supercharging z31

[titaniumbmx]

now i have a paxton charger... and an 85 z31... what now

[mario_82_ZXT]

use it as a hat??

 

lol... i don't know sorry....

 

Cut the intake manifold and put it on the top and get a custom hood and pulley?

 

We're gonna need more info... or use your skillz...

Mario

[titaniumbmx]

my brain could use the boost...

its a stand alone doesnt mount to the intake.

[veritech-z]

So it's centrifugal then? Sounds like it's time to build a bracket...How bad do you need that A/C compressor?

[titaniumbmx]

im three steps ahead of you... i've got the whole a/c system out allready:burnout:

[veritech-z]

I'd say it's time to get under there and see what fits...then wrap a string to see in inches how long of a belt you need, and take a trip down to the auto parts store and git r dun, right? From there you should just have to build a bracket that ensures your belt will line up just so, run some plumbing, and hope that your ecu or FPR will compensate for the boost, or run some electronics to do that for you.

 

*edit* Also, is the pulley on your supercharger the same amount of teeth as the rest of your accessory drive system, or does it use a wider belt? You might need to play some games with that if they aren't already the same...

[mtcookson]

Oh man... a centrifugal s/c is the last type of forced induction I'd use on a Z... especially since you can do a turbo setup rather easily.

 

They may be very efficient... but you still have parasitic losses and you don't reach peak boost till redline, period. That's the killer. A turbo is nearly as efficient, compressor wise, doesn't have the parasitic losses that using a belt does, and has much quicker boost response... peak boost comes on much sooner.

 

Basically you'll make more power all around with a turbo than with a centrifugal s/c. If it were a roots... maybe... I'd still go with a turbo over a roots. If it were a screws, I'd say go for it. A turbo is still a bit more efficient but a screws is still extremely efficient and gives instant boost. I'd still choose a turbo over a screws as well but of the superchargers, I believe the screws is the best.

[Guest ZFury]

You will loose more hp from a turboC not a superC. And when you get peek boost all matters on your pully sizes.

 

 

You gotta' post picks of this. I so wanted to swap out my AC for one of these in my ZX.

[tfreer85]

You will loose more hp from a turboC not a superC. And when you get peek boost all matters on your pully sizes.

Do you have any theory behind that or just saying it? With an SC what is the direct corralation for it to produce boost? ENGINE SPEED (RPM) therefore peak boost does not occur until the engine is at peak RPM. There is a direct effect there. Pulley sizes merely change the amount of boost that the SC is creating, not necessarily WHEN.

An example for a street driven car (since that is what most of our applicatoins are): 7 PSI on an SC is not the Same as 7 PSI on a turbo, when you factor in parasitic losses (the loss of power to create power). An SC is creates drag on the front of the cranksaft to spin to the RPM to create that 7 PSI, according to Engine Masters that drag comes at a cost of an average of 15% of the power created. Therefore 7 PSI boost may be the same 7 PSI for a turbo, but is only creating the amount of POWER a Turbo would produce at 5.95 PSI due to the parasitic loss. One more thing to consider with an SC is the stresses that its going to put on the front of the engine: wearing out front main bearings quicker and even shearing off the front of the crankshaft, along with other problems to engine harmonics due to the stresses on the front of the engine.

 

The only major downfall of a Turbo is the amount of heat it produces in the engine bay. However with a properly designed and setup Turbo system this can be minimized. A turbo functions off of wasted gasses from the engine and has NO parasictic drag directly on the engine.

 

So please, please explain to me how you loose more power through a Turbo than an SC in a street driven car. And dont argue drag/race cars as to why they are better, because race cars are COMPLETELY different ball games.

 

Tyson

[TheNeedForZ]

You will loose more hp from a turboC not a superC

 

(shakes head) SC uses crankshaft power, turbo uses exhaust power which is originally "wasted". Generally 30 out of 100 hp gained by SC is wasted compared to 5~10 hp loss per 100hp gained by Turbo.

[titaniumbmx]

good points everyone im going to first bulletproof my bottom end and do the heads and intake w/90 mm throttle body from q45 im under the impression that i can change pulley setups depending on what im aiming for. like a bike gear setup the the larger the pully i put on the charger the easier it will be on drag but it will produce less boost do to the rpm change right... i'll play with it to see what works best. all your input is appreciated and i'll listen to all that you guys give. thanks guys

[Guest ZFury]

Reason for more HP loss from a TC is because it inhibits the exhaust flow. (which is a big inhibiter) Surely by this stage we all know to get bigger exhaust to free up the exhaust flow. So if you stick a turbo in that exhaust pipe you are just restricting the flow. Plus the heat from your glowing headers are transfered directly to your intake, heating all that compressed air. Both SC's & TC's air flow increases when the RPMs increase. The exhuased being pushed out of the motor forces the turbine to spin on a TC. The spin of the crank spins a SC. So lets say your peek allowed intake pressure is 10psi. You can set up your SC to create that 10psi of pressure at idle if you want (if your SC can withstand high RPMs) using different pully sizes. But with a TC you will always have to rely on the exhaust flow to spin the turbine, which can not create that kind of pressure off of low RPM exhaust flow. And as for throwing the crank off. Your crank doesnt hover in the block, so putting a small pully wheel at the end to spin a small SC should not cause a problem. You can remove the fan and replace the load with a SC :::shruggs:::. The only advantage i ever knew a TC to have was the size. You could tuck a TC in easier than a SC at one time. But now they have vortec SC and smaller SC.

[tfreer85]

Okay, I see some of your points, however hardly any Turbocharged cars these days run without an intercooler, so that air is not directly put into the intake manifold. What do you think an SC does to create that Boost pressure? Unless its a centri, it has two or three screws creating FRICTION which equals HEAT directly on top of the block! The little squished intercoolers that you put between them are far less than sufficient to cool the intake temperature. So then your putting large amounts of heat directly into the engine with an SC. Centri SC's are the only SC's that can get around this by being able to run an FMIC.

 

Your headers are going to glow no matter what SC or Turbo, that is inherent in the type of metals used in headers and the extreme heat produced by the combustion. As to the restriction on the exhaust, have you ever played around with a turbo in your hand, have you seen how easily they spin? Most of a turbos power comes from the heat energy, not necessarily from the pressure of the exhaust. While yes it is true the exhaust won't flow as well on an N/A or SC setup, but it does not have near the same amount of parasitic loss that the SC creates.

 

Yes a turbo creating pressure is related to exhaust gases which is related to engine speed. When do most turbo guys say they get full boost? Anywhere from 2500-3500 depending on turbo size etc., so that means that the only time really in which the SC is creating more power or boost is below 3500 RPM in LARGE turbo applications. At that 3500 RPM the amount of PSI that the turbo can produce can FAR exceed that of a SC at the same RPM.

 

No, your crank doesn't just float in the block, but that does not dis-credit the fact that stresses are being put on the front of it by installing an SC. A fan on the front of the crank IS NOT the same amount of stress being put there. The fan turns in a circle and has no linear force being applied to it. Put an SC pulley on the crank sure turns in a circle as well, however it must power another pulley on the SC itself which creates large amounts stress on the crank.

 

Sure with the proper pulley setup you can get your SC to idle at 10 PSI, but you AREN'T creating a true 10 PSI of POWER!! Why, because of the parasitic losses that I've talked about before. You can't reap the benefits of 100% efficiency of creating power if you must take 15% of that power to create that power. Another benefit to the turbo is the fact that it can function at a higher rate of efficiency for creating that 10 PSI of power. Vortec and similar centri Style SC's are by far the worst SC's for creating PSI in the lower RPM range. They are essentially belt driven turbos, that can produce more PSI than a roots, but not until the HIGH RPM range, more times than not HIGHER RPMs than a turbo spools at!

 

I like SC's in some applications, but dollar for dollar to create MAX HP the turbo wins everytime in my book. They are too efficient at creating that power easily.

 

Tyson

[Guest ZFury]

I cant argue with that. But its all wrong.

[tfreer85]

I cant argue with that. But its all wrong.

HOW? Read Corkey Bells Maximum Boost, Read Engine Masters Magazine about SC's, read Sunnen's Complete Engine and Cylinder Head Rebuild Handbook. Please argue your point prove me wrong or pick it apart my argument or HOW its wrong. Don't just say it is wrong and NOT back it up, you aren't making your case very well for SC people reading this.

Also don't take this as an attack on you its not, I'm open for any arguing as to why the SC's "better" than the Turbo.

 

Tyson

[Guest ZFury]

The SC you are refering to in the 1rst paragraph is not the same as the one I posted a pic of before. Those that you are refering to do create heat (like all chargers), but no SC creates more heat than a TC. (Your exhaust heads will creat much more heat than anything else on the car, and that heat goes directly to the compressor of the TC.... now back to my point) But as you can see below you can not put an intercooler/or large inter cooler in one of these types of SC.

it connects directly to the intake manifold, it is almost part of the manifold. So not being able to use a intercooler on one of these is a minus. Now you would have to argue if the intake temp is cooler from a SC with no IC that creats less heat, or from a hot TC with an intercooler. Probably all just depends on your set up. BUT! the SC I posted a pic of before does not connect to the intake manifold in this way (nor does a vortec SC) and can have an intercooler installed in the same way a TC can. So your intake temps could/would/should be much lower than a TC's intake temps.

 

Now as for the exhaust part of the TC. Your TC is not powered by heat, it is powered by the air being forced out of the motor. That air is pushed through a turbine that spins a compressor. If you have ever seen a turbine you can see that it has a little small passage ways for the air to pass through over the fins to spin it. Even though it spins easily the amount of volume/space for the air to pass through is lessened, for if it wasnt you could not spin the turbine. That = a loss in HP, more of a loss than the small load on the crank fram a small SC. So as for the "true HP"... both TC's & SC's take a little hp to make hp, and the SC uses less.

 

Now as for the "Full Boost". if you read and understand what I wrote in the post before you will understand how a SC can create "full boost" before a TC can. And can sustain that boost all the way through the RPM range if set up in that away.

 

And as for the pull on the crank. Many fans are belt driven, just as is the power steering, altenator, & AC. Removing one and using it to power a SC would not cause any problems. Adding a pully if done correctly shouldnt be much more stress on the crank bearing.

[tfreer85]

AWESOME!!! THANK YOU FOR THE IN DETAIL RESPONSE!!! All very good points. I think you mis-understood me when I said the TC doesn't run off exhaust pressure, it does like what you are saying but it also gets power from the heat generated by the exhaust gasses. Also, there are water-to-air intercoolers that can squish between the SC like you showed the picture of. Yes both TC's and SC's take little power to make power, but it has been my understanding in my readings that the Turbo requires LESS.

 

I agree with you that a SC can make more boost in the lower RPM before a turbo spools and hits its maximum boost. However, after you get past the 2500-3500 RPM range the turbo can make MORE boost which equals more power than what the SC can.

 

If an SC is propely setup like you are saying the frontal crank load SHOULD be minimized (but it is still there), however this is rarely taken in to consideration or design with backyard mechanics. It is something that most people don't realize, so I figured I'd make a point of it.

 

I would recommend an SC for a car that can only handle 6-12 PSI of boost, but if your motor can handle more PSI then I'd recommend the Turbo because they turbo can produce more PSI which means more power. As for intake temperatures, its like you said it depends on your setup. Thanks for the argument and backing up your standpoint!!

 

Tyson

[veritech-z]

http://i3.tinypic.com/11awbw2.jpg

Out of curiosity, what is supposed to bolt to the bottom of that roots style blower if not the lower intake manifold? Some other kind of plenum that funnels the air into that intake tube? That looks like it cam off of a thunderbird super-coupe, and I'm pretty sure they also had their roots blowers mounted in the standard way....I read AND understood what you posted to mean that you do NOT in fact realize what it is you are trying to say about superchargers reaching "full" boost before turbochargers. If the maximum allowable boost is 10psi, and you set your supercharger to make 10psi at idle, you have just set the STARTING psi of your system, which will then increas as a function of pulley ratio until maximum engine rpm is reached in a LINEAR way, making the engine feel like it is just a larger displacement NA motor (that's why these blowers are called positive displacement blowers) unless you then incorporate some kind of wastegate or pop-off valve to vent out the extra boost you don't need. A boost gauge in a supercharged car would give you a better picture of how superchargers make boost, but they do not just make one preset psi and carry that throughout the rpm range. Also, if turbos get so inefficient from exhaust heat, how would you explain intercoolers that are able to get charge temperatures back down to ambient air for air/air, or even lower than ambient in the case of water/air?

[mtcookson]

You will loose more hp from a turboC not a superC. And when you get peek boost all matters on your pully sizes.

 

-----------------

 

Reason for more HP loss from a TC is because it inhibits the exhaust flow. (which is a big inhibiter) Surely by this stage we all know to get bigger exhaust to free up the exhaust flow. So if you stick a turbo in that exhaust pipe you are just restricting the flow. Plus the heat from your glowing headers are transfered directly to your intake' date=' heating all that compressed air. Both SC's & TC's air flow increases when the RPMs increase. The exhuased being pushed out of the motor forces the turbine to spin on a TC. The spin of the crank spins a SC. So lets say your peek allowed intake pressure is 10psi. You can set up your SC to create that 10psi of pressure at idle if you want (if your SC can withstand high RPMs) using different pully sizes. But with a TC you will always have to rely on the exhaust flow to spin the turbine, which can not create that kind of pressure off of low RPM exhaust flow. And as for throwing the crank off. Your crank doesnt hover in the block, so putting a small pully wheel at the end to spin a small SC should not cause a problem. You can remove the fan and replace the load with a SC :::shruggs:::. The only advantage i ever knew a TC to have was the size. You could tuck a TC in easier than a SC at one time. But now they have vortec SC and smaller SC.[/quote']

 

 

Negative... totally incorrect on nearly all accounts.

 

You will lose more power powering a supercharger than you will a turbocharger... fact. The only time you'd be correct in that you would lose more power with a turbocharger is if the turbo being used was grossly too small for the engine either due to simple stupidity of the person who put it on, lack of turbocharging knowledge, or simple confusion.

 

Heat from the headers... I've seen normally aspirated engines make the manifolds glow red. Yes, that will decrease power. No, a turbo isn't the only thing that will cause immense heat. If you're having heat problems like that you need to coat or wrap your manifolds to retain the heat and best yet get them made with the proper material (321 stainless steel, which can be expensive but is one of the best materials for high temp exhaust next to inconel). From there you could go further and coat the 321 but wouldn't be as necessary as when using standard steel, lower quality stainless, or cast.

 

From there you can use an aftercooler to lower the intake charge temperature, which is heated mostly from the compression in the turbo or s/c*. Turbochargers use aftercoolers most often because they are able to compress air much more than most superchargers (most notably, positive displacement). A nice thing about them being able to compress more air is you essentially can make more torque with higher boost pressures as long as the compressor can supply the volume.

 

As for boost presure increasing... a turbocharger's boost pressure will build till you reach peak boost as limited by the wastegate where it then stays at that pressure till redline. Most setups see peak boost in the 3,000-4,000 rpm range depending on the turbo size. A centrifugal supercharger will build linear boost until redline where the boost peaks for the particular pulley being used. A roots supercharger will have nearly instant maximum boost and will likely drop off a little bit near redline or if its a decent one hold boost tille redline. Finally, a screws supercharger will have instant peak boost and will hold boost till redline. Reasons:

 

Turbocharger/Centrifugal Supercharger:

These two units are both centrifugal compressors. They are RPM dependent compressors meaning they will not create boost until a certain RPM. Turbochargers spin in the range of 100,000+ RPM for peak boost. Centrifugal superchargers spin in the 40,000 to 50,000 rpm range. The actual compressor wheel of both units look similar, but have totally different designs due to their RPM range. The reason the centrifugal superchargers spin at a much lower RPM is simply due to gearing. The pulleys and gears would have to be quite a bit larger to spin the s/c at the speeds a turbo is capable of.

 

Roots Supercharger:

The roots supercharger is in the positive displacement family and is actually not even a compressor like the other forms are. Lets start with positive displacement. An engine is a positive displacement air compressor. For every rotation, the unit will pull in and push out a measured amount of air just like an engine. That's why positive displacement superchargers have instant boost, because they are always moving the same amount of air. At idle the air must be recirclated using a recirculation valve that is built into the unit itself. This prevents boost while the throttle plate is closed.

 

As I mentioned above, the roots supercharger is not an air compressor. Think of the roots supercharger as a fan or a blower. The roots s/c blows so much air into the intake that it causes the air to compress in the intake itself. This is why roots superchargers are the most inefficient of the forced induction methods.

 

Screws Supercharger:

Like the roots supercharger, the screws is a positive dispacement supercharger... for ever rotation and measured amount of air is put through the unit. The major difference between the two is that a screws supercharger is a true air compressor. The air is compressed betwen the screws themselves making this unit very efficient. Boost is still instant and is able to hold till redline.

 

So lets say your peek allowed intake pressure is 10psi. You can set up your SC to create that 10psi of pressure at idle if you want (if your SC can withstand high RPMs) using different pully sizes. But with a TC you will always have to rely on the exhaust flow to spin the turbine, which can not create that kind of pressure off of low RPM exhaust flow.

 

You can setup your s/c to make 10 psi at idle... since we're talking about centrifugal superchargers lets start there. Lets say the maximum pressure the supercharger can make is 15 psi. If you set the supercharger up to where it made 10 psi off of idle, the minute you run the engine past a few thousand rpm you're going to blow the hell of your supercharger. Centrifugal superchargers can not and will not make peak boost until redline period. You can set the pulleys up to make more boost down low but you'll just blow the unit if you rev it past it's maximum pressure capability.

 

If we're talking roots or screws superchargers then yes, you're right... you can set the pulley up to have 10 psi off idle. Techincally they'd still nearly be making that 10 psi at idle if it weren't for the recirculation valve. Even though these units make boost earlier than the turbo... they are so much less efficient than the turbo that the turbo will still out power them.

 

Those that you are refering to do create heat (like all chargers), but no SC creates more heat than a TC.

 

A roots supercharger, like the one in the picture you posted, can easily put more heat into the air in the intake than a good turbo setup due to the way they force the air into the intake. A huge reason as to why they are so much more inefficient than a turbo.

 

Your exhaust heads will creat much more heat than anything else on the car, and that heat goes directly to the compressor of the TC....

 

That heat does NOT go directly to the compressor of a turbocharger. There is minimal heat exchange between the compressor and turbine. Yes, there is some... but not in the amounts you're trying to say. The center housing connects the two parts and is cooled and lubricated by oil... on a lot of newer units it is cooled by coolant as well.

 

But as you can see below you can not put an intercooler/or large inter cooler in one of these types of SC.

 

Yes, you can... it is an air to water aftercooler that is put between the intake and supercharger and even though they are rather small they make a massive difference in power output because of the heat those particular superchargers put out.

 

Now you would have to argue if the intake temp is cooler from a SC with no IC that creats less heat, or from a hot TC with an intercooler. Probably all just depends on your set up. BUT! the SC I posted a pic of before does not connect to the intake manifold in this way (nor does a vortec SC) and can have an intercooler installed in the same way a TC can. So your intake temps could/would/should be much lower than a TC's intake temps.

 

The original supercharger in question, the centrifugal supercharger, will have slightly less heat than a turbo and can be aftercooled, which is a big plus... however, you still have parasitic losses (the supercharger will take more power than the turbo), and you still won't have peak boost till redline (which is a massive hinderance).

 

Now as for the exhaust part of the TC. Your TC is not powered by heat, it is powered by the air being forced out of the motor.

 

That couldn't be more incorrect... Heat plays a HUGE role in spooling the turbo. The more heat you can keep in the exhaust and send to the turbo, the quicker the turbo will spool. Simple fact. That is why on those STS turbo setups that put the turbo in the rear of the car, they run a much smaller turbine for any given engine due to the immense heat drop between the manifolds and the end of the exhaust pipe.

 

If you have ever seen a turbine you can see that it has a little small passage ways for the air to pass through over the fins to spin it. Even though it spins easily the amount of volume/space for the air to pass through is lessened, for if it wasnt you could not spin the turbine. That = a loss in HP, more of a loss than the small load on the crank fram a small SC. So as for the "true HP"... both TC's & SC's take a little hp to make hp, and the SC uses less.

 

Yes, exhaust backpressure increases in the exhaust manifold when you use a turbo which is exactly where the power loss of a turbo comes from. Its a simple fact that using the crank to spin a supercharger takes more power than the increase in exhaust back pressure caused be a turbo. That is why turbochargers are so much more efficient.

 

Now as for the "Full Boost". if you read and understand what I wrote in the post before you will understand how a SC can create "full boost" before a TC can. And can sustain that boost all the way through the RPM range if set up in that away.

 

We're talking 3 different types of superchargers in this thread which I believe is confusing everyone. A centrifugal supercharger can not and will not ever create full boost anytime before redline unless they do a CVT pulley setup. A roots and screws supercharger will create full boost nearly instantly due to be positive displacement.

[Mr.INSANE]

When The hell did this become a turbocharger vs supercharger

 

Save you useless correcting and rambling and get the ******* point a supercharger on a z31

 

almost nobody has been attempting to help this guy