Turbo vs. Blower psi?

[Jthomas]

Ok so im at carshows meeting people or surfing the forums, they have turbos, and they all tell me they are running like 20+ lbs of boost. And some of these people have little 4 bangers, stock for the most part. And I ask how can they run 20lbs? It's still boost, it's measured the same way as roots. How can they do it. They tell me, turbo boost is way different than blower boost. HOW? ITS STILL BOOST MEASURED IN PSI

I have a blown BBC,  flat top blower 8.5:1 pistons,  @3-5lbs on pump gas. If I put much more boost on my engine I'd either have to run race fuel or change the pistons again.

So again, how are the two different in the terms that they can run 20+psi on a pretty much stock motor?

Thanks alot

[J.C.]

I know water alcohol injection helps alot with detonation... Eroq on here knows a bit about them

[xjs3667]

I've always wondered the same thing....Im running 6psi on my blower and run 110 octane.... It will run with 91, but she dont like that ......   I know with vortech superchargers they run a pretty high boost level, like turbos, but vortec superchargers don't have to much effect in low rpms, unlike a turbo that you can spool up.  Another thing I know is that roots blowers are direct drive from the engine, so I'm thinking this might have something to do with it???

[Jthomas]

I've always wondered the same thing....Im running 6psi on my blower and run 110 octane.... It will run with 91, but she dont like that ......   I know with vortech superchargers they run a pretty high boost level, like turbos, but vortec superchargers don't have to much effect in low rpms, unlike a turbo that you can spool up.  Another thing I know is that roots blowers are direct drive from the engine, so I'm thinking this might have something to do with it???

I run 93 octane no prob.

a roots style blower is a "pump" there is no pressure within the case. All the pressure is in the manifold. There are two other kinds of superchargers, a screw charger, wich is where the rotors look pretty much like corck screws or wood screws if u will. all the pressure is built in the case. The centrifugal  super charger or the "vortec charger" are both the same. It works like a turbo, except is driven from the serpent belt. And the pressure is made within the case. That's the difference between turbos and supers. Supers are all belt driven and have a parasitic effect on the motor.  Bt in bothe the screw and centrifugal, they create a ton of boost, but not that much power from off idle or low rpm power like a roots. A 671 pushes like 640" of air in 1 rotation. But all I have to do to make more boost it change my pulleys and overdrive it, or get a bigger blower.

But I still want to know how these ricers are getting away with it.

[Jthomas]

I know water alcohol injection helps alot with detonation... Eroq on here knows a bit about them

My old man runs alcohol injected on his drag boat. He likes it so much more than gas, no detonation. He's got a billet 16-71 on there and it's overdriven a ton, idk what kind of boost is on it. But it runs like 2000+ hp

But that's the difference between gas and alky- no detonation  you can run an engine to it's limits with the comp ratio and boost.


I remember when I was a kid I had one of them nitro rc trucks
one day I come home from school all pumped to play with it. All my nitro was gone. I asked dad what happened to it. 
Dad -"oh yea bout that, I was running low on f-"
Me-"enough said." disappointment.

[Eroq]

higher boost, requires higher octane to eliminate detonation.  20+lbs your looking at some expensive fuel!

Super chargers are great because they provide boost nearly right off the line, but do require horsepower to run...

turbos are great too because they use "wasted" energy... exhaust flow, and HEAT!   you want the exhaust hot before the turbo and cold after the turbo... the temp drop results in more flow... compressor turbine spins more.

its all really pretty easy.. if you are seriously considering BUILDING a system, buy a book and read it. word for word, every page. You will learn TONS.  one book i bought was Maximum Boost - written by Corky Bell.  Alot of it carries over from blowers to turbos. Diagrams with air flow rates. pressure drop charts, anything you would need.

Or you can buy a turbo setup... but i know we are all on a budget and cant afford a $5000 turbo kit!

[Jthomas]

higher boost, requires higher octane to eliminate detonation.  20+lbs your looking at some expensive fuel!

Super chargers are great because they provide boost nearly right off the line, but do require horsepower to run...

turbos are great too because they use "wasted" energy... exhaust flow, and HEAT!   you want the exhaust hot before the turbo and cold after the turbo... the temp drop results in more flow... compressor turbine spins more.

its all really pretty easy.. if you are seriously considering BUILDING a system, buy a book and read it. word for word, every page. You will learn TONS.  one book i bought was Maximum Boost - written by Corky Bell.  Alot of it carries over from blowers to turbos. Diagrams with air flow rates. pressure drop charts, anything you would need.

Or you can buy a turbo setup... but i know we are all on a budget and cant afford a $5000 turbo kit!

I know how turbos work and how to rig em. But I was just currious about my question. I was doing some extra research, Somone said it's because its not the psi, it's the airflow.

But as far as superchargers go, I'm pretty good with em. I built a few and converted em from diesel to gas, I'm pretty good with their boost levels and air ratios. But I know if you added a chiller to a blower that's like an instant 100hp

[ice87]

I never thought there was a difference. 20psi is 20psi. But I see where you went wrong. They told you that's what they are running. Ask them for a dyno sheet and that should shut up 95% of them.

[Jthomas]

I never thought there was a difference. 20psi is 20psi.

That's what I thouht.


But what I was told is that some turbos are forcing small amounts of air into the engine @20psi. Not like a 671 where it's 640"s at 1 revolution.

[Jthomas]

So idk what to think

[J.C.]

turbos spin alot faster then a roots, and have smaller area to compress the air

[Jthomas]

turbos spin alot faster then a roots, and have smaller area to compress the air

True. And roots aren't compressers.  They are pumps. All the pressure is made in the manifold.

[J.C.]

turbos spin alot faster then a roots, and have smaller area to compress the air

True. And roots aren't compressers.  They are pumps. All the pressure is made in the manifold.

there ya go!

[xjs3667]

Thats what I'm thinking, It takes more pressure for the turbo to put same amount of air in as a blower at lower psi,

[Jthomas]

My mistake. I think a 671 is 411"s per rotation.

[Jthomas]

I guess just the though irritates me. Like I spend twice the $$ in just engine parts, I have twice as Many cylinders, big cubes.

And I look at vids on YouTube of like a 1000HP Honda. And I'm just like. Wtf... Just by the looks, it's just a big ass turbo. Now I assume there are engine mods.        But if that were on a built v8?

[ice87]

OK sorry but the 1000hp Honda's are not your everyday Honda. Lots of money into those builds. Look at the new ls/vortec motors. Change exhaust, valve springs and fuel system and you can run 600+ on a complete stock motor. I also think you could run more psi in your motor but need a nice ignition system so you can pull more timing out with the higher boost.

[ice87]

Your question got me thinking and I couldn't figure it out but the is the best I could find on the web.
PSI is half the equation, the other is flow, or CFM. Think of it like a pressure washer. You have one with 3000 psi (the pressure at the tip) and 2.5 gpm (how much water it flows out over a minute). The 2 work together to determine what you can clean. You could have 1,000,000 psi, but at .001 gpm, you aren't going to clean anything. So a turbo's efficiency will depend on how much boost pressure it can achieve, as well as the total volume of air it can move. 35 psi sounds like a lot, but is unimpressive if its only moving 50 cfm. Make sense? For best results, you want a properly sized blower. Too large a supercharger will create a flow restriction, costing hp. Too large a turbo will cause extreme lag. A large turbo is slowly building pressure (and power) but it still gets there. A garret T91 is too big for a 1.6L Civic, but if it eventually spun, it would make big power and a big explosion

[Jthomas]

Your question got me thinking and I couldn't figure it out but the is the best I could find on the web.
PSI is half the equation, the other is flow, or CFM. Think of it like a pressure washer. You have one with 3000 psi (the pressure at the tip) and 2.5 gpm (how much water it flows out over a minute). The 2 work together to determine what you can clean. You could have 1,000,000 psi, but at .001 gpm, you aren't going to clean anything. So a turbo's efficiency will depend on how much boost pressure it can achieve, as well as the total volume of air it can move. 35 psi sounds like a lot, but is unimpressive if its only moving 50 cfm. Make sense? For best results, you want a properly sized blower. Too large a supercharger will create a flow restriction, costing hp. Too large a turbo will cause extreme lag. A large turbo is slowly building pressure (and power) but it still gets there. A garret T91 is too big for a 1.6L Civic, but if it eventually spun, it would make big power and a big explosion

Okay I think I'm getting all this. But they still make power? But again they are always poping head gaskets.  the ricer is a whole other breed of car enthusiast.
If I were ever to get a 4 cylinder it would be the old school vega.

But as far as my ignition, I don't want to spoil any surprises for the build. But it's good. Trust me

I got really nice flowing heads, and everything i have will work great with one another.

[ice87]

Well I did alot of researching about putting a Turbo on my bike and alot of tuners don't pull enough timing when they up boost. So it goes off before it should messing up pistons and heads.