Who wants to get supercharged?

[headpunter]

Originally Posted by Rekt

But I thought they were still a roots blower, and not a true twin screw?

the new ones are High helixed twin screws

[GTAHVIT]

All of these aftermarket "under the hood" blowers are twin screw. Except centrifugal blowers.

I think where the confusion comes in is Whipple claims they are "roots style" blowers but in reality all twin screw are, exactly that, "roots style" blowers.

The difference is a Roots blower's impeller lobes are not twisted like they are in a twin screw, hence the name twin screw. And roots blower are much bigger and capable of producing much more boost.

Looking for some pics... brb

This is a true Roots blower taken apart. The impellers or in the upper right hand corner of the pic. Notice they aren't twisted around the center axis.



This is a twin screw. You can see how the impellers are twisted.



At least that is my understanding of the major difference.

Edit:

Spike???

[Rekt]

Originally Posted by gtahvit

All of these aftermarket "under the hood" blowers are twin screw. Except cetrifugal blowers.

I think where the confustion comes in is Whipple claims they are "roots style" blowers but in reality all twin screw are, exactly that, "roots style blowers.

the difference is a Roots blower's impeller lobes are not twisted like they are in a twin screw, hence the name twin screw. And roots blower are much bigger and capable of producing much more boost.

Looking for some pics... brb

Ok, this makes sense as well.

I just read on Whipple's homepage that it compresses air between the lobes and housing, where I thought it compresses air between the lobes.

I posted before this, but I deleted the message because I felt that it was inaccurate.

[GTAHVIT]

Originally Posted by Rekt

Ok, this makes sense as well.

I just read on Whipple's homepage that it compresses air between the lobes and housing, where I thought it compresses air between the lobes.

I posted before this, but I deleted the message because I felt that it was inaccurate.

My understanding is they all compress air between the housing and the lobes. Obviously the lobes are what draw the air in to the housing at a greater volume yet less density then it pushes it into the engines intake.. You need both the housing and the impellers to do this. roots, screw, turbo, centirfugal or otherwise.

My apologies if I'm telling you stuff you already know.

[Rekt]

Originally Posted by gtahvit

My understanding is they all compress air between the housing and the lobes. Obviously the lobes are what draw the air in to the housing at a greater volume yet less density then it pushes it into the engines intake.. You need both the housing and the impellers to do this. roots, screw, turbo, centirfugal or otherwise.

My apologies if I'm telling you stuff you already know.

Don't be sorry. I appreciate the clarification. I just got a little confused about the exact operating principles.

[Ad Wizard]

Originally Posted by headpunter

the new ones are High helixed twin screws

That's good to know! After dealing with a "Heaton" roots-style supercharger for a number of years, and seeing the crazy power gains and efficiency of a twin screw, I'm sold on 'em.

This hasn't been asked in this post, but what would the max, safe boost be on a non-forged, high-compression engine like the Camaro's? Maybe 6-8psi? What would that give you in horsepower? 100 or so extra ponies? I'm in the dark here, so maybe Wm Holden or others can fill me in.

My point is that it's gonna be hard to justify a $6000 (at least) supercharger on a stock motor when a hot cam will get you maybe 50hp for under a grand installed. If I'm gonna do this, I want to do it right - which means forged internals and lower compression slugs, so I can safely run LOTS of boost!

[GTAHVIT]

My personal opinion is, for the money you will spend, I'd go with bolt on mods like Cam, intake, exhauts, tune on the LS3. You will spend much more money on a blower but be very boost limited due to the high CR. so in the end you can get over 500HP with out it.

Not to say that blowers are bad. In fact I'm gonna do everything i can to get one. But, you don't really get the max available performance from a blower unless you are gonna lower the CR.

my .02

[headpunter]

Originally Posted by gtahvit

My personal opinion is, for the money you will spend, I'd go with bolt on mods like Cam, intake, exhauts, tune on the LS3. You will spend much more money on a blower but be very boost limited due to the high CR. so in the end you can get over 500HP with out it.

Not to say that blowers are bad. In fact I'm gonna do everything i can to get one. But, you don't really get the max available performance from a blower unless you are gonna lower the CR.

my .02

im lost, what engine are we talking about? 10.7 isnt that bad for a Supercharged engine. holden HSV cars and corvettes get 600-700hp without tearing the engine down.


that said i am going to be doing a cam, exhaust, intake on mine to drive for a while before i get a twin turbo for my camaro.

[GTAHVIT]

Originally Posted by headpunter

im lost, what engine are we talking about? 10.7 isnt that bad for a Supercharged engine. holden HSV cars and corvettes get 600-700hp without tearing the engine down.


that said i am going to be doing a cam, exhaust, intake on mine to drive for a while before i get a twin turbo for my camaro.

I'm really saying that forced induction is a great way to get the max power out of your engine. However, You will not get Max productivity out of a blower when you put it on a High CR engine.

Man, I don't really want to start this argument again.... Oh well here goes.

Hence the reason the LS9 gets 630+ HP with a CR in the low 9's, while a LS7 gets 500+ HP with a CR in the low 11's

And yes, there are a ton of other factors that contribute. I'm just making a generalization.

So, without saying FI is better than NA, or vice verse, I'm really saying you don't get the most out of a blower/turbo unless you have a lower CR.

Does that make sense or did I just confuse the issue?

[PatrickfromMD]

I have to agree with gtahvit on the compression ratio issue. The LS3 is on the higher side of the range therefore limiting the amount of boost you can use with pump gas before detonation occurs.
You asked how much boot equates to how much HP. Understanding that normal atmospheric is 14.7 psi, and an engine works like an air pump, the general rule I would follow is that for every 14.7 psi you can add in the form of boost (maintaining the same incoming charge temperature)doubles your horsepower, and does it at relatively the same rpms. (this excludes some variables like the losses needed to drive the forced induction, and ignores that most normally aspired engines don’t achieve 100 volumetric efficiency anyway). Still the rule is a good ball park. So, if you add say half that (i.e. say around 7.5 psi) you are adding like 50% more power, or making a 6 liter motor believe it’s a 9 liter motor. (ever wonder how Wm Holden came up with that comment on his signature). We use intercoolers to bring the temperature back down after compressing it, as air looses density as its heated (not to mention increased chance of detonation) and this must also be factored in. I’m also watching to see what a practical limit for a bone stock engine, and so far I’m leaning towards 6-7 psig. (keep in mind, if you choose your modifications carefully, you can also combine some traditional modifications to a FI engine

[GTAHVIT]

Originally Posted by PatrickfromMD

I have to agree with gtahvit on the compression ratio issue. The LS3 is on the higher side of the range therefore limiting the amount of boost you can use with pump gas before detonation occurs.
You asked how much boot equates to how much HP. Understanding that normal atmospheric is 14.7 psi, and an engine works like an air pump, the general rule I would follow is that for every 14.7 psi you can add in the form of boost (maintaining the same incoming charge temperature)doubles your horsepower, and does it at relatively the same rpms. (this excludes some variables like the losses needed to drive the forced induction, and ignores that most normally aspired engines don’t achieve 100 volumetric efficiency anyway). Still the rule is a good ball park. So, if you add say half that (i.e. say around 7.5 psi) you are adding like 50% more power, or making a 6 liter motor believe it’s a 9 liter motor. (ever wonder how Wm Holden came up with that comment on his signature). We use intercoolers to bring the temperature back down after compressing it, as air looses density as its heated (not to mention increased chance of detonation) and this must also be factored in. I’m also watching to see what a practical limit for a bone stock engine, and so far I’m leaning towards 6-7 psig. (keep in mind, if you choose your modifications carefully, you can also combine some traditional modifications to a FI engine

great post.

Question: In reference to the bold text above, I've heard that you should be careful when choosing a cam for blown applications. Do you think the GMPP Hot cam for the LS3 will be good for FI or not?

[Wm Holden]

The Cam in the GTO is stock high lift high duration...and is a nice mate with blower...much better match then we expected...and obviously a GM design (duh)

[Ad Wizard]

Originally Posted by gtahvit

I'm really saying that forced induction is a great way to get the max power out of your engine. However, You will not get Max productivity out of a blower when you put it on a High CR engine.

You nailed it exactly. Which is why I would want to reduce the compression ratio if I ever add a blower.

Wm Holden, thanks for posting your dyno numbers. I have some questions for ya. First, it looks like you are putting down 480 to the wheels, which, in my mind is about 550 crank (considering the typical 15% drivetrain loss). So that's about 150hp gain from stock on 7psi? That's better than I thought! Also, what's with the torque reading? It looks like you are putting down 1,500 ftlbs.

[Wm Holden]

Originally Posted by Ad Wizard

You nailed it exactly. Which is why I would want to reduce the compression ratio if I ever add a blower.

Wm Holden, thanks for posting your dyno numbers. I have some questions for ya. First, it looks like you are putting down 480 to the wheels, which, in my mind is about 550 crank (considering the typical 15% drivetrain loss). So that's about 150hp gain from stock on 7psi? That's better than I thought! Also, what's with the torque reading? It looks like you are putting down 1,500 ftlbs.

first...you are welcome

I've been seeing A4's estimated at 20 to 18% DT loss...so 19%x600hp=114
600-114=486rwhp...that's my math for it.
And yes a 50% increase is way more then heads and cam..or whatever really...once I looked at the cost per horse and threw out Nitrous....
F/I was my only choice possible AND PASS SMOG.


PS divide torque numbers by my rear ratio and we see 460 rwtq....