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Optimizing

N

Necronommicon

CEG'er
Joined
Mar 31, 2007
Messages
432
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Flat Rock Mi
Was digging through some od posts about people optimizing their TB or LIM, I have a spare LIM though I read a few have tried it and it wasn't worth it. I know this is a dumb question and I will just be told to search. Well I did, and I didn't find the asnwer I was looking for. What exactly is optimizing the TB or LIM on a pretty much stock SVT going to do? Also people have used the 65mm TB, is this only if you have more mods done to your power plant?
 
Optiminzing the SVT TB will give you better throttle response and a little more power. Going to a 65mm TB will give you a drastic improvment in throttle response but you might notice it won't pull quite as well after 6k rpm which is not an issue for most ppl.

Only thing I'd do to the LIM is pull it off and clean it as per the archived how-to.
 
optimizing the svt throttle body will only improve power at WOT. Because thats the only time the center shaft becomes a restriction. The 65mm throttle body has a larger surface area compared to the svt tb. 5mm difference, where this helps during 1/4-1/2 throttle around town. At wot the 65mm throttle body is feeding too much air resulting in no power gain. ON a stock bone svt you will actually lose power because the increase of cfms is killing velocity.

I optimized my lim, with counter sunk screws and shaved the other side of the shaft down. This allowed more flow, and was noticed at the upper rpms. It seemed at 5k+ it pulled harder. This is where the 2nd runners were most effective period on our cars.
 
you will see some gains if you just clean the TB ,UIM, and LIM. If you fit an oil catch can on the oil breather system, you will keep that crisp smooth running longer. Also; i have a 65mm TB .. trust me, you would have to beat me with an effin' big stick to get me to take it off lol.... go for it .. your efforts will be rewarded ...G.
 
imnotacop420 said:
I dont think there is a how to for optimizing the LIM, its not going to be as easy as the TB thats for sure.
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It's not easy at all! The screws are a Pain in the arse, and most people fug up their lim as they attempt to do this mod. I've done 3 of them...and it's a process.
 
There was just a big bore group buy from SHO Source a little while ago. You could go this route but IMO, not worth it from what I've seen of the reported gains. Unsure if they "optimize" it too.

My solution? Wait till I do my 3L swap and swap in a full 3L with open secondaries and a tune to run without it.
 
Necronommicon said:
So I should see some decent gains if I optimized both the LIM and the TB? I think I may try this.
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Yes you will, but the throttle body optimization is a heck of a lot simpler then the lim. trust me it's difficult to tackle. Better off buying the sho-shop lim and calling it a day.
 
Harrry said:
At wot the 65mm throttle body is feeding too much air resulting in no power gain. ON a stock bone svt you will actually lose power because the increase of cfms is killing velocity.
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Here is the old saying: a motor is nothing but an air pump! Keeping this in mind, I tend to disagree with above 'too much air' statement. You can NEVER have too much air going through an engine (air flow = power). You have have to get larger injectors, or they are maxed out at high rpm. Are increase the fuel pressure (adjustable FPR) if you pump can get you higher pressure and the PR is pulling it down too low. And certainly tune for the nozzle size you used and the pressure. But KEEP THE AIR COMING!
 
Wrong, when you get too much air going in the velocity suffers and you lose power. You have to balance it out so everything works in unison.
 
ScottyDsntKnow said:
Wrong, when you get too much air going in the velocity suffers and you lose power. You have to balance it out so everything works in unison.
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Scott i didn't even bother..and you shouldn't either. Sounds like he's been taught with the old mind set of speed density cars...and even then things didn't work the same way he thinks. But thats what most backyard car junkies live by.

So i leave it be....It's for the better of man kind...(kinda thing :))
 
So I hear, I've had one of his for over a year now and every time I go to install it, something comes up lol. First the brakes took a •••• (NPG upgrade ftw), then I got a rash of CELs to fix, now a wheel bearing/dash swap and I'm betting as soon as I get all that done the 2.5L will start ticking or some such lol.

But yeah dude listen to Harry and just about EVERY other forum out there. Hell, there are HUGE threads on the corral about why you should NOT use a 75mm throttle body on a 94/95 Mustang 5.0 and instead use a 65mm/70mm depending on what your mods are but people still don't listen (they know better than experts/those with actual empirical evidence after all) and dyno sheets prove a drastic loss of torque down low and little to no gains all the way at the top.
 
Harrry said:
Scott i didn't even bother..and you shouldn't either. Sounds like he's been taught with the old mind set of speed density cars...and even then things didn't work the same way he thinks. But thats what most backyard car junkies live by.

So i leave it be....It's for the better of man kind...(kinda thing :))
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Well guys, I don't mind to get beaten up if there is something to learn in the process: what makes the 'velocity suffer' and where? Assuming constant flow (in CFM, but more accurately the engine sees lbs/min), a larger throttle body decreases the velocity through the TB. Fine. But why is that velocity decrease (and only across the throttle body; the velocity in other areas does not change since the cross sections don't change) create a loss of power?

I hope that none of the critics disagree with the rule: 10 flywheel horsepower for every lb of air (1 lb is 13.16 cubic foot at normal conditions) (the commonly used range is 9.5 to 10.5). More pounds of air through the engine (with the matching fuel to go along) = more power. Or how do you explain the additional power of turbo chargers? They are nothing but air pumps. quod erat demonstrandum.

I am NOT saying that a larger throttle body automatically allows more air through the engine; but if the TB is LIMITING the possible flow, removing the restriction will increase flow (and sufficient fuel available, increase power). Removing ANY restriction in the air path with have the effect (cleaning up your secondaries, UIM, LIM, high flow air filter,etc.). Increasing the air density will have that effect also (colder air, but also lower altitude, barometric pressure)
 
vtraudt said:
Well guys, I don't mind to get beaten up if there is something to learn in the process: what makes the 'velocity suffer' and where? Assuming constant flow (in CFM, but more accurately the engine sees lbs/min), a larger throttle body decreases the velocity through the TB. Fine. But why is that velocity decrease (and only across the throttle body; the velocity in other areas does not change since the cross sections don't change) create a loss of power?

I hope that none of the critics disagree with the rule: 10 flywheel horsepower for every lb of air (1 lb is 13.16 cubic foot at normal conditions) (the commonly used range is 9.5 to 10.5). More pounds of air through the engine (with the matching fuel to go along) = more power. Or how do you explain the additional power of turbo chargers? They are nothing but air pumps. quod erat demonstrandum.

I am NOT saying that a larger throttle body automatically allows more air through the engine; but if the TB is LIMITING the possible flow, removing the restriction will increase flow (and sufficient fuel available, increase power). Removing ANY restriction in the air path with have the effect (cleaning up your secondaries, UIM, LIM, high flow air filter,etc.). Increasing the air density will have that effect also (colder air, but also lower altitude, barometric pressure)
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Yes this is correct except the part about lower altitude and Baro. When altitude is lower then that means the barometric pressure is higher. This may have been a typo on your part since everything else is correct. The actual Barometric Pressure ( we call it Station Pressure - NOT the Barometric Pressure your TV weather man reports ) in Denver is 24.50 because it is 5000 feet above sea level, while it may be 30.09 at the shores of New Jersey. Every 961 feet ( approx ) is one point of Barometric Pressure. High Baro always means more power because it is Nature's supercharger.

I see velocity problems on my dragster. When I run on a throttle stop in Super Comp my intake manifold is far too large to run well below 4000 RPM. In order to compensate I have to increase the RPM while I am on the stop. When I get it right it comes back to full throttle perfectly, when I get it wrong it pops and farts a few times until the engine RPM matches the velocity it needs.

This is why Ford puts secondary throttle blades, so velocity matches engine RPM.
 
Those symptoms occur during part open throttle, which I would consider 'driveability' issues. I was only referring to WOT conditions. Naturally, with butterfly style throttles, the bigger the diameter gets, the more 'non linear' flow behavior you get during partial open conditions! Staged throttles mitigate this effect (knife gate valves would be nice!).

Soon, we will get rid of throttles (the key major source for the low efficiency in partial load operation of today's gas engines (compared to for examples throttleless diesel engines), and control the flow with fully variable, electrically controlled cylinder valves to get rid of the 'throttle losses'.
 
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