Back Pressure Data

Gwoody

Gwoody

Switchblade Turbos
Joined
Jun 19, 2007
Messages
414
I have some data on back pressure to share, this is from an 06 Dodge that we ran some data logs on. This is a stock manifold and turbo, the drive pressure is double the boost in the higher boost ranges. The data is in the attachment.
 

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  • 8 23 #3 Smarty 3 Stock turbo 06 Dodge.LOG.zip
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Why can't you attach it as a graph? :)





Series1 is drive, Series2 is boost.
 

Attachments

  • boost drive.JPG
    boost drive.JPG
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I was pretty tickled I even figured out how to get it on here as an attachment. However, if someone wanted to convert it to graph, that would be good...................
 
So if I understand this correctly, a stock truck seeing 35# of intake/manifold pressure with 70# backpressure, the head gasket is actually holding 70# boost?
 
PSUCE said:
So if I understand this correctly, a stock truck seeing 35# of intake/manifold pressure with 70# backpressure, the head gasket is actually holding 70# boost?
Click to expand...

no, it's holding 70psi of drive pressure...

it takes the 35psi of boost and compresses it 17.5 times which = 612.5psi... then when you inject fuel, the cylinder pressure skyrockets far higher still!!!!

70psi is nothing
 
PSUCE said:
So if I understand this correctly, a stock truck seeing 35# of intake/manifold pressure with 70# backpressure, the head gasket is actually holding 70# boost?
Click to expand...

Yeah, those mult layer gaskets are good!!!!!!!! I have retorqued the factory bolts to 125. This was with tthe smarty on 3.
 
Forrest Nearing said:
70psi of drive is NOT 70psi of boost... 70psi of boost compressed 17.5 times is 1225psi!!!
Click to expand...

I agree Forrest, cylinder presuure increases as boost does, point taken.
I was pointing out that the CR gaskets are pretty d.... tough.
 
I suspected the drive pressure was a little high but I was really suprised at it being about double the boost once we hooked everything up to gather the data.
 
Forrest Nearing said:
no, it's holding 70psi of drive pressure...

it takes the 35psi of boost and compresses it 17.5 times which = 612.5psi... then when you inject fuel, the cylinder pressure skyrockets far higher still!!!!

70psi is nothing
Click to expand...

Sorry, meant to say drive pressure. :bang Still wasn't thinking right as you pointed out in your previous posts about the compressing of the boost.

Has anyone played around with this on the other generations? Just interested stock how they would all compare. I realize that as they depart from stock they are all different, but just wondering.
 
Gwoody said:
I have some data on back pressure to share, this is from an 06 Dodge that we ran some data logs on. This is a stock manifold and turbo, the drive pressure is double the boost in the higher boost ranges. The data is in the attachment.
Click to expand...

It wont do that for long, your at a 2:1+ ratio now. you need a bigger turbo or you need to gate the turbo down about half the boost your seeing now.
 
If dp is only 70 psi how does it effect hg failure if cylinder pressure is over 1000psi?

i love hearing opinions on this subject
 
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?
 
OrangeNV said:
If dp is only 70 psi how does it effect hg failure if cylinder pressure is over 1000psi?

i love hearing opinions on this subject
Click to expand...

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?
 
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