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Turbo vs blower

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Old 11-25-2007, 11:22 PM
  #31
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or if you like roots blowers, hear is a regular old 500cid 871 blower motor... from a tractor puller, on alky!!!
http://www.youtube.com/watch?v=q621p...eature=related
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Old 11-25-2007, 11:29 PM
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Some times with turbos simple is the best....

Deisel turbos in big boats are ussually shaft driven arn't they?
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Old 11-26-2007, 12:52 AM
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Originally Posted by Chris Sunkin View Post
With many performance boaters and racers operating with huge, if not unlimited budgets and with the quality of engine builders the likes of Sterling, etc., that's not likely.
They are in the business to make money, and I doubt they see that they could charge all that much more for a turbo setup than one with a blower. There is quite a bit more R&D with a turbo system, because you not only have to work with flow dynamics, but also thermodynamics on the exhaust side. There are a lot more parts to fabricate, and systems to build such as wastegates and blowoff valves. There is a lot more trial and error getting the turbos sized properly, since they are free floating system, and the turbo manufacturers typically don't publish turbine data. Blowers are just a lot more forgiving. While I don't doubt they could build one after studying them for a while, I just don't think they are motivated.

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Old 11-26-2007, 01:10 AM
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you were asking about small block turbo engines, this is brads 355 cuin small block turbo charged. it made 750 hp on pump gas at a low boost.
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Old 11-26-2007, 03:05 AM
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Originally Posted by DonziJapan View Post
The same thing happens with turbos on an unloaded engine it doesn't register boost on the gauge. Load does not "make" boost. An unloaded engine is more volumetrically efficient than a loaded one. Which means the fuel and air flow through easier. The boost is the same between an loaded or unloaded engine its the difference in resistance that causes the difference in your boost pressure gauge readings. To further simplify what you're looking at consider this. A roots blower is a form of compressor. Take your garden variety shop compressor. It has a fixed output same rpm same piston. Run it with the valve open the pressure will never build. But close the valve and pressure will build. Either situation the output of the compressor is the same just the load has changed so the gage reading changes. Your "boost" gauge is nothing but a pressure gauge reading the air pressure in your intake manifold. The intake manifold is like the tank on your shop compressor and loading the engine equates to closing the valve on the tank. Hence the rise in pressure in the intake manifold. Now this is the fact the output of the roots blower is linear in regard to the engine rpms. The lobes on a roots blower displace a fixed amount of air each time they go around. The output is determined by how many times the lobes go around in a minute. Some blowers are driven at different ratios than the engine but still the output graph will be in a straight line just at a different angle. Again we're back to the illusion of boost on your pressure gauge.he blower doesn't achieve max boost at the lower RPM either the gauge has topped out or there is a relief valve that has opened at a preset level of boost and is dumping the excess. In fact the blower is putting out more boost as the rpms rise than your boost gauge is telling you.
I think we're mostly on the same page and I see what you are saying, but it seems you are referring to actual air volume pushed through the blower and not boost pressures. I agree that the actual airflow volume is greatest at the highest rpm. Actual air flow and boost pressure are not the same thing. Air flow is affected by rpms and boost pressure is affected by engine load. Achieving max boost pressure is what increases the dynamic compression in the cylinder.
You can change the boost pressures on an engine without changing anything on the blower. Increase the flow of the heads and add more free flowing exhaust and boost pressure will drop. Actual volume being pushed through the blower will remain the same.

The boost gauge reads correctly and is not topped out. I agree, its measuring the boost pressure in the intake but its also measuring the pounds of pressure forcing the intake charge into into the cylinders.
There is no relief valve or waste gate on the supercharger or intake.
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Old 11-26-2007, 10:13 AM
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In answer to the original question, turbos are easier on parts than blowers. I have been running twin turbo engine configurations for over 10 years and consistently get more time between rebuilds than my blower loving friends.
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Old 11-26-2007, 12:20 PM
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I have ran my turbo engines for 5 years at 1800 hp and they have the same cranks, rods, pistons, valves, blocks, ect. times 2. that they were built with. only did normal maintenance oil changes and valve springs, lifters, gaskets ect.

We are willing to build them and stand behind them like I said.
Tyson, How many RPM's are you spinning to achieve 1800hp. ? Also what octane fuel are you running for that kinda power?

Nice work !
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Old 11-26-2007, 02:56 PM
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Pretty low RPM, that is one reason my engines have lasted. we usually only turn them in the 4000 rpm range but I have over 1100 hp at 4k. I run 110 octane fuel. I will admit that the 1800 hp was at around 20 lbs of boost on a 9.5-1 engine.

I tell people that my engines made 2000 hp because we ran the texoma run and the shootout at 25 lbs of boost but we never dynoed them with that high of boost. kind of scarry when all that tubing we made to dyno them kept shooting off the engine.
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Last edited by BigSilverCat; 11-26-2007 at 03:11 PM. Reason: forgot to put octane
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Old 11-26-2007, 03:10 PM
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Good thread....shows how much mis-conception/ mis-understanding there is about what effects hp, boost, rpms, etc. have on engines of any type. Also, doesn't Merc Racing electronically bleed boost of the 700SCi package, for torque management?
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Old 11-26-2007, 03:24 PM
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Quote:
Originally Posted by Bigyellowcat View Post
Pretty low RPM, that is one reason my engines have lasted. we usually only turn them in the 4000 rpm range but I have over 1100 hp at 4k. I run 110 octane fuel. I will admit that the 1800 hp was at around 20 lbs of boost on a 9.5-1 engine.

I tell people that my engines made 2000 hp because we ran the texoma run and the shootout at 25 lbs of boost but we never dynoed them with that high of boost. kind of scarry when all that tubing we made to dyno them kept shooting off the engine.
Very Cool and very nice numbers for the RPM ranges.
What speeds did you get at the Texoma run with 25lbs of boost? Still running the Apache Cat?

Thanks
Jon
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