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Old 03-11-2015, 09:33 AM   #101
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Quote:
Originally Posted by Corky Bell View Post

Loads: Get a plot of chamber pressure vs crank angle. Multiply piston area times chamber pressure at every degree and plot. At each degree of crank angle, calc the inertial loads. Plot. Add the two loads together for every degree for a total load. Calc column buckling strength of the con rod. Take worst case compressive sum and adjust boost (reflecting pressure load) and rpm (inertial load) to stay below the column buckling load.
I read that page in your book yesterday. I think I found an error in your Power formula on page 7. Power = Torque x rpm, shouldn't it be Power (HP)= torque x RPM / 5252
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Old 03-11-2015, 10:16 AM   #102
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No no, my MX6 makes 1,900,000hp at 3800rpms.
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Old 03-11-2015, 10:25 AM   #103
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It doesn't say Power = HP

it says Power = P x L x A x N
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Old 03-11-2015, 10:37 AM   #104
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The "5252" factor would only come in when specific units are attached to the formula. If power were in KW, and torque were in N-cm, then the acutal number would be something else.
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Old 03-11-2015, 11:19 AM   #105
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Quote:
Originally Posted by Braineack View Post
It doesn't say Power = HP

it says Power = P x L x A x N
Quote:
Originally Posted by DNMakinson View Post
The "5252" factor would only come in when specific units are attached to the formula. If power were in KW, and torque were in N-cm, then the acutal number would be something else.
I sort of thought that might be the case the first time I read it. I realize it was unit-less now that I went back and read it a second time. I searched around the internet for a bit, but didn't (easily) find confirmation that the 5252 can be disregarded when your factors are unitless.
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Old 03-12-2015, 12:35 AM   #106
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Quote:
Originally Posted by nitrodann View Post
I'm sorry why is there a 'goal boost' ?

Dann
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Originally Posted by 18psi View Post
because there is such a thing as stock rods
Not just stock rods, it could be a stock 5 speed, or having 225/45/15 street tires instead of fender flares and 275/35/15 race rubber, a lot of factors go into this. I am very traction limited on 225's with 280 wheel HP, I can't imagine it being better with 350 WHP on those same 225's.

I am talking about boost creep, not boost overshoot.

Nitrodann, if you honestly don't understand why someone would want functional boost control where you can set it at your goal boost and not have it creep then why do you have a wastegate? One of the reasons I want to get ride of creep is so I can have what you have... controlled rise in boost pressure as RPM's rise.

Your entire argument is based on you having a system that does not have boost creep and asking us why we want a system that functions as well as yours does. I know you don't have boost creep because if you did you couldn't have controlled rise in boost pressure as RPM's rise, you would have uncontrolled rise in boost pressure as RPM's rise.

Keith
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Old 03-12-2015, 12:46 AM   #107
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Quote:
Originally Posted by Corky Bell View Post

2D: You need V clamp? I Make V clamp. A/O can do both.


corky
My current turbo is V-band clamp, so I would need A/O setup for V-band on booth the manifold and downpipe.

You mentioned that I would need modifications to the turbo to run it on the A/O system, that is why I mentioned it was a V-band housing and that I have modified the clocking of the compressor housing... trying to clarify what turbo modifications would I need to make to run my current turbo (spud with tial V-band turbine housing) on the A/O system so I know if it is something I can do, or if I need to send it in to you.

Keith
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Old 03-12-2015, 01:28 AM   #108
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Quote:
Originally Posted by Twodoor View Post
Not just stock rods, it could be a stock 5 speed

My original example given in this thread is a 280whp NA8 VVT with a 5 speed, yes i agree.

, or having 225/45/15 street tires instead of fender flares and 275/35/15 race rubber, a lot of factors go into this. I am very traction limited on 225's with 280 wheel HP, I can't imagine it being better with 350 WHP on those same 225's.

you still arent quite getting this, WHP alone has absolutely **** all to do with traction, once again, its all about the peak torque (in this case at the tyres).
Lets do some numbers. 250ft lb is the number usually used as the limit of both 5 speeds and stock rods. In my experience cars with stock engines are not significantly traction limited on stock engines, with 225 street legal tyres, and a non fucked up setup. 240 ft lb (im using a small safety margin here) is over 340rwhp at 7500rpm.
If it makes traction with that torque at 4000 itll make it at 7500.


I am talking about boost creep, not boost overshoot.

Nitrodann, if you honestly don't understand why someone would want functional boost control where you can set it at your goal boost and not have it creep then why do you have a wastegate? One of the reasons I want to get ride of creep is so I can have what you have... controlled rise in boost pressure as RPM's rise.

Your entire argument is based on you having a system that does not have boost creep and asking us why we want a system that functions as well as yours does. I know you don't have boost creep because if you did you couldn't have controlled rise in boost pressure as RPM's rise, you would have uncontrolled rise in boost pressure as RPM's rise.

Keith
I understand that people want control of their boost, but boost creep which adds 5psi from midrange to redline, as we originally discussed is less creep than you need to hold torque flat, on a miata without MONSTER cams or MONSTER sized turbo.

EDIT: Here is the boost map (duty cycle) used on the 280whp GT2560r 5 speed car, blurred out everything but the part in question, the full throttle part of the map.





That above map is directly off the tune, this below image is the with changes made to show what it looks like on a similar setup that has a little creep like the 5 psi at redline we have been discussing.



IE; in this thread, the creep being discussed is less that you actually want for peak performance and therefor is fine, in the exact same way that a 7psi WGA is fine even though it wont allow you to have less than 7 psi.

Dann
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File Type: jpg Boost_some_creep.jpg (80.3 KB, 163 views)
File Type: jpg boost_no_creep.jpg (81.7 KB, 162 views)

Last edited by nitrodann; 03-12-2015 at 02:08 AM.
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Old 03-14-2015, 08:52 AM   #109
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2d, roger, you can handle it. Outline needs later.

Power is defined as force times velocity. There are a several variations. Two are; torque times rpm, and pressure times volume rate of flow.

corky
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Old 03-14-2015, 02:53 PM   #110
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Quote:
Originally Posted by Mobius View Post
...In terms of compressive loads, 230wtq at 4000 vs 230wtq at 7000 is always going to be harder on the rods, because they have to endure that compressive load for nearly twice the amount of time.
??? I don't get this part. Which is worse? And why? I get number of cycles is higher at higher RPM, that is obvious.

But in simple terms, for a 4 stroke engine, any given cylinder is going to spend 1/4th of it's time on the power stroke, 1/4th on compression, etc.
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Old 03-14-2015, 02:55 PM   #111
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Also Dan has a lot of good points, and I think you guys are all arguing over semantics/terms. How about instead of a pissing contest, let's be civil and talk about how to make miata's go faster and keep them reliable?
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Old 03-14-2015, 04:26 PM   #112
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Brain trolled Dann, and I jumped in, Dann got his panties in a wad as always and went off on me, as always, while brain stepped back and laughed at his successful troll.

I can't believe I have to spell it out for you guys.

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Old 03-14-2015, 04:31 PM   #113
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Quote:
Originally Posted by patsmx5 View Post
??? I don't get this part. Which is worse? And why? I get number of cycles is higher at higher RPM, that is obvious.

But in simple terms, for a 4 stroke engine, any given cylinder is going to spend 1/4th of it's time on the power stroke, 1/4th on compression, etc.
At 4000 RPM as you said 1/4 of the time you are on the compression stroke, so 4000 RPM /60 = 66.7 revs per second. Invert that and you get .015 seconds or 15 milliseconds per revolution of that 15 milliseconds 1/4 are on the compression stroke so each compression stoke lasts 3.75 milliseconds.

At 7000 RPM doing the math you see that each compression event only lasts 2.15 milliseconds.

As was pointed out to me in another thread, if you have the same torque output from the engine at two different RPM's the higher piston speed moving away from the flame front at higher RPMs reduces the peak load on the rods even at the same total torque output.

Keith
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Old 03-14-2015, 05:21 PM   #114
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Quote:
Originally Posted by Twodoor View Post
....
As was pointed out to me in another thread, if you have the same torque output from the engine at two different RPM's the higher piston speed moving away from the flame front at higher RPMs reduces the peak load on the rods even at the same total torque output.

Keith
Ok that makes sense, but it had nothing to do with it enduring a load for twice the amount of time. The engine spinning faster has more events at a shorter time/even, but total time is the same. You said it endured it for twice the time, that's what didn't make sense. Time it spends during that cycle isn't WHY it has less load at higher RPM.

Basically if you measure cylinder pressure vs crank position and plot that at both RPM points, for the same torque, the motor turning slower will have higher peak pressure, as the 10-90% combustion time will occur with the piston closer to TDC than an engine turning faster.
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Old 03-14-2015, 08:21 PM   #115
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OK
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Old 03-14-2015, 08:34 PM   #116
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You want me to post the screenshot of the conversation me and Scott were having laughing at you on G-chat?

Or you wanna cry some more?

hurr durr
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Old 03-14-2015, 08:37 PM   #117
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I feel that it would be necessary for anyone but you and Scott to believe what you are saying.
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Old 03-14-2015, 08:38 PM   #118
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I dont even know what this thread is about.
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Old 03-14-2015, 10:14 PM   #119
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Quote:
Originally Posted by 18psi View Post
Brain trolled Dann, and I jumped in, Dann got his panties in a wad as always and went off on me, as always, while brain stepped back and laughed at his successful troll.

I can't believe I have to spell it out for you guys.

Well I think that's stupid if true. But I come here to talk about making miata's go fast, not to waste people's time and **** them off.
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Old 03-14-2015, 10:15 PM   #120
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no i actually made errors in my argument.
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