50 PSI boost, 15:1 compression on gasoline?

[McRat]

I've been kind of out of the loop with what the drag racers are doing with gasoline.

But somebody is trying to convince me they are running 50psi supercharger boost pressure with 15:1 pistons on race gasoline???

Has technology changed that much? 

Sounds extreme to me. 

This sounds like a statement based on "advertised" ratings.  You can buy 15:1 "advertised" pistons for almost anything, but the actual static ratio is a function of real volumes.  If he's using open chamber heads, he may actually only be achieving 10:1, for argument sake.
 
Keep in mind that 15:1 static doesn't equal 15:1 actual.  I'd ask what his cam timing is.   

I'd calculate my cylinder/head volumes to determine my actual static CR before I'd assume anything.  You can read the boost gage, but you've got to know your volumes.

My school of thought on that, is if I really wanted 50psi in a gasoline engine, I'd go with the lowest possible compression that would still allow the engine to run at a high idle.  I'd get slightly more fill in the cylinder, and less peak pressure to lift the head or bend the rods.  When I ran a turbo Kaw 650, I ran 6.9:1 Ross pistons for 30PSI boost.

[jl222]

Why do people relate "boost" to power?

I works for me!

Yes, we run 15:1 and 60psi boost, but that's diesel.  I can't imagine the piston on a gas engine getting very far up before autoignition.  Yeah, direct injection might do it, but I don't think racers are running it at the drags yet.

So, if I have a t-3 turbo and a t-18 turbo running 20 lbs or 72" in/hg why won't they make the same horse power?

Drive pressure and compressor efficiency are part of the tuning process when selecting turbos.  Run it off it's map, and low HP won't be your biggest concern.  Been there, done that have have the T-shirt.

 

I'm running a compound setup for testing purposes, a GT4202R + GT5533R.  While both are in the center of their maps (using a turbo RPM sensor), it seems I'm not working them equally.  So I'm making a change and running them again. 

  Compounding to me and the aero guys is when you run the exhaust into the tubine [no compressor side] and gear it back to the crank. The Wright R3350 had this setup right after World War 11 and they gained 20% hp. This type of system is what they're talking about in the SCTA rule book under supercharging. Since its not really supercharging they didn't want anybody doing this in the unblown classes. From what I understand the late Bruce Johnson had this rule inserted. Blowing one blower into another is called stageing. but I know a lot of diesel guys call it compounding.I believe Detroit Diesel is compounding their new engine but still using the compressor side and picked up 50 hp.

    JL222

        

[dwarner]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

[McRat]

Why do people relate "boost" to power?

I works for me!

Yes, we run 15:1 and 60psi boost, but that's diesel.  I can't imagine the piston on a gas engine getting very far up before autoignition.  Yeah, direct injection might do it, but I don't think racers are running it at the drags yet.

So, if I have a t-3 turbo and a t-18 turbo running 20 lbs or 72" in/hg why won't they make the same horse power?

Drive pressure and compressor efficiency are part of the tuning process when selecting turbos.  Run it off it's map, and low HP won't be your biggest concern.  Been there, done that have have the T-shirt.

 

I'm running a compound setup for testing purposes, a GT4202R + GT5533R.  While both are in the center of their maps (using a turbo RPM sensor), it seems I'm not working them equally.  So I'm making a change and running them again. 

  Compounding to me and the aero guys is when you run the exhaust into the tubine [no compressor side] and gear it back to the crank. The Wright R3350 had this setup right after World War 11 and they gained 20% hp. This type of system is what they're talking about in the SCTA rule book under supercharging. Since its not really supercharging they didn't want anybody doing this in the unblown classes. From what I understand the late Bruce Johnson had this rule inserted. Blowing one blower into another is called stageing. but I know a lot of diesel guys call it compounding.I believe Detroit Diesel is compounding their new engine but still using the compressor side and picked up 50 hp.

    JL222

        

Yup, then I would be called staged (non-sequential).

All the two-stroke Detroit Diesels are super-turbocharged (staged).  But for a different reason.  They can't run without the crankcase blower.

When you hear of a 6-71 blower what that is the supercharger off a Detroit two-stroke.  It's sized for 6 cylinders of 71ci each.

[McRat]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

Dan, are you saying that running one turbo into another is not permitted in DT class?  I assumed it was legal since they've been running that way, even in 2008.

[jl222]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

  Dan

  My rulebook does not have the word ''staging'' in it. Staging is part of supercharging, turbo compounding is'nt. No compressed air goes into the engine.

  JL222

[dwarner]

Crap, there goes my afternoon. I'll get back to you.

DW

[McRat]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

  Dan

  My rulebook does not have the word ''staging'' in it. Staging is part of supercharging, turbo compounding is'nt. No compressed air goes into the engine.

  JL222

I think it's a difference in semantics that is causing a problem.  In diesel pickup lingo:

Single - Normal.
Sequential - Two turbos, one does low CFM boosting, then the other does high CFM boosting.  This is to increase the effective map range.  New Ford is one.
Twinned or Compound - A big charger feeds a little charger to generate more boost than a single will.
Parallel twins - For those need a lot of low pressure air augmented by nitrous.  Very rare.

Detroit diesels aren't diesel pickup engines, they are super-turbocharged in a compounded layout.  The turbo feeds the supercharger to amplify boost.

[McRat]

Crap, there goes my afternoon. I'll get back to you.

DW

No biggie Dan.  Don't worry about it.  I can run either way at the same power I found out.  If there are questions, we can address them at El Mirage.

[McRat]

Crap, there goes my afternoon. I'll get back to you.

DW

One point to ponder if you ask around, is that if they outlaw diesel "big/little" twins in DT, a real Ford diesel pickup (stock) is illegal in diesel pickup class as sold, since that would meet the definition of staged.  All the Detroit engines would be outlawed as well.

[jl222]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

Dan, are you saying that running one turbo into another is not permitted in DT class?  I assumed it was legal since they've been running that way, even in 2008.

 McRat
 All the rule is saying is if you turbo compound it puts you in supercharge class. What so bitchen about Bville you can do
anything you want with supercharging including running one blower into another +another + another if you want + turbo compound if you want.

    JL222

[McRat]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

Dan, are you saying that running one turbo into another is not permitted in DT class?  I assumed it was legal since they've been running that way, even in 2008.

 McRat
 All the rule is saying is if you turbo compound it puts you in supercharge class. What so bitchen about Bville you can do
anything you want with supercharging including running one blower into another +another + another if you want + turbo compound if you want.

    JL222

Yes, the class I run in allows all forms of supercharging as I read it, and that's how they've been setting up the trucks.

[jl222]

John is correct. Bruce added the staging/compounding rule when he was the head tech guy. In the SCTA rulebook staging/compounding is the same thing.

DW

  Dan

  My rulebook does not have the word ''staging'' in it. Staging is part of supercharging, turbo compounding is'nt. No compressed air goes into the engine.

  JL222

I think it's a difference in semantics that is causing a problem.  In diesel pickup lingo:

Single - Normal.
Sequential - Two turbos, one does low CFM boosting, then the other does high CFM boosting.  This is to increase the effective map range.  New Ford is one.
Twinned or Compound - A big charger feeds a little charger to generate more boost than a single will.
Parallel twins - For those need a lot of low pressure air augmented by nitrous.  Very rare.

Detroit diesels aren't diesel pickup engines, they are super-turbocharged in a compounded layout.  The turbo feeds the supercharger to amplify boost.

 McRat

  Hears your chance to create a new diesel term for gearing a turbine back to the motor

    JL222

[McRat]

Turbine pressure recovery! 

[jl222]

Turbine pressure recovery!