Lancia Integrale crankshaft strokes and rod ratios
Posted: February 13th, 2007, 10:00 pm
Guy,
Recently I've been looking at some of the eight weight cranks that are available for the turbo engine and would like your opinion please.
Three strokes are available 86mm, 90mm and 96mm all requiring different lengths of rod. As I calculate rod ratios (roughly) they will be 1.73, 1.61 and 1.46. Nothing too accurate and not allowing for compression height change which is another question I have for another day.
Having scoured the WWW and read what books I have, I have taken a liking for the 86mm, this requires obviously the longest rod. My understanding (clouded by many opinions and info overload) is I'll benefit in the higher engine range (at the expense of lower) with a safer high rpm with benefits such as lower piston velocity and reduced friction due to a reduced rod angle. Better combustion, higher cylinder pressure and increased chamber temperature and syptoms bandied about. My concerns are for the reduced capacity, increased potential for detonation and harming the VE. What if any of this rings true? What else am I missing? Possibly I'm just WRONG thinking this for a turbo engine!?
The shorter stroke as I understand improves torque in the low range with a delayed maximum cylinder pressure (less prone to detonation) I'm concerned for total cylinder pressure and reduced combustion as well as harming the ability to rev. What if any of this rings true? Maybe this is the route for a turbo engine?
Maybe, if only for my sanity, leave well alone and stick to the 90mm stroke.
I realise that its a long way down the list of priority when it comes to a race engine and jobs to do but I don't want to miss a trick or leave a stone unturned. Even if it means living on meagre rations for a while longer :-)
Thanks
Nik
Recently I've been looking at some of the eight weight cranks that are available for the turbo engine and would like your opinion please.
Three strokes are available 86mm, 90mm and 96mm all requiring different lengths of rod. As I calculate rod ratios (roughly) they will be 1.73, 1.61 and 1.46. Nothing too accurate and not allowing for compression height change which is another question I have for another day.
Having scoured the WWW and read what books I have, I have taken a liking for the 86mm, this requires obviously the longest rod. My understanding (clouded by many opinions and info overload) is I'll benefit in the higher engine range (at the expense of lower) with a safer high rpm with benefits such as lower piston velocity and reduced friction due to a reduced rod angle. Better combustion, higher cylinder pressure and increased chamber temperature and syptoms bandied about. My concerns are for the reduced capacity, increased potential for detonation and harming the VE. What if any of this rings true? What else am I missing? Possibly I'm just WRONG thinking this for a turbo engine!?
The shorter stroke as I understand improves torque in the low range with a delayed maximum cylinder pressure (less prone to detonation) I'm concerned for total cylinder pressure and reduced combustion as well as harming the ability to rev. What if any of this rings true? Maybe this is the route for a turbo engine?
Maybe, if only for my sanity, leave well alone and stick to the 90mm stroke.
I realise that its a long way down the list of priority when it comes to a race engine and jobs to do but I don't want to miss a trick or leave a stone unturned. Even if it means living on meagre rations for a while longer :-)
Thanks
Nik