there is a kit thats in developement and there is one guy i know of on here who has a custom kit. just run a search and you should be able to find all the info you need.

 

as far as i know, if you want lots of power, go with a Turbo but it also has a price, Turbo Lag....

if you hate lag but dont want extreme amouts of power, Supercharger but no lag.. power is there with you need it... no spooling..

now if im wrong, plz correct me

 

Lag isn't actually always a problem with turbos on the stock engine. With the high compression ratio of the engine, you still have power off boost, and with the low boost being run, the right sized turbo will spool quickly. I'm getting the AVO turbo kit from www.rallitek.com , and it has 6 psi, and all of it is available by 2k RPM. I did want a supercharger, but there really isn't anything out there unless you custom build it. There is that one kit that is being worked on, but it's been a long time since they started on it, and I have doubts as to whether it will ever see production. Look for reddevil, he built a custom SC setup for his car using a supercharger unit from a Mercedes he found in a wreckingyard.

 

yeah with a high compression motor with my old td04 I had full boost instantly. It just doesn't make sense to supercharge a four cylinder.

 

yup, i have a td04 on my stock 2.5, instant boost anytime i want it. everyone i take for rides either says it drives like a v8 or it drives like it's supercharged. point proven.

 

on a 4 cylinder motor it isn't effective to have a SC vs. a TC because SC eats power to make power (a.k.a. parasitic power loss..

 

I know I'll probably get flamed for this, but whats the difference between a turbo and a supercharger? I've always wanted to know....

 

The difference between a turbocharger and a supercharger is its power supply. Something has to supply the power to run the air compressor. In a supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust. The exhaust runs through a turbine, which in turn spins the compressor.

Both push the compressed air into the intake and create "boost"; this in turn gives you more powah!!

 

yeah with a high compression motor with my old td04 I had full boost instantly. It just doesn't make sense to supercharge a four cylinder.

It does make sense, depending on the application. If you are keeping the stock compression and won't be running much boost, then it doesn't make sense to supercharge because a properly sized turbo will act exactly like a supercharger anyway.

But if you were lowering the compression, and running alot of boost (say 18+), with a twin screw supercharger it does make sense; provided you make a design that can be intercooled. But price, difficulty, and the fact that it has to be custom has made alot of people go turbo because its alot easier. I'm a person who absolutely will not put up with lag, I really hate driving my g/fs WRX even if it is faster because the throttle response is so slow compared to my RS. So I am going to do the lower compression/custom supercharger route. My goal is 20 psi with a STI Shortblock and a hydra.

If you are only going to run low boost or you think supercharging costs too much or is too hard to do, definitely go with the turbo.

 

on a 4 cylinder motor it isn't effective to have a SC vs. a TC because SC eats power to make power (a.k.a. parasitic power loss..

Turbo's eat power to make power too, the energy has to come from somewhere. If you think it isn't eating power to work against 12-36 psi of back pressure then you have some research to do. Pressure ratios of the turbo's change, changing your exhaust can change what presure ratios the turbo hits. But when I do my calculations I assume that a turbo is working near a pressure ratio of 2. For those of you that don't know, at a pressure ratio of 2, multiply your boost number by 2 and you get what your back pressure is.

Most of the time when people talk about Parasitic Loss, they are talking about the drain that the supercharger has off boost. This is especially true with superchargers that have internal compression (twin-screw and centrifugal), but with a properly installed bypass valve this is pretty much eliminated.

 

Turbo's eat power to make power too, the energy has to come from somewhere. If you think it isn't eating power to work against 12-36 psi of back pressure then you have some research to do. Pressure ratios of the turbo's change, changing your exhaust can change what presure ratios the turbo hits. But when I do my calculations I assume that a turbo is working near a pressure ratio of 2. For those of you that don't know, at a pressure ratio of 2, multiply your boost number by 2 and you get what your back pressure is.

Most of the time when people talk about Parasitic Loss, they are talking about the drain that the supercharger has off boost. This is especially true with superchargers that have internal compression (twin-screw and centrifugal), but with a properly installed bypass valve this is pretty much eliminated.

Why do you assume your PR is near 2:1? That is a very inificient setup IMHO. Im still fairly new to subaru setups, however turbocharging and its theories should apply the same.

What benifits are you after that require you to run such a high ratio

 

It does make sense, depending on the application. If you are keeping the stock compression and won't be running much boost, then it doesn't make sense to supercharge because a properly sized turbo will act exactly like a supercharger anyway.

But if you were lowering the compression, and running alot of boost (say 18+), with a twin screw supercharger it does make sense; provided you make a design that can be intercooled. But price, difficulty, and the fact that it has to be custom has made alot of people go turbo because its alot easier. I'm a person who absolutely will not put up with lag, I really hate driving my g/fs WRX even if it is faster because the throttle response is so slow compared to my RS. So I am going to do the lower compression/custom supercharger route. My goal is 20 psi with a STI Shortblock and a hydra.

If you are only going to run low boost or you think supercharging costs too much or is too hard to do, definitely go with the turbo.

Thats exactly my point. If you want to spend triple the price of going super ovre a turbo then go for it, I would want to see that. Good luck with that

 

The difference between a turbocharger and a supercharger is its power supply. Something has to supply the power to run the air compressor. In a supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust. The exhaust runs through a turbine, which in turn spins the compressor.

Both push the compressed air into the intake and create "boost"; this in turn gives you more powah!!

Thanks, I appreciate the answer!!

 

Why do you assume your PR is near 2:1? That is a very inificient setup IMHO. Im still fairly new to subaru setups, however turbocharging and its theories should apply the same.

What benifits are you after that require you to run such a high ratio

Well, take this compressor map for example.

This is a relatively small turbo (GT28R series) that should give you 6 psi on a 2.5L right around 2000 rpms. From that image, a PR of 2:1 isn't very high on the map. Infact the turbo can almost get to a PR of 3:1. Now if I mapped the air flow required to get 6 psi out of it on a 2.5L it would probably be below a PR of 2, I won't know unless I do all the calculations. Mostly I used the PR of 2:1 as an example as it seems to be in the middle of most smaller turbo's efficiency ranges.

My point is that alot of people claim that the boost from a turbo is from "waste energy" and that it causes no loss in power from the engine. The fact is that it is really easy to measure the drain from a supercharger (spin it to a certain rpm and measure how much torque it takes at whatever boost level), but no one has hooked up a turbo to a dyno'd N/A engine and measured the loss at certain pressure ratios. You could probably just make a manifold with a valve on it and control how much exhaust gets through to change the backpressure.

In either case, Turbo or Supercharged, they both make more power than they consume. The only real difference is how you want your powerband, what kind of throttle response you want, and Price.

 

I think it's also important to consider efficiency. As Master points out, all FI creates more power than it uses, but to the best of my knowledge, most turbos are more efficient than most SCs in this process. This means that more of the power that's taken from the engine is turned in to boost instead of heat.

I think I remember reading that most SCs sit around 40-50% while most turbos sit around 60-70% ... although I think the SC that's going into the kit that is being developed is closer to the 70% range.

 

Well, take this compressor map for example.

This is a relatively small turbo (GT28R series) that should give you 6 psi on a 2.5L right around 2000 rpms. From that image, a PR of 2:1 isn't very high on the map. Infact the turbo can almost get to a PR of 3:1. Now if I mapped the air flow required to get 6 psi out of it on a 2.5L it would probably be below a PR of 2, I won't know unless I do all the calculations. Mostly I used the PR of 2:1 as an example as it seems to be in the middle of most smaller turbo's efficiency ranges.

Oh, what i was refering to was when we were talking about exhaust backpressure pressure ratio's, and i thought the 2:1 was an exhaust to compressor side pr, of which 2:1 is pretty bad.

what do you use for VE when caluclating. and by anychace do you have a ve plot for a rs-t or a stock rs etc? i have been trying to put one together but cannot find everytying i need from one car


as for measuring power required to run a turbocharger. this is the forumla i was givin one day

HP = ((CID / 2 / 1728 x Manifold Density x RPM / Numberofturbo's) X VE ) x (1545 x 1 x (intakeTempF + 459.6) / (29 x egt's) x (compressor PR ^ (1/(1/0.288))-1)) / (compressor eff x 33000)

if i feel modivated il put that in a spreadsheet

 

I think it's also important to consider efficiency. As Master points out, all FI creates more power than it uses, but to the best of my knowledge, most turbos are more efficient than most SCs in this process. This means that more of the power that's taken from the engine is turned in to boost instead of heat.

I think I remember reading that most SCs sit around 40-50% while most turbos sit around 60-70% ... although I think the SC that's going into the kit that is being developed is closer to the 70% range.

everything ive ever read points the same way. However newer centrifugal superchargers are much much more efficient than previous superchargers.

A couple of years ago a guy from Philly was developing a turbo or centricugal supercharger that made use of the telsa bladeless turbine technologie and that had efficiencies of high 80's and possible 90's, however with pattent problems.. he disipeared