Turbo or Supercharger?

[k-man]

my friend installed dual turbos in his car and it worked well and was compact, no holes in the hood for some huge supercharger. What he liked best was how he could adjust the amount of boost with a small control panel inside his car so he kept it fairly low for most of his driving and could turn it up when he wanted to race. The exhaust piping was pretty difficult though, his brother does custom exhaust so he did it but otherwise it would have cost him a fair bit.

 

[DeltaT]

I went with a built 383 and a centrifugal blower. I can't say it's the best combo out there but the two are very complementary - the 383 has great off the line torque (had to get drag radials to hook well) and the blower yields a god-awful mid and top-end push.

If I had more low-end torque I wouldn't be able to hook up with less than full slicks.

But this way, I have a good driving car that turns into an ungodly beast when I want, but then drives like stock when I relax.

Not saying it's the best, but it sure is a streetable combo.

And I've beaten a lot of cars that have more of something but can't put it to the street.

On top of that, mine still handles well. There are quicker cars around but I wouldn't want to take a high-speed off-ramp with them (or have them anywhere near me on one).

Jim

 

[cleetus]

Can you safely run a turbo or blower on a street car (92-3) octane with 10.5:1 compression, or do you need to lower the compression? Running a single digit boost number is probably not worth the gain in the end.

I've been throwing around the turbo idea for some time, but wonder if I'd have to completely rebuild with deeper pistons.

 

[basketcase]

Can you safely run a turbo or blower on a street car (92-3) octane with 10.5:1 compression, or do you need to lower the compression? Running a single digit boost number is probably not worth the gain in the end.

I've been throwing around the turbo idea for some time, but wonder if I'd have to completely rebuild with deeper pistons.

10.5 seems high, I know of a couple of 9.5:1 Motors.

Depending on your cylinder head combustion chamber cc, you may be able to put on a bigger chamber to lower your compression vs. changing pistons.

 

[onefastermonte85]

centrif and be done with it

 

[cleetus]

But a blower has the same issues, no? 10.5:1 is still high for a blower motor isn't it?

 

[basketcase]

But a blower has the same issues, no? 10.5:1 is still high for a blower motor isn't it?

Boost is boost, doesn't matter what creates it. If you want to run high compression and boost, look into alky, alky injection, and/or coating your pistons and combustion chambers

 

[Robert1320]

But a blower has the same issues, no? 10.5:1 is still high for a blower motor isn't it?

Boost is boost, doesn't matter what creates it. If you want to run high compression and boost, look into alky, alky injection, and/or coating your pistons and combustion chambers

True, a turbo isn't free hp but a blower will use more hp to make power than a turbo.

 

[Anonymous]

a turbo isn't free hp but a blower will use more hp to make power than a turbo.

and we know this how? we can measure how much power it takes to turn a blower but we have no way of measuring how much the turbo is choking the engine. don't forget boost on charge side is restriction on exhaust side.

 

[Robert1320]

and we know this how? we can measure how much power it takes to turn a blower but we have no way of measuring how much the turbo is choking the engine. don't forget boost on charge side is restriction on exhaust side.

This a quote from a Engineer that work with this daily and a great read.

I will try and give as HONEST of an answer as I can if we can specify a few parameters.

Lets say your F1R can make 1000 hp based on moving a given amount of air at the same 25 psi in the Intake Manifold.

You will never see that 1000 hp in real life (in this example) as the supercharger is belt driven and consumes a given
amount of HP that the engine is making.

It is a well known rule of thumb that it takes about 1 hp to move 1 lb of air.

A supercharger has other losses from the belt and from the mechanical parts in the supercharger so 15% added to
the "Air Power hp number.

Supercharger Flywheel hp would be:

100 lbs of air moved makes 1000 hp minus 100 hp to move the 100# of air plus 15 hp for the other losses =

1000hp - 115hp = 885hp at the flywheel (Given the right camshaft, same heads, right exhaust, right timing, etc)


Now we do the Turbocharger

Same rule of thumb of 1 hp to move 1 lb of air.

A Turbocharger has other losses (No belt or mechanical losses but it does have back pressure)

BUT WE DO HAVE EXHAUST ENERGY AND EXHAUST TEMPERATURE

Turbocharger Flywheel hp would be:

100 lbs of air moved makes 1000 hp minus about 15 hp for exhaust back pressure =

1000hp - 15hp = 985hp at the flywheel (Given the right camshaft, same heads, right exhaust, right timing, etc)

If we assume the common rule that 1/3 of the total energy goes through the mechanical parts, 1/3 goes out of
the exhaust, and 1/3 goes into the cooling system we can then assume that the exhaust contributed the 100 hp
that drove the Turbine wheel and therefore the compressor wheel to move that 100 lbs of air per minute.

IF you do not have the right camshaft, IF you do not have a proper Turbo Manifold system, IF you do not have the
right exhaust system after the Turbo, the numbers will change just like they would on a "Belt System" if you made
a mistake there.

A Turbo will make the same heat across the compressor side of the turbo moving the same amount of lbs of air but
there will be a very slight increase in temp from the center housing oil cooling and water cooling not being 100%
efficient. But the number is a small difference.

A Turbo will always make more power at the flywheel vs a "belt car" as the turbo is using (as was mentioned FREE
POWER from the exhaust).

About as honest as I can be.