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Roots-type supercharger gurus.............

 
Old 02-14-2019, 08:38 PM
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Default Roots-type supercharger gurus.............

So, I want to use a roots-type supercharger......19-21psi....goal is 1,100 RWHP.

I've been told that if I spin SC'er too high on the top end which will is great....max power.......It will be spinning too fast down at the low rpms when driving normally around town.

Is that true.....?

Say use a 70mm upper and a 10% lower, it'll spin at 22,700rpm at 7,000 engine rpm. Will that drive perfectly normal at idle, cruising at 30-40-50-70 mph.

Is there any problem like this with roots-type SC'ers.....?

Thanks....

.

Last edited by snow---flake99wssix; 02-15-2019 at 01:35 AM.
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Old 02-15-2019, 02:43 AM
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If you run one that has the built in bypass valve, it's not going to make boost just cruising around. From personal experience though I wouldn't spin the blower higher than the manufacturer rating. They become inefficient due to heat and turbulence, not to mention most bearings aren't rated for more than 20k rpm.
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Old 02-18-2019, 05:35 PM
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Originally Posted by kyoytey1693 View Post
If you run one that has the built in bypass valve, it's not going to make boost just cruising around. From personal experience though I wouldn't spin the blower higher than the manufacturer rating. They become inefficient due to heat and turbulence, not to mention most bearings aren't rated for more than 20k rpm.
Check the rpm rating with the manufacturer.

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Old 02-18-2019, 06:00 PM
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Roots type blower probably isnt the best idea with your power goals. They arent meant for crazy high hp builds unless your running fuel that dont have to worry about knocking and high Intake air temps. Spinning too fast creates a lot of heat and can really kill high rpm power. Most cars that come with them stock are already at max efficiency out of box. Not that you cant get more HP out of them by putting on smaller pulleys, exhaust, and headwork but usually have diminishing returns. Roots blowers are way better at providing instant and reliable power over wide rpm ranges. Your power goals may be possible but i would suggest diff form of boost.
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Old 02-19-2019, 11:05 AM
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Originally Posted by 2kSilverSS View Post
Roots type blower probably isnt the best idea with your power goals. They arent meant for crazy high hp builds unless your running fuel that dont have to worry about knocking and high Intake air temps. Spinning too fast creates a lot of heat and can really kill high rpm power. Most cars that come with them stock are already at max efficiency out of box. Not that you cant get more HP out of them by putting on smaller pulleys, exhaust, and headwork but usually have diminishing returns. Roots blowers are way better at providing instant and reliable power over wide rpm ranges. Your power goals may be possible but i would suggest diff form of boost.
How about full time E85
10:1 compression
Large Intercooler
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Old 02-19-2019, 02:01 PM
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Id start with a forged ls3 shortblock and cnc ported Ls9 heads from GM performance. Then at least a 2900 or larger blower with the biggest air/water intercooler you can make work. Custom blower cam with E85 and see how fast you can spin the blower till the air gets too hot.
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Old 02-19-2019, 10:47 PM
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Gonna take a lot of money to get a blower that style to make the type of power consistently. 10:1 isn’t high enough especially on e85.
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Old 02-19-2019, 11:09 PM
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Originally Posted by Detoxx03 View Post
Gonna take a lot of money to get a blower that style to make the type of power consistently. 10:1 isn’t high enough especially on e85.

Can you explain the reason you say 10:1 isn't high enough?
I have a 408 that made over 900hp on the dyno with a 10-71 old school roots blower on E-85 at 15lbs of boost and compression is 8.5:1, Lower compression and more boost is better than more compression and less boost unless something changed that I didn't hear about?

He's not going to get those numbers with an LS3 bore and stroke or LS3 heads unless they are heavily ported but a stroker combo with good heads should get him there.

Last edited by LLLosingit; 02-19-2019 at 11:19 PM.
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Old 02-20-2019, 12:11 AM
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Why not go turbo?
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Old 02-20-2019, 12:55 AM
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Originally Posted by LLLosingit View Post
Can you explain the reason you say 10:1 isn't high enough?
I have a 408 that made over 900hp on the dyno with a 10-71 old school roots blower on E-85 at 15lbs of boost and compression is 8.5:1, Lower compression and more boost is better than more compression and less boost unless something changed that I didn't hear about?

He's not going to get those numbers with an LS3 bore and stroke or LS3 heads unless they are heavily ported but a stroker combo with good heads should get him there.
Not taking advantage of e85 fully with that compression. Old school thinking would suggest the low cr more boost is the only way to go but tech has advanced. Outside of this site many people are and have been doing high cr setups with lower boost and timing levels with great success. Mine is stock cr 10:7.1 and Iíll bump it to the 11ís eventually. 980 and 21psi sbe LS3. He can make the power with one just have to do it right.
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Old 02-20-2019, 06:52 AM
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Originally Posted by Detoxx03 View Post


Not taking advantage of e85 fully with that compression. Old school thinking would suggest the low cr more boost is the only way to go but tech has advanced. Outside of this site many people are and have been doing high cr setups with lower boost and timing levels with great success. Mine is stock cr 10:7.1 and I’ll bump it to the 11’s eventually. 980 and 21psi sbe LS3. He can make the power with one just have to do it right.

But it's not the old school way of thinking, You can still pack more fuel and air into the cylinder with lower compression ratio and in turn make more power. There are other benefits like less valve shrouding and wider tuning window and so on. It's not just a theory but has been proven over the years. It may not be a lot but it's there and it's free power.
The main reason people say otherwise is usually because they are running a turbo on the street and don't want it to be a dog off boost, Roots style superchargers don't have that problem.

Aren't you running a centri not a roots? A roots blower doesn't suffer from low end power loss with lower compression like a turbo and centrifugal supercharger does. They make boost from idle and make tons of low end torque.

Last edited by LLLosingit; 02-20-2019 at 07:04 AM.
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Old 02-20-2019, 07:57 AM
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I know the differences in power delivery. There are more than one way to skin a cat. His blower choice is gonna hold him back from his power goal either way.
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Old 02-20-2019, 02:29 PM
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I'm not very knowledgeable, but Leah Pritchett's super stock Dodge Demon makes up to 1,300hp with a 2.9 Whipple. Randomly came across a video yesterday. It's a factory 6.1 Hemi that's bored 60 over, so it isn't very big.
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Old 02-20-2019, 02:32 PM
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Looks like they can get much bigger......ModelDisplacementMax Continous RPMMax Peak RPMMax CFMMax M^3/HRMax PSIPeak VEPeak AESC Blueprint (PDF)W100AX1.6 Liter/rev18,00020,00011201902309981100AXW140AX2.3 Liter/rev18,00018,00014302430309980140AXW140R2.3 Liter/rev18,00018,00013892360309577140RW175AX2.9 Liter/rev18,00018,00017202922309978175AXW200AX3.3 Liter/rev16,00018,00021403635309978200AXW200R3.3 Liter/rev16,00018,00020303449309476200RW245AX4.0 Liter/rev16,00018,00025184278309978245AXW305AX5.0 Liter/rev18,00020,00034625882309877305AXW305R5.0 Liter/rev18,00020,00032505522309375305RW510AX8.3 Liter/rev11,00012,00034625882309877510AXW510R8.3 Liter/rev11,00012,00032505522309375510R
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Old 02-20-2019, 05:09 PM
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Fountain Racing Engines.......made 1150 FWHP with a Harrop 2650 Supercharger last month on a 416 LSA engine with LSA 8-Rib drive................15psi and E85. NW 102mm TB.

That was NOT with the larger 10% lower pulley.

Last edited by stilealive; 02-20-2019 at 05:15 PM.
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Old 02-20-2019, 06:00 PM
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Originally Posted by Detoxx03 View Post
I know the differences in power delivery. There are more than one way to skin a cat. His blower choice is gonna hold him back from his power goal either way.
I guess looking back at his post I'm not so sure he's even looking at a roots style blower, You don't turn a roots 22,000rpm, A centri maybe. If he was looking at a true roots style then he can easily find a blower that will support the power he's looking for.

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Old 02-21-2019, 10:41 AM
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So....Eaton recommends a max rpm of 18,000. So how much further can you take it before it gets inefficient?
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Old 02-22-2019, 04:29 PM
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The tvs2650 looks like it has potential to put down some good numbers. I look forward to seeing more people running it. Physically ive been told the harrop 2650 is the same size and a maggie 2300
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Old 02-22-2019, 07:35 PM
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A 2.3L TVS is good for ~650 rwhp at 15000 rpm. I've had two of them running that speed. No heat problems at all. Doing a little cyphering, a 2.65L blower should blow enough air to hit ~750 wheel running similar blower speeds. Run the 2.65L blower up to 18000 rpm and you're in the 860 wheel hp range. I haven't heard how good the intercooler/heat exchanger system is on the 2.65L TVS. That could be a limiting factor. Plus, you'd need to be sucking through a bigger throttle body (or a pair of throttle bodies) to help this thing breathe. A big cube engine would certainly help too. By far, not the easiest way to get four digit power numbers. It would be a fun ride getting there though.
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Old 02-22-2019, 10:48 PM
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Originally Posted by old motorhead View Post
A 2.3L TVS is good for ~650 rwhp at 15000 rpm. I've had two of them running that speed. No heat problems at all. Doing a little cyphering, a 2.65L blower should blow enough air to hit ~750 wheel running similar blower speeds. Run the 2.65L blower up to 18000 rpm and you're in the 860 wheel hp range. I haven't heard how good the intercooler/heat exchanger system is on the 2.65L TVS. That could be a limiting factor. Plus, you'd need to be sucking through a bigger throttle body (or a pair of throttle bodies) to help this thing breathe. A big cube engine would certainly help too. By far, not the easiest way to get four digit power numbers. It would be a fun ride getting there though.
The Harrop 2650 technically has made 1,000 RWHP. A shop in Florida made 1150 FWhp at 15psi.

Another guy in South Florida made 803 RWHP with a basically stock Chevy SS engine....no mods except for the Harrop 2650 and a new cam to accommodate the blower. Ran 9.84 @ 142 mph.

Here it is at the drag track and doing highway pulls: ((just about the ugliest car possible....but it shows what the Harrop can do on the LS engine))
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