Fluttering?
07-31-2003, 06:01 PM
#16
Administrator
Thread Starter
Re:Fluttering?
Here is DonM's reply to me in the high perf section.
Monty,
Compressor surge and bark are not the same thing. You are experiencing surge or a tractive loss of grip on the air.
The turbo is not able to grab the air, hence the flutter or surge you hear. Another way to say it would be compressor slip. It is slipping through the air or partially so. Air is a fluid. That being said think of a boat prop that cant grab the water or your hand having a problem grabbing a handful of water. Same thing. This happens on some compressors when the CFM damand is high and the boost pressure is low
Monty,
Compressor surge and bark are not the same thing. You are experiencing surge or a tractive loss of grip on the air.
The turbo is not able to grab the air, hence the flutter or surge you hear. Another way to say it would be compressor slip. It is slipping through the air or partially so. Air is a fluid. That being said think of a boat prop that cant grab the water or your hand having a problem grabbing a handful of water. Same thing. This happens on some compressors when the CFM damand is high and the boost pressure is low
08-03-2003, 05:51 PM
#17
Adminstrator-ess
Re:Fluttering?
Here's the reply I got from High Tech Turbo:
Hi Dave,
Yes, you do have the turbo I thought you had. The surge won't hurt anything.
it is simply cavitating to some degree. It is normal for some setups. But if
you wanted to go with a ported housing and larger wheel it might help you out.
There is a way to go ported with the same size wheel but if you have more fuel
than stock then the stage I upgrade might be just right for you. But it sounds
like an upgrade to an HX35/40W hybrid might be best for you in the long run if
you add lots of fuel. Just let us know what you think you want and when you
want it and we'll set you up.
Paul
High Tech Turbo
I'm going to stop worrying about it and just drive. ;D
Hi Dave,
Yes, you do have the turbo I thought you had. The surge won't hurt anything.
it is simply cavitating to some degree. It is normal for some setups. But if
you wanted to go with a ported housing and larger wheel it might help you out.
There is a way to go ported with the same size wheel but if you have more fuel
than stock then the stage I upgrade might be just right for you. But it sounds
like an upgrade to an HX35/40W hybrid might be best for you in the long run if
you add lots of fuel. Just let us know what you think you want and when you
want it and we'll set you up.
Paul
High Tech Turbo
I'm going to stop worrying about it and just drive. ;D
08-05-2003, 10:52 AM
#20
Registered User
Re:Fluttering?
Funny -- I got a fast response from HTT too . . . but Don M over on the high perf board is maybe talkin' me out of the cheap compressor upgrade idea link.
Anyway HTT has a couple different new wheel and housing combinations that would work and have map width slots -- they range $150 to $225 US.
Did you call 'em some kind of name? Or just tell 'em they want too much money for their 16cm housings?
Alec
Anyway HTT has a couple different new wheel and housing combinations that would work and have map width slots -- they range $150 to $225 US.
Did you call 'em some kind of name? Or just tell 'em they want too much money for their 16cm housings?
Alec
08-06-2003, 12:14 PM
#21
Chapter President
Re:Fluttering?
Holy cow... NOPE... No names just said that a few of us on the DTR were mulling over a problem we were having with flutter(surging) of our stock turbos and wondered what they would suggest with the upgrade. Just the compressor or the whole turbo swap..Asked if they could tell from our posts what would benifit us the most..
Must be my Canuk drawl..LOL...
J-eh
08-08-2003, 10:21 AM
#22
Chapter President
Re:Fluttering?
Well my ISP must use the old postal service...LOL..
It looks like my mail didn't get to HTT till this am.. I did get a good response too with what we have discussed already about the surging/cavitating problem ..
I have a feeling Paul is tired of talking to us...LOL...
J-eh
It looks like my mail didn't get to HTT till this am.. I did get a good response too with what we have discussed already about the surging/cavitating problem ..
I have a feeling Paul is tired of talking to us...LOL...
J-eh
08-10-2003, 09:12 PM
#24
Registered User
Re:Fluttering?
I got this information from an e-bay sellor who has been consistently selling turbo housings and injectors for the past year or so after I inquired about new parts for my H1 or a new Hx35 cartridge . . . Doesn't quite jibe with the impresiion that I got from Don M . . .
"The H1 and the HX turbos use the exact same wheel contours and exact same compressor maps. The difference in the two turbos is that to save money, they moved away from the H1 to the HX, which has fewer parts and is easier to build on an assembly line because it is put together on the back plate and compressor housing with simple snap rings. The H1 turbo had a bolt in thrust bearing, bolt on back plate, and an o-ring and v-band connection on the compressor cover to back plate. The H1 is a better turbo and given identical inducer sizes, performs every bit as good as the HX, in fact identical."
Also, in regard to my surgeing problem: "It still sounds like an intake restriction to me". Well, I have been meaning to put that filter minder on the truck -- maybe the K&N is just a little too restrictive as I get close to the edge of the compressor map?? Wouldn't that be interesting . . .
Anybody have any other info?
Alec
"The H1 and the HX turbos use the exact same wheel contours and exact same compressor maps. The difference in the two turbos is that to save money, they moved away from the H1 to the HX, which has fewer parts and is easier to build on an assembly line because it is put together on the back plate and compressor housing with simple snap rings. The H1 turbo had a bolt in thrust bearing, bolt on back plate, and an o-ring and v-band connection on the compressor cover to back plate. The H1 is a better turbo and given identical inducer sizes, performs every bit as good as the HX, in fact identical."
Also, in regard to my surgeing problem: "It still sounds like an intake restriction to me". Well, I have been meaning to put that filter minder on the truck -- maybe the K&N is just a little too restrictive as I get close to the edge of the compressor map?? Wouldn't that be interesting . . .
Anybody have any other info?
Alec
08-11-2003, 03:53 PM
#25
Adminstrator-ess
Re:Fluttering?
Alec-
Mine surged with NO air filter, Bill @ Heath wanted me to test it to see if it was an intake noise. My BHAF has less that 2000 miles on it, so I doubt it's a restriction. The K&N probably isn't a restriction, but unless you've swiss-cheesed the filter box, that little tiny inlet duct might be a choke point.
I'm not ready to chuck the H1 yet, either. I'm going to try playing with the pump settings to see if I can restrict the low RPM fueling enough to get rid of the surge without killing the low end torque. Just set the smoke screw to no preload, haven't played with the star wheel yet. I'll keep you posted.
Mine surged with NO air filter, Bill @ Heath wanted me to test it to see if it was an intake noise. My BHAF has less that 2000 miles on it, so I doubt it's a restriction. The K&N probably isn't a restriction, but unless you've swiss-cheesed the filter box, that little tiny inlet duct might be a choke point.
I'm not ready to chuck the H1 yet, either. I'm going to try playing with the pump settings to see if I can restrict the low RPM fueling enough to get rid of the surge without killing the low end torque. Just set the smoke screw to no preload, haven't played with the star wheel yet. I'll keep you posted.
08-11-2003, 06:28 PM
#26
Registered User
Join Date: Oct 2002
Location: Mountain View, CA
Posts: 187
Likes: 0
Received 0 Likes
on
0 Posts
Re:Fluttering?
My H1C surged like mad after the PODs and the tranny work. I picked up a used HX35 cheap and that cleared it up. I can tell from first hand experience the HX35 spools better than the H1C and it seems to flow a little more air.
Jay
Jay
08-11-2003, 08:28 PM
#27
Registered User
Join Date: Sep 2002
Location: Birmingham, Al.
Posts: 315
Likes: 0
Received 0 Likes
on
0 Posts
Re:Fluttering?
What I would like for someone to explain is from what DonM said in the post, that it was like cavitation. The pumps we supply use WATER to PUMP AIR, in a cavitation state, the air is imploding on it's self and "eats" away at the metal of the "impellor" , we call it a rotor, this kinda looks like termites that can eat IRON, but it will mess up a rotor in short time, as some of our medical pumps only have .0015 clearance. If the pump is operating with a cool water temp and high air inlet temp, then we get cavitation, kinda sounds like marbles rolling around inside, centrifugal pumps will also cavitate if the inlet is restricted, but sounds even worse.
So back to my question, how can a compressor such as a turbo cavitate. If the inlet is restricted, the turbo should slow down accordingly due to lose of air flow???, if it maintained or continued building rpms with a lose of inlet air flow, then I could see a cavitation state.
Just a dummy wanting to learn asking another dummy question.
So back to my question, how can a compressor such as a turbo cavitate. If the inlet is restricted, the turbo should slow down accordingly due to lose of air flow???, if it maintained or continued building rpms with a lose of inlet air flow, then I could see a cavitation state.
Just a dummy wanting to learn asking another dummy question.
08-11-2003, 08:46 PM
#28
Adminstrator-ess
Re:Fluttering?
Alec-
Smoke screw at no preload made a noticeable difference. I can still make it surge if I try, but for most driving it doesn't do it. I guess the best way to put it is it's less sensitive. The truck isn't quite as snappy as it was with the smoke screw turned up, but it still spools up quick enough for me, and it's nice not to have to drive like I have an egg under my foot at low RPM in 4th and 5th.
I was able to almost completely eliminate the surge (would only do it in 5th around 45 at WOT) by turning the star wheel counterclockwise nearly to the top, but it spooled way too slow and actually lost overall power (probably couldn't make enough boost to get full fuel). For now, I have the star wheel back where it was when I opened the pump and the smoke screw at no preload. I'm wondering if maybe a very stiff star wheel setting and turning the smoke screw in all the way would cure it. Would be very smoky off the line, though.
Smoke screw at no preload made a noticeable difference. I can still make it surge if I try, but for most driving it doesn't do it. I guess the best way to put it is it's less sensitive. The truck isn't quite as snappy as it was with the smoke screw turned up, but it still spools up quick enough for me, and it's nice not to have to drive like I have an egg under my foot at low RPM in 4th and 5th.
I was able to almost completely eliminate the surge (would only do it in 5th around 45 at WOT) by turning the star wheel counterclockwise nearly to the top, but it spooled way too slow and actually lost overall power (probably couldn't make enough boost to get full fuel). For now, I have the star wheel back where it was when I opened the pump and the smoke screw at no preload. I'm wondering if maybe a very stiff star wheel setting and turning the smoke screw in all the way would cure it. Would be very smoky off the line, though.
08-12-2003, 08:33 AM
#29
Registered User
Re:Fluttering?
Please note I AM NOT AN EXPERT in fluid dynamics, but I think this is the basic gist of the matter.
A turbine compressor, and indeed any centrifugal pump, works by accelerating the mass of the medium it is pumping.
If you block off the outlet of these pumps so that the flow of the medium stops, the inducer (wheel) will become loaded with the medium, but the medium will have no place to go, so instead of being able to pump the medium, the loaded wheel will just start spinning as a solid unit. This happens in a turbocharger when the inertia of the mass of the air in the inducer can no longer overcome the pressure in the intake manifold -- at this point the turbine speed INCREASES very rapidly, because instead of transferring energy into a flow of air, it only can transfer energy into speeding up the loaded compressor wheel. Eventually the inducer spins fast enough that the inertia (centrifugal force) can overcome the head pressure, at which point energy starts being transferred into air flow, rapidly slowing the turbine . . . the change between these two states is the "flutter" problem we are having.
Because the turbos are working on a gas, if the inlet is restricted, it affects the mass of the air charge (really the density of the air) in the compressor -- which is why it is the pressure ratio that is important, not the absolute pressure. The turbo can support a given pressure ratio between inlet and outlet at a specif mass flow of air. Lower the inlet pressure, and you lower the outlet pressure that can be supported without surging.
Cavitation occurs with liquid media when the inertia of the media creates an outlet flow that is greater then the inlet pressure can support. The media is discharged from the impeller, drawing a sort of vacuum behind it (I think that suspended gasses, etc. actually come out of the medium and fill that space, etc., but the area is under very low pressure) forming little pockets along the impeller -- these little pockets are formed and collapse chaotically, causing very rapid erosion of the impeller surface.
As for setting the pump to get rid of the problem: I am glad that you found a compromise setting that makes it easier to drive. The problem as I see it is, though, that it is really a matter of reducing fuel at rpms below about 1700, which reduces torque below that speed, and effects a type of drivability that I want.
As for the H1 & Hx35 differences, the Hx35's on the later trucks have a different inducer and scroll housing from the early trucks, and may even have map width enhancement slots. If my supplier was correct, an H1 set up with the same exhaust housing, inducer, and compressor scroll would perform identically to an Hx35 with the same specs.
So that is what I have been able to gather so far -- still looking for more information, improvements, or corrections, though.
Alec
A turbine compressor, and indeed any centrifugal pump, works by accelerating the mass of the medium it is pumping.
If you block off the outlet of these pumps so that the flow of the medium stops, the inducer (wheel) will become loaded with the medium, but the medium will have no place to go, so instead of being able to pump the medium, the loaded wheel will just start spinning as a solid unit. This happens in a turbocharger when the inertia of the mass of the air in the inducer can no longer overcome the pressure in the intake manifold -- at this point the turbine speed INCREASES very rapidly, because instead of transferring energy into a flow of air, it only can transfer energy into speeding up the loaded compressor wheel. Eventually the inducer spins fast enough that the inertia (centrifugal force) can overcome the head pressure, at which point energy starts being transferred into air flow, rapidly slowing the turbine . . . the change between these two states is the "flutter" problem we are having.
Because the turbos are working on a gas, if the inlet is restricted, it affects the mass of the air charge (really the density of the air) in the compressor -- which is why it is the pressure ratio that is important, not the absolute pressure. The turbo can support a given pressure ratio between inlet and outlet at a specif mass flow of air. Lower the inlet pressure, and you lower the outlet pressure that can be supported without surging.
Cavitation occurs with liquid media when the inertia of the media creates an outlet flow that is greater then the inlet pressure can support. The media is discharged from the impeller, drawing a sort of vacuum behind it (I think that suspended gasses, etc. actually come out of the medium and fill that space, etc., but the area is under very low pressure) forming little pockets along the impeller -- these little pockets are formed and collapse chaotically, causing very rapid erosion of the impeller surface.
As for setting the pump to get rid of the problem: I am glad that you found a compromise setting that makes it easier to drive. The problem as I see it is, though, that it is really a matter of reducing fuel at rpms below about 1700, which reduces torque below that speed, and effects a type of drivability that I want.
As for the H1 & Hx35 differences, the Hx35's on the later trucks have a different inducer and scroll housing from the early trucks, and may even have map width enhancement slots. If my supplier was correct, an H1 set up with the same exhaust housing, inducer, and compressor scroll would perform identically to an Hx35 with the same specs.
So that is what I have been able to gather so far -- still looking for more information, improvements, or corrections, though.
Alec
10-13-2003, 05:11 PM
#30
Adminstrator-ess
Re:Fluttering?
Alec-
Have you done anything with your timing yet? Bumped mine up 1/16", now it's very difficult to make it flutter. I think if I could get it to 1/8" or 3/16" the flutter would go away altogether. Dang pump is hard to move, though.
Have you done anything with your timing yet? Bumped mine up 1/16", now it's very difficult to make it flutter. I think if I could get it to 1/8" or 3/16" the flutter would go away altogether. Dang pump is hard to move, though.