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Looking forward to seeing the numbers you guys come up with
Originally Posted by U-928
...........aanndd.......................
no numbers? cmon.
Patience. It's not being run under boost yet, so there are no meaningful power or torque numbers that we could show. This is a break-in dyno session, and the main numbers we're looking for now are blowby numbers so we can get that sensor calibrated for the appropriate range.
This may sound weird to many of you, but there are literally ten things that I'm more interested in learning than how much power it will make. I'm mostly just looking to learn things and verify my understanding of what happens inside that motor. I want to know how much blowby it makes with these rings, and how long the engine needs to be broken in for the blowby to stabilize. I want to know what's the cycle average boost to back pressure ratio. I want to know at what rpm will cylinder #1 start knocking with these new exhaust manifolds because of the 90-degree exhaust blowdown interference. I want to know if the valve springs set with the low seated loads can really handle boost. I want to know if the larger overlap cams help or hurt cylinder evacuation. Etc.
Patience. It's not being run under boost yet, so there are no meaningful power or torque numbers that we could show. This is a break-in dyno session, and the main numbers we're looking for now are blowby numbers so we can get that sensor calibrated for the appropriate range.
This may sound weird to many of you, but there are literally ten things that I'm more interested in learning than how much power it will make. I'm mostly just looking to learn things and verify my understanding of what happens inside that motor. I want to know how much blowby it makes with these rings, and how long the engine needs to be broken in for the blowby to stabilize. I want to know what's the cycle average boost to back pressure ratio. I want to know at what rpm will cylinder #1 start knocking with these new exhaust manifolds because of the 90-degree exhaust blowdown interference. I want to know if the valve springs set with the low seated loads can really handle boost. I want to know if the larger overlap cams help or hurt cylinder evacuation. Etc.
YOU ARE A BOOST TEASE MAN!
Watching this thread has alot of us on the edge of our seats!
YOU ARE A BOOST TEASE MAN!
Watching this thread has alot of us on the edge of our seats!
I'm sorry to drip out info little by little, but I can assure you that I'm not sitting on any dyno graphs that show boosted runs. Scouts honor, when this blue engine sees boost then this forum is the first to know.
Originally Posted by Lizard928
Larger overlap cams always helps boost (turbo as well). Obviously there is a limit, but there is more than enough data to show it helps.
"More is never enough and too much is just right"? I think there's a limit.
Originally Posted by Lizard928
If your exhaust back pressure is too high are you going to increase the A/R?
Well, it depends on why the back pressure is too high, and on what is too high. To me, too high is measured specifically during the overlap and relative to the intake port pressure.
If the back pressure is too high because the turboback exhaust is too restrictive and turbine outlet pressure is high, I'll proceed to tear out my hair, increase the exhaust pipe size, and redouble the efforts to muffle the exhaust. Next stop: dual 3.5" or single 5" -- aaarrghh!
If it's too high because there's a big pressure loss from the plenum box to the intake port, then I may need to move to a short-runner intake, although I don't believe that's the case / necessary. I'd first try more extensive porting of the throttle body element and up pipes in addition to a larger throttle plate to slow down the air.
If it's too high at cylinder #1 because of exhaust blowdown interference during the overlap, then I don't know what I'll do. I think larger turbine housings don't fit in the space, so that's out of the question. This housing has three A/R options, .63, .82, and 1.03, with .82 currently in the car. I'm not even sure that the 1.03 A/R housing fits there, but it may. There's zero square millimeters of space under the hood for any bigger pipes of any kind, anywhere. I guess the next thing then would be to have cylinder-specific lobe centerlines on the cam?
UPDATE: John solved it! This key fob is going to totally take care of any back pressure problems. Unless if there's kryptonite in the pump gas motor's exhaust, is there? No kryptonite, right?
If you've got turbos that spool by 2400 rpm such that wastegate needs to be opened, you're better off taking off the flappy and welding the shaft holes shut. But I don't think I'm there with these turbos and this compression ratio..,
As a test, John run the car at 5000 rpm with 7 psi boost. It made about 420 ft lbs at the axle and thus an estimated 450 ft lbs at the flywheel (close enough for government work). The stock engine makes about 295 ft lbs at 5000 rpm, and we have lower compression but bigger cams. Scaling up 295 ft lbs by (14.7+7)/14.7 = 435 ft lbs so we're doing somewhat better with the blue engine than the theoretical benchmark of linearly scaling up a stock engine. This is with very conservative timing that prevents any chance of knock, so in terms of power and torque production we're exactly where we planned to be.
Now to the important stuff. At 5000 rpm, 7 psi boost, and 450 estimated flywheel ft lbs, the blow-by meter doesn't go over 2 CFM. This gives us a blow-by coefficient of 2 CFM / 450 ft lbs = 0.0044 CFM/ft lbs, which is as good as or better than a new modern engine would produce. (http://performancetrends.com/Blowby_...nsor_Meter.htm .) I'd consider the ring seal excellent, which is very good news. The person who built this engine knew what he was doing.
Based on how it appears visually, the blow-by gas coming out of the blue engine is mostly water vapor and some other exhaust-like gasses. The engine doesn't eject any oil whatsoever thru the new breather system design, at least not at 5000 rpm and when it's timed not to knock. This is also very good news. Later, we'll push our luck with more boost and rpm, and finally we'll induce high-load knock to test the breather system under an adverse, worst-case scenario.
When on boost, the car is considerably LOUDER than with the previous twin-turbo system and stock engine. This is as expected. The blue engine has lower expansion ratio, earlier EVO, and more valve overlap. The twin-turbo system has a massive filter and huge thin-wall stainless compressor inlet pipes. Hell yeah it's going to be loud when on boost and WOT, and that's A-OK with me! (Just need to keep it quiet under 2500 rpms and at part throttle.)
Next up is going to 6500 rpm with this boost level, and then gradually to higher boost levels.
In terms of next measurements, I really want to measure the turbocharger blow-by independently. The quantities are lower than with total crankcase blow-by, so let's use liters per minute units. A very simple model of turbo blow-by is that the blow by from the center housing assembly is proportional to the square root of [(turbine inlet pressure + turbine outlet pressure)/2 - crankcase pressure]. Since our turbine outlet and crankcase are close to atmospheric, this simplifies to turbo blow-by being proportional to the square root of the turbine inlet gauge pressure. The goal in the next set of measurements is to estimate that constant of proportionality and assess the accuracy of such a super simple blow-by model.
Why do I care about turbo blow-by quantity? It relates to the crankcase breather design.
At high load, the compressor and turbine are both under pressure and thus the turbocharger oil drain contains a significant quantity of blow-by gas flow, in addition to the estimated 1.4 l/min of pure oil per turbocharger. The pump evacuates 3.8 l/min per side. In terms of the crankcase breather system design, if the blow-by gas flow rate from the turbocharger exceeds 2.4 l/min, the external air-oil separator in this design will flow some blow-by gas up the -8AN line into the separator bottom. This will slow down the oil drain from the separator.
Given that the oil drain line is -8AN and thus has 11.2mm inside diameter, at approximately 5.4 l/min flow rate the gas velocity in the drain line exceeds 1 m/s. At that flow rate, by my guess the gravity drain of the oil is likely to slow down or even stop. Therefore, if the turbocharger blow-by gas flow rate exceeds 7.8 l/min (of which 2.4 l/min is evacuated by the pump and 5.4 l/min evacuated via the separator drain line) the oil begins to temporarily accumulate in the external separator until the blow-by flow rate is reduced below the threshold. This is fine, because the peak blow-by episodes from the turbo are very short lived.
My current best guess of the expected high-load (1 bar boost, 1.5 bar turbine inlet pressure) turbo blow-by gas flow rate is approximately 5.5 l/min -- but that's just a pure guess based on some academic research. Soon we'll actually know!
The car is being run up to 5500 rpm and 8.5 psi boost now.
This here isn't a serious warning, just a note that a test has finished. Phew... Nobody wants to break a dyno.
Superman key fob in action:
Here are some numbers. Making 477 axle hp or 455 axle (transmission scaled) ft lbs at 5500 rpm and 8.5 psi of boost. Again, this was run with ignition timing that doesn't knock with almost a full point higher compression, so it's ultra safe.
Boost normalized, this is about 302 axle hp at 5500 rpm, which I consider a strong number, considering the very conservative ignition timing. The blue engine not only seals well, but also breathes well.
The observations track the simulation pretty well. The simulation makes a little more power because it uses a little more spark timing.
In particular, what may be of interest in the simulaitons is the exhaust back pressure at 8.5psi (0.6 bar) and 5500 rpm:
The back pressure in the wastegate pipe fluctuates widely so there's no such thing as just one back pressure. Then we'll have a Mach index of about 0.31, which adds another 7% or so of dynamic pressure on the wastegate poppet valve.
One of the next things is to correlate the measured static exhaust manifold pressures with the simulated ones.
The existing exhaust design that I call Silent Night is attracting some police attention in Kentucky and neighboring states. Even when the car is outside the radar range, the police can still estimate the location, direction, and ball-park engine speed from the exhaust sound. Google and the Russians are automatically tracking the location of the car based on the exhaust noise.
Wow, remind me to never visit your neck of the woods. Driving around in my 79 with open headers for the past 13 years I get thumbs up from the police.
Originally Posted by ptuomov
Nobody wants to break a dyno.
We have a similar issue here. Our local shop where Turbo Todd tunes his car needs to upgrade due to a Supra they built recently reached 1500rwhp:
01-23-2017, 10:26 AM
