The Technical Questions Thread

[clutch-monkey]

awesome!

[MilesR]

I like that engine animation site, Pimento. Thanks for that.

As for the pedal configurations, Magnum, as RacingManiac says, the standard was not set until the late 1920's, I think. The Ford model-T was in production until 1927, and it had a pedal configuration unlike anything we would recognise now. The throttle was hand-controlled. The left pedal selected neutral when half-pressed, first gear when completely pressed, and second (top) gear when released. The middle pedal selected reverse, and the right pedal operated the brake, mounted in the transmission. The hand-brake, when engaged, would also select neutral, allowing the car to be started by one person.

According to Top Gear, the first mass produced car to use the modern layout of gear-stick and clutch-brake-accelerator was the Austin 7, first built in 1922. Until this time, and for a few years afterwards, there was no standard for pedal layouts. I would guess that the right brake pedal may have been a concession to people who had learned to drive, or even race, in model-Ts, or other cars with other arrangements of pedals.

I can think of no serious downside to the right-brake arrangement. Heel-and-toe could be achieved pretty much as with the modern arrangement. There would be more foot-changing, under some circumstances. Up-shifts would require the right foot to be on the middle pedal, and the left on the clutch, while "left foot braking" would have the left foot on the middle pedal, and the right on the brake. This would make left foot braking almost impossible without driving with crossed legs, or lifting off the accelerator to change feet before you reach a braking point, which would slow you down. That is the only disadvantage that I can think of.

[pimento]

This guy made his own 9-cyl radial engine from mostly bike parts... then fired it up. It nearly worked!

[Kitdy]

Originally Posted by pimento

This guy made his own 9-cyl radial engine from mostly bike parts... then fired it up. It nearly worked!

Did he died?

[drakkie]

Originally Posted by pimento

This guy made his own 9-cyl radial engine from mostly bike parts... then fired it up. It nearly worked!

A little bit more thinking might have saved him a lot of money. Got to love these kind of projects though!

[karabiner98k]

Hello guys,
I have heard that the more you rev an engine, the faster it becomes!

Someone told me that if you change gears at higher RPMs most of time, you car will be faster in the long run and vice versa.
Is it true?
Please give me some technical reason for it (if it is true).

[Magnum9987]

Horsepower is a function of torque at a given RPM. The higher the rpm, the more power, generally. Thats why F1 cars rev to 17,000 rpm, and even higher if they were allowed to. They only make less than 300ft-lb. Diesels, by comparison, are much slower because while they have more torque, can only rev to 5,000 rpm. That torque can't be applied quickly enough.

[karabiner98k]

Originally Posted by Magnum9987

Horsepower is a function of torque at a given RPM. The higher the rpm, the more power, generally. Thats why F1 cars rev to 17,000 rpm, and even higher if they were allowed to. They only make less than 300ft-lb. Diesels, by comparison, are much slower because while they have more torque, can only rev to 5,000 rpm. That torque can't be applied quickly enough.

You are right but i meant something else.
Someone told me that if you always change gears at lower RPMs your car will be lazy in the long run.
Suppose we have two identical cars:
The first car was always driven with more revs.
The second was always driven slowly (it's driver change gear soon)

Now, if we test these two cars side by side at full throttle, which one will be faster?

[csl177]

Modern engine managment systems being what they are, the car that's spent it's service life being short shifted won't be any slower than the one that was constantly revved to the max. In fact, when your fictional test of identical vehicles takes place, the car that had been driven hard may well be slower due to increased internal wear.

EDIT: Why these myths are perpetuated for modern engines is another question.

[Matra et Alpine]

Created from days when fuelling and combustino wasn't as efficient or managed as todays cars.
So a car not revved and fuel/air/exhaust gasses moved quickly woudl tend to have poorer combusion creating more carbon in the chamber which would collect. Thus carbon build up woudl lead to reduced airflow, poor valve sealing and reduced spark.
Back then REDEX was added often to clear the soot out !!

[csl177]

^^^ That's why I referenced "modern engine management", Matra. Carbon buildup once was an issue depending on state of tune and driving use. It can still be a problem for some older cars, but aside from the occasional Italian tuneup and gasoline additives, modern fuels and oils in classics coupled with less average use have kind of limited the issue. Coking (carbon buildup on valves & combustion chambers) used to be taken care of by rotating the crank 'till the valves were open on a cylinder and blasting the chamber with crushed walnut shells. It's very effective, I've done it myself. But usually it's "L" and "T" head, side valve engines that are prone to coking.

I guess I should edit the last sentence above...

[Matra et Alpine]

yea I felt that for younger readers it woudl need the explanation of WHY the modern engine managemetn stuff did it's job better

NEVER heard of crushed walnut shells application

RAW Redex directly into the carb inlet was used on the rally engines regularly between rebuilds. Works great but neighbours usually end up calling fire brigade

[csl177]

Originally Posted by Matra et Alpine

NEVER heard of crushed walnut shells application

RAW Redex directly into the carb inlet was used on the rally engines regularly between rebuilds. Works great but neighbours usually end up calling fire brigade

Combustion chamber cleaning with walnut shells is left to the few oldtimers with the knowledge and tools to do it.

We've got a couple of things like Redex still, but I remember a Mr. Gasket or STP "cleaner" used that way. When I was a teen working at a garage, we'd open all the bay doors and the clouds were HUGE. What a hoot! Smelled great, too!

http://www.youtube.com/watch?v=_eKdGfEvUxM

http://www.youtube.com/watch?v=_eKdGfEvUxM

[Matra et Alpine]

WOrse modern one is teh "seafoam" the US guys use to clear the carbon from their rotaries ....

http://www.youtube.com/watch?v=2xa07pzIRFU

http://www.youtube.com/watch?v=2xa07pzIRFU

[NSXType-R]

Two part question-

1. Other than Jaguar, BMW, Toyota/Lexus and Nissan, what other companies have used straight 6 engines?

(Side note- it's a shame that only BMW uses straight 6s now, and even rarer than ever.)

2. Straight 8s- other than Deusenburg, what other car companies used straight 8s?