70Stang

iTrader: (2)

We recently have had 2 turbo failures due to bad or slow reacting blow off valves. One car had an old BOV that just stuck shut - it killed a turbo in 1 hour.

The second car had a Tial 50 hooked to a slow responding vacuum source. It worked, but was slow to open. You could rev the motor, hear it surge 2-3 times and then see the BOV open.

This the what it did to the inside of the turbo from all the compressor surge -









The result was an obvious lack of power and heavy smoking out the exhaust.


So, today or whenever you get a chance, go outside, pop your hood and watch your blow off valve. It should open as soon as the motor comes off a quick rev and should be fluttering at idle.

If you here any surge try a couple of things before buying a new BOV.

Check the vacuum line going to the BOV and make sure it isn't crimped, but or in a bad location.

Spray some lube on the actual valve and see if it reacts quicker.

Adjust the hardness/softness of the BOV and see if it helps.

Replace a stiff spring with a softer one (11psi to 9 or 7)


If none of that helps and you still suffer from surge, it is time to start looking for a new blow off valve before you have to buy a turbo!

Zombie

iTrader: (2)

I don't think surge would cause your turbo to fail in one hour. Some cars come from the factory without BOV's.

Thank you very much for learning how to use your camera for taking macro pictures!

70Stang

iTrader: (2)

Yeah, you wouldn't think it - but it did.

These pictures are from a YEAR of surge, not an hour. The other turbo was barely hurt, but on its way....20-30 runs on the dyno at 30psi with surge and no blow off valve will hurt a turbo...you dont agree?

Zombie

iTrader: (2)

What kind of surge? Is it surging while in boost or just surging when you let off? What size engine and what size turbo? Lot's of things cause turbos to go bad such as over speeding them and bad oiling or oil contamination. No diesel I know of comes with a BOV and they routinely run 30-50psi. Not saying surge can't hurt a turbo, just that I feel it's unlikely under most circumstances.

70Stang

iTrader: (2)

Right - Diesels don't have a throttle body, so the air is still headed into the motor after you let off - bad oil wouldn't cuase a thrust to wear side to side...it would hurt the bearings, but not hurt the thrust like that.

30psi on a 1.6L 67mm Turbo car... Surge was on throttle close

Reject

iTrader: (24)

how was the vac lines? like did he have alot of things usung that same vac source?

70Stang

iTrader: (2)

Well, on that turbo the vacuum lines were ok - but the source was lacking. We moved the vac line to the manifold directly and it solved the problem.

great421

iTrader: (1)

Not to hi-jack a thread... but:

As an Engineer for Volvo / Mack Trucks, I can tell you our newer (2004 and up) turbos are a variable geometry design; meaning they are designed to stay spooling at top speed and they simply adjust the amount of air that they move (less air at lower speeds, more at higher). Now, having said that "high" speed for our 16 Litre in-line 6 is 1600 - 1800 RPM!

So, given that, a BOV is not required for a turbo diesel as the PCM can modulate the volume of the turbo every 50 to 100 ms!

MIKE

MDoe8

iTrader: (3)

That's pretty badass

Stang's Bane

iTrader: (22)

VTEC for turbo's!!!!

b00sted

iTrader: (7)

Same idea as the variable vane stuff used for years?

Eddiep

iTrader: (26)

Grand Nationals / T-Types didn't have blow-off valves. I had a Turbonetics T-60, with no BOV for many, many years and never had a problem. Snapping the throttle shut during boost would make the car sound like a duck quacking - from the boost spike escaping back through the inlet of the turbo!

70Stang

iTrader: (2)

It is possible that some turbos are built better then others and they don't allow this to happen?


If not surge, what do you guys think caused this?

TS6

iTrader: (41)

It wasn't surge. As mentioned, many cars don't even have a BOV.

If I was gonna guess what killed the turbo's I'd say oil contamination or just poorly built turbos.

spaz1

iTrader: (9)

possibly too small of a restrictor in the oil line?

70Stang

iTrader: (2)

Someone explain to me how oil in any way could cause a side load on a thrust that would eat almost all of it out. I mean, you guys are seeing that the thrust has a huge chunk of it that has been worn away from a side to side motion, right?

SS4Matt

iTrader: (4)

i would say you are correct it was in adequate blow off valve. factory cars sometimes don't have BOV's. but that is why some turbos have the volute with the slits on it on the compressor side, it's for the surge....a friend of mine has a turbo hatch back stang. 347 R block with an ST80, and it used to have a little bosch plastic POS BOV. when the car was making around 700rwhp (mustang dyno) ~ 20'ish #s when you would snap the throttle shut you could hear the turbo shutter because the BOV was inadequate. was it bad, yes...would it live, not long....

oh and about the GN's...GN guys are not right in the head and those buzz'n half dozen don't live long anyways, i know a few of those weird-O's

Eddiep

iTrader: (26)

Sold my T-type with 147k miles, two turbos were on it during that time (stock and a T-60), never had a BOV, never had a bearing problem

Maybe the surging had a hand in his turbo problem (I'm sure it didn't help), but I doubt it was the primary cause. Probably an oiling problem as mentioned.

hellbents10

iTrader: (10)

When you start talking bigger turbos and more air flow the blow off becomes more important for the life of the turbo. bigger wheel is harder on everything.

Ponyhntr

iTrader: (9)

Put a ProCharger race valve on it... all the fast turbo guys do it.

IN FACT, Precision Turbo STOCKS them!