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Old 11-18-2012, 11:49 AM   #1
voltic
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Default FMIC installed, now throttle delay?

Hey guys, I just did a Perrin FMIC install on my 12 STi, and now have a small issue I'm not really sure about. When I'm taking off, it seems like I have to add more throttle than usual, and it feels like there's a short delay. Anyone have any thoughts?

Other than that, I checked all connections and did a log while I drove it around the block. Everything looked good.
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Old 11-18-2012, 11:59 AM   #2
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Turbo lag?

From Unabomber's FMIC FAQ:

What about the additional lag of a FMIC? This topic is highly debated. The two general trains of thought are:
1. FMICs increase turbo lag.
2. FMICs decrease throttle response.
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Old 11-18-2012, 12:07 PM   #3
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Quote:
Originally Posted by findurpath View Post
Turbo lag?

From Unabomber's FMIC FAQ:

What about the additional lag of a FMIC? This topic is highly debated. The two general trains of thought are:
1. FMICs increase turbo lag.
2. FMICs decrease throttle response.

^this
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Old 11-18-2012, 12:08 PM   #4
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Turbo lag bro. The air has to travel much further so there is a slight delay.
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Old 11-18-2012, 12:12 PM   #5
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Quote:
Originally Posted by brutnus View Post
Turbo lag bro. The air has to travel much further so there is a slight delay.
Exactly. Think about using a straw to sip a drink. What if you used a 2' long straw and threw some bends in it also?
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Old 11-18-2012, 12:16 PM   #6
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Granted it will work fine. You can also not have to worry about heat soak. Also if you ever plan on running more boost it won't be a problem.
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Old 11-18-2012, 12:20 PM   #7
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Professionally tuned?
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Old 11-18-2012, 12:46 PM   #8
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Quote:
Originally Posted by findurpath

Exactly. Think about using a straw to sip a drink. What if you used a 2' wide straw and threw some bends in it also?
Fixed it
Width not length
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Old 11-18-2012, 03:59 PM   #9
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Turbo lag is not the correct term.

No variables have changed causing the turbo to spool any slower. The correct term would be delayed throttle response. The air is compressed at the same rate, but the air has to travel a longer distance.
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Old 11-18-2012, 04:26 PM   #10
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Quote:
Originally Posted by subieguy87

Fixed it
Width not length
Both matter. I would've made a bong comparison (may get some points here ) bigger the bong the more fresh air you suck up before you get to the...er...tobacco smoke
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Old 11-18-2012, 04:41 PM   #11
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Quote:
Originally Posted by FLEX'N WRX View Post
Turbo lag is not the correct term.

No variables have changed causing the turbo to spool any slower. The correct term would be delayed throttle response. The air is compressed at the same rate, but the air has to travel a longer distance.
which is just a fancy way of saying turbo lag
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Old 11-18-2012, 04:58 PM   #12
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False... The turbo is not lagging
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Old 11-18-2012, 05:00 PM   #13
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someone else said it... is it tuned for the fmic? my guess would be no
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Old 11-18-2012, 05:01 PM   #14
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Quote:
Originally Posted by FLEX'N WRX View Post
False... The turbo is not lagging
Quote:
Turbo lag is the time required to change power output in response to a throttle change, noticed as a hesitation or slowed throttle response when accelerating from idle as compared to a naturally aspirated engine.
turbo lag
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Old 11-18-2012, 05:07 PM   #15
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You're misinterpreting the variables.

The turbo will naturally have characteristic lag. The lag that the OP is describing is not turbo lag. It is delayed throttle responses from the variable that did change. The longer pipes of the intercooler.

Your quote is irrelavant.
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Old 11-18-2012, 05:07 PM   #16
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Did you reset the ECU? Any time I do this my gas pedal's sensitivity changes. Your issue may be related your your FMIC but the way you describe it sounds exactly like what happens when you reset the ECU.
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Old 11-18-2012, 05:36 PM   #17
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You need a tune for a FMIC to remove the laggy throttle response.
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Old 11-18-2012, 05:52 PM   #18
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Turbo lag when I shouldn't be producing boost? I'm going to guess the delay is just because of the longer piping as some have already said... this is also what I had assumed but wasn't sure. I'm pro-tuned with the stock TMIC, by the way.

It's not going to hurt anything if I run it like this for the next few weeks is it? Trying to delay a new tune until I get the rest of my goodie box under the hood.
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Old 11-18-2012, 05:57 PM   #19
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Quote:
Originally Posted by FLEX'N WRX View Post
You're misinterpreting the variables.

The turbo will naturally have characteristic lag. The lag that the OP is describing is not turbo lag. It is delayed throttle responses from the variable that did change. The longer pipes of the intercooler.

Your quote is irrelavant.
The quote is completely relevant, because it treats turbo lag as a characteristic of the system. Which includes the motor, piping, etc and is based on actual output vs. your metric which isn't really realistic. Which is pretty much the only relevant metric, because a turbo doesn't have lag, it has an inertia and frictional losses. The same turbo in two different applications, will have different lag.
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Old 11-18-2012, 06:47 PM   #20
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Quote:
Originally Posted by voltic
Turbo lag when I shouldn't be producing boost? I'm going to guess the delay is just because of the longer piping as some have already said... this is also what I had assumed but wasn't sure. I'm pro-tuned with the stock TMIC, by the way.

It's not going to hurt anything if I run it like this for the next few weeks is it? Trying to delay a new tune until I get the rest of my goodie box under the hood.
Get a tune... ASAP. You can drive around, but stay off the throttle and out of boost. There's a reason you're feeling this 'delay'. Your fueling is tuned for a TMIC. With the FMIC, boost takes a little longer to get to your engine, so it's creating a 'choppy' section in your power band that can be smoothed out with a tune. Resetting your ECU will not magically fix this...
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Old 11-18-2012, 07:12 PM   #21
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Quote:
Originally Posted by LastResort View Post
The quote is completely relevant, because it treats turbo lag as a characteristic of the system. Which includes the motor, piping, etc and is based on actual output vs. your metric which isn't really realistic. Which is pretty much the only relevant metric, because a turbo doesn't have lag, it has an inertia and frictional losses. The same turbo in two different applications, will have different lag.
Youre on a tangent now...

The quote compares a turbocharged application to a NA application.

The OP described an issue. The relevant parts of the system that alter the spooling characteristics have not been touched. The natural lag associted with the system is still present. The turbo is not lagging anymore than it did prior to his fmic install. To say the cause is turbo lag is incorrect. The culprit is throttle response, and the need for a tune to account for the pressure drop in the system.
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Old 11-18-2012, 07:45 PM   #22
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Quote:
Originally Posted by voltic View Post
Hey guys, I just did a Perrin FMIC install on my 12 STi, and now have a small issue I'm not really sure about. When I'm taking off, it seems like I have to add more throttle than usual, and it feels like there's a short delay. Anyone have any thoughts?
i guess you figured out why a fmic may not be the best idea, didnt ya??
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Old 11-18-2012, 08:13 PM   #23
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Quote:
Originally Posted by Uncle Scotty View Post
i guess you figured out why a fmic may not be the best idea, didnt ya??
Despite my insatiable need for approval from people I don't know, I was looking more for answers as to whether this was a problem or a common thing.
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Old 11-18-2012, 09:08 PM   #24
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Quote:
Originally Posted by Tripintaz View Post
You need a tune for a FMIC to remove the laggy throttle response.
^ This makes me
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Old 11-18-2012, 09:32 PM   #25
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It seems to me throttle response (engine responding to the throttle petal being pushed) and turbo lag (the time it takes the turbo to build boost) are two different things. Is the op complaning about the off boost response or the delay in boost? It does need a tune ether way.
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