I am starting a 1.6TD build version 2, hoping for more than 40,000 miles :D

[theman53]

The way I understand it is that when the throttle plate shuts or the opening decreases suddenly and air demand decreases suddenly, the mass en transit has to stop, it's just air but there's mass to it, so then there's a reverse wave that travels backwards and acts against the compressor wheel in the opposite direction where the impact can cause serious mechanical damage. It's at that point, when the manifold pressure is relatively low and the charge delivery piping is still holding a relatively higher pressure, at that point is when you want to release that pressure, and it's that momentary pressure differential that drives the system tuning and determines the spring rate.

During steady state operation the pressure differential across the blow off valve diaphragm/piston should be pretty close to zero. But when the manifold pressure (the engine side of the throttle plate, compared to the rest of the system) is lower and the charge delivery piping is still higher, then the differential pressure across the blow off valve increases. It's that differential pressure increase that the spring is acting against. Increasing the spring rate increases the amount of differential pressure that can be tolerated before the blow off valve operates. Otherwise the pressure on either side of the blow off diaphragm/piston should be nearly equal and the valve stays shut.

[theman53]

That ^ is more of a gasser response, but to add to Rabbit Jockey *Travis* I think it would work using E.xhaust M.anifold P.ressure and the normal boost pressure that a BOV sees. Is this what you are talking about Libby?

[RabbitJockey]

also from talking to josh more, he says he never had this issue and he was running the straight mercedes t3 with the mercedes turbine wheel and .48 exhaust housing

but he also had a fmic with lots of piping just like your car, and he had even run much more boost psi.  you guys had very similar engines but his has survived many dyno sessions and 1/4 runs, at higher boost levels.

[theman53]

call me if you want.

[theman53]

Found this on another site and it makes sense to not need it...

Turbo bark isn't a huge problem, the engine on the other end is still consuming air and it's not until the turbo slows beyond the surge point for that pressure that the air can blow back through. It's nothing like slamming a throttle plate shut on a petrol. Some modern engines use the EGR valve to vent intake pressure to the exhaust with a rapid dumping of load, probably more for consumer perception than turbo life.

[RabbitJockey]

The thing that raises my eye brow is that it happened in only 100 miless of driving and at only 15psi.

Also josh having a similar engine with nearly twice the boost and no issue.

I mean i want to agree with the turbo builder but those 2 things contradict what he has said imo

Although what he did say makes sense

[8v-of-fury]

So I run 15-20 on my k03.. in which the waste-gate does not function as it never gets that high..

I spin this turbo probably at a higher turbine RPM than you guys are spinning your larger turbo's at, Why do I have no turbo bark at all? I can go from hard accel to nothing like not even decel.. clutch in and back to idle.

I heard a VNT mk4 the other day that had MASSIVE turbo bark from an idle-up throttle blip even.. wth?

[RabbitJockey]

For one u have no intercooler or related piping so not much volume for the gasses to build and store up pressure, and for 2 u have a tiny turbo with a tiny inducer so it has hard for the air to back out that inducer

[libbydiesel]

How about a simple check valve between the intake mani and exhaust mani that would allow air to flow to the exhaust when the pressure in the intake was higher, but stop exhaust from moving to the intake?

[745 turbogreasel]

I must be in trouble, my automatic Dodge who's only mod is a short exhaust pipe  barks like an angry dog every time  you are under load, and let off.
I assume it has done it the last 210,000 miles.  I'd estimate the intercooler holds about 2 gallons.

[theman53]

nother theory...at 15psi I was venting tons through the wastegate as it probably had 30+ worth of drive. When I let off the wastegate was dumping the  drive pressure so there was not much left, then closed probably at 14.?psi but I still had all that air in the intake and not much in the exhaust. I think I would have been better off at 30psi as I would probably had 40+psi of drive pressure.

8v: I think of the k03 moving a bicycle tires worth of air and mine is moving a truck tires worth of air.

745: I don't know why I have problems and you don't. Other than this is not a stock turbo and yours probably is? I have a Mercedes 300D cold side a 45trim mounted to the VW hot side. Travis idea and mine was to have Mercedes boost with Vw spool. Maybe if the exhaust side was bigger and it took longer to make boost then the higher engine RPM would eat the boost when I let off? All guesses on my part.

[RabbitJockey]

How about a simple check valve between the intake mani and exhaust mani that would allow air to flow to the exhaust when the pressure in the intake was higher, but stop exhaust from moving to the intake?

Thats is the idea with the bov, except to have the air vent to atmosphere not the exhaust.

The only difference i can see with the dodge is that all of the holsets have anti surge compressor housings

[8v-of-fury]

8v: I think of the k03 moving a bicycle tires worth of air and mine is moving a truck tires worth of air.

I punched some numbers, and our engines should actually move nearly the same amount of air through our turbo's at the 4000-4500 RPM range and WOT (roughly 240-245 CFM). I will need 3 less psi as well because of the larger displacement.

[745 turbogreasel]

Any idea how many times the nut had been on and off?

[theman53]

No idea how many times the nut was on and off. New wheel and nut and shaft so all hopefully will be better.

I am tapping the ex. mani. for a copper line and running it to a 100psi gauge. I don't care how accurate it is I am going to try and see how fast it is losing EMP. If it is pretty constant then I will just run it. If it falls very rapidly I will add the BOV.