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Discussion Starter · #1 ·
I was bored today I desided to increase my knowledge. I was interested in why a twin screw is sooooooo... much more different than a roots blower. pictures was the only why i understood what i was reading. it appears that the twin screw holds the incoming air for about 2-3 inchs of the screw and then dumps it straight down. the roots just graps it and then pushes it off to the sides and then down into the intake.

a roots is only 40-60% efficient and a twin is 60-80% wow! the twin screw has the same efficiency as a turbo.

the real impressment was the gains many cobra owners were seeing. 2-3 psi increases with the same pully and 42-70 HP.

on whipples site they have all their supercharges listed by size but im not sure what Liter output is a good match for our engines. and they was in the 1800 dollar price range. looks like a better way than twin charging.

oh well just a little info rant but im serously thinking about measuring up my m62 and doing this mod.(does anyone have a blueprint with dimentions i can use to find a match?)
 

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Contact them & see if they have any intention of building a kit for the RL. If not, maybe we could all petition to convince them to.
 

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Is it true that they dont have bypass valves? I was looking up some comparisons today. The down-sides I read all involved daily driving.
 

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BlackLine said:
I was bored today I desided to increase my knowledge. I was interested in why a twin screw is sooooooo... much more different than a roots blower. pictures was the only why i understood what i was reading. it appears that the twin screw holds the incoming air for about 2-3 inchs of the screw and then dumps it straight down. the roots just graps it and then pushes it off to the sides and then down into the intake.

a roots is only 40-60% efficient and a twin is 60-80% wow! the twin screw has the same efficiency as a turbo.

the real impressment was the gains many cobra owners were seeing. 2-3 psi increases with the same pully and 42-70 HP.

on whipples site they have all their supercharges listed by size but im not sure what Liter output is a good match for our engines. and they was in the 1800 dollar price range. looks like a better way than twin charging.

oh well just a little info rant but im serously thinking about measuring up my m62 and doing this mod.(does anyone have a blueprint with dimentions i can use to find a match?)
Well, a few questions and comments here...

The 2-3 psi increase: The don't make a twin-screw that moves 1L of air like the Eaton, the closest two are 1.16L and .89L. I would have to imagine that's part of it right there.

The charts I have in front of me, from Eaton and Autorotor, show the Eaton M62, at 2bar, starting with an adiabatic effic. of over 80% declining to 54% by 14,000 rpms. The volumetric effic of the M62 peaks at 95% at 14,000 rpms, and the outlet temp is 78 deg Celcius with a peak of 82 Celcius at 14k.

The 1.16L Autorotor at 2bar, for sake of brevity, has nearly the identical same stats, including the amount of power it takes to spin the rotors. With the exception of the discharge temps, which are much higher. I'm not sure why that is, since everywhere I've looked I'm told the twin-screws have lower outlet temps. The Eaton charts do not have the ambient temps listed, so I won't compare them. The Autorotor charts do however, and it's quite a bit higher than the Eaton.

Not sure where the appeal is. It's not like I'm getting any of this of the Eaton sales sites either. The kit that is sold for the BMW Z3 adds 54 rwhp with the .76L twin-screw. So it does seem to be adding about what ours does, with less of a supercharger, but it also has a few other things that come with the kit other than the supercharger.
 

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I looked at the autorotor graph and honestly I had no idea what was going on. There was crazy lines everywhere. Here is a little blurb I found online
A variation on the positive-displacement configuration, externally a twin-screw supercharger appears much like the common Roots design, but inside the case it’s a different story. Air enters the twin-screw supercharger through the rear or top rear and is compressed internally between screw-like rotors. The twin screw’s shorter airflow path reduces the high turbulence, friction, heat, and pumping losses characteristic of classic Roots designs, but without sacrificing the positive-displacement design’s instantaneous boost virtues. In one comparison of similarly sized Roots and twin-screw blowers, the Roots’ intake temperature rise from boost was about double that of a twin screw (about 8.6 degrees F/psi for the twin screw compared to the Roots’ 15-18 degrees F/psi). That extra charge temperature robs power potential. High-end racing twin-screw blowers exist, but they are not widespread because many rule-makers discriminate against them. However, small-screw compressors sold by Kenne-Bell have gained some popularity among the 5.0L Mustang and import crowd.
So on there test the roots was gaining an extra 9* per psi.

heres the link
car craft
 

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that's when we need an external bleeding bypass valve, when we run 20 psi with something like that...
 

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Discussion Starter · #10 ·
on whipples site they have bypass valves that you can install. i would really like to get the 1.6L i sure you could easily see 21psi with that
 

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this is what we need hrere when we run high boost. not sure if it's necessary, but they say to use them in applications that run more than 12psi, it's not needed with ours because it's built in, but with a lysholm blower, pushing 20psi, i think it's justifiable
 

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Vita said:
this is what we need hrere when we run high boost. not sure if it's necessary, but they say to use them in applications that run more than 12psi, it's not needed with ours because it's built in, but with a lysholm blower, pushing 20psi, i think it's justifiable
the screw chargers are truly awesome the only problem with them is thay many of the drag race sanctioning bodies outlaw them in many classes.
 

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clownhair said:
I looked at the autorotor graph and honestly I had no idea what was going on. There was crazy lines everywhere. Here is a little blurb I found online


So on there test the roots was gaining an extra 9* per psi.

heres the link
car craft
Crazy looking charts aren't they? I know the popular opinion, EVERYWHERE that I look, says in the area of 80% Ab. efficiency. Along with reduced outlet temps, even though their own charts show a much higher discharge temp than Eaton's charts. Not sure why, must be a test variable that's not mentioned.

So if we're talking heat, does anyone have ANY idea of what out post-blower outlet temps are the the 'ol Eaton? I guess after the intercooler would be more important? Maybe not...
 

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the screw chargers are truly awesome the only problem with them is thay many of the drag race sanctioning bodies outlaw them in many classes.
which is good for me! well not good, but not bad either. don't plan to use her as a pro dragster anyways. do you guys happen to know for sure if the snout spins in the opposite direction than the roots? i am wondering because it's been said, and it would make a huge difference in the feasability of a simple swap, unless we could swap out the snouts from a lysholm blower and the m62. probably something i could ask lysholm though.

i assume we could use our stock vacuum lines to run the bypass valve, or am i mistaken with that? basically, since eaton owns lysholm, and there housing look similar, i presume that they use the same castings for the housings, or at least mounting points. i have charts somewhere at home with the other million pages i've printed looking into it, but i've got to sit down and compare the different charts.

this would be a fun winter project, since i believe that if we run the same boost leves/airflow levels, we wouldn't have to worry about tuning much until we swap out a smaller pulley, which your kit will come in handy for. :D
 

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Sp00ner said:
Crazy looking charts aren't they? I know the popular opinion, EVERYWHERE that I look, says in the area of 80% Ab. efficiency. Along with reduced outlet temps, even though their own charts show a much higher discharge temp than Eaton's charts. Not sure why, must be a test variable that's not mentioned.

So if we're talking heat, does anyone have ANY idea of what out post-blower outlet temps are the the 'ol Eaton? I guess after the intercooler would be more important? Maybe not...
i would think that the efficiency of the intercooler is more important. as long as it can handle the heat discharged by the blower without going to the limits, i don't think it'll matter much what the outlets temps of the blower are within reason
 

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Vita said:
i would think that the efficiency of the intercooler is more important. as long as it can handle the heat discharged by the blower without going to the limits, i don't think it'll matter much what the outlets temps of the blower are within reason
Ah, but if you have a blower that's discharging lower than your current one, even if the post aftercooler temps were the same, the aftercooler system would be able to handle full boost, for a longer period of time, without being heat saturated...
 

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Sp00ner said:
Ah, but if you have a blower that's discharging lower than your current one, even if the post aftercooler temps were the same, the aftercooler system would be able to handle full boost, for a longer period of time, without being heat saturated...
exactly danial son, which is what's so appealing to me about twin screw design, we could up the airflow by a good amount due to the lower air temps, and be well within our safety net of the efficiency of the intercooler
 

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Figured out those damn charts...

Figured out those damn charts...

The Eaton chart is showing temperature CHANGE over ambient. So it's not coming out of the discharge at 80 Celcius, it GAINING that amount over ambient. The Autorotor charts are showing the actual discharge temps in a, I think it was 60F room.
 

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Nice one Sp00ner. I was thinking about putting a twin screw in my SC2, but that's just gonna be entirely too much work, so instead, I would like to drop a bored, stroked, and supercharged 350 small block in there instead and make it a track only for when I get a RL (SKY or ION, not sure yet) as my daily driver. ;) ;) :D
 
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