Turbo Question? What does it mean...
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liquid00meth
Senior Member
your a/r is the ratio of compressed air to "blown" air. The higher the a/r, the bigger the turbo. IE a turbo with .4 a/r will probably spool insanely fast, but won't blow much air, while a turbo with 1.2 a/r is massive, and probably won't spool to fast - but when it does, it will be blowing ALOT of air.
I have no clue what those P,0,q things are though
I have no clue what those P,0,q things are though
liquid00meth
Senior Member
buy a boost controller
ok hold up.... lots of mis info in here.....
straight from Corky Bell's book, Maxium Boost.
That said, the larger the a/r, the longer it will lag, but the more potential it has for top end power.
IT IS NOT TRUE that the larger the A/r, the larger the turbo. a/r doesn't not efect housing size.
IT IS NOT TRUE that the a/r is a ratio of compressed air.
a/r = area over radius. as you can see in the diagram, a1 goes with r1, and so forth, and they are equal at all those points.
P,Q,R etc are trims of compressor wheels... im sure you have heard of staeg3 and stage 5 wheels, well, they all get a letter too. I'm not sure off hand what is what... but for all intense and purposes, stage 5 is as high as you need to go on a street car.
all boost levels are controlled by the wastegate, not a boost controller.
all a boost controller does is trick the wastegate into seeing less boost, so that it thinks you are only at 5 psi instead of 10 for example, and thus will keep the gate closed longer so as to increase boost presure.
a boost controller is good for about double the wastegate;s spring. so if your gate comes with a 7psi spring, then you should be able to use a boost controller to 14 psi.
there are many other things that come into to play though running 13 psi.
you need a 3-bar map sensor above 10.65 psi on obd1 and 2, and 9.5 i think it is for obd0.
you have lots to learn about boost. I highly suggest you pick up corky bell's book. amazon has it, so do other places.
and for fucks sake, THE is spelled THE, not DE.
do you speak it?
straight from Corky Bell's book, Maxium Boost.
That said, the larger the a/r, the longer it will lag, but the more potential it has for top end power.
IT IS NOT TRUE that the larger the A/r, the larger the turbo. a/r doesn't not efect housing size.
IT IS NOT TRUE that the a/r is a ratio of compressed air.
a/r = area over radius. as you can see in the diagram, a1 goes with r1, and so forth, and they are equal at all those points.
P,Q,R etc are trims of compressor wheels... im sure you have heard of staeg3 and stage 5 wheels, well, they all get a letter too. I'm not sure off hand what is what... but for all intense and purposes, stage 5 is as high as you need to go on a street car.
all boost levels are controlled by the wastegate, not a boost controller.
all a boost controller does is trick the wastegate into seeing less boost, so that it thinks you are only at 5 psi instead of 10 for example, and thus will keep the gate closed longer so as to increase boost presure.
a boost controller is good for about double the wastegate;s spring. so if your gate comes with a 7psi spring, then you should be able to use a boost controller to 14 psi.
there are many other things that come into to play though running 13 psi.
you need a 3-bar map sensor above 10.65 psi on obd1 and 2, and 9.5 i think it is for obd0.
you have lots to learn about boost. I highly suggest you pick up corky bell's book. amazon has it, so do other places.
and for fucks sake, THE is spelled THE, not DE.
do you speak it?liquid00meth
Senior Member
but in terms the guy can understand, big a/r means lag and more top end , small a/r = fast spool and less top end. 
Isn't top ened everything though in drag racing? I mean once you get up in the high rpm's you dont' really drop past 5k or anything. I know when I shift from 1-2nd, etc on my car it doesnt' go below around 5500 area at most, so wouldn't you still be at full boost? the whole time after 1st gear where that would be the only time you felt lag.
In other words, I say fuck lag, get the big boy.
In other words, I say fuck lag, get the big boy.
liquid00meth
Senior Member
yes. That is why drag cars usually have outrageous A/Rs ie. 1.0+
You wont be saying fuck the lag when you get a turbo that spools at 4k and you are driving around town. If you just have a drag car it is fine, but if you have streep/strip you dont want something so outrageous that it makes the driving experience horrible. If you do get a turbo with a huge a/r, the boost comes in surges around the street and it will not be pretty.
liquid00meth
Senior Member
yea seriously, it will be like your accelerating normally from a stop light, and as soon as you hit 4k your tires just start smoking. lol. not too fun.
you peaople have a huge misconception of boosted cars
accerlating away from a stop light can be done with a t88 at 25 psi on a 1.5 a/r with the same smoothness as your stock geo metro.
around town, you pobably won't boost anyway. it takes a combination of throttle pressure, and revs, to make the boost happen. at 20% throttle (average acceleration let's say) you aren't putting out enough gasses to get out of vacuum. and thus, the car drives normal.
Lag is GREAT for around town. there is no need to have 10 psi on your 14b when you are going to the grocery store. stay under 4 or 5k for normal driving, and easy throttle, and the car will run perfect, if not alomst N/A. lag is also great on the highway... crusiingin in 5th gear, you don't want to be in boost for long periods of time straight... like 15 secs max, otherwise shit gots STUPID hot and detontation starts to happen. so crusiing at 80mph, you are at about 4500 on a gsr tranny... do you want to be at full boost right away when time comes to give it more gas to pass someone? or do you want to ease into the thrttole a little more and gradually, but quickly gain boost and pass?
My turbo is probably going to spool aroun 45-4800 give or take. it is a street car. it is my only car. it will be driven every single day.
you mention surge. I don't think you have a full grasp of what the surge limit of a turbo really is.
The surge limit is the LEAST amount of exhaust air needed to spin the turbo to create boost on any given turbo(surge limit will be less on smaller turbos). I used the wrong word before. I meant that boost will not be there and then all of a sudden it WILL be there on a huge a/r. Most people on this board i dont think accelerate at 20% throttle anyway.
You are on FWD, you WILL squeal tires accidentally on a turbo this big when boost hits, it will be anything BUT smooth.
Type R got 
thanks for supporting my point of view on big turbo=better.
B will be soon driving around on 20% throttle, but really I drive around on 30% and I am still slow as fuck but I can accelerate like every other big ass suv and metro on the road.
Once he goes 100% damn, those bitches are going to spin like mad.
thanks for supporting my point of view on big turbo=better.
B will be soon driving around on 20% throttle, but really I drive around on 30% and I am still slow as fuck but I can accelerate like every other big ass suv and metro on the road.
Once he goes 100% damn, those bitches are going to spin like mad.
liquid00meth
Senior Member
it's all in how you want to look at it. I agree that lag can be your friend. But at the same time, it can kind of be dangerous when your dealing with large turbos that can "turn on" very harshly. I agree it is also about self control and responsibility when you have something that is so easily abused.
