Forged Pistons

[Bradders]

Reading with interest the Crossflow upgrade thread.

 

With regards the forged pistons, am I to think with no head work or other tuning that they are still a benefit? Sorry if that's a numpty questions.

[myothercarsa2cv]

As I understand it, the benefit will be extra reliability (which you don't really need on a standard engine, but will be good for the future) and less mass flying around in the engine which will have a similar effect to a lightened flywheel, i.e. motor spinning more freely.

 

Unless of course you go for higher compression pistons which will give you a few extra BHP.

 

If you have it in pieces, you might as well do the head at the same time, saves on labour. I wouldn't bother doing it on its own, personally. Do you have a lightened flywheel? That might be a better first step.

[Roger King]

They are worth doing on their own. Typically you'll gain 8 to 10bhp if nothing else is changed. This is due to better sealing of the rings + greatly reduced running friction. The reduction in mass is all to the good too - we're talking about several ounces difference.

 

It really does work; in fact reducing internal mass and friction are two of the big aims of modern engine design for these very reasons.

 

Of course, you can then take other things further too.

[gundersen]

Would these gains translate to the k-series?

[Roger King]

Not really, the K is much more modern and the components reflect that. The standard Crossflow pistons haven't changed since before Noah took up boatbuilding.

[Roger Ford]

But K-series standard pistons have a habit of breaking up under heavy load (racing or hard trackday use) so it's worth doing on a K-series as well.

[halstock]

I was asking Dave Andrews (hi Oily ) a few questions recently about potential upgrade paths for my 1600K and he advised that the standard pistons are only deemed safe up to about 160bhp and anything above that would need forged.

 

Andy

[David Brown]

Always wondered if the issue with K series pistons was with sustained use at high revs rather than quick overtaking bursts.

[gundersen]

Thank you for clearing that up Roger. I already have the uprated "trophy" pistons, and they should be good for the tune I am running. So the forged pistons are off my Christmas wishlist again

[Myles]

up to about 160bhp and anything above that would need forged.

 

There is - or rather was- a middle ground. I think Rover did a 'Trophy' engine or something - can't remember the designation, but the pistons were tougher than standard and are ok for higher revs and power (180ish and 7.5krpm). I've got them in my 183bhp 1.8 - bits supplied and assembled by Oily...

 

I understand they became quite sought after for certain race series where forged pistons were outlawed.

[Mankee]

Most Trophy/VVC 160 engines have these pistons in them. They have 160 engraved on the crown:

 

http://images20.fotki.com/v233/photos/8/42688/8879057/DSCF1261-vi.jpg