jomo_eng

Please notice that Fred, "Injuneer" said the 52mm TB would have done him just fine. He is running a 275 shot of nitrous and is producing Horse Power: 762@6000RPMs, Torque: 754@5200RPMs. We are comparing a car that is almost stock in my opinion to a car that produces over 750 hp. According to almost all the "experts" of this site and others. The 52mm TB is not needed until you go to a 383 or stroked motor. And if the 48mm TB hurts the air intake so much why do they use it on the Chevy 502 bb motor.

I have read numerous articles on this subject and the consensus is your money is better spent elsewere.

I personally think you will see a 2 or 3 HP increase at peak. Considering an air foil is worth 1.5 to 2hp i don't see the point. If your up to paying roughly 75 to 100 per HP go for it.
Just my .02.

Later,
JoMo

96z

TheHeadFl brings up another good point. How do you plan on getting more air to make more power if the head flow potential doesnt change? LT1 heads stall at .550 lift. He could have a cam with .700 lift and it doesnt mean jack since the heads cant flow anymore.

Explain to me how you see more power can be made with all this extra air when the head flow hits a wall?? Where's all this extra air that the motor needs going to go?

GreenbeanZ28

52 MM on my stock *** car picked up .2 and 2 mph in the 1/4. I say get the bigger TB. If you want to go faster...if you want to remain slow, use you stock TB.

mtxpert

Stock motor Impala SS
I picked up .2 from 52MM TB and another .2 from stepping up to a 58MM with stock valve springs/RR's etc. I then changed valve springs and RR's and picked up another .3

I run 14.0's on motor with 58MM, electric water pump, 1.6 RR's, valve springs, headers - no cats and dynomax 2.5" exhaust. Bryan Herter programming with modified WOT tables from WBO2/dyno tuning.
This is in Phoenix at 1300' elevation and 60+ degree weather.

275HP and 335TQ to the rear wheels with this combo.

Mike

EddieP

I'd be interested to know what the real deal is behind T/B sizing.... My gut tells me that the larger 52 or 58mm T/B could only help, as long as the tuning is there, but who knows.

Anyone else notice that the stock LS1 T/B has a larger cross-section than an aftermarket 52mm LT1 T/B?

Mindgame

These numbers according to TPIS:

48mm, 668 cfm
52mm, 790 cfm
58mm, 1000 cfm

Doesn't say at what pressure drop they flowed them at but I'd assume 1.5" of mercury or 20.4" H2O, since that seems to be industry standard.

Just to make a point, lets go back to the engine airflow equation....
cfm=(rpm*cid)/(2*1728)
1728 is the number of cubic inches in a cubic foot, but it's easier just to remember 3456 (2*1728).
So lets look at a theoretical example..... we have a 350 ci engine reving to 6,300 rpm and based on the formula, an engine air consumption of 638 cfm. We need to adjust this number based on the actual volumetric efficiency of the engine, which I'd assume is less than 90% depending on the caliber of the engine build, but we'll use 90 anyways. So our new air consumption is 638*.9 or 574 cfm.
Something I'd keep in mind before we get going on this..... you are going to see flow losses in the induction system after the throttle body and I've seen anywhere from no loss to 10-20% to friction. So, the intake manifold and port modifications are going to contribute in one way or another to the actual air consumption seen at each cylinder. That said, I'd add 10% back onto the corrected-for-volumetric-efficiency calculation, for 638 cfm. If you flow the intake and throttle body, you don't have to guess at the flow losses. Good thing to have done if you're trying to wrench every last hp out of an engine.

Ok, so we have our 638 cfm and we need to know velocity through the throttle bore. Remember, we are looking to find whether we'll see a loss or not and that's based on the velocity..... remember the .2-.3 mach numbers I mentioned in my last response?

Velocity=cfm/flow area

We have a 48mm tb, each bore is 48mm or 1.89", so we split the air demand between the two bores, hence (638/2).

Velocity=((638/2)/pi*.945^2)x(1/60)/(1/144)
Velocity = 274 cfm

"From mach .3-.2 we may see gains of 1-3% but anything from .2-.1 improvements are nil".... this coming from a gentleman who does nothing but develop endurances engine for a living. Safe to take his word on it.
Mach is the speed of sound, I think its generally assumed to be ~1200 feet/sec at the temperatures we're talking here.
So our 274 cfm falls in the middle of the scale, Mach .3-.2 or 360-240. We may yet see some gains with a larger throttle body but we'd most likely see an even bigger gain if we were closer to 360 feet/sec. Again, take this with a grain of salt... we may actually be seeing greater than 10% loss after the throttle body which would drive our velocity up some.

The theory is cool, it's fun to study and you don't need a degree in quantum physics to do the math. I'm a computer science guy who does a bit of independent study but I'm far from Isaac Newton. If I were writing a paper to convince someone, I wouldn't do it with the "I'm smarter than you approach", I do it just like this.

What Greenbean said holds even more weight with me because it's real world experience. He picked up .2 and that's a nice gain... especially if it was a consistent gain. Fun stuff.

-Mindgame

EddieP

I take it that this is just a simple a reference to the law of diminishing returns (i.e., a larger TB won't give an substantial gains after a certain point)?

95TA8280

Look at what happened top a simple question!

HM Murdock

Ego has not one thing to do with it. Physics and logic do.

I said, with a 52mm TB, properly programmed, either PCM or MAFT, will always make more high end power on a cammed car. Note the combination of phrases. Now we are into English grammar.

I know I am wrong on a lot of things.

I am a student. My major is Physics. I know physics.

I am always willing to admit when I am wrong. I admit it a lot.

I am not wrong on this. This is not an ego trip. This is fact.

If your heads can flow 140CFM per cylinder, that's 1120 CFM. (maximum)

The stock TB is not 1120CFM.

I obviously know that we are not getting max airflow into the heads, but anything that can helps, is good.

If people are reporting .2 in the 1/4 from a 52MM TB and programming, that's called "proof in the pudding"


The problem with people who put 52mm TB's on their car, and then do not gain much, if any, peak HP are 99 times out of 100 doing this without even a MAFT. The stock MAF controls fuel delivery. If it still thinks the stock amount of air is getting into the intake, it will run lean. Period. This is not egotripping, this is FACT.

Do the proper thing and upgrade the fuel delivery by MAFT or PCM tuning before saying a mod doesn't work.

And as for as this Physics stuff.

I do not assume I am smarter than anyone. just like ya'll should always assume that an engine builder is not the Know it all GOD of engines, flow rates, and Newtonian Physics. Even he said a .2 or .2 gain. And that's again. supporting the facts as I have presented them.


I think that if we ask all those out there who have a stock LT1 with a 52MM or even 58MM and programming or MAFT how much they gained the the 1/4 mile, all will respond in a drop in ET and maybe even a gain in trap speed. I never said it will increase peak power. I don't care about peak power. That's for dyno queens. My frustration in those posts was due to having to explain that the ONLY thing horsepower is is a measure of Torque at a given RPM. I had to say it several times. I hate when people do that. I always will read every thread just to make sure I don't say the same thing that was dispelled without a doubt earlier in the thread. I apologize if I came off preachy, or egotistical. Those who know me know I am neither. But I know physics.

A gain of .1-.2 is still a damn gain. The only argument I made was there will be a gain in ET. Not peak power. ET. That was the only argument I was making. I tried to make it as simple as possible. I will take every .1 or .2 I can get. If you don't want them, fine. Then don't be surprised when my cammed Z beats your H/C LT1.

You have to lay the ground work. A TB is a piece of groundwork. By itself, it is not great. I would never recommend it to someone without a MAFT or PCM programming, and if you were already interested in one anyway, to go ahead and do it. It'll make a difference. .1 or .2 is still a gain. All I was saying is there would be a gain. I just had to say it a lot.

And you guys with your holier than thou attitudes, get off it. You don't fool me. You are just as egotistical as those you attack.

"All men are created equal" - a famous line in a famous document, that I live my life by.

There is always someone who knows more. There is always someone who knows less.

There is always someone faster, there is always someone slower.

I never said I was better, or faster, or smarter. In fact, my car is mostly stock. I know how to mod, though. I just got tired of people saying uninformed things that other people have said. I know of many mechanics who I would never trust near a crankshaft. Epsecially at speed shops. I make it my business to know as much as possible about what mods I am going to do.


You cannot actually believe that a 52 or 58mm tb is the problem. It is the lack of fuel to accompany the air.

<-----Will take every .1 or .2 in the 1/4 he can get.

Are you the same people who defeat AIR? Get a K&N filter? Get rid of EGR? Then how can you say that TB's don't help? Get the facts straight. Power is made by putting as much air and fuel through the engine as possible. That's not just physics, it is common sense.

If you still think I am wrong, do the actual research, not into proving me wrong, but do a search. Talk to people who have ACTUALLY DONE IT. I have, on my previous 95 Z28.

Gain of .2 and 2mph in the 1/8, with MAFT and 52MM TB over just MAFT.

EddieP

Hmm... you might want to consider that each cylinder's intake port has flow only when the intake valve is open... that might make your flow requirement much less than you thought.

HM Murdock

[quote]
Consider the fact that so many stock eliminator LT cars are breaking into the 10's these days.... then consider the fact that they are doing that with stock 48mm throttle bodies!
[/qoute]

Then they'd be faster with a 52mm and proper tuning.

I wouldn't want to waste the potential of my 10 second car by limiting something that was designed soley to be adequate. It is designed to pass emmisions, and make no more than 300HP, 340 Lbs ft.

Why restrict something you don't have to?

If there is no point in changing out the TB, then there is no point in changin the exhaust manifolds, or porting heads, or 4" intermediate pipes, or anything else that frees up the restrictive, soley designed for the minimum GM crap.

Why do you guys hate throttle bodies so much? Damn...There's a lot of TB hatin' in here.

A gain is a gain, pure and simple. And I'd like to remind people, all Ai have said is that with a 52mm and proper tuning, you will pick up some lower ET's.

That's it.

That was my whole point, except for explaining that HP is irrelevant, and that it is torque that matters.

Why keep it? Does it give you kickbacks? Is it doing certain "Presidential Intern" services?

Why do you guys not want to think that maybe a bigger TB is a good thing, with the proper adjustment to your fuel system, like PCM tuning and/or MAFT.

OK, to prove my point.

A 4" ID pipe flows more than a 3" ID pipe.
Undisputed Fact.

Yet most of you have 3" pipes coming out the muffler.

That's hypocrasy.


Or is it?

Individually, the flow rates of each cylinder head is not enough to warrant it. But if you have 8 cylinders, then you are capable of a LOT more airflow. Like 8 whole times.

If stock heads were really as restrictive as 100CFM flow rate, then they would still have the capability of 800CFM, total.

That is indisputable.

It's like running a 1.75 inch header pipe into a Y pipe 3" collector, and dumping into a 4" catback. Of course it works. Does it work as well as it possibly can? Nope. Sorry. You need more ID on the collector.


Now say the exact same analogy to the TB. All arguments go out the window.

If the stock TB flows 660CFM, then it is woefully inadequate. Your stock heads are capable of more. The ONLY reason that ANYONE has ever lost or not gained power with a 52mm TB is that the DID NOT REPROGRAM THE PCM(properly) OR GET A MAFT!!!!!!

Try it, then if you don't gain anything, I'll recant everything, and study history or something.

HM Murdock

Yeah, but I would rather have a denser charge of air under higher pressure in the manifold. Air compresses. At the velocity of air entering the manifold, it will put more molecules of air in the manifold, to get sucked down into the cylinder. More air+ more fuel= power.

Oh, hell I give up. Keep that stock piece of GM crap. If they were so damn great, why doesn't any speed shop sell them, and so many companies make 52 and 58mm ones? If the stock one was so damn good, there would not be a market for them at all.

HM Murdock

And with the valves opening and closing many many times a second, I want as much air and fuel as I can shove into the cylinder as possible.


But hey, who needs air and fuel to make power when we can just put stickers on our cars and gain 50 Honda HP for each one.

Mindgame

Yeah Eddie, that's basically what we have here, a law of diminishing returns.

Murdock,
Like I mentioned before, there are stock eliminator cars running in the high 10's now with the stock throttle body..... no modifications allowed in that area. Let's not make a mountain out of a mole-hill.

You are also assuming 100% ve in your response... then again I don't see where you're getting the numbers so I'm a bit confused. No attacks... just an observation. Just drop the attitude and the "I'm a physics guru" stuff and we'll all get along fine. You're a student right? I'm assuming you're relatively young.... 19-22 years old?
Stay cool.

-Mindgame

HM Murdock

Oh, and you don't have to do anything. But when your car is in the 11's or tens, you start looking for anything to gain a .1 or .2. It can mean the difference between the trophy and the loser prize.