Pipe pressure guage

lancelarue · Feb 4, 2012

I thought I would pass this on.
Finally found a good accurate, waterproof, shock resistant low pressure digital guage to measure pipe pressure. In past experience I could hook up 3 analog guages to the same plenum and get 3 different readings. Maddening to say the least.
Omega 3500B is the guage. I configured this one 0 to 15 psi and it runs on battery. Has actual,high, low, & recall so you can make a pull up the mountain and pull it out of your pocket hit recall and wa la!!!!!
Should have done this years ago----------

lancelarue · Feb 7, 2012

Already figured out the heat soak problem that's been running me around in circles with the 860. Never would have believed it, but the can wouldn't flow enough. 2 1/4" inlet
2 1/2" between chambers with a 2 3/8" outlet.
Modified a different can now my pressure finally went down so I need to tighten up the pipe.
WHAT A DIFFERENCE !!!!!!!!!!!Now happy motor!!!!!!!!!!!!!!!!!!!!!!!!!!

Boyko · Feb 7, 2012

Thats a bomb proof looking gauge.

So how much of a change in pressure did you end up with?

LRD · Feb 8, 2012

lancelarue said:
I thought I would pass this on.
Finally found a good accurate, waterproof, shock resistant low pressure digital guage to measure pipe pressure. In past experience I could hook up 3 analog guages to the same plenum and get 3 different readings. Maddening to say the least.
Omega 3500B is the guage. I configured this one 0 to 15 psi and it runs on battery. Has actual,high, low, & recall so you can make a pull up the mountain and pull it out of your pocket hit recall and wa la!!!!!
Should have done this years ago----------

How about a link to where you found this gauge. I googled Omega 3500B and got everything but a gauge!!!

And what kind of Lbs are you reading and looking for in the pipe. If I remember right TurboAl said a number of years ago about 2.5 to 3 PSI were good #"s. Where do you have your sensor, midddle of belly etc.?

Thanks

and Good Luck

lancelarue · Feb 8, 2012

I went with the same in & out on a straight through style can and dropped 1 1/2#'s.
I needed to drop .6 #'s. I have a bolt in the stinger to adjust the pressure so I need to turn it in some more to bring the pressure back up. I'll see what it takes to keep my target pressure up at altitude and count the turns on the adjusting bolt. Only takes a minute to adjust.
I ordered the guage with automatic shut down in 15 minutes so I wouldn't have to worry about forgetting to turn it off (batteries). Now I'm wishing I wouldn't have done that as when I'm testing a new change like the can I have to keep turning it off and on after each test so as to not lose the next test data if it shuts down. Not a big deal but ----- Here's the address http://www.omega.com/ppt/pptsc.asp?ref=DPG3500&ttID=DPG3500&Nav=

lancelarue · Feb 8, 2012

LRD said:
How about a link to where you found this gauge. I googled Omega 3500B and got everything but a gauge!!!

And what kind of Lbs are you reading and looking for in the pipe. If I remember right TurboAl said a number of years ago about 2.5 to 3 PSI were good #"s. Where do you have your sensor, midddle of belly etc.?

Thanks

and Good Luck

I think to play it safe a person should take some baseline readings off a stock Ski-doo or Polaris with "their" guage and go with that to start with.
Like I said before the other problems I had with the analog guages all reading different. I always had a pressure guage hooked up when I was running the dyno and every guage would be different sometimes over a # different!
Al and I have been talking for years and yes he see's 3#'s at his shop @ 1,500' elevation. I checked a sled the other day again and it showed 2.93 #'s here @ sea level baro about 30.6".
I can tell you you will be amazed if you're under pressured, and you start to turn the bolt in, the seat of the pants dyno goes nuts.:whip: Same holds true if you're too high a pressure.:nono: No top end on my motor, noise out of the intake was terrible and of course the inevitable heat issues. !!?????
You can pick up your pressure pretty much where you want. It's just a pressure vessel. I put mine about 3" ahead of the stinger in the rear cone so it's easy to plumb to on the sled. Keep your plumbing as small diameter as you can to the guage with as short as you can. This time I went with 12" of 3/16" brakeline tubing to 1/8" npt and then to 3/16" hose.
I also put a quick connect chuck makes it nice.

lancelarue · Feb 8, 2012

One thing a guy needs to keep in mind, No matter who's pipe you're running, or who's can, if you're not running the build that the pipe & or can was designed for, at the correct altitude it's a crap shoot. If you're running a mod motor that's " out of the box" you don't know what exhaust is actually doing with YOUR motor with YOUR build, at YOUR altitude, it's just a guessing game.
We have pretty big air in Alaska and lower elevations & this will really make a difference.
The other thing is the actual design of the can you have. I've never played around with the stock cans because of their size and weight but I believe my 06' Summit X stock outlet is 2 1/4". Might flow my motor here because of the design, but I kind of doubt it. Anyway, I don't want to pack it around !!!!!!!!!

lancelarue · Feb 8, 2012

My next project, now that I think I'm going the right direction is going to be a friend's Polaris 910. This should really be good with the heat soak issues with this motor. I'm thinking it will be interesting the results when we get done with the pipes at these lower elevations--------

wellfed777 · Feb 8, 2012

really interesting stuff keep it coming

LRD · Feb 8, 2012

Thanks for the great info. I fooled around with pipe pressure way back in 91 or 92 when I put a 617 Rotax in my Phazer and had to design and build a pipe and can to fit it into a space about the size of an XP or Rev. I was aware of pipe pressure from my Tom Turner 2-stroke software when I designed the pipe. So I had put in a sort of butterfly valve with a large hole through it that was in the outlet of the can and could be rotated externally for more or less restriction.

Currently on my TNT big bore mtn mod with pipe and can have a couple different size restrictors (small flanged tubes different thickness) that slip in the end of the pipe. Have been afraid to really go after it without being able to actually measure the pressure first with the stock can at flatland altitude.

Kind of funny RKTEK wrote a tech article on his website claiming you can't measure exhaust pipe pressure!!!

Thanks again for the great info!!!

Good Luck

lancelarue · Feb 8, 2012

LRD said:
Thanks for the great info. I fooled around with pipe pressure way back in 91 or 92 when I put a 617 Rotax in my Phazer and had to design and build a pipe and can to fit it into a space about the size of an XP or Rev. I was aware of pipe pressure from my Tom Turner 2-stroke software when I designed the pipe. So I had put in a sort of butterfly valve with a large hole through it that was in the outlet of the can and could be rotated externally for more or less restriction.

Currently on my TNT big bore mtn mod with pipe and can have a couple different size restrictors (small flanged tubes different thickness) that slip in the end of the pipe. Have been afraid to really go after it without being able to actually measure the pressure first with the stock can at flatland altitude.

Kind of funny RKTEK wrote a tech article on his website claiming you can't measure exhaust pipe pressure!!!

Thanks again for the great info!!!

Good Luck

Thanks. I wish I could say I came up with all this on my own but 90% I learned from Turbo Al over the years and what I realized when I had the dyno going.:face-icon-small-hap

PTE800 · Feb 8, 2012

Pipe pressure

Here's some thoughts that are from Dyno Tech Research's dyno session on a RK Tek 925 Big bore Artic Cat.

Now we fitted the pipe with the dyno instrumentation that registers pipe center section temperature and pressure. This sensor replaces the stock sensor (creates max timing at about 900F). When we disconnect the stock pipe center section probe, the ECU defaults to max timing. Rider X and Tech X had surmised that if this 2012 stock muffler were a bit “loose” for Billy Howard’s stock 800, the 925cc top end’s added airflow CFM could create optimal conditions.
To generalize, 4 psi seems to most often a best average pipe pressure for best torque and HP.
Too low, and too much charge/ air mix can be allowed to short-circuit out the exhaust
making only extra EGT and no power. Too high, and often deto-producing active radicals
can be packed back into the combustion chambers creating havoc. But today, the stock
800 muffler seems just right!

lancelarue · Feb 9, 2012

I've read this. Interesting that is what they see there. Sure had me wondering after I received my new expensive precise pressure guage (±0.25% Test Gauge Accuracy ). This is one of the reasons I said earlier to set your own baseline with YOUR guage on a stock Polaris or Ski-doo. I don't know what Cat does. I've heard that they do run pretty "loose".
Seems strange they're wanting to tune the system with the can and not the pipe?

lancelarue · Mar 9, 2012

Well I'll tell you this has been quite an education this last month or so. I've tested several combinations of pipes & cans including stock to get baselines.
You can really get in trouble quick with the wrong pipe / can combinations. ( I have quite a few pistons re-nicked cylinders from the last 10 years to prove it).
We have such a huge altitude variation here where I live. We've had huge dumps right here at sea level and we go to 6,000'.
On my new guage I'm seeing 3#'s on stock and aftermarket systems that work. The motors just love it there. Drop down and you can hear it and feel it in the throttle response for sure. The danger area is when you go over that it will still feel / sound good if you're not too high, but things really start "glowing"!!!!!!!!!!!!!!!!
Tested everything from full on mod 860 big bores to 440's. What an education!!!!

LRD · Mar 9, 2012

If its not a secret or whatever could you describe/or pics of the apparatus you are using to adjust your pipe restriction? From what you have said sounds like you have something that works fairly quick and easy.

Thanks

lancelarue · Mar 9, 2012

As I described earlier, drill a hole & weld a nut to stinger to run bolt into pipe to adjust restriction. People have been doing this for years. The difference is I finally spent the money and bought a guage to measure it accurately.
Generally am dealing with too much pressure because of mods / big bore situations so I oversize the stinger to be able to adjust with the bolt. I've noticed if a person goes too big, and you have to run the bolt down too far, motor doesn't seem to like it? In my case when that happened, I just put a reducer ring inside to get closer to target pressure, then just fine tune with the bolt.
On a Skidoo race 440 we just drilled the pipe sensor plug in the middle of the pipe(06' ) welded a coupler cut in half & then put a " T ". One side of the " T " goes to guage, other side I ran 1/4" copper tube out & down to can outlet hole. Sent the kid out with the guage and a pair of vice grips to tune his pipe pressure!!!! Wa la---Pipe pressure dropped from 3.9#'s ( stock pipe & can ) to 1.8#'s with the tube open. He sqeezed the end down until he hit the target # which was 3 #'s. DONE. Ready for race. This was a quick fix to get away from having to modify the pipe etc. Sled ran awesome.
Say the next race is at 3,500' instead of here at sea level- pipe pressure will drop because of altitude, so, maybe won't need so much bleed off. At any rate, totally adjustable to keep the motor happy and the pipe working without the dreaded pipe heat soak issues on the long straights.
On the 8oo's and bigger I usually weld a 2" stinger and reduce down to adjust pressure. Example would be a 800R in an 09' XP. SLP Pipe with a "Thing" can which is a really good combo. Modified exhaust valves that open fully approx 4,500 rpm, Boyesons,13.25 to 1 compression- 2" outlet with a 44.5 mm restrictor should be close. ( We'll be finishing one today). Stock pipe / can pressure is 3#'s. That's where we'll be when we're done.

BCROCK · Mar 11, 2012

i played around with the restrictor bolt trick last season and melted a few motors.when i started i believe i was at 1lb and i think i ended up about 3.5lbs or 4. the motor ( flannery full mod 600) ran much better with the higher pressure but produced too much heat, basicaly doing what looked like a cold seize after 3-4 laps.is there a happy medium # or is just an expensive crap shoot till it doesnt melt?

lancelarue · Mar 11, 2012

Check your guage on a stock motor. There's your baseline.

LRD · Nov 8, 2013

I bought the Omega Gauge as recommended except without auto shutoff early last winter.

Wow free HP found.

My sled is a 08 TNT 600 carb I built into a mtn sled with 15 X 141 X 2.25 track and 365 lbs dry weight, so performs great and very high fun factor because of low weight.

Engine ported and bigbored to 621.

Did some preliminary testing at low altitude in MN before going out west to get an idea of pressure in the system. Note I have Carbon Fiber cannister and expected it to be low and it was.

When we were out in the mtns first put in my largest ID reducer bushing for the stinger of the pipe and had only about 1.8 lbs of pressure. With 1.8 lbs engine would pull 7700 rpm on repeated runs. Then added my smallest ID reducer bushing to the stinger, pressure jumped to 2.8 lbs and r's went to
8100, right where I wanted them. Without the ability to check the pipe pressure and adjust accordingly would have had to pull a lot of weight out of the clutch.

I have been chasing this idea for 20 years and finally with the digital gauge can measure it accurately. Have previously tried a mechanical gauge for measuring exhaust back pressure and no consistency at all. Worthless!

My sled ran and performed the best it ever has in the mtns.

The testing tells me also if your exhaust system leaks anywhere your losing a great deal of performance.

Good Luck

Thanks Lancelarue, my sled rocks now a lot more than it did before

lancelarue · Nov 8, 2013

Pipe pressure

Sure is nice to get rid of another variable! Glad the guage is working good for you.
Have a set of big twins to tune here pretty quick. I can't wait to see what's going on--------

Pipe pressure guage

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