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The mkiv Supra Owners Club

Crower 3.4 stroker kit?


JamieP

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Are you saying the kit is no good then Chris?

 

Yes, the material spec isn't good enough for such a long stroke, small overlap crank. Using buttons to retain the piston pins is really cheap and horrible. Beloved by Yank drag engine builders as they can remove pistons from rods without tools, in seconds, and failsafe in the hands of incompetents. They knock like hell as they wear, mark the bores and are really a drag engine "thing" only. They should have round wire circlips and chamfered pins. These things are on a par with Spirolox retainers, another abortion from over the pond :)

 

Doug Kiddie (Arrow Precision), Farndon and Phoenix will agree with me over crank material specs. Any engine builder wil agree over using buttons in a road engine destined to do any sort of mileage. CP pistons need a mass of bore clearance due to the (poor) alloy used. I believe you like to spend money, and your car deserves better. Jun pistons and a decent crank material will make your investment a lot safer. Personally I think the stroke out at 3.4 is a bit excessive. They might survive over 8000 revs for a few drag passages, no way would I want to turn those sort of revs, long term, on that sort of stroke, unless it was a properly built S312 ccrank with proper accompanying mods. Even then 8K and (shudder...) above is a LOT of revs on a long wobbly crank.

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Yes, the material spec isn't good enough for such a long stroke, small overlap crank. Using buttons to retain the piston pins is really cheap and horrible. Beloved by Yank drag engine builders as they can remove pistons from rods without tools, in seconds, and failsafe in the hands of incompetents. They knock like hell as they wear, mark the bores and are really a drag engine "thing" only. They should have round wire circlips and chamfered pins. These things are on a par with Spirolox retainers, another abortion from over the pond :)

 

Doug Kiddie (Arrow Precision), Farndon and Phoenix will agree with me over crank material specs. Any engine builder wil agree over using buttons in a road engine destined to do any sort of mileage. CP pistons need a mass of bore clearance due to the (poor) alloy used. I believe you like to spend money, and your car deserves better. Jun pistons and a decent crank material will make your investment a lot safer. Personally I think the stroke out at 3.4 is a bit excessive. They might survive over 8000 revs for a few drag passages, no way would I want to turn those sort of revs, long term, on that sort of stroke, unless it was a properly built S312 ccrank with proper accompanying mods. Even then 8K and (shudder...) above is a LOT of revs on a long wobbly crank.

 

Thanks Chris, im looking into what you have said.

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Yeah but I think Chris was saying Vvteye after multiple passes things would start to let go!

 

I'm sure Jamie can ask those who use it for opinions if that is what Ryan Woon has.

 

Maybe Jamie should get hold of the kit to show us what it is or isnt capable of :)

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Also, how can a bottom end with a smaller L/R ratio have a higher safe top end speed than stock? Just putting the kit on will increase the mean piston speed and TDC acceleration, without over revving it.

 

Anyone know what the piston masses are compared to stock?

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nice Nic... whats that going to cost?

 

About £8000 plus shipping and duty - Titan have it listed for $14,500 at the moment, for comparison their own kit is $8,895 and the HKS $11,915. The Crower 3.3L (is it?) is $6,824, it's a budget option as far as these things go.

 

A set of JUN pistons for the Supra is $2,110, JE or CP ones cost around $750 a set - I guess all that postage from country to country adds up ;)

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Also, how can a bottom end with a smaller L/R ratio have a higher safe top end speed than stock? Just putting the kit on will increase the mean piston speed and TDC acceleration, without over revving it.

 

Anyone know what the piston masses are compared to stock?

 

The CP's are about 3/5's the weight of the stockers. Same goes for the Rods.

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The CP's are about 3/5's the weight of the stockers. Same goes for the Rods.

 

 

It's trivial to make a lighter piston than the stock Toyota ones when you cheat and delete the wonderful hollow oil cooled crown. It's very trick if you want a forged piston WITH the oil cooled hollow crown, both to forge, and to keep below the stock weight. Tomei managed it with their RB26 forged hollow crown pistons, but they are very expensive. I have never seen 2JZ-GTE forged pistons with oil cooling. By FAR the best piston is the Cosworth one, marketed by JUN. Any serious engine should have these, they are poles apart from the likes of CP and stuff.

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The CP's are about 3/5's the weight of the stockers. Same goes for the Rods.

 

 

OK, assuming (reading Chris' post above) that they hold together that would just about make things equal as far as intertial loading goes. The stock loading at 7000RPM is about the same as an assumed 3.4litre at 8500 with a 2/5 reduction in reciprocating mass.

 

3.4

rod length: 133mm

crank throw: 49mm

Inertia load (assume 0.48kg rod and small end mass) 25kN @ 8500

 

3.0

rod length: 139mm

crank throw:43mm

Inertia load (assume 0.8kg rod and small end mass) 24kN @ 7000

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OK, assuming (reading Chris' post above) that they hold together that would just about make things equal as far as intertial loading goes. The stock loading at 7000RPM is about the same as an assumed 3.4litre at 8500 with a 2/5 reduction in reciprocating mass.

 

3.4

rod length: 133mm

crank throw: 49mm

Inertia load (assume 0.48kg rod and small end mass) 25kN @ 8500

 

3.0

rod length: 139mm

crank throw:43mm

Inertia load (assume 0.8kg rod and small end mass) 24kN @ 7000

 

How about a 3.2 that is about 4/5's the weight of the stock system? The Jun/Cosworth pistons arn't light...but they are a little lighter than stock.

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