To the pros: Which of these 3 Mods creates the most lag?
Hard to put and end to some things. I already calculated the internal cubic feet of 20 feet of 2.5" tube for one post to illustrate how a turbo would instantly fill the space producing no noticeable lag due to even an egregious amount of intercooler piping (It's less than 1 cubic foot btw). Now to put the math down on a "Large core/time to fill" comment. I'm not hating btw, I just don't like how myths get started.
Example - A huge frontal are core 24x14x3 or 4"
24x14x3 = 1008 inches cubed
24x14x4 = 1344 inches cubed
for a difference of 336
1 cubic foot of air is 1728 inches cubed
The difference is a whopping .19444 cubic feet which would fill in a millisecond and you would never know the difference. This is assuming also that the core is an empty box which it isn't, so the number in reality is even smaller probably in the .06 CF range if you subtract the turbulators and external channels.
Barring the use of a walnut sized turbo and a intercooler core the size of your hood, bigger is always better. Proper sizing should be considered, but more for, will it handle what I throw at it, rather than does it handle more than I need.
/brox
Example - A huge frontal are core 24x14x3 or 4"
24x14x3 = 1008 inches cubed
24x14x4 = 1344 inches cubed
for a difference of 336
1 cubic foot of air is 1728 inches cubed
The difference is a whopping .19444 cubic feet which would fill in a millisecond and you would never know the difference. This is assuming also that the core is an empty box which it isn't, so the number in reality is even smaller probably in the .06 CF range if you subtract the turbulators and external channels.
Barring the use of a walnut sized turbo and a intercooler core the size of your hood, bigger is always better. Proper sizing should be considered, but more for, will it handle what I throw at it, rather than does it handle more than I need.
/brox
Don
My stock VIII turbo spooled up around 300 rpm earlier after installing an SS Auto chrome o2 housing, which is not all that special, but it stood the test of time, was better then stock and was a lot lighter. There is no way it is the o2 housing. Whats left...the tune. If its not the tune then, you need to look for boost leaks. Do you have a smoke machine handy?
I've tried to stop people from perpetuating some stuff like this but it doesn't seem to sink in.
Even a huge FMIC MIGHT increase the real internal volume of the space between the compressor outlet and the throttle body by .5 cubic foot over the stock intercooler. That's a half a cubic foot. The internal volume of an intercooler is just not that big people.
Even if we don't subtract the external channels, which intake air doesn't flow though, or subtract for the volume taken up by the turbulators, which the stock IC doesn't have because it's tube/fin not bar/plate, the size difference is still incredibly small. And that size difference is not nearly, not by a long shot, large enough for anyone to notice "Lag".
The stock IC is what, I'll shoot low on it, maybe 18x2.75x12? OK, so 594 cubic inches. I have a huge FMIC on my car, massive even. It's 24x4.5x14. That's 1620 cubic inches, for a difference of 1026. That's .6 cubic feet people. And that's NOT subtracting for the external channels on either core or the turbulators on my core. If I factor those things in, it's closer to .3 cubic feet. As soon as anyone short of Michael Schumacher can feel the difference of .3 or even .6 cubic feet in the intake tract, you let me know. You might think you can. It's in your head. A log would prove it. Furthermore with the cooler intake charge of a large FMIC, not causing any lag at all, you can increase timing and spool up faster.
Lag is caused by one thing. A larger restriction in the exhaust stream. That's it. A bigger or heavier turbine wheel or a restriction after the turbo. Don't say larger IC pipes either, I already did that math. You could double the length of pipe you have on your car right now and it would add .75 cubic feet of space.
If it's not one forum it's another. I apparently honestly cannot repeat it enough. Your turbo will fill the extra volume of a large IC in a split second, a fraction of a second, an unnoticeable blip on the rpm band. If the Ops car was supercharged, then we could talk about lag due to increased volume before the plate. Other than that unlikely scenario, the factual answer is NONE of the things you have listed will increase lag to any sort of degree you are going to notice.
/brox
Edit: I can see I have been quoted above as I was writing the post. Good times. I have spoken to Corky about this subject to the point where he is sick of me asking him. I can assure you the theoretical and practical application of a larger intercooler will perform as the math in either post lays it out.
//brox
Even a huge FMIC MIGHT increase the real internal volume of the space between the compressor outlet and the throttle body by .5 cubic foot over the stock intercooler. That's a half a cubic foot. The internal volume of an intercooler is just not that big people.
Even if we don't subtract the external channels, which intake air doesn't flow though, or subtract for the volume taken up by the turbulators, which the stock IC doesn't have because it's tube/fin not bar/plate, the size difference is still incredibly small. And that size difference is not nearly, not by a long shot, large enough for anyone to notice "Lag".
The stock IC is what, I'll shoot low on it, maybe 18x2.75x12? OK, so 594 cubic inches. I have a huge FMIC on my car, massive even. It's 24x4.5x14. That's 1620 cubic inches, for a difference of 1026. That's .6 cubic feet people. And that's NOT subtracting for the external channels on either core or the turbulators on my core. If I factor those things in, it's closer to .3 cubic feet. As soon as anyone short of Michael Schumacher can feel the difference of .3 or even .6 cubic feet in the intake tract, you let me know. You might think you can. It's in your head. A log would prove it. Furthermore with the cooler intake charge of a large FMIC, not causing any lag at all, you can increase timing and spool up faster.
Lag is caused by one thing. A larger restriction in the exhaust stream. That's it. A bigger or heavier turbine wheel or a restriction after the turbo. Don't say larger IC pipes either, I already did that math. You could double the length of pipe you have on your car right now and it would add .75 cubic feet of space.
If it's not one forum it's another. I apparently honestly cannot repeat it enough. Your turbo will fill the extra volume of a large IC in a split second, a fraction of a second, an unnoticeable blip on the rpm band. If the Ops car was supercharged, then we could talk about lag due to increased volume before the plate. Other than that unlikely scenario, the factual answer is NONE of the things you have listed will increase lag to any sort of degree you are going to notice.
/brox
Edit: I can see I have been quoted above as I was writing the post. Good times. I have spoken to Corky about this subject to the point where he is sick of me asking him. I can assure you the theoretical and practical application of a larger intercooler will perform as the math in either post lays it out.
//brox
Last edited by Broxma; Feb 21, 2009 at 12:03 PM.
Evolved Member
Joined: Jul 2005
Posts: 619
Likes: 0
From: Istanbul
not the o2 or the hardpipe. my car actuall lost power and was lazy after installing upper IC pipe, APS intercooler, injectors and full race manifold. the tune tweaked by the same tuner. it just did not work out until I got someone with more experience mapping the car to get the car driving right again (and make an additional 10HP to boot)
I wish I could afford the Ralliart hardpipe kit, but that's another story. What exactly do you mean when you say that the Ralliart hardpipe kit, "....sounds EVIL"? Do the intercooler pipes produce a distinctive noise, or sound? Are you running the stock diverter valve or, maybe, an aftermarket BOV? I am still trying to figure out why your car seems less responsive. Is the exhaust equipped with a catalytic convertor, or a test pipe?
As others have mentioned, none of the three mods which you have listed should have any significant negative impact on turbo spoolup. In fact, to the contrary, the tubular O2 housing will make the turbo spoolup faster, as should the IC pipes. The impact of the additional IC volume should be negligible really, as Broxma has already noted.
As others have mentioned, none of the three mods which you have listed should have any significant negative impact on turbo spoolup. In fact, to the contrary, the tubular O2 housing will make the turbo spoolup faster, as should the IC pipes. The impact of the additional IC volume should be negligible really, as Broxma has already noted.
Last edited by sparky; Feb 21, 2009 at 09:35 AM.
Thread
Thread Starter
Forum
Replies
Last Post