XLR8R
Crew Chief
- Joined
- Sep 10, 2007
- Messages
- 2,364
If dp is only 70 psi how does it effect hg failure if cylinder pressure is over 1000psi?
Simple - it doesn't.
I dont think drive pressure in most cases is a major player in head gasket failure... it's more about peak cylinder pressure, is it not?
TIP can reflect combustion pressure like EGT indicates cylinder temp... neither is necessarily an accurate measurement of the critical numbers.
No HG ever failed from blowdown pressure in the exhaust tract.
This where I was trying to get to with my original post. Would it be the duration of the event? i.e. a "peak" of 1000psi vs a continuous 70psi? Also with a lopsided ratio, at what point (if ever) would one have to worry about reversion?
Duration of the pressure is insignificant when it's an order or two of magnitude less than peak combustion pressure.
Reversion is always an issue that must be considered - small turbines & tight exhaust A/Rs require less overlap & higher LSAs in the cam profile to avoid diluting the fresh intake charge with excessive combustion byproducts... hence the 600 series' "in-cylinder" EGR, courtesy of the OEM bumpstick's tight LSA.