Switching back to stock tb from 78mm bbk... - Forums at Modded Mustangs
 
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post #1 of 11 Old April 3rd, 2015, 06:55 PM Thread Starter
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Switching back to stock tb from 78mm bbk...

I am switching back to my stock tb, I have had nothing but problems with the 78mm bbk since i put it on.... I think i am actually moving way to much air into the engine being i have no other mods than the normal ones... It idles horrible, and prior to installing this tb two years ago it never had a issue. I do remember seeing articles after my purchase saying these tb's only do well with heavily modded engines, blowers, heads, etc. Thoughts on am i making the right choice?

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post #2 of 11 Old April 3rd, 2015, 07:47 PM
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I have the same tb, and like you,took it off because I saw no difference, idled funny, and some other hiccups, but I installed it back, the bad idling and other issues were non related to the tb, check you iac valve, plenum gasket, check for stuck open egr valve.

My car works fine with that tb and is pretty much stock, I know it's overkill but I do plan on going FI so, it will be useful.



1999 Mustang GT
Drop in K&N Filter
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O/R Pypes X pipe
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BBK 78mm TB
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post #3 of 11 Old April 3rd, 2015, 07:52 PM
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I have the BBK 78mm TB combo, Adjust the screw on the TB Eagle2000gt (i think that is his name) Shared the link on how to do it and it fixed my problems. Who did your tune also?
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post #4 of 11 Old April 3rd, 2015, 08:32 PM
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:word: to condor, I did had to adjust the idle stop screw.



1999 Mustang GT
Drop in K&N Filter
Shift Kit
O/R Pypes X pipe
Glasspacks
BBK 78mm TB
CC plates
Ford Racing lowering springs
Big Transmission cooler
03 Cobra Rims
6000k 55w HIDs

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post #5 of 11 Old April 3rd, 2015, 08:39 PM
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Got the same tb here. I honestly think it's a really nice piece. Haven't had one problem out of it. Like condor said you may have to adjust the set screw but only adjust it very small increments at a time.



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post #6 of 11 Old April 4th, 2015, 06:21 PM
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TB's only gain on heavily modified engines. In other words, the stock tb on a stock engine is not a restriction, therefore therefore a bigger TB will not "cause too much air" to flow into the engine. (some idiot AM rep posted that once)

Maybe you have a vacuum leak?

FWIW all I have is full exhaust and Accufab 75mm TB/Plentum and my car idles like stock with zero issues.
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post #7 of 11 Old April 4th, 2015, 07:40 PM
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I had one when I was n/a and had no issues but a slight stick at first. That went away though and never had an issue after that. Certainly no idle issues.
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post #8 of 11 Old April 4th, 2015, 07:56 PM
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my stock TB took me to low-11's and 500+ HP. I doubt an aftermarket TB will do much, especially on a NA engine.

T-trimmed black 99 GT
Cobra SB, 44cc TF heads, HP292 cams, RR intake, T56
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post #9 of 11 Old April 4th, 2015, 09:06 PM
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Quote:
Originally Posted by metalman302 View Post
TB's only gain on heavily modified engines. In other words, the stock tb on a stock engine is not a restriction, therefore therefore a bigger TB will not "cause too much air" to flow into the engine. (some idiot AM rep posted that once)
I'm pretty sure that is sarcasm. If so then you are correct. If you go to the link and click on TB/Plenum/MAF/IAC and then on Accufab flow data you will see the test data. At 6500 rpm our motors need around 475 cfm of air. The stock TB/Plenum maxes out around 372 cfm (1999-2000) or 388 cfm (2001-2004) of air which is around 100 cfm short of what is needed. So the stock combo does restrict performance.

The greatest restriction though is not the 65 mm stock TB. It's the plenum. Putting any aftermarket 70/75 mm TB on the stock plenum will fall short of what is needed. That combo will max out around 414-412 cfm. Greater gains are achieved from putting the stock TB on an aftermarket plenum. But all such combos still fall short of what is needed. The Accufab plenum comes closest with 470 cfm (but its their test data).

I have heard it said that the 75 mm TB provides too much air. It's the old velocity vs. volume argument. This is not true on our motors. If you look at the data the aftermarket plenum (while providing enough air) is still the restriction. For most aftermarket plenums there is only a couple of cfm difference between the 70 and 75 mm TBs. So a 75 mm TB does not hurt engine performance.

The only plenum that needs a 75 mm TB is C&L. It only flows 470 cfm with the 70 mm TB.

Link: PaladinMicro

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Quote:
Originally Posted by TonyG View Post
my stock TB took me to low-11's and 500+ HP. I doubt an aftermarket TB will do much, especially on a NA engine.
OK, but you force fed it with pressurized air. That is not the same thing as running it on an NA engine.

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post #10 of 11 Old April 4th, 2015, 11:27 PM
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Atmospheric air is also "pressurized air," so the physics in the two cases is not that different. It's just that the pressure delta is larger in the FI case. Anyway, the main point is that there is little or no gain with an aftermarket TB.

T-trimmed black 99 GT
Cobra SB, 44cc TF heads, HP292 cams, RR intake, T56
21 psi @ 7k , 10.327/136.14/1.417
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post #11 of 11 Old April 5th, 2015, 03:15 AM
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I've read that the gain is around 3 rwhp (a college student doing testing for a class). Others have said 5 rwhp. Either one is about right considering that a tb/plenum doesn't cost very much. Depending upon the approach mods can cost $60-100 per horsepower.

ProCharger P-1SC, 9 psi, STD 396/383; Uncorrected 388/375; SAE 383/370.
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