Reply With QuoteDustin was a great resource at Whipple, unfortunately he no longer works there.
Whats the difference in a roots and screw blowers?
Sorry it took so long to reply, but Dustin of Whipple blowers has that answer.
Heavy boat,
Example temps @ 12psi, 900SC, max HP, before IC.
1071= 290F
Quad 2.3= 180F
Also keep in mind the fuel running through reduces the air temp. The hotter the temp is, the more the fuel removes. Estimated power consumption at peak hp
1071=135
Quad 2.3=60
If you have some doubts of their effectiveness, go to the Miami Boat Show in Feb. and walk by the Marines largest engine supplier, check out what there offering.You are somewhat correct in the fact that one of the short comings of the roots type is the lack of internal compression. The screw compressors do have internal compression. They vary from application to application, but an example for the 2.3L is 1.35. This allows for far less leakage through the casing and rotors. Every case design, rotor design and then every application including blower speed, manifold PSI, manifold temp all function into leakage. This is referred to as volumetric efficiency. Roots are typically in the 40-50% range while the screw is in the 85-95%.
The idea of trapping the air after every rotor lobe opening is simply not possible at the current blower speeds and would have very little purpose. If it was possible, it would certainly allow for lower temp gains but thatÂ’s what better superchargers are for. Parasitic losses would still be a major problem. Centrifugals and turbos have the same problem, if you have any clearance, you will have some type of leakage. Only industrial screw compressor have reached Volumetric efficiency levels of 100% and they are "oil flooded" which seals the rotors and casing. The screw compressor is not only better in area of heat, it also very efficient at trapping air and moving it. Screw compressors have port timing in the rotors and casing similar to a two stroke engine. There are other things that you are not aware of:
-Screw compressors prepare fuel for combustion far better than another supercharger. Because it has the ability to compress and mix the air and fuel together allowing better distribution in almost all cases. Roots just move air and do nothing to promote better combustion.
-Screw compressors, when running the proper amount of fuel through it actually intercools itself. The fuel goes through a phase change, from liquid to gas, this creates a massive cooling effect. Run a screw compressor for 20 minutes, WOT, 15psi 14,000 compressor speed and you can put your hand on it. Ice actually forms on the top of the compressor!!
-SAE (society of automotive engineers) found that there is no better way to produce such a wide range as well as peak torque than the screw compressor. This is due to the positive displacement design, high efficiencies and air flow demand of an IC engine.
-The lightweight, deep lobed, shorter, perfectly balanced screw compressor rotors take less energy to rotate (less torque of inertia), accelerate quicker and last far longer.
The fact is that the roots has done it's job for many years, but there are tremendous down falls that have never been addressed and cannot be addressed. Especially with the 671-1671's. Just some of the problems for the blowers offered to the performance boaters:
-Very big and bulky for the air volume they deliver. Example, our 3.3L is better than any 871 (in efficiency and power potential), yet its externally 40% smaller.
-Distribution. Although a few have played with moving the discharge ports all around, some have played with making them smaller and bigger, the common problem is bad distribution. Drag racing has fought this for years (our blower is banned from top fuel), they now have the blower positioned more towards the center of the intake and the inlet slid all the way forward.
-Heat. They build tremendous heat as the boost builds up, some rotor designs and some cases are worse than others, very few are a like. This is harder on everything.
-Parasitic losses. Due to the lower efficiency levels, they consume more energy than almost all other superchargers. This has more resistance against the crank shaft and reduces total hp and torque.
-Massive rotor sizes allow far more flex and distortion meaning you must open up clearances so they don't touch, in effect, this lowers overall efficiency and shortens bearing life. Race style roots supercharger use teflon or nylatrol strips to try and seal. These take even more energy to operate until they self clearance themselves. Between the time of creating tremendous friction and heat and then self clearancing, they need to be replaced. Almost all extreme racing applications require you to replace them every single run and this is drag racing which is a very short pass. If they don't SC performance falls off dramatically which lowers overall power.
-Wasted space and energy. The roots typically pull from the top center and exit out the bottom center (some have moved this around). ThereÂ’s large areas of the rotors that simply do not help move air. The screw compressor moves the air axially through the case utilizing the entire rotor volume.
Your attitude towards "easier on engine" is completly off. The fact is, the more efficient the supercharger (since it's heating air and taking energy to operate), the easier it is to achieve certain power levels. If you are running say 10psi to make 1000hp with a roots that is lets just say taking 125hp to operate, then install a better supercharger, same engine, same 10psi, same engine rpm, same discharge temp, but only takes 25hp to operate, you would effictively gain 100HP making 1100 while actually lessening the strain on the crankshaft/bearings. Are the rods somehow seeing more pressure, how about temp? NO. How about the pistons, the block, the valves, lifters, springs? NO. Is the actual cylinder pressure increasing? NO. What if you use a better coating on the cylinder walls which reduces the frictional losses, I've seen that make 50-100hp. Did that somehow hurt the motor more? No, less.
It's also a fact that you can build engines around the SC to further lower strain, especially in comparison to the roots. You can run 7:1 compression/high boost vs. 9:1 compression/low boost. The overall duty cycle of the engine, especially for normal boating conditions will have far less heat and strain on the engine than the high compression motor. You will also create more power, far more power where a roots will not allow you to do this.
So don't "try" to look through a sales tactic, learn whats true and whats not. The roots will never reach the performance potential or ease of power that the screw compressors, centrifugal or turbos provide. That is a fact.
HP350SC, for 1600hp and more (you can make more), theres so many varibles. The obvious is all the best internals, solid roller cam, dry sump oil system, big tube exhaust.... If you wanted to do it on 110-116 octane which realitively simple, then you would need low compression 7.5:1, 16+psi of boost, really good flowing heads with a good combustion chamber design such as the Big Chief (but not as cast), Sterling does awesome work on their Big Chief heads. You need a big intercooler, big carbs or big TB's for EFI. You can certainly do it without NOS. Here would be some rough specs if I was building one for play in my boat:
3.3L quad
598ci, billet crank and rods
Big chief heads, CNC finished, major porting on exhaust side
6.75:1 compression, Mahle forged and coated pistons
20lbs of boost
Solid roller cam, 700+ lift, 280+ duration
92 pump gas
Racecrafters (www.racecrafters.biz), home of the Scorcerer boat, makes 2000hp with our 9.8L race supercharger and 118 octane, 1550 on 92 octane.
Thanks,
Dustin
Hope this is that answer
Willis
Dustin was a great resource at Whipple, unfortunately he no longer works there.
Well Dustin hit the nail on the head ... good post Willis!
Kevin got your PM ... to answer in a more simple way, the casting and clearances of a screw type superchasger allow for a easier rotating assy. creating less heat.
The roots type have to have a tight tolerance making it harder to turn and creates a more heated charge.
By just changing the blower, you free up horsepower while cooling the charge at the same time ... so even at the same boost levels, you have freed up HP that will RPM the pump quicker ...
Brian
I think it sucks ass that they "retire" records after a peroid of time.
MAJOR slap in the face to the teams that set them.
agreed
BigBlockolds,
I don't think you are being negative at all. I think you asked the questions and had the thoughts that most of had but did not want to throw out there. I have a lot of the same questions. When someone comes out and lays out the Gauntlet such as Willis did, people are naturally going to look back at his past performances and form an opinion from that. I do not believe Willis has run within a full second of the record. Not slamming Willis. I think you guys are giving BBOlds a hard time when he has been diplomatic about it.
well, i disagree with ya and i do think he was blastin' and baggin willis for past performance a bit. but, if ya never went out there, you'd never risk getting praised or pounded, now wouldja?
from what i recall, not too many bgj guys just fell out of the womb one day and just threw their jocks on the water and ran 7.60s. somebody wants to say nelson never had any problems, well there's some news flashes you missed. jimb s went through some trials too before he got it together, and harris took at least one swim, among other things.
ronnie, what got dan p.o'd was that he ran the 7.40 on a red light, so they wouldn't acknowledge the record. he jumped up and down a lot and never came back, but, it was in the rule book then, and in the rule book now. why? i have no idea. another one of those wierd deals. but i don't remember if that was november 00 or 01. we ran those 140 runs in 01, and there were actually several time slips that said 140+. data said boat was haulin the best it ever did that weekend, which was the last we ran it.
to set records, it takes more than just a different blower, or turning the boost up a bit, or a few new parts. all that stuff is part of it, but that just means you get to go to work now. nobody ever set a real record in a parking lot.
BTW Willis ... where is the bag? You know you can't run it that way, right? You'll never pass tech ...
http://img.villagephotos.com/p/2002-...nditsalive.gif
mj680 -
Just to keep everything straight ...
1) The Only Thing Tom Papp Racing about Dan Nelson's Boat was the original hull ... The Bottom (Keel), Intake modifications, Loader ... All Hardware as well as all of the pump work was thought out and done by Dan Nelson Himself ... As was his motor.
2) Tom Papp never had Anything to do with Jim Sampica's Boat ... Jim's hull did not come from the original Cheyenne molds Tom had and sold to Capps (It is One, the First, of Two Special LayUps requested by a 'guy' here in Phoenix ... Splashes, if you will, that had a few Very Different Things About Their Bottoms).
What Jim was able to Accomplish with his boat was Purely A Result of the effort of what He Did with Dan Nelson ... Jim's Motor, 'Grandpa' was built by Dan (With Jim's Input). All the Pump, bottom hardware, etc. Logic was done by Dan with Jim doing alot of the machine work (Jim is a Master Machinist, Old Style & CNC).
None of what I've posted above is to take anything away from Tom and His Shop as, from what I've seen and heard, his shop puts out reasonable work ..... I would just like to see Credit Given Where Credit Is Due and Credit is not given where it is not appropriate ... Dan Nelson & Jim Sampica can make jet boats Quick ... as can Tom Papp.
As 'Another Sampica' reminded me today ... Winter is Here and it's now the Time that 'Stuff' comes out on these Threads.
Jak
well, i disagree with ya and i do think he was blastin' and baggin willis for past performance a bit. but, if ya never went out there, you'd never risk getting praised or pounded, now wouldja?
from what i recall, not too many bgj guys just fell out of the womb one day and just threw their jocks on the water and ran 7.60s. somebody wants to say nelson never had any problems, well there's some news flashes you missed. jimb s went through some trials too before he got it together, and harris took at least one swim, among other things.
ronnie, what got dan p.o'd was that he ran the 7.40 on a red light, so they wouldn't acknowledge the record. he jumped up and down a lot and never came back, but, it was in the rule book then, and in the rule book now. why? i have no idea. another one of those wierd deals. but i don't remember if that was november 00 or 01. we ran those 140 runs in 01, and there were actually several time slips that said 140+. data said boat was haulin the best it ever did that weekend, which was the last we ran it.
to set records, it takes more than just a different blower, or turning the boost up a bit, or a few new parts. all that stuff is part of it, but that just means you get to go to work now. nobody ever set a real record in a parking lot.
Hey Bob ... Merry X-mas!
I never said that they boltd on and set records either ... my statements were that performance picked up immediately ... but there was a lot of tuning to be had ... that's why in Willis' other thread and this one ... I brought up that he needed to hold on ... that there was a lot of work ahead ... but BBOJ was bashing Willis' program and performance pretty good IMO ...
Hope all is well with you and that Willis gets his X-Mas wish of a new record next year!
BB
to set records, it takes more than just a different blower, or turning the boost up a bit, or a few new parts. all that stuff is part of it, but that just means you get to go to work now. nobody ever set a real record in a parking lot.
In a round about way, that was kind of the initial point I was trying to make. All I was basically asking in the begining was for the Willis team to explain what they have done that elevated their team to a potential record breaking level and how they expected to break a record that was above the 145 MPH open cockpit speed threshold.
Jak
good to hear from ya,
Brian, The bag is in the truck, took it off to clean up the boat and prevent moisture builup :220v:
Also had to make a new rope deflecter.
Willis
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