Forced Induction

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Revision as of 09:28, 27 August 2013

Forced Induction comes in two forms: Supercharging and Turbo-supercharging. Both work well in a Datsun 1200!

Overview

Also see:
* Turbo
* SC14

discussion: s/charged a14

One thing to remember is that a method that works well isn't the only good way.

Wuote: Forced induction. This is a subject that was vigorously & robustly debated in an extensive thread not so long ago, so have a play with the search function & you will likely find it. Myself, & a few others prefered the ability of the positive displacement blower to deliver high levels of torque, almost instantly, at very low engine speeds, while a large number of others prefered the advantages that a turbo offers at higher engine speeds. The turbo debate was further broken down into blow through versus suck through. See if you can find this thread & have a read through it all. With some luck ou will gain an insight of the advantaged & disadvantages offered by each system.

The big discussion: regarding Turbocharging A12. Caution: difficult reading in that discussion.

ddgonzal summary from thread:

Intercooler

- Not needed. The first three years of the Porsche 911 Turbo didn't have one (75-77), yet this 3.0 liter turbo outperformed 7.5 liter NA cars. - Intercooler is worth it as it significantly reduces the temperature of the compressed air, which increases the boost possible with a given octane fuel - Using an aluminum radiator should be better than nothing. Unless someone actually tested this, we are all just guessing. Radiators can flow a lot of water, and air is easier to pump ... so air should flow through w/o significant restriction. Putting this in front of the car should allow some cooling effect, although obviously not as a much as a purpose-designed cooler. - An alternative is to use water or alcohol injection. Some OEM applications used water injection (ex. 1962 Oldsmobile Jetfire)

Wastegate

- Used for adjustable control over boost pressure. When the set pressure is exceeded, exhaust is routed around the turbine to go out the tailpipe - Not needed if you carefully size the turbo to the application (ensuring that at maximum rpm, design boost is not exceeded). Older OEM applications used this method.

Blow-off valve (or recirculation valve)

- preventing the turbo from surging, for example during gear shift or whenever throttle is closed - Porsche uses these, so obviously they work a Blow-off intake boost to atmosphere. Boost is lost. Simple, inexpensive b.Blow-off to compressor inlet (recirculate back through turbo inlet). Used to enhance throttle response: Boost is kept in circuit for immediate availability when throttle is opened again

Carb setup

- Injection is better, allowing better control of mixture - Draw through was used by many OEM setups. It is reliable, and the simplest otpion. The downside is you can't use an intercooler, as the fuel will condense in the cooler. - Blow through works well. The main reason to use this over a draw-through is so an intercooler can be used. a Boxing carb. This allows a more or less stock carb to be used, the outsided pressure balancing the inside pressure b Unboxed carb. This was a popular OEM method. phunkdotaspok says this can handle 10 psi with a good top-gasket seal. In an NA application, a warped top is not a problem, as there is no pressure in the float chamber. This only becomes important in boosted application. - Need richer jets to keep air charge cool and prevent detonation

Fuel pump

- Stock fuel pump is good for draw-through setup. It's not enough for a blow-through setup, as 2.5 boost would overpower the fuel pressure - Using a low-pressure (15 psi) electric pump oughta be good for a 10-12.5 psi boost. - Needle and seat has trouble holding more than 10 psi fuel pressure. Better to use a secondary 15-psi pump to cut in only when needed. - Best setup is to use a rising-rate regulator with a high-psi pump. Excess fuel is returned to the tank.

Turbos

- T3 is pretty big for an A12. Needs high rpm, head work, etc - Mid-80s Nissan Pulsar turbo (E15 engine) has integral wastegate - go_the_datto actually tried Daihatsu diesel 1.0 turbo on A12. Good response in lower rpm ranges. Two make better twin-turbo application for A12

Boost pressure

- 6-7 psi is what a lot of OEM applications use. - 10 psi should be possible with a stock A12/A14 - 14.7 lbs gives theoretically double the airflow so max. power would be about 2x stock, but this isn't actually the result. The reason is that the stock induction and exhaust system won't flow this much air under pressure. However, the low rpm torque could approach 2x (at about 2250 rpm) if a small turbo is used. So a 130hp turbo engine will have much more performance than a 130hp NA engine - 1986 Honda 1.5 liter ran boost of 4.0 bar - that's 300 bhp ... per cylinder with special fuel

Toyota 4A 1600cc engines

- Word is that the the 4AF has not much more power than an A15 - 4AGE (double-overheard cam) Impressive power - 4AGEZ supercharged. Use this motor and its fuel system and computer for a turbo setup. The advantage over the supercharger is that boost can be variably controlled per the wastegate. A supercharger has a fixed design boost.

Supercharging vs. Turbocharging -- what's better?

Turbocharging generally makes more power as the engine revs higher. So does centrifugal supercharging (paxton, etc).

By contrast, a rootes-type blower, twin-charger or screw-charger makes power all through the RPM range and so makes the engine feel like a larger displacement engine. It also does not suffer from lag like a turbo does.

B&M blown A14 (rootes-type supercharger)

B&M supercharged NAPS-Z engine (rootes-type blower)

Centrifugal supercharger (belt-driven turbine)

Compound Supercharging concept

Twin-Turbo A12

Draw-through vs Blow-through

You can put the carburetor before the blower (draw-through) or after the blower (blow-through).

Intercooler

An intercooler can result in far more HP, but requires a blow-through system (boxed carburetor) or EFI port injection. This is because for safety you don't want air-fuel mixture going through the cooler.

Boost pressure

• 6-7 psi is what a lot of OEM applications use.
• 10 psi should be possible with a stock A12/A14
• 14.7 lbs gives theoretically double the airflow so max. power would be about 2x stock, but this isn't actually the result. The reason is that the stock induction and exhaust system won't flow this much air under pressure. However, the low rpm torque could approach 2x (at about 2250 rpm) if a small blower is used. So a 130hp forced induction engine will have much more performance than a 130hp NA engine

Induction and Exhaust

Obvious, for more airflow, a higher flowing carb, intake, heads (ports and valves) and exhaust system is beneficial.

Supercharging will increase power on a stock engine, but increasing the airflow capability of the engine will bring your blown engine to its full potential.

Setups

suppafatto

Toyota SC14 is every popular

Toyota SC14 blower
oval port lo-comp head 
watermeth injection 
hi energy ignition
manifolds to suit oval port
32/36 Weber DGV carburetor

photos

Blown A-series