1990 Toyota Corolla Back Pressure

JACKOLSON

MEMBER
1990 TOYOTA COROLLA
4 CYL
FWD
MANUAL
80,000 MILES

Why is back pressure being said to be important to have in a naturally aspirated engine? And why is it important to have none in a boosted one?

Isn't it right that if the exhaust gases goes out of the engine faster, then it will decrease wasted power, and improve performance of the engine?

Then what is back pressure for?

Thanks.

5 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

It is a complicated issue but remember factory engines are not designed to produce maximum power, they are designed to provide a wide range of power and torque in all driving conditions.

Also remember that one specific goal of manufacturers is to maximize fuel economy and most improtantly emmissions, as mandated by federal law.

A good example of where MAXIMUM power is the goal over any other concern is Pro Stock drag racing.
A 500 cubic inch engine producing over 1400hp.

Another example is the turbo era of Formula 1.

Honda had a 1.5 liter V6 turbocharged engine that produced over 1,000hp in a car that weighed 1600lbs.
This engine would be undrivable on the street, since its powerband was in the 6,000 to 12,000 rpm range.

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Monday, August 31st, 2009 AT 8:56 AM

JACKOLSON

MEMBER
67 POSTS

I do understand the dynamics of what you explained, thanks, but I have another concern, please.

What's the minimum diameter of header pipe and exhaust pipe can I use for a toyota 4af carb engine 1.6L 16valve 4cl engine?

From what you explained I guess that:

1. If I remove the CAT and Muffler, it will diminish the torque at the low rev range? Right?

2. If I use 4 separate pipes from the Exhaust Manifold going out as 4 separate exhaust pipes into one resonator pipe at the end, no muffler, no cat, would that be different in using a 4-1 aftermarket header going to a resonator, no muffler?

Emissions policy in my country is a joke, so I'm not after emissions and I'm not after fuel economy either. I just want to know HOW to make the most performance out of my old engine, that's all. I want torque to be readily available in the low rev range and max power at the high rev range. And I don't want any mufflers or catalytic converters, I want the engine to sound as it is.

Hope you understand.

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Thursday, November 5th, 2009 AT 1:45 AM

MMPRINCE4000

MECHANIC
8,548 POSTS

Sure I understand, here is the U.S. Emmissions is becoming the main issue.

The only way to get more HP is to get more air into engine. There are several ways to do this.

Turbo
Supercharger
Nitrous Oxide
Higher flowing head with larger valves
Camshaft change with higher lift and duration
Larger throttle body diameter
Larger pistons/longer stroke

Headers and cold air intakes will make a small difference, nut the key as mentioned above is more air. More air allows you to burn more fuel, more fuel = higner HP.

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Thursday, November 5th, 2009 AT 5:43 AM

JACKOLSON

MEMBER
67 POSTS

Thanks man.

Well, I guess I have to go back to one of my options and that is to get the Toyota "Black Top" 4AGE but not the supercharge or turbocharge one, I don't really like turbos and superchargers. Then I'll mod the camshaft of the Black Top, just the camshaft.

More power.

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Friday, November 6th, 2009 AT 9:03 AM

MMPRINCE4000

MECHANIC
8,548 POSTS

The 4AGE is a good choice, 30 more HP than the 4AFE.

You would also have to use the ECM and most likely the harness also.

Honda (unlike Toyota) has allowed the aftermarket to produce blocks, heads, and many other components.

Toyota has a division called TRD (Toyota Racing Development) that does have high peformance parts for many engines, although I am not sure about the 4ALC, 4AFE and 4AGE engines.