Crossflow Kent - what RPM for a shift light

[twobone]

Hi,

I have a Stack Clubman tach and just bought a shift light.

For a stock SuperSprint Crossflow Kent, what is a "safe" redline that balances longevity but still provides a kick in the pants?

I'm looking forward to worrying less about keeping my eye on the tach while driving.


Thanks and happy motoring

[Eric Mc]

My manual says do not exceed 5,500 too often.
Who needs a shift light?

[Aeroscreens]

My modified x/flow (forged pistons etc) happily revved to 7,200, but I set the shift light at 7,000. The fact that it went 'bang' after 53,000 miles of hard use is another story......

I reckon that a standard 1700 supersprint would be in the region 5,500-6,000 revs. Hopefully someone else will be along to confirm or deny. The standard pistons are not known for their longevity if the car is driven 'properly'

[davidball]

I would not take my 1700 Supersprint above 6000 rpm.

[elan_fan]

6000 all day long and 6500 in the gears. No ford iron crank and rods from the xflow in the 1.6 and above capacity (77mm stroke) are safe over 7000. As for pistons the ford items have too much meat above the gudgeon and a split skirt. Go get some twincam pistons and have the crown machined down to form the combustion chamber.

[twobone]

OK

I will set it at 5,500 for the road and then up it to 6,000 for any track time.

When you step on it in a Caterham the sensory overload level is very high. I'm looking forward to the little red light reminder to lift or shift.

[Eric Mc]

Caterhams are all about feel and sensing. You don't really need mechanical aids to tell you what to do - you will just know when it is right.

[downsman]

I had a crossflow built with standard crank and about 140bhp. I set the redline to 6000rpm, but when the engine builder saw that he said that I wouldn't get the best out of it without taking it to 6500. It was fine for 4 years using that limit.

Duncan

[Noger]

Useful if you let anyone else drive your 7. M

y "mate" thought my crossflow would go to 8000rpm because that is what the dial went to !

Actually, it DOES go to 8000rpm it seems

[twobone]

Duncan, what happened after 4 years? Did it go BOOM?

[Sam_68]

elan_fan said:

6000 all day long and 6500 in the gears. No ford iron crank and rods from the xflow in the 1.6 and above capacity (77mm stroke) are safe over 7000. As for pistons the ford items have too much meat above the gudgeon and a split skirt. Go get some twincam pistons and have the crown machined down to form the combustion chamber.

The Crossflow in my Sylva is still on a cast iron crank, albeit tuftrided and everything lightened and balanced with Twin Cam pistons.

The Rev limiter is set at 7,800rpm and engine still seems happy enough after 16 years in my ownership.

For a Super Sprint engine, I'd stick to 6,5000 rpm for the rev limiter, though (maybe 6,750 if you feel brave) and at least 250rpm less for the shift light.

As Duncan said, a tuned Crossflow won't give anything like peak power unless you rev it to at least 6,500.

[elan_fan]

Sam_68 said:

The Crossflow in my Sylva is still on a cast iron crank, albeit tuftrided and everything lightened and balanced with Twin Cam pistons.


The Rev limiter is set at 7,800rpm and engine still seems happy enough after 16 years in my ownership.

So basically the OP will be safe above 7000 as long as his engine is a different spec

Sam_68 said:

For a Super Sprint engine, I'd stick to 6,5000 rpm for the rev limiter, though (maybe 6,750 if you feel brave) and at least 250rpm less for the shift light.

As Duncan said, a tuned Crossflow won't give anything like peak power unless you rev it to at least 6,500.

As I Said 6000 all day long and 6500 in the gears. Keep up at the back

[Sam_68]

elan_fan said:

So basically the OP will be safe above 7000 as long as his engine is a different spec

My apologies. I'll narrow it down to as few words as possible for the hard-of-thinking:

elan_fan said:

No ford iron crank and rods from the xflow in the 1.6 and above capacity are safe over 7000.

to which I said:

The Crossflow in my Sylva is a cast iron crank. The Rev limiter is set at 7,800rpm and the engine still seems happy enough after 16 years in my ownership.

Have we got that?

Oh... and if you spend all day at 6,00rpm, you either need a taller final drive ratio, or you need to get someone to explain what a gearbox does.

Edited by Sam_68 on Saturday 16th April 09:33

[elan_fan]

Good comeback Sam, at the risk of this turning into the usual tt fest when you get involved - my reply:

You have twincam pistons which are a totally different design to OP's and are much lighter and a better design than xflow pistons.

You have Tuftrided your crank. The OP's is the standard item.

6000 rpm all day refers to the rpm at which you would never get a failure but you know that and are just baiting me which I have fallen for.

well done on not getting a failure on you Sylva. You are obviously doing something different to me, and when I build my next Twincam maybe you could give me some pointers

[twobone]

Really enjoying the recently installed shift light. Now I drive around looking for an opportunity to turn on the light.