Throttle Bodies... Come hither JT.

[gasketmaster]

Quote:

Originally Posted by Shel-Game A 46mm TB may flow ~300CFM at 10in vacuum. But it will flow a lot more than that at a larger pressure differential (up to the point that it chokes).

Thank you!

If you put 15 psi to a Holley 650 it's no longer a 650........that's for sure

[gasketmaster]

Quote:

Originally Posted by TrboVan I love Real World examples. Thanks Terry,.

Well unfortunately I'm no engineer but I lean over a whole bunch of fenders

Here are some more real world examples of what I've seen:

3500 lb. GN 10.92 @ 122 with the stock 60mm TB

3550 lb. GN 9.90 @ 136 with a 62mm TB

3500 lb. GN 8.68 @ 155 with a 70mm TB

3300 lb. Mustang 9.17 @ 151 with a 75mm TB

My 3350 lb. minivan 12.69 @ 107 with the stock TB

Now on the larger side two cars that I tune have 90mm TB's........what a nightmare they are for tip-in hesitation
Just creeping into the throttle with one of these Folger's coffee cans is like going from idle to WOT with a 65mm TB but you've only moved the pedal 1/4".........LOL!!!

[Shadow]

I only see restriction in the form of CFM, not in PSI.

[gasketmaster]

Quote:

Originally Posted by Shadow I only see restriction in the form of CFM, not in PSI.

Yes but the CFM of a given TB changes drastically as you add PSI similar to tubing

[Frank]

Quote:

Originally Posted by TrboVan I love Real World examples. Thanks Terry,.

Real World examples are only useful if you have the complete picture... why dont you say what is really on your mind, like: "Get the hell out of here with your desktop engineering?" Fine go ahead. hehehehe

The information posted is not wrong, but I have not stated otherwise. There is no fault to find because I am not trying to start a revolution by saying everyone *needs* to upgrade. I am only trying to provide some numbers to support a possible cheap upgrade for people because I feel that it will work.




Frank

[Frank]

Quote:

Originally Posted by gasketmaster Yes but the CFM of a given TB changes drastically as you add PSI similar to tubing

Yep and by adding more PSI to maintain that CFM (since that and fuel make power), you are working your turbo more then needed. This is seen by higher temperatures, typically running outside the optimum range of the turbo, and requiring a higher shaft speed. The higher shaft speed means that your turbine isnt as efficent and you will have more exhaust backpressure.

Everything effects everything.


Frank

[B.A.P.]

Quote:

Originally Posted by Shel-Game The only way a larger TB would help is if it is the restriction at WOT.

Didn't I say that its always down to the least restriction?

[B.A.P.]

Quote:

Originally Posted by Frank Cutting off the elbow on your intake, weld a larger pipe on, and trying out a 65mm throttlebody. Frank

I could do that... was rather planning on making a whole intake tho... How about these steps?:

1 - make a new intake for new ??mm TB
2 - dyno car as it sits now with current intake, 52mm TB & current calibration
3 - dyno car with new intake, 52mm TB & current calibration
4 - dyno car with new intake, ??mm TB & current calibration
5 - dyno car with new intake, ??mm TB & new I/C & current calibration
6 - dyno car with new intake, ??mm TB & new I/C & new calibrationtion

EDIT: BTW, I have never dynoed any of my cars...

[turbovanman]

Quote:

Originally Posted by GLHNSLHT2 Because back in the day Gary D said it wasn't needed. There were also reports of MPG dropping off 3-4MPG when running a 52mm TB. I know of one car that this isn't true on. Anyone else? TD'ers are just afraid of change in general as well.

I've done back to back vs 46-52mm, identical fuel economy and the larger t/b picked up 5 whp on the dyno. I changed it on the dyno.
Very mild ported head, back cut valves, 2.5L with stock T1 cam, stock manifold and TIII turbo. I noticed the larger t/b was smoother.
With my new engine, I am going to put the 46mm back on and see what happens,

[B.A.P.]

Quote:

Originally Posted by turbovanman I've done back to back vs 46-52mm, identical fuel economy and the larger t/b picked up 5 whp on the dyno. I changed it on the dyno. Very mild ported head, back cut valves, 2.5L with stock T1 cam, stock manifold and TIII turbo. I noticed the larger t/b was smoother. With my new engine, I am going to put the 46mm back on and see what happens,

We're assuming you opened up the mouth of the intake to clear the 52mm throttle blade? I made a custom 1/8" spacer on my shadow to not have to cut the intake, works decent...

Did you take the throttle cam off the 46 and put it in the 52? the 46 cam is more agressive, so if you put it on the 52 you get better throttle response.

[Frank]

Quote:

Originally Posted by BadAssPerformance 1 - make a new intake for new 70mm TB 2 - dyno car as it sits now with current intake, 52mm TB & current calibration 3 - dyno car with new intake, 52mm TB & current calibration 4 - dyno car with new intake, 70mm TB & current calibration 5 - dyno car with new intake, 70mm TB & new I/C & current calibration 6 - dyno car with new intake, 70mm TB & new I/C & new calibrationtion

Thats what I would do... except it might be worth your time to buy Wallace's & Andre's two piece custom intake fitted for a 70mm. May save some significant time. I wish I had a picture... its nice.


Frank

[turbovanman]

Quote:

Originally Posted by BadAssPerformance We're assuming you opened up the mouth of the intake to clear the 52mm throttle blade? I made a custom 1/8" spacer on my shadow to not have to cut the intake, works decent... Did you take the throttle cam off the 46 and put it in the 52? the 46 cam is more agressive, so if you put it on the 52 you get better throttle response.

I swapped over the arm/cam as the 3.8 one I got didn't have the hole for the kickdown cable.
Of course the plenum was opened, lol! It was a 1 piece intake BTW.

I will report back on throttle repsonse and fuel economy when I swap back over to the smaller one. Right now, I average 14mpg with a stock T1 cal and Paul's 3 bar cal.

[B.A.P.]

Quote:

Originally Posted by Frank Thats what I would do... except it might be worth your time to buy Wallace's & Andre's two piece custom intake fitted for a 70mm. May save some significant time. I wish I had a picture... its nice. Frank

I'd like to see it and hear a price too, but you know I like to make my own stuff...

EDIT: i just noticed you replaced ??mm with 70mm... how'd you pick out that size?

[B.A.P.]

Quote:

Originally Posted by turbovanman I swapped over the arm/cam as the 3.8 one I got didn't have the hole for the kickdown cable. Of course the plenum was opened, lol! It was a 1 piece intake BTW. I will report back on throttle repsonse and fuel economy when I swap back over to the smaller one. Right now, I average 14mpg with a stock T1 cal and Paul's 3 bar cal.

14mpg? not too bad

[Putter]

I'm getting confused by some of this:

Air speed is dependant of absolute pressure. If 300ft/sec is a wanted maxium of a naturally aspirated engine, thats roughly 27% the sound of speed.

So if we increase our air density to 29.4psi absolute, wouldn't a respectable airspeed be 600ft/sec as the speed of sound has roughly doubled? (I'm assuming speed of sound is directly related to air density, someone correct me if I'm wrong)

So if we figure this same sized orifice with a 10" vac drop from 29.4absolute vs 10" vac drop from 14.7 absoulute, we have done nothing more than increase the density through the orifice, therefore increasing its flow capacity at the same pressure drop.

Now the biggest factor in this would the pressure vs density. I doubt air at 29.4psi is half as big as 14.7, its probably more around 2/3rds as big.

So, what I'm curious to know:

Is air pressure vs volume linear or not (I'm assuming it isn't)
Is speed of air linear to air pressure also? (I'm thinking it is?)

Again I'm not trying to argue to this point either way, I would just like to have a more educated understanding of this.

The entire point of turbocharging is to increase air density so more air flows through the same size hole, which is why high powered N/A engines make higher powered turbo engines. Someone with alot of time/money ought to build an N/A 2.2 using turbo intake and a regular exhaust manifold and go to town trying to get some more power out of it. My N/A 2.2 only made 82whp @4000rpms...so no matter how much boost you run, its still going to suck.