Originally Posted by pbonsalb
Because the planetary gear drive blowers like the Rotrex, HKS, and ASA spin about twice as fast as the Vortech, Paxton and Procharger single step up ratio gear drive blowers, the centrifugal effect begins a little sooner and boost build a little sooner. I think "a little" is the right description. The downside is that, at least thus far, none of these blowers have had the top end of the Vortech. Their small impellers are less efficient at high flow volumes and their complex gear drive system does not allow them to reliably be spun any faster.
So thus far, it has been a compromise between a little better midrange with flattening out on top or a little less midrange and no loss of flow up top. ESS used to use the ASA, but changed to the Vortech. ESS has previously stated their testing did not show any dramatic differences in power curves or reliability, but that it was simpler for ESS to use one blower in all of its kits and only the Vortech had the flow range for that broad use.
Whoever said they want to feel instant boost needs to study centrifugal superchargers. A centrifugal that makes 9 psi at 8400 rpm will make roughly 3 psi at 4200 rpm. It is just the nature of the centrifugal. The planetary gear drive blowers may improve on this a little -- would 4 psi at 4200 make you happy -- but not dramatically and they sacrifice some flow on the top end. If you want instant boost, the closest you will come is a positive displacement blower like a twinscrew of Eaton 4 lobe, but no kits are available for these cars. Or a turbo sized a little on the small size.
One of the car specific problems with instant boost is that the S65 is an 8400 rpm motor and high rpm motors just don't make much power at low rpm and this is also true when they are fitted with any form of forced induction. Another car specific problem is the 12.0:1 compression ratio. You simply cannot run much boost in the natural torque window (peak cylinder pressure) on pump gas. The centrifugal is actually well suited to this engine for these reasons -- its boost follows the engine's power curve and causes no real issues. It is also much much easier to tune than a turbo.
I know Rotrex has come out with the C38-91, which is higher flowing than the previous top of the line Rotrex models and that ASA is also working on a higher flowing blower or may already have it. But the inevitable larger impeller means it takes a little longer to get flowing, which diminishes some of the low to midrange advantage. Time will tell on how these work out. AA has already shared dyno tests of a built motor running a C38-91 at way more boost than Evolve is running and the power was not exceptional. It was on a development tune, so maybe a little more timing (always risky with 12.0:1 CR on pump gas) will help. ESS, on the other hand, has run the Vortech Si Trim to about 650 rwhp.
Exciting news in the world of centrifugals is coming from Procharger, which has developed a variable speed transmission that is user adjustable to alter the flow patterns. It can spin the blower faster at lower rpm to make boost sooner than any centrifugal on the market. Should be released later this year. It has a big body to house the transmission and may be best suited for large displacement V8s that have the torque to spare to drive the blower fast at low rpm. Time will tell.
Most of what you say is theoretically correct.
However, study the compressor maps (and correct them to the same standards before you do) of the V3Si and C38-91.
What you will find is that the Rotrex produces more boost much earlier and closely matches the V3Si for absolute maximum airflow. They both produce over 1100 CFM.
Vortech shows 1150CFM with SAEJ1723. Correct the Rotrex to the same standard and conditions and it makes 1134 CFM.
So how do they actually perform once bolted to the engine? Is there a big difference?
Top end HP no not really. Through the RPM range - yes.. very much so. Under partial load rolling on the throttle - massive difference. Response - Big difference.
The effects are completely different from one blower to another.
Once you are in a development programme this complex it takes hardly any additional effort to make a bracket to fit another type of blower. The rapid prototyping of intakes is quick and everything can be tested. We have this data to hand. We have not really gone about posting it and comparing blowers as it causes nothing but chaos. Now the questions have been asked I guess we need to respond.
Out kit gives quite an impressive low-mid rpm torque delivery. The response is very much instant. If people find this too much then we will give the option of the V3Si. We just put the bract into production. We use the same pulleys as we prefer an 8 Rib setup for best belt traction. It would very much still be unique as it would be the first Vortech based air to air inter cooled setup out there. We will ONLY make it if people find the response and torque of the Rotrex is too much. Highly unlikely. One of very secondary reasons we used a Rotrex is because no one else did at the time. So uniqueness was important to us also but not an over riding decision maker.
If anyone insists on seeing the difference of boost and power of the blowers we can supply this but I would ask people wait for the kit to go on a few people's cars first and you get independent reviews to back up what I am saying. This way you probably won't need to see any kind of comparison and we don't need to start getting into the 'which blower is best' wars which other companies can fight out. We personally do not care which blower we use. We have no personal relationships with any company and have no allegiances to them. We use the one we feel that fits the bill as per our concept of tuning.
All I can say is that both blowers are great. They clearly both produce excellent results and not just on this platform.
We have used the Vortech's and Rotrex on the S62's and the difference is very similar. Same top end power. Everything else is different.
You will see. Give us a chance.
The Rotrex that was used on the AA car was running at around maximum capacity and it made 580rwhp on their Mustang. This would equate to a fair bit higher on a dynojet.
Interesting new on Procharger but as you say... they are a little large!