Paging jon K, super question

[Jon K]

All supercharger brackets attach via alternator attach bolts. you need longer than stock alternator bolts and lots of miscellaneous **** - it's not fun.



Anything is possible

You guys are saying CF blowers aren't good - etc, but what they do is make power reliably. There is no guessing whats going to happen at 4k rpm - the engine picks up linearly and all is well.

Roots blowers can be somewhat unpredictable. They're always making boost so when you first rev it up theres a instant "shock" to the motor that has the same effect when shifting sometimes... its a noticeable difference from a CF.

A twinscrew is the least "noticeable" setup. The rotors spin compressing the air - the rotors are often coated with teflon and have like .001" of gap. The rotors DO wear, and need to be refinished eventually. There are several makes of twinscrews...eaton makes on and whipple makes one. The power band on a twinscrew is much different than on a CF or Roots. The TS blower acts like a larger motor. The torque curve is the flattest thing - people often think you're dynoing a large V8 when dyno'ing a L6 with a TS.

The only downside to a twin screw is that it replaces the intake manifold. This means there is no room for an intercooler. Some kits replace the intake manifold with an inline air to water intercooler - some don't. Some people have been successful fitting the Eaton blower from mercedes c230 kompressor motors into BMW 318's (e30). However, it doesn't mount on the head like that, but rather ghetto all over the place with plates that convert the direct runner into a collector etc.

A lot of VW guys use Lysolm or Autorotor kits. They were so badly they only get about 6k miles before the blower is leaking boost inside to outside. You can see in the above picture how "unbulky" the actual main body of a twin screw is. All the seams are prone to opening.

The kit pictures above is the Eurosport kit, which sells for about $7,000 uninstalled. It replaces intake manifold including the fuel ports. Is it worth it? Max power out of them tends to be a little lower than CF units, however CF units only make their peak power at peak RPM. I am turning 9 psi @ 6500rpm. I have a max of 7200 RPM rev limiter which would be well over 10 psi - 11psi. The twin screws are only running 6 or 7 psi, but its constant. The power is everywhere and not just up top like a CF unit. Some people like that, but i actually prefer getting kicked in the butt at 5000 rpm.


Also! The unit you pictured in the first post is a Powerdyne unit originally used by Dinan and some RMS kits. These blowers are HORRIBLE. If you find one on ebay, run. You can see the buldge on the front of the unit - that is the drive belt. There is an internal belt in there that links one wheel to another, so the turbine spins. This belt breaks OFTEN. It's a real pain and generally not efficient as they leak boost out all of the orifices etc. I am using the ASA supercharger... its internally geared 15:1 compressor:drive pulley. Geared superchargers are MUCH preferred over belts - there wont be a chance of a belt breaking.

My blower:



By the way, if you are doing an M3 crank in a 2.5 block you need 3.0 or 3.2 rods as I recall... which is kind of a bump in the wrong direction if you have a NON VANOS motor.




Oh one more thing... about the remote mounting of the twin screw. ALL the pressure on the blower will be at the pulley, so with a long neck, the TS has a dendency to dip if mounted on a bracket. This causes angle at the pulley and throws belts a lot. Ask any 318 owner with the eaton setup. the manifold replacement method is much more sound. I only threw a belt once, and it was when I was pissed off.

One more edit: TS set is making 350 hp on OBDII 3.2L M3. There are CF guys making over 450hp. The TS kit is also $8500, not $7k as previously stated... and thats $8500 uninstalled.

[Jon K]

Rob101,

I just also saw you questioning the twin charging setup. I am going to be running 11 psi on the CF blower by 7200 rpm. That means about 6 psi at 5k rpm. The turbo is a Garrett T-66 from a single turbo supra. Read: LAG. I know CFs make power high, but not nearly as high as the turbo is going to I want it more for show than practicality obviously - but the large turbo is going move huge CFM.

BigKriss,

As for the question of 14 psi on 9.0:1 CR. That image you linked is somewhat ridicluous. I am not sure how they're assuming those figures of efficiency. All I know is my friend is running a 2.8L M52 on 9.0:1 and 22 psi of boost for 635rwhp... good enough for my blood.

[BigKriss]

BigKriss,

As for the question of 14 psi on 9.0:1 CR. That image you linked is somewhat ridicluous. I am not sure how they're assuming those figures of efficiency. All I know is my friend is running a 2.8L M52 on 9.0:1 and 22 psi of boost for 635rwhp... good enough for my blood.

The graph was taken from Forced Induction - Performance Tuning by Graham Bell. "It specificlaly applies to turbos and centrifugal blowers.....which is reasonably safe for 4 valve engines with digital electronic injection and ignition at 98 RON fuel." An intercooler operating at 100% efficiency means that the temperature of the intake charge leaving the compressor is at ambient (outside) temperature.

[rob101]

thanks for your input jon, yeah not sure at this point what pistons / rods/ crank, i would use for a stroker, might even go a custom H-beam rod if i was doing FI. but yeah I am still doing my homework... keep in mind we have the 3.2L s50 as well so that may be the preferred option, i'll have to look at cost, may just opt for a stroker without FI. but i really like the stroker idea especially since s50 engines will be expensive to find in australia

[emw525E34]

Yeah, but there is no such thing as a 100% efficient intercooler. So one tops out at 70% and steals a couple of PSI in the process. People can boost all the way to 25 PSI but that cannot be sustained for long without damage.

Old school Altimas running to 25-30 PSI lasts for a few days then a huge blow-out. Old track-mate's dad blew two of these suckers ....

[Jon K]

There is no problem with running 30 psi as long as your headgasket will physically hold it and your fuel situation keeps it from detonating and you have sufficient charge cooling. Running 30 psi isn't like running 10 psi. You set your fuel up for like 10:1 - 10.5:1 afr so as to cool the cylinder. This rich will steal power but you make up for it in pressure. If you want to run leaner you just injector alcohol through the throttle body. If you know what you're doing it is not that hard.

[bjl4776]

For all of the work of a TS i dont see what a turbo doesnt seem like a feasible option. If you put two small turbos, like t28s or so you will be making your 6-10psi at around 2500rpm and hold that through redline, plus it is easy to make more or less boost with this application. Any supercharger isnt going to make peak power until peak rpm because of the princable of it. A turbo lets out excess exhaust gas to prevent it form boosting higher through a wastegate. The only way to make a supercharger do that is with some sort of clutch that is actuated by boost pressure, which i havent seen around. Any kind of forced induction is positive displacement, as rpm goes up, the amount of air it can pump goes up, doesnt matter if its turbo TS, or CF. Personally I would never go with any kind of mechanical forced induction. You cant vary boost pressure, they aren't as efficienct, they dont hit peak power till peak rpm, and mileage is reduced more than that of turbo, it takes more HP to run a s/c than a turbo.

[Jon K]

For all of the work of a TS i dont see what a turbo doesnt seem like a feasible option. If you put two small turbos, like t28s or so you will be making your 6-10psi at around 2500rpm and hold that through redline, plus it is easy to make more or less boost with this application. Any supercharger isnt going to make peak power until peak rpm because of the princable of it. A turbo lets out excess exhaust gas to prevent it form boosting higher through a wastegate. The only way to make a supercharger do that is with some sort of clutch that is actuated by boost pressure, which i havent seen around. Any kind of forced induction is positive displacement, as rpm goes up, the amount of air it can pump goes up, doesnt matter if its turbo TS, or CF. Personally I would never go with any kind of mechanical forced induction. You cant vary boost pressure, they aren't as efficienct, they dont hit peak power till peak rpm, and mileage is reduced more than that of turbo, it takes more HP to run a s/c than a turbo.

That's why I decided to run both I need to talk to you sometime about picking up the motor man. Give me a call 267 980 2625