bigger turbo

[ADU_S2]

hi every 1

A stock RS2 with a good exhaust can go up to 370HP and around 600-620Nm, peak HP is around 6000 RPM and peak torque around 3500 RPM.

so if you upgrade a stock rs2 engine with a bigger turbo preferably a garett turbo what kind of power can i expect and how much torque would it produce?

If torque remains at 600-620Nm is it ok to presume the engine bottom end ie rods will be able to handle the power as the torque is the same?

thanks

[caterpillar]

the engine bottom will NOT handle the torque.....the rod will bend or broke,and they have to came out of the block......the org rod will NOT stand more than 70-80hp pr rod. stenparnermotor in motala in sweden have h-profilsrods will stand 200hp pr rod.and he is not ekspensive.

[ADU_S2]

I was under the impression that its the torque which would bend the rods not the hp. so if torque remaiins the same and hp increases why would the rods bend

[porkkis]

Same max torque, more max hp -> bigger turbo -> more upper rpm hp -> more rpm -> more stress.

[Pisobiker]

I was under the impression that its the torque which would bend the rods not the hp. so if torque remaiins the same and hp increases why would the rods bend

Exceeded max torque limit will bend rods (combustion forces) while conrod will crack and break under two circumstances:

1) Inertial loads (which increase with the square of the speed, and are maximum @ TDC on the intake stroke), which mean having exceeded max rpm limit;
2) Fatigue, which is the combination of alternating forces (pushing+pulling) and the frequency of it.


So, from a practical point of view, if X is max safe torque the conrod can withstand, it doesn't matter if it's applyed @ 1000 or 9000 rpm.

Not only! There is another interesting aspect on increasing torque at high rpm:
while increasing rpm, inertial loads increase, among which the strongest is an EXTENDING FORCE over the conrod. Combustion force, instead, represents a COMPRESSING FORCE for the conrod, therefore, during power stroke, inertial loads are actually lowered by the combustion force.
At high rpm (where inertial loads often, even in forced induction engines, exceed in absolute value combustion force), the higher the torque the lower the resultant of the two forces, meaning, at same rpm, you are actually lowering peak load and fatigue stress......


Something to take into consideration, when running near max conrod load reasistance, is that load which actually harms is peak pressure in the combuston chamber, no matter for how long it is reached.
This means that any small pinging problem, which increase quite consistently pressures, might be the cause of bending the rods.

So someone might ask: if when pinging pressures increase a lot compared to "non pinging" conditions, how come when engine pinges output actually drops considerably?
Answer: Torque is the resultant of the AVERAGE force over the piston in the entire power storke. When pinging, pressures increase dramatically for only very short periods of time, while dropping down in the other part of the power stroke, so that AVERAGE force is reduced.


Try this thread for further comments over this topic:

http://www.s2forum.com/forum/showthread.php?t=322&highlight=conrods+stress

Even though it seems OEM conrods can take up to 600Nm, for practical purposes and road use I personally won't run more than 550Nm peak (which is my actual output).



Marco

[sorens2]

Hi

Max pressure on conrods is @ max torque. So U can increase the HP without any problems. As long as torque is the same. I would also say 550 Nm max on standard conrods.

Søren S2