hey guys,
I'm looking to upgrade my throttle body to something that's going to keep up with the amount of air my engine will need. I have a couple of questions about the throttle position sensor (TPS) and the idle speed controller (ISC).

firstly, the TB I'm looking at has universal TPS mounts as shown in this pic...
http://e4eonline.com/TB80/TB_FIT.jpg

I am going to pull my TB off this weekend and measure the TPS, but does anyone know if that looks like it might fit?

secondly, fitting the ISC will be interesting... again, if someone has done this, can they recommend what to look for in a TB to help with fitting the ISC?

pic of TB in question...
http://e4eonline.com/TB80/TB_400.jpg

cheers,
.wook

you could always buy a billet magna one from RPW's supplier :-) ( also haggle the price on the website )

http://www.throttlebodies.net.au/product_info.php?products_id=55&osCsid=76fc2ca37c85b5be2d520e2b55b00a52

interesting... but more than double the price and only 72mm. the one I'm looking at is 80mm and $245 delivered. maybe if I could bore it out to 78mm or so.

so uve established that the stock TB cant flow enough air for your requirements?

reason i asked i thought someone actually established the magna TB was good enough for some crazy amount of air flow....?

^ Bah. I dont believe it is.

Normally when trying for big power on an Evo (for example), you upgrade to a 70+mm throttle as soon as you stroke to 2.2+L.

I can see that a 65mm throttle can hold back a built 3.5L motor. Need bigger throttle.

yeah, the blower I'm looking at getting will suck in 1.7L per rev vs the 0.87L per rev that the current one sucks...

I'm thinking 65mm (~33cm^2) is not going to cope with that very well. 72mm (~41cm^2) might be ok, but I'd prefer 80mm (~50cm^2). I just don't want to put all this time and effort into the blower and then be hampered by a TB.

cheers,
.wook

EDIT: I'm trying to find some air flow measurements for the stock TB... I need a max of 21M^3 per minute compared to the other blower which was 12.3M^3 per minute.

OK, some quick maths for those playing along at home...

Flow (F) = Velocity (V) x Area (A)
so V = F/A

for a 65mm ID TB
A = 33cm^2 = 0.0033m^2
F = 21m^3/minute

V = (21m^3/min) / 0.0033m^2 = 6363m/min = 106m/sec :shock:

that's pretty quick, and I doubt the intake will deal well with that...

for a 72mm ID TB
A = 0.00407m^2
F = 21m^3/min

V = (21m^3/min) / 0.00407m^2 = 5160m/minute = 86m/sec


for an 80mm ID TB
A = 0.0050m^2
F = 21m^3/min

V = (21m^3/min) / 0.0050m^2 = 4200m/minute = 70m/sec

so 72mm might do it, but 80mm will do it easily.


for reference, the current setup is as follows...

65mm ID TB
A = 33cm^2 = 0.0033m^2
F = 12.3m^3/minute

V = (12.3m^3/min) / 0.0033m^2 = 3727m/min = 62m/sec



cheers,
.wook

how did this go?

how did this go?

well... no one who had actually done this even posted in the thread. I'm still investigating. will talk to my head guy this week and see what he reckons.

PM Ego he might be able to help

the only comment I've seen from Ego on TBs is he doesn't know... I searched through his threads about the Mustang TB he has and he says "Don't Know" to every question.

I'm thinking Jason's VRX or EZY Boy or someone who has actually replaced the stock TB with an aftermarket one would be able to help...?

EZ boy hasn't replaced the standard one he just has a flowed one

fair enough, but he's messed around with them enough that he might be able to shed some light on how the ISC works and how it interacts with the TB.

I didn't get around to removing my TB on the weekend... too much other stuff going on.

Just a couple of numbers for NA race engines.

BTTC are limited to 60mm and make 310-315HP on 4 cylinders. With more cylinders there is less pulsing and flow potential increases.

Rolex Grand Am make 500-550HP with 80mm on 8 cylinders, but are limited more by small cams and 7000rpm rev limit.

In my experience I'd expect some flow restriction with a 6 cyl over about 350-360HP on a 65mm TB.

Cheers,
Alan

thanks Alan... that's the sort of thing I've been looking for.

the expected output is going to be 250+kw atw, which would be 330+hp atw, but being an FI engine the flow won't be as variable as NA engines.

--------------------------------------------------------------------------------

OK, some quick maths for those playing along at home...

Flow (F) = Velocity (V) x Area (A)
so V = F/A

for a 65mm ID TB
A = 33cm^2 = 0.0033m^2
F = 21m^3/minute

V = (21m^3/min) / 0.0033m^2 = 6363m/min = 106m/sec

that's pretty quick, and I doubt the intake will deal well with that...

for a 72mm ID TB
A = 0.00407m^2
F = 21m^3/min

V = (21m^3/min) / 0.00407m^2 = 5160m/minute = 86m/sec


for an 80mm ID TB
A = 0.0050m^2
F = 21m^3/min

V = (21m^3/min) / 0.0050m^2 = 4200m/minute = 70m/sec

so 72mm might do it, but 80mm will do it easily.


for reference, the current setup is as follows...

65mm ID TB
A = 33cm^2 = 0.0033m^2
F = 12.3m^3/minute

V = (12.3m^3/min) / 0.0033m^2 = 3727m/min = 62m/sec



cheers,
.wook


these calculations are valid, however, you need to change your units from m/sec to m/min!
edit: silly me.

these calculations are valid, however, you need to change your units from m/sec to m/min!

read it again... they are in m/min then m/sec.

o sorry, my bad, haha

also, another thing to concider is that the air in the center of the pipe would be moving faster due to the fact that the air closer to the pipes walls would be moving slower due to the friction between the air and the pipe.

Wookie, PM Levi.
He had a 75mm TB on his magna that used the stock ISC and TPS switches. From what he told me, its the same TB as the ones that rip off place in WA is selling.

ok, after further calculation, your calculations are fundamentally flawed because you are assuming that after it gets through the blower, it will still be at 1atm (101.3kPa) of pressure. on the contrary, i am guessing it will be at a minimum of 6psi (142.7kPa REAL pressure), once this is factored in, the FR is closer to 15cubic meters per second as opposed to 21. (because as pressure -> infinity, FR -> 0)

plugging this new number into your formulas,

at 6psi, flow rate = (approx) 15 cubic meters per second

f=VxA

V = 15 cubic meters / .0033 m squared

= 75 meters per second. (this is aroud 25% slower)

at 8 psi, flow rate equals (approx) 13.5 meters per second

which works out to be 68 meters per second

also,

what size inlet and outlets does the blower have?

(edit, the volume to pressure formula i used is not 100% accurate for flow rates, however it gives a good estimate, i dont feel like deriving tonight.)

I don't think my calcs are flawed... before it hits the blower the pressure doesn't change. the TB is before the blower, thus all air flowing through it will be at 1 atmosphere.

post blower of course the flow will be affected by the increase in pressure.

the inlet of the blower is a figure 8, approx 160mm tall and 100mm wide.

the outlet is triangular and I'm not sure of the measurements... see diagram below.

cheers,
.wook

http://img17.imageshack.us/img17/110/mx417.jpg

Wookie, PM Levi.
He had a 75mm TB on his magna that used the stock ISC and TPS switches. From what he told me, its the same TB as the ones that rip off place in WA is selling.

thanks Jason!