Restrictor plate in BEGi exhaust
#81
Someone should probably explain the difference between boost overshoot and boost creep. I'm pretty sure Dann is referring to creep (boost rises with RPM regardless of wastegate spring pressure), while everyone else is referring to overshoot (boost rises rapidly past the wastegate spring pressure which creates torque spikes that can damage stock engines).
let me google that for you Dann
http://lmgtfy.com/?q=what+is+boost+creep
#84
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e: This thread is basically a clusterfuck of nomenclature. Boost creep (boost rises with RPM, max boost at/near max power) doesn't put any additional stress on rods if it doesn't move the torque peak up. Uncontrolled creep is still not desirable because you can outrun the fuel injectors and it generally means the wastegate setup is pretty ****-poor. Boost overshoot (boost immediately rises beyond the desired level, max boost at/near max torque) is seriously undesirable in all cases and, by definition, is never induced on purpose. Most of you are talking about overshoot, but saying "creep". Dann is talking about creep as I've defined it.
Can we get back to talking about how kludgy exhaust restrictors are now?
#87
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**** all your strawman semantics arguments. That includes you vlad.
this is what we are discussing:
and I'm the only one who's addressed his question and completely bogus statement and it pisses me off that you're wasting words talking about creep or overshoot or creep vs overshoot.
Nitro's theory is that peak torque on a dyno plot is the peak load of an engine's conponents, so he tunes his cars to increase boost after peak torque to keep the torque output flat to redline.
talk about that.
this is what we are discussing:
Originally Posted by nitrodann
Seriously, why do we give a **** if we get 5psi of creep past peak torque?
If its past peak torque then its not putting any more stress on any components than peak torque already did. Which is why its called -peak- torque.
Nitro's theory is that peak torque on a dyno plot is the peak load of an engine's conponents, so he tunes his cars to increase boost after peak torque to keep the torque output flat to redline.
talk about that.
#91
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in regards to tensile or total inertial loads, yes. total compression or power loads, no.
if you're inducing "creep" to maintain peak torque to redline, you're putting more load/stress on the rods the greater the rpm.
if you're inducing "creep" to maintain peak torque to redline, you're putting more load/stress on the rods the greater the rpm.
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More tensile load/stress, yes, but not more than a stock motor can handle (unless you rev it past 7k, which nobody has suggested). The compression load is what the stock rods care about, and the peak compression load happens at peak torque.
IOW, if the motor copes with 230wtq at 4000rpm, is 210wtq at 7000rpm going to break it? I think not.
IOW, if the motor copes with 230wtq at 4000rpm, is 210wtq at 7000rpm going to break it? I think not.
#97
Nitro, Hang in there.
Vbad, ??//?????///???
2D: You need V clamp? I Make V clamp. A/O can do both.
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.
It appears nitro has figured this out, its just hard to get past the accent.
Subject for the next thread: In what month of the year do the Aussies drink the least amount of Tequila?
corky
Vbad, ??//?????///???
2D: You need V clamp? I Make V clamp. A/O can do both.
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.
It appears nitro has figured this out, its just hard to get past the accent.
Subject for the next thread: In what month of the year do the Aussies drink the least amount of Tequila?
corky
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More tensile load/stress, yes, but not more than a stock motor can handle (unless you rev it past 7k, which nobody has suggested). The compression load is what the stock rods care about, and the peak compression load happens at peak torque.
IOW, if the motor copes with 230wtq at 4000rpm, is 210wtq at 7000rpm going to break it? I think not.
IOW, if the motor copes with 230wtq at 4000rpm, is 210wtq at 7000rpm going to break it? I think not.
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.
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I haven't really read up on loads in a quite a while--it's probably been over 10 years.
I was thinking that if you added boost to redline and since tensile load is a function of rpm^2 that the loads would significantly increase as you reach redline, compared to if you held it steady. But that was wrong because that extra boost doesn't really factor into those loads and any increase in boost is really just making up for the loss of combustion pressure due to the speed of the explosions relative to the crank angle and all that business.
Plus I really just wanted to argue about something.
it takes a brave/strong man to admit he was wrong--remember that.
Last edited by Braineack; 03-11-2015 at 08:16 AM.