drive pressure

i was wondering how you were measruing it. anybody got a pic of how they set it up. and what kind of pressures are you see like, whats normal, high, bad...
 
cm cows said:
i was wondering how you were measruing it. anybody got a pic of how they set it up. and what kind of pressures are you see like, whats normal, high, bad...
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Dont have a pic but you either tap another 1/4 NPT in the manifold or pull out your Pyro and Put in a 1/4 fitting with a ferral end( just like a 1/8 boost fitting but 1/4" and get about 4ft of 1/4 copper tubehook it up to the manifold,run it across the valve cover ,once you get it across that far coil it up about 5-8 time to help disapate the heat so it wont melt the 1/8" boost line your about to hook it to.after you coil it up run the rest of 1/4" copper tube over by the brake booster than you'll need another 1/4" male ferral fitting and a 1/4" to 1/8" coverter then run a boost tube kit to a guage.
 
how imortant is it to have this hooked up and monitored? will it be more nessicary to watch on a set up with a mild to large set of injectors with a smaller turbo?
 
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you don't really have to watch it, but it can show you a boost leak or other issues.

good to know where you're at, but no reason to hawk eye it.
 
And would most needed at time of set up change to determine if you put together the correct air to fuel mix. Once your done tuning you'd never need it again until issues arise
 
cm cows said:
how imortant is it to have this hooked up and monitored? will it be more nessicary to watch on a set up with a mild to large set of injectors with a smaller turbo?
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Just for tuning a setup especially in twins, but with all the engine combos most people have a good idea where they stand, some do it to try to find a problem or just optimize their setup with their wastegate
 
Forrest Nearing said:
as long as you didn't plumb the copper into your mouth, I don't see a problem w/ that for dialing in a combo :hehe:
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If I took the guage off it'd be like a little in cab stack :st:
 
Red Stroke said:
Jim interesting write up, you must work for a fluid power company?

High BP also holds the exhaust valves open and increases the chances of kissing a valve with the top of the piston, if runnning twins you should always put heavier spring rate springs on the valves.
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No, I am just a dork.... :bang

Not true for 24 valve engines right?

Jim
 
OK some examples. I do not know how to calculate the actual pumping losses so these numbers are just the change from the minimum pumping loss to the change in pumping losses caused by drive pressure.

Baseline
1.0 DPR
35 Boost
35 Drive
3200 RPM
0 Change in Pumping Loss Hp

A Screaming HX35
1.9 DPR
35 Boost
65 Drive
3200 RPM
44 Change in Pumping Loss Hp

Nice Set-up
1.5 DPR
35 Boost
52 Drive
3200 RPM
25 Change in Pumping Loss Hp

Diesel Freaks So So
1.2 DPR
60 Boost
70 Drive
3200 RPM
15 Change in Pumping Loss Hp

Wet Dream
1.1 DPR
40 Boost
45 Drive
3200 RPM
7 Change in Pumping Loss Hp

My Exhaust Brake
#DIV/0! DPR
0 Boost
60 Drive
3200 RPM
87 Change in Pumping Loss Hp

Cruising in a 5.9 Liter Diesel
1.2 DPR
5 Boost
6 Drive
1900 RPM
1 Change in Pumping Loss Hp

Cruising in a 5.9 Liter Gasser
-0.3 DPR
-11 Boost
3 Drive
1900 RPM
12 Change in Pumping Loss Hp

Stupid I know....:shake:

Jim
 
Red Stroke said:
High BP also holds the exhaust valves open and increases the chances of kissing a valve with the top of the piston, if runnning twins you should always put heavier spring rate springs on the valves.
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I got to re-thinking this..... *bdh*

How would the valve kiss the piston?
Just happens?
Possibly caused by poorer volumetric effientcy of a stock 12v head?

In theory:

Lets say we are just before TDC on the exhaust stroke with the exhaust valve still open. Because the exhaust valve is still open the pressure in the exhaust port = the pressure in the cylinder.

Now right at TDC the exhaust valve closes. The pressure in the exhaust port drops rapidly venting into the larger volume of the exhaust manifold. Where the pressure in the cylinder stays constant as it has no vent path.

Two scooches past TDC and the intake valve opens. The cylinder can be pressurized to boost pressure. But pressure already exists in the cylinder because boost = drive (or hopefully close to it) and no air flows into the cylinder until the piston starts down.

Now BDC intake stroke. The cylinder is filled with air only because of the increasing volume. But the pressure in the cylinder stays constant the whole time. This is where cylinder pressure = boost pressure and the intake valve closes.

The cylinder never loses pressure in relation to the exhaust manifold during either exhaust or intake. Where would the force to open the exhaust vavle come from?

I can see how an exhuast brake could possibly make this happen.

Sorry guys, you know I am dork;
Jim
 
(quote) Now right at TDC the exhaust valve closes. The pressure in the exhaust port drops rapidly venting into the larger volume of the exhaust manifold. Where the pressure in the cylinder stays constant as it has no vent path (quote)

Now picture 100 psi of back pressure typical to some twins, the pressure venting into the manifold you speak of is more like a 100 psi pressure vessel with the spring pressure trying to pull the valve closed.

Now lets say you have a 2" diam valve.
(pie)* r2= 3.14 x 100 psi is 314 lbs holding the valve open against a 60 lb spring. Give or take a little.
 
Hanging open exhaust valves would not be much of an issue due to the gas direction of flow (cylinder pressure is always higher than Exhaust manifold pressure). The Impulse would actually tend to close the valve.

However, on the intake it is the exact opposite. Gas flow is into the engine, and the impulse on the intake valve would tend to cause the valve to hang open.

LOL, BYW, I am the Fluid Power dork!!! I will have my BSME in May!!!!!!
 
There was a post, a while back, where they guy used copper to one of those tin fuel filters then nylon from the other side to the gauge. I have been thinking of using an electric gauge but I dont know how accurate they are.
 
dodge359 said:
There was a post, a while back, where they guy used copper to one of those tin fuel filters then nylon from the other side to the gauge. I have been thinking of using an electric gauge but I dont know how accurate they are.
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That was me. But my truck hasn't moved since the weekend after I put it on.


Me at half throttle
1.1 DPR
70 Boost
80 Drive
3200 RPM

Me at WOT
1.1 DPR
130 Boost
145 Drive
4500 RPM
 
Good reading. Here is a little question. Say you have a 62/14 over S400 twin setup and you replace the 62/14 with a 64/14. Will this change the drive pressures at all, if the exhaust housings are the same? Also, would going from a 65mm turbine wheel to the 71mm wheel lower drive pressure?
 
Rodram2002 said:
Good reading. Here is a little question. Say you have a 62/14 over S400 twin setup and you replace the 62/14 with a 64/14. Will this change the drive pressures at all, if the exhaust housings are the same? Also, would going from a 65mm turbine wheel to the 71mm wheel lower drive pressure?
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Dont think you would notice much difference in drive pressure between the 62 and the 64 but going to a 71 over a 65 will free up some drive pressure and open it up more fot top end power.

Member "Ph4tty" made 540ish hp today with his 62/71/14 over his previous 64/65/14 that only made 490ish hp Same setup.
 
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