Okay. I'm a complete no0b when it comes to things like turbo trims and A/Rs, but I've done enough research and reading here to know that when the choad at AutoZone tells me I should "throw a t66 on there," he's a moron and doesn't have a fucking clue. What I'm looking for here is some basic info or maybe generalizations about turbos in general (and a quick lesson in how to abstain from redundancy). So far, all I really know about turbos is the following:
1. a t3/t4 is a hybrid made of a compressor housing from one mated to the turbine housing of the other (t3 mated to t4 or vice versa). 2. Lower A/R ratios translate into relatively quicker spool up, but get into efficiency issues at the top end. Higher A/R ratios will have more lag, but have longer legs, so to speak.
(Yes. The search is goooooood.)
? > So if A/R is related to the turbine, does the same sort of ratio apply to compressor wheels? Would a lower A/R (if it exists for compressors) mean a broader power band where output jumps and climbs gradually to peak? Would a higher A/R start more gradually and keep building and building to peak?
?? > Someone explain trim. (And I don't mean a clever name for pussy, although it's nice to get pussy and turbos in the same thread, isn't it?) If someone says they're running a 50trim or 60trim, is that kinda like saying they run a .50 A/R?
I've learned a lot here in the almost 2 years I've been around, but I want to learn more about turbos in general. They can be found in all sorts of cars, and our beloved little 2GNTs are not the only cars out there which came without turbos. I think it would be a good thing to maybe have a post that could someday make it to the TWSB discussing differences in turbos. It would help me out, and I'm sure it would be a nice little reward for anyone smart enough to check the search in the future.
#73871, "RE: *** turbo school imo ***" In response to Reply # 2
Originally posted by Chamuko clasroom on your lap IMO...well that didnt sound good. You get what I meant right? RIGHT!? lol j/m with ya. seriously though, best 15 bucks (about) you can spend.
#73876, "RE: *** turbo school imo ***" In response to Reply # 4
Damn. The first time I wrote that post, I mentioned something about not wanting to have to go buy that book. I know the title and the author by heart, but I'm really looking for some generalizations if that's possible. I've got other things I should be reading. So anyone who read the book and knows what's up feel like at least shedding a little light on my post? kthnx.
HotRod dot com The turbine housing A/R (area/radius) ratio is the area (A) of any turbine inlet scroll cross-section divided by the distance from the center of that cross-section to the center of the turbine shaft (R). For any given turbine housing, A and R vary in the same proportions, so all As divided by their corresponding Rs yield the same dividend--which is the A/R ratio.
Originally posted by DR1665 ? > So if A/R is related to the turbine, does the same sort of ratio apply to compressor wheels? Would a lower A/R (if it exists for compressors) mean a broader power band where output jumps and climbs gradually to peak? Would a higher A/R start more gradually and keep building and building to peak?
The compressor is exacly like a turbine in the sense that there is an A/R. You could substitute the word turbine with the word compressor in that snail caption - "For any given compressor housing, A and R vary in the same proportions, so all As divided by their corresponding Rs yield the same dividend--which is the A/R ratio.". Thats about where the similarities end.
It sounds like you have a descent understanding of how the turbine A/R affects the turbo. Check out the rest of that article for some good info. Seriously - it looks like most of it was just ripped out of the book.
Theres a fundamental difference betwen turbines and compressors though. Turbines generate power and compressors generate boost. IMO The questions about compressor A/R are moot. Whats important on the cold side is the compressor map. Your power is directly related to compressor and intercooler effeciencies, so the trick to getting the power where you want it is understanding how to read a compressor map. The best place that I've found for learning how-to read a compressor map is here - http://www.stealth316.com/2-turboguide.htm Scour that site.
Just one more thing about that last link there. My favorite quote from that page addresses the most common misconception about how a turbo works:
Stealth316 dot com This bears repeating one more time. Just because a turbo is rated at 650 CFM @ 15 psi (for example) does not mean that the turbo flows that amount of air in our 3L V6 engine at 15 psi plenum pressure. The engine mass airflow is determined by the displacement, the RPM, the volumetric efficiency, and the air density (or plenum air pressure and temperature). At a given RPM and at the same plenum air pressure and temperature, the same amount of airflows regardless of which turbo is used.
Basically - you cannot escape volumetric efficiency. It doesn't matter if you've got forced induction - the intake stroke still has to "suck" what it needs from the plenum. Boost makes the air density higher...but it doesn't "force" anything into the engine.
#73913, "RE: *** turbo school imo ***" In response to Reply # 10
Thanks Jim! I will spend some quality time with that site.
So, then, do modifications such as larger valves (intake and exhaust) and port work alter the volumetric efficiency? I'm thinking that if the engine has larger valves, it would be able to suck more a/f in and push more exhaust out. Of course, if it's more about the engine's ability to draw air in, then larger valves would possibly flow less due to a lower velocity. Just trying to wrap my head around it, ya know?
