dewbries
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 posted on 26/10/17 at 05:33 AM |
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Hayabusa Throttle Bodies For Mk1 MX5 Engine
Hi Guys n Gals,
Has anybody successfully used a set of gen 1 hayabusa throttle bodies on a Mk1 1.8 mx5 engine? I believe the hayabusa is a 1300 and I know folk use
750 gsxr bodies (I think) any advice would be appreciated.
[Edited on 26/10/17 by dewbries]
Second build. Now refining and changing drive train
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SPYDER
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| posted on 26/10/17 at 08:09 PM |
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Hi there. I think they would be too big. Even GSXR 750 ones might be borderline "too big" on a road car. Don't get me wrong, they
will work, the engine will run etc. but even a small throttle opening will let gobs of air in and all manifold depression is gone. Mapping it
wouldn't be easy unless using AlphaN ie. TPS based. Even that brings along its own foibles.
I had a few "driveability" issues on my car using K1 GSXR750 itbs and that is on a 2 litre 3SGE (190hp+) engine. At low revs even a small
throttle opening effectively gives near enough full throttle. A very steady right foot is called for.
I replaced the tiny throttle quadrant with a much larger one and offset it to give a "rising rate" movement. The first 10% of butterfly
opening now uses about a quarter of the pedal travel.
I had a reasonable tune on Megasquirt MS2 using AlphaN but things were improved when switching to the dedicated ITB mode. It gives a blended approach
using Speed Density ( manifold depression) at small throttle openings then seamlessly switching to AlphaN with increasing load.
GSXR750 itbs are good for over 200hp, Hayabusa probably up to 250. If your proposed (130hp) 1.8 engine is otherwise standard ( and for road use) I
would be tempted to consider GSXR600 bodies. You "might" leave the odd hp on the table (I doubt it) but driveability would be
better. If you are chasing the last hp, or you intend to mod further in the future, maybe going to 2 litres, then GSXR750 bodies might make more
sense. Early ones are easy to respace. K1-K2.
Early 750 and 1000 are the same butterfly size. 42mm. Hayabusa 46mm. 600 38mm. IIRC.
What ECU are you proposing?
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