exhaust back pressure

gambling209 · Jan 28, 2016

what is the max I should run? it is a job2 truck with no studs, stock fuel and turbo. make sure if it is absolute pressure that you let me know. will be monitoring with a dashdaq. does it do both gauge and absolute pressure? looking to run my own tests to see if I need a waste gate.

6fodays · Jan 28, 2016

Honestly drive pressure should be as close to 1:1 to boost as possible but ive always been told +/- 15 is okay? And are you running a single turbo?

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gambling209 · Jan 28, 2016

no stock as a rock except for the normal bolt on stuff. I've noticed that some tunes really get boost up there.

powerstroked08 · Jan 28, 2016

Valve springs are only 75 pounds. So you want to keep the ebp lower than that.

ckrueg · Jan 28, 2016

From what I have read about 80 absolute is really the max you would want to see. Around that and higher you risk floating valves. On h&s street tune I see about 75 absolute

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6fodays · Jan 28, 2016

So i assume you have an egr ******? The stock turbos use the egr system as sort of a back pressure relief (something to that extent) but i dont think youd need a wastegate. Studs are a good idea though. Id just closely monitor boost and ebp and go from there.

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gambling209 · Jan 28, 2016

have the egr stuff. just have not put it on. spring time i'll take care of it. have read the egr relief thing before, but some people don't agree. so I figured I would just watch it and see what it does. ******* tunes keeps the egr shut all the time on the tunes I run. so don't know if that matters or not. would love to have engine studded, but can't justify the cost right now to do it. so trying to avoid having to add them. a waste gate can be a cheap insurance policy. also have read stock turbo and fuel doesn't need a waste gate. just looking to see for myself.

6fodays · Jan 28, 2016

gambling209 said:
have the egr stuff. just have not put it on. spring time i'll take care of it. have read the egr relief thing before, but some people don't agree. so I figured I would just watch it and see what it does. ******* tunes keeps the egr shut all the time on the tunes I run. so don't know if that matters or not. would love to have engine studded, but can't justify the cost right now to do it. so trying to avoid having to add them. a waste gate can be a cheap insurance policy. also have read stock turbo and fuel doesn't need a waste gate. just looking to see for myself.

You can do studs one at a time. All you have to buy is studs. Not a terrible job at all.

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sootie · Jan 28, 2016

The factory sensor stops reading around 73psi so I bet you are climbing a ways past that.

On a stock tune, the Egr opens at wot, letting some drive pressure relieve thru the Egr cooler. Nothing to agree or disagree about.

drunk on diesel · Jan 28, 2016

you don't need a wastegate... let that sumbitch eat!

I've run as big a tune as I can on every 6.4 I've owned. I've never paid a lick of attention to EBP. I watched buddies beat the tar out of them on big tunes, and I'm not near as hard on them as they are.

I've got two of them in the driveway right now running 2.2-2.4us duration. I've been actively tuning both of them lately, so they've been getting plenty of WOT runs. My old service truck had 200k on it when I sold it. Same tunes on it. Stock fuel and turbos.

Oh, and untouched EGR on every one of them. I see exponentially more issues with EGR ******s than I do with actual EGR components! LOL water leaks, exhaust leaks, frozen EBP tubes, etc. I've never had a single EGR related problem.

And... I don't know if it holds true on 6.4's, but on the 6.7 Dodges, I saw a TON more blown head gaskets on trucks with EGR ******d vs. not. Does the EGR path act as a pressure buffer chamber to lessen EBP spikes?

Or are guys who "gotta rip all that stock junk off so I can have water leaks and crank case vapors puffing under muh daily driver" just harder on their trucks?

I tuned a buddy's 6.4 with just an absolute dirty nasty tune. He's hard on trucks and is balls to the wall with them. The truck was lifted on 37's with 3.55 gears, and it would hit 60psi boost on stock fuel and turbos. I'm sure EBP was 100+

I talked him into trading it in on a 6.7 once it hit about 180k miles because *I* was concerned that it was going to let go on him! LOL

But that's the kind of abuse I've seen these trucks take. Run whatever tune you want because there's no magical EBP limit that's going to prevent damage. If something's going to happen, it's going to happen IMO. Might as well enjoy the truck!

drunk on diesel · Jan 28, 2016

oh, and anybody who 1-4-1's studs on a 6.4 needs his head examined...

and he'll probably have plenty of time to examine his heads when the gaskets let go.

the seal is far better on the OEM bolt torque job vs. unloading them and studding.

I'll roll the dice on a 141 job on a Cummins with 6 bolts per cylinder and a much easier head R&R. But on a 6.0 or 6.4? I've never seen it work out, personally...

gambling209 · Jan 29, 2016

well I usually run a tune that cycles the egr in the winter to lesson the freeze up of the sensor issue. well this year the egr won't cycle anymore. it only cycles at idle anyway on my tunes. thats what is speeding my lazy tail up to replace it all. I think you are right that a working egr probably help lesson the blown parts thing. but I'm not keeping the egr stuff. already have a $300 piece bad. as far as replacing studs one at a time. I'm sure some guys get by with it, but don't let my long on name fool you, I'm not a gambling man. thanks for the responses.

6fodays · Jan 29, 2016

drunk on diesel said:
oh, and anybody who 1-4-1's studs on a 6.4 needs his head examined...

and he'll probably have plenty of time to examine his heads when the gaskets let go.

the seal is far better on the OEM bolt torque job vs. unloading them and studding.

I'll roll the dice on a 141 job on a Cummins with 6 bolts per cylinder and a much easier head R&R. But on a 6.0 or 6.4? I've never seen it work out, personally...

You are correct. It is sort of a rolling the dice move. But ive only heard of one person have a blown head gasket after going one by one. If you start from the inside out and torque as they are supposed to be there really isnt a way to effect the seal from the head gasket unless it is already damaged.

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drunk on diesel · Jan 29, 2016

I hear ya. follow the sequence and such. I just wouldn't take the gamble, personally.

OP, I have no problem with removing parts if they're giving you a headache. Enjoy the truck and don't get too hung up on EBP numbers.

footlong70 · Jan 29, 2016

Studs one at a time is very reliable if done right. Oem bolt torque/initial seal means squat when you double/triple the clamping force with studs, further crushing the gasket. Head gaskets can even be reused if you read some of the old mechanic books, as long as more clamping force(higher bolt torque value) is used and no damage to the gasket. Head gasket technology for the most part hasn't really changed much. However nobody in their right mind does the major job of pulling the heads (magnaflux/machining/cleaning/ect)and takes the chance of putting a used gasket back on that might be compromised even a little during the head job anymore. Doing the studs one at a time I don't consider a major job. IMO, if the gaskets are not already compromised, the gaskets are the most updated oem, the clamping force of MORE than ONE bolt/stud doesn't go below original clamping force, and the sequence is utilized than I firmly believe you're in the clear.
With oem updated head gaskets being able to handle +1000hp with enough crush force over oem clamping force, I don't see the issue. The biggest concern though is not trying to band-aid head gaskets that puked before.
Ive run mine zero issues for a little over a year. A lot of heavy mountain towing, racing, 60 PSI boost, ect. Very happy with it.

drunk on diesel · Jan 29, 2016

I've never had a problem with stock bolts on stock fuel and air.

If I'm throwing the sink at it, I'm pulling it down to put pistons in it anyhow, so it's a moot point.

ckrueg · Jan 29, 2016

sootie said:
The factory sensor stops reading around 73psi so I bet you are climbing a ways past that.

On a stock tune, the Egr opens at wot, letting some drive pressure relieve thru the Egr cooler. Nothing to agree or disagree about.

I was speaking absolute pressure. So 73+14.5 is the max it will read.

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UpstateDieselGuy · Jan 30, 2016

drunk on diesel said:
you don't need a wastegate... let that sumbitch eat!

I've run as big a tune as I can on every 6.4 I've owned. I've never paid a lick of attention to EBP. I watched buddies beat the tar out of them on big tunes, and I'm not near as hard on them as they are.

I've got two of them in the driveway right now running 2.2-2.4us duration. I've been actively tuning both of them lately, so they've been getting plenty of WOT runs. My old service truck had 200k on it when I sold it. Same tunes on it. Stock fuel and turbos.

Oh, and untouched EGR on every one of them. I see exponentially more issues with EGR ******s than I do with actual EGR components! LOL water leaks, exhaust leaks, frozen EBP tubes, etc. I've never had a single EGR related problem.

And... I don't know if it holds true on 6.4's, but on the 6.7 Dodges, I saw a TON more blown head gaskets on trucks with EGR ******d vs. not. Does the EGR path act as a pressure buffer chamber to lessen EBP spikes? Or are guys who "gotta rip all that stock junk off so I can have water leaks and crank case vapors puffing under muh daily driver" just harder on their trucks?

I tuned a buddy's 6.4 with just an absolute dirty nasty tune. He's hard on trucks and is balls to the wall with them. The truck was lifted on 37's with 3.55 gears, and it would hit 60psi boost on stock fuel and turbos. I'm sure EBP was 100+

I talked him into trading it in on a 6.7 once it hit about 180k miles because *I* was concerned that it was going to let go on him! LOL

But that's the kind of abuse I've seen these trucks take. Run whatever tune you want because there's no magical EBP limit that's going to prevent damage. If something's going to happen, it's going to happen IMO. Might as well enjoy the truck!

Funny you mention everything staying intact. I ran my old '04 with everything stock other than an exhaust and street tune. It had the gaskets replaced with studs under warranty as it was having issues. Gaskets weren't good once the heads were off. After that, I ran a race tune with all the egr in place and never had another issue.

Fast forward to my '15, I ran that with a race tune and pipe for several thousand miles without an issue. In fact, I never touched anything under the hood!

I believe that in stock form, these new diesels with the EGR use the valve as a means to help regulate exhaust back pressure. The issue with the 6.0 was the cooler was inadequate and allowed the coolant to get too hot. I don't think the 6.4 had as much of an issue.

drunk on diesel · Jan 30, 2016

I haven't heard of a ruptured 6.7 cooler, but I've seen a few ruptured horizontal coolers on 6.4's.

But I've never seen one rupture after stopping the flow through it. I'm not saying it can't happen. I'm saying I've never seen it, and have zero fear of it occurring.

But I'm obstinate... I'll do the opposite of popular opinion just to test the theory against my own logic. I've spent money after my theory fell apart in the face of popular opinion.

But my experience with diesel performance forums has usually proven to side with my logic and gut instincts. Going as far back as the late 90's when you weren't supposed to modify 12v fuel plates because they were "special hardened steel"

I'm not saying I was the first to do it, but I was the first dumb kid on TDR who did it in the face of everybody saying not to. Within 5yrs, the "welcome to your 12v" intro threads all said "grind your plate, don't waste your money on an aftermarket one"

I digress... often!