Jezza's Turbo LJ
- Thread starter Jezza
- Start date
OP
I'm not revving high at all. My trans is programmed to shift at 5k. I think the hard cut is 5600. Those were the springs he sent with it. Comp 26125. The ones I got are 74813 which is actually a Lunati part made by Comp.
OP
I was readin through your thread for the third time and wanted to ask if you thought drive pressure caused your freeze plug failures. I build performance diesels everyday and we just take it as a given that the freeze plugs aren’t going to hold once you reach an established pressure. Lots of companies offer the aluminum “t bar”
Plugs for that very reason. We usually add an oil catch can about the same time. Just funny to me the similarities I guess. Now when you get finished with all of this gas burner foolishness, let me know. I’ll show you something decidedly more dirty.
Plugs for that very reason. We usually add an oil catch can about the same time. Just funny to me the similarities I guess. Now when you get finished with all of this gas burner foolishness, let me know. I’ll show you something decidedly more dirty.
OP
That thought did cross my mind, but I'm still breaking in the engine and am on wastegate (6 psi). I can't imagine I am getting that much coolant pressure at that low of boost. I had been seeing coolant leaking from that corner for a while. I think the plug just slowly walked out. I have had other failures with brass plugs in the past. After this I won't use them again. I stole the idea of the aluminum plugs from the diesel guys. So far it is leak free, and my confidence is slowly returning.
I'm having trouble imagining boost pressure causing coolant pressure to spike that much. Is that what happens? I was guessing it has more to do with high power levels causing the block to flex.
On diesels the cylinder pressure migrates past the head gasket into the coolant. Idk if its the same?
Drive pressure also pushes oil out of the egr and oil filler cap.
Dont you hate when that happens
My jeep magically finds itself on rocks somehow.......and then i gotta clean it after, So yall stay safe i know alot of you guys struggle from this
wow......i would have never known that
The more you know out of the blue by just reading
Having no previous knowledge of drive pressure until now, my mind went to the custom water pump impeller.
probably not enough pressure there to make the difference between a plug working or not.
Having zero experience with diesels, how does that work? The coolant pressure on a 4.0 is set by the pressure rating on the cap so I would think any excess would just push coolant into the reservoir.
It is the force of the exhaust gasses exerting against the turbine wheel in the turbocharger. As the exhaust gasses turn the turbine, the compressor wheel turns and compresses air that you read as boost... as this boost goes up, it is increasingly harder to turn the tubine and creates the back pressure or Drive Pressure. Now then, most of the time this is a nominal pressure, manageable and within the limits of things like freeze plugs. The problem is when it spikes. Stomping the gas and maxing out the boost, this will push past a head gasket, even lift a head. This compressed gas looking for an escape will do all sorts of weird things. Most of the time it focuses in areas around the head, instantly spiking. Popping a freeze plug with the spiking pressure before the fluid can transfer in the system and equalize. That make sense?
Now this doesn’t mean that the head gasket it bad, it just means that the pressure is exceeding the clamping force on the head bolts.
Now this doesn’t mean that the head gasket it bad, it just means that the pressure is exceeding the clamping force on the head bolts.
Is this a momentary thing that happens before the WG opens and/or something that happens if your WG isn’t operating correctly or set up properly for your build?
Cylinder pressure can exceed 3000psi on a diesel. It happens in pulses and can send pressure into the crankcase or coolant
Exactly.
I was trying to tone it down as I don’t know what a gas engine calls excessive pressure when running a turbo but the byproduct of that pressure is the same. Gas engines also don’t have nearly the amount of head bolts or clamping force on the head as a diesel engine does. In that I would expect to see the excessive drive pressures cause those issues we discussed earlier, sooner and with less pressure.
OP
I made myself a new fuel rail for the 4.7. -8 all the way through with ORB ends and machined threads. All one piece and extra thick. I also made a few for some friends.
