| | | quote | Originally posted by tjm4fun:
you reasoning has as many flaws as sts's claims.
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That's an odd statement for someone who goes on to reiterate everything I've said.
Let's take a look:
| | | quote | 1.) whether a tube is 18" or 18' 5 psi is 5 psi.
2.) the issue is volume flow, and lag.
3.) air is compressable,
4.) so you could have a delay in seeing the pressure increase from the length of the pipe from the turbo. likewise a delay in the exhaust pressure build up to kick up the turbo.
5.) With considerations of that, properly sizing the unit will minimize the latter, and reduce the effects o fthe boost lag.
6.) drivability will only be minimally effected.
7.) the impact would actually be worse in a track environment, as the unit would would be over boosted/driven with the staging powerbrake.
8.) you would need to use a different turbo setup in that case. |
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1.) I agree, but you seem to be disregarding the fact that the 18 foot tube has 12 times the volume to be pressurized.
2.) This, I also agree on. It is my primary point of contention, actually.
3.) This is so important to my argument that I split it from the rest of the sentence to address it. When the turbo starts to produce boost, all the volume of air in the intake plumbing has to be compressed before the engine will see any boost, so it WILL take longer for the same turbo to pressurize the 18 foot pipe versus the 18 inch one.
4.) The first part of this line is correctly included in the term "turbo lag", while the second is more correctly included in "boost threshold". Most people don't understand boost threshold, and just lump it all into "turbo lag", though the two are actually independent of each other (for the most part). Turbo lag is the time from when the turbo begins spinning fast enough to produce positive air flow to when the intake manifold begins to see positive pressure. "Boost threshold" is the engine speed where the engine is creating enough exhaust to begin spooling the turbine. Now, when you have to pressurize more exhaust system, the engine has to pump more exhaust into the pipes, and given the same turbo, a longer exhaust system will mean the boost threshold will increase. Also, the exhaust gasses will have more time to cool before reaching the turbo, cooler exhaust will have a lower pressure then hotter, further decreasing the efficiency of the system, and effectively raising the boost threshold by requiring more exhaust to reach the same pressure.
5.) Making "considerations" for mounting the turbo in a less efficient location means you will have to make compromises in the design to try to counteract the design elements you are "considering". When you compromise on turbo sizing you will limit the potential power output of the system. You could also compromise on tubing sizes, keeping them small to limit volume increase due to length, but smaller tubes
may limit power (as long as the initial sizes were correct for the intended power goal, then reducing them
will reduce power, but if they were too big, it could help things).
6.) But drivability will be affected. So will power production. You
will have more lag, and make less power than a system with fewer compromises in the name of "a simple install". But if a simple install is all you're looking for, then it wouldn't be so bad, you'd get a bit more power and wouldn't have to do much work in the engine compartment.
7.) But the problems come from the delay in pressurization, and power braking will allow all the pressurization to occur before the lights come down, therefore it doesn't matter where you put it, provided you size everything
properly for the intended power levels (i.e. really big exhaust, really big turbos, really big intercooler, etc.). And I have no clue what you mean by, "the unit would would be over boosted/driven with the staging powerbrake". There is no way you'd see maximum boost at the staging lights, let alone over boost.
8.) Of course. No street turbo is even remotely correct when you are tuning for all out, maximum performance. No racer planning on being competitive would run a turbo sized for street driving on the track, unless class regs required him to.
