I understand most don't need this type of configuration, but since 3800s come blown I figure may as well take advantage of the M90.

If one were to have the turbo boosting the blower then the blower to the engine then the engine to the turbo. A traditional supercharger/turbo compound setup.

What size turbo would be best? I have read that a T66 is the smallest for a turbo only 3800, but would a T88 be big enough to take advantage of the compound setup?

I would expect making a map of the blowers output, and using the turbo to fill the gaps would be a good approach.

the m90 is not that great of a supercharger. it dose not compress the air it just mover 90 cfm per revolution. it would be way easier and cheaper to run a good sized turbo with a shot of juice to help spool it. zzp did run a twin charged setup but it was no faster the intense's single turbo drag car. what are your goles and budget with this car?

quote Originally posted by chrisgtp: the m90 is not that great of a supercharger. it dose not compress the air it just mover 90 cfm per revolution. it would be way easier and cheaper to run a good sized turbo with a shot of juice to help spool it. zzp did run a twin charged setup but it was no faster the intense's single turbo drag car. what are your goles and budget with this car?

it does compress, but that 90 CFM is variable. it does NOT move the same amount at different RPMs. that is one of the problems with superchargers.

They don't move 90 CFM. CFM is cubic feet per minute. They move 90 CUBIC INCHES per REVOLUTION . The output of the supercharger is dependent upon how fast it is turned (engine speed or pulley ratio) and how much air it can draw past the pressure drop of the throttle body. With the throttle closed, the output is much much LESS than 90 ci per revolution.

They do "compress" the air. That's why the outlet temps of superchargers are elevated. In fact, as a general rule, when operating at a flow rate near peak efficiency, turbochargers almost always compress air more efficiently than superchargers. Each type of compressor (centrifugal versus positive displacement) has its own compromises and drawbacks.

Not sure what you mean by saying that the output is variable.....?
Sure the actual boost level in PSI doesn't stay the same throughout the whole range of engine operating RPM at WOT, but that has to do with a number of factors such as solenoids that bleed boost in most of the modern supercharged cars, as well as engine volumetric efficiencies which vary with engine speed. The supercharger puts out a fixed amount of air per revolution, and its the engine's changing capacity that causes the "boost" gauge to vary

[This message has been edited by KurtAKX (edited 09-19-2007).]

Roots may not be the best superchargers, but I see no reason to "waste" an M90. Running compound is cool cause you can run low psi in the turbo and super, but have an end result of like 18psi.

I want a car that is good at the local 1/8th as well as good in street racing. Like highway runs or light to light. The compound idea sounds pretty good for what I want. I am sure nitrous will spool the turbo faster, but only because of the increased exhaust gases. Now an M90 can do the same for cheaper. I would rather use my nitrous as a "small" increase in power and not rely on it for my power. Compounding creates a vicious powerband.

[This message has been edited by goatnipples2002 (edited 09-19-2007).]

quote Originally posted by KurtAKX: .... Not sure what you mean by saying that the output is variable.....? Sure the actual boost level in PSI doesn't stay the same throughout the whole range of engine operating RPM at WOT, but that has to do with a number of factors such as solenoids that bleed boost in most of the modern supercharged cars, as well as engine volumetric efficiencies which vary with engine speed. The supercharger puts out a fixed amount of air per revolution, and its the engine's changing capacity that causes the "boost" gauge to vary

the compressor system is not consistant thru the RPM range in the amount of air it will move/compress. what it moves at 1000 rpm and what it moves at 4000 rpm is NOT a 4x difference. obviously, in the design, they will try and make the sweet spot as wide as possible, and in the expected usage range - but, it is NOT a flat CFM X RPM formula.

quote Originally posted by Pyrthian: the compressor system is not consistant thru the RPM range in the amount of air it will move/compress. what it moves at 1000 rpm and what it moves at 4000 rpm is NOT a 4x difference. obviously, in the design, they will try and make the sweet spot as wide as possible, and in the expected usage range - but, it is NOT a flat CFM X RPM formula.

True, but you can approximate it that way a lot better for a roots (or any other positive displacement pump) than you can for a centrifugal style like a turbo or Paxton/Novi.

I wouldn't even consider this on an N/A motor, but if it comes with an M90 for the lows, why not add a huge snail for the highs.


In a compound setup detonation is easier to deal with because with a SC or TC the intake psi is well above the exhaust back pressure, and with sufficient valve overlap, the heat can escape due to much more efficient positive scavenging.

[This message has been edited by goatnipples2002 (edited 09-20-2007).]

Just a follow up on this. It is a very sweet idea, but I have a complete nitrous system and that will be my "twin charge" for my future L67 swap. I can use nitrous for the top end and for cooling. Turbos are sweet, matched with a blower they can be even sweeter, but a 75-100 shot (maybe more) on a boosted motor will give me the power levels that I want without the troubles of trying to cool the intake charge.

Any thoughts on this?

[This message has been edited by goatnipples2002 (edited 12-12-2007).]

here's an idea...

Since a turbo needs air at all times, why not use a supercharger to spin the turbine?
Throw a pressure valve on open air that way, at low rpms, the SC can pull in fresh air, then as more exhaust is pushed, the fresh air source closes and the SC is fed from there, pushing the turbine to power the turbo.

This should allow the turbo to make boost right at idle. The SC would have to be sized to the turbo so that it could make boost right to redline as well.

Thoughts?

quote Originally posted by lou_dias: here's an idea... Since a turbo needs air at all times, why not use a supercharger to spin the turbine? Throw a pressure valve on open air that way, at low rpms, the SC can pull in fresh air, then as more exhaust is pushed, the fresh air source closes and the SC is fed from there, pushing the turbine to power the turbo. This should allow the turbo to make boost right at idle. The SC would have to be sized to the turbo so that it could make boost right to redline as well. Thoughts?

The whole idea behind a turbo is to reuse some of the wasted energy in the exhaust. By driveing the turbo from a supercharger you're directly taking power off of the crankshaft and not putting as much volume throught it. You'll just be compounding innefficiencies.

There is some wrong information flying all over here.

The biggest thing everyone is overlooking is the fact that the blower moves fixed amounts of air, but the "90ci per rev" or whatever, is measured with a 0psi input pressure. The blower is efficient up to a pressure ratio of 12psi, aka 1.8:1. So simply, if you put 10PSI in, you can easily get that PSI compressed further by the blower, adding it on just like you would in a "supra style" bi turbo setup.

The overall Idea of twin charging is very decent idea, and very easy to implement, due to the fact that compressors work on pressure difference, not intake pressure. In theory, the blower would not be working any harder, if you put 50PSI into it, and it added on an extra 10-12 psi.

The biggest misconception about running a blower, is the fact that your "losing power" through turning it. While this obviously is true, its fairly moot, considering 99% of the setups I see, are losing the 20 or so HP that the blower uses to run and wasting it somewhere else. Also, if you got a M90/turbo hybrid putting down 500 to the wheels, taking the blower off and exactly compensating with a turbo, will only add 20hp.

The only problem I see with a bi charged setup, is the fact you need a fairly retarded turbo, big exhaust housing, and a high flow compressor to really take advantage of the supercharger.

This setup would be very good with a heads/cam motor, with plenty of cooling after the turbo, and after the blower, so that makes for 2 intercoolers, $1000+ in heads, cam, and plenty of custom fab, along with a fully built AUTOMATIC. So, basically I am saying its only usful to add the turbo if you have a motor that is already maxing out a blower setup, and the same goes for the nitrous. If you are not putting down 300+whp just a M90, you have no business tossing on nitrous or a turbo.

quote In a compound setup detonation is easier to deal with because with a SC or TC the intake psi is well above the exhaust back pressure, and with sufficient valve overlap, the heat can escape due to much more efficient positive scavenging.

Wrong, turbos create excessive exhaust backup compared to a supercharged setup with headers. Intercooling and gas are the only tools you have when fighting knock.

quote Originally posted by Zac88GT: The whole idea behind a turbo is to reuse some of the wasted energy in the exhaust. By driveing the turbo from a supercharger you're directly taking power off of the crankshaft and not putting as much volume throught it. You'll just be compounding innefficiencies.

Right but the turbo usually needs time to make boost. Having a supercharger do the scavenging of the exhaust would eliminate that and as darkhorizon pointed out, having more exhaust coming into the supercharger, it will still add 10psi to it feeding the turbo with even more pressure.

This way you can put on a big turbo and have it make boost early, not to mention at the top.

quote Originally posted by Zac88GT: The whole idea behind a turbo is to reuse some of the wasted energy in the exhaust. By driveing the turbo from a supercharger you're directly taking power off of the crankshaft and not putting as much volume throught it. You'll just be compounding innefficiencies.

You'd have a higher detonation threshold than with just a turbo. Once you are in the boost the turbo will actually give your efficiency back to the blower by helping push the rotors, so not much, if any parasitic loss. Superchargers by themselves all suffer from a rapidly falling volumetric efficiency at high engine rpm, that is inescapable. Turbos, (within a fairly limited flow range) can offer increasing flow and pressure, with rising rpm. Wonderful for top end airflow, but excessive turbine back pressure, high boost threshold, and lag, can be less than wonderful. But combine the two in the correct proportions and it is pure orgasmic. Getting the proportions right is just a case of experimenting with the blower pulley and the exhaust turbine a/r. This is not difficult, but the results are always extremely rewarding. Heat would be a concern but through an intercooler, meth/water/alky injection and/or valve overlap adjustments the heat can be a nonfactor.

The VE drop of the M90 is exactly one of the reasons nitrous up top would be very beneficial.

[This message has been edited by goatnipples2002 (edited 12-12-2007).]

You are really thinking about this wrong. You will never "push" the rotors, they will always have the same pressure ratio, unless you change the amount of air you are getting out from under it.

Nitrous only makes up for boost you cant add, so in a super/turbo setup, nitrous would NEVER have a place. The only people that nitrous blower cars, are running flawlessly with a maxed out M90. Very very few people can spray turbo cars, and its only in limited places to help spool the turbos.

Overall, you should just setup something, and practice running and tuning that for awhile, because anything you do like this is going to be VERY hard tuning wise (again I do not mean pcm tuning exclusively). You really need to learn what these setups need, and supply it to them, and its not really something that can not be taught, its really just learned experience.

Lets just say there is a reason I still just have a stock setup and Its more than money that keeps me from going to a more aggressive setup.

So you are telling me nitrous will not help in the higher rpms with an L67? Plenty of people run juice on the L67 with great results. What is maxed out as far as pulley and cam go. How can nitrous not help. It helps cool down the charge AND it adds air, but above all it increases efficiency as does this.

I would like to add a turbo to an L67, but I will have just enough for the swap and valve train upgrades.

I mean hell people use nitrous to spool turbos that don't do anything before 3800-4k and they use nitrous to help blowers that lose efficiency after 3800-4k, why not us?

I think i just caught on do you mean because the roots doesn't compress in the case but in the Manifold? (About the "push" theory?)

What I plan just running and tuning is an L67 with juice.

[This message has been edited by goatnipples2002 (edited 12-12-2007).]

The "cooling effect" is not even enough to keep the added knocking introduced by nitrous. You will have to run less timing, and more fuel in any nitrous setup, and hope that you are coming out on top by adding the extra oxygen.

Nitrous has the least amount of cooling effect of anything known to inject into a motor, that means fuel, water, alcohol, all have better cooling properties than nitrous. Remember the density of nitrous is nearly insignificant when compared to water or alcohol. If for some reason you are running perfectly flawless with a m90, and you have a 2.8 pulley on, adding 125HP of nitrous, upping to a 3.0 pulley, and taking down some timing is possible, but only if you have intimate knowledge of what condition your motor is in while running this. I see too many people that do all these things, toss all this money at their motors, then do nothing to keep tabs on it, or tune it to work the best way you can out of what you have, and think they need to toss more stuff on it to make it faster. From my experience, setting up a custom motor is more than just reading crap and attempting to replicate it, its more of an art project, as no 2 setups can be perfectly identical. You can make post after post on here, and get very intelligent and accurate descriptions of what people have done and how well it works, but you will never understand the complete package they actually have and how they accomplished it.

Your effort you put into your project, and the amount of time you spend with it, is directly related with how well it will perform.

For your information, nobody runs "juice" on their L67's with great results. Some have had results similar to higher boost levels, but in no situations has nitrous surpassed properly sized boost adders.

I understand scanning/tuning is the key to any good setup. I never said it wasn't I assumed anybody speaking on this subject would have that common knowledge.

I read to learn, I converse to understand what I have learned and share experiences, then try it to gain experience.

You speak as if nitrous is the devil. Boost is not the only way of making power. I guess spraying a shot and gaining more than the shot sprayed isn't great to you, but that sure sounds good to me. People spray boosted motors all the time. SRT4s, Cobras, Skylines, Supras, Hondas, guess what even L67s.

Nitrous may not be as dense, but when it leaves that bottle it is way colder than some damn water. I should know I got a mean ass nitrous burn once. It didn't feel hot to me. If you are running perfect with an m90 then add nitrous why would you not still be running flawless if your fuel and tune are good?

I know you know some stuff about this engine but damn do you read all the nitrous threads on CGP?

[This message has been edited by goatnipples2002 (edited 12-12-2007).]

cold does not mean it has great thermal absorbing properties..... I am just saying that there is no free power from nitrous, If you want to replace boost with nitrous, go ahead, its alot cheaper than adding a turbo, just dont expect amazing results with it.

You cant "gain experience" from talking about things.

quote Originally posted by darkhorizon: You cant "gain experience" from talking about things.

For real? Thanks for the clarification.

That is why I said "TRY IT to gain experience".

[This message has been edited by goatnipples2002 (edited 12-12-2007).]

quote Originally posted by darkhorizon: ..... You cant "gain experience" from talking about things.

no, but you can gain wisdom from those who have tried. never be scared to discuss. you will ALWAYS come out better.

Yea, I said that sorta blunt. I did mean what you guys corrected that too though.

Why not sequential turbo and run like a t25 or smaller then a T04 and then you have the best of both worlds and save your self alot of SC trouble. As for the M90 the ford thunderbird version may have a higher parasitic loss but will produce 14psi and with porting and a pulley they have seen 20psi so they are effective and do the job. As for a eaton M90 as a good supercharger considering if you want a more efficient blower you will need a whipple and yea you spend the cash on one of those if you want but for the $ the M90 is one of the best you can have.

Would nitrous/turbo or nitrous/super be considered twin charging?

Nitrous may not have the same cooling effect as meth/alky/water (I don't believe that, I will check), but it sure as hell has major potential for power.

Dark are you against nitrous?

To all that have posted in here thank you.

I an never against nitrous, I am quite a nitrous fan. I just dont think you will need it until you get a setup running and breathing for awhile. I dont see a need to put nitrous on a motor that cant handle the blower thats on it already. There is a reason GM warrentee's a pulley drop from 3.4 to 3.0 on the LSJ ecotec's, they have the motor setup to support it, 3800's dont from the factory.

The reason I dont like nitrous on 3800's is dispersion. The lower intake manifold really favors getting any type of injection material distributed to pistons 3/4 more than any others. You NEED to do some direct injection if you are going to do it reliably.

quote Originally posted by darkhorizon: The overall Idea of twin charging is very decent idea, and very easy to implement, due to the fact that compressors work on pressure difference, not intake pressure. In theory, the blower would not be working any harder, if you put 50PSI into it, and it added on an extra 10-12 psi.

Not quite. Constant displacement pumps (like an M90) make pressure by flow ratio. Non-constant displacement pumps (like a turbo compressor) make flow by pressure ratio.

quote Originally posted by goatnipples2002: You'd have a higher detonation threshold than with just a turbo. Getting the proportions right is just a case of experimenting with the blower pulley and the exhaust turbine a/r. This is not difficult, but the results are always extremely rewarding.

If the results are "always" rewarding, you should have now trouble showing FIVE twin charged setups for which selecting the right combo of pulley and turbine housing A/R was rewarding.

Define "detonation threshold".

[This message has been edited by Will (edited 12-12-2007).]

quote Originally posted by Will: Not quite. Constant displacement pumps (like an M90) make pressure by flow ratio. Non-constant displacement pumps (like a turbo compressor) make flow by pressure ratio.

Yea, its a bit off due to the fact that the blower has to keep the pressure from leaking back, but in a perfect world it would be sorta true. I guess I was just trying to prove a point with it.

quote Originally posted by darkhorizon: in a perfect world it would be sorta true.

No, it wouldn't.
A blower makes boost according to flow ratio, not pressure ratio. The boost pressure is dependent on the flow ratio.
A compressor makes boost according to a more complicated set of criteria, but pressure ratio is its independent variable.

Anyway, twin charging is a bad idea because the inefficiencies of the turbo and the blower are multiplicative. The system would have comparatively huge intercooling needs.

[This message has been edited by Will (edited 12-12-2007).]

check out this tread, turbo + s/c'd 3.8 formula

Will not unless you run some ridiculous pressure ratio...
It is ok to have an educated opinion, but WCF did this project couple of years ago and it was absurd power to say the least. It is all about compromises and what you are willing to live with or give up...
Go to UK or hardcore FI forums and this things have been done several times over.
Also rather than regurgitate info you can try eng-tips forum...luck good!

Eng-tips forums is where I read alot about this.

http://www.eng-tips.com/vie...m?qid=177189&page=14
http://www.eng-tips.com/vie...fm?qid=137731&page=7
http://www.eng-tips.com/vie...fm?qid=198474&page=1
http://www.eng-tips.com/vie...fm?qid=174690&page=1
http://www.eng-tips.com/vie...m?qid=173617&page=10

quote Originally posted by nocuttt: Will not unless you run some ridiculous pressure ratio... It is ok to have an educated opinion, but WCF did this project couple of years ago and it was absurd power to say the least. It is all about compromises and what you are willing to live with or give up... Go to UK or hardcore FI forums and this things have been done several times over. Also rather than regurgitate info you can try eng-tips forum...luck good!

What am I regurgitating? I use my words, not someone else's.

If you're not running a "ridiculous" pressure ratio, what's the point of the extra weight and complexity?
If WCF's project made such "absurd" power, how absurd was it? The car must have been on a dyno for tuning...
If I knew anything about eng-tips, I might be there...

quote Originally posted by goatnipples2002: Eng-tips forums is where I read alot about this. http://www.eng-tips.com/vie...m?qid=177189&page=14 http://www.eng-tips.com/vie...fm?qid=137731&page=7 http://www.eng-tips.com/vie...fm?qid=198474&page=1 http://www.eng-tips.com/vie...fm?qid=174690&page=1 http://www.eng-tips.com/vie...m?qid=173617&page=10

The first one is an extremely tame setup in which the guy's wondering why his boost falls off when he's pushing a T28 to 280 HP... It's completely maxed. Using a centrifugal SC the results will be closer to what you'd see with a stacked turbo setup, but you still stack the inefficiencies as well.

I'm not saying it doesn't work... just that it's not "all that" because of the stacked inefficiencies at high boost... which no one seems to get. Thermodynamics is a dying art, I guess.

quote by will: What am I regurgitating? I use my words, not someone else's.

Will don't blow a head gasket I was referring to myself...I was saying rather than regurgitate info I saw I will post the source. I remember debating this with you a while back on RFT...

quote will cont'd: If you're not running a "ridiculous" pressure ratio, what's the point of the extra weight and complexity? If WCF's project made such "absurd" power, how absurd was it? The car must have been on a dyno for tuning... If I knew anything about eng-tips, I might be there...

Extra weight and complexity are subjective, you can always get rid of some 'pork' some where else and complexity is just $$$ lol...imo. However you are right in the general sense it is not for every joe blow...
we did not put that car on the dyno we did a street tune, very conservative tune in short as per the owners request. It is all relative in any regards, I am not going to argue or debate the point. It was done, can be done...will it benefit the end user...Yes, but there is a threshold since the fiero cannot be easily aftercooled etc,etc. My point here is not really in conflict with yours..., if you are doing a compound setup especially in a fiero for high boost it is a waste of resources, if it is to push a very large turbine to do more work; that is one way amongst several to do it.
Thermodynamics still conserved

[This message has been edited by nocuttt (edited 12-13-2007).]