Drive pressure Gauge

[Killerbee]

I am not familiar with the types of gauges available. The hot side will get well over 500 degrees, so tubing has to be used carefully.

A magnehelic uses simple static pressure ports. If the is a gauge that can display the boost as compared to the inlet side (vs one that is vented to the atmopsphere) then the actual numbers would surprise. I believe that there is a 38-40 psi differential, for 30 psi of plenum boost, the other 8-10 psi going to plumbing losses. That is a design nightmare if you ask me. But then again, it somewhat explains the LLY (stock) performance handicap.

40 psi is a PR of (40+14)/14=3.86

If you look back at the compressor map on the other thread, that is freakish efficiency and overspeed. Translated, beaucoup heat.

Edit: clarifying, a boost gauge normally shows pressure compared to ambient. Get one that is a differntial, IOW the high pressure side is compared to the inlet pressure, as opposed to simply venting it to the atmopsphere.

 

[LarryJewell]

This is the 3rd time to re-do my drive pressure plumbing, hopefully this cures the leak. The first one was using plastic hose, the same as with a normal boost gauge. The second was with copper tubing, this time a good friend sent me a braided hose. Bet this works finally.

 

[sweetdiesel]

That is a mighty nice hose Larry

 

[LarryJewell]

That is a mighty nice hose Larry

I think if I had used that hose from the Manifold all the way up to the sensor, I would have saved a lot of aggravation.

 

[MAXLLY]

Solid info Larry.

Thanks Sounds like braided line with a loop is the way to go.

BTW- Thanks for all the funny emails!!

 

[LarryJewell]

I now think I have an exhaust leak at the manifold, I'll check it out this weekend. The sputter at WOT hasnt gone away though and it is difinitely on the driver side.

 

[LarryJewell]

I now think I have an exhaust leak at the manifold, I'll check it out this weekend. The sputter at WOT hasnt gone away though and it is difinitely on the driver side.

Gasket to driverside uppipe at the turbo connection was leaking.

 

[LarryJewell]

new home for my drive pressure gauge

This is my new gauge mount "freshly painted" for my drive pressure gauge and 2 boost gauges

 

[kodiak]

So, when are we going to see if the Cheetah lowers your backpressure??? I am curious to see if this eliminates the problems with the LLY overheating.

 

[LarryJewell]

So, when are we going to see if the Cheetah lowers your backpressure??? I am curious to see if this eliminates the problems with the LLY overheating.

It does lower the back pressure based on how you setup the vane tables, I cant run the normal vane tables as they send drive pressure up as high as 2-1 or 3-1 ratio's compared to boost pressure.

 

[sweetdiesel]

This is my new gauge mount "freshly painted" for my drive pressure gauge and 2 boost gauges

Looks Good Larry,I hope you prefit the dash before painting it

 

[sweetdiesel]

So, when are we going to see if the Cheetah lowers your backpressure??? I am curious to see if this eliminates the problems with the LLY overheating.

OT ,But why is it that some LLY overheat and others dont?


As for a VVT turbo a stock turbo,stock tune with be close to 3:1 at certain points

and for the most part it is 2:1 on a stock turbo stock tune


Max Vane posistion is a huge player in how the VVT reacts,it is the single most important table on boost IMO

 

[LarryJewell]

Max Vane posistion is a huge player in how the VVT reacts,it is the single most important table on boost IMO

:exactly:

 

[Killerbee]

Back pressure, or drive pressure, is a product of many things. If the turbo is easier to drive, and allows a lower PR to effect the same boost, drive pressure decreases. But drive pressure is not a root cause of overheating IMO.

Compression heat is. Additional compression (work) will generally yield additional drive pressure, ...one shaft afterall. A different turbo may create less of this, but it may well be the systemic change in PR and efficiency that reduces that heat generation. Much of that can come from plumbing on both sides of the compressor, but particularly the inlet side.

Excessive drive pressure, is as much a symptom of improper induction design, as a hot tranny is a byproduct symptom of an O.H.

FWIW, and IMO, increasing max vane position allowance will create more boost and more compression heat. Reducing boost slightly will alleviate OH tendency. The disparity between OH tendencies among different LLY vehicles, may well come down to the allowance in disparity among MAP sensors.

 

[kodiak]

I did lower the boost pressure for towing up the same mountains that I overheated on last summer. Results were, no OH problems but I also could not maintain the speed that I could before. With that in mind....I was thinking that a more efficient turbo might allow me to increase the boost, add a touch more fuel, and be able to hold a decent speed...all without increasing my water temps.

I don't think the intake on my truck is near as bad as whats on the smaller ones.

 

[McRat]

OT ,But why is it that some LLY overheat and others dont?


...

Tell you what, when we drove Blue (04.5 LLY) towing Casper up through Vail last summer, for the first time I considered Blue an overheater.

The thin air made the charger work harder, and made the radiators less effective. Even the transmission overheated. Downhill!

 

[McRat]

One more time, Casper has a drive pressure sensor attached again. Hopefully I can get some valuable data this time.

Have:

Boost pre-CAC, boost post-CAC, EGT, Drive Pressure all set up to log externally with EFILive. In theory.

 

[Killerbee]

Along with IAT, that will be an interesting log on a tow trip.

 

[LarryJewell]

One more time, Casper has a drive pressure sensor attached again. Hopefully I can get some valuable data this time.

Have:

Boost pre-CAC, boost post-CAC, EGT, Drive Pressure all set up to log externally with EFILive. In theory.

Where do you have the drive pressure setup attached? I have the same setup (I think) but its not set up for logging yet.

 

[LarryJewell]

Looks Good Larry,I hope you prefit the dash before painting it

:hug:

gauges going in tomorrow