well i want to go fi on my car. question is which one?? the car is a dd in the summer and goes into storage in the winter. i dont take it to the track but probably would a few times a year if it i had fi. just would like an awesome street monster live in a semi small town so never really get it up past 80mph. just like seat in ur pants head snapping power!! i have always liked the sound of turbos. so i was leaning that way, but was reading that turbos make power higher in the rpm band and supercharger make it lower so now im leaning towards the supercharger. then i was reading about a twin turbo setup with something called a 2 step (could someone explain )and that setup makes power down low like a supercharger. any light shed on the subject would be great and greatly appreciated. and if there is anybody that lives near erie pa with fi that would let me ride in there car to get a feel of what each feels like would be awesome
thanks in advance
bert

 

Twin turbo setup is going to be using two smaller turbos so you'll see boost at a lower RPM since it will take less to spool each one up. A single setup is going to be a lot bigger turbo to spool so you wont' see boost as soon in the RPM range. You will probably see a bit more top end power since a single turbo is usally more efficient.

 

Bert, there is alot of misconception about the comparison of turbos versus S/C's.

S/C's have the apparance of making boost lower in the rpm range versus a turbo, but thats not completely true. A S/C is belt driven so as you increase engine rpm you build boost with the blower.

Lets look at an example with say a blower at 10# of boost. I am simplifying thisso you get the picture. At 1500rpm you might make 2psi, and at 2500rpm you might make 4psi, etc. You wont make the ful 10# of boost until you spin the blower high enough for that pulley. For this example, lets say you hit the magc 10#'s at 5500rpm (linear rise in boost). People at the track love blowers because when they rev the engine up at the starting line, they are building boost while waiting to take off.

Now, a properly built turbo system will spool faster than a blower. A turbo is spooled by loading the engine. Eaxample with a turbo goes someting like this:

At 1500rpm you might not make 1/2 psi, and at 2500rpm you might make 7psi, etc. and make full 10psi by 3000rpm. So if you look at the S/C, its only around 5psi @ 3000rpm. They spool based on engine load, not engine rpm.

Now there is alot that goes into a setup (for both S/C and turbo), but I wanted o show a very simplified comparison. People think S/C's give you moe boost down low, well they do at very low rpms, buy turbos will FULL boost faster and stay there.

As far as a two step, its a rev limiter you have on at the starting line. You mash the gas pedal, the rev limiter (2 step) activates and bogs the engine, which causes the engine to fight to stay running. This loading of the engine is what causes the turbo tostart to spool and build positive manifold presure (boost) while the car is not moving. If you dont have a 2 step and just rev te engine... it wont make boost because the engine doesnt have to work that hard to free spin.

Again, this is simplified... just want you to gt the idea. BTW, you could go with a small single setupand make 700rwhp no problem... enough to take you from 0-80mph in under 6 seconds.

Jon

 

BTW, the S/C a great power adder and installs are usually pretty easy. They are pricey though, as are turbos, just depends on what you want.

 

now tell him the difference between a centrifugal supercharger and a setup like a KB or magnuson

I would but Im lazy

 

Turbos will make more power at the same boost level because there is no parasitic drag on the motor. However, the space is very limited on Fbody's and turbos require alot of piping so the install can be quite intimidating. Also superchargers are easier to tune with the stock PCM since the boost rises linearly to engine rpm. Lastly, the bigger the turbo is the longer it takes to spool up. With superchargers the power is more responsive and easier to control wheelspin.

 

I am lazy too since neither are an LT1 option

OK, here goes:

Roots charger is positive discplacement blower. The boosting occurs in the intake below the blower. Every rotation of the lobes discplaces the same amount of air everytime. Engine speed doesnt matter... 1 rev displaces xxx amount of air. This provides for instant throttle response and instant boost. These tend to heat soak quickly and boost tends to fall off in the high rpms.

Screwcharger (like KB) looks similar to a roots, but provides the lowend of the roots charger and the high end of a centrifugal charger. Its the best street charger IMO... unfortunately, nothing is available for the LT1 due to engine/cowl placement.

Simplified I know...

 

Well done



...ohhhh would it be nice to have a KB 2.8l on a LT1 with a little hose

 

Send a car off to KB with a blank check in the glove box and you can be sure they will send you back a nasty street car.

(you may want to rob a bank first)

 

well thanks for the simplified explanation really helped out so i can make 700 rwhp on a small turbo setup is there a kit out there like this or should i build my own (have some mechanical know how just not in the fi department anybody got a turbo arourd erie pa within a couple hours

 

You would need to run a T76 to make the 700rwhp mark with the LTx platform. Thee are setups out there by manufacturers:

Turbo Technologies Inc. (TTi)
Pro Turbo systems (PTS)
Squires turbo systems (STS)
Ohio Forced Inductions (OFI)

Then there are custom setups.

BTW, here is a great link showing at what rpm people are seeing full boost with their turbo kits (note that the rearmount STS setups hit peak boost later than front mount setups):

http://www.ls1tech.com/forums/showthread.php?t=772595

 

Unless you are going to invest some serious money into your motor, just get a stout, budget bottom end and throw some N20 at it. You'll get that instant low-end SOTP feel you want, minimal install hassles and easier on the motor in the long run.

Just my .02.

 

well its not something i wanted to do in a hurry. I was going to start this winter finding an lt4 block and start building it up throught next summer and maybe have it ready to put in next winter with the turbo kit but thanks for the suggestion

what would your ultimate street car have in it ?????

 

I'm excited for my new setup, and is exactly what I wanted. But the end cost was about 3X what I had imagined. A turbo is worth it, but based on how you plan on using it, it may really be over kill.

If you have a lot of patience and a BIG budget, then go for it!

 

what is ur current set up