Silvia Club of NSW

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 Post subject: Boost, Street and drag.
PostPosted: Wed Nov 16, 2005 6:20 pm 
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T28

Joined: Tue Nov 15, 2005 7:47 pm
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Car: Ford Telstar (LOL)
Hi,
I was wondering, are you able to get BC that have 2 settings, like street and drag.
Dont have the car at the moment but will be a S13 Silvia with an SR20DET and will recive a turbo upgrade straight away (GARRETT GT28RS) with a Low Mount Turbo Manifold, as well as all the other stock mods if not on (Pod, 3' exaust, ect.) and maby some HKS step 1 cams (264/264 'later mod') or somthing like that.

I ask as i do not want to run the car at full boost all the time. I will be driving to work every day (50k's each way) and do not want to run it at full boost.
Now in saying that is there any reason not to run it at full boost all the time? or on the way to work?
Any input? Do and Don'ts? Any other mods to look at?

P.S Anyone selling a S 13 Silvia? Sorry but has to be an Auto SR20DET.
Thanks


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PostPosted: Wed Nov 16, 2005 10:11 pm 
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people arent aware but the best boost controller is free. via your right foot. mine is left on the high boost setting all the time. if i only want 0.5bar i only push the pedal that far. simple!!

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PostPosted: Wed Nov 16, 2005 11:47 pm 
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more boost, floor it 8)

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PostPosted: Thu Nov 17, 2005 12:43 am 
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zei20l wrote:
if i only want 0.5bar i only push the pedal that far. simple!!


I dont think thats entirely accurate actually;

you are correct in that pressing lighter on the pedal will allow less boost, say a constant 0.5bar for example, but teamed with that 0.5bar, youve only got the throttle body open 25%...

I would rather have 0.5bar with the TB open 100% personally...

to me,
Boost = density,
Pressure = flow

High pressure = less lag :)
High boost = high power :P
High boost + high pressure = low lag and insane power :D

My way of thinking of the whole boost and flow issue is this;
Imagine that 0.5bar is the pressure/density of water...
Keep imagining for me;
- TB open 100%
- The cylinder will only be opened for say, 1 second. You have to cram all the fuel and air you can in there in that 1 second.
Now on a T25G at 0.5bar, we have the density of water; its a shit, slow turbo, so lets pour our 0.5bar water in that cylinder for 1 second.. w00t i got it half full!! Change that T25G to a T28; same pressure (water)... pouring for 1 second... BOOYAH 80% full! Why? because it flows at a faster rate.
More boost = higher density, so its like 50ml of water (0.5bar) vs 50ml of mercury (1bar)

If that makes any sense at all to anyone but me, w00t... Laugh at me all you want; I explain it to people that way and then they understand the concept :P (Answering the question "why does a t28 at 7psi give more power than a t25g at 7psi - its the same boost!??!?")

Zei, if youre trying to put all that 0.5bar into the engine, dont you think the nice restriction in the form of a 75% blockage by the throttle body would reduce the flow of our 0.5bar water?

Its not making boost because the exhaust isnt spooling up the turbo enough; it isnt making the exhaust because it isnt making the power.
When you run with boost restricted to 0.5bar, the turbo WANTS to make 30psi but youre saying "no more", so its making the necessary exhaust flow to make more boost, therefore making more power.

nfenech: If you are talking about casual cruising all the way to work and back, you should never hit full boost; if you want to drive hard with less power (and better fuel economy), get a dual stage boost controller, but if you plan on grandpa-ing it the entire time, meh! leave it on high boost and dont press too hard on the go pedal.


I definitely hope my understanding of the turbo flow is correct :P


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PostPosted: Thu Nov 17, 2005 6:34 am 
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Twin T04
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In the end your right foot controls the power which is what matters, the only reason you'd need to restrict the boost is if something was wrong, eg you got a bad fill of fuel.

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If that makes any sense at all to anyone but me, w00t... Laugh at me all you want; I explain it to people that way and then they understand the concept (Answering the question "why does a t28 at 7psi give more power than a t25g at 7psi - its the same boost!??!?")


Nope, your explanation is wrong.

Take a GT-RS and a T28, using your explanation they will make exactly the same power


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PostPosted: Thu Nov 17, 2005 8:09 am 
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omg wrote:
Nope, your explanation is wrong.

Take a GT-RS and a T28, using your explanation they will make exactly the same power


How so? Cmon - if im to be told im wrong, you may as well say WHY :P


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PostPosted: Thu Nov 17, 2005 8:14 am 
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Control is the right foot, as everyone (but ark who like pouring water into his engine) has stated.

My car is running 20psi max and the ebc settings haven't been changed since it rolled off the dyno. Am i constantly putting 20psi through the engine? No. Does it matter that it's pissing down outside? No. Do i care if i'm putting 7 or 10psi into the engine at partial throttle? No. Do i want to rev the tit's out of my engine at 7psi to make the same power i can make at 3k with 14psi (at partial thottle)? No.

Do i want the rush of midrange torque that comes with running big boost and partial throttle? Fuck yes.

Ark, a small correction. Boost = pressure (thats why it's measured in psi/bar/mmhg/kg/cm2....).

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PostPosted: Thu Nov 17, 2005 8:31 am 
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boost=pressure
flow=power

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Sil80 - SR20DET 231rwkw
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Stagea - DeathWagon - RB25DET 185rwkw.

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Last edited by too_much_boost on Thu Nov 17, 2005 10:19 am, edited 1 time in total.

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PostPosted: Thu Nov 17, 2005 10:12 am 
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Twin T04
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Ark - compressor efficiency, that's why turbos with an identical rear end (and so identical flow) will make different power


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PostPosted: Thu Nov 17, 2005 11:23 am 
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Twin T51
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In answer to your first question, yes you can get boost controllers that will operate like this turbo smart make on, and most electronic boost controllers will be able to do it for you (low/hi modes).

You'd be able to get a ebc for a bit more than the turbosmarts, and would be a better option.

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PostPosted: Thu Nov 17, 2005 3:02 pm 
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T28

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Thanks a lot.
I'll opt for the ebc one. Thanks for all the info.


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PostPosted: Thu Nov 17, 2005 3:10 pm 
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okey dokey, never mind me :)

I ask people to teach me about the ins and outs of turbos and i get linked to howstuffworks.com... that teaches alot :roll: lol


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PostPosted: Thu Nov 17, 2005 3:58 pm 
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Ark - here's a tip.... stop complaining that others won't do the groundwork for you and buy a book on the topic and put in some effort yourself.. Seems you don't understand the basics yet, and that link i sent you should have at least taught you that

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Sil80 - SR20DET 231rwkw
Silvia Race Nugget - SR20DET 225rwkw
Stagea - DeathWagon - RB25DET 185rwkw.

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PostPosted: Thu Nov 17, 2005 4:54 pm 
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That howstuffworks article (http://auto.howstuffworks.com/turbo.htm) is actually pretty good, and if you understand everything in it you can work out why different turbos and boost pressures behave the way they do.

Engines make power by burning fuel and air.
The more air you get into the engine the more fuel you can burn, hence more power.

Boost is the difference between how much air the engine car flow, and how much air the turbo is trying to push in.
If the engine can flow a maximum of x litres of air per second at atmospheric pressure, increasing the pressure at the intake will force it to pass more air through - so it can make more power.
In theory, 1 bar of boost would double the engine's power, but since the turbo causes a restriction on the engine's exhaust (reducing its total flow capacity) and there are other heat losses it's not that efficient.

Smaller turbos restrict the exhaust more, and can't flow as much air, so the engine will make less power at high rpm.
An SR20 will "overtake" the air capacity of a T25G at 1bar at high rpm, which is why the boost tapers off.
A T28 has a larger compressor and is more efficient so it can keep supplying enough air to maintain 1bar (or more) of pressure at the intake.
If you put a set of cams in the engine, port the head, and use very high flowing intake and exhaust systems the SR will start to outflow a T28, so the boost will taper off in the top end again.

A really big turbo has the same problem at low rpm, where there's not enough exhaust gas to spin the turbo fast enough to flow more air than the engine.

This is why it's important to match a turbo to the engine.

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PostPosted: Thu Nov 17, 2005 7:57 pm 
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Quad T66
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power = fuel + air
mass of air = boost/pressure x temperature x volume

in very simple terms... to explain how you get different levels of engine power at same boost pressure and volume (engine capacity), different compressors with different efficiencies will change the temperature variable in that equation for differing amounts of flow


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