If you have the time and a little ingenuity you can pull off a turbo setup for less than a blown setup.

 

Then something isn't right. My car can sit at 60 mph in 3rd gear (4000 rpm) and show 20 inches of vacuum. It's all about engine load and throttle position. In normal driving the motor never sees any boost and just tipping into the throttle a little isn't enough to do it.

You sure they had a working bypass valve on those setups?

 

Boost is not dependent on speed, it is dependent on RPM AND throttle. I could go 85 in my old T/A and not make 1psi of boost.

 

Exactly Trust, and RPM alone won't make boost either unless the bypass valve isn't working, in which case they have a serious problem and not long until the headunit goes

 

No doubt about it! I had a T70 putting boost into my 346 for well under 3Gs... But you have to be confident enough to brave the territory.

 

They don't go into boost unless your foot is in it. That is the purpose of having boost and not an all motor car. The boost is there when you want it and when not in use, it drives like stock. You must be mistaking vacuum or something.

 

It maybe that all of them are not setup right. I just know what I've seen in the different cars that I've been in. Myself I am a turbo man. I never did say anything to those that took me for a ride in there cars. But I just thought that it was one of the different things between a blower motor and a turbo motor.

Installing a turbo setup is more of a headache than installing a blower. But with a turbo you dont have to worry about the belt breakin or slipping or it causeing damage to the crank pulley and to the crank. I've seen that one before. But thats not saying that turbos are perfect. I have just seen better from turbos than blowers.

 

Personally I like turbos but I am biased. Ultimately it comes down to your budgeting preferences, wants for your car, need of power range.

 

No mistaking they was showing boost. Why? I dont know. I just know what I seen. I agree about what you said about the purpose of boost. All I can say is what I seen. But I will stick with the turbos. But that is just me.

 

That had to be one phooked up system. I have two supercharged LS motors. The fastest one (670+) shows 18" of vacuum at 75mph cruise.

 

LOL... what did the gauge show at idle? Junk gauge maybe? Definitely should NOT be in boost under very light cruise... maybe they had a heavier right foot than you thought?

 

Seems like you've made up your mind. Don't get me wrong, I love turbo setups, and had I kept the T/A I'd have changed to a KYTP setup pretty soon to change it up. Belt issues are quite annoying. However, if the crank is keyed or at least pinned and you don't over tension the belt, you're not going to damage the crank.

 

I got ya. I dont know if I can make that kind of power with out going deep into the wallet anyway. How do the stock heads on the ls1 hold up under forced induction? cam swap to think about with forced induction as well?

 

A set of 317 heads even unported will do better than the standard 241's. You can pick them up for fairly cheap, $300 or less.

Cam choice is important, probably more important than the heads. I know a guy with a forged 347 and a 3.7" pulley on his D1SC that just did about 740/666 with what a lot of people would consider a baby cam. I think it is something like 216/230 on a 117. I don't know all the details of it, just saying the right cam will make a big difference on power band and peak power.

Mine is a 224/240 .620/.600 116+4. If I had it to do again the only thing I think I'd change is the advance since it peaks a little early at 6100 and holds pretty much flat until a little past 6400 rpm.

With the right combination you can make great power without trying to max the system out, keeping your temps lower and more reliable.

 

Vac. in the teens best I can remember. It was a long time ago when these rides took place. But it might be true about the heavier foot, I don't know. But if so I know for sure I am a turbo man all the way LOL! Because that was the weakest few pounds of boost I've ever felt. Compared to a turbo.

 

sounds great i appreciate all the help. it really is making the decision a bit easier since I am now seeing all the hard facts. Thanks guys.

 

am I missing something here? As long as the supercharger is turning it is going to move some amount of air correct? You guys are talking about the supercharged setups like as if they were turbo cars. Boost in a supercharged application has nothing to do with engine load or throttle position (well not directly). It is solely based off of the rpm supercharger in correlation to the rpm of the engine (I don't know what the step up gearing is in a supercharger). In other words it takes engine rpm to make boost. That is the reason why they don't make max hp until the top end of the rpm range. Turbos are directly influenced by engine load and throttle position. They make little or no boost at cruising/part throttle conditions but the minute you upshift and put the engine under a load (lug the engine) it'll start making boost rather quickly. So in all actuality turbos drive like stock until you put your foot into it. Supercharger are going to make some amount of boost a majority of the time. (unless you are cruising at such a low rpm that your not turning the supercharger fast enough to generate positive pressure because the engine is simply using all of the air that the supercharger is making) Just my humble .2 cents

 

ta02zx10r, what you are forgetting is the bypass valve on the charge pipe which is open when the engine is pulling a vacuum. As a result all the extra air pushed by the blower is being dumped to atmosphere or recirculated depending on the setup. A motor is actually making vacuum under most conditions until the throttle blade is opened up sufficiently to allow the air to pass through the throttle body into the intake to build positive pressure.

This is why you can hold a steady speed in any gear (such as 60mph in 3rd at 4000 RPM) and not build any boost. What you get instead is a hurricane under the hood as all the air escapes through the bypass valve as the motor is actually making vacuum since the throttle blade is mostly shut.

What could be the cause of someone seeing boost while cruising is if they are referencing the boost gauge in the charge pipe instead of from the manifold. If they are getting their boost source from in front of the throttle body then yes there is going to be positive pressure in the intake pipe, but a vacuum is still in the manifold and the gauge is giving a false reading of what the motor is actually seeing.

 

good points aster I had forgot about the bypass valve on the supercharger kits.

 

Driven and ridden in two sts cars..one ls1 and one lt1. Been in and driven ati cars.
LS1 and lt1. Been in one tt ls1 car..mine..Have played with tons of turbo dsms and still have a few in the stable.Had one big block chevy roots blower car in the old days.

I always hear about initial supercharger install being easier and that might be true but once turbo is installed its installed. So what usually if it takes an extra day or two or whatever.Sts kits actually seem pretty easy install and they work ok ,they new kits look significantly improved in many key areas.
Turbos are pretty reliable if you have quality turbos, couplers, clamps,gates and blow offs.And of course belt slippage with turbo. Bigger area under the curve from turbos over centrifugals, but roots types or twin screws can also give huge areas under the curve and at even lower rpm than turbos.
Turbos are most efficient of the three thats pretty much universally recognized but in the real world all the different types have their pluses and minuses.
Centrifugals can be easier to hook up since they work thru rpm.Twin screw and roots types can cause big traction problems. So can turbos but turbos can be "ramped" pretty easily by rpm, time, gear position to name three ramping methods.

Turbos can require more complex oil and water cooling ,not a huge deal usually but blowers can be simpler in this area.

Sound wise love turbo sounds and blow offs. Roots sound good to me too. Centrifugals sound pretty good but some have annoying as hell gear rattle at idle noise that don't much care for.

Looks and intimidation hard to beat a nice polished up roots sticking thru the hood Max max style.

ATI kits are not cheap these days new. But some used out there . STS kits are also not that cheap new. Turbo kits for the f bodies come and go and I personally lost 2000 bucks few years back buying custom kit off board sponsor. So would usually stick with the bigger companies but thats my personal thing. ATI, STS been around for awhile.

You can also make up a kit from ebay stuff or whatever if you are handy ,welding is a good skill to have if you are really into fabbing in a turbo kit. But they can be done pretty cheap ,just stick to quality turbo, gate and blow off. Especially the first two.
And some decent silicone couplers and t bolt clamps.

Turbos are not overly complicated or unreliable normally. Millions of factory cars, trucks ,semis all have turbos.

Lots came out with blowers too like my favorite factory supercharged cars the grand prix gtps.

Other things to consider are oversized turbos can add al ot of lag. And to build boost off the line on a turbo car in a manual you need two step and anitlag. Antilag is not needed in auto, two step still helps. super cars of course don't need these things to build boost.
Both with centrifugal and turbo if youi are in higher gear you cans simply gear down to get more boost. Or brake boost at turbo car is another option that can work pretty good.

Going up thru the gears well then the turbo has usually advantage since it can say full spool by 3000 rpm for example and hold full boost to redline. centrifugal will make say 2 at 2000, 4 at 40000, 8 at 6000 type of thing. At the track the centrifugals seem to do very similar to the turbos though. As you can of course especially with a stick leave at high rpm to get them into higher boost quickly.

I would like to ati my 96z28 at some point in time likely with used kit.