Kia Forte Turbo Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
1,697 Posts
Discussion Starter · #1 · (Edited)
New thread, but I did not find a better place to ask that question. Unless you think it should be merged somewhere.

Turbo compressor is before cooler, right?
So, if we increase cooler size, we increase its overall capacity as well. In other words, more air volume before throttle body.

Hence, for the pressure to build up, the compressor must work a bit longer to reach same ratio as it would do with stock IC.
As a result, the boost power comes delayed...

Theoretically, we would like to have the distance from the compressor to the intake valves the shortest and the dead volume the smallest, and twin scroll turbo to minimise the time it takes to build up pressure (at low RPM).
Then of course, restrictions come in place when engine speed increases... so we would add larger IC, larger pipes and so on - trade off game.

I was just thinking... FMIC would increase the turbo lag.
 

·
Registered
Joined
·
458 Posts
FMIC would increase the turbo lag

I have a FMIC from 6th element engineering, just purchased and installed last week... I have no leg & no surge. I did with the stock setup.

I'm not sure on the technical / theory end of it.

But this car is night and day difference. You would need to find someone with our car and FMIC and drive it to compare the difference.

6th Element Engineering FMIC Prototype Testing
http://www.forteturbo.org/forum/showthread.php?t=591

6th Element Engineering Front Mount Intercooler Kit
http://www.forteturbo.org/forum/showthread.php?t=789





Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
192 Posts
The biggest factors in lag are pressure drops and resistance to airflow both intake and exhaust side of the turbo impeller. The length of piping, diameter, bend angles, intercooler volume and design, welds etc all play a factor. You want the maximum flow in and out of the turbo. With too large or small an intercooler or overly large/small piping or poor bends it can cause excess pressure drop leading to lag.the location of the intercooler also makes a difference in the cooling ability. That's why it pays to have a kit matched to the flow characteristics of your engine. Check out some of the results from our vendors :)
 

·
Registered
Joined
·
1,697 Posts
Discussion Starter · #4 ·
Check out some of the results from our vendors :)
Yes, I get that. I looked over the dyno tests and while they surely prove extra power, they do not show if there is any additional lag.
Just my thinking is more air to compress so more lag.

It is only a thesis... which I am curious if can be proven correct or wrong.
 

·
Registered
Joined
·
1,697 Posts
Discussion Starter · #5 ·
I have no leg & no surge.
I am sorry for your loss. :D

OK, seriously. No doubt power is there, but does it come a bit later?
Again, I'm just thinking out loud and trying to prove it either way.
 
  • Like
Reactions: lephoenix

·
Registered
Joined
·
192 Posts
Without a doubt too large a intercooler or longer piping can cause increase in lag. I can tell you the twin scroll design of these turbos does more for lag than any intercooler change. My last turbo car was not twin scroll (GM 1.4t LUV motor) and it had the biggest intake with only a 1.5ft run from filter to turbo and a very short path from turbo to FMIC to throttle body due to the turbo being mounted facing forward. It still had more lag than our 1.6 gamma and it used a tiny turbo, it was out of steam by 5k rpm. If you're worried about lag from a FMIC go catless dp and midpipe and that'll cut lag significantly. Plus lower EGTS, quicker spooling, etc.
 

·
Registered
Joined
·
458 Posts
Haha.

No it doesn't come later IMO. Butt dyno only but I'm shocked at how the car responds now. A lot of work by Mr.6 went into his FMIC and it shows so gotta give him credit.
Other vendors have FMIC kits as well but I can't speak to them.



Sent from my iPhone using Tapatalk
 

·
Premium Member
Joined
·
294 Posts
You are going to be adding more piping, and a larger core, there is going to be a slight lag associated with it, really not enough to notice considering the size of the turbos and how quickly they spool, trust me when i say that the benefits greatly outweigh the draw backs. It is going to flow a ton better with less bottlenecking resulting in a greater output of power.
Tyson
 
  • Like
Reactions: PLP

·
Premium Member
Joined
·
1,035 Posts
New thread, but I did not find a better place to ask that question. Unless you think it should be merged somewhere.

Turbo compressor is before cooler, right?
So, if we increase cooler size, we increase its overall capacity as well. In other words, more air volume before throttle body.

Hence, for the pressure to build up, the compressor must work a bit longer to reach same ratio as it would do with stock IC.
As a result, the boost power comes delayed...

Theoretically, we would like to have the distance from the compressor to the intake valves the shortest and the dead volume the smallest, and twin scroll turbo to minimise the time it takes to build up pressure (at low RPM).
Then of course, restrictions come in place when engine speed increases... so we would add larger IC, larger pipes and so on - trade off game.

I was just thinking... FMIC would increase the turbo lag.
You don't know lag until you ride/drive a big single turbo Toyota Supra lol :)

We spent A LOT of time designing our system properly. The results are overall much more favorable vs stock intercooler.

If you look at our development thread:

- we get consistent temperatures of only a few degrees above ambient temp even at the end of long throttle runs through 5th gear. Results the stock intercooler system CAN'T get.
- looking at the CAI dyno vs FMIC dyno, the Torque and Power curves are much broader in scope. Area under the curve is more significant!

As for lag, we didn't bother spending the time on timing throttle response because extra time to charge the extra volume isn't significant given our small turbocharger.
Also, I'd have to go thru my notes again to confirm but if I remember correctly I only counted an extra 16% of additional system volume vs stock. This isn't significant by any means. The dyno confirms this too :)

Let's say we are going to start a race in 3rd gear at 3500 rpm (safe rpm to start). Going back to the intake vs FMIC charts:

It takes a fraction of a second when you hit that throttle pedal to reach full boot at that RPM/gear. By that time we are probably at 4000 rpm. Let's compare intake (Car #1) vs FMIC (Car #2) at that time.

- #1 is making about 190 wheel torque (already at peak) and because of the restrictive stock intercooler, torque begins to fall while power curve starts to plateau just shortly after at 4500 rpm.
- #2 is making slightly more torque here, but had to play catch-up for that fraction of a second while making about 175-180 wheel torque at the start. #1 probably had a slight jump, hard to tell on paper.
- Either way #2 is going to continue to make power after that first second because of the better flowing system. Torque curve doesn't fall nearly as fast for #2, while power has a consistent slope on it's way to peak power made at the same RPM as #1.
- All of this while being significantly higher across the RPM band

Is there lag? Of course there is. A properly designed system minimizes it.
How much is there? I could set up a test and I'd bet the farm time to full boot before/after is less than 1 second.

That point becomes moot as well when tuning comes into play. We can make fuel timing adjustments to make the system spool faster too :)
 

·
Premium Member
Joined
·
139 Posts
New thread, but I did not find a better place to ask that question. Unless you think it should be merged somewhere.

Turbo compressor is before cooler, right?
So, if we increase cooler size, we increase its overall capacity as well. In other words, more air volume before throttle body.

Hence, for the pressure to build up, the compressor must work a bit longer to reach same ratio as it would do with stock IC.
As a result, the boost power comes delayed...

Theoretically, we would like to have the distance from the compressor to the intake valves the shortest and the dead volume the smallest, and twin scroll turbo to minimise the time it takes to build up pressure (at low RPM).
Then of course, restrictions come in place when engine speed increases... so we would add larger IC, larger pipes and so on - trade off game.

I was just thinking... FMIC would increase the turbo lag.
There is a huge misconception with what lag vs turbo spool time. One is based on the size of the turbine area, the other is the time (in seconds) it takes to spin the mass of the turbo. What you are concerned with is the time. The time is the differences because you are filling a larger area with compressed air vs the stock set up. This would not be lag, but this would be turbo spool time (again time as in seconds or minutes it would take to fill the area).

Will a FMIC increase the time it takes to reach full boost? Yes. Is it noticeable by the standard user? No.

Why?

The area increase from stock FMIC to aftermarket is huge, but a turbos ability to fill an air with air is amazing. The actual time difference will be less than .5 of a second. See, boost and volume of air do not go hand in hand. Now, physics will say differently, but when talking about turbos you have to take into account the compressor wheel map and how fast the compressor wheel spins. Last, you have to figure out how efficient the engine behind all this is using the air both cold and hot side. I could do a huge write up on how light weight compressor and turbine wheels effect the time it takes to "spool" the turbo. Then I could dive into the lag of the turbine side and how lag vs rpm vs time plays a part in how the car responds, but most people get lost with the time it takes to spool a turbo, lol. One last thing you have to remember... a turbo pushes air, but the engine sucks air. So, up until the point that the turbo is spinning fast enough to build boost, the sucking of the engine will make up for that. When you put a larger intercooler in the middle, the sucking of the engine doesn't change. Just something to think about.

So, the answer would be... no. A larger intercooler will not impact the time it takes for the turbo to spool (well not enough to notice it).

Hope this helps.
 

·
Registered
Joined
·
1,697 Posts
Discussion Starter · #13 ·
This would not be lag, but this would be turbo spool time (again time as in seconds or minutes it would take to fill the area).

Will a FMIC increase the time it takes to reach full boost? Yes. Is it noticeable by the standard user? No.
That's what I meant, man.

Larger volume to fill although less restrictive to flow, still turbo must compress it. How quickly it does it? I have no clue.

I was simply thinking out loud how the system works, and while I completely understand the extra flow from better intercooler and more power from colder temp, I was wondering if in daily driver, city driving say, the car would feel more powerful in low band only because the compressor will need less time to build up pressure (spool time, as you use the correct terminology) in the smaller system.

If you say 0.5 second - is it much? That's subjective. Well, if currently I need 0.7 second to get full boost would 1.2 second with higher power make really difference? I do not know. Seem like almost 50% longer than stock... (only top of my head numbers - I did not measure anything).


Guys, one thing.

All what I say here is not to deny need for your products or tuning, or else.
I am simply a guy who wants to deeply understand the subject and investigate each option before changing something in his car.
I am a big fan of DIY (with certain limitations when it comes to warranty) with great understanding of physics, chemistry, and some other subjects. I love troubleshooting, hence I ask questions and challenge some subjects.
Nothing is personal. I just want to learn. And you guys help a lot here.
 
1 - 13 of 13 Posts
Top