Pipe pressure guage

I finally finished longtracking my wifes 09 TNT 600 carb with stock engine and exhaust. So was able to get some baseline numbers for stock engine at low altitude.

In MN at 1000 ft am seeing 3.75 lbs to 3.89 lbs at 8000 to 8100
rpm. My big bore ported 600 carb with Straightline pipe and carbon silencer
with a reducer insert in the pipe stinger was only making 2.34 lbs off pressure.

A couple of recent issues of DynoTech Research have a lot of pipe pressure info
on the cat 800. They picked up hp and moved the HP rpm point up about 200 rpm by raising pipe pressure from about 2.5 to 3.5 lbs. Amazing engine they were getting 170 hp with computer tuning, pipe/can, and Lower compression head, exhaust pressure increase and no porting

What DynoTechs #'s tell me is if you don't raise pipe pressure in the mtns to what it would be at sea level the HP rpm point will be a bunch lower.

pipe pressure

One thing I don't see people talking about who are tuning pipes / pressures
is fueling. Typically it changes with pipe pressure changes and needs to be monitored pretty close to be safe if you're going from a tight system / too high pressure to a looser system / lower pressure. Going the other way, they will go fatter & lose power and fool some folks thinking the motor doesn't like the tighter pipe. After adjusting the fueling back to baseline, power goes up------
3.5#'s will show good power but I wouldn't run quite that high for fear of the long pulls / internal heat. Corner to corner or shorter runs would show good though.

I was kind of surprised how high the pressure was on my wifes 09 but the 600 carb motor in stock form isn't much above a lawn mower engine on the exhaust ports, real low exhaust port heights. Would think that might be part of why it can get away with it, piston closes off exhaust port a lot sooner keeping out more of exhaust heat.

Quick, somebody make an aftermarket kit! Solenoid controlled variable orifice in stinger working with closed loop feedback to maintain a pipe pressure set point with controller/readout combo in dash - sounds like $$$ to me. I am actually surprised Koso and other EGT mfg's haven't done this yet...

robm said:

Quick, somebody make an aftermarket kit! Solenoid controlled variable orifice in stinger working with closed loop feedback to maintain a pipe pressure set point with controller/readout combo in dash - sounds like $$$ to me. I am actually surprised Koso and other EGT mfg's haven't done this yet...

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This is funny , i sent lancelarue a pm this morning asking about more info on where the pressure tap location should be and the bolt set up location , I run the ViPec standalone in both my sleds , turboed apex and N/A 800 Pro .
I am thinking about adding a pressure sensor on my pipe wired to the ViPec on my Pro (can be done very easy) then you can data log this pressure and see how the Barometric pressure effects it , and yes if there was a solenoind valve of some type you could set up a map in the ViPec that would control said valve to maintain set pipe pressure.
I never thought about how the pipe pressure would change when the baro pressure changed and how this would afect your tuning , interresting?

And yes i do have a pressure sensor already installed on my turbo inlet on my apex , to much turbo backpressure ( heat ) is not good for your valve train , cyclinder etc

robm said:

Quick, somebody make an aftermarket kit! Solenoid controlled variable orifice in stinger working with closed loop feedback to maintain a pipe pressure set point with controller/readout combo in dash - sounds like $$$ to me. I am actually surprised Koso and other EGT mfg's haven't done this yet...

Click to expand...

Check out this thread by TurboAL, back in 08 he mentions how he did it some time before that.

http://www.snowest.com/forum/showthread.php?t=96603

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----------

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good thread. Sledrock and I have also installed the pressure gauge, we have a smaller 2.5 inch digital with 0-5 psi range that holds the high as well. I,m mounting her in the dash and can hit the button and alter her wherever i ride, takes seconds! what a great tool. two knowledgeable builders have talked me into this, Great concept.

Pretty cool, what turbo Al is describing is essentially a relief valve, spring rate would have to be quite low. This would guarantee your desired pipe pressure (or very close to it) at less than WOT and with elevation changes, would only need to choose the correct spring rate to yield the correct pressure. Or alternatively have a mechanism of varying spring preload. Pretty cool conceptually, but probably tough to pull off from a design standpoint (thinking durability/reliability factor with moving parts in adverse conditions). Way simpler than my brainwave, but not as "tweakable" which brings me to a question:

How do back pressure requirements change with engine rpm? I.e I would assume more rpm requires more backpressure for efficient scavenging... Linear relationship? If so then Al's setup could be the ticket. Couldn't get the speedwerx link to work ...