IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: Scoobum on April 06 2015, 10:39:40 PM
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For those that are too lazy to look it up. :)
Want your engine to spool/rev up quicker...then here ya' go:
RJC billet aluminum pulleys...and if you can only afford one...get the crank pulley.
9.5" torque convertor...th ink of the weight savings over the stock 12" D5
Balanced rotating assembly
Aluminum driveshaft
Aluminum rear drums
Billet rims...the ones on my car weigh 9 lbs each...compare d to the GN steel rims weighing 28
Erics TT chip...allows you to pull low gear/spoolup fuel and add low gear timing and aggressive mode with his alky chip.
Removing 1 pound of rotating mass is the equivalent of removing 7 pounds of static weight.
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Removing 1 pound of rotating mass is the equivalent of removing 7 pounds of static weight.
I cringe every time I see overly simplistic (and wrong) statements like that.
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I did say it was useless info. :)
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Hey, cool guy wheels are needed. Just look at those giant rims on them donk and slab cars. Surely they help the car go faster.
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Removing 1 pound of rotating mass is the equivalent of removing 7 pounds of static weight.
Maybe it's the dork in me but I sure would like to see exactly how this statement came to fruition... and the formula used to derive this answer
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It was in a magazine once and spiraled out of control. Or maybe not.
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The dork took over and found this on a BMW site:
Conventional wisdom says that conservatively, 1lb worth of rotating mass lost is roughly equivalent to a 4lb sprung mass lost. This being said, I don't think there's any way to get an exact measurement. Even where the rotating mass is lost will make a difference. 1lb lost at the tire tread will make a bigger difference than 1 lb lost near wheel bolts.
In terms of converting that to horsepower, it depends on the power to weight ratio before the weight loss.
For instance, let's just assume we agree with the 4/1 ratio for rotating vs spring.
Let's further assume we're talking about a 4000lb vehicle with 500hp (ie. much like an E60 M5). We're starting off with a 8 lbs per hp ratio.
Let's take 50 lbs off of the rotating mass. Given our 4/1 assumption above, that is equivalent to losing 200 lbs. We're now at 3800lbs and 500hp, giving us 7.6 lbs per hp.
If we wanted to do this by increasing horsepower instead of losing weight:
4000 / 7.6 = 526hp
In other words, we could gain 26hp and we'd be at the "same place."
How much weight would we need to lose to be equal to a 100hp gain in this example?
4000 / 600 = 6.67 lbs per hp
6.67 * 500 = 3333.3 lbs
4000 - 3333.3 = 666.67 lbs sprung weight lost
666.67 / 4 = 166.67 lbs rotating weight lost
166.67 lbs is a LOT of rotating weight to lose
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I trust virtually nothing I read on model-specific enthusiast boards - because hillbilly physics.
You'll find more about the effects of rotational mass here: https://www.google.ca/search?q=moment+of+inertia+speedtalk+rotational+mass&oq=moment+of+inertia+speedtalk+rotational+mass&gs_l=mobile-heirloom-serp.3...14302.18916.0.19403.16.16.0.0.0.0.373.3242.2j6j7j1.16.0.msedr...0...1c.1.34.mobile-heirloom-serp..12.4.759.y7jJZz-wmv4&gws_rd=ssl#q=moment+of+inertia+speedtalk+rotational+mass+site:speedtalk.com&safe=off (https://www.google.ca/search?q=moment+of+inertia+speedtalk+rotational+mass&oq=moment+of+inertia+speedtalk+rotational+mass&gs_l=mobile-heirloom-serp.3...14302.18916.0.19403.16.16.0.0.0.0.373.3242.2j6j7j1.16.0.msedr...0...1c.1.34.mobile-heirloom-serp..12.4.759.y7jJZz-wmv4&gws_rd=ssl#q=moment+of+inertia+speedtalk+rotational+mass+site:speedtalk.com&safe=off)
And yes, the better the N/A engine you build the better it responds to boost.
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I like how losing weight at the wheels is any kind of equivalent of sprung weight...
Last time I checked, wheels are unstrung weight.
it's all about polar moment of inertia. It's the distance from the centerline that is just so slight a factor.
Try this, grab a 15# bowling ball and hold it against your chest. Clock out long it takes to spin your body to full speed. Then clock how long it takes to stop.
Then hold the same ball at arms length and do the spin test again. After your arm bones fuse back together, write down the difference an arms length made.
Fun fact. The weight exerted on the floor was the same on both tests.
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It's really a complex calculation and there are a lot of variables at play.
For instance reducing weight of the pulleys, flex plate, converter has a greater effect in first gear than it does in second gear and even more so when compared to third because we are dealing with rotational acceleration which is affect by the gear ratios.
Reducing weight of the wheel/tires gives a variable result because, as Earl points out, the effect depends upon where along the radius the weight was removed.
Removing weight is good. Reducing rotational weight is also good...but how good may not be nearly as good as one thinks.
I was thinking the other day that I have been playing with cars about 55 years. And, if you take any ten year period, about 95% of what I learned turns out to be untrue at some later date. Magazines are always interesting but they tend to print what their advertisers want them to print. Often the results cited have zero to do with the reasons written down.
There is a reason that the really successful guys employ top notch engineers and there is a reason why they seldom tell us the real truth behind why they do what they do. In the day of Google, science is taking a real hit.
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When does light become too light? I know when doing work torque is what gets it done. A big flywheel to keep ot spinning helps in many applications. That in motion and at rest statement and all.
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HRE wheels president explains rotational inertia:
https://youtu.be/-3FDthcLieE (https://youtu.be/-3FDthcLieE)
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When does light become too light? I know when doing work torque is what gets it done. A big flywheel to keep ot spinning helps in many applications. That in motion and at rest statement and all.
Mot really. A flywheels takes away from the power pulse and stores it. It also acts as a smoothing medium of sorts between power pulses. I.E. conveterting kinetic energy into potential energy and back....
They also pay attention to moments of inertia, hence the large O.D. The same way a smaller torque converter allows an engine to rev faster.
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https://www.physicsforums.com/threads/rotational-mass-and-energy-required.577882/ (https://www.physicsforums.com/threads/rotational-mass-and-energy-required.577882/)
Simple calculators: http://hpwizard.com/rotational-inertia.html (http://hpwizard.com/rotational-inertia.html)
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When does light become too light? I know when doing work torque is what gets it done. A big flywheel to keep ot spinning helps in many applications. That in motion and at rest statement and all.
Maybe you could stop by my local track and explain the big flywheel thing to the guy with the 4 speed 55 Chev that falls on its face when launched.
All this weight talk reminds me. I gotta drop off this fiberglass bumper at the bodyshop and get 'er painted.
Let's keep this thread rolling. True or false. Higher compression ratio produces more exhaust velocity and more heat...thus quickening spool time.
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True or false. Higher compression ratio produces more exhaust velocity and more heat...thus quickening spool time.
Really it depends. If the cam and ignition timing, fuel, and architecture of the engine (and drivetrain) are not optimized for it: no. The whole engine must be designed as a package to perform as such.
10 seconds on Goofle later...
http://www.xcceleration.com/cr-boost%20101.htm (http://www.xcceleration.com/cr-boost%20101.htm)
http://energy.gov/sites/prod/files/2014/07/f17/ft016_heywood_2014_o.pdf (http://energy.gov/sites/prod/files/2014/07/f17/ft016_heywood_2014_o.pdf)
https://www.physicsforums.com/threads/high-compression-turbocharged-engines.646362/ (https://www.physicsforums.com/threads/high-compression-turbocharged-engines.646362/)
Garrett still wants you to run low compression and a big turbo:
http://www.turbobygarrett.com/turbobygarrett/compression_ratio_with_boost (http://www.turbobygarrett.com/turbobygarrett/compression_ratio_with_boost)
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http://speedtalk.com/forum/viewtopic.php?f=1&t=39166 (http://speedtalk.com/forum/viewtopic.php?f=1&t=39166)
My experience is that more compression (with no change in the cam) will raise the dynamic compression ratio creating more cylinder pressure so that the car spools faster. Now, according to the above link, the exhaust temp may go down and that makes sense when I think about it. On the other hand, I am guessing the velocity will actually increase.
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Hmm why do higher compression motors run hotter if the exhaust temp is lower?
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because they release more heat into the cylinder to drive the piston downward and this heat is absorbed by the coolant passages and the oil....
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I'm still confused how can there be cooler exhaust then? Would there not be more heat in the exhaust gas also.
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There is a more complete burn within the combustion chamber so the gas temperature that emerges should be less if the tune is correct.
Remember that an engine is essentially a heat pump. Adding compression builds more heat because the heat is contained better in the cylinder due to the completeness of the combustion. If the timing is reduced too much, then we get more heat out the exhaust valve...and we get less power
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and add to the above that the act of driving the piston down absorbs quite a bit of the heat generated by combustion so there is less left to exhaust
a compressed gas cools when allowed to expand
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Let's keep this thread rolling. True or false. Higher compression ratio produces more exhaust velocity and more heat...thus quickening spool time.
Static or Dynamic?
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I'm still confused how can there be cooler exhaust then? Would there not be more heat in the exhaust gas also.
10% cooler and 12% more of it.
Lower temp in degrees, but more heat in total.
(those numbers aren't exact)
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It's widely accepted that cooler air can make more power because the air is more dense.
The earth's atmosphere contains 78% nitrogen, 21% oxygen and 1% other gases of which .03% is carbon dioxide, the composition and percentages of those gases remains constant no matter what the elevation is but the pressure decreases as the elevation increases.
With that being said, at sea level, what temperature would we see a negative benefit on power increases due to the density of the air?
Also, what would be the ideal temperature and elevation (density altitude) to get the most benefit from the turbo before getting the compressor wheel into blade compressiabili ty?
One other thing, in the aviation community engines are spec'd for the power they can make on what is called a "standard day." A standard day being at sea level, 15 degrees C (59F) and altimeter setting of 29.92 inHg (1013.25 mbar). How does the automotive world spec their engines? I mean I can dyno an engine at Pike's Peak and get some numbers and then go to Galveston and dyno the same engine and get completely different numbers.
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There should be a dyno correction applied to bring the readings to standard....NH RA used to, and probably still does, apply a density altitude correction to compare cars from different venues as I recall.
I don't know if there is a tipping point, but we do everything we can practically to get the intake air as cold as possible to obtain the densest air going into the engine and, of course, we add fuel to keep the a/f where we want it.
Bigger intercoolers, intercoolers submerged in ice/water or alcohol, spraying the intercooler with co2 out of bottle, alky injection both post and pre-turbos, etc. I would say the colder the air the better as long as the air is dry as possible.
As humidly increases, the less the "air" going into the engine.
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many articles out there discussing dyno corrections... here is one http://www.superchevy.com/how-to/ghtp-1109-fact-and-fiction-of-dyno-correction-real-wheel-horsepower/ (http://www.superchevy.com/how-to/ghtp-1109-fact-and-fiction-of-dyno-correction-real-wheel-horsepower/)
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The earth's atmosphere contains 78% nitrogen, 21% oxygen and 1% other gases of which .03% is carbon dioxide, the composition and percentages of those gases remains constant no matter what the elevation is but the pressure decreases as the elevation increases.
Correct, but why mention % since all calculations are done with pressure and volume? I do realize the last portion kind of explains that. For me I always use the diameter formula for calculating volume, not radius because you don't buy pipe by radius even though it does give you the same answer.
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The earth's atmosphere contains 78% nitrogen, 21% oxygen and 1% other gases of which .03% is carbon dioxide, the composition and percentages of those gases remains constant no matter what the elevation is but the pressure decreases as the elevation increases.
Correct, but why mention % since all calculations are done with pressure and volume? I do realize the last portion kind of explains that. For me I always use the diameter formula for calculating volume, not radius because you don't buy pipe by radius even though it does give you the same answer.
You must stop eating Quibbles and Bits for breakfast!
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I only mention that because of the practical aspect of it. You don't go out and order radius pipe, so you divide by 2 then multiply by 2 again when you order it. Just Monday, I used the steam tables to cross reference what temperature a coil should have at a given pressure, it was bang on for one and the other was off 20'C which is telling me the control valve isn't opening up all the way.
Steve, I only mention that because a really smart person mentioned it to me once and when you think about it, he was totally right. Makes calculating and ordering of parts much easier, with less likely hood of ordering the wrong part because of something like I need a 6" diameter pipe but I accidently ordered 3" because I was thinking of radius. This is why you stick with a practical standard.
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The earth's atmosphere contains 78% nitrogen, 21% oxygen and 1% other gases of which .03% is carbon dioxide, the composition and percentages of those gases remains constant no matter what the elevation is but the pressure decreases as the elevation increases.
Correct, but why mention % since all calculations are done with pressure and volume? I do realize the last portion kind of explains that. For me I always use the diameter formula for calculating volume, not radius because you don't buy pipe by radius even though it does give you the same answer.
I used percentages of the contents of the atmosphere to represent the atmosphere as a whole. It was not meant as part of the equation, only to represent the contents of our atmoshpere when measured in inMg or mBar at sea level
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Let's keep this thread rolling. True or false. Higher compression ratio produces more exhaust velocity and more heat...thus quickening spool time.
Static or Dynamic?
Hence my point about cam timing. The valve events mean a lot.
http://www.hptuners.com/forum/showthread.php?35092-Basic-VVT-Tuning-info (http://www.hptuners.com/forum/showthread.php?35092-Basic-VVT-Tuning-info)
http://www.theturboforums.com/threads/369240-How-does-cam-overlap-affect-spool-rpm (http://www.theturboforums.com/threads/369240-How-does-cam-overlap-affect-spool-rpm)
http://www.hotrod.com/how-to/engine/ctrp-1106-turbo-camshaft-guide/ (http://www.hotrod.com/how-to/engine/ctrp-1106-turbo-camshaft-guide/)
Who is more right? I'd say the guy with the quickest car.
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The TSM guys are handcuffed with the 3 bolt turbos. The reading I'm doing suggests they're using some real oddball cam grinds...espec ially in respect to exhaust cam timing.
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What are they trying to accomplish with the odd grinds? Open longer to let the incoming charge push the exhaust out?
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What are they trying to accomplish with the odd grinds? Open longer to let the incoming charge push the exhaust out?
I am certain exhaust duration and overlap are key players in tuning around (band-aiding for) a restrictive exhaust scenario.