Biased about what? It's not their S/C design. I'm pretty sure he was mostly comparing it to current Roots blowers.

The numbers are off an engine dyno. On 6psi that's a pretty good number. Probably around high 600's, maybe more at the wheels.

 

Actually a twin screw has a problem for street driving. It is ALWAYS compressing the air. This is one reason why Mercedes used a clutch to disengage the compressor for cruising.

The constant compression takes energy (power pulled from the crank) but more importantly causes heat. This will heat soak the assembly during cruising conditions. The resulting HOT assembly reduces the net adiabatic efficiency considerably.

For racing only the twin screw is excellent and highly efficient. HOWEVER, the new TVS series Eaton's are highly efficient also and with a bypass do not have the twin screw compression at cruise problems. Comparing the two on the street the average efficiency of the TVS is possibly HIGHER than a twin screw (without an imput clutch).

Another issue is noise. Here is a quote from an engineering forum:
http://www.eng-tips.com/viewthread.c...=205859&page=6
"While screw compressors may not have the same "pulsing" as a roots, the internal compression in the unit (pressure ratio built-in of approx 1.4) results in a case where air is being compressed, and the "re-expands" when the bypass valve is open. This expansion results in a "popping" sound as it is often characterised, and the screw compressor is typically regarded as being noisier than the newer style Eaton type roots blower with the 3 lobed twisted rotors."

I for one am VERY excited to see what the real world potential of these new blowers really will be... especially the 2300.

 

Yes, that is what I implied with "racing" above. Above say 12psi the twin screw outpaces the high helix TVS. However below 12psi the TVS series are highly efficient with mid 70% range adiabatic.

Bypass works differently on a screw as they do not prevent the internal compression. Still needed and used but will not resolve that issue.

Here is the 1900 map showing a solid 75% island at 1.55 - 1.65 PR (8.0 - 9.5psi) and holding 70% all the way to 2.2 PR (17.5psi)

Here is the TVS 1900 map

 

No way you are going to feed a 1/2way decent sized motor with a 2.2pr a 1.9 blower and only 12000rpm blower speed. that would be a 3.5" pulley at 6500rpm...

It take a 2.8 KB a 2.5" pulley on a 8" crank at 20,000rpm blower speed to make the same 17.5 psi.

With that 1.9 or even the 2.3 you will be at 65% efficiency at best.

 

When I mean the vendor I am talking about a factory rep. Sorry in my world of Government acquisitions vendor means the factory not the middle man.


And since it is a six speed then 10-12%.

 

thats sick!!!

 

If its one thing I HATE, its in accurate information..

First off, 9 times out of 10 (without looking it up on the internet), people who speak like this dont even know what the true definition of adiabatic efficiency is..

Secondly,
The KB not ony uses a bypass it utilizes a LARGER bypass than the roots.

Third,
The Twin screw pulls the bypassed air AFTER the I/C, so when it recirculates, it is actually recirculating cooled air. Unlike the roots, where it recirculates and continually heats the air charge. Hence the reason roots blowers tend to run MUCH hotter at very low rpms.

Fourth,
If the twin screw was for "Racing Only", why is it that Shelby has now begun using KB twin screws from the factory on their street cars? Better yet, why is Panoz, doing it as well?? Hell, even Eaton owns a patent on a twin screw, and they openly admit its a more efficient way. Its just not cost effective.

Fifth,
Twin Screws have approximately 30% less parasitic loss than the roots style blower. Not to mention, increase IAT on average of just under 9* per psi versus and average of 16.4* for the roots.

Sixth,
Due to the twin screws single path air charging, versus the circumferentially pumping (basically throughout the ENTIRE headunit) roots style, the twin screws air path is significantly less turbulent. Which actually LOWERS the pumping losses by up to 16hp over and above the roots..

I can go on, but hopefully you get the point.

You are severly misinformed when it comes to the differences between the 2, and will hopefully do a little reading on BOTH types of blowers, and not just listen to a bunch of internet garbage..

I know this comes off as harsh, but in order to debate the differences between 2 items, you need to know the fact first. Not make up your mind based off f eneral popularity..

Heres a FACT:
The Eaton head unit cost $300.00 to manufacturer
The Twin screw costs just over $1000.00

As a manufacturer, which one would you use??? Which one would you market??

You would choose and market the most profitable one..

 

good info. thanks learn something new every day. u strengthend my knowledge about twin screw's vs roots. appreciate it.

 

I am glad you gained some knowledge from it.. That was my point.

Unfortunately, typing words does NOT allow a person to express their atttitude when typing. I hope that I did not come off as rude, or disrespectfull. I look at it as 2 men having a conversation over a beer. Just because your bro gets loud when he's talking to you, doesnt mean he's being an ***.

That being said, to the first guy I quoted, please take what I said with the upmost respect. I was NOT intending on talking down to you, even though after I re-read it, it looked like I was..

 

Just an update, they posted some new results over on CF. The car did 733/646 on the dyno. Then they took it to the NASA event at Road Atlanta and ran a 1:25.7 lap during one of the time trials.

That's .1 off the World Challenge qualifying record.

http://forums.corvetteforum.com/show....php?t=2104027

 

That is crazy. The car seems to like that charger alot!

As for what blowers are better, Depending on money spent, you can make anything work as good as a roots/ procharger ect...

I have hit a wall with my 454 on power with the mp122 and Ordered a TVS 2300, I would love to get proved that another roots type blower will beat the TVS.

Im open if you want to get the kenny bell guys to send over a test unit in order for me to do a no other change but blower intake units from one to the other to see who does more power on the same big engine.. Same boost level for each ect.....

 

If you kept the same exact pulleys and simply changed from a TVS 2300 to a KB2.3, you would get up to 1.35 times more boost at a lower temp. You can't get around that built-in twinscrew compression ratio and the efficiencies it buys you. That's why you are already seeing Ford GT's upgrading from the TVS unit to the Whipples and KB's, even units of the same size. They get a fatter power curve that stays higher longer.

TVS is publishing their efficiency numbers without taking into account the power it takes to spin the supercharger, which is why, on paper in pretty charts, they show such high numbers. Whipple (Lysholm/OPCon) numbers take drive power into account which is why they read lower. This is a big deal since blowers in this size range can take 60-90HP to drive at high boost/high rpm.

Jeff said it well above, particularly about the cost factor. Also the TVS is quieter.

Jim

 

??? the Ford GT comes with a twin screw blower from the factory.

 

Jesse, I would definitely like to see that test. I have done similar tests, and yes a twin screw outperforms, in some cases, it does not do so until 6000rpm.

 

I agree that there is some in-accurate information in this thread.

Depending on the roots blower, the bypass routing you described is not always true. On my roots and tvs application, the bpv air is cooled, which helps greatly to reduce temps on tip-in and while cruising.

Last time I checked the ZR1 was using a TVS, has this since changed? The ZR1 is not exactly a cheap car, certainly $700 could be a wash for them. Roush and FRPP use the TVS. You can make the argument either way about who is using a TVS or a twin screw.

 

I am running my 2300 TVS at 19,000RPM and 2.4PR making 705RWHP/708RWTQ DJ SAE on a very small 330 cubic motor (comparatively). It makes more low end than any of the twin screws out there, some of the twin screws don't surpass it until ~6000RPM, when its time to shift anyways. Yes the TVS is limited to 1.9L and 2.3L displacements, so it will never run with the big blowers, but bigger is not always better when it comes to blowers.

 

Agreed ... so lets get some facts stated.
As one of the very few, perhaps only, manufacturers of both twin-screw (Lysholm-based) and Roots (Eaton-based) superchargers we can make some statements based on unbiased fact that is backed up with both test-bed & real-life data.

Depends on the model ... our TVS2300 uses a 50 or 55mm bypass depending on the application, as does our TSK140 twin-screw.

Again, this depends on the application. Many of the superchargers we make (regardless of twin-screw or Roots) have an integral bypass that is routed from the cooled air. In one case, the bypassed air is cooled twice in one lap.

I would like to see some evidence of this as it is contrary to our (extensive) testing. It would be an accurate statement if only a segment of the performance range was analysed.


Again ... this is not consistant with our unbiased testing. I would like to view some data on this.

This has not been our experience ... in fact, our testing shows quite the opposite.

Again ... not fact.
I can state in absolute terms that if manufacturing Roots and Twin-screws in the same volume, the difference is nothing like the $700 stated above ... it is within a few percent.



I would welcome some data to prove this incorrect ... ken@harrop.com.au

Cheers ...

 

Bringing and oldie up...Jeff what did you have to say to this?

 

^ What he said.

Magnuson seems to have a very large customer base, with positive feedback from numerous customers on many forums... why do some other vendors seem so hostile towards the reliable product they provide, along with good support after the sale?

from above: ...Unlike the roots, where it recirculates and continually heats the air charge. Hence the reason roots blowers tend to run MUCH hotter at very low rpms. ...

I apologize for being a little slow on this FI stuff, but if this "roots blower air charge is recirculated continually", what air is the engine using for combustion? On my roots blown car, the engine runs 15+ inches of vacuum (under the blower) on the highway, leading me to assume that very little "air" is being compressed at light load.

Please help me understand.

 

wow... back from the dead...