educate me

[4g63mightymax]

I want to know why a turbocharger needs engine load to work. Without an engine load, there is no boost, why? Isn't it the same amount of air volume and pressure coming out the cylinders at 7000 RPM whether you are in neutral or in 5th? Maybe it is a very easy answer and I just missed it along the way. If anybody can provide some insight on this it would be greatly appreciated. Thank you for the education!

 

[GRNDSM]

>I want to know why a turbocharger needs engine load to work.

It doesn’t… But in order to sustain a load, your need a turbocharger (boost).

>Without an engine load, there is no boost, why?

Because your engine revs too high/too fast, way before there is enough air flow to build boost.

>Isn't it the same amount of air volume and pressure coming out the cylinders at 7000 RPM
>whether you are in neutral or in 5th?

No, as you pointed out, you can’t have boost in neutral… so pressure is not the same.

Actually, if you let your car bounce off the stock rev limiter, it will build boost . But you are approaching this question from the wrong direction. It isn’t load that causes boost, it is the boost that allows you to overcome or sustain the load.

Lets take an NT car, can you go WOT and expect it to stay at 3000rpms? Not, unless you have a stutter box or some other 2 stage rev-limiter. In a turbo car, you build the boost by opening the throttle and letting exhaust gases drive the turbine. So, if you go WOT, RPMs will raise much quicker than boost so you will never see it, but technically it is there, it is just “lagging” behind the motor .

If you give it only a partial throttle (like ~10% open), just enough to keep it at, lets say 5000 rpms, you will not have enough airflow to build the boost. And if you were to begin to build boost, you will not be able to keep 5000rpms, as your engine speed would rise. If you lower your throttle down to ~5%, you are back to a point where you can not build boost.

This goes on and on until you figure out a way if keeping RPMs at 5000rpms (like with a stutter box or torque converter on an automatic car). Then you can build boost.

I hope I made this clear enough

 

[4g63mightymax]

Thank you very very much. I had to read it about 11 or 12 times to really get the full meaning of it all, but never-the-less, I got it!. You would not believe how difficult it is to find that information.

On a lighter note, I saw your car at the world of wheels for sale. Now does this mean you have something else in works? The Tr7 maybe? Here is another long shot, but do you still have the D50? or is that long gone?

Thanks again!
Jeremy

 

[GRNDSM]

Sorry if I wasn't perfectly clear. Information like this is difficult to explain .

Green Machine didn't sell. So it is back in storage. I am just going to pull it out in the spring and I will deal with running 9's after I actually make into the 9's. Bit I am planning on getting back to the TR7 this winter.

D50 is long gone! Sorry.

 

[Defiant]

I want to know why a turbocharger needs engine load to work. Without an engine load, there is no boost, why?

Because, you ninny, "boost" is just a measure of manifold pressure. When it goes into negative pressure, we grease monkeys call it "vacuum". So, "boost" means "more air coming in than the pistons can get away from". Which is why boost is so hard (and, hard on the engine) to bring up in first gear. The motor will spin up too quickly under light load for the turbo to be able to make "boost". However, the motor will spin up quickly enough to outrun the oil pump's ability to provide fresh, cool oil to the balance shaft or rod bearings, and shazam, bearing knock starts. Not to be confused with the sounds the knock sensor is listening for.
Same stuff goes on cruising down the road at 80 with no load- the turbo's boost is being run into the cylinders just as fast as they can use it, and you'll see very little or no boost on a gauge- on normally-aspirated engines, the same happy settings will show high vacuum, and in both circumstances, highest engine efficiency. If you want to see the boost come up, start up a hill. Or, change engine load by opening up the throttle plate and similarly asking for more power. Close the throttle, and the vacuum will come up.
Although there's lots of fussy little parts, and the tolerances are in the thousandths of inches, not much is more simple than how internal combustion engines work.

Well, okay, there's turbines, but they're even more fussy about being built.

Oh, and sorry about the "ninny".



not.

 

[4g63mightymax]

Ok, I got it now. Thank you both for the info, I feel smarter today than I did yesterday.
Leon - I guess I would settle for 9's if I were you . Im shocked that nobody at world of wheels saw what a great value your car is for the money. Where else can you buy a car that fast for that amount of money? Anywho, I'm sure I will see you at New England Dragway this spring. If I dont see 9's by the end of the summer, I will be very disappointed.
Jeremy (aka-ninny)