new car surprise gas saver

[Project84]

Originally Posted by BEEF

so what are the major contributing factors to turbo lag?

he has the smaller turbo which is supposed to spool up faster (and he wants to keep it that way) so I guess the size of the turbo matters but what else?

I have thought about a boosted car at some point and am kind of curious about this as well.

he also pointed out that it would be quite a job to relocate his intercooler since it is mounted right to the turbo and cutting would be required. I think that's right but I haven't looked at that aspect. it is right after the turbo and right before the intake so the entire distance is all of a foot at most.

http://en.wikipedia.org/wiki/Turbocharger

[Project84]

Originally Posted by theholycow

Sounds wasteful...energy goes into spinning it up, creating backpressure, and is then discarded out the wastegate.

In a naturally aspirated engine what do you call exhaust?

Waste.

So if you are able to use that waste to create an increase in horsepower, it's sorta like a win-win. To relate it to FE, think biodiesel or methane. Using something that is typically a byproduce to recreate a productive process.

[theholycow]

Originally Posted by Project84

In a naturally aspirated engine what do you call exhaust?

Waste.

So if you are able to use that waste to create an increase in horsepower, it's sorta like a win-win. To relate it to FE, think biodiesel or methane. Using something that is typically a byproduce to recreate a productive process.

Exhaust isn't as wasted as you think; and a turbocharger doesn't reclaim it as usable energy. Turbo takes the movement of the exhaust and uses it to shove more air and fuel into the engine (and as a side-effect it makes backpressure which consumes energy). Without a turbo, exhaust gas velocity's scavenging effect is an important part of making torque (which I can visualize but don't understand well enough to explain to someone else).

Anyway, my issue was not with the general idea of using a turbo; it was with spending energy on spinning up a turbo more than you're going to use it and then dumping that energy by spewing pressure out the wastegate.

[bowtieguy]

Originally Posted by Project84

In a naturally aspirated engine what do you call exhaust?

in a domestic V8 w/ a high flow/performance system it's called...music

[Philip1]

Na engines benefit from well tuned exhaust. A well tuned exhaust will use the mass of the sound wave to create a small vacuum at the port sucking in more air/fuel at cam crossover. a turbo engine works using a pressure differential across the turbo this is why high performance turbo cars have huge exhausts. the major issue with a turbo is they do create backpressure. This will cause a certain ammount reversion of exhaust into the cylinders. Most of the time a turbo pushes enough air to overcome the backpressure. at light load a turbo can be beneficial acting as a pumping loss reducer by pushing air in rather than relying on purely vacuum.


To answer the question about what makes this car a "race" car it was bought with a long history of autocrossing and HPDE's. I am currently using it as an autocross car and plan to take it to a few HPDE events. this car will end up with a roll cage and 5 point harnesses. This is every inch a real race car.

[severach]

Originally Posted by theholycow

and a turbocharger doesn't reclaim it as usable energy

The claim is that the turbocharger takes advantage of already expanding gas in the exhaust thus it doesn't waste power. Like you I think that's a bunch of malarkey and a turbo is an energy wasting tube fan for the power hungry. That said the Dodge turbo models got almost the same mileage as the non turbos.

Besides, if your engine has expanding gases beyond the exhaust valve then I say it needs a tune up.

[ma4t]

Because it's cool to know how stuff works.
http://auto.howstuffworks.com/turbo.htm

[dkjones96]

It isn't all free if that's what some of you are thinking. Yes, it is taking advantage of exhaust energy but it also places an additional load on the engine. Turbines create back pressure which is never a good thing for fuel economy or power but a turbocharged engine can shove enough through the intake to overcome it.

Your gains come from the increase in thermal efficiency. The more air and fuel you can cram into the same size cylinder the more heat is generated. Absorption through the cylinder walls and combustion chamber is relatively constant so you lose less of a percentage of that heat as a result.

[fowljesse]

That's cool that your race car gets good mileage, too!
I have a Mazda MX-3 that has about 200 wheel horsepower (short- stroke V6) that gets 34mpg, but I have done extensive modding, including an Engine management system. The car is also a daily driver, so it has a 10 speaker stereo, leather seats, etc... so it weighs about 2,500 lbs.