SC Kit for reliability (Jackson vs HKS)

[mrg666]

Rotrex is much more efficient than Vortech. I am getting the same mpg with Rotrex and engine as efficient as NA when I drive normally. You can't say that with Vortech. Difference is not just slightly more power with Rotrex. Vortech is outdated and inefficient technology that should not exist anymore.

I'm glad you enjoy your Vortech though.

[GrabTheWheel]

My experience was the Rotrex units were much less reliable than a well made turbo or roots blower. I must have been one of the unlucky ones though...

I owned both Edelbrock and JRSC C30 and C38. The roots kits will pull like a strong V6 and Rotrex kits give you the boosted feel and sound. Only real advantages I see to rotrex is a bit less weight and not sitting on top of the engine. They also might run a bit cooler IAT's when it's really hot out.

If I had to choose again it would be Harrop > Edelbrock > JRSC especially for an AutoX car.

Do you have access to E85? To me a car with a good header and tune on ethanol feels similar to the SC kits on a CARB tune and shitty 91 gas. That would probably be more reliable than any supercharger.

If you decide to go to a custom tune and E85 with a SC the difference is huge, feels similar to the power jump between a stock car and carb tune SC car.

[bfrank1972]

Originally Posted by mrg666

Rotrex is much more efficient than Vortech. I am getting the same mpg with Rotrex and engine as efficient as NA when I drive normally. You can't say that with Vortech. Difference is not just slightly more power with Rotrex. Vortech is outdated and inefficient technology that should not exist anymore.

I'm glad you enjoy your Vortech though.

*shrug* I'm not going to lets this thread sway to a rotrex vs. Vortech thing, pretty useless. I'm around 270ish at the wheels, gas mileage is lower but I think that has more to do with my driving style. Definitely happy, I guess maybe I'm ignorant and blissful?

[Yoshoobaroo]

My big gripe with Rotrex is the damn traction drive. It just doesn't inspire any confidence in me as a transmission. I'd take the Harrop blower any day of the week.

[mrg666]

Originally Posted by Yoshoobaroo

My big gripe with Rotrex is the damn traction drive. It just doesn't inspire any confidence in me as a transmission. I'd take the Harrop blower any day of the week.

LOL, you are missing whole beauty of Rotrex design. That is how it reaches such high revs and why it is so efficient.

[Yoshoobaroo]

Originally Posted by mrg666

LOL, you are missing whole beauty of Rotrex design. That is how it reaches such high revs and why it is so efficient.

It has to spin that fast because it will only build boost at crazy RPM’s. A side effect of the fact that a centrifugal compressor builds pressure at the square of the input rpm, this also means that in order to not overboost at redline you are forced to cut boost significantly at low rpms. Centrifugal compressors work much better in turbos, where the shaft speed isn’t linearly tied to the crank speed.

Positive displacement systems have a linear pressure vs rpm curve, which suits an ICE much better. They don’t need a 97% efficient gearbox cause they need ~5 times less shaft speed to get to the same boost. This means they can use a traditional geared setup that is much more robust and doesn’t rely on proprietary fluid that is designed to wear down the contact faces in the transmission.

[mrg666]

Originally Posted by Yoshoobaroo

It has to spin that fast because it will only build boost at crazy RPM’s. A side effect of the fact that a centrifugal compressor builds pressure at the square of the input rpm, this also means that in order to not overboost at redline you are forced to cut boost significantly at low rpms. Centrifugal compressors work much better in turbos, where the shaft speed isn’t linearly tied to the crank speed.

Positive displacement systems have a linear pressure vs rpm curve, which suits an ICE much better. They don’t need a 97% efficient gearbox cause they need ~5 times less shaft speed to get to the same boost. This means they can use a traditional geared setup that is much more robust and doesn’t rely on proprietary fluid that is designed to wear down the contact faces in the transmission.

All those arguments you mentioned are why I chose Rotrex. Those are the desirable qualities for me.
- Low boost at low rpm for high engine reliability given that FA20D was not designed for FI
- Linearly increasing boost with rpm to get power at high-rev of FA20D. FA20D was designed as a high-rev engine. Still drives like the same sports car not a drag car. I like shifting gears instead of just smashing the gas pedal. The whole rpm range is useful with rapidly increasing power level. Acceleration is so much different than a muscle car and exactly the sensation I want.
- Efficient, no wasted gas at low rpm, driving around town.
- Light, whole kit is just ~30 lbs additional weight. I have already offset it with a lighter battery and lighter wheels. There is zero change in weight balance of my car.

So, Rotrex works much better than any other FI for my car since it does not change anything that made this car desirable for me. If I buy another twin, I would choose Rotrex again.

[toast]

You do not get linearly increasing boost with rpm in a centrifugal blower, it is simple physics. You get linearly increasing torque with rpm because as the torque curve would normally start to fall in an NA engine the boost grows as the square of engine rpm.

If one wants linearly increasing boost they should get a Harrop/Cosworth/Edelbrock.

[gtengr]

Originally Posted by MilkyWitness

What about Jackson Racing vs Edelbrock?

Looking at just the charger unit, I'm a big fan of the Edelbrock/Harrop/Cosworth/etc. The TVS 1320 on the Edelbrock is the same blower core used for some OEM mass produced cars (e.g. Audi B8 S4).

[mrg666]

Originally Posted by toast

You do not get linearly increasing boost with rpm in a centrifugal blower, it is simple physics. You get linearly increasing torque with rpm because as the torque curve would normally start to fall in an NA engine the boost grows as the square of engine rpm.

If one wants linearly increasing boost they should get a Harrop/Cosworth/Edelbrock.

Positive displacement pumps (not compressors) increase flow at constant pressure with increasing rpm.

Centrifugal compressors (not pumps) increase pressure with increasing rpm.

https://en.wikipedia.org/wiki/Supercharger

So you get a compressor (centrifugal) if you want boost increasing with increasing rpm not a pump (positive displacement).

But if there is resistance to increasing flow (i.e. engine is not able to pass increasing air flow) pressure increases with a positive displacement supercharger as well. But this is not due to pump increasing the pressure, engine increasing the back pressure. Simple enough?

[Yoshoobaroo]

Originally Posted by mrg666

Positive displacement pumps (not compressors) increase flow at constant pressure with increasing rpm.

Centrifugal compressors (not pumps) increase pressure with increasing rpm.

https://en.wikipedia.org/wiki/Supercharger

So you get a compressor (centrifugal) if you want boost increasing with increasing rpm not a pump (positive displacement).

But if there is resistance to increasing flow (i.e. engine is not able to pass increasing air flow) pressure increases with a positive displacement supercharger as well. But this is not due to pump increasing the pressure, engine increasing the back pressure. Simple enough?

It's simple enough, that's how the compressors/pumps work in a vacuum (not literally). The flow rate of the engine is the other half of the equation.

Used as a supercharger on and ICE the behavior of the system results in linear pressure increase with RPM for the PD blowers, and Quadratic increase of pressure vs RPM for the centrifugal compressors.

There's a reason no OEM uses centrifugal compressors unless they're bolted to a turbine. No consumer wants that kind of power curve.

[mrg666]

Originally Posted by Yoshoobaroo

It's simple enough, that's how the compressors/pumps work in a vacuum (not literally). The flow rate of the engine is the other half of the equation.

Used as a supercharger on and ICE the behavior of the system results in linear pressure increase with RPM for the PD blowers, and Quadratic increase of pressure vs RPM for the centrifugal compressors.

There's a reason no OEM uses centrifugal compressors unless they're bolted to a turbine. No consumer wants that kind of power curve.

Oh no, we are going through the same stupid arguments again. There is Honda and Koenigsegg that used Rotrex before. Search and find, I will not post links again. But you are right. Market, people like you, want instant power, muscle car response. That is why OEMs prefer positive displacement although it is less efficient, bulky, and heavy. But, I agree with one thing, positive displacement can be more dependable. I guess we are done.

[toast]

Purple trace is boost. Log file from an Edelbrock kit (mine).



In your world using only wikipedia as a source that purple line would be flat. Surely you've done a WOT log for someone, look at your manifold pressure vs rpm.

[toast]

Originally Posted by mrg666

Oh no, we are going through the same stupid arguments again. There is Honda and Koenigsegg that used Rotrex before. Search and find, I will not post links again. But you are right. Market, people like you, want instant power, muscle car response. That is why OEMs prefer positive displacement although it is less efficient, bulky, and heavy. But, I agree with one thing, positive displacement can be more dependable. I guess we are done.

Apparently it is only a stupid argument because you keep making it and are wrong.

No one said anything about muscle car response, Honda or Koenigsegg other than you. You are advising someone on a purchase and you made an incorrect statement on how a system on your own car works.

The OP should understand what the end product will feel like. I drove an ACE header 86 and then a JSRC 86 back to back and until you wind it out the JSRC feels slower under normal driving conditions. He should understand that.