Back to back fox versus 94-95 TB dyno results inside!!!
- Thread starter Killercanary
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Black95GTS
Active Member
The test is much appreciated Paul, there is no doubt. I can see how people may conclude that the Fox style is better, but you also have to see that a cloud of doubt is cast by the difference in throttle body sizes.
I don't think anyone meant to say what you did is useless. Throttle body size is a hotly debated topic (why, I don't know) that is discussed constantly, so its only natural that things would be examined closely. If for nothing else, the conversation that posting your results generated is worth it.
On a completely unrelated note, at what pressure are you driving those poor 24s and what duty cycle are they running? I'm guessing around 50PSI and near 95 percent.
Adam
I don't think anyone meant to say what you did is useless. Throttle body size is a hotly debated topic (why, I don't know) that is discussed constantly, so its only natural that things would be examined closely. If for nothing else, the conversation that posting your results generated is worth it.
On a completely unrelated note, at what pressure are you driving those poor 24s and what duty cycle are they running? I'm guessing around 50PSI and near 95 percent.
Adam
Black95GTS
Active Member
You better believe itout of all the mag articles and countless threads I've read over the years YOUR info/data is the best and most accurate I've seen regarding this subject on our cars. Your data proved beyond a shadow of a doubt for me that G. Klass's (Accufab) article is absolutely right on the money on how to properly choose a TB ( again..CFM not the size of the hole).
With all due respect, you can't solve an equation with two variables.
Adam
BlackVert
15 Year Member
You better believe it
I am glad someone pays attention like you.
Not all TB's flow the same, due to a few solid reason (design, shaft/blade thickness, etc.)
An engine is just a large air pump and those TB's help delegate the pumping. If an engine pumps 400 cubic feet of air, and a TB will flow 800 cubic feet of air during the same time frame, I think it is pretty cut and dry on whether a TB can keep up or not.
George knows his stuff and they have did more testing then I will ever do in a lifetime. There is a reason why they only go up to 105 mm in their sizing.
I was reading an article somewhere the other day, where a 1800-2000 HP drag car (Livernois maybe?) was running a 100 mm TB on it.
greenlantern
Member
Paul I don't knock your test I'm glad you did it. It sparked one of the best throttle body debates I've read to date. Some of us are bitching because we finally realize that we need to go spend some more money.
Throwing your opinions around to bounce of others helps eveyone to make smart decisions about there own setups.
Throwing your opinions around to bounce of others helps eveyone to make smart decisions about there own setups. 75 mm opening, but it necks down to around 65 mm a couple inches in.
This is why just a dremel for just the opening does not work on the majority of intakes.
His stock elbow was even ported, which I find interesting.
I wonder if anyone has ever measured the volume and length of the stock, TFS, and Edelbrock elbow adapters?
I hope noone gets me wrong here. A large throttle body is not going to hurt "bottom end" and is not like a carb (needing a pressure drop across the fuel bowl area to pull fuel out).
I just can not help but
when I hear or see someone post that they need a minimum of a 70-75-90 mm TB on a 7k or less 302.
I just found out the local guy actually saw similar results to mine once he pulled his graphs out He saw an improvement of ~10rwhp and 6ftlbs of TQ. He went from 325rwhp/353 to 335rwhp/359rwtq. I'll work on getting the graphs. Even in light of this, I'm dying to do the test again with a 94-95 75mm TB and comparing it to the 75mm fox. I'll post more details later.
Black95GTS
Active Member
Paul's friend did his tests on different days and different dynos. I feel that that somewhat disqualifies his data. Thats what makes Paul's test so cool, he actually went ahead and did something that always gets talked about but never actually gets done!
I'm still maintaining that:
Paul made more power because he went with a bigger throttle body. Based on what we see here, you can't say I'm wrong.
HOWEVER
If 5SpdGT (sorry I forget your real name,Dave?) said:
Paul made more power because he went with a Fox setup regardless of throttle body size. I couldn't prove him wrong either.
Air flow is not the deciding factor in producing horse power. Keep in mind that using a larger throttle body before the intake creates a larger pressure differential then a smaller throttle body, so that when the diameter inside the intake "necks down" greater velocity is produced, which results in an air charge of higher energy and a more even cylinder fill: more horsepower.
This is why (I believe) the Holley intake mentioned above necks down on purpose to create higher velocity before the air hits the cylinders.
A word on Volumetric Efficiency (VE): How VE is measured is critical to understanding this. VE is the Density of Air in the Intake Manifold / Density of Air in the Cylinder * 100 = VE%. Notice this has nothing to do with the flow rate of the throttle body before air enters the intake manifold. Having 100% VE would mean that the air density in the intake manifold is the same as the density in the cylinder. This is very difficult in a naturally aspirated engine! Especially in all 8 cylinders. Super and turbo charged engines have higher then 100 percent because they are actively pressurizing the air and stuffing it into the manifold before the cylinders can keep up with it. BOOST is a measurement of how much extra pressure is inside the intake manifold when this occurs. The more efficient the engine, the less BOOST is created by the power adder because the cylinders can get rid of that extra pressure faster. It can also be done naturally aspirated but it takes some tricky valve timing, exhaust scavenging, and you will be basically pulling no vacuum when your not in the RPM range over 100 percent VE so it wouldn't be street drive-able.
CFM is a critical measurement of engine components but its not the only one. Just something for you all to think about. And yes, I am a huge nerd.
Adam
PAUL...I didnt look at these debates the way you did...the way I see it, it is a good chance for someone that is just learning to read through and take into acct some of the factors being mentioned. If you go vack through 1 by 1, I think there are only 1 or 2 posts that are kind of "disrepectful". The rest are just points of view. If you posted those results and said "THIS IS BETTER SINCE...." then I could see.. All you did was say "here's what I did, and here's what I got"
RC
RC
There may have been a few HP difference, but to me it appears that the design is what caused it, as he switched both the restrictive elbow and the 65 mm TB out.
75 mm area is 6.84" (squared), while the 65 mm area is 5.14" (squared). That is a 33% difference in area. So do you think he needed every bit of that 33% more area. Looking at the power difference between each, I can safely say, no.
David, Dave, same thing...(good memory)
I believe it is a slight combination, but more or less, 70/30 (Fox design/TB).
I used to think this way.
You do not need the velocity, as the area shrinks. It enters into a plenum and slows greatly before entering the individual runners. A plenum is full of "slow air" which creates more pressure, which in turns, helps the ramming effect!
Think Bernoulli's Principle here Adam.
Dynamic Air (Fast) = Less Pressure
Static Air (Slow) = More Pressure
A few examples of the principle at work:
A. Airplane lifting off the ground
a. An aircraft wing is curved on top, but flat on bottom. As air passed over the the top and bottom wing, air has to travel faster on the top part of the wing, but cover the same distance. This causes the air to have to move faster, which reduces pressure. The pressure will then be greater on the bottom, therefore, it causes the airplane to begin to lift.
B. Window shades "sucking out" during windy days
b. As wind moves faster outside of the windows, this causes less pressure. The static air inside begins to push outside. It appears that the window shades are being "sucked out", but they are really being pushed out by the greater (slower air) pressure inside.
C. Closing a door going down the highway.
c. Ever wonder why it is so hard to close a door going down the highway at 50 MPH? It should be easy, right? Nope, because the air blowing past the door reduces pressure on the outside of the door, and therefore creates a large pressure differential (greater) on the inside, which causes the door to be hard to shut.
I hope a couple of these examples help out.
I do not see it this way. This would interfer with the plenums job. I believe it is because it leaves you room to grow with, by keeping the throttle body runner area on the smaller side.
NASCAR runs in the 125% VE range. That is with 358 cubic inches (4.185" x 3.253"). That is why they put out ~ 850 HP.
Exhaust scavenging is huge in getting high VE numbers. You are correct!
True, true.
Here is where I believe many false assumptions occur. There seems to be a trend with the higher HP/TQ cars per cube running larger TB's. For the most part this is very true!
However, here is where the issue gets twisted. The high HP/TQ cars per cube have large TB's because they usually package their goals around reaching these numbers and care less and less with your typical street guy. They make everything "big" in order to get that number.
This does not mean the large TB is needed, it is just part of the thinking and package. This sticks in the minds of many, and the typical post hoc fallacy.
"Oh, since he has a 90 mm TB on that 400 RWHP 347, it must be needed"
They forget to look at the rest of the package and goals of the end user.
As usual Adam, I like your thoughts as you actually try to explain your reasoning, while others just post up whatever the flavor of the month is.
There was a guy on HC50, that went by flyin2jz (sp?), with a more drag oriented 302 that was running the low 90 (91-94) MPH range in the 1/8 mile. Pretty strong for his combination.
He had a 75 mm TB (first TB) and swapped to a 90 mm TB (second TB), and gained zilch!
He listened to some "big wigs" too.
That is for you track guys.
He had a 75 mm TB (first TB) and swapped to a 90 mm TB (second TB), and gained zilch!
He listened to some "big wigs" too.
That is for you track guys.
An FRPP throttle body will not flow as well as an Accufab of the same size.
Stock 5.0L 60 MM - 526 CFM
SVO 65 MM - 540 CFM
Accufab:
65 MM - 664 CFM
70 MM - 787 CFM
70 MM - 896 CFM (Race version)
75 MM - 924 CFM
75 MM - 1045 CFM (Race version)
80 MM - 1142 CFM
85 MM - 1322 CFM
90 MM - 1369 CFM
105 MM - 1550 CFM
Holley:
65 MM - 750 CFM*
70 MM - 790 CFM*
75 MM - 840 CFM*
80 MM - 892 CFM*
*Information given by Tech Rep.
BBK:
70 MM - 726 CFM
Here's the local guy's dyno graphs with a 65mm TB and a 75mm TB. His combo was different than I posted above when he dyno'd the car, at the time these dynos were done it was:
10.5:1 NA 347, AFR 185s, TF stage 2 Cam, TF R series intake, 42 lb inj & 90mm LMAF, 75mm BBK Throttle Body, BBK shorties, Bassani cat back, 255 LPH fuel pump, Stock Ford distributor and ignition, Tremec 3550, Centerforce clutch, FRPP safety bellhouse, FRPP aluminum driveshaft, 3.73 gears, Steeda suspension
Remember, these test were done on two different dynos and on two different days.
65mm TB:
75mm TB:
10.5:1 NA 347, AFR 185s, TF stage 2 Cam, TF R series intake, 42 lb inj & 90mm LMAF, 75mm BBK Throttle Body, BBK shorties, Bassani cat back, 255 LPH fuel pump, Stock Ford distributor and ignition, Tremec 3550, Centerforce clutch, FRPP safety bellhouse, FRPP aluminum driveshaft, 3.73 gears, Steeda suspension
Remember, these test were done on two different dynos and on two different days.
65mm TB:
75mm TB:
Thanks for that!
Random question:
Do you know what the elevation is like at each?
You gained 9 RWHP and you started out with 40 more RWHP, and you removed the Sn-95 elbow and changed TB size, not just TB size. The different day/dyno may actually have been an issue as Adam and you stated.
Random question:
Do you know what the elevation is like at each?
You gained 9 RWHP and you started out with 40 more RWHP, and you removed the Sn-95 elbow and changed TB size, not just TB size. The different day/dyno may actually have been an issue as Adam and you stated.
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