reasonably priced ITB kit

[colin86325]

I just came across these today and they look to be reasonable priced.  They come in 42, 45, or 48mm sizes.  Does anybody know what size the Dbilas kit is that everybody says is too big?

http://www.racehead.com.au/?page_id=195

[wazzu70]

The dbilas throttle bodies are 45mm, S14 OEM are 48mm, and Euro S50 are 51mm.

I dont think dbilas are too big, but I think S50 throttles on a M42 street care are a bit big.

FWIW, getting the throttles is easy. The manifold from the head to the throttles is whats difficult.

[colin86325]

I see that Dbilas offers an adapter for the cylinder head.  Or one could get creative and machine part of the stock manifold for this.

Thanks for the info on the Dbilas size.  I seem to remember people faulting them for being too large, but 45mm is not too large according to some rough calculations.
BTW the S14B23 used 46mm, and the S14B25 used the 48mm throttle bodies.

[Tgoode318]

besides the adapter what else would be needed to get these working?

[colin86325]

You'd probably want ram tubes. Either the nice ones shown or others (even plastic ones).
Then either use individual sock filters on the ends, or ideally create a tuned plenum to house the ram tubes. You could even fashion a plenum from fiberglass.

The adapters to the head would need bungs for the fuel injectors.  Maybe that would mean that modifying the stock intake manifold would be an easier option.

[bmwman91]

Pretty cool. I have always sort of wanted to try to build an "OEM looking" ITB setup by mating ITB butterflies to a modified stock intake manifold, although the plenum may not be quite the ideal size. Anyone with a dBilas setup have an approximate volume for the plenum (or better yet, a set of measurements giving diameters and lengths of everything)?

One big parameter is selecting the distance from the butterflies to the injectors & ports. Too close and you get lousy fuel mixing, too far and you start eating away at the improvement in throttle response.

[MLM]

dBilas diameter is 45mm
Plenum volume 6.5L approx.
valve to opening in airbox is approx. 285mm though don't have a full set up to measure as I created my own airbox and runners which were longer at 420mm which gave a peak torque at 4300rpm. I think the dbilas one is a bit short really.

I didn't get much power out of it, cams is probably the key to that but the sound is epic.

[wazzu70]

I see that Dbilas offers an adapter for the cylinder head.  Or one could get creative and machine part of the stock manifold for this.

Thanks for the info on the Dbilas size.  I seem to remember people faulting them for being too large, but 45mm is not too large according to some rough calculations.
BTW the S14B23 used 46mm, and the S14B25 used the 48mm throttle bodies.

Good point on the S14 throttles. The 48mm are the ones people upgrade to from thr S38. I just remembered the upgrade number

Machining the stock manifold my not work as the difficult part is the correct runner spacing for the DCOE throttles. Its worth investigating for sure though.

I have thought of designing an intake manifold to accept the individual throttles and 3d printing it out of ABS or ULTEM since production volumes would be low. Then I decided my car sounds pretty wicked using just the open throttle body on the stock intake. Also the dbilas one is great and isn't rediculiously expensive so there is no reason to reinvent the wheel.

[MLM]

Who would do the fdm for you nick?

Pricing on a cnc ally adaptor from china is about 450us for a reasonaby complex design. (pug mi16). Plastic options cnc or fdm are availble to but ABS and many other common grades etc are not petrol resistant. If you need need contacts let me know.

[wazzu70]

We have a few places locally that have the big Stratasys machines for large parts.

There isn't much petrol/ethanol in the manifold as its all directed into the head and atomised. Obviously there is some residual in the runners (tau) but not enough to cause issues. I have talked to additive manufacture shops in the past that make auto and motorcycle inlet manifolds without issue.

[MLM]

All good We use statasys too in fact a new machine arrives today.

I mention the potential for plastic degredation as reversion can blow fuel back out the intake if particularly bad and an fdm would need sealing


If anyone want a more detailed photo and measurements of the Dbilas plenum let me know, its just a paper weight for me at the moment.

[colin86325]

Is fiberglass suitable (gas resistant) material?  I saw a pretty cool fabrication trick for making runners. The guy used a section of inner tube from a bicycle and filled it with sand.  Then he coated the rubber with release compound and formed it into the curved shape that he wanted.  He then applied the fiberglass and when it was cured he simply emptied the sand from the inner tube and removed it from the glass shell.

It would be cool to see some more measurements and pictures of the dbilas manifold if you have the time...

[MLM]

Fiberglass (the fibre) is resistant, its the resin you use which needs to be resistant to heat and chemical. I used a Vinyl ester resin on the recomendation of a local supplier.

Will post pics up when i can and an amateur attempt at airflow analysis which shows why its not the best desing nout there.