Twin turbocharging Vs. single turbocharging.

If you are too lazy to read long posts... Then you don't need to be driving a car let alone racing one.

OK, I was asked to post this because since I picked up that block, I have been serouisly thinking about going to twin turbocharging.

Now first I was like most the skepical about twin turbos because I used to feel that it was not worth the money. I also used to think that the only reason people used twin turbocharging is for better spool up because eveyone knows that two smaller turbos will spin up faster than one big one.

First thing I realized.

The whole deal about smaller twin turbos will spin up faster than a single is pretty much not true (assuming we are talking about having the turbochargers hooked up in parallel) is wrong. Think about it, on a v type engine with a single turbo, you route the exaust from one side of the engine,have it flow into a crossover pipe, that pipe connects to the other header. So all the cylinders (6 on my setup) are driving the turbine. Well on a twin turbo setup, you would have a smaller number of cylinders driving one turbo (for my setup, I would be using 3 cylinders per turbocharger. So, with a single turbocharger, you are getting massive ammounts of exhaust and heat through the turbine (Remember heat drives a turbocharger more than pressure.) Then on a twin setup, you have a smaller turbo, you have a smaller turbo being driven by half the exhaust heat and pressure.

Where I find the big advatage to twin turbocharging is not in airflow or manifold pressure or spool up time. It's in Exhaust pressure.

OK, lets get one thing out of the way, Turbochargers are NOT free horsepower. There is only one way to acheive free power out of ANY forced induction system, and that is intercooling.

Where the power loss is at is Exhaust back pressure. Now I know you all know that a turbocharger does put backpressure on the Exhaust system, but do you know how much pressure??

You would think that if you have 15 PSI of boost, then you would have 15 PSI of backpressure (get out what you put in right?)

General rule of thumb.... For every pound of boost you run, you will have 1.5-2 times that ammount of exhaust backpressure before the turbo. so you run 15 PSI, your going to have 30 PSI of backpressure. 20 PSI, 40 PSI in the exhaust. That is alot of damn pressure people. I know that sounds crazy and your probabally thinking "Oh BS, if that was the case, the exhaust would rush right back into the cylinder as soon as the piston stopped pushing it out of the cylinder." Well that would be true... BUT why do you think a cam that is designed for turbocharging has NO overlap in it?

Now going back to the way a single turbo setup Exhaust system is setup. the mainfold, over to the other manifold through a crossover pipe and in the turbine housing out the down pipe. That is a lot of piping with a lot of pressure. Then after it goes through the turbine, ALL the exhaust has to go though a single downpipe increasing the backpressure.

NOW on a twin setup, you have a shorter heads, two 3 inch downpipes, since it is a smaller turbocharger you can run a bigger A/R exhaust housing and decrease turbine housing backpressure (If you run dual ball bearing turbos, then you can run a HUGE A/R housing and have a real open turbine housing.) There are a few other things that reduce the pressure. Now I am not saying that you will completely get rid of the back pressure, you don't want to. Exhaust heat does most of the work but pressure does it's fair share as well.

Now lets go back to this turbo cam deal. A cam that has been ground for a turbo car is not designed to make power. For example, if you took a Buick Stage 2 272 cubic inch Bush grand national engine that made 600 HP naturally asperated, take the cam out of it, and put a cam in it designed to be on a turbocharged car, your power would drop so fast it would not be funny. If you can decrease the exhaust backpressure, you can start running a cam that is more ground for power and less ground for turbocharger ( I know that is not techincal but, I don't have the numbers in front of me)

Turbo cost also is a myth... Have you guys priced a PT-88 or larger large frame turbocharger???? Compared to a pair of TE-44's or TE-60s?? Now with a twin setup, you have more fabercation time and work in it but there are two things that ultimatly equal power. Money and Work.

Thourun, This is pretty much the short version of what I found

DISCLAIMER: This is research based on my Grand National. Different cars will be different in some certian aspects but, it all applies to evey type of turbocharged car.

Good write-up. The cost part is not clear to me. So it is cheaper for a twin-turbo than a single turbo (when talking about large turbos)?
Are you staying with a single turbo, or going twin?

That was a good read. HRM had a good article on a Twin turbo Viper, the guy switched from s/c to TT.... Also a good article to read if you're wondering what type of FI to use.

Well, now I can tell my mommy that I learned something very interesting at school today. Thanks Hypsi, I think I'll book mark this page for future reference :thumbsup:. L8...

Mr. Hypsi87, very good post, and your talking about something I was involved in at the University of Utah.
Some of the most heated arguements have been about turbo supercharging. The big myth you keep hearing is turbocharging is free HP cause it uses waisted heat and exhaust gas to make boost, whereas the centrifical, roots and screw type supercharger use the engine to drive them and consume large amounts of engine power to operate.
Lets establish two facts here. Fact one, the auto engine hates heat. Fact two, the auto engine hates exhaust backpressure.
Under controlled testing we installed different turbos on a engine with means of cooling the exhaust before it entered the turbo, in other words a cool exhaust. The difference between driving the turbo with hot exhaust and cooled exhaust was ZIP, nada.
The big difference was with cooler exhaust the turbos ran much cooler and the discharge air on the compressor was denser or more oxygen bearing air.
We went one step further and took a V8 and drove it with another engine making the engine a compressor. To that we installed a turbo to the exhaust side of this (engine) compressor and drove the turbo with nothing more than compressed air.
Everyone knows by installing a free flowing exhaust and headers you can gain 10-50HP on a stock engine. Now as you pointed out turbo's create back pressure. Your figures of 1.5-2 is alittle low, but close enough for the kinds girls I go with. This back pressure robs the engine of power. How much? depends on how much pressure you want to make. To compress air it takes power. I don't care what you use, to compress 10 lbs of air takes a given amount of power to make 10 lbs of compressed air.
Now a guy with this knowledge in Orem, Utah named Rick Squires (STS Turbo) and has developed a remote mounted turbo system, taking the turbo's to the next level. Being the turbo run cooler the discharge air is cooler (denser), cooler oil returning to the engine, much simpler mounting, and tests have proven more efficient than engine mounted turbos and less heat in the engine bay.
Old myths are nothing but old news, and those looking to get the most out of there cars don't need myths, but facts.

the advantage in parallel twin turbos is not that they spool faster, but can use both to create more boost vs a single. give me more time to think about why that is and i'll get back to you, okay?

the advantage in parallel twin turbos is not that they spool faster, but can use both to create more boost vs a single. give me more time to think about why that is and i'll get back to you, okay?

Smaller turbo's have less weight to move so easer to spin, the same reason we use lighter flywheels, lighter crank pulleys, lighter anything thats in motion. It takes less power to accellerate or put in motion. The size of the compressor and how fast it spins within it's envelop determines how much boost you'll create.

so how much hp loss is there with a turbo compared to a S/C?

so how much hp loss is there with a turbo compared to a S/C?

There is no loss as their all making power. As for the amount of power needed to compress air depends on how efficient the compressor is.
The most efficient compressor is the screw type supercharger and the topend turbo's real close.
Thats why Carrol Shelby chose to use the screw type supercharger on the new Shelby GT500 Mustang, as has Jag, Nissan and other car mfg's.

thats very interesting, i was always under the impression that turbocharging was better because it didnt eat up horsepower like a supercharger does

Mr. Hypsi87, very good post, and your talking about something I was involved in at the University of Utah.
Some of the most heated arguements have been about turbo supercharging. The big myth you keep hearing is turbocharging is free HP cause it uses waisted heat and exhaust gas to make boost, whereas the centrifical, roots and screw type supercharger use the engine to drive them and consume large amounts of engine power to operate.
Lets establish two facts here. Fact one, the auto engine hates heat. Fact two, the auto engine hates exhaust backpressure.
Under controlled testing we installed different turbos on a engine with means of cooling the exhaust before it entered the turbo, in other words a cool exhaust. The difference between driving the turbo with hot exhaust and cooled exhaust was ZIP, nada.
The big difference was with cooler exhaust the turbos ran much cooler and the discharge air on the compressor was denser or more oxygen bearing air.
We went one step further and took a V8 and drove it with another engine making the engine a compressor. To that we installed a turbo to the exhaust side of this (engine) compressor and drove the turbo with nothing more than compressed air.
Everyone knows by installing a free flowing exhaust and headers you can gain 10-50HP on a stock engine. Now as you pointed out turbo's create back pressure. Your figures of 1.5-2 is alittle low, but close enough for the kinds girls I go with. This back pressure robs the engine of power. How much? depends on how much pressure you want to make. To compress air it takes power. I don't care what you use, to compress 10 lbs of air takes a given amount of power to make 10 lbs of compressed air.
Now a guy with this knowledge in Orem, Utah named Rick Squires (STS Turbo) and has developed a remote mounted turbo system, taking the turbo's to the next level. Being the turbo run cooler the discharge air is cooler (denser), cooler oil returning to the engine, much simpler mounting, and tests have proven more efficient than engine mounted turbos and less heat in the engine bay.
Old myths are nothing but old news, and those looking to get the most out of there cars don't need myths, but facts.

On the Grand Nationals, we found that it was 1.5-2 lbs of pressure per lbs of boost.

NOW today in lab, I had a pressure gage hooked up to intake pressure and a pressure gauge hooked up to the manifold before the turbocharger (3126 CATERPILLAR diesel) and exhaust pressure was about 10 in/HG lower than boost at 90% load factor. The diesels have exhaust housings with such big AR's that they are not effected as much.


As far as you guys driving a turbocharger with cooled exhaust... I am confused. On my car and alot of other turbo cars that I have been around. The colder the exhaust the lazier the turbocharger was. Not that I am doubeting you, just not understanding.

Mr.Hipsi87, I love it when talking to people that are intellange enough to ask when they don't understand. I see someone with enough wisdom to look at things in a different way.

As to answer your question. From this point on everything is example only.
When the A/F (air/fuel) mixture fires it makes a great amount of pressure in the combustion chamber and drives the piston down. When the exhaust valve opens some of this unburnt mixture enters the exhaust manifold and is still burning and expanding creating more pressure. So what we have is the volume of the engine plus the unburnt fuel burning and expanding creating pressure on the turbine wheel.
Because of ignition timing and cam duration on most engines what we have is a engine with about 90% efficiency or a engine putting unburnt fuel into the exhaust.
Not really a big problem cause by supercharging a engine to say 14.7psi we can make a 300ci engine think it's a 600ci engine, but we still have the unburnt fuel problem.
We can't advance the timing much or we run into detonation problems, but we've eliminated the unburnt fuel problem. To eliminate the detonation problem if we install a water/alky injection system we'll not only cool the combustion chamber temps. but we'll also raise the octane level of the fuel so we can run more timing and thus eliminate the unburnt fuel problem and make more power as were putting more power into the engine than the exhaust. Also by making more power were making more pressure in the exhaust without the hi temp. thus driving the turbine with more power.
I suggest you read all you can about water/alky injection you can and kill all the myths about it at the same time.
And if you are really serious about this I'll tell you about making 1,000HP per liter engine displacement.
Snow has some pretty good info on water/alky injection.

http://www.snowperformance.net/

Zgringo i have to say that as Hpsi I'm very surprised by those results.

by cooling the exaust down the presure diference between the two sides of the tubine will decrease, or if you prefer to see it in terms of kinetic energy by cooling down the gass you are robing it of its potential energy which would normally be transfered to the turbine blades.


Also about STS turbo, i have to admit I was a bit cinical about its remote turbo systems. However it seems they do seem to work quite well. However I'm still firmly convinced that the best placement for the turbo is close to the exaust ports where the exaust gas has the highest kinetic energy.

Also my gym trainer who is also a major car freak like me happens to know the STS guy, and from my last talk to him it sounded like even STS agrees with me about the proper placement of a turbo, and their remote systems are more of a "next best thing" for convenience. Of course this is more of a hear say so i might have the wrong impression.

However I can talk to my trainer to ask him directly this question or me and Polygon can drive up there and talk to them directly.

Lets try this heat cold thing a different way. Take a turbo and on the engine exhaust side apply 1000F and on the discharge side apply dryice -180F. Well it spin?

Now take a Ingersoll Rand compressor and apply 150psi to the engine exhaust side (inlet) of the turbine. Well it spin?

The pressure differencial between the intake side and outlet side will determine the amount power the turbine potential well be.

Have your gym teacher talk to Rick Squires, owner at STS turbo and I don't think he'll say it's "the next best thing". If you'd like I could get Rick on here or maybe email me his thought's on this so I could post them here.

If you read my post I say the unburnt gas coming out of the engine is still expanding creating more pressure.

Read what a few experts have to say:

<DIV><DIV>Kenny Duttweiler - Duttweiler Performance, Inc.
(Longtime "Turbo God" Kenny Duttweiler has a well-established reputation as the finest turbo tuner in all of drag racing.)</DIV><DIV>"Squires Turbo Systems' remote-mounted turbos have solved all of the problems associated with traditional engine-mounted turbo systems. The intense underhood heat a turbo generates has been eliminated and you no longer need to punch a hole in your oil pan or cut up the front of the vehicle for an intercooler. Emissions should be really good too with mounting the turbocharger after the catalytic converter."</DIV><DIV>Joe Pettit - Editor of Sport Truck Magazine
(Joe recently installed our system on a Chevy 4.8L Silverado - details are in the October 2004 issue of Sport Truck (http://java script:ezPOpen('news');)magazine.)</DIV><DIV>"When we first saw this turbo system at last year's SEMA Show, we were very skeptical about throttle response. We thought that with the turbo so far away from the combustion chamber, the system would be lazy with a lot of turbo lag. But after driving the system on other trucks as well as on this install, we find the lag not excessive in the least; it is very near what you find on factory turbo systems."
</DIV><DIV>"So if you're looking for a power adder for your sport truck, we recommend you take a look at the STS remote mount turbocharger system." </DIV><DIV>Evan Griffey - Editor of Turbo and High Tech Peformance Magazine
(Evan's 3 page article on STS appears in the October 2004 issue of the magazine (http://java script:ezPOpen('news');))</DIV><DIV>"The velocity of exhaust gas and the fact that the STS design features a good deal of straight pipe, coupled with what exhaust gas does when it enters a turbo, should help negate any "lag" in the system."

</DIV><DIV>"We commend Squires Turbo Systems for the innovation and integrity of the concept it put forth, and we also appreciate the enormous potential it represents."</DIV><DIV>Patrick McCarthy, instructor at ESPN's

Here's somemore to read about STS

http://www.ststurbo.com/testimonials

Lets try this heat cold thing a different way. Take a turbo and on the engine exhaust side apply 1000F and on the discharge side apply dryice -180F. Well it spin?

Now take a Ingersoll Rand compressor and apply 150psi to the engine exhaust side (inlet) of the turbine. Well it spin?

The pressure differencial between the intake side and outlet side will determine the amount power the turbine potential well be.




notice in my post that i did specifically mentioned that the turbine is spun by the pressure difference.


So there is no contradiction between us. My point was however that by cooling the exaust before it hits the turbine you lower the initial presure.

About my STS comment as i said previously It was only hear say so I might have gotten the wrong impresion. That is why i might just pay them a visit this weekend to talk to them directly to find out more info. My trainer speaks quite well of them so it sounds like they have a very good company. However i would still like a few more details about their remote turbo systems.


About the original question Hpsi my opinion is to go twin turbo since from my knowledge its more efficient to have the turbo close to the exaust ports rather than have it at the end of a maze of tubes.

So there is no contradiction between us. My point was however that by cooling the exaust before it hits the turbine you lower the initial presure.

So you understand where I'm coming from all I hear is turbo's operate on heat. The heat or expanding exhaust gas is making pressure, but you still have pressure created by the engine displacment. Without the expanding exhaust gas you'd have to resize the turbine to make up for the drop in volume and pressure.
STS has done some engineering to figure this drop and has sized the turbines to make up for this.
I'm glad to see were on the same wave length.

So let's see if I'm following this correctly.

Neutrino was saying that there would be a significant drop in exhaust pressure as the temperature is lowered. This makes sense because when considering the Ideal Gas Laws (back to high school chemistry, bear with me), PV=nRT, where temperature and pressure are directly proportional to eachother. Therefore, you believe that a turbocharger should be located near the exhaust manifold.

On the other hand, ZGringo, you acknowledge this fact; however, you think that the drop in temperature and thus pressure will be made up by the unburnt gases exiting the exhaust port burning and creating more pressure. Also, the intake charge will be much cooler, and thus, denser air into the engine.

Am I correct or did I miss something?

DISCLAIMER: This is research based on my Grand National. Different cars will be different in some certian aspects but, it all applies to evey type of turbocharged car.

First off, that was a very good read. I must say that your article applies to every turbo-charged car. I like the fact that you pointed out that turbo-charging does not offer free power. Backpressure on a turbo-charged car is much like the parasitic loss on a super-charged car except a turbo also uses lost power to make power through the exhaust. I think the average car loses 70HP out the exhaust. Some have more than others and there are many ways to reduce backpressure. I also like the fact that you pointed out the difference between a turbo cam and an N/A cam. A lot of people don't realize that the way you make power in an N/A will hurt a turbo car and vice versa.

There are a lot of ways you can reduce backpressure. I know that my car exhibits a lot of backpressure because of a very restrictive exhaust. Things like pipe diameter, types of bends, and material all can affect backpressure. Ideally you want to run bigger pipe, at least three inches or more depending on your application, and you want mandrel bends. Crushed bends are just a restriction. Also, you can have your manifolds or headers and downpipes coated in a thermal coating that will help the exhaust exit faster. This will reduce backpressure and spool time.

As for the twin vs. single debate, I must say that depends on the setup. I prefer one turbo; it is less to worry about and less to go wrong. Also, if you have one turbo per bank and one turbo fails that might damage that bank of cylinders. While that isn’t likely, it is just a thought. Have you ever considered using a smaller turbo in tandem with a larger turbo? The smaller turbo will spool up fast and once it runs out of steam the larger turbo will pick up where the smaller one died out. That is also just a thought.

As for what turbo to get, I would go with nothing less than a GT series turbo even though they start at around $1,600 just for the turbo, they are very much worth it. My pick would be a couple of GT28RS, I believe, that is the right model for the famed "Disco Potato" turbo.

I am putting one of those on the GTC. It has been called one of the most efficient turbos ever.

Holy cows BATMAN this has been one of the best discussions I've seen.

So let's see if I'm following this correctly.

Neutrino was saying that there would be a significant drop in exhaust pressure as the temperature is lowered. This makes sense because when considering the Ideal Gas Laws (back to high school chemistry, bear with me), PV=nRT, where temperature and pressure are directly proportional to eachother. Therefore, you believe that a turbocharger should be located near the exhaust manifold.

The above statement is very correct, but the drop in exhaust pressure can be compusated for by sizing the turbine to the pressure available. Also the complete turbo housing will be much cooler, thus you discharge air from the compressor will be much cooler.


On the other hand, ZGringo, you acknowledge this fact; however, you think that the drop in temperature and thus pressure will be made up by the unburnt gases exiting the exhaust port burning and creating more pressure. Also, the intake charge will be much cooler, and thus, denser air into the engine.

Now we come to the STS application. By placing the turbo in the rear of the car we have a lower exhaust temp. but by sizing the turbine have recovered most of that loss.
Now comes the biggie. Do to the fact we have a cooler turbo housing our compressor will have a cooler (denser) outlet air temp., plus with a longer tube exposed to the free air to supply pressured air to the engine, more drop in the air temp. being supplied to the engine.
Another plus is the returning oil is exposed to the free air also and is cooler returning to the engine.

Now if you install a water/alky injection system in eather setup's you'll only enhance the performance of the engine 10 fold.

Am I correct or did I miss something?

You've hit the nail on the head!!!!!!

Mr. Polygon, your statement on exhause is so right and factual. If all of us would take a look at some of the exotic motorcycle exhaust or the formula1 cars we'd see technology beyond our wildest dreams.
We as drag racers or street racers havent even scratched the surface yet in that area.
Then we have ram intake tuning.
We all have lessons to learn.

So what is the best??? Well if pissing on a spark plug would help me win, guess what?

Thourun, This is pretty much the short version of what I found
So sory I wasn't there when you messaged me AIM, I was out with a friend and didn't leave an away message. This discussion is great and answred a lot of the questions I would have had if I had been here for it :rolleyes:, just wish I had somthing to add.

There should be another discussion on how meth/water/propane injection should be used now. I hope to upgrade turbos and suporting hardware within a year or two and want to increase the power I can get out of my car using 93 octaine gas and stock heads. The only person I've actually spoken to about this had propaine and some marginaly larger turbos (stock housings, different wheels), he said that he used propane because he would have to refill on alky/water much more.... In any case perhapse this should become its own thread even though it was mentioned a few times here, I just hate to make threads with my stupid questions, makes me feel selfish and lazy like I'm having other people do research for me.

ok I will start a new thread on it.

Lets establish two facts here. Fact one, the auto engine hates heat. Fact two, the auto engine hates exhaust backpressure.
Under controlled testing we installed different turbos on a engine with means of cooling the exhaust before it entered the turbo, in other words a cool exhaust. The difference between driving the turbo with hot exhaust and cooled exhaust was ZIP, nada.
The big difference was with cooler exhaust the turbos ran much cooler and the discharge air on the compressor was denser or more oxygen bearing air.
We went one step further and took a V8 and drove it with another engine making the engine a compressor. To that we installed a turbo to the exhaust side of this (engine) compressor and drove the turbo with nothing more than compressed air.

Those are very interesting results. However, I am not sure if I understand them correctly.

The results indicate that a significant amount of heat is passed from the turbine side of the turbocharger to the compressor side, correct? So an excessive amount of heat is transferred from the exhaust gases into the incoming air? Do you have any data on the heat transfer characteristics that you can share?

Also, assuming I am following this correctly wouldn’t it better [theoretically] to increase the distance between the turbine and the compressor. Such as using a longer impeller shaft and completely separate turbine and compressor housings in effort to reduce heat transfer.

The point is that for a given pressure ratio more work can be extracted by the turbine if the exhaust gases are higher. In this way the backpressure could be minimized by maximizing the exhaust gas temperature. Thermodynamically speaking isn’t this a desirable approach?

Mr. Polygon, your statement on exhause is so right and factual. If all of us would take a look at some of the exotic motorcycle exhaust or the formula1 cars we'd see technology beyond our wildest dreams.
We as drag racers or street racers havent even scratched the surface yet in that area.
Then we have ram intake tuning.
We all have lessons to learn.

So what is the best??? Well if pissing on a spark plug would help me win, guess what?

Exactly.

People with turbo cars need to understand that the quickest way to get some more power from a stock turbo setup is to replace the exhaust. Most of them start with the intake and what not. Removing the cat alone give you much more responsive turbo.

I have also enjoyed reading your posts man! :bigthumb:

Those are very interesting results. However, I am not sure if I understand them correctly.

The results indicate that a significant amount of heat is passed from the turbine side of the turbocharger to the compressor side, correct? So an excessive amount of heat is transferred from the exhaust gases into the incoming air? Do you have any data on the heat transfer characteristics that you can share?

Also, assuming I am following this correctly wouldn’t it better [theoretically] to increase the distance between the turbine and the compressor. Such as using a longer impeller shaft and completely separate turbine and compressor housings in effort to reduce heat transfer.

The point is that for a given pressure ratio more work can be extracted by the turbine if the exhaust gases are higher. In this way the backpressure could be minimized by maximizing the exhaust gas temperature. Thermodynamically speaking isn’t this a desirable approach?

There is a flaw in your theory since most of the backpressure is a simple result of the impeller being in the way of the exhaust flow. Also lengthening the shaft wouldn't help. The heat will transfer through the shaft no matter how long you make it. It also makes more weight and rotational mass for the exhaust to spin which might cause more backpressure.

There is a flaw in your theory since most of the backpressure is a simple result of the impeller being in the way of the exhaust flow.

I realize there will always be back pressure and that a certain amount of pressure is necessary for turbine work. Also, realizing that temperature and pressure are related I am wondering about operating temperature for a given pressure. Is not thermodynamically desirable to have a higher temperature for given exhaust pressure?


Also lengthening the shaft wouldn't help. The heat will transfer through the shaft no matter how long you make it.

I understand that heat will still be transfer through the shaft, but what proportion is transfer through the shaft with respect to the housing. I would think significantly less is transfer through the shaft alone, and I was hoping Zgringo could shed more light on that.


It also makes more weight and rotational mass for the exhaust to spin which might cause more backpressure.

You are definitely right about that.

I suppose there are pros and cons to each side. I can see your points though. It would be nice to try it and see which is more efficient.

I suppose there are pros and cons to each side. I can see your points though. It would be nice to try it and see which is more efficient.

As with everything. I'd like to have Strasburg's engine dyno and a base engine and test the remote turbo vs. engine mounted turbo's vs. screw type superchargers. Then do a single turbo vs. dual turbo's test. I truly (but not sure) think all compressors well do there job within there envelop according to there efficiency, being all sap engine HP by backpressure or directly from the crank. It takes a giving amount of HP to compress air.
I'm somewhat bias to the screw type supercharger as they operate in the 90% efficient range where as the engine mounted turbo is in the 80-85% range. The rear mount turbo??????

Zgringo

Could you share any of your information on heat transfer from the "hotside" of the turbocharger to the "coldside"?

Zgringo

Could you share any of your information on heat transfer from the "hotside" of the turbocharger to the "coldside"?

I'd be more than happy to if you'll tell me just what your looking for.
Also I just got off the phone with the owner and one of the top boys at STS (Squires Turbo Systems) and they have agreed to come on here and answer any questions about there system and turbo'n you might have.
All someone needs to do is start a thread and get the ball rolling. I just don't want this to turn into a sales meeting but a scorce of information.

I'd be more than happy to if you'll tell me just what your looking for.
Also I just got off the phone with the owner and one of the top boys at STS (Squires Turbo Systems) and they have agreed to come on here and answer any questions about there system and turbo'n you might have.
All someone needs to do is start a thread and get the ball rolling. I just don't want this to turn into a sales meeting but a scorce of information.

I started a new thread, so if you could let STS know that would be great:

http://www.automotiveforums.com/vbulletin/showthread.php?t=399086

I currently have a ITS DBB76R on the car, but with the rear mount setup i'm not able to supply enough exhaust pressure to effectively boost over 6 psi. The 67 p-trim I had on it worked much better and made more power.

The 76 .81 divided housing is for sale for $1600 if anyone is interested, has barely been used. New they cost about $2600 new.

Link to sale
http://www.ls1tech.com/forums/showthread.php?t=310428

Go look at all the STS dynos. Compare them to conventional mount turbo dynos. They're fairly similar in peak power numbers, but the front mount kits bring the power in way sooner. I've seen two cars with fairly similar setups dyno in terms of peak power, and the front mount kit bested the rear mount by over 100 RWTQ because of how much quicker the boost comes on.

Go look at all the STS dynos. Compare them to conventional mount turbo dynos. They're fairly similar in peak power numbers, but the front mount kits bring the power in way sooner. I've seen two cars with fairly similar setups dyno in terms of peak power, and the front mount kit bested the rear mount by over 100 RWTQ because of how much quicker the boost comes on.

If the turbine was sized properly, I don't think this would be true. Could you please post some dyno results.
Also I don't understand how the front mounted turbo could have over 100RWTQ when the peak power numbers are similar.
There's a thread where you can ask STS (the inventor) any question directly.