Bike Throttle Bodies- Best Diameter?

[Guest mattyj]

Hi

 

Been researching this for some time, but i just want some opinions on the set up i should choose. I'm lookin at the moment at 46mm diameter bike tb's, do you reckon this is too big for a 1.9 8v? will be changing to a MI 16 in the future tho.

 

thanks

Matt

[M3Evo 0]

Reckon that it probably a bit big for an 8v.

 

The ports on the 16v head are only 40mm diameter!

 

Supposedly 40mm bodies are good for about 50bhp/cyl (think that was from the jenvey site?)

[pugpete1108 62 1 Cars]

Hi

 

Been researching this for some time, but i just want some opinions on the set up i should choose. I'm lookin at the moment at 46mm diameter bike tb's, do you reckon this is too big for a 1.9 8v? will be changing to a MI 16 in the future tho.

 

thanks

Matt

 

i have been reasearching this on here for a while for 1.9 ,but have given up and am looking for mi power instead as i was told there is no manifold to fit bike tb's on an 8v unless you use a carb on and keep the bike injectors ( which i didn't want to do) , so mi it is and then i will fit bike tb's and see how we go woo hoo.

pete

[Dom9 2]

I'm sure there are manifolds to fit bike TB's to the 8v from Bogg Bros. and Shenpar...

 

40mm is adequate for about 200bhp, 46mm is serious and probably not worth it!!

[RobMGti 0]

I'm sure there are manifolds to fit bike TB's to the 8v from Bogg Bros. and Shenpar...

 

40mm is adequate for about 200bhp, 46mm is serious and probably not worth it!!

 

Dom is right, as per my reply in the other thread i believe Bogg Brothers have allready done at least 2 8v's and numerous 16v. A shenpar one was recently sold on Ebay, ill try and find the link

[Dream Weaver 2]

40mm on mine and had my first drive in it yesterday - its absolutely stupidly quick now

 

If you stick with the 8v just have a manifold made. Just get some straight runners ally welded onto a flange then fit some GSXR bodies onto it.

[Baz 421]

40mm on mine and had my first drive in it yesterday - its absolutely stupidly quick now

 

If you stick with the 8v just have a manifold made. Just get some straight runners ally welded onto a flange then fit some GSXR bodies onto it.

 

GSXR750s are 40mm then?, as i have 600s- but not sure if they're right for an Mi. What manifold are you running?

Edited February 6, 2006 by BazGTMi

[d-9 0]

Dream Weaver, got any detailed photos of your setup?

[cybernck 402 1 Cars]

there should be plenty in his massive topic i'd have thought?

 

or did you mean more detailed?

[d-9 0]

Please excuse me, im stupid *goes to look for massive topic*

[Dream Weaver 2]

LOL There are some pics in my topic.

 

A few pics below.

 

 

Edited February 6, 2006 by Dream Weaver

[Dream Weaver 2]

All pics I have shown above, didnt take that many really whilst I was building, too keen to get them done

Edited February 6, 2006 by Dream Weaver

[DrSeuss 0]

when you mounted them on the manifold. Did you port match them to the manifold?

[Dream Weaver 2]

Yes, and it was a right ballache.

 

I had to fit the bodies to the manifold, and angle the top of the Samco hose away - this brought them much more in line than I had managed before.

 

If you look at Pic 3 you can see some pen marks on the inlet. This is where the manifold was ported, but not as deep down in the end, as those marks are from the initial fitting with the Samco's straight.

 

I then got the Dremel out, and through 4 hours of trial and error, fitting the bodies, removing them and Dremeling, fitting them back on etc all of the bodies were perfectly matched to the manifold so under the Samco couplers is a smooth transition from body to inlet.

 

I had a stroke of luck in that I got a 300 and 200 piece Dremel set in the B&Q bargain bucket sale which cost me £3 and £2 respectively (retailed over £60) as I used a huge amount of the grinding stones, sanding discs etc - it would be easier with a Die-grinder, but they are dear.

[DrSeuss 0]

Lower your rad and fit long trumpets. I oh so desperately want you to prove all the bike tb doubters wrong. Not as much as you do no doubt

[Dream Weaver 2]

I will be doing that. I also want to prove people wrong

 

There is one problem though, the throttle angle is very small with bike TB's, so the pedal is tricky to use at low speed, seems to be either on or off

 

Just want to get it running properly first and ensure the engine is OK before putting any more time and money into it, the compression readings were worrying the other day (200-150-180-200), though it is a fresh rebuild so that may be the reason. The oil pressure was also half way when warm, and there was no blue smoke out the back so maybe the compression tester isnt that good.

 

I have some 60mm trumpets here which will fit with a little work, so just a filter to buy and then the rad to lower using some brackets.

 

When I take it for mapping I will take both the current filters (without trumpets), plus the trumpets and new filter to see what the difference is.

 

Before all of that though, I need a new rear beam and brakes - everything is seized due to being sat so long More money needed

[Dom9 2]

Lower your rad and fit long trumpets. I oh so desperately want you to prove all the bike tb doubters wrong. Not as much as you do no doubt

 

I don't really understand why they are any doubters... There have been plenty of poor results with 'normal', 'comercial' TB's, so I don't know why people jump on bike TB's... I guess the problem is that most applications have been home-made and so the fit and finish hasn't been as good out of the box and they haven't worked so well. In reality, all TB's are just tubes with butterflies in them, doesn't matter whether Yamaha made them for a bike or Jenvey made them for a car, or you or I made them out of an old drain pipe, they should all pretty much work the same if we pay attention to detail.

 

 

I will be doing that. I also want to prove people wrong

 

There is one problem though, the throttle angle is very small with bike TB's, so the pedal is tricky to use at low speed, seems to be either on or off

 

Can't you just lengthen the arm the throttle cable attaches to on the TB's??

 

As for the compression readings... They are a bit low, well, the 150 at least... Give it some running in time, watch the water and oil, then re-test after some miles I guess?!

[M3Evo 0]

Took me ages to design/build a reasonable linkage for my TBs with decent pedal weight and travel.

 

If you can be arsed, I reckon it's gotta be worth designing a progressive linkage so that at the beginning of the pedal travel, the butterfly opens by proportionally less than at the end.

[tom_m 0]

There is one problem though, the throttle angle is very small with bike TB's, so the pedal is tricky to use at low speed, seems to be either on or off

 

you should be able to get round this by putting a cam on the throttle cable so it slows down the opening at low pedal angles. Its been done before iirc, but can't for the life of me remember who's done it!

 

hope this helps

[DrSeuss 0]

Couldn't you just chop the throttle cam off a standard throttle body then bodge it onto the bike throttle bodies? An adaptor plate here etc. and it'd give you something approximating your original throttle pedal.

[Dream Weaver 2]

I will try all these things once its running, its certainly "liveable" as it is.

 

I also cant understand the doubters, bike TB's may not be quite as good as Jenvey etc, but my setup has got to be better than the std single TB/butterfly.

[Dom9 2]

I will try all these things once its running, its certainly "liveable" as it is.

 

I also cant understand the doubters, bike TB's may not be quite as good as Jenvey etc, but my setup has got to be better than the std single TB/butterfly.

 

I don't even like using the word 'better'... Jenvey's, off the shelf, may not even be 'as good' as well set-up bike TB's, we really just don't know... The reality is that all TB's should pretty much work the same if the linkages are sorted, there are no leaks and they are port matched etc!

 

As for throttle cams, there are plenty out there! All the Porsche 944 boys bin theirs to go back to a non-cammed linkage... I bet you can find one of those for nothing on eBay or on a Porsche 944 forum!

 

You are right though, get it up and running first and maybe before the final map, get a more progressive linkage in there and the jobs a carrot!!

[Dream Weaver 2]

Or maybe a turnip

[Guest mattyj]

Thats great guys, i was lookin at the early GSXR 750 tb's that are 46mm diameter as they didn't have second throttles, but the later ones with the second throttles are just as good with the second throttles removed i guess, i was told they taper from 45mm to 40-42mm which would be ideal, as for the manifold. Im makin a bespoke alu one myself, just finalising the drawings now. I'm also planning on using the bike injectors as far as i can find they are 230cc per min which should be enough fuel, but it's easily changable. not sure what gains i'll see tho?? thinkin of using a Xu10 head as well but agian i can't find that much evidence on how well they'll do??

[cybernck 402 1 Cars]

we really just don't know... The reality is that all TB's should pretty much work the same if the linkages are sorted, there are no leaks and they are port matched etc!

the difference will mostly come from the manifold used and that's why there are so many "doubters".