Gauges Installed - What Do the Numbers Say?

[tugboatphil]

At the same time that I installed a 16cm housing, I finally put some gauges on. Not thinking about it until later, I didn't have any "before" numbers for my gauges, to base the readings against.



Currently I get 18 lbs of boost at WOT. More usually 17-17. 5, but 18 is max. I haven't had a heavy load yet, but exhaust temp going up a fairly steep grade holds at 1150. Temp quickly decreases when I let off the throttle.



Also, with the smaller housing, when I've been going uphill and quickly let off the throttle, it sounds like the turbo is freewheeling. Is this normal? Will it tear anything up?



Thanks for the help.

 

[fox]

Your boost pressures are nornal for a stock truck.

Where is the probe for the pyro?

Is it pre-turbo or post turbo.

If it is pre- it is ok, if post- it is very hot be careful.

The turbo noise when lifting the throttle can be damageing but few with stock motors have broken.

Some call it "sneezing".

 

[tugboatphil]

Thanks for the reply. I forgot to say that the pyro probe is pre-turbo. I had read different opinions on placement, from 2 inches from the flange to 3/4" from flange. I put mine 1 1/4" from flange and centered on the rear manifold port.



This turbo sneeze, is it because the exhaust side is spinning too fast for the intake? Would a larger intake impeller make up for this? Would the same be true for going to an HX-35?

 

[Greenleaf]

Turbo Chuffing

We tractor pullers call this "chuffing". Why,I don't Know. We just do. It is caused by the compression of air going into the engine at high velocity/pressure, then when you decide to pull your foot up off the throttle,the engine slows abruptly. All of this compressed air looks for the path of least resistance,which is your air filter.



Attend a Grand National tractor pull sometime. When they shut 'em down you'd think the engine just blew. Keep in mind. you have 18 psi, we have 140 and the turbo "hoses" are not hoses, steel pipe sealed by way of "o" ring.



Scott

 

[BushWakr - RIP]

The actual term is "compressor stall".



The cause is as described above... . high boost followed by instantaneous release of throttle, which means the boost air rushes back to the compressor side and trys to stop the pinwheel from turning, and can actually "stall" the wheel of even blast it in reverse.

This is commonly seen at much higher boost pressure though, and not seen at the pressures you are seeing.



On a side note, my experience has shown that if the pyro is mounted pre-turbo the gauge responds much faster to EGT's.

If the probe is post-turbo it responds slower, AND there is an error in actual temps. For example, I found that 10*F for every 1 pound of boost was pretty close... UNTIL you were at or over about 23-25 psi boost. At that point the error factor was increasing. As an example you might be running 1200*F on the gauge, and at 25 psi boost your error would be around 11-12*F for every 1 pound of boost.

This error also grows beyond that as well, to the point you could very well be off by 300*F or even significantly more as you go up in boost pressures.



bob

 

[tugboatphil]

So as far as the stall on the compressor, is it damaging in the long run? Would going to a larger turbo be a solution, or would that create it's own problem by not having an increased fuel flow?



I found that my tailpipe had a dent in it, on the top of the pipe, right where it goes over the axle. I dropped the tailpipe and muffler, just so I could hear it running straight. It was GREAT!! I never heard the turbo so clearly before. I do too much work in residential areas to get away with it for long. So I knew I had to put the stuff back on.



Anyway, I ran down the road and got 20 psi on my boost. Going up the same hill my pyro read not quite 1100. So when I got back to the house I noticed that something was rattling around inside my muffler. So I dropped the muffler and tailpipe from ol' Blue, my trusty 90. I had replaced both of these within a year of shutting her down.



I put the "new" stuff on and didn't notice any changes from having the bent pipe on. Of course, I just ran a little way down the road yesterday, as I could wait to get home and dig taters.



Not being able to afford an entire exhaust right now, does anyone know of a good straight through muffler that is available for a stock exhaust system?



Thanks.

 

[Greenleaf]

Muffler

When my 3. 5" muffler-less exhaust system terminated at the factory location it wasn't loud enough to bother my wife! It wan't loud enough to suit me. Now that it is 4" and terminates at the passenger side door it's really loud! My wife cringes when I pull a hill.



Point is, it's not loud enough to bother my wife with out a muffler,you may wish to consider placing a pipe in place of it,the muffler that is, not the wife



Scott

 

[tugboatphil]

If only it was my wife, I wouldn't have to worry about the noise. Problem is that it's my work truck and at least once a month I'm all around the state capital and they're pretty strict on noisy and/ or smokey vehicles.

 

[cerberusiam]

Most exhaust shops should have a 3 inch straight thru truck muffler that will work. I used one and it sounds pretty good. Doesn't buzz at road speeds at makes enough noise you know there is something there.



As far as the "compressor stall", "chugging", or what I called "turbo bark", I had the same thing on mine with the H1C/21cm housing after I opened up exhaust, air and fuel. The problem I ran into was the turbo gave up after 10k miles and started oiling down the intercooler and making all kinds of strange sounds. Replace it with an HX35 with bigger compressor and 16cm housing and have heard it do it anymore. Not sure if what contributed most to turbo failure, 250k miles or too much boost. If it is stalling the compressor and/or spinning it backwards there has to be some stress on the bearings so one could assume it would contribute to early failure.



The two biggest improvements on mine were getting rid of the exhaust restrictions and opening up the air box. That crushed tailpipe and a muffler necked down to 2. 5 inches was a real performance killer.