tested a larger opening yet. Maybe Moparbusa could test it on his. We are still in the adoloescent stage on the GEN 3.


Another completely different direction with this thought is head intake port size. How large is the intake opening on the Gen 3 heads? I would almost bet that porting the heads would far outgain porting throttles. If the throttle body is 43 mm but the head opening is still 40 mm there would be no real net gains. This is where it has to become an entire complete approach with all the variables known and calculated.
 
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Ked0607 said:
Has anyone tried this yet? Ive been kicking this around a bit more and with the winter months coming ........

Anyhow I have a few thoughts / points Ive thought about. So Gen 2 and many other bikes that Suzuki make has secondary throttle valve in the way. Gen 3 does not. Less turbulent airflow and nothing in additional in the way. So 3mm is huge gain airflow wise. Also for those who go turbo secondaries tend to get slammed shut sometimes. So those who are either doing the TTS or a Turbo kit would benefit from better flow. Will this make huge gains absolutely not. Will it allow for that finishing touch on top of the build Id say you might get a couple hp on a big bore build or on a forced induction build. Theres a reason HTP made their own plenum and went to a different throttle body. I wonder if @powerfulone has tested a larger opening yet. Maybe Moparbusa could test it on his. We are still in the adoloescent stage on the GEN 3.


Another completely different direction with this thought is head intake port size. How large is the intake opening on the Gen 3 heads? I would almost bet that porting the heads would far outgain porting throttles. If the throttle body is 43 mm but the head opening is still 40 mm there would be no real net gains. This is where it has to become an entire complete approach with all the variables known and calculated.
Click to expand...
I'm in the process of buying a second set of throttle bodies from a friend and going to have them ported. If they get here before my turbo does I'll be able to test them back to back on my bike stock motor still. I won't have a dyno but with my Maxx I'll be able to post fuel correction from the auto tune and we'll see if the bike needs a statistically significant amount of fuel, then let it tune itself and see a difference in performance. If it lines up that I have boost before they get here I'll still do the comparison it just won't be as relevant for you guys.
 
SS4Luck said:
I'm in the process of buying a second set of throttle bodies from a friend and going to have them ported. If they get here before my turbo does I'll be able to test them back to back on my bike stock motor still. I won't have a dyno but with my Maxx I'll be able to post fuel correction from the auto tune and we'll see if the bike needs a statistically significant amount of fuel, then let it tune itself and see a difference in performance. If it lines up that I have boost before they get here I'll still do the comparison it just won't be as relevant for you guys.
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Where are you planning to get them ported? HTP or Maxbore?
 
after boring throttle bodies I would assume the gen 3 stacks will no longer fit, anybody know if Gen 2 stacks would fit?
 
SS4Luck said:
Imma put together a group collection to get my TBs done so I can finally just test this and put this thread to bed hahaha. If the Instagram morons can get mods through crowd sourcing I may as well try too hahahaha
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also interested in boring TBs but then the stacks won’t fit snug and will have a gap between stack and TB. Know of a way around this? Maybe modify the stacks somehow to match the interior diameter of the new TB bore size?
 
Johnnysinz said:
also interested in boring TBs but then the stacks won’t fit snug and will have a gap between stack and TB. Know of a way around this? Maybe modify the stacks somehow to match the interior diameter of the new TB bore size?
Click to expand...
The two different stacks I’ve had don’t have enough material to allow that. The TB base is the choke point of the intake anyway and I bet even taken out the 2mm or whatever they get out of it wouldn’t create a sloppy fit in the top. If I remember right there is a recess for the stacks to slot into anyway and I’m sure you could use a thing layer of permatex to eat up any gap if need be. I just got word tonight my turbo kit is done so tb’s are back on the bottom of my list of money items
 
pcs said:
the stacks bolt up to the airbox to stay in place. they do taper down to fit inside tb however it’s not hard to cut the the taper portion of the stack since it’s made of plastic.
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A little bear of silicon where the stacks fit at the bottom of the actual airbox would solve any spacing issues. I really cant see it being more than 1 or 2mm of possible gap. An adventurous person could probably even cut the bottom of the stack off that has the shoulder on it and seal the whole thing just to the bottom of the airbox so as soon as it went through the venturi area of the stack it was full width into the neck of the TB
 
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