intake mani or throttle body?"
My logic would say the throttle body would be the one to change if you had to do one or the other. Why? Well to me I have a hard time believing that the FULL potential of the stock intake manifold is reached with a stock throttle body or even a bored-out throttlebody. The throttle body is the bigger cork in the system.
I would look at it like you look at the exhaust on the car, do you get a testpipe first or a header? They are both going to make gains but the header takes the bigger cork out and makes the bigger gain. Why? because its first in the exhaust flow chain. Same as the throttlebody assuming you already have an intake. You cant get more out if you dont put more in. With the throttle body being the choke point what good does it do to open up the intake manifold behind it?
I would look at it like you look at the exhaust on the car, do you get a testpipe first or a header? They are both going to make gains but the header takes the bigger cork out and makes the bigger gain. Why? because its first in the exhaust flow chain. Same as the throttlebody assuming you already have an intake. You cant get more out if you dont put more in. With the throttle body being the choke point what good does it do to open up the intake manifold behind it?
well here's how i see it. if you wanna slow down air at the throttle body to just adequately feed the higher vacuum in the intake runners, get the TB. if the TB is too big, the IM might be having to "pull" air through the TB instead of the TB supplying the right amount of air at the right speed like it should be doing. this all depends on how bad/good your IM was casted from the factory. the opening from the IM to the TB seems to be well ported on all cars i've seen. the larger TB might kill a bit of low end torque for some better top end.
if you wanna create more vacuum in the runners creating a bit more torque down low and not suffering up top, then the IM should be your upgrade. the top end either is not going to change at all or see a bit more improvement. down low torque should increase due to the higher vacuum in the manifold. you just got rid of the restriction closest to vacuum making device: the cylinder. this should give you a broader powerband that starts earlier but ends up similar or better up top.
longer skinnier runners makes for better torque with limited top end. shorty fat runners are bad for torque, but better up top(pertains to the TB). not only do you have to factor in the IM and TB, you have to think about whether you have a sri or cai. why do people "think" a sri gives better throttle response? because the vacuum from the engine has less distance to travel to open air than a cai(and is still sucking in hot hp robbing engine air) causing the engine to react to the pedal faster. but once a cai has air coming in, torque goes up as air speeds in and dies out past peak torque.
comparing intake to exhaust is a bit different as intake is being supplied by a mass of air to sequential intake pumps. most of the air comes in as one mass that separates near the end and mostly you just worry about turbulence. exhaust comes out as pulses and seems a bit more complicated to me as you worry about the pulses crashing into each other or going back up the exhaust into the engine again.
all in all, it doesn't really matter at this point of modding. the difference right now are pennies and nickels. of course getting both would complement each other. just giving my take on thinking about the intake system as a whole.
if you wanna create more vacuum in the runners creating a bit more torque down low and not suffering up top, then the IM should be your upgrade. the top end either is not going to change at all or see a bit more improvement. down low torque should increase due to the higher vacuum in the manifold. you just got rid of the restriction closest to vacuum making device: the cylinder. this should give you a broader powerband that starts earlier but ends up similar or better up top.
longer skinnier runners makes for better torque with limited top end. shorty fat runners are bad for torque, but better up top(pertains to the TB). not only do you have to factor in the IM and TB, you have to think about whether you have a sri or cai. why do people "think" a sri gives better throttle response? because the vacuum from the engine has less distance to travel to open air than a cai(and is still sucking in hot hp robbing engine air) causing the engine to react to the pedal faster. but once a cai has air coming in, torque goes up as air speeds in and dies out past peak torque.
comparing intake to exhaust is a bit different as intake is being supplied by a mass of air to sequential intake pumps. most of the air comes in as one mass that separates near the end and mostly you just worry about turbulence. exhaust comes out as pulses and seems a bit more complicated to me as you worry about the pulses crashing into each other or going back up the exhaust into the engine again.
all in all, it doesn't really matter at this point of modding. the difference right now are pennies and nickels. of course getting both would complement each other. just giving my take on thinking about the intake system as a whole.
it's not totally about more air/more fuel. it's more like controlling air/fuel. if we stuck on a 90mm TB, we would suffer in the low end waiting for ages to hit the powerband. then when you hit the powerband, hp goes up dramatically. for some of us, that's a useless powerband. how your whole air induction system is setup pretty much lays out where your powerband is going to be. it sets where peak torque and hp is(aside from intake cam profile).
let's take a look at variable valve timing. the lower profile used for the lower rpm band has shorter lift. this means a smaller valve opening, thus air comes in faster to fill the cylinder producing more torque. when you get higher into the rpms, cam profiles change to higher lift and duration to support high rpm horsepower. this example could also be seen in dual intake runner setups like toyotas as well as variable intake lengths found in german cars. these technologies try to have faster moving air at low rpms and higher volume at high rpms. this just goes to show that bigger all around is not the best thing.
let's take a look at variable valve timing. the lower profile used for the lower rpm band has shorter lift. this means a smaller valve opening, thus air comes in faster to fill the cylinder producing more torque. when you get higher into the rpms, cam profiles change to higher lift and duration to support high rpm horsepower. this example could also be seen in dual intake runner setups like toyotas as well as variable intake lengths found in german cars. these technologies try to have faster moving air at low rpms and higher volume at high rpms. this just goes to show that bigger all around is not the best thing.
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Joined: Sep 2004
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labor costs for a shop are around $70+ an hour, so i really wouldnt do that. It will be a difficult install but thats just cause of all the parts and pieces. Wouldnt you feel beter if you installed it yourself? but yeah i heard the IM is a very restrictive part, in any car for that matter[/QUOTE]
hi. i was wondering if anyone knows how hard it would be to port and polish your own intake manifold. I have a dye(sp) grinder and all sorts of brushes but i thought i better ask and see if anyone had tried it already.
hi. i was wondering if anyone knows how hard it would be to port and polish your own intake manifold. I have a dye(sp) grinder and all sorts of brushes but i thought i better ask and see if anyone had tried it already.
