power, lost or found?
 

It seems to me there is a an area in the operation of a turbo motor that we don't know much about. Perhaps its only me that is in the dark, (run with that as you like), but I think it would be interesting to see what happens when a turbo motor is run to the redline with the boost gauge needle pointing at absolutely zero.

Have any of you comedians tried that? I think I will at the next opportunity.

There is no real performance value to find here, or so I suppose, but maybe an explanation of where some did//did not come from.

If one of you jokers has the opportunity try that in the near future, please offer up a report.

corky

You're referring to an N/A engine? I'm very confused by the purpose of your post.

So if I understand correctly the data you are interested in would be a dyno plot showing the motor running at 100kpa load all the way to redline?

Would you want instrumentation of shaft speed on the turbo?

Edit:

I'm confused as well as to what exactly you are trying to measure.

^^ I ass*umed that he was actually talking about a theoretical condition on a turbo engine, where the engine is running at redline, but it is not experiencing any boost. How you arrived at a such a condition in the first place would be interesting, but it would then, in a sense, seem like just a question about flow. Would we assume the waste gate be wide open, along with the BOV, to arrive at this unique condition? Are the wheels even on the ground? :dunno:


EDIT: Ok, I see he said "run to redline" . . . but I still don't get it.

Obviously with throttle modulation we can maintain 100kpa at redline and measure the torque being produced in that condition. I'm not seeing what Corky is getting at, though, how that information is useful. Information has to have a context to be useful. I'm not seeing the context. What could be changed to improve something? I'm not grokking whatever the something that could be improved is.

Corky, I'm not seeing what you're saying, know what I'm sayin? If I ask if you're talking about N/A, and you say "no", then I might think you mean the "know" in "know what I'm sayin", know what I'm sayin?

He's saying he wants to see a dynograph of someones car where target boost was zero for the whole rev range. No one has a wastegate large enough to do that, but we know from other dyno's that even when a turbo motor hasnt started building boost yet it will still be making more power than its N/A brother.

Just want to make sure I'm tracking here --

This is because even before building positive boost, the turbo engine isn't fighting a vacuum (or as much of a vacuum) like the N/A engine, right?

So let's prove that volumetric efficiency is increased by a turbo charger, even when we already know that volumetric efficiency is increased by a turbo charger.

You guys are thinking about this too much.

He's clearly sun-downing.

He does realize 18 is a mod now right?

:laugh:

I was going to respond, but just like the other thread he likely already forgot he made this thread, so this will be a 1 sided conversation.

I have done this before, though not exactly like the scenario he's discussing (the car still managed to make a teensy weensy amount of boost up top due to creep). Before it would make pressure, the car was still faster with the turbo at 100kpa because while not making pressure it is still flowing air and "helping" the engine breathe and overcoming the hotside restrictions.

Good day Mr. Bell

Ah yes...the moment I was waiting for.

Maybe I'm just optimistic, but maybe he wishes to compare N/A performance to find what's worth investing in? ebay log vs the tubular matched external gate or whatever. (More examples here)

Kinda a lot of variables to be comparing if I'm on the same page. My car wouldn't comply in current form for the same reason as Vlad.

Nah. A better flowing manifold is a better flowing manifold, period.

Corky please enlighten us as to the nature of your investigation. There is no butthole factor in my request.

Sounds like a motor with air assist?

Why not do 1psi with a teeny tiny trubo, Instant spool & consistent through red line? :dunno:

The question is are we talking wastegate wide open, or throttle holding the boost back?

You guys are over thinking this. Pull off the intake piping from the turbo to the throttle body. Boom, 100kpa at redline full throttle and a turbo. No need for BOV or wastegates.

But that kills off any "pre-boost" the turbo might be making, and eliminates any restrictions in the intake that might be masked by boost...

At least if I understand the question correctly. The suspense is killing me, can we get clarification now!!

This thread needs less talk and more kitten pics.

I made a roughly estimated 190 whp at 4 psi. Big turbo, big wastegate.

Here's a datalog dyno run. Take it with a grain of salt. Then mentally subtract 4psi worth of power.

I have overlayed a stock dyno graph for comparison. Same car, no has trubo.

https://www.miataturbo.net/attachmen...ine=1425479352

I had this happen when my Forge wastegate actuator rod unscrewed from the spring retainer at the track. The car was purely NA at that point. I thought my EFR spit out the turbine wheel "a la Soviet". I red-lined it on the way home and had zero boost the whole time.

This thread... :facepalm:

https://www.miataturbo.net/attachmen...ine=1425515506

dat EFR wastegate life :party:

The vol eff does change with the addition of something pushing it in. I'm not sure if it becomes meaningless as a measurement with turbo, but it seems to me the difference in power from atmo stock to atmo with turbo might offer a clue regarding, at least, what it was when stock.

I'm often challenged to explain why the power gain at a specific boost pressure is always greater than the pressure ratio. When suggesting it is in part due to taking Evol out of the equation, I sometimes get challenged that one can't do that.

Never taken the time to try proving it, but, wouldn't the two suggested measurements give us a hint?

Then, the question of how best to do the test. Part throttle offers an undue restriction, but an open wg slows the turbine. Easy enough to try both, I just haven't done it.

Useless info perhaps, except for number crunching enthusiasts.

corky

Just to be clear, would we need a 1.5" exhaust restrictor to keep manifold pressure at 0psi without creeping?

turbos convert enthalpy into mechanical energy to spin the compressor. part of it is pressure differential, part of it is heat differential. the net result of the entire turbocharged engine system is that you're increasing overall efficiency by slightly reducing the energy (temperature, pressure) leaving the tailpipe and using the recovered energy to push air into the engine. sure there are flow and friction losses within the turbine and its bearings, but (and I don't have a number handy) turbos are very efficient energy converters.

didn't some texan write a book on this?

Also couldn't you test your theory by using a car with a very large turbo that didn't have sufficient exhaust flow to make boost? Or running at lower RPM? Just pick a point where the boost threshold of the system is above your operating parameters.

for example at 2000 rpm on my old setup (VVT full retard, big-ish turbo):

https://www.miataturbo.net/attachmen...ine=1425651967

Would restricting the exhaust be a fair test? Doesn't seem like it.

The writer of that book pleaded ignorance on several subjects and then proceeded to prove it.

The big turbo might prove it, but work and cost...............

Wouldn't an open wastegate (and one big enough) be about the same as the bigger turbo? Or rather, the bigger turbine.

Come on Y8s, anyone who knows what enthalpy means ought to know everything about something as simple as Evol.

corky

I would think an open wastegate would kill turbine efficiency.

Volumetric efficiency is important here though. If you have more air going in than would otherwise be pulled in by the piston suck, then VE goes up. That's why we like turbos in the first place. The engine isn't a closed system though, so you'll also have to look at flow. Take a variable valve timing motor. It can change power output without changing pressure, can't it? Same with bigger valves. same with replacing the air with liquid oxygen. pressure can still be at or below 1.0 ATM and power output will change.

Power would be lost in such condition. If the motor makes 100hp at redline before turbo at 100kpa it would make less at 100kpa with the turbo since the turbo is blocking the exhaust yet the intake pressure remains the same.

Essentially it would be a leaf blower with an exhaust restrictor and we know that leaf blowers dont work.

If you're going to bring up the show that made the car with the 5 leaf blowers, dont forget they also tuned the car to get the 30 hp.

In my observation, power is not lost with both measurements at 100kpa.

That would agreeably defy reason until we know enough about it. Then "reason" might be more reasonable.

The numbers come out about right if the evol of the stock motor is ignored. Is that reasonable?

corky

Well why not compare power of 1.5" exhaust vs 2.5" exhaust?

have you ever compared dyno plots of a car with and without a turbo on the same motor? even before making positive pressure, there are power gains.

Actually yes, below boost pressure its a power loss.

https://www.miataturbo.net/attachmen...ine=1425965130

did you just image search for a random dyno plot that fit your hypothesis?

Must have. If you want to rebutt him, FM posted a 3071R dyno somewhere on mnet that shows the turbo car making more power at every single point on the dyno, even before spooling up. There might have been a discussion on that thread about the effect.

that's not even close a turbo vs non turbo comparison plot

lol

triple runs in wrong groove. triple stuck in groove. triple probably has supercharger driven by crank. triple trying to pull wool/eyeball deal.

corky

Yeah, well.... YOUR FACE!

Ah yes indeed this is a supercharger driven by the crank. Must be why the build quality is junk.

https://www.miataturbo.net/attachmen...ine=1426136319

I looked on FMs page specifically about dynos but none of them start from way way low rpms. They all start at +2.5-3k where the turbo is already making 1-2 psi.

The dyno i posted is of a LS1 before and after.

Turbos are superchargers..

Squares are rectangles, too.

But, the entire world calls them "squares," and we know which shape is being referred to when someone says "square."

ah go fly a rhombus.