Excessive boost pressure / wastegate sticking closed

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

ramhunter9

Senior Member
Joined
Jun 25, 2010
Posts
24,464
Reaction score
974
Ram Year
2012
Engine
P-Star Jeep Wrangler
DIY on waste gate inspection
 

Mopar1973Man

Senior Member
Joined
Aug 22, 2011
Posts
825
Reaction score
21
Location
New Meadows, Idaho
Ram Year
1996, 2002
Engine
1996 Dodge 1500 (V8-5.9L) & 2002 Dodge Ram 2500 (5.9L Cummins)
DIY on waste gate inspection

LOL... Just read your PM to me and figured your going to ask that question... Ugh!

Well the best I can do shooting from the hip. First off we would need to figure out if you got a HX35 or HY35. HX35's are all the manual transmssion trucks where the Hy35's are on all the automatics. Ok for the HX35's there are easy to test wastegate function by disconnecting the rubber hose on the wategate elbow and applying air pressure to the hose 20-25 PSI and you should see the wategate arm move. As for the HY35's they have a hardline from the turbo to the wastegate motor so you can't do this test. Instead you remove the turbo and remove the exhaust cover for the turbine there you'll find the wastegate and turbine. At this point you'll be disconnecting the wastegate rod from the turbo and then phyiscally try moving the wastegate open and close with your fingers. If its frozen then you would use WD40 or simular to free the wastegate again. All you got to do is reassembly the utrbo and reinstall on the engine.
 

KGBIGCOUNTRY

Senior Member
Joined
Jun 29, 2010
Posts
13,309
Reaction score
474
Location
MECH, VA
Ram Year
2004 RCSB/2005 QCSB
Engine
5.7 / 5.7
Good info, are the wastegates know for failure?
 
OP
OP
ramhunter9

ramhunter9

Senior Member
Joined
Jun 25, 2010
Posts
24,464
Reaction score
974
Ram Year
2012
Engine
P-Star Jeep Wrangler
Hy35 , no code and I found the issue .. my programer was on #10 setting giving me 45psi in boost . After further review I found non stock injectors and the waste gate works properly .
 

RubberFrog

Senior Member
Joined
Jun 26, 2010
Posts
5,727
Reaction score
334
Location
Arizona
Ram Year
2019
Engine
6.4
I don't know what that **** means, but it sounds good!

[yt]pBaqJj4aPDY[/yt]
 

Mopar1973Man

Senior Member
Joined
Aug 22, 2011
Posts
825
Reaction score
21
Location
New Meadows, Idaho
Ram Year
1996, 2002
Engine
1996 Dodge 1500 (V8-5.9L) & 2002 Dodge Ram 2500 (5.9L Cummins)
Hy35 , no code and I found the issue .. my programer was on #10 setting giving me 45psi in boost . After further review I found non stock injectors and the waste gate works properly .

OK... The HY35 turbo is limited to 30-32 PSI of boost. As for the programmer it will kill off the P0234 error code because of the programmer ability to boost fool. So the ECM never sees above 20 PSI so the error code is never tripped.

Hmmm... I honest suggestion... Upgrade at least to HX35 turbo...

HY35 is a 9cm2 exhaust housing... HX35 is 12cm2 exhaust housing...

So the HX35 will spool a bit later and have more lag but EGT's will be much lower. Might actually see a increase in HP too. Just remember all the P7100 12V's had HX35's on both auto and manual trucks. It was in the 24V trucks that switch the auto's over to HY35 for smog reasons.

I don't know what that **** means, but it sounds good!

Stick around you might learn something... Ask question I'l answer it to the best of my abilities...
 
OP
OP
ramhunter9

ramhunter9

Senior Member
Joined
Jun 25, 2010
Posts
24,464
Reaction score
974
Ram Year
2012
Engine
P-Star Jeep Wrangler
Thanks Michael
 

dripley

Member
Joined
Aug 23, 2011
Posts
75
Reaction score
0
Location
hickory, nc
Ram Year
2002 2500 ho 6 speed 4X4
Engine
5.9 24v cummins
OK... The HY35 turbo is limited to 30-32 PSI of boost. As for the programmer it will kill off the P0234 error code because of the programmer ability to boost fool. So the ECM never sees above 20 PSI so the error code is never tripped.

Hmmm... I honest suggestion... Upgrade at least to HX35 turbo...

HY35 is a 9cm2 exhaust housing... HX35 is 12cm2 exhaust housing...

So the HX35 will spool a bit later and have more lag but EGT's will be much lower. Might actually see a increase in HP too. Just remember all the P7100 12V's had HX35's on both auto and manual trucks. It was in the 24V trucks that switch the auto's over to HY35 for smog reasons.



Stick around you might learn something... Ask question I'l answer it to the best of my abilities...

please explain the 9cm2 and the 12cm2. the 9 and 12 cetemeter is the opening in the outlet of the turb i believe. what is the 2? maybe a new thread.
 

Mopar1973Man

Senior Member
Joined
Aug 22, 2011
Posts
825
Reaction score
21
Location
New Meadows, Idaho
Ram Year
1996, 2002
Engine
1996 Dodge 1500 (V8-5.9L) & 2002 Dodge Ram 2500 (5.9L Cummins)
please explain the 9cm2 and the 12cm2. the 9 and 12 cetemeter is the opening in the outlet of the turb i believe. what is the 2? maybe a new thread.

Yes... Your right is 9cm square opening or a 12cm square opening...

Smaller the opening the quicker the turbo will spool with less lag but the faster it will climb in EGT's and hit a choke point early. With a larger opening there is more lag but EGT climb slower and the choke point is higher.

Choke Point...

Choke point is when you drive pressure (exhaust pressure entering the turbo) climbs higher than the boost pressure (leaving the turbo). Once this occurs the turbo is compressing more and working harder to push more air into the engine than what can leave so the air starts to heat up.

So now coming back around and using RamHunter9 as a example he's got a HY35 turbo with 9cm2 exhaust housing so that makes his max boost pressure about 30-32 PSI for choke point so exceeding this just creates a hot charge of air for the engine (performance lost!) Because the engine has to pump the exhaust through the small housing.

So now you can see why high performance guy look for large single turbos or compound twins because the can create more boost pressure but still have very large exhaust hole to pump out of.

Now you crossing a boundary... (Drivability / Performance) more Later...
 
OP
OP
ramhunter9

ramhunter9

Senior Member
Joined
Jun 25, 2010
Posts
24,464
Reaction score
974
Ram Year
2012
Engine
P-Star Jeep Wrangler
So the more air in and more out the better ?
 

Mopar1973Man

Senior Member
Joined
Aug 22, 2011
Posts
825
Reaction score
21
Location
New Meadows, Idaho
Ram Year
1996, 2002
Engine
1996 Dodge 1500 (V8-5.9L) & 2002 Dodge Ram 2500 (5.9L Cummins)
So the more air in and more out the better ?

Yes and No...

Yes for performance because the larger housing allows it to breathe better. But No because driviiblity and emissions on a large housing is really laggy ans moke going from light to light. So there is a balance that has to be mantained. Too big and you got a laggy and smokey truck and too small and now you got EGT's problems hauling heavy loads.
 
OP
OP
ramhunter9

ramhunter9

Senior Member
Joined
Jun 25, 2010
Posts
24,464
Reaction score
974
Ram Year
2012
Engine
P-Star Jeep Wrangler
Ugh ... you need to do some experimenting for us ..lol
 

Mopar1973Man

Senior Member
Joined
Aug 22, 2011
Posts
825
Reaction score
21
Location
New Meadows, Idaho
Ram Year
1996, 2002
Engine
1996 Dodge 1500 (V8-5.9L) & 2002 Dodge Ram 2500 (5.9L Cummins)
More on turbo exhaust sizing...
How does a turbo work?

VOLUMETRIC EFFICIENCY AND BACKPRESSURE
Although the turbine recovers wasted exhaust gas energy from the expansion of the hot exhaust gas, the kinetic energy of the flowing exhaust gas and the acoustic energy of the exhaust gas, the working turbine also causes an increase in exhaust gas backpressure. This increase in backpressure can reduce the engine's volumetric efficiency.

A typical, streetable turbo system has more exhaust backpressure than boost pressure and the power gains from such systems are due to the increase in the density of the intake charger, not due to increases in volumetric efficiency. (Volumetric efficiency, if you don't remember, is the volume of intake charge inhaled during the intake stroke vs. the actual displacement of the cylinder. VE is expressed as a percentage; the larger the VE, the better.)

Backpressure is higher than boost pressure because the smaller turbine housings and turbine wheels used to ensure a quick spool-up time also, by nature, restrict the exhaust flow. We will explain the mechanics of this in more detail a little later. Racing turbos, the latest generation of medium-sized turbos and turbochargers for engines where throttle response is not much of an issue (like fixed industrial engines, long haul trucks and aircraft), have free-flowing turbines that have less exhaust pressure than intake pressure. Engines using these turbos often do have improved volumetric efficiency.

This condition, where boost is higher than backpressure, is called crossover and crossover is what ever turbo system designer strives for. In crossover, VE percentages as high as 110 percent are not unheard of. Unfortunately, some of the design features that can create a free-flowing turbo can also contribute to turbo lag, something that is not desirable in a street-driven car that needs a wide dynamic power band.

Excessive backpressure is hard to manage in a boosted four-stroke engine. Excess backpressure causes what is known as reversion. Reversion is when hot exhaust gas gets pumped backwards into the engine during the overlap period. Reversion can cause the engines internals to get excessively hot as cross flow of the cool intake charge during overlap is one of the ways an engine cools its self internally. Hot internal parts can trigger uncontrolled combustion and engine-destroying detonation. Because of this, it is sometimes not a good idea to really crank the boost on an engine that has a small, high-backpressure turbo - in other words, the kind of turbo that usually comes on a factory turbo car. This is a good reason not to go crazy with a boost controller on a factory-equipped turbo car. A little more boost, perhaps 4 to 5 psi might be tolerated, but trying for 20psi could be flirting with disaster.

On small turbo cars with a lot of backpressure, camshaft overlap should be kept to a minimum. This means that the stock cam usually will work best. To deal with the problems associated with backpressure and reversion, the engine's tuning must also be compromised with richer mixtures and more ******** timing than what would normally be optimal for the best power. Even on full race turbocharged cars with low backpressure turbos, camshaft overlap should be several degrees less with more lobe separation angle than on an equivalent naturally aspirated engine, unless physical measurements indicate that the engine is in crossover in the engine's operational range.

Because of backpressure and VE issues, the correct turbo size for the application is very important when designing a turbo system. A small, quick-spooling turbo can be restrictive, causing a great deal of backpressure and reducing VE at higher rpm. This means that small turbos should be limited to lower boost levels. A big, free-flowing turbo can be laggy and unresponsive, making it unpleasant for street driving but producing awesome power at higher rpm.

To combat high backpressure and possible reversion, the compromised tuning needed to prevent destruction with an overboosted small turbo will also reduce power. If a small turbocharger is running backpressure to boost ratio of more than about 1.8:1, a supercharger has a good chance of performing better. Fortunately, it is easy to design a reasonable responsive, powerful turbo system with a ratio of less than this.
 
Top