Engine/Transmission (1998.5 - 2002) Measuring exhaust back pressure

[John Berger]

I will be installing my Pacbrake this weekend. I had to plug a 31/64 inch hole in the butterfly and drill a 1/4 inch hole out to 9/32 inch. I want to test the back pressure when I get it installed to make sure I'm not exceeding 60 psi. I have an air pressure gauge. What other parts do I need to monitor this as I'm driving the truck? I do not plan on making this a permanent setup. TIA

 

[Mark Craig]

John,



I have seen BD promote some products to do just what you asking I would give them a call they can probably tell you all you need to know.



Mark Craig

DPPI

 

[illflem]

All you need is the line to your gauge and whatever adapters necessary for it. At least the first foot of line will need to be heat proof.

I've seen some guys hook up a two way solenoid valve to the back pressure line and to their boost line with one line going to a 60 lb. boost gauge. The valve position is controlled by your e-brake switch. When the e-brake is on the gauge registers back pressure, when off turbo boost.

 

[John Berger]

Any ideas on where to get this type of stuff? I want to get the brake installed this weekend. I don't want to have to wait another week for a mail order, just because I want to test the damn thing. I have to get it installed this weekend or it will be at least three weeks before I can get to it again. I'm assuming the line I need is the same as what is used with boost gauges, as well as the couplings. How do you heat proof that vacuum line?

 

[TowPro]

The BD has a plug in front of the butterfly where a 1/4" NPT screws in. I just used the same gauge I use to check my Fuel pressure.

Originally posted by John Berger

Any ideas on where to get this type of stuff? I want to get the brake on this weekend. I don't want to have to wait another week for a mail order, because I want to test the damn thing. I have to get it on this weekend or it will be at least three weeks before I can get to it again. I'm assuming the line I need is the same as what is used with boost gauges, as well as the couplings. How do you heat proof that vacuum line?

 

[John Berger]

Towpro, you must be running a mechanical fuel pressure gauge. I called Advance Auto and they say they have different sizes of line. I have my air pressure gauge in the toolbox on the truck, so it's just a matter of getting the correct compression fittings, which they told me they have. I sure hope so. I really need to get this brake installed this weekend.



I have a Pacbrake. It has a plug right up at the top by the bracket that mounts to the adapter plate at the turbo outlet and it looks like 1/8 NPT. There is another plug down by the butterfly, but I'm not sure that it serves any purpose. I'm assuming that the opening at the top could be used for an EGT probe.

 

[illflem]

John, if it's just a temporary gauge you're after buy a copper mechanical oil pressure gauge feed line kit from any auto parts, under 10 bucks. Most come with all the fittings you need to go from the 1/4'' port on the e-brake to whatever size you need for your pressure gauge. Any fitting that may not come with the kit is easy from any place that sells plumbing. Tape the gauge to your windshield if you don't want to hassle feeding the line though the firewall. A $5 60lb water pressure gauge will work fine if you don't have a gauge.

 

[MUDDY]

harold bowers kits

harold bowers is making kits to enable you to use your boost guage to monitor exhaust back pressure. a valve in the line lets the boost guage work under boost reading boost presure and when ya let up, the guage reads the backpressure of the exhaust at your brake



he is getting 25bucks plus s&h for the kits, complete.



his email is -- email address removed --



his ph is 208 459-7849

 

[John Berger]

mexican jumping needles

Why would the needle be so jumpy? I noticed this when testing my fuel pressure with a 30 psi water gauge. When the truck was running the needle was wacko. It was wacko within a specified range, but wacko nonetheless. When I bumped the engine, the gauge went to a steady 15 psi as the lift pump primed the system and did not jump around at all. Same thing on the 160 psi gauge I used to test back pressure. It jumped around wildly. Do these things need some type of isolater, or is it just cheap manufacturing?

 

[jelag]

The fuel pressure gauge is pounding from the sudden change in pressure..... Where there is constant change in pressure a liquid filled gauge is used to slow down the pounding of the gauge and make it last a little longer... .



On the exhaust brake, I've suggested to several people that if they wish to test their back pressure, they go to the home improvment store and pick up a simple 100 psi gauge for an aircompressor..... usually under $10. Than plumb it into the system using either plastic or metal tubing... . The plastic will hold up as a test gauge but won't stand the constant heat from a long pull... .....



Hook up the gauge and run the truck down the road... I usually hook up a switch that allows me to turn on the exaust brake before the engine comes to an idle... ... I can buzz down the road at 2200 - 2500 rpm in 2nd or 3rd gear, hit the switch and let my foot off the fuel pedal at the same time..... the gauge should go to 60 or so... ...



We test all the brakes we install and I don't remember their ever being a problem with a new brake..... however on a change over or one purchased used I wouldn't trust the brake until I had tested it.....



Severe damage can be done if 60 psi is exceeded on the 24 valve engines... ...



Jim

 

[illflem]

John, the jumping needle is due to pressure pulsations. You need to use a gauge snubber or valve shut almost all the way down somewhere in the line to smooth it out. Many times you won't see the pulsations on an electrical gauge but they are there none the less hammering away on the sender. A $4 needle valve is cheap insurance to protect a sender or gauge.