Turbo vs blower
11-29-2007, 01:24 PM
#71
Platinum Member
Platinum Member
Don't yell at me because I don't post but this thread is up my alley. I was AMT Diesel, we developed all kinds of things for racing diesels and our designs made it into Cummins & Navistar truck engines - turbo and supercharged(roots)
We also ran the racing engines for Super Hero/Buzzi and my own little diesel boats here in the US years ago. We developed the small hi-po diesels that were to be marketed as small Seateks/Super Hero based on Cummins B series engines (also did C's and L-10's to compete with the Seatek)
I pride myself on the shear number of engines we have blown up on the dyno - in the name of developement & testing you have to break them.
Please ask Craig or Bud from Cig/Hawk who I am, no bull.
There are so many things being said here, if you have a question ask me and I'll answer it as best I can based on our cubic dollars of experience.
Joe Gere
We also ran the racing engines for Super Hero/Buzzi and my own little diesel boats here in the US years ago. We developed the small hi-po diesels that were to be marketed as small Seateks/Super Hero based on Cummins B series engines (also did C's and L-10's to compete with the Seatek)
I pride myself on the shear number of engines we have blown up on the dyno - in the name of developement & testing you have to break them.
Please ask Craig or Bud from Cig/Hawk who I am, no bull.
There are so many things being said here, if you have a question ask me and I'll answer it as best I can based on our cubic dollars of experience.
Joe Gere
Thanks for the post, added knowledge is always welcome in my book. So Post away...............
Thanks
Jon
11-29-2007, 05:43 PM
#72
Any info would help I havent done this for 16 years or so. Trying to remember is tough with out getting out a lot of info and go through it. Have puut togeathe most of the parts I need to do turbos on my boat. Small blocks boost can range from 4 to 15 lbs or so. Planning on no more than 6 lbs to start out. Should put me in the torq range of a well built possibly short lived N/A BBC.
11-29-2007, 08:29 PM
#73
Registered
You asked for this so......
Componet wise a turbo will last must longer than the roots style blower that is on your boat engine, here are some reasons why:
1a - turbo bearings (non roller, no friction) are lubricated with engine oil presure and the oil is used to cool the bearings as well. The flow of oil takes a tremendous amount of heat off those bearings, the less heat and that fact that the turbo shaft similar toa crank shaft rides on oil and never touches metal means longer life.
1b - on your roots blowers the back bearing is a sealed roller bearing and the front are usally oil bath roller bearings. There is no way to get fresh lube or cooling to them - over time they will fail.****Please remember the roots blowers are from a 2 stroke DD that had oil galleries to feed and cool those rotor bearings. That's why you would see an old 6-71 go 15,000 hrs or more without ever touching the blower.
- like someone mentioned the amount of power and the strain on the crank to spin a blower is huge. We spent some time with the Top Fuel guys here at RacewayPark in NJ to really understand how to replace our turbos with blowers and the amount of HP that they consumer going through the traps was up near 1,000 hp. When that roots blower was in a DD it was a gear drive that didn't put any weight on the nose of the blower or drag on the crank. These things add up over time. The drag the blower makes verus the gains for us on the diesel just made no sense, plus the boost psi was not high enough. In our race engines we could hit 75 psi, you didn't have hose clamps and hoses on the air take side, they were machined slip connectors with O-rings and bolted together to prevent the boost from separating them.
- someone mentioned water cooled turbo houses costing power. Not at all, yes it is true that heat is what drives a turbo and a water jacketed housing could lower exhaust temps, but it's the expansion of the hot gases that is taking place before the turbo that actually drives it. If you were experiencing a cooling of exhaust gas problem you just need a smaller turbine, that's all.
- the real advantage a blower has is low rpm boost which a normal turbo set-up has trouble making. Here's the basic problem, we all now an engine is just an air pump nothing more or less. The faster it spins the more it pumps. When you compare gas rpm's (5,500) to a diesel rpm's (3,000) you can size a turbo on diesel much easy because the effective rpm range is no narrow compared to a gas engine. So, when you have a basic turbo on gas engine you ahve to size it to run at a higher rpm, thus no boost at the low end. The roots blower doesn't suffer from that.
Seatek had their version of twin turbo to overcome that low RPM power problem and we had our split housing single turbo.
Seatek used two turbos with a valve in-between the two of them. When running on one turbo you could only make so much power because your exhaust gas flow was cut in half, once exhaust back pressure was greater than boost pressure the engine runs flat, can't make 1hp more. When you open the valve the exhaust pressure dropped, the other turbo spins up and you effectively have double the air volume not double boost. This makes BIG power.
Our version worked like this. We use one large turbo with an axial divided turbine housing. When we needed low end power like getting on plane a diverted directed all the exhaust gas to the large dia side of the turbine wheel. This allowed ot to spin easier with less pressure because exhaust temps were low at lower RPM's. Again same problem as Seatek, our exhaust gas opening was restricted until yo make enough boost to open it all up and then your head snapped back!
Another huge problem with turbo engines racing offshore is as soon as you throttle back (leave the water) your exhaust temp drops like a rock and you loose so much boost, a blower stays constant it's mechanical driven, not gas temp. driven.
That problem is impossible to overcome, there are tricks to throttleing a turbo gas or diesel boat and that's why people don't like them - they are difficult to race with (at least years ago when we went in the ocean for 160 miles -LOL).
My opinion for what it's worth - if you wanted an engine to make lots of power for many hours and not run it like a race boat jumping wave to wave - a turbo engine is far superior.
If you want to run a boat the way we did, which was literally fly wave to wave a blower engine (gasoline) is so much better power wise and ease of throttling.
Bring on your re-buttals!!!!
Componet wise a turbo will last must longer than the roots style blower that is on your boat engine, here are some reasons why:
1a - turbo bearings (non roller, no friction) are lubricated with engine oil presure and the oil is used to cool the bearings as well. The flow of oil takes a tremendous amount of heat off those bearings, the less heat and that fact that the turbo shaft similar toa crank shaft rides on oil and never touches metal means longer life.
1b - on your roots blowers the back bearing is a sealed roller bearing and the front are usally oil bath roller bearings. There is no way to get fresh lube or cooling to them - over time they will fail.****Please remember the roots blowers are from a 2 stroke DD that had oil galleries to feed and cool those rotor bearings. That's why you would see an old 6-71 go 15,000 hrs or more without ever touching the blower.
- like someone mentioned the amount of power and the strain on the crank to spin a blower is huge. We spent some time with the Top Fuel guys here at RacewayPark in NJ to really understand how to replace our turbos with blowers and the amount of HP that they consumer going through the traps was up near 1,000 hp. When that roots blower was in a DD it was a gear drive that didn't put any weight on the nose of the blower or drag on the crank. These things add up over time. The drag the blower makes verus the gains for us on the diesel just made no sense, plus the boost psi was not high enough. In our race engines we could hit 75 psi, you didn't have hose clamps and hoses on the air take side, they were machined slip connectors with O-rings and bolted together to prevent the boost from separating them.
- someone mentioned water cooled turbo houses costing power. Not at all, yes it is true that heat is what drives a turbo and a water jacketed housing could lower exhaust temps, but it's the expansion of the hot gases that is taking place before the turbo that actually drives it. If you were experiencing a cooling of exhaust gas problem you just need a smaller turbine, that's all.
- the real advantage a blower has is low rpm boost which a normal turbo set-up has trouble making. Here's the basic problem, we all now an engine is just an air pump nothing more or less. The faster it spins the more it pumps. When you compare gas rpm's (5,500) to a diesel rpm's (3,000) you can size a turbo on diesel much easy because the effective rpm range is no narrow compared to a gas engine. So, when you have a basic turbo on gas engine you ahve to size it to run at a higher rpm, thus no boost at the low end. The roots blower doesn't suffer from that.
Seatek had their version of twin turbo to overcome that low RPM power problem and we had our split housing single turbo.
Seatek used two turbos with a valve in-between the two of them. When running on one turbo you could only make so much power because your exhaust gas flow was cut in half, once exhaust back pressure was greater than boost pressure the engine runs flat, can't make 1hp more. When you open the valve the exhaust pressure dropped, the other turbo spins up and you effectively have double the air volume not double boost. This makes BIG power.
Our version worked like this. We use one large turbo with an axial divided turbine housing. When we needed low end power like getting on plane a diverted directed all the exhaust gas to the large dia side of the turbine wheel. This allowed ot to spin easier with less pressure because exhaust temps were low at lower RPM's. Again same problem as Seatek, our exhaust gas opening was restricted until yo make enough boost to open it all up and then your head snapped back!
Another huge problem with turbo engines racing offshore is as soon as you throttle back (leave the water) your exhaust temp drops like a rock and you loose so much boost, a blower stays constant it's mechanical driven, not gas temp. driven.
That problem is impossible to overcome, there are tricks to throttleing a turbo gas or diesel boat and that's why people don't like them - they are difficult to race with (at least years ago when we went in the ocean for 160 miles -LOL).
My opinion for what it's worth - if you wanted an engine to make lots of power for many hours and not run it like a race boat jumping wave to wave - a turbo engine is far superior.
If you want to run a boat the way we did, which was literally fly wave to wave a blower engine (gasoline) is so much better power wise and ease of throttling.
Bring on your re-buttals!!!!
Last edited by HabanaJoe; 11-29-2007 at 09:14 PM.
11-30-2007, 03:44 PM
#77
Geronimo36
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11-30-2007, 04:07 PM
#78
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That’s all very interesting. I sure do have a lot more respect for the turbo. Hell I've got one in my F-250. The convenience of boost adjustment is really nice. Blowers just look really cool though. Here at the University of Texas we have some very large diesel generators that use big ass turbo’s on each side of the engine (twin turbo) that feed a supercharger right in the middle. That’s totally awesome forced induction.
11-30-2007, 08:28 PM
#80
Registered
- someone mentioned water cooled turbo houses costing power. Not at all, yes it is true that heat is what drives a turbo and a water jacketed housing could lower exhaust temps, but it's the expansion of the hot gases that is taking place before the turbo that actually drives it. If you were experiencing a cooling of exhaust gas problem you just need a smaller turbine, that's all.
Our version worked like this. We use one large turbo with an axial divided turbine housing. When we needed low end power like getting on plane a diverted directed all the exhaust gas to the large dia side of the turbine wheel. This allowed ot to spin easier with less pressure because exhaust temps were low at lower RPM's.
Michael
