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Ok, someone should make a test run

The merits of cubic inches vs bolt-ons for gaining performance. For or against?

By bolt-ons, I mean turbos, superchargers, nitrous, etc…

I’m fine with turbochargers for extra power when you need it, and good fuel economy compared to bigger 6- amd 8-cylinder engines.

No matter what you do, the speed limit is the limit.
That is, except on closed courses.

Now, modifications that improve efficiency for a given load are very useful, but there aren’t many that pay off in a short time.

Real easy. ‘There is no substitute for Cubic Inches!’ Even tho it may not be as fuel efficient, for consistent, reliable power, there is none better than a bigger engine. Turbos and superchargers will boost power, but will require more maintenance and shorten the engine’s life, exponential to the boost level applied. Nitrous really cooks engine parts.

The best story I ever heard on this subject was the legend of the Ford GT40. Ford wanted to get into european racing, and chose the 24 Hours of Lemans. With this race in mind, they started design on the GT40. They decided to use a 427 big block V8, with a slightly altered cam profile and a four barrel carb on an aluminum intake. Besides the tubular headers, the rest of the long block was factory spec. The reason was because of it’s proven reliability and durability and consistent power. The result was racing history. The GT40 won Lemans 4 years in a row, from 1966 to 1969, not by being necessarily the fastest car in the race, but by needing less and shorter pit stops for repairs, tires, and fuel.

Before cars were built with the performance we get now, it was one way, the other, or both. You still want the enging to stay running. You can get more performance by bolt-ons but these small engines are already stretched out about as far as they can go. So, if you want a street legal car, you can just but the fastest one you can get. As always, what you can do is based on what car you plan to get. After that, you decide what kind of parts or engines you like the best. In the old days, cubic inches were cheaper. A Catalina with a 455 beats a 5.0 Mustang in a drag race. It’s been done, and it’s history.

I don’t have any idea. I do know those really fast cars on TV that look like space cars don’t have a much bigger engine displacement than my Toyota Sienna, but they can run 200 mph. So, it would seem you can really add a lot of power to a small engine.

In any case, I am helping test this new layout. Sorry about the dumb answer.

I was told when I tried to post my previous comment that it would be held until approved by a moderator. I thought the rules said stuff would be posted immediately, and if flagged by other readers would be hidden until read by a modertor. What gives?

Also, each time I reply, I am required to agree to terms of service. Is this logical?

My opinion is this: If you want a faster car, buy a faster car. This is probably much less expensive in the long run than modifying a car to gain performance.

But modifying a car is so much more fun.
I bought the Rivvy for $500.
I’ve put over $1000 into it.
I probably could have bought a 96’ Civic with working A/C, stick, no major problems, and at least 50K more trouble free miles on it here in Florida for that and not had to spend time working on a car.
But the fact of the matter is that it’s fun! :slight_smile:
(Yeah that’s not modifying but the analogy works anyway)


PS: This new method of replying is absolutely kick@$$!

I’d like to add that the engines used in Chevy’s and Ford’s in NASCAR use the same small block V8 configuration that can be found in production cars. But, they build them with much higher compression, bigger valves, larger cam, etc., and are developing over 700 horsepower, compared to the 250+ of the factory version. The cost is reliability. Those engines will not last much past 500 miles, and some don’t survive the race.

Bolt-on performance is very risky when you begin to pump more air into an engine that is not designed for it from the bottom up.

Turbochargers are used in many production cars today with good results, short term. But turbochargers have problems. They are, in effect, little turbines that are mounted in the exhaust flow. As the engine increases RPM, the turbine wheel spins faster. Connected by a shaft to the intake side where there is another turbine wheel, the spinning exhaust turbine pressurizes incoming air on the other side, thus increasing the amount of oxygen and allowing more fuel to be burned, hence more power. But since the exhaust turbine and shaft are in the red-hot exhaust tube, there is a tendency for bearing failure. Some engineers have created water cooled housings to try and reduce the amount of heat build up, but ultimately a turbocharger will cook the bearing and have to be replaced. All turbochargers do have an oil feed dripping on the bearing, and this can cause the oil to break down more quickly as well, so frequent oil changes are mandatory. Yet another problem is cool-down time. If you come flying in off the interstate and shut down for a re-fuel, that oil flow is interrupted and the oil cooks on the shaft bearing. Ideally, a turbocharged engine should be allowed to cool down at idle for a minute or two until the exhaust drops to reasonable temperatures.

Superchargers are a bit less efficient but arguably better on passenger cars. They do the same thing – compressing incoming air for the intake, but they do so by a belt driven compressor spun by the engine, so they are a bit parasitic.

The problem with turbo or super charging is that it raises compression pressures in the engine, and an engine not designed for the pressure will fail prematurely. My '01 Pontiac GTP has a compression ratio of 7:1 (if I recall) which is much lower than the normal 9:1. The supercharger is monitored by the computer via a waste gate. If additional engine load is sensed, the waste gate closes allowing additional intake pressure to be built up and more power is delivered when the computer allows additional fuel. But it is all engineered that way from the beginning. I just turned 150,000 miles on that 3.8L V6, by the way. Nothing done except plugs in the engine.

That is an excellent tutorial, Anon. If one is just after horse power, and doesn’t care how it’s gotten, and is willing to replace a blown (disintegrated) engine, or three, one would get the biggest engine one could afford, put a supercharger on it, and run it until it blows. Now, THAT’S simple horse power!

Forced induction technology has gotten a lot more advanced recently. Superchargers versus turbos for smaller displacement engines is much closer than it was in recent years, when supers were great for low end and turbos were great for max top end. That being said, it’s true, there’s no replacement for displacement, but even that gap is closing.

Just to clarify, FI doesn’t raise the compression ratio, but does increase the pressure within the combustion chamber.

You can put bolt ons on just about any engine, as long as you’re reasonable. Some engines will only tolerate single digit pressures above ambient without exploding, and some that are factory turbos to begin with can take pressures almost three times ambient. Stay within reasonable limits, and have good standalone engine management, and you can safely FI for hundreds of thousands of miles, with proper maintenance.

For example, let’s take the dog of an engine that is a 318 Chrysler small-block, 2-barrel carb, emissions equipment and all still intact, with headers and a performance ignition. What does that put out? About 178hp. Step up to a hotter cam, 4-barrel carb, aluminum intake, and proper timing, and the motor will put out another 100hp on top of that. Check Mopar Muscle Magazine to see what I mean.

Imagine if you put nitrous or a supercharger in addition to all that?

What kind of performance do you want? If you are talking about drag racing you can’t beat nitrous for bang for the buck. If you want everyday performance a turbo setup is hard to beat. All it takes is money and starting with a good base. If your engine and drivetrain are “tired” get them built to handle the increased power.

In other words, “There’s no replacement for displacement.” :slight_smile:

The questions before the court - - bolt on? yeah / neah ?
The neah has-is-it! The equation is out of balance. Here it is - - in one hand, a gallon of gas-so-lean (100% energy). In the other hand, one piston recipricating engine (for work). Add the two together and you’d think-es-sis that you have 100% work. eeerrrnnnttt ! Way to much-es-es wastes-es-es in the form of heat. This is why I am the only citizen in the United States of Am-er-Asia that is the most wasteful - - tah-dah !!

I’ve never done any real homework on this topic, but turbos are expensive.

(resurrecting the first car advice thread I could find. Just to ruffle some feathers…)
(ps: The reply area tells me that this post is gonga old, and asks if I am sure that I want to continue this old conversation, so many folks replying to really old threads and restarting them know exactly what they are doing- much like I do.)


Anybody considering “bolt-ons” should read the December issue of Hot Rod magazine. They “tested” the viability of a bolt-on turbocharger and found a lot of surprises. They pulled a 350ci small block Chevy V8, got it in good shape and ran a baseline run on a dyno, ordered a turbo “kit” from Amazon, and went forth to install it… in an expert’s lab with his dyno setup and equipment. The turbo itself worked flawlessly, but there were numerous problems even without the engine constrained by a car body (it was on a test stand). The biggest was runaway boost… they had to abort the test when it zoomed to 17psi for fear of the engine exploding. They had to do welding, heating and reshaping one of the exhaust manifolds, modifying the blow off valve fixturing, and ultimately adding another, larger, wastegate.

Their conclusion is that yes, it made power, but required a seasoned veteran with basic fabrication, welding, and problem solving skills… and would be extremely dangerous installed by the average joe. I recommend reading it. It’s an eye-opener.

Here’s some feathers


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