I have seen a few trucks with 2 holes drilled in the exhaust manifold and one always has a copper loop like a still. What is it? Why?

You can see it here:

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/26-engine-systems/482-holset-he351ve-install-retrofit-2nd-gen-cummins

Pressure tap for a gauge to measure drive pressure. The copper dissapates the heat.

Most common on twin turbos or something special.

Edited September 20, 20159 yr by CSM

That is for a drive pressure gauge to measure exhaust pressure basically, one needs the copper coil to dissipate some of the heat before it turns into the plastic pressure hose, mos generally use a boost gauge to measure exh drive pressure, in a perfect world drive pressure should be as close to or less than 1:1 but with different turbo designs and restrictive exhaust systems the drive pressure is generally higher especially if one adds more fuel via a comp box injectors ect.

Perfect thanks guys!

Now just for information value...

 

Wild & Free how far would you go on the drive pressure to boost pressure offset safely? Ratio?

Now just for information value...

 

Wild & Free how far would you go on the drive pressure to boost pressure offset safely? Ratio?

 

Right wrong or otherwise without scientific data I am a 10% variance kinda guy with things like this guy. If the drive pressure got to more than 10% more than boost I would be looking to improve on things.

There are also a very long list of variables that can affect this and I would be watching the egts along with it, if egts are still safe @ the 10% over I would feel safe going higher.

Right wrong or otherwise without scientific data I am a 10% variance kinda guy with things like this guy. If the drive pressure got to more than 10% more than boost I would be looking to improve on things.

There are also a very long list of variables that can affect this and I would be watching the egts along with it, if egts are still safe @ the 10% over I would feel safe going higher.

 

I would like to find a gauge like the below for my truck and play with it... If for nothing else but the fun factor. 

 

http://www.hewittindustries.com/pressure_gauges_boost_dual.html

Edited September 21, 20159 yr by CSM

Right wrong or otherwise without scientific data I am a 10% variance kinda guy with things like this guy. If the drive pressure got to more than 10% more than boost I would be looking to improve on things.

There are also a very long list of variables that can affect this and I would be watching the egts along with it, if egts are still safe @ the 10% over I would feel safe going higher.

 

That could be rather thin for margin. So for stock turbo and your running 30 PSI and where 33 PSI drive pressure or a mere 3 PSI difference that is your 10%.

10% is kinda stiff.  That is basically where the stock turbo sits.  Anyone that is running an HE351 is seeing a heck of a lot more.   The problem is the tight exhaust housing trying to get it to spool at low RPM's.  The DP on cylinders 1-3 just about hit 60 psi at 35 psi boost.   That is because I'm only wastegating 4-6. 

 

 

I have an idea I've been wanting to try for years.  The goal, fast spooling and low drive pressure.

 

Here's a 4th gear from a roll.  Before the most resent round of mods.  I am very happy with my boost governor.  Clicking the image will make it bigger.

That is for a drive pressure gauge to measure exhaust pressure basically, one needs the copper coil to dissipate some of the heat before it turns into the plastic pressure hose, mos generally use a boost gauge to measure exh drive pressure, in a perfect world drive pressure should be as close to or less than 1:1 but with different turbo designs and restrictive exhaust systems the drive pressure is generally higher especially if one adds more fuel via a comp box injectors ect.

 

 

The 10% thing was just for me personally never intended it to be a broad all incompassing statement.

I'd say it greatly depends I know in my setup 2:1 (or more)in low boost situations is needed.

Once the turbo is going good it levels out to 1:1 pretty quick.

I can tune the ratio better, but spool is is way worse.

I look at it from the stand point of normal cruising the ratio is most likely close to 1:1 for most people but its when the hammer is dropped that things get stupid quick. Like I know my Hx35W and my +50 HP injectors and Edge Comp is pushing the upper end pretty hard. But I'm normally not drag racing everyone on the highway nor am I towing day in and day out. So understanding the limitations of my set up is key...

 

There has to be some sort of ratio that is usable and what is not. Heck we could always throw a H1C turbo on that thing has a huge exhaust housing at 21cm² that should do it right...

The ratio cruising heavily depends on RPM's Sub ~1600-1700 RPM, boost is higher.  Then it goes to about 1.1:1 Drive Pressure:Boost.  The Stock turbo seems to like 1800-2000 RPM, I can build 30 psi, while maintaining pretty close to 1:1.  Once the wastegate opens, all bets are off.  I would really like to get some towing data, so I can have a more sustained load.

Each setup is different in terms of what is acceptable for drive:boost. A HE351 on a stock truck can see 2:1 and be fine, thou lower is better. The cam actually plays a role in that. 

 

With my current setup I am generally around 0.8-1 until I get above 2600 rpms WOT and it can go to 1.2:1. 

 

I would actually like to drive to my turbo a little harder between 1600-2200 rpms above 5K feet a 1:1 or 1.1:1 for towing heavy. Thou I am not sure how...