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!