Drive Pressure Data Logging, Part 1

[McRat]

Been a bit busy. Casper is now running again but with a special S400 charger on top from Borg Warner/AirWerks/HighTech.

I need to start recording drive pressure, so I drilled and tapped the pedestal spacer for both 1/4 NPT and 1/8 NPT.

I bought a Oil pressure gauge from Summit for about $20. I found that when using a 470 ohm resistor to split the voltage:

120 PSI = 1.33v
100 PSI = 1.71v
80 PSI = 2.15v
60 PSI = 2.70v
40 PSI = 3.15v
20 PSI = 3.60v
0 PSI = 4.20v

While not perfect, this should give a good enough range for EFILive's external ports on the V2, which understands 0 to 5.0 volts.

I did the mapping with an air compressor and eight AA batteries, so this should give me some extra wiggle area when dealing with a car battery and alternator.

Next I got:

1/4" aluminum tubing (to dissipate heat), 3' long
AN-4 to 1/8 NPT fitting (male to male to go into the pedestal)
AN-4 to 1/8 NPT fitting (male to female to the gauge)
AN-4 nuts and sleeves (2 each)
37 deg flare tool.

Materials are about $30 plus tools.

I should hook it up tomorrow and take pictures and draw a schematic. Not much of a schmatic since it's one stinking resistor.

 

[Mike]

sounds like your on a mission.

:grd::grd::grd:

I'll be settin back admiring and learning :happy:

 

[LBZ]

X2!!
Wow creative.

Would it be possible for someone to log this using the existing and presumably unused EGR sensor wiring?

Hope I'm not in left field on this, I have been thinking about logging drive pressures myself. Just need to find the right 5 minutes.........

Although just monitoring it Simon Ghetto Style seems a lot more within my range of capabilities!!

 

[sweetdiesel]

Very cool Pat!
im going to rig mine up like yours if i can?
i have the ultralite electric 0-100 psi gauge and IIRC thats already 0-5v?

 

[McRat]

Preliminary data (I'm breaking in a new engine) is drive pressures up to 70 PSI when boost is up to 30 PSI. This is about 1.9:1 drive pressure ratio. Always add atmospheric pressure to get Absolute before doing the math, or 70+14.5 / 30+14.5. This reading was probably a spike off a bark though.

If I average the reading from 10PSI to 30PSI boost, I get 1.26:1 drive pressure ratio. This jives nicely with the published compressor efficiency.

 

[McRat]

I tried to take pictures, but just had crap luck all day. 2 camera DOA, third missing chip.

The S400 is more "mellow" than the GT42. It does not come on as violently. I kinda miss that OH SHIIT when the boost climbs though. I'm in this for the adrenaline.

 

[JOHNBOY]

Pat

Did you drill thru the centerweb of the riser also? I heard some people say that divivded housings can have different readings from side to side. It does kind of make sense but pressure is pressure so it should be equal?

I bought a 100psi oil pressure sender to do mine and some 1/8" SS tube.


Keep up the good work!

 

[McRat]

No, but I did tap both sides. In theory I can do each side to see if they read different.

This 1/4" aluminum is working very well so far.

I also put in a pyro in the other hole, but that didn't work right. The pyro was not long enough to get into the air-stream, so it's just reading the temp of the pedestal block.

I promise I will get some pictures. Hmmm... I'll try right now. Currently I have SPA sending units in the block so I can read it both with a gauge and EFILive. I will put the Cheapo sending units back in once I get a good feel for the data.

 

[McRat]

A "rat's nest" of wiring:

 

[McRat]

It's too dark, but this shows where I tapped into the block.

 

[dmax tim]

A "rat's nest" of wiring:

scares me and I'm fearless :rofl:

 

[sweetdiesel]

hmm, my DP shows same as boost all the time

Nice work though Pat and glad Casper is up and running again

 

[BIG DIPPER]

Pat, you think it's more suttle not being BB?

 

[McRat]

hmm, my DP shows same as boost all the time

Nice work though Pat and glad Casper is up and running again

They should go up at the same time, but the drive pressure has to be more than the boost pressure on the average.

The journal bearing seems work just fine. Never have figured why everyone panics about journal bearings. Most big turbos use them with very good results. The drag on a charger is not much of the equation.

 

[sweetdiesel]

2 Questions

how or what will change my drive pressure? it was easy to see the vane on the stock turbo changing the DP

And with my setup installed into the BD drivers side manifold is this not as good as the pedestal?

 

[McRat]

Installing in the manifold is fine. I only installed in the pedestal because it will be easier for me to change things around.

Drive pressure has to do with the efficiency of the charger, and size of the compressor and turbine. If your drive pressure gets to a certain RPM then goes through the roof, you've went off the map. If it never goes nuts even after the power falls off, you probably has too big of a turbine housing.

 

[SBCNX20]

Pat ive read that kinda a smallish turbo?? Whats the thought behind the change?

 

[McRat]

No, this charger is bigger than normall for an S400. It is 74mm inducer yet a T4 mount instead of a T6 "Diesel" mount.

IGNORE FOLLOWING:

Solid = positive
Blue pair = data3
orange=4
green=2
brown=1

 

[McRat]

.6 ohms for 15'

 

[McRat]

Picture1 - I soldered a 470ohm resistor between those two connectors to protect the resistor. This will be the 12v input.
Picture2 - I soldered a ground strap to a 1/8 NPT f-f coupler to get a good ground. Most gauge problems are grounding. Also you see the Summit sending unit, and you see that I wrapped the resistor assy with tape to protect.
Picture3 - The resistor goes on the "spud" then to 12v. You will attach the 5v Gauge Positive wire to this. The ground goes to chassis ground AND the gauge ground.
Picture4 - I'm using a piece of network cable. These have 4 pairs of wires that are color coded to each other, are cheap, and you can replace easy.