Turbo Lag From A FMIC

[Daniel Young]

It happened to just dawn on me that adding a Larger front mount intercooler say from ion or the one wagner is prototyping will make our turbo's lag alot more. I'm not very mechanically knowledgeable about how a turbo system works. But wouldn't that be a Con from adding a FMIC? I guess the pro would be the added horsepower and more torque from the cooler boost. But how do they work in comparison to each other? Won't there be some hesitation to the throttle?

 

[Notorious]

You'll get pressure drop, but not lag.

 

[Daniel Young]

Why's that? It seems that I have seen an increase in horsepower up to 25 more by adding the fmic

 

[azian6er]

well in essence, pressure drop will cause the turbo not to spool up as fast, so it is lag in a sense.

When you install a fmic, there is more volume of air to fill (bigger IC core) thus there will be a little pressure loss, but nothing to get your pants in a bunch about.

You are gaining power with the fmic because it is not subject to heatsoak as much so the air going into your engine is colder i.e more dense thus a larger number of combustions is able to take place in your engine and hence you make more power.

Dont worry, any lag you are getting is made up for by the fmic cooling the intake charge.

-B

 

[YuYuRena]

let's say that having a larger ic will = larger volume of "piping" needed to pressurized by our turbo = more time = turbo lag. it's not only for fmic, but rather any larger size ic than our stock one. pressure drop comes about because of longer piping, the bends in all the pipes (fmic notoriously for long and twisty piping). So take a fluid dynamic class if you want equations and formulas or just drive the car and be happy with boost!!

 

[t3ase]

so what if there's "hesitation at throttle"? you're protecting your engine.

 

[bill harvey]

has anyone ever measured the pressure drop on the terrible stock intercooler? i would bet it is worse than a well designed fmic with a good core.

 

[azian6er]

has anyone ever measured the pressure drop on the terrible stock intercooler? i would bet it is worse than a well designed fmic with a good core.

No. A well designed IC core still will have more internal volume that it has to fill. Our stock IC is so small that the internal volume is very small and it heatsoaks very easy.

The larger the volume of the IC the higher the pressure loss on average.

-B

 

[bill harvey]

but a larger bar and plate will flow better than our stocker. pressure drop isn't how much time the volume takes to fill its the amount of pressure lost flowing through the intercooler. 6psi in 5 psi out 1 psi of pressure drop. there is no way the stock one flows well. the bar and plate i had in my subaru flowed so well you could hear it. you may get a lack of boost response but that doesn't mean it is caused by pressure drop.

 

[perfworks]

You'll get pressure drop, but not lag.

Almost correct.
At least more correct then some other assumptions here.
In the case with the FMIC Wagner and I are working on- Bar and Plate design. LESS pressure drop and better quality of oxygen molecules after the fact

 

[bill harvey]

Asian6er: If what you are saying is true than you would have to turn up the boost on the turbo to get the smae 6psi at the manifold. if your, if this is the case with your car i would get a new core.

 

[perfworks]

Why's that? It seems that I have seen an increase in horsepower up to 25 more by adding the fmic

Your increase in HP was due to cooling efficiency in comparison to a vehicle at the same ambient temp with an extruded core coooler, pressure drop and lack of VE at the same RPM

 

[perfworks]

well in essence, pressure drop will cause the turbo not to spool up as fast, so it is lag in a sense.

When you install a fmic, there is more volume of air to fill (bigger IC core) thus there will be a little pressure loss, but nothing to get your pants in a bunch about.

You are gaining power with the fmic because it is not subject to heatsoak as much so the air going into your engine is colder i.e more dense thus a larger number of combustions is able to take place in your engine and hence you make more power.

Dont worry, any lag you are getting is made up for by the fmic cooling the intake charge.

-B

Not really correct here Brian. Lag has almost nothing to do with the pressure side of the turbo. It is totally dependent on the Volumetric efficiency of your engine and the turbine AR.
The quicker the vehicle builds the energy needed to expel and spin the turbine the less "lag" you will experience. Also it depends on the size of the inlet nozzle area. The samller it is (generally) the quicker spool up characteristics you will have.
Lag is just a general term. You get it with and without a turbo. The difference is that with a turbo you get a noticable torque increase depending on turbine speed and size at a given RPM
Boost threshold

Now the MORE volume of air is after the IC not before. Before It is the same as it was with any cooler , again comparing it with the same turbo.
After the core the charge temps will be cooler of course . But depending on many things the question is how much.
Remember MASS will be the same . Volume will increase and decrease depending on ambient temp. So density is what is affected . Not boost pressure(mass).

 

[perfworks]

let's say that having a larger ic will = larger volume of "piping" needed to pressurized by our turbo = more time = turbo lag. it's not only for fmic, but rather any larger size ic than our stock one. pressure drop comes about because of longer piping, the bends in all the pipes (fmic notoriously for long and twisty piping). So take a fluid dynamic class if you want equations and formulas or just drive the car and be happy with boost!!

In theory you could say that the longer and more diameter the piping the more "time " it will take to get to the valve. But in most automotive applications where you are ALREADY pressurized thru atmoshperic pressure, this is not true. Turbo lag is soley dependant on the turbine shaft speed at the same given RPM.
Once the car is idleing you already have pressure against the valve all the time. The difference with the FMIC is very minimal. In fact it becomes even more minimal when the "density of the air" is incresaed thru the fins of the core. Making the pressure more consistent thru the piping.

 

[azian6er]

Not really correct here Brian. Lag has almost nothing to do with the pressure side of the turbo. It is totally dependent on the Volumetric efficiency of your engine and the turbine AR.
The quicker the vehicle builds the energy needed to expel and spin the turbine the less "lag" you will experience. Also it depends on the size of the inlet nozzle area. The samller it is (generally) the quicker spool up characteristics you will have.
Lag is just a general term. You get it with and without a turbo. The difference is that with a turbo you get a noticable torque increase depending on turbine speed and size at a given RPM
Boost threshold

Now the MORE volume of air is after the IC not before. Before It is the same as it was with any cooler , again comparing it with the same turbo.
After the core the charge temps will be cooler of course . But depending on many things the question is how much.
Remember MASS will be the same . Volume will increase and decrease depending on ambient temp. So density is what is affected . Not boost pressure(mass).

Sounds good. Nice explanation. i learn new things every day.

So hypothetically A good IC core even if 4x the size of the stocker will have minimal or no pressure loss of the stock unit then correct?

-B

 

[perfworks]

has anyone ever measured the pressure drop on the terrible stock intercooler? i would bet it is worse than a well designed fmic with a good core.

THIS restriction is also what causes you to have quicker heat soak and less pressure against the valve. The stock core is HORRIBLE. I haven't measured the drop. Basically because it is "known " to be significant above stock boost levels. Just isnt worth the time really. It will not get proportionately worse. In fact it gets "horrible" with more boost. (even worse than proportional)

 

[perfworks]

Sounds good. Nice explanation. i learn new things every day.

So hypothetically A good IC core even if 4x the size of the stocker will have minimal or no pressure loss of the stock unit then correct?

-B

It depends on the design of the core. Also depends on HOW it is being forced thru. End tank design.
If it is of bar and plate design, then they are generally made to handle a larger volume of air without restriction. They cool very well also again depending on the airflow characteristics thru the front of your vehicle.
Extruded core IC like the one you have on your car stock is great for low boost applications where your more in tune with keeping the charge air in longer so that it can dissipate the heat better. BUT the draw back is that in stop and go applications you get heat soak. Where you actually MATCH and exceed the inlet charge temp. NO airflow across the core = heat soak in any core. Key is to get it out of there quick and get as much flow thru the core as possible. To put in perspective for you the drag cars we see every day that run at the tracks are more concerned with IC cooling than the radiator. You'll see the IC right up front and the radiator off to the side or parralel to the ground.

 

[Daniel Young]

I'm glad I posted this thread. I appreciate it perfworks, I have learned a great deal about the benefits from adding a fmic. Do you know if Ion or Wagner are taking orders for theirs yet? I'm definetly going to buy a fmic kit.

 

[Kooldino]

it WILL NOT increase turbo lag, but it WILL make throttle response worse.

 

[Daniel Young]

What are you trying to say? That you don't believe in adding a larger fmic. Or are you asking a question? I guess that surely there are other mods to be done to make the throttle more responsive after the addition of the fmic.