ITB Build Thread

You got fantastic skills there buddy. Very tidy work.

 

How sensitive will these be when setup? (just going on previous threads about using bike parts).

 

Fabulous
I just have to try the same thing some day... if you think of what you get for the little investement (of money, not time etc), it can't be beat... it's the way it should be: inginuity triumphs over budget
Let us know how it performs (and how it handles small throttle openings at low revs)

 

top stuff

 

How do the inlet dimensions compare with the usual off the shelf ITB options?

 

very nice comming along well

 

I take it you are refering to the length of the runners. They are 360mm long from the centre of the valve to the end of the belmouth and are pulse tuned for an engine that makes max torque at 6500RPM. However i'l have to wait to get it on the rollers and play arround with some different length trumpets to see if there are gain's to be had.

They're a bit longer than DTH's but about the same length as the TWM DCOE setup. Most importantly the injectors are about 200mm back from the valve which should in theiry give better atomisation at high revs over the DTH's but whether or not it does is another question.

They will be as sensitive as I want. If i were to connect the cable to the top of the throttle pedal arm then the full throttle travel will be about 25mm of pedal movement and would be a bit on/off. I'm going to mount the cable lower down the throttle pedal arm so that the pedal travel is identical to that of a standard k-jet throttle so don't expect them to be any different to any other ITB's.

 

Great info there again Ray - loads of homework gone in to this clearly.

The actual Q I was thinking of (though that was interesting too) was in relation to the internal diameter of the TBs, ie how the start point of 48mm, down to 42mm would compare with off the shelf TBs. How much do they taper by if at all? (DTH or TWM/or dare I suggest Mangoletzi).

 

looks like a piece of art!

 

Looking good Ray !!!

Can't wait to see this car on the track !!

 

"As with the injector position (see below), higher RPM demands a larger butterfly to valve distance. A practical minimum figure for a 7 - 9,000 RPM engine is 200mm, whilst the maximum is dictated by the need to fit an air horn of reasonable length to achieve a good overall tract shape. One solution to this apparent compromise is the use of bodies with fully-tapered bores which, in effect, extend the trumpet distance beyond the butterfly and into the manifold."

That's the theory behind tapered boddies incase anyone was interested.

DTH's and the like aren't tapered. The only tapered ITB's I know of are the single Jenvey SF boddies used on very high level race engines. Graham put some of these on the 20v .

Reading the Jenvey website they seem to have a taper angle of 4.5 degrees. Over a 90mm long throttle boddy that relates to a either a 6mm or 12mm reduction in diameter depending how the 4.5 degrees is measured which seems prity similar to the taper on the Suzuki throttles.

 

Ive done quite a bit of playing around with inlet length and suprisingly have never seen much of an effect, couple hp here or there, probably depends on engine spec. One of things I like is very instant throttle response, goes back to racing bikes I think, (and why turbo's are so frustrating to me on track), but this is one of the big benefits with dth and having the injector and butterfly so close to the valve, as you move injector and butterfly away, this diminishes but 'in theory' as you say, you should get more power - trade off of what you want/like and ultimate figs - could have got another 16hp from my motor but settled for red hot throttle response and midrange as, for me at least, these are quicker. Good work, youv'e clearly thought this through.

 

and some engines do better with parallel trumpets - go figure - seems for every rule there are plenty real world examples that defy them

 

Nice work there! Looks very neat. Hope you get the results you're after.

Gurds

 

Great - so you have really engineered a like-for-like for a quarter of the money by the look of it. That's ace, and something others could repeat.

 

Looks exellent Ray, looking forward to seeing it in the metal !

 

Top work!

 

any updates before xmas .

 

Great project. However love to see more detailed pic as to where you got vacumn and MAP.... inspirational

 

some nice work..

worth mentioning is injector type and delivery spray pattern where you mention "better atomisation" as this can be achieved by injectors.

Genesis injectors over on vortex have some nice delivery characteristics, twin cone delivery etc.

just a thought.

Also, when I played with the DTH bodies originally (and my slide throttle before that) he longer I made the induction tract length the better it got, more torque than bhp, but it got better the longer I went until I ran out of length.

nice work.