Turbo Back Pressure Relief System

[Alan Reagan]

TX Ram, I'll post more about how it works, soon. I'm not concerned about people knowing once I am sure it works. What I'm being cautious about is the fact that finding the parts with the right temperature/pressure specifications has made this project more difficult than I would have imagined. Most solenoids valves that operate in this temperature range require pressure to seal. Sometimes (at idle) there is no pressure. So I don't want to stick some half baked solution out there that people try on their own with bad results.

 

[KWIKKURT]

Alan, Please add my name to your list of "Very Interested"...



-- email address removed --

 

[tobaccogrower]

i need on of these bad!!!!, count me in... james...

 

[Jff24Gordn]

ok, use the TPS to activate it.

 

[Alan Reagan]

I haven't forgotten this thread. I've been trying to work out an issue with a manufacturer on the solenoid relief valve. There is a vibration issue they have experienced with diesel engines that is more of a resonance issue that can only be dealt with through a specific method of mounting with regard to placement and orientation regarding the crankshaft. We are discussing the issue now and they are going to make recommendations based on possible locations I have supplied to them. I just wanted you to know that I'm still figuring out some fundamental issues of relieving pressure on these things that if dealt with on the frontend will result in a high reliability system.

 

[RottnDogue]

Still looking forward to hearing more... .....





Darren

 

[tobaccogrower]

alen:

keep up the research and good work !!!our turbo's will love ya for it..... james... .

 

[Alan Reagan]

I will. Hopefully this is just a small bump on the dirt road of development . Fortunately, the valve manufacturer has run across this situation concerning the effects of diesel engine resonance and solenoid controlled pressure valves. So they know what questions to ask and what recommendations to make.

 

[Marco]

Alan,



I have only ONE question for you.



When can you deliver me one, and how much $$$$$ ?



Ok, Ok, it's a couple of questions!



Marco

 

[Alan Reagan]

You get the prototype for testing. Fair enough?

 

[Marco]

Beta Tester?



Sure! Sounds like I'll have some fun!



Marco

 

[Lil' Dog]

Did I miss something??

The only time the CTD should see a backrush from the intake would be if someone shutdown at full boost... It just doesn't seem justified on an engine that doesn't have a throttle plate, the engine will take the pressure as fast as you give it and the pressure in the intake manifold should drop as fast as the turbo spools down. Not trying to rain on your parade, but seems like alot of work for no real reason. Like one post said, if you have a standard and you shift, you'll lose your boost between shifts and have to worry about the lag to re-build, which is why everyone is trying these "super turbos" to reduce lag. IMHO, FWIW, this is just tail chasin.



Jason

 

[Jff24Gordn]

Lil Dog, there is no such thing as too little turbo lag.

Also the other reason is to keep it from barking. I was having some traction problems in 4th gear again the other night. When I went to let off, I let off slowly. The tires grabbed, and the engine slowed down quite a bit real fast with a lot of boost. It barked the turbo about 4 times. Sometimes you cant help it. Also, it barked real bad when I was having traction problems, and it started to get away from me. I was sitting sideways in the road facing a tree when I stopped, and the turbo barked ALOT. There was not time to let off slowly. If I was unlucky, I might have broke my shaft on one of those occasions.

 

[Alan Reagan]

We are looking to relieve the pressure when there is a sudden lift from the accelerator under high boost conditions. You are right that the engine will take it as fast as you can give it but when you've built 30-40 lbs and suddenly shut down, the air tries to go backwards. Some of the posts indicate this when they talk about having high boost, letting off and getting that sudden "whoosh" sound. Race cars with turbos use this system now but it's vacuum triggered. Even if not successful, believe me, I have learned enough about turbos, temperatures, how to calculate throuput air, intercoolers and everything else to be a great source of info. If we are successful, it will be because of lot's of unsolicited input from TDR members and manufacturer's.

 

[Lil' Dog]

Gotcha

Sounds reasonable guys. Thanks for the additional info. Hittin the clutch and dropping to idle is the same as a shut down now that I think about it. I just forget about the huge amounts of boost you guys are running, right against the edge of the turbo performance curves... LOL!!!!



I'm always learning something new here. Thanks Alan.



Jason

 

[Power Wagon]

Re: Did I miss something??

Originally posted by Lil' Dog

The only time the CTD should see a backrush from the intake would be if someone shutdown at full boost... It just doesn't seem justified on an engine that doesn't have a throttle plate, the engine will take the pressure as fast as you give it and the pressure in the intake manifold should drop as fast as the turbo spools down. Not trying to rain on your parade, but seems like alot of work for no real reason. Like one post said, if you have a standard and you shift, you'll lose your boost between shifts and have to worry about the lag to re-build, which is why everyone is trying these "super turbos" to reduce lag. IMHO, FWIW, this is just tail chasin.



Jason

When you drop the fuel going into the engine, the amount of pressure on the exhaust side falls dramatically. If there is no fuel being burned, the amount of exhaust heat and pressure driving the turbo falls to minimal, even if the RPM's are up.



If you have a big intercooler and piping between the turbo and intake, you have quite a quantity of compressed air stored, and when you let off the throttle suddenly, the air is not depleted by going through the engine before the turbo will spool down.



The backrush of air will spin the turbo backwards in extreme cases, and in all cases, the turbo will decelerate dramatically.



By dropping off the excess air in the intake area, you can reduce the lag if you are only momentarily off the throttle, as well as all the other benefits explained already...

 

[Diesel Freak]

I think the simple approach here would be a check valve at the turbo outlet



-Cliff

 

[Lil' Dog]

I know I asked for it....

Good point Mark. I haven't thought of those conditions. I guess the problem is I'm not thinkin like a drag racer, rather a trucker... We like to get 'er up easy and keep it there... Boost that is...



J

 

[fest3er]

Re: Re: Did I miss something??

Originally posted by Power Wagon

...



The backrush of air will spin the turbo backwards in extreme cases, and in all cases, the turbo will decelerate dramatically.



By dropping off the excess air in the intake area, you can reduce the lag if you are only momentarily off the throttle, as well as all the other benefits explained already...

Pondering the system, when one is accelerating at

full throttle and max boost, the pressure on the

boost side of the turbo will not change suddenly

between full throttle and no throttle.



On the other side, exhaust pressure is driving the

turbo with 40-60 PSI exhaust. This is where the

stress on the shaft originates: the shaft is, if

you will, slightly twisted. When the throttle is

released suddenly, the pressure of the exhaust is

removed and the 'twist' goes away.



The sudden removal of the 'twist' combined with

the boost pushing against the input side might be

enough to cause the shaft to back-twist and twist

a few times before equilibrium is reached.



The only real solution to broken shafts is to use

stronger shafts. However, eliminating the intake

pressure should mitigate the problem to some

degree.



It might be better to monitor exhaust drive

pressure and boost pressure. If boost is over,

say, 15 PSI *and* exhaust pressure suddenly drops

to less than, say, 1. 1 times that, open the

bleeder valve.



I would also expect that one could use a flapper

somewhere before the cooler. This would serve

two purposes. First, it would serve to maintain

boost pressure between shifts. Second, it would

minimize the air that needs to be bled off the

boost side during shifts. Of course, designing

such a flapper would not necessarily be trivial.

There are heat and mechanical factors to consider.



Food for thought.



Fest3er

 

[Vaughn MacKenzie]

Wild idea?

OK, how about this: When running high boost, the drive pressure (exhaust) side should be higher than the compressor side. SO, how about running a 2" or so pipe back from the compressor side to the outlet area of the exhaust manifold and stick a check valve in this pipe? As long as drive pressure is higher, everything works like normal. Drop off the throttle and drive pressure drops instantly, then the check valve opens and the pressurized air rushes back into the exhaust side to help support the pressure and still provide a bit of drive to the exhaust turbine. This would probably be enough to save the turbo, especially if you have air shooting back with 40-50psi helping it along, to at least keep the turbine from going backwards or having high pressure differentials. This setup would not allow exhaust to leak into the intake if the check valve is quality.



This wouldn't me a simple modificiation. Sound too far out??



Vaughn