70MM Throttle body
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70MM Throttle body
Any 70mm throttle body owners still here?
Considering a larger throttle body to go with the air box mods. By itself I'd expect a drop in mpg but with a modded air box it might be different. I would be looking to get the best of both worlds between the 2 mods (TB & air box)
Why?... cause I know what the mods did for the Ram and I am greedy
Considering a larger throttle body to go with the air box mods. By itself I'd expect a drop in mpg but with a modded air box it might be different. I would be looking to get the best of both worlds between the 2 mods (TB & air box)
Why?... cause I know what the mods did for the Ram and I am greedy
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From: Clayton MI
Single barrel? For a two barrel, that is HUGE, and you will lose quite a bit of low-end torque. If you ran your engine at WOT all the time, I can see how the bigger throttle bores might help, but, on a daily driver? Way too big.
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the stock one is a 68mm tb, it is not that big if a change. my thinking is for the higher load conditions that would require more air that mated with the modded air box may give the best of both worlds
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From: Clayton MI
Ah, ok. That explains it. 
I am just not as familiar with the 4.7 as I would like to be.
In that case, bumping up a couple millimeters shouldn't hurt you. Probably see somewhat better off-idle throttle response.
I am just not as familiar with the 4.7 as I would like to be.In that case, bumping up a couple millimeters shouldn't hurt you. Probably see somewhat better off-idle throttle response.
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I have read that the throttle response does change for sure, had a 52mm fastman years back on the 2000 I had and did not notice any drop in bottom end, however I was not sensitive to that change back then.
What I am trying to wrap my head around is the airflow velocity and how it generates bottom end torque. If I understand it correctly, there needs to be a balance of quantity & velocity to fill the cylinders. Since the runner length and head config will not change, that only leaves velocity. With what I've concluded (again) on the airbox flow, the easier the flow thru the box, the higher up the rpm range the torque peak goes.
I may have a different view of the TB after the intake tube is swapped out. Either it will be the Airaid tube or I will make one. ONe thing I'd explore if I make one is setting up the intake tube where the flow into the throttle body is straighter than the current setup with an expansion area far enough in front of TB to accelerate airflow thru the TB. Will need to play with that if I get there.
What I am trying to wrap my head around is the airflow velocity and how it generates bottom end torque. If I understand it correctly, there needs to be a balance of quantity & velocity to fill the cylinders. Since the runner length and head config will not change, that only leaves velocity. With what I've concluded (again) on the airbox flow, the easier the flow thru the box, the higher up the rpm range the torque peak goes.
I may have a different view of the TB after the intake tube is swapped out. Either it will be the Airaid tube or I will make one. ONe thing I'd explore if I make one is setting up the intake tube where the flow into the throttle body is straighter than the current setup with an expansion area far enough in front of TB to accelerate airflow thru the TB. Will need to play with that if I get there.
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From: Clayton MI
That's where the whole 'tuned length runners' thing comes in. The intake is designed to be 'most efficient' within a given RPM range, such that the pressure pulses from valves opening/closing will aid in cylinder filling. The science is out there, but, WAY beyond what I can explain here. (or pretty much anywhere else for that matter. )
It's like the old GM Tuned Port Injection motors of the 80s-90's. The TPI 350 was a torque MONSTER (for the time), but, ran out of breath around 4500 RPM, and power output dropped off like a stone. Of course, in the rpm range the manifold was designed to operate best at, (around 1500 to 4000 rpm,) it was great. Loved it in my old Firebird Formula.
Tuning on the GM products was also a lot easier. (there are whole communities dedicated to it.....) For gas mileage mods, one of the favorite tricks was to invoke "highway mode". It would run the mixture lean, under VERY specific circumstances, and could dramatically improve highway mileage. Some folks with well-tuned engines were pushing 28MPG on the freeway. But, those cars also had knock sensors..... (your should as well?? I think)
)It's like the old GM Tuned Port Injection motors of the 80s-90's. The TPI 350 was a torque MONSTER (for the time), but, ran out of breath around 4500 RPM, and power output dropped off like a stone. Of course, in the rpm range the manifold was designed to operate best at, (around 1500 to 4000 rpm,) it was great.
Loved it in my old Firebird Formula.Tuning on the GM products was also a lot easier. (there are whole communities dedicated to it.....) For gas mileage mods, one of the favorite tricks was to invoke "highway mode". It would run the mixture lean, under VERY specific circumstances, and could dramatically improve highway mileage. Some folks with well-tuned engines were pushing 28MPG on the freeway. But, those cars also had knock sensors..... (your should as well?? I think)
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That's where the whole 'tuned length runners' thing comes in. The intake is designed to be 'most efficient' within a given RPM range, such that the pressure pulses from valves opening/closing will aid in cylinder filling. The science is out there, but, WAY beyond what I can explain here. (or pretty much anywhere else for that matter. )
It's like the old GM Tuned Port Injection motors of the 80s-90's. The TPI 350 was a torque MONSTER (for the time), but, ran out of breath around 4500 RPM, and power output dropped off like a stone. Of course, in the rpm range the manifold was designed to operate best at, (around 1500 to 4000 rpm,) it was great. Loved it in my old Firebird Formula.
Tuning on the GM products was also a lot easier. (there are whole communities dedicated to it.....) For gas mileage mods, one of the favorite tricks was to invoke "highway mode". It would run the mixture lean, under VERY specific circumstances, and could dramatically improve highway mileage. Some folks with well-tuned engines were pushing 28MPG on the freeway. But, those cars also had knock sensors..... (your should as well?? I think)
)It's like the old GM Tuned Port Injection motors of the 80s-90's. The TPI 350 was a torque MONSTER (for the time), but, ran out of breath around 4500 RPM, and power output dropped off like a stone. Of course, in the rpm range the manifold was designed to operate best at, (around 1500 to 4000 rpm,) it was great.
Loved it in my old Firebird Formula.Tuning on the GM products was also a lot easier. (there are whole communities dedicated to it.....) For gas mileage mods, one of the favorite tricks was to invoke "highway mode". It would run the mixture lean, under VERY specific circumstances, and could dramatically improve highway mileage. Some folks with well-tuned engines were pushing 28MPG on the freeway. But, those cars also had knock sensors..... (your should as well?? I think)
runner length, the manifold on this motor has the longest runner lengths of the ones available. the 1999, 2000 throttle bodies are the smallest at 65, cant imagine i would try one...
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TIt's like the old GM Tuned Port Injection motors of the 80s-90's. The TPI 350 was a torque MONSTER (for the time), but, ran out of breath around 4500 RPM, and power output dropped off like a stone. Of course, in the rpm range the manifold was designed to operate best at, (around 1500 to 4000 rpm,) it was great. Loved it in my old Firebird Formula.
Loved it in my old Firebird Formula.Tuning on the GM products was also a lot easier. (there are whole communities dedicated to it.....) For gas mileage mods, one of the favorite tricks was to invoke "highway mode". It would run the mixture lean, under VERY specific circumstances, and could dramatically improve highway mileage. Some folks with well-tuned engines were pushing 28MPG on the freeway. But, those cars also had knock sensors..... (your should as well?? I think)
Coming from the world of GM has its uses.
Last edited by Vimes; Dec 13, 2021 at 10:24 PM.