Hi there,
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Welcome to IMOC.
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Differences between revision 1
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& 2 engines and revision 3
Just a quick list, do not take any of these as gospel:
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* position and orientation of oil filter changed.
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* different internal engine parts, e.g.
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pistons, con-rods etc.
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* turbo charger changed from Garrett CT26 to CT20
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(same intercooler though).
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* boost pressure raised from about 10 to about 13 PSI.
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* power output raised from 220 to 240 BHP.
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* compression ratio slightly lowered.
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* injector size increased from 430cc to 540cc.
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* fuel cut threshold raised from about 12 PSI to about 18 PSI.
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* head and inlet path completely redesigned.
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TVIS removed, 8
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'independent long ports' reduced to 4.
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* throttle body increased from 55mm to 60mm.
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* inlet valve lift increased from 8.2 to 8.7.
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* different, smarter engine ECU, more tolerant of poor fuel, different connector pin out.
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* air flow meter removed.
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* intake manifold inlet air temperature sensor added.
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i.e.
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after turbo and intercooler.
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* ECU now modulates the turbo VSV to achieve variable control of boost pressure rather than either open/full or closed/reduced.
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Control of boost now quite subtle when ECU is unhappy because of temperatures, detonation, speed, etc.
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* location of valve shims moved
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(someone said this was to stop problems with them falling out).
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Note this makes adjusting the valve clearances a much bigger job as on the revision 3 it involves removing the camshafts
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(might as well replace the timing belt whilst you're at it).
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* exhaust valve clearance increased by 0.08 mm
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(probably.
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valve clearances is one question I'd like answered direct from Japan.
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They are probably the same as the UK GT4s, but it would be nice to be sure).
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* oil pan changed from a one piece pressed steel part to a two piece affair, the upper half being aluminium, the lower half being pressed steel.
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* No.
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1 compression ring now described as
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'stainless steel' in GT4 manual/supplement instead of just
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'steel'.
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Oil ring is described as
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'stainless steel' instead of
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'a combination of steel and stainless steel'.
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No.
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2 compression ring remains described as
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'cast iron'.
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* idle speed perhaps slightly reduced
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(need to check this out on a rev 1 or 2 car, my stickers say 750 rpm, I've a feeling rev 1
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& 2 was 800 rpm).
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* exhaust part numbers changed.
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Revision 2 part number for the front pipe is superceeded by the revision 3 front pipe part number.
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Back-box part numbers different.
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Unknown to me whether they are actually different.
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I would say get the best condition car your money will afford.
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I would personally prefer a mint rev2 to a trashed rev3.
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All cosmetic differences can be easily made to make a early model look like a later model so if looks are the main concern maybe budget for a few hundred to bring the cosmetics up to date.
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Regards
Esmond