How does timing affect head gaskets?

The more advanced the timing, the harder on the head gaskets?

Is it that simple?

 

Begle,

Advancing the timing causes changes in cylinder pressures. Depending on the drive pressure of the turbo these changes can cause instant failure of the headgasket. Not a bad idea to have a second boost gauge in the exhaust manifold to monitor such pressures if you are concerned.

 

i've read and read and am asking myself some questions on this topic.... on a boost gauge for the exhaust manifold.... do i need copper line instead of the nylon so it dosen't melt? and just any gauge will work? what is a good pressure for that? i've heard that my HTT is suspose to be in the 1:1 ratio.... so in theory i should have 50# on both sides? also i've heard mixed reviews on retorque on stock bolts.... my machinest said re-tq them and not worry..... others have said it'll break off..... waht if i replaced the old bolts with new ones and tq'd them at a higher poundage? would that work? replacing them one at a time? just some questions i've been meaning to ask..... sorry if i hijacked this one....

 

In laymen's terms yes.
The more you advance it the higher the cyl pressure.
As mentioned though you can inadvertently increase timing by running to high of turbine inlet pressure. This is probably the most common cause of HG failure and most blame the high boost # but its the timing generated from the TIP being to high.

 

A easy way is to just pull the pyro and thread in a fitting there. Yes you want to run a few feet of copper to dissipate the heat. I use all copper and just run the gauge thru the drivers side window into the cab. You only need to check TIP after making fueling or cooling mods as it shouldn't change unless you have made mods. Yes 1:1 is equal boost and TIP pressures. If you don't have o-rings I don't see the need to do a re-torque. The stock bolts need to be measured for stretch prior to reinstalling them and I would not recommend you pull them harder than the factory recommendations.

 

How can increased boost levels result in advanced timing?

Increased exhaust back-pressure increases the pressure on the pistons because they need to push harder to get to TDC... High boost doesn't cause the fuel to burn any farther before TDC, does it?

Maybe a tad since high boost would result in high cylinder temperatures, but I thought that the fuel is always injected at high enough temp's for auto-ignition.

Would a couple feet of copper tubing be enough to dissipate 1600 degrees?

 

The key is heat. Combustion = expansion, earlier injection allows for more expansion time witch in turn = higher cyl pressure. If you run a higher TIP than boost # you are not completely evacuating the cyl every stroke and leaving some spent HOT gas in the cyl witch in turn causes the next charge to combust a little sooner. Each consecutive stroke will compound this timing advance until either the HG or the turbo pops if pushed.
Your pyro temps are a good indication of whats happening in the cyls.
Actually the boost # on its own is irrelevant in the equation.
Whats important is the boost in relation to your TIP.
Many turbos like the magic 1-1 ratio so if your turbo(s) happy ratio is 1-1 @ 60 psi than 60 psi is relatively safe. However if its 1-1 @ 25psi (like the stock hx35) and you run up to say 35psi boost your turbine inlet pressure could be 45+psi.

 

Lots of good info here guys. I would like to add one more note on an exhaust backpressure gauge set-up. Use about 10ft of copper line and coil it to make about a 2" coil. This allows heat disipation so you can run a nylon line to the boost gauge with no adverse affects. Merchant Automotive, who is a diesel specialist in Michigan, has done a few installs this way. He just built the first 1000hp DMax and has contributed greatly to the diesel and DMax community. Just throwin that out there so that everyone knows that an industry expert has proven the method.

 

Diesel has an autoignition temperature of 494 degrees.
Higher boost pressures, and a high inlet-to-exhaust pressure ratio, will result in higher cylinder temperatures.

But even with no boost, the combustion chamber is still above 494 degrees when the fuel is injected, right? Will temperatures above 494 degrees cause the fuel to burn even faster?