Vauxhall Owners Forum banner

1 - 20 of 35 Posts

·
Registered
Joined
·
3,438 Posts
Discussion Starter #1
What power can the standard LET con-rod cope with using ARP bolts?

Craig
 

·
Registered
Joined
·
8,331 Posts
It's not only the lb-ft
It's also the max revs the engine will experience. Raising the rev limit (as many chips allow) may prove to be a double-edge sword.
After 6.5K rpm the risk of rodbolt failure rises sharply:beer:
 

·
Registered
Joined
·
3,438 Posts
Discussion Starter #6
RPM

Have had 7000rpm on the LET a few times now with no problems!
Whats the torque figure of phase 4 or V-MAX evo 6 kit?When running properly!!!!!!!!!
Or is it better to run phase 3.5 with NOS?

craig
 

·
Registered
Joined
·
13,676 Posts
speaking to steve at SBD yesturday, and he was saying that std rods in an XE are rev safe to 8500rpm, but the bolts are not, thats whay he suggests fitting ARP's, but he said you can rev then that high on a turbo too, but the thing that causes them to break is the torque, its the downward force of the torque that kills the rods as they are put under too much stress
 

·
Registered
Joined
·
34,309 Posts
Revs kill con rods a lot more than people give them credit for, often the failure actually occurs on after the exhaust stroke when there is no pressure above the piston and the rod/bolts have to take all the strain of reversing the direction of the piston, its this stretching that kills rod bolts in particular, the bolts arent acutally under any extra strain at all from more torque.


Chip
 

·
Registered
Joined
·
8,331 Posts
Re: RPM

GSImad said:
Have had 7000rpm on the LET a few times now with no problems!
Haven't we all? lmao
The rod bolts won't shatter the moment you hit 7K.
The *risk* of failure rises sharply though. So the risk of failure at 3000rpm is higher than at 2000rpm, but that difference is nothing compared to 8K vs 7K rpm.

If you're also producing high torque at top revs, that compounds the situation, so where an XE can rev happily (ish) at 7K a turbo doing 2bar boost might kick the bucket at the same revs.:beer:
 

·
Registered
Joined
·
34,309 Posts
torque doesnt effect rod bolts, only rods, revs effects both.

This is because the revs hurt things due to the tension, which both the rods and the bolts have to deal with, where as torque only increases the load under compression which doesnt effect the rod boltss at all as all this pressure is transmitted from the rod to the bearing to the crank without the involvement of the bolts.

So if you are only increasing torque and not revs you dont need to worry about the rod bolts really, although personally i always fit them anyway just because i dont trust the standard ones.


Chip
 

·
Banned
Joined
·
12,030 Posts
JohnA said:
340 ftlb at 6.5Krpm is getting close to 500bhp Rob:D

Is this an indication of what you've got in store?;) :beer:
I have been told as a matter of fact that the rods do break (not the rod bolts if ARP's fitted) with torque in this sort of range with standard rods!

John we shall wait and see:p
 

·
Registered
Joined
·
8,331 Posts
You probably already know this, but you can DIY strengthen the stock rods by polishing them (yes folks, very shiny polishing reduces the appearance of wrinkles..eeeerrr.... hairline cracks I meant)

Or even better you could have them shot-pinned, then polished.:beer:
 

·
Registered
Joined
·
9,240 Posts
hi

its at this point i start wishing i had not dropped out of robs group buy on the rods.....

approx 300bhp on phase 3.5 + 125bhp of n20 over this weekend and its still in one piece...

i think ill most probably be able to tell you exactly how much power the standard rods are capable of within a few weeks eh!

regards, brian
 

·
Registered
Joined
·
34,309 Posts
300bhp from phase 3.5 + 125bhp from ntirous should equal 475bhp or so if your ignition is up to it (which i believe it is as i know the spec of it all)

So i guess the standard ones are at the very least good for 475bhp for a short period of time!


Chip
 
1 - 20 of 35 Posts
Top