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Post by BikeTuna on Dec 19, 2016 13:09:25 GMT
So from looking, a lot of peeps go for the GSXR 600 or 750 throttle bodies for their homebrew conversions, I'm guessing this is either because they line up to the ports nicely or that they are just common and easy to find...
The question is regarding restriction in size - Is there any gain in getting a larger throttle body to allow more air in? What if there was also a turbo involved? Would you need a bigger throttle body to allow for the increased airflow? |
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Post by atlex on Dec 19, 2016 13:28:18 GMT
turbos squeeze more air into the same space.. you'd need a nice pressure-tight manifold over the ITBs.
after a point larger holes / spaces don't gain you much, because they move air more slowly.
most folks don't bother with turbocharging on ITBs.
bigger flow means better headwork, or turbo. after some point you need both and spending 000s. or getting lucky with second hand parts hence GSXR stuff, which are both very common and very spare from when people drop/upgrade their bikes.
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Post by BikeTuna on Dec 19, 2016 14:28:20 GMT
I've seen a couple of turbo/ITB builds and it looks like a laugh, even if it is a lot more difficult for a little gain, though with other things going on in life that have a knack of stopping car play any idea would really be a long way off.
But it's good to know that if I went ITBs I wouldn't have to change them if I FI them at a later date.
Cheers!
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Post by atlex on Dec 19, 2016 16:28:41 GMT
The other thing is that ITB builds tend towards increasing the compression ratio because that is a fundamental number to power where you aren't forcing induction... and turbo builds tend to want to reduce it, because you use the turbo to increase the dynamic compression ratio. pick one ?  revs. |
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Post by BikeTuna on Dec 20, 2016 10:34:07 GMT
I see what you are saying, if you were to continue building a ITB based engine you would do things different to a FI build, but I would imagine that if you was doing a FI build using ITBs you would build the engine for the turbo and just use the ITBs for a more accurate A?F ratio control than a singular TB?
Also, on the subject of ITBs (without the silliness of turbos attached), why do they use more fuel? Apart from equalising the intake lengths and giving individual cylinder fine tuning ability surely the injectors are still doing the same thing?
(unless is just because they make such a great noise that drivers just rag them everywhere)
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Post by martiny on Dec 20, 2016 12:01:45 GMT
I don't think anyone uses ITBs for fine AFR control, unless I'm missing something.
They're used for instantaneous throttle control by minimising the throttled volume and for power increase due to discarding the restrictions in a long intake tract, but the compromises include the difficulty of balancing the flow of all four throttles which, if anything, will tend to make AFR control less accurate. With a conventional single throttle and manifold, the imbalance is down to how well designed the manifold is to even up the flow to all four runners.
If you use them with FI you have to contend with both forms of imbalance - the manifold design and the throttles.
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Post by retrorodster on Dec 21, 2016 10:02:13 GMT
There's a fair few builds on MT using larger (single) throttle bodies and making more power. As for boosted ITB builds, there's Matt Mann's drag Miata which is all over Instagram etc, another drag mx5 down in New Zealand, and I have seen some others but can't remember details. The place to look for inspiration on boosted ITB setups is rallycross - seems to be almost the standard there. I imagine that throttle response is paramount for them given how much time those cars spend sideways. www.stavtech.co.uk/home/rallycross-the-maddest-road-car-based-engines-in-motorsport |
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Post by Rickster on Dec 21, 2016 11:52:45 GMT
Cool, I really like the ALS thing - "like driving a 12 litre normally aspirated from a 2 litre turbo"
Ooh that sounds right up my street
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Post by Rickster on Dec 21, 2016 12:16:58 GMT
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Post by atlex on Dec 21, 2016 12:22:23 GMT
one of the most entertaining car/rally tech reads I've read.. in a long time. tempted to look for a turbo hanger now too |
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Post by Ptichka on Dec 22, 2016 14:53:11 GMT
Hahah, those stavtech pages were well worth a read!
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Post by retrorodster on Dec 22, 2016 15:24:09 GMT
Probably the most informative and entertaining journo working in automotive media these days, I've been following his work since Redline.
Hopefully I should get my ITBs on this year. Boost can wait...
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revs.
le sigh