Bigger FMIC = More Lag
Apr 16, 2009 | 04:18 PM
#2
depends., there might be a drop in pressure due to size.. but before you go bigger.... you should do an analysis of what intercooler core size you REALLY need for your power goals.
here is a good book:
http://www.amazon.com/Maximum-Boost-...toc/0837601606
here is a good book:
http://www.amazon.com/Maximum-Boost-...toc/0837601606
Apr 16, 2009 | 07:25 PM
#4
I noticed increase lag with the larger FMIC, I think it's due to the fact that it's having to fill more volume of air (stock 2.5" I think vs Buschur 4.5" thickness). After I got a tune though the lag is gone and it spools faster now than it did before the new FMIC. Power came on harder when it did have more lag up top though for sure.
Apr 16, 2009 | 07:40 PM
#5
Does UICP and LICP matter in terms of diameter of the piping? 3" vs 2.5" I am trying to stay with a stock turbo, maybe years from now upgrade to a Garrett unit.
Should I get 3" piping and a larger FMIC? or get 2.5" piping and get a smaller FMIC?
Current power goals BELOW 400whp on stock turbo and fuel system.
Should I get 3" piping and a larger FMIC? or get 2.5" piping and get a smaller FMIC?
Current power goals BELOW 400whp on stock turbo and fuel system.
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Apr 17, 2009 | 01:11 AM
#8
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Apr 17, 2009 | 08:37 AM
#9
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From what I understand and my experiences, a bigger FMIC will indeed cause more lag.
If you upsized your core to 3.5 or 4" (flow rate 1500 to 2000cfm) you have double the volume to fill compared to the stock intercooler. Your 152G turbo only outputs ~550cfm at stock boost so it will take a longer time to pressurize an upsized intercooler.
So the bigger the intercooler, the larger the psi drop and longer time needed to pressurize the intake circuit. A higher absolute pressure is also required to create the same boost level in the cylinders.
This is where people begin to deny that a bigger FMIC causes more lag, because their cars were tuned after the install and it shows a stock-like boost curve with additional power. But the simplified explanation as to what is happening here is that the tune has raised your boost and is pressurizing the intake side faster giving the illusion that there is no lag caused by the FMIC. If you have a stock FMIC with the same tune on the same dyno it is guaranteed you will spool 2-400 rpm faster than stock and bigger FMIC with even better low and midrange response at the cost of some top end power - which I believe is not useful for the street anyway.
Is there a benefit to running a huge intercooler? If you have a bigger turbo, free flowing exhaust and other mods to support a better breathing system. The only intercooler that is better for the stock turbo is the ARC/ColtSpeed 2.5" core with a more efficient fin design that flows faster but retains a stock volume.
And the 2.5" vs. 3" intercooler piping debate. You want to stick with close to stock diameter intercooler piping for the same principles mentioned above. If our stock turbo outputs 500cfm, air gets pushed in a 3" pipe at a max velocity of 115mph - very laminar, but slow and you will feel the lag and unresponsiveness. If the same 500cfm was pushed through 2.25" piping it would result in an increase in velocity to 205mph, which is also very laminar, but fast - resulting in great throttle response, no lag with instant power. Our stock intercooler latex pipe is around 2.25" but expands under boost to ~2.5" so a 2.5" aftermarket pipe would be a good choice especially with a tune. Nobody needs a 3" pipe not even for most aftermarket turbos available for the X.
If you upsized your core to 3.5 or 4" (flow rate 1500 to 2000cfm) you have double the volume to fill compared to the stock intercooler. Your 152G turbo only outputs ~550cfm at stock boost so it will take a longer time to pressurize an upsized intercooler.
So the bigger the intercooler, the larger the psi drop and longer time needed to pressurize the intake circuit. A higher absolute pressure is also required to create the same boost level in the cylinders.
This is where people begin to deny that a bigger FMIC causes more lag, because their cars were tuned after the install and it shows a stock-like boost curve with additional power. But the simplified explanation as to what is happening here is that the tune has raised your boost and is pressurizing the intake side faster giving the illusion that there is no lag caused by the FMIC. If you have a stock FMIC with the same tune on the same dyno it is guaranteed you will spool 2-400 rpm faster than stock and bigger FMIC with even better low and midrange response at the cost of some top end power - which I believe is not useful for the street anyway.
Is there a benefit to running a huge intercooler? If you have a bigger turbo, free flowing exhaust and other mods to support a better breathing system. The only intercooler that is better for the stock turbo is the ARC/ColtSpeed 2.5" core with a more efficient fin design that flows faster but retains a stock volume.
And the 2.5" vs. 3" intercooler piping debate. You want to stick with close to stock diameter intercooler piping for the same principles mentioned above. If our stock turbo outputs 500cfm, air gets pushed in a 3" pipe at a max velocity of 115mph - very laminar, but slow and you will feel the lag and unresponsiveness. If the same 500cfm was pushed through 2.25" piping it would result in an increase in velocity to 205mph, which is also very laminar, but fast - resulting in great throttle response, no lag with instant power. Our stock intercooler latex pipe is around 2.25" but expands under boost to ~2.5" so a 2.5" aftermarket pipe would be a good choice especially with a tune. Nobody needs a 3" pipe not even for most aftermarket turbos available for the X.
Apr 17, 2009 | 09:28 AM
#11
Does UICP and LICP matter in terms of diameter of the piping? 3" vs 2.5" I am trying to stay with a stock turbo, maybe years from now upgrade to a Garrett unit.
Should I get 3" piping and a larger FMIC? or get 2.5" piping and get a smaller FMIC?
Current power goals BELOW 400whp on stock turbo and fuel system.
Should I get 3" piping and a larger FMIC? or get 2.5" piping and get a smaller FMIC?
Current power goals BELOW 400whp on stock turbo and fuel system.
Apr 17, 2009 | 09:36 AM
#13
From what I understand and my experiences, a bigger FMIC will indeed cause more lag.
If you upsized your core to 3.5 or 4" (flow rate 1500 to 2000cfm) you have double the volume to fill compared to the stock intercooler. Your 152G turbo only outputs ~550cfm at stock boost so it will take a longer time to pressurize an upsized intercooler.
So the bigger the intercooler, the larger the psi drop and longer time needed to pressurize the intake circuit. A higher absolute pressure is also required to create the same boost level in the cylinders.
This is where people begin to deny that a bigger FMIC causes more lag, because their cars were tuned after the install and it shows a stock-like boost curve with additional power. But the simplified explanation as to what is happening here is that the tune has raised your boost and is pressurizing the intake side faster giving the illusion that there is no lag caused by the FMIC. If you have a stock FMIC with the same tune on the same dyno it is guaranteed you will spool 2-400 rpm faster than stock and bigger FMIC with even better low and midrange response at the cost of some top end power - which I believe is not useful for the street anyway.
Is there a benefit to running a huge intercooler? If you have a bigger turbo, free flowing exhaust and other mods to support a better breathing system. The only intercooler that is better for the stock turbo is the ARC/ColtSpeed 2.5" core with a more efficient fin design that flows faster but retains a stock volume.
And the 2.5" vs. 3" intercooler piping debate. You want to stick with close to stock diameter intercooler piping for the same principles mentioned above. If our stock turbo outputs 500cfm, air gets pushed in a 3" pipe at a max velocity of 115mph - very laminar, but slow and you will feel the lag and unresponsiveness. If the same 500cfm was pushed through 2.25" piping it would result in an increase in velocity to 205mph, which is also very laminar, but fast - resulting in great throttle response, no lag with instant power. Our stock intercooler latex pipe is around 2.25" but expands under boost to ~2.5" so a 2.5" aftermarket pipe would be a good choice especially with a tune. Nobody needs a 3" pipe not even for most aftermarket turbos available for the X.
If you upsized your core to 3.5 or 4" (flow rate 1500 to 2000cfm) you have double the volume to fill compared to the stock intercooler. Your 152G turbo only outputs ~550cfm at stock boost so it will take a longer time to pressurize an upsized intercooler.
So the bigger the intercooler, the larger the psi drop and longer time needed to pressurize the intake circuit. A higher absolute pressure is also required to create the same boost level in the cylinders.
This is where people begin to deny that a bigger FMIC causes more lag, because their cars were tuned after the install and it shows a stock-like boost curve with additional power. But the simplified explanation as to what is happening here is that the tune has raised your boost and is pressurizing the intake side faster giving the illusion that there is no lag caused by the FMIC. If you have a stock FMIC with the same tune on the same dyno it is guaranteed you will spool 2-400 rpm faster than stock and bigger FMIC with even better low and midrange response at the cost of some top end power - which I believe is not useful for the street anyway.
Is there a benefit to running a huge intercooler? If you have a bigger turbo, free flowing exhaust and other mods to support a better breathing system. The only intercooler that is better for the stock turbo is the ARC/ColtSpeed 2.5" core with a more efficient fin design that flows faster but retains a stock volume.
And the 2.5" vs. 3" intercooler piping debate. You want to stick with close to stock diameter intercooler piping for the same principles mentioned above. If our stock turbo outputs 500cfm, air gets pushed in a 3" pipe at a max velocity of 115mph - very laminar, but slow and you will feel the lag and unresponsiveness. If the same 500cfm was pushed through 2.25" piping it would result in an increase in velocity to 205mph, which is also very laminar, but fast - resulting in great throttle response, no lag with instant power. Our stock intercooler latex pipe is around 2.25" but expands under boost to ~2.5" so a 2.5" aftermarket pipe would be a good choice especially with a tune. Nobody needs a 3" pipe not even for most aftermarket turbos available for the X.
Apr 17, 2009 | 09:41 AM
#14
This post contains a lot of inaccurate information. It's actually a good thing to upgrade the intercooler even on the stock turbo. The stock unit has a tendency to heat soak, cause knock in a 3rd gear pull and makes the car not very consistent pass after pass. When you upgrade your intercooler to a bar and plate intercooler you get very consistent back to back runs, the ability to run more timing with the cooler AIT. The Evolution x actually gained 1.5 psi of boost when using a 4.0" intercooler compared to the stock unit and picked up 24whp. There was also no noticeable decrease in spool up time. We have never had an Evolution X that didn't benefit from an upgraded intercooler.
If you have any more questions, let me know!
Thanks Everyone!
Michael
If you have any more questions, let me know!
Thanks Everyone!
Michael
Apr 17, 2009 | 10:04 AM
#15
no...
I seem to quote this guy a lot on this topic. People continue to think that a bigger IC is going to create lag but it just won't (^^^ he even does the gerneral math).
Don
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
Don