Strange Turbo Noise

[McGivern]

I have a question to pose to everyone about a strange noise. Under load pulling my boat, when I accelerate through the 1600-2000 RMP range and 14-18 psi , I get a strange noise that I can best describe as a steam engine running fast, like a quick chuff-chuff noise. I also see that most of the time while this is happening the boost gage resonates back and forth a few psi almost like a vibration. This all started when I put in the 12cm wastegate and seemed to get worse when I put in the bleed elbow from Janetty. I am wondering if anyone out there has heard anything like this? I am leaving with my boat for a long trip in 3 days and would really like to get it figured out.

Thanks for your suggestions in advance,

Mark

 

[nascar mark]

Hi Mark,



My guess would be the waste gate is fluttering, opening then closing repeatably. But as I don't have any experience with waste gates I would ask Power Wagon for help as he has the same set up as you.



Have you tried raiseing or lowering your bleed off boost to see if things change? Your going to pull a load with a 12 cm housing? Be careful as your egt's are going to be up there.



mark

 

[CRWilliams]

Ha, another one. I have been trying to figure mine out for over a year. JFitzgerald is having the same problem. I have been trying to get mine on chassis dyno and build some boost while somebody is under the hood. I have pretty much ruled out the wastegate. Let me know if you find anything out.

 

[JFitzgerald]

??

I'm not aware of having this problem. Maybe you've confused me with someone else?

 

[CRWilliams]

OOPS, sorry JFitzgerald, you were the Getrag, MGrant was the turbo.

 

[McGivern]

Thanks guys,

I pm'd MGrant to see if he ever resolved it.



Mark

 

[Jet Tech]

Hi guys, just going thru in my mind how I would troubleshoot this. It sounds like an interesting problem. I don't have the same set up as you guys but I did have an idea. It would be nice to see the waste gate actuator while truck is on the dyno but short of that how about setting up a temporary indicator and driving the truck. I would build it from a cable and tape it to the windshield so I could see it while i drove. Just trying to help!

 

[Mgrant]

Hi Guys,

Just got done moving and found the time to add my two cents worth. I narrowed the noise down to the intake. As an experiment, I removed the BHAF and put the stock airbox back on and the noise disappeared entirely, as well as the nice turbo whine. So, I'm assuming that the noise is there all the time, but the stock airbox just muffles it and the BHAF is like having no muffler at all. Second, what could the noise be? Well, my fist thought was that we were hearing the onset of the turbine blades going supersonic, which they would at the RPM these turbos are spinning. But that doesn't explain why the noise disappears as boost and RPM climbs. The second theroy was something called a compressor stall, which means that the turbine impeller can't physically cram any more air into the intake for the amount of RPM the blades are spinning, sort of like putting your hand over the end of a hair dryer. On a jet engine, abnormal airflows will cause a similar problem of the air piling up on the back end of the compressor while the forward part can't bite off enough air to keep the airflow going, resulting in a drop in pressure in the combustion chamber, a flameout, and unburnt fuel exiting the turbine. Pretty flames and a loud whoop-BANG! In our diesels, the air will rush back out the turbine blades until an intake valve opens, relieving boost and allowing normal airflow again, hence the cho-cho sound. So, the air will go back and forth within the turbine blades until the turbo or engine increases RPM, allowing more boost or airflow. I'm thinking that a way around this would be to install a Banks Twin Ram intake, allowing more airflow, less restrictive boost build-up and relieving the compressor stall. Bigger intercooler lines would help as well. Also, maybe a turbo with an upgraded or hybrid compressor will work, Piers Super Turbo comes to mind. But for now, I know what it is and as long as the EGTs are acceptable and the brand-Xs are in the rearview mirror, I won't pay any mind to it. Mine does it at about 1200 RPM and at 12-15 psi boost, so if I'm towing and I hear it, it reminds me that I should take it out of 5th anyway.



Mike

 

[mark93]

Mine does this too.



It occurs with full throttle at around full torque rpm and will remain present until rpms get out of the critical range. After my Banks Intercooler was installed it seems to occur at higher rpm. As Mike says, it has to do with the turbocharger's "performance map". I do not believe it is harmful at all.

 

[McGivern]

solved- hopefully

Problem should be solved. I understand the earlier H1C's like on my '92 experienced separation of airflow on the compmressor wheel when you run much higher than stock boost.

I have on the way a later version compressor housing which has relief veins machined in the housing. I should have it installed in a week or so and can file a report on the results.



I got the answer by calling Piers - he knew exactly what was happening and told me about the later version H1C. He was so sure that this would solve the problem that he offered me a full refund if the solution didn't work - you can't beat that. He was a genuine pleasure to talk to and really knows his stuff.





Mark

 

[Old Smoky]

I am currently running 28psi and hear no noise like you guys are describing. All I hear is turbo whine. Maybe I am just missing it?



Mike

 

[CRWilliams]

Hey guys, check this out. I was looking for an HX 35 on e-bay and found this. Seems like probably just what we need to cure the problems. McGivern, I wonder if this is similar to what you are getting? The price doesn't sound bad, I may try it. Have to check my finances.



http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1864314106

 

[McGivern]

That is probably the one - you want to make sure there are relief grooves in the housing where the compressor blades ride.



One note, if you buy that one you'll have to get your turbo re-balanced, and I don't know what that will cost. Piers sold me the whole turbo, less the exhaust housing for less delivered. This way I just leave my exhaust housing mounted in the truck and swap cartridges - no balancing required. I should get it early next week, and I'll post the results.



Smoky - IF you had this condition happening, you'd defintiely hear it!



Mark

 

[McGivern]

I installed the HX35 that Piers sent me last night.



What a difference!!!!!!!!



3 more pounds of boost, quicker spool-up, and 50-100 deg EGT drop across the board! Best of all, no more pressure cooker noise.



My advice is for any first gen guys running a W. G. 12 cm , start looking for an HX35 cheap and sell you H1C.



Mark

 

[Mgrant]

You're right Mark! Piers sold me a HX35 and that did the trick. Top end boost seems to be about a pound more, but a LOT more low end boost. I guess the low speed fluttering on the H1C was causing some inefficiency. Also, talk about whine! Sounds like a PT6 spooling up! Can't imagine why the 2nd gen people want to take the silencer ring out. And all thumbs up for Piers! When the $$ start flowing again, the HX35 will get Piersified!



Mike

 

[McGivern]

Mike,



I am very happy you are similarly pleased. Yes, I too love the sound! Anyway, glad I was able to help out. I just found out there will be an articel in the next TDR about my crew cab conversion; watch for it.



If you have Piers do his thing to your turbo, please PM me and tell me about it. My next project will be EGR brakes on all 4 corners.



Take care buddy,



Mark

 

[JFitzgerald]

Originally posted by McGivern

Mike,



I just found out there will be an articel in the next TDR about my crew cab conversion; watch for it.

Congrats on that, Mark! Can't wait to see the article.