So Very Supercharged

[NCTaurusSHO]

well.. we aren't really sure if they are stage two actually. bought them from a guy who had the pp heads with the cams already installed and shimmed up. he said they were 3.2 heads with stage one cams, but it is pretty lumpy, and others on the forum suspected they might be 2's after hearing them in a video. I thought maybe he got his facts wrong because they were actually 3.0 heads. so not sure about that however.

 

[NotSoSlowSHO]

careful about smaller pulleys on the M90.

The temps of the compressed air will go thru the roof, and the M90 will self destruct if overspun. With the factory GTP pulley on my M90 boosted SHO, the blower will see redline just as the motor does.

Putting smaller pulley on the blower will result in overspinning it, if you take the motor all the way to redline.

HOWEVER, a properly ported M90 will drastically lower outlet temps, and make the blower much more effient at high revs.

 

[NCTaurusSHO]

i thought the whole difference b/w the roots (positive displacement/fixed displacement) and the centrifugal superchargers was that the roots doesn't compress the air and the other does, it just moves the air more quickly. isn't that what positive displacement is? a fixed amout of air at each RPM...but not compressed air, just faster moving air. the charger came off a supercoupe with the smaller pully on it. I don't think there were problems. we happend to have 2 superchargers one with the smaller pulley and one with out. if i need to run an intercooler I have that too. -ashley-

 

[TedB]

. . . isn't that what positive displacement is? a fixed amout of air at each RPM...but not compressed air, just faster moving air.

No. Only the engine speed (with respect to VE) determines the rate of airflow. Superchargers and turbos only increase air density.

Positive displacement and centrifugal superchargers are both compressors, but work on different principles, and induce compression by different means.

 

[Off Road SHO]

Positive displacement and centrifugal superchargers are both compressors, but work on different principles, and induce compression by different means.

Well maybe a twin screw positive displacement supercharger is a compressor, but not the Roots style Eaton that they're using. All Roots style blowers are just air pumps, they do not compress the air, they just move it. If there is a restriction in the output side of the blower, say a 500 cc cylinder, then yes the air outside of the compressor (for the most part) in the piping and cylinder will be at a higher pressure.

The nice thing about ALL positive displacement blowers is that they are "right now". Not as soon as the turbine blade spins up, but right now. It's a great feeling, sort of like cubic inches.

Tom

 

[TedB]

All Roots style blowers are just air pumps, they do not compress the air, they just move it.

This is incorrect. ALL PD pumps create pressure if they move more material than can be accepted by the receiving end. A (sufficiently sized) roots style blower moves a greater volume of air than engine can accept. This results in pressure in the intake, which increases air density (sounds familiar?). This is where the extra power results. Don't take my word for it, put a pressure gauge on the manifold and watch it move past "0". Or, ask yourself why a 12lb pulley for a specific roots blower with a specific application is called a "12 lb pulley". 12lb =~ 12 psi.

Only the engine speed with respect to VE determines the actual volume of air being used. Turbos, blowers, etc., don't change volumetric airflow, only mass airflow.

The on-tap power that comes with a PD compressor results because the compressor creates an effective seal (unlike a turbo or other centrifugal device). This enables it to build pressure at very low speeds, and this pressure is built fairly linearly with respect to rpm.

 

[twr]

Tom, if it's an air pump... doesn't that make it a compressor?? I mean, to move air from point A to point B there needs to be a pressure difference, no? I know the twin screw setup is superior to the roots setup as far as adiabatic and volumetric efficiencies, but the principle is the same.

OT: I need to tag along with Jason to Arizona one of these days, tired of hearing him jabber on about the other woman.

 

[NCTaurusSHO]

but the pressure isn't being made inside the supercharger on a roots style. it is on the other side- in the piping itself. there isn't a chamber where the air is being compressed. the inside of a roots just moves it from point a to b then is pressurized inside the piping on the other end right-however, not inside the supercharger itself. I mean I guess technically were all kind of right. haha. what a long discussion this has become!!!! it's kinda like school. yay! -ashley-

 

[TedB]

Where the pressure is made (manifold or tubing) depends on how/where the unit is mounted with respect to the engine, but that isn't really significant for the sake of discussion. Roots blowers, centrifugal blowers, and turbos all make power by strictly increasing the density of air the engine consumes, not the volume. What makes a PD device like a roots blower different lies primarily in the fact that once air enters, there is no way back. This is why a roots equipped engine delivers off-idle boost - it creates positive manifold pressure at any rotational speed.

The volume of air used by an engine is determined by swept displacement, and only way to make the engine use a greater volume of air without altering the displacement is to make it more volumetrically efficient (e.g. bigger cams, better exhaust, intake, etc.) and spin it faster.

 

[SeanMc]

I believe texantony's monster has stage 2 cams. Not sure if the vortech he has is a PD blower though.

 

[NCTaurusSHO]

Where the pressure is made (manifold or tubing) depends on how/where the unit is mounted with respect to the engine, but that isn't really significant for the sake of discussion. Roots blowers, centrifugal blowers, and turbos all make power by strictly increasing the density of air the engine consumes, not the volume. What makes a PD device like a roots blower different lies primarily in the fact that once air enters, there is no way back. This is why a roots equipped engine delivers off-idle boost - it creates positive manifold pressure at any rotational speed.

The volume of air used by an engine is determined by swept displacement, and only way to make the engine use a greater volume of air without altering the displacement is to make it more volumetrically efficient (e.g. bigger cams, better exhaust, intake, etc.) and spin it faster.

(Lets say..for now... i was putting these mods on a N/A motor with a supercharger ) Adding cams, ported heads and intake runners on a N/A motor with a postitive displacement supercharger is shown to reduce the nuber of lbs.that a blower produces by about 2-4lbs. However, it does up the volumetric efficiency of the motor itself, which reduces the superchargers need to move air into the engine (doesn't have to work as hard) In turn, there are very positive results to be seen as long as you are able to bring your boost numbers back by making the supercharger spin faster than the crankshaft and to what it was originally without the mods...whether it be with a pully or other means. When we try it with this larger pully on first, if it does seem to fall flat after 4000K then we have a 10% pulley capable of 3-4lbs. more of boost. that should bring the supercharger to the speed that we need it. if not, then we'll get an even smaller one. -ashley-

I did say that... right? haha

 

[Lupo]

I believe texantony's monster has stage 2 cams. Not sure if the vortech he has is a PD blower though.

All Votechs are centrifugal.
A PD (positive displacement) blower pretty much moves the same amount of air per turn at any speed, hence the "linear" power output.

The output of a centrifugal blower, or turbo increase exponentially as RPMs increase, for example:
One turn at 1K RPM may move "X" amount of air.
At 40K RPM, one turn will move 20X the amount of air.

The centrifugal forces (which actually move the air) increase as impeller speed increases. This is what produces that non-linear exponential output you see for centrifugal blowers and turbos. Not a lot on the low end, but a TON on the high end.

 

[Mike Kopstain]

True, though there are still many key differences between the two calibrations that will keep the Supercoupe PCM from running optimally on a foreign V6 SHO configuration. What's more is that you will eventually need to retune the PCM (whether it be from the Supercoupe or the SHO) to achieve optimum mileage and maximum peformance from the entire setup.

OTOH, I definitely applaud you guys for both your ingenuity and your creativity. Keep up the great work!

Proving once again that not only am I capable of being wrong but I most like AM! :laugh_ti:

 

[Shoman594]

Ashley, Just wanted to ring in and say the project looks great! I saw you and the turbo car at the convention. Who was the guy with you?

Any way congrats on both cars, cant wait to see what happens with them.

 

[NCTaurusSHO]

haha he is my fiance. (it was his turbo sho).... thanks though about both.... mine will be the supercharged one. we got most of it finished last night ( the piping and everything) we are waiting for the bypass valve to show up, still. so that will be most of it. we are gonna do a video of the whole build up and the end result so keep on the look out for that. thanks again though -ashley-

 

[Off Road SHO]

OT: I need to tag along with Jason to Arizona one of these days, tired of hearing him jabber on about the other woman.

Bring it Terry. We can go dig some ruts out in the desert with The Other Woman.

Tom

 

[shogansta]

NCTaurusSHO i cant wait for the write up for this mod!! i have been following your posts from day one and i think that for doing all these mods you are incredible! your like the superman errr supergirl of sho's!!!!

 

[NCTaurusSHO]

we're both... he's the superman and I am the supergirl... wow.. that sounded dumb. haha... sweet. -ashley-

 

[pudge235]

these ppl are the best. they are by far the most innovative ppl on the forum right now. i love there ideas and deff love there level of enthusiasm and love for modifying these cars. hopefully soon enough i will be boosted with there help and knowledge. by the way awsome project cant waqit to see the outcome.

 

[Minnesho]

Very cool, so where did you get the custom jackshaft? and what are you going to do about the fan?