Catalytic converters and horsepower

No it doesn't produce power. It's more like it releases power.

Think of it like this. Have you ever ridden a bicycle into the wind? You can't go very fast can you? You have the ability to go faster but the pressure of the wind against you slows you down. Well it's sort of the same deal with an engine.

The cells inside the catalytic converter act as a sort of plug. When the piston is pushing the exhaust out, the insides of the cat slow the air down. This is know as back pressure. So the engine has to use more power to push the exhaust out of the engine. Like when you are peddling hard on the bicycle against the wind, but no going anywhere. You exserting alot of force but getting much out of it. Now when the wind stop blowing, they you start going faster because you aren't fighting the wind. You didn't get any stronger, you just didn't have to find the wind. Well the same thing happens when you release the back pressure in the engine. It allows the piston to push the exhaust out easier, thus releasing the power of the engine. So that is why high flow cats "make" more power. The engine can use more of its power to move the car instewad of fight the back pressure.

See above.

With the decrease in back pressure the exhaust noise will get a little bit louder. Again I'll use wind as an example. The hard/faster the wind blows the louder is gets. So the harder/faster exhaust comes out of the engine the louder it gets.

Yes.

The reason is because the catalytic convert is used to burn up the excess exhaust that wasn't fully combusted in the cylinder. So if you have no cat to burn off the unburn fuel, you will will smell the unburn gas still present in the exhaust.

 

I also heard that it's not good to have no backpressure at all... can you verify that Ernie? Why is it bad to have no backpressure at all?

 

In simple terms your engine gulps down fresh air, adds gas, burns the mixture, and then pumps out exhaust fumes.

Getting the gasoline to mix with the air has gone from a black art to a very complicated science. Part of the equation is to have both the inlet and exhaust valves open for a small amount of time because this promotes ‘swirl’ which causes the gasoline to really mix with the air. Remove the back pressure by altering the exhaust system and you could reduce the amount of power you car will put out at some RPM ranges. Why? Because your air/fuel mixture is now pouring down the exhaust pipe instead of being kept in the cylinder.

This is another reason why cars without their cats smell of gas.

I would recommend you leave the cats in, but that recommendation has, I must confess, a social bias to it.

 

It really depends on the cam timing.

As Mark said, some engines have both valves open for a brief amount of time. This is know as valve over lap. It is control by the cam timing. The whole Idea is to try and get the fuel and air mixxed just right. The better the mix, the bigger the bang, the more power it can make. So one way to get a better mix is to use the exhaust stroke of the engine to help pull in that little extra air from the intake before the exhaust valve closes. As the exhaust is leaving the cylinder it creates a sort of syphon effect.

Have you ever had a fish tank? Well one of the ways to empty the water is to use a syphon. You would have the bottom of the tube lower than the top of the tube in the water, so that gravity can be used to create a syphon. Then you suck up the water so that is starts to come out of the tube. As it starts coming out you stop sucking. If you have done it right, the gravity of the water coming out of the tube will continue to draw water into the tube. The valve over lap sort of does the same thing.

Now, if the car has had the valve over lap tuned with a restrictive exhaust set up, it was done accounting for the back pressure. So lets say that with the back pressure the exhuast stroke would pull in an extra 1 part of air, using the valve over lap. That extra 1 part would give the mix the right amount of air/fuel ratio for the car to make the most power with a restrictive exhaust set up. So if you get rid of the back pressure, the exhaust coming out faster may change that to 2.15 extra parts. This could suck in more air, but, it can also suck out some of the fuel that was being drawn into the cylinder, throwing off the fuel ratio. By not having the proper mix the engine won't make the most power it could.

However, with todays modern injected cars, O2 sensors, Mass Air Flow Sensors, and variable valve timing, the computer usually will adjust to the extra exhaust flow, thus "creating" more power with the less restrictive air flow.

 

Love your analogies Ernie!

As far as the aftermarket catalytic converters actually increasing horsepower, yes! I'm not familiar with the gains on the Testarosta but I've spoken with customers who have them on 360's or 355's and absolutely love the increase and sound.

 

I have a TR and have driven and tuned them since 85. I have driven them back to back with and without cats. Cats alone make very little difference and I suspect you would need a dyno to tell. What does make a difference is the tuning changes that having no cats allow you to make. The cam timing was changed on the US cars and for one reason. The same reason that other manufacturers do it as well. With greater overlap due to the exhaust gasses being sent down stream earlier, at low RPM it will take some unburned fuel with it. That is as a result of the scavanging effect of the cam timing. The cam timing is changed only to reduce those emmissions. In the case of the TR (and many other cars I expect) It is also to prevent the cats exposure to that unburned fuel that will cause a cat overheat. Without cats you are given the freedom to manipulate cam timing.

You can also change the ignition timing because all Microplex boxes have all timing maps for every market programmed in them and all you have to do is to instruct it to select the base map. At that point the only tuning difference between a US and a base model TR is the compression ratio and changing that is a little more invasive.

 

The cheapest, easiest, reversible HP increase can be obtained by purchasing a new computer chip for your car. A $500 computer chip can give you up to 20HP, they take less than an hour to install, and are legal. The FCA newsletter has a company that advertises ECU chips in it every month, www.tap1.com

 

On a TR? Guess again.

 

www.tap1.com/catalog/product_info.php?cPath=97_99_124&products_id=167

 

Thanks Kevin.

Sometimes people have a hard time understand what is said. So I try to make it easier to understand by relating it to something more common. So that they say "Ooooooohhh I get iiitt."

 

TR 85-91

TR 512 92- up

Different cars, or did you not read the first post?

 

Did you read the link?

"FERRARI 512 & TR TPS Chip Upgrade +24hp increase."

It says 512 and Testarossa, so I think it will work. I tried to call them but no one answers their phone.

 

I certainly hope it will work on my 88.

 

The engine management systems are different between the two. If they say they can increase the power by a chip change on the TR by the same amount as a TR512 it's BS.

And no I did not bother to read the link. Lewis Carrol and The Brothers Grimm are both far more down to earth.

 

Very good explanation Ernie, a small addition to the main question if I may. Reducing back pressure and causing the charge to be pulled through and out of the chamber reduces torque, like installing a cam with a longer duration but it increases HP in the upper RPM range because of the scavenging effect from either a larger cam or less restrictive exhaust. So, people feel less power in the seat of their pants, happens all the time with these ricers and mustangs with no converters and trashcan mufflers.

 

For a Ferrari 308? Just joking, we have no chip

 

Funny I do not hear you denying the ability to change computer chips in a TR anymore. Perhaps they use different chips, with different programs, we do not have enough information to say how they came to their statemetns or what they have in supporting documentation. "Down to earth" is subjective, and since I know nothing of any three of the entities personalities, I can not comment.

 

Never did. I just call B.S. on the claim.

 

I did finally go to the link and it lists 512TR. It does not list TR.

Those are 2 decidedly different cars. As I tried to point out before but you did not listen.

I have many times entered into a thread without being as thorough reading all the posts as I should have and consequently stepped in it but I try "A" to hold it down to one misinformed post and "B" to only comment on topics that I have some knowledge in.

You have done neither.

 

Brian will correct me if I'm mistaken, BUT early TRs, such as the 87 that the original poster owns, use CIS injection as do 308s, 328s, 911s and a bunch of other european cars. Easy, durable, and reliable system, but not easy to modify for performance gains. I know of NO pre-motronic CIS systems that can be modified with a simple plug and play chip. I'm sure they're popular with the WRX tuner crowd, but don't apply to F-cars from the 80s.

That said, GTOfan, others have flamed you on hear and I have restrained, but I value the info and expertise that guys like Brian bring to the board. It is invaluable to me. It chaps my ass when people with virtually no working knowledge of these cars has the balls to argue with him and others like him. Pick your battles and do some research before you go blasting away.

Hi-jack over,
John
P.S. Ernie, good explanations in leymans terms.

 

You highlighted my quote, their webage says "and testarossa". So the question is, do they mean the 512TR only, or do they mean both the 512TR and regular TR? The word "and" is the issue and until someone at Tap actually answers the phone, I can not determine if a pre-512 chip is available. If the chip was only for the 512TR why say FERRARI 512 & TR TPS Chip Upgrade +24hp increase.", instead of FERRARI 512TR TPS Chip Upgrade +24hp increase? Is it a matter of sloppy editing or does such a chip exist? I'll try to find out tommorow.

 

I look forward to your query results.

 

Ernie,
I love analogy for explanations simply because it WORKS.
And you have used it effectively.
Thank You.
Keith

 

I went to the trouble of exploring the website and all the products for Ferrari.

They have no product for the car we are talking about.

Unlike you I have a great deal of experience with the car in question and the only computer is for the ignition timing. To "Chip it" is futile.

Rather than argue a subject you have no knowledge of why don't you just read and learn?