rotrex s/c's

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 4:05 am

Im researching the rotrex s/c's for my aveo
and im trying to figure out what the hp is
it will read C30-74 head unit 150-300 hp

what does the 150-300hp mean???
is that how much hp it can handle or is it the range of hp of the engine you can put it on?

Audacity Racing · Post by **Audacity Racing** » Fri Feb 09, 2007 6:09 am

The HP rating is plausible power... the potetial the charger has depending on the engine size.

The HP is directly related to the displacement of the engine. If I had to guess, it would be 5-6psi (I haven't looked at the graph, I honestly have no idea)... 5-6psi on the stock motor is about 140-150hp, putting you at the bottom of the range for that specific compressor.

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 6:51 am

what if i jumped up to the c30-84 which has 200-320? would i be able to get more power out of that then the smaller c30-74?

Audacity Racing · Post by **Audacity Racing** » Fri Feb 09, 2007 7:11 am

If it's too big for the engine....

1. You won't be able to turn it effectively
2. You'll not make enough boost
3. You'll not be able to fit it under the hood

Shoot for a smaller compressor that will bump your power. S/C's work within specified ranges. Since they are parasitic (they ROB power), you have to have a beefy engine to get a good gain from it. This is the law of diminishing returns... at some point an engine will be too small to turn it over effectively and the boost will be replacing the power lost in parasitic drag.

Use the smaller one, if not smallest (I know you picked the next step up from what you could have)

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 7:22 am

yeah are there other pulleys that will work with the rotrex that are smaller??

Audacity Racing · Post by **Audacity Racing** » Fri Feb 09, 2007 7:27 am

Smaller pulley = harder to turn = more parasitic loss

So we have two very distinct and contrasting ideas here...

1. A smaller pulley will spin the supercharger faster giving more boost and thus more power
2. A smaller pulley is harder to turn and is a greater source of energy loss in the car

The balance between the two comes in sizing appropriately. A smaller charger with a smaller pulley is an OK route to go on a small displacement engine. It's a better option than a large charger and a large pulley.

Trust me when I say you'll be happier with a smaller, easier revving charger that makes good boost as opposed to a large one that doesn't turn well and makes mediocre boost

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 7:28 am

well thats why i asked...and actually i think the smallest one rotrex offers should be fine. but im not lookin for a minimal gain from the s/c since its gonna cost 3k+ to get it i want a signifcant gain. if you know what i mean.

Audacity Racing · Post by **Audacity Racing** » Fri Feb 09, 2007 7:44 am

IN my 5 minutes with the windows calculator, it looks like you could squeeze 8psi about of the C15-16.

Tomorrow evening I'll do a plot for you on the maps and show you where losses are and where power is

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 7:49 am

is 8 psi the most i can boost? i was hoping for 10 maybe a lil more.

exist3nce · Post by **exist3nce** » Fri Feb 09, 2007 2:24 pm

AveoSSTurbo wrote:is 8 psi the most i can boost? i was hoping for 10 maybe a lil more.

Are you planning to build the motor? Pushing over 8psi on stock motor is getting risky. Unless you want to just push it and see how much it can take before something gives out. I'm planning to put mine up to 8psi soon, but the tuning has to be good or else I will probably blow something. I would consider 10psi quite risky, and anything over that just asking for trouble without some upgraded internals.

AcingTeam · Post by **AcingTeam** » Fri Feb 09, 2007 4:27 pm

My friend put a turbo on his M3 (V6), he's only running like 5psi. His got an exhaust, but the engine is pretty much stock. He already went through like 4 fuel pumps, 5 alternator belts etc. The car isn't very reliable... and it's only 5psi on almost a stock motor.

exist3nce · Post by **exist3nce** » Fri Feb 09, 2007 4:33 pm

AcingTeam wrote:My friend put a turbo on his M3 (V6), he's only running like 5psi. His got an exhaust, but the engine is pretty much stock. He already went through like 4 fuel pumps, 5 alternator belts etc. The car isn't very reliable... and it's only 5psi on almost a stock motor.

LMAO 4 fuel pumps 5 alternator belts??? how lol......... I don't see why the alternator belt should be affected in any way.

Also I believe M3's are I6 (inline 6).

Audacity Racing · Post by **Audacity Racing** » Fri Feb 09, 2007 6:57 pm

exist3nce wrote:
AveoSSTurbo wrote:is 8 psi the most i can boost? i was hoping for 10 maybe a lil more.
Are you planning to build the motor? Pushing over 8psi on stock motor is getting risky. Unless you want to just push it and see how much it can take before something gives out. I'm planning to put mine up to 8psi soon, but the tuning has to be good or else I will probably blow something. I would consider 10psi quite risky, and anything over that just asking for trouble without some upgraded internals.

I agree. 10psi is too far for any reliability unless you intend on running a water-cooled intercooler, alcohol injection, or high test fuel all the time.

AcingTeam · Post by **AcingTeam** » Fri Feb 09, 2007 7:42 pm

exist3nce wrote:
AcingTeam wrote:My friend put a turbo on his M3 (V6), he's only running like 5psi. His got an exhaust, but the engine is pretty much stock. He already went through like 4 fuel pumps, 5 alternator belts etc. The car isn't very reliable... and it's only 5psi on almost a stock motor.
LMAO 4 fuel pumps 5 alternator belts??? how lol......... I don't see why the alternator belt should be affected in any way.

Also I believe M3's are I6 (inline 6).

Yeah, I think you're right, they are inline 6. He's now upgrading to an aftermarket fuel pump. And I have no idea why he had problems with his alternator belt... but those are the numbers, I'm not even exaggarating.

AveoSSTurbo · Post by **AveoSSTurbo** » Fri Feb 09, 2007 8:09 pm

what do you mean by stock motor? cuz i do intend to upgrade the cams and pistons and whatever else i need too to upgrade.