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Posted by: Mueller Nov 3 2003, 12:42 AM

Anyone ever do back to back testing with stock and then a bore'd out throttle body??

stock dia: 45.10mm

average overbore diameter???

I'm guessing 50mm, it looks like I could bore mine out to 53.50mm...hmmmm

motor to have higher than stock compression, custom R.A.T. cam and Megasquirt......

Posted by: fiid Nov 3 2003, 12:45 AM

Aye - what was up with the Engel cam?

Rich @HPH sells overbored throttle bodies and seems to think they are a good idea. About as high subjective praise as you can get.

Fiid.

Posted by: Brad Roberts Nov 3 2003, 12:46 AM

Yep. Mike Harris and I tested it on his HPH built BP 2.0 last year.

Worthless on a stock engine with racing header.

I could see how it would be needed for a engine that requires MORE air.

This is why I have Andy working on the actual engineering flow numbers for the stock intake.

I want to know EXACTLY what numbers the factory had to determine the stock intake manifold and stock throttle body.


B

Posted by: Brad Roberts Nov 3 2003, 12:47 AM

Mike.. I may want the Engle FK cam.


B

Posted by: Mueller Nov 3 2003, 12:54 AM

Hey b,

the cam is just sitting collecting dust

do you have any extra t/b's?

I could bore 'em out to a few different diameters if you want for testing, I also want to clean up the shaft and the trottle plate, lots of resistance with the current setup....

I got those "iris" throttle body parts


Attached image(s)

Posted by: Brad Roberts Nov 3 2003, 01:22 AM

I want drawings.. not throttle bodies.

I'm tired of "experimenting" or using parts that are "supposed" to work. I want real numbers and real answer for this crap. Not guesses.


B

Posted by: Britain Smith Nov 3 2003, 01:34 AM

Hey Brad...we also have the elgin cam sitting up there that would work well in NA trim...

-Britain

Posted by: Mark Henry Nov 3 2003, 08:10 AM

Brad, I love to see those numbers when you done.

I have no swap experience, but in the little seat time that I had, my SDS 2.0 with an old C-25 cam and 42mmX38mm valves was rockin. Just got a lot of tweeking still to do.

But then anything would be an improvement over my old "snorting" 75hp 1.8 Ljet

Posted by: r_towle Nov 11 2003, 03:47 PM

Whats the progress on this topic?
I would really like to see these numbers.

Rich

Posted by: r_towle Nov 11 2003, 03:50 PM

Sorry for the questions, but Who is HPH???
Could we add them to the vendor area??

Rich

Posted by: seanery Nov 11 2003, 03:53 PM

HPH is Rich Bontempi's company, High Performance House

http://www.highperformancehouse.com

Posted by: SirAndy Nov 11 2003, 04:40 PM

Posted by: Jake Raby Nov 11 2003, 07:08 PM

When I tried it we lost HP.

Posted by: r_towle Nov 11 2003, 07:50 PM

Im thinking 2270 with a bigger throttle body and MPS/Head Temp resisitor and fuel pressure tuning.

Posted by: Jake Raby Nov 11 2003, 08:32 PM

it'll never feed it.

Tried it tons of times!

Posted by: r_towle Nov 11 2003, 08:37 PM

how big have you gone Jake?????

DJet driven???

Rich

Posted by: Jake Raby Nov 11 2003, 08:43 PM

All the ones that have stayed D Jet have been 2056 or smaller....

Posted by: fiid Nov 11 2003, 11:17 PM

I bet you could get a megasquirted 2270 to run really nicely, and that might benefit from the larger throttle body. I wouldn't get too far into tuning the D-jet -

Posted by: SirAndy Nov 11 2003, 11:35 PM

I bet you could get a megasquirted 2270 to run really nicely, and that might benefit from the larger throttle body. I wouldn't get too far into tuning the D-jet -

Posted by: SirAndy Nov 18 2003, 12:10 AM

ok, back to this issue. i have never seen a aftermarket "overbore" throttlebody but brad tells me they just use a stock TB and bore it out to a larger diameter.

running the numbers on the stock TB and looking at the shape of the original TB, it becomes quite obvious why this "modification" is not only NOT giving you more HP, fact is it will decrease your HP!

and here is why:

CFM (cubic feet per minute) is the amount of air your engine will "pump" through at a certain rpm. using the stock 2.0L (us-spec) engine as a reference, that would be ~170 CFM @ 4900 rpm (or 4829 Liter/min). this is the theoretical max if your engine had a VE (volumetric efficiency) of 100%. normal street engines have a VE of around 85%, meaning the 2.0L actually only pumps about 128 cfm. this is due to a lot of factors, like friction and turbulences and restrictive air intake and exhaust. (as well as valve size, of course).

now, CFM is calculated as

Area (in sqft) * Feet per Minute (velocity), where Area is the diameter of your intake, in our case, the throttle body and "Feet per Minute" is the speed (velocity) of the Air.

sooo, overboring the stock TB will give us a bigger Area, thus, we get more CFM, right?
Wrong!
the stock TB has a special shape that introduces a "venturi" effect, which increases the velocity of the air going through the intake which results in a actual increase in CFM.
if this shape is "bored out" to gain a bigger diameter, you'll loose the venturi effect, and at best, you'll end up with no gain, but most likley, you will even loose a few CFM.

sooooo, what we need now is someone who has access to a flow-bench so we can confirm (or not) the theoretical numbers we have and come up with the correct size Throttle Body and intake runners and valves-sizes and exhaust system for various T4 engine-combos. anyone?

Andy

Posted by: KenH Nov 18 2003, 12:48 AM

The TB opening for a 2.0 is 45mm while the ID of the runners to the heads is only 35mm.

Ken

Posted by: Jeff Bowlsby Nov 18 2003, 01:13 AM

I have a Chuxter-bored 2.0 TB to 50mm to lend for testing....

Posted by: SirAndy Nov 18 2003, 11:50 AM