Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here.

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Old 10-12-2021, 07:37 AM
LM93 LM93 is offline
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Question How equal do exhaust manifolds need to be for a twin scroll turbo?

If you are trying to use a single turbo on a V8, the turbo will probably need to be located off to one side of the engine bay, right? If it is, then the exhaust from one bank of cylinders will have to have to travel much farther than the other. Does that mean that a twin scroll housing is impossible to run properly? Most info on the internet about twin scroll turbos are for inline 4s so I haven't been able to find a definite answer.

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1979 Esprit, Starting the Resto-Mod Process with a 350 and a TKO 600.

"And the one thing you can say about Capitalism is that, although it produces inequality-which it absolutely does-it also produces wealth, and all the other systems DONíT. They just produce inequality." Dr. Jordan Peterson
  #2  
Old 10-12-2021, 10:26 AM
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Tom Vaught Tom Vaught is offline
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Think about two freight trains (with the exhaust pulses being the "Box Cars").

One freight train has a one minute head start on the second freight train.
This is simulating the exhaust pulses from say the passenger side exhaust manifold and transfer pipe to the
split scroll housing being shorter vs the drivers side exhaust manifold and transfer pipe to the other inlet of
the split scroll turbo.

The energy pulses are like marbles traveling down a pipe. At high rpm are they are almost a solid stream
of pulses on the turbine wheel. Only at start-up before idle are they reaching the turbo wheel at different times.

The turbine wheel is driven by two "nozzle points" inside the turbine housing.
So if one nozzle point has the exhaust points hit the turbine wheel slightly before
the other turbine wheel at original crank and firing, no big deal.

As soon as the other bank of cylinders has starting its firing then the exhaust pulses
are from both sides of the engine. Now the pulses are both powering the turbing wheel equally.
It was only on the initial firing point of engine start when the pulses from the drivers side was not
helping the passenger side of the turbine housing.

Each pulse has energy so keeping the pipes fairly small keeps the response (spool) time of the turbo
shorter. But at some point they are both trying the equally drive the turbine wheel.

The gas travels thru the pipe at about 500 meters per second. This is 1500 feet per second.
So the difference in the two pipes in length, (say 12") or 1 foot difference or 1/1500 difference
in the initial time the first marbles got to the turbine wheel for the split scroll exhaust system
energy transfer to the turbine wheel.

It doesn't make any difference if the pipes are slightly different in length.
Some guys have mounted their turbos under the car and left the engine compartment
looking stock in street racing vehicles. Since the set-ups are mostly converter cars and
the guys are launching at higher rpm the "marbles" have been driving the turbine wheel
for a goodly period of time before the car/vehicle ever leaves. Again, not an issue.

Tom V.

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  #3  
Old 10-12-2021, 12:12 PM
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They dont! If they are way off just build and open plenum before it it’ll run fine. Your not trying to beat people by .001 here. I’ve seen guys w the ugliest crap log on one side and full on race header on the other and the cars runn like an animal . Don’t sweat it.

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Old 10-12-2021, 12:17 PM
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What is it your trying to accomplish with this build? Your goals will dictate how you need to build it. Most guys wayyyy over think the turbo build process, it’s simple, it’s easy, and it’s reliable . Just don’t ever break the golden rule-“ keep it fat and lazy! “ Meaning lots of fuel and don’t get greedy with timing or boost! It’ll live a long happy life.

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Happiness is just a turbocharger away!
960 HP @ 11 psi, 9.70 at 146.
Iron heads, iron stock 2 bolt block , stock crank, 9 years haven't even changed a spark plug!
selling turbos and turbo related parts since 2005!
  #5  
Old 10-12-2021, 03:18 PM
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Quote:
Originally Posted by turbo69bird View Post
Most guys wayyyy over think the turbo build process, itís simple, itís easy, and itís reliable .
SOME VERY GOOD ADVICE THERE.

Tom V.

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Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
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Old 10-12-2021, 04:00 PM
LM93 LM93 is offline
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Quote:
Originally Posted by turbo69bird View Post
What is it your trying to accomplish with this build? Your goals will dictate how you need to build it. Most guys wayyyy over think the turbo build process, itís simple, itís easy, and itís reliable . Just donít ever break the golden rule-ď keep it fat and lazy! ď Meaning lots of fuel and donít get greedy with timing or boost! Itíll live a long happy life.
500-600hp weekend cruiser/ track day road course. Nothing crazy. I just want to make sure the turbo system is made properly.

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1979 Esprit, Starting the Resto-Mod Process with a 350 and a TKO 600.

"And the one thing you can say about Capitalism is that, although it produces inequality-which it absolutely does-it also produces wealth, and all the other systems DONíT. They just produce inequality." Dr. Jordan Peterson
  #7  
Old 10-12-2021, 05:18 PM
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What is your assumption for the Turbo Size?
And the size of the engine I assume is the 350 cid engine in your signature?

Tom V.

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Old 10-12-2021, 05:44 PM
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Quote:
Originally Posted by LM93 View Post
500-600hp weekend cruiser/ track day road course. Nothing crazy. I just want to make sure the turbo system is made properly.
That’s a very easy set up to build and achievable on a very inexpensive budget too.
Remember when sizing a turbo compressor size is always better to be BIGGER than smaller. Smaller creates heat which is the enemy.

Remember when speaking to people about turbos that the terms boost threshold and turbo lag are many times used incorrectly.

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Happiness is just a turbocharger away!
960 HP @ 11 psi, 9.70 at 146.
Iron heads, iron stock 2 bolt block , stock crank, 9 years haven't even changed a spark plug!
selling turbos and turbo related parts since 2005!
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Old 10-12-2021, 05:50 PM
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Things you’ll need.
Turbo
Turbo headers
Wastegate
BOV
Hot side piping
Cold side piping
Boost referenced regulator
Oil drain back line of some kind possibly a tank and pump depending upon where it’s placed .
A carb set up for boost or EFI
A carb hat if using a carberator
A fuel pump that will pump enough fuel under boost a1000 for carb
Intercooler or water meth injection.

None of this has to be expensive especially these days .

__________________
Happiness is just a turbocharger away!
960 HP @ 11 psi, 9.70 at 146.
Iron heads, iron stock 2 bolt block , stock crank, 9 years haven't even changed a spark plug!
selling turbos and turbo related parts since 2005!
  #10  
Old 10-12-2021, 08:39 PM
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I have experience with road race vehicles and will say that a proper sized air to air
inter-cooler WILL BE REQUIRED with a vehicle that is raced more than a once a year on a road course.

Tom V.

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  #11  
Old 10-14-2021, 03:51 AM
LM93 LM93 is offline
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Quote:
Originally Posted by turbo69bird View Post
Remember when speaking to people about turbos that the terms boost threshold and turbo lag are many times used incorrectly.
From MotorAuthority.com:

"Let's start with boost threshold. That's the term to describe the engine speed required to produce enough exhaust gas flow that in turn generates the boost a turbo needs to start spinning and feeding air into the engine. So it's a level of engine speed where the turbo has positive manifold pressure. It's almost like a changeover point for a VTEC engine."

"On the other side of the turbocharger discussion, you'll find turbo lag. This describes the amount of time between the point when the throttle is opened and the turbo spools up. You're already operating the engine at a point past the boost threshold though, so that is not a factor in the turbo lag equation. Instead, turbo lag can be related to engine tuning, intake design, backpressure, and the size of the turbocharger itself. A larger turbo simply takes longer to spool up and deliver more boost."

Is this correct?

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1979 Esprit, Starting the Resto-Mod Process with a 350 and a TKO 600.

"And the one thing you can say about Capitalism is that, although it produces inequality-which it absolutely does-it also produces wealth, and all the other systems DONíT. They just produce inequality." Dr. Jordan Peterson
  #12  
Old 10-14-2021, 04:48 AM
LM93 LM93 is offline
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Quote:
Originally Posted by Tom Vaught View Post
What is your assumption for the Turbo Size?
And the size of the engine I assume is the 350 cid engine in your signature?

Tom V.
So, messing around with BW Matchbot puts me in the 68-78mm wheel size range. Borg Warner seems to be the only company that gives you a bunch of their compressor maps. Precision/Turbonetics don't, at least not online.

Definitely going to use an intercooler. I've seen some air-to-water setups with a heat exchanger that looked pretty slick. Even had dual fans on the forward IC wired to a switch on the dash for when you're stuck in traffic.

__________________
1979 Esprit, Starting the Resto-Mod Process with a 350 and a TKO 600.

"And the one thing you can say about Capitalism is that, although it produces inequality-which it absolutely does-it also produces wealth, and all the other systems DONíT. They just produce inequality." Dr. Jordan Peterson
  #13  
Old 10-14-2021, 05:43 AM
LM93 LM93 is offline
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Things youíll need.
Turbo: I have a general idea for what I need but I'll ask ask some experts to help get me the right trim, bearing, etc.
Turbo headers: I'm a welder, been doing a lot of CRES, CuNi, and NiCu piping on ships recently. I think I can fab some good headers. Use v-band clamps and bellows for heat and vibration.
Wastegate: I'll need two to keep the exhaust manifolds separate, right?
BOV: Will a blow-thru carb work better with one that vents to atmosphere or one that recirculates?
Hot side piping: Same size as turbo outlet, silicone couplers.
Cold side piping: Same.
Boost referenced regulator: Not one off ebay.
Oil drain back line of some kind possibly a tank and pump depending upon where itís placed:I'll have to get creative with plumbing.
A carb set up for boost or EFI: CSU, C&S.
A carb hat if using a carberator: Match the cold side piping.
A fuel pump that will pump enough fuel under boost a1000 for carb: Will I need an EFI tank or can I retrofit the original tank?
Intercooler or water meth injection: Air-to-water with a heat exchanger would be cool.

What else?
Cold air intake
boost gauge
Air charge temperature sensor
Exhaust gas temp sensor
Fuel pressure sensor
Are valve cover breathers fine or are there advantages of a PCV system with check valves and oil separators?

__________________
1979 Esprit, Starting the Resto-Mod Process with a 350 and a TKO 600.

"And the one thing you can say about Capitalism is that, although it produces inequality-which it absolutely does-it also produces wealth, and all the other systems DONíT. They just produce inequality." Dr. Jordan Peterson
  #14  
Old 10-15-2021, 09:03 AM
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Tom Vaught Tom Vaught is offline
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Quote:
Originally Posted by LM93 View Post
So, messing around with BW Matchbot puts me in the 68-78mm wheel size range. Borg Warner seems to be the only company that gives you a bunch of their compressor maps. Precision/Turbonetics don't, at least not online.
Back in the day,before Mr Bob Keller sold Turbonetics to the Wabtec, (A very large industrial engine company in Europe), and Wabtec purchased Precision Turbo, Turbonetics provided Turbo Maps in their catalogs.

When they and other companies went to the web all of that disappeared.

Precision did not have the capability to generate Turbo Maps like Turbonetics and Garrett. Borg Warner has been in the Turbo Business for some time but did not own any Turbo Businesses until they bought KKK in Europe and
formed the Boost department for BW. This Boost Department was led by
a former Garrett Boost Guy Tom Grissom. Grissom and Harry (Precision)
had been friends for many years. Grissom was Director of all BW Turbo
Systems in the world until he retired.

Tom V.

Matchbot is a good program.

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Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
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