My Phantom BA XR6 Turbo Build

[tazzanz]

Sigh, Probably should have rephrased that, not the first I have heard of it, but the first I have heard of recommending 5500rpm as a rev limit!!

[k31th]

that's just the stock rev-limit and not the worst "safe-zone" to keep to.

[tazzanz]

*SIGH*

[k31th]

that's alright, you can make around 1000hp at the crank on a 5,500rpm limit, with the right setup...

[tazzanz]

Na will still be sending it at 8000rpm. Was just interested to hear peoples thoughts. Didn’t buy that billet crank for nothing!

[k31th]

well you're going to need strengthened valve guides etc at the top end, heaps of stronger bits for the rotating assembly (bearings, bolts etc) and (and probably more) even then it's risking it, bigtime... get a de-stroked setup if you want it to survive and make stupid power haha

[Puffwagon]

Have a read of this https://www.musclecardiy.com/performance/understanding-piston-speed-in-high-performance-engines/

 

I worked out the maximum safe piston speed for a 4 litre barra ages ago and it was about 5500 rpm iirc.

[skidxr6t]

I say build it strong and tune it properly and that's not a worry.

 

these motors don't like being revved high I do know this but on falcons everything else breaks before the engine

[tazzanz]

I see hoon tune has tuned a couple pushing 8500rpm on the stock crank. Crazy impressive.

[Puffwagon]

The main reason not to rev it high is the stress on the pistons, gudgeon pins, conrods and rod bolts as it stops to change direction at tdc or bdc. All of this moves a lot faster as it has a long stroke. If you make all of that strong, the stress moves to another part of the motor.

 

It is a fallacy to say that the engine runs out of torque at a set point, as for the most part this is dictated by everything else, ie: cams, turbo, head work etc etc, not the stroke or displacement.

 

You can rev a barra higher than 5500 obviously, but in a stock falcon it ain't necessary. In a 1500hp car with a built motor etc, it is necessary to raise the limit a bit.