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Old 11-11-2010, 08:52 PM   #1
binjoau
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Default TMIC vs FMIC Lag difference???

Hi all,

so just putting together a build and curious if anyone has had direct experience between the spool time on a TMIC (aftermarket) or FMIC?

Hoping for someone doing dyno runs back to back and wondering what difference in rpm you hit full boost at? I know it's different for all turbos but hoping for comparison with a larger turbo.

My car is an 09 WRX and I am using stock heads, Dom3 xtr, APS 70mm Inlet / Intake, walbro 255, 1000cc ID, RAW / Axis stage 3 shortblock.

I am thinking about the ProcessWest TMIC as it can be used with an aftermarket turbo and the build quality seems excellent.

Any thoughts would be great

Thanks
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Old 11-11-2010, 10:00 PM   #2
KpT KiM
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Well I think an FMIC will definitely have a bit more lag and less throttle response, but you'll definitely make more power with an FMIC if that's what you're going for. I think it all depends on the application.
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Old 11-11-2010, 10:20 PM   #3
chuckdez
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I don't know where you are located... If you are in the South the TMIC heat soaks and the FMIC helps out in the summer. Actually my STI felt less responsive with the TMIC in July/Aug with 95+ deg heat and 90% humidity. My intake air temps would get up 170 degrees at a stop light. With the blow-thru FMIC I rarely see over 100 deg on the IAT.
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Old 11-11-2010, 10:32 PM   #4
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Depends on your goals. When I talked to my tuner he said it's not a huge difference but without actually driving it I can't say for sure but when I looked around it was like 200-300 rpm difference. For reference I am running a Dom 3.0r with a TMIC and I feel virtually no lag which kinda makes me want to go front mount because it's hard to notice a couple hundred rpm difference and then you can get more power so it seems worth it, again depends on your goals.
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Old 11-11-2010, 10:38 PM   #5
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I have sat in a sti with tmic and fmic and i felt no difference. If there is any lag.. its barely noticeable but again i don't have any problem daily driving a rotated 35r kit =p.
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Old 11-11-2010, 10:40 PM   #6
chuckdez
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Two key upgrades that eliminated most of lag for me was the Grimmspeed EBCS and blow-thru setup.
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Old 11-11-2010, 10:46 PM   #7
binjoau
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Quote:
Originally Posted by kasra007 View Post
I have sat in a sti with tmic and fmic and i felt no difference. If there is any lag.. its barely noticeable but again i don't have any problem daily driving a rotated 35r kit =p.
Haha! I should imagine not,

the other thing thouugh I am wanting to keep a relative sleeper look. Maybe do something a little different by staying TMIC lol. I am surprised to know there is not much difference between them as far as lag goes.

So to ask another question, do people see much benefit using IC spray systems? Maybe il go with the TMIC and use an IC spray to control temps. My main goal is a street vehicle, less lag is better for my application. It will be dragged occasionally but il take a bag of ice for those days
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Old 11-11-2010, 10:48 PM   #8
binjoau
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Quote:
Originally Posted by chuckdez View Post
Two key upgrades that eliminated most of lag for me was the Grimmspeed EBCS and blow-thru setup.
Yeah I have read lots about the ECBS, I guess as it's not that expensive either for a good benefit il get one.

Excuse my ignorance, blow thru setup?
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Old 11-12-2010, 12:08 AM   #9
kasra007
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Quote:
Originally Posted by binjoau View Post
Haha! I should imagine not,

the other thing thouugh I am wanting to keep a relative sleeper look. Maybe do something a little different by staying TMIC lol. I am surprised to know there is not much difference between them as far as lag goes.

So to ask another question, do people see much benefit using IC spray systems? Maybe il go with the TMIC and use an IC spray to control temps. My main goal is a street vehicle, less lag is better for my application. It will be dragged occasionally but il take a bag of ice for those days

FMIC compared to TMIC won't make your vehicle any less streetable than it already is.

Why don't you sit in a sti with tmic and one with fmic and see if you feel the difference. Plus you always have the FMIC ready incase you plan on doing things big.
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Old 11-12-2010, 12:10 AM   #10
NSFW
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I didn't notice a difference when switching from TMIC to FMIC, back when I had the stock turbo. If there is a difference it's small. I suspect it was more pronounced back when the average turbos for Subarus were tiny, because there's no other way I can explain the anti-FMIC fearmongering that usually appears in threads like these (usually from people who have never driven a FMIC'd Subaru).

"Blow through" = moving the MAF sensor way downstream, putting it between the IC and the throttle body. So the turbo blows through it rather than sucking through it.

See also: http://www.romraider.com/RomRaider/FMICRichDip
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Old 11-12-2010, 12:36 AM   #11
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Quote:
Originally Posted by NSFW View Post
I didn't notice a difference when switching from TMIC to FMIC, back when I had the stock turbo. If there is a difference it's small. I suspect it was more pronounced back when the average turbos for Subarus were tiny, because there's no other way I can explain the anti-FMIC fearmongering that usually appears in threads like these (usually from people who have never driven a FMIC'd Subaru).
+1

Big crybabies
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Old 11-12-2010, 12:59 AM   #12
binjoau
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Quote:
Originally Posted by Nuke209 View Post
+1

Big crybabies

Some say crybabies, others say people looking for knowledge.

Oh and I did go in a FMIC'd WRX and there was noticable lag. I was wondering if a bigger turbo overcomes this.

But thanks, your comment was both constructive and appreciated lol
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Old 11-12-2010, 01:01 AM   #13
binjoau
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Quote:
Originally Posted by NSFW View Post
"Blow through" = moving the MAF sensor way downstream, putting it between the IC and the throttle body. So the turbo blows through it rather than sucking through it.

Is this advantageous because the inlet temperature is more accurate or the air is more stable??
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Old 11-12-2010, 01:03 AM   #14
kasra007
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Quote:
Originally Posted by binjoau View Post
Some say crybabies, others say people looking for knowledge.

Oh and I did go in a FMIC'd WRX and it there was noticable lag. I was wondering if a bigger turbo overcomes this.

But thanks, your comment was both constructive and appreciated lol
Getting a larger turbo would increase your lag even more..you definitely don't want to run a 35r with TMIC

I am the type of guy that looks for high end power / torque. low end power doesn't make me say wow.

What are you goals to begin with?
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Old 11-12-2010, 01:31 AM   #15
NSFW
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Quote:
Originally Posted by binjoau View Post
Some say crybabies, others say people looking for knowledge.

Oh and I did go in a FMIC'd WRX and there was noticable lag. I was wondering if a bigger turbo overcomes this.
Looking for knowledge = people asking questions
Crybabies = people freaking out over FMIC lag like it's a big deal
I see two distinct sets of people there, so I have no idea what you're getting at.

I won't say there's no difference at all, but I will say that I didn't notice it.

What turbo was in that FMIC'd WRX?
Did you ride in it when it had a TMIC?
I mean, how do you know that the FMIC was causing the problem?

If I had a signature on this site, it would be "Correlation is not causation."
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Old 11-12-2010, 01:34 AM   #16
NSFW
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Quote:
Originally Posted by binjoau View Post
Is this advantageous because the inlet temperature is more accurate or the air is more stable??
Check out the link I posted earlier.

But, yes, more accurate temps is a nice side benefit.
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Old 11-12-2010, 01:37 AM   #17
binjoau
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I am not freaking out about fmic lag, I am not knowledgable about the subject and yes maybe I am mis informed about the amount of lag it may cause but again unless i ask i wont ever know the answer.

It was a VF52'd 08 wrx with walbro 255, bigger injectors, inlet, tbe and a fmic. Yes i went in it both times, with tmic and fmic. It just did not seem to pick up as well as before that was all.
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Old 11-12-2010, 01:48 AM   #18
kasra007
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Quote:
Originally Posted by binjoau View Post
I am not freaking out about fmic lag, I am not knowledgable about the subject and yes maybe I am mis informed about the amount of lag it may cause but again unless i ask i wont ever know the answer.

It was a VF52'd 08 wrx with walbro 255, bigger injectors, inlet, tbe and a fmic. Yes i went in it both times, with tmic and fmic. It just did not seem to pick up as well as before that was all.
then rev match to a higher rpm and you will pick up just as much as you did in the sti with TMIC. no high end power? throw in some cams
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Old 11-12-2010, 02:01 AM   #19
berdugo
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whenever I get asked here regarding upgraded TMIC, I always asnwer that I don't recommend any TMIC at all because it's really hot here and we never have any winter. I've seen STIs here with upgraded TMIC but their tuner tells me some "branded" TMIC is worse than the oem STI TMIC thus losing power.

I advise to get a GOOD FMIC kit if the owner wants to upgrade the intercooler. Lot's of people here are paranoid of the "lag" of the FMIC, and lot's of cars here with TMIC gets into a lot of engine troubles sometimes blewn engine but that could be caused of incompetent tuning, of course heatsoak of TMIC will only make matters worse for incompetent tuners.
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Old 11-12-2010, 02:07 AM   #20
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is it the added volume in the fmic piping and the intercooler itself that causes the lag? Are there low volume fmic's that would help reduce lag or would that defeat the purpose?
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Old 11-12-2010, 08:20 AM   #21
binjoau
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Quote:
Originally Posted by boosterseat View Post
is it the added volume in the fmic piping and the intercooler itself that causes the lag? Are there low volume fmic's that would help reduce lag or would that defeat the purpose?

+1 for an answer, I am guessing the more air you have to pressurise the longer it takes and that increases lag. So lower volume = less lag?

Although on the other side if your upgrading the turbo to a higher performance one will this air volume issue be negated due to the turbos ability to spool faster as it has a more efficient design?
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Old 11-12-2010, 09:21 AM   #22
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Quote:
Originally Posted by boosterseat View Post
is it the added volume in the fmic piping and the intercooler itself that causes the lag? Are there low volume fmic's that would help reduce lag or would that defeat the purpose?
That's the theory, and in actuality it does take more time to fill the added volume of the piping and the IC. But if you do the math, the added lag should be largely undetectable. If you add up all of the added volume from piping and larger IC core, you'll find about an additional 2 cubic feet. As the turbo is starting to spool it is flowing a good bit more than 200 cubic feet/minute, or 3.3 cu ft per second. So the added lag time would be less than 2/3 of a second.
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Old 11-12-2010, 02:06 PM   #23
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I don't think the lag from a FMIC is significant in terms of starting at vacuum and hitting full boost.

I think the change in fueling from adding a FMIC to a MAF based system during spool up is significant, especially on a fast spooling turbo. If you want to call that lag, then yes you will feel some lag. If lag to you is just the rate of change of boost pressure over RPM, then no, lag will not increase very much, at least not enough to worry about.

If you look at logs from a stock turbo with TMIC to one with a FMIC, you'll be hard pressed to see a really big difference in spool relative to rpm. It will be small. However if you look at your A/F as you hit peak boost, and compare that to what it was before adding the FMIC, and then time how long it takes to lean out to previous levels, yes it's significant lag. You will feel a dead spot, and you'll notice it even more if you look at a log and watch it happen. If you just stare at the boost gauge and watch the rate of change, you will notice that the range of change is small and convince yourself that adding a FMIC doesn't change the car's performance. But without changes in the MAF table to accommodate the new change in timing from MAF reading to pulsewidth, you'll be slower than before at certain throttle angles.

The faster your turbo spools and the longer the piping the more fueling issues you'll have on spoolup. It's possible to reduce the rich spot--beyond what is tolerable (as it should go rich at peak torque), but I haven't been able to make it go away completely. And I doubt any type of ETUNE would cure it without a significant amount of logs and playing with various throttle angles, but it's possible to do by tweaking a few tables and a lot messing around.

Last edited by reid-o; 11-12-2010 at 02:18 PM.
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Old 11-12-2010, 02:22 PM   #24
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And on a side note, it was this issue (stock turbo FMIC fueling) that made me realize how big real time tuning was to a professional tuner (I'm so not a professional). But I sat in the car years ago thinking...wow...I'd probably be losing money right now trying to make this small blip go away (having to pull over to the side of the road every flash).
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Old 11-12-2010, 05:43 PM   #25
thusimos
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Are you trying to explain this?

http://www.romraider.com/RomRaider/FMICRichDip

"While you canít tune out the rich dip, you can tune around it."

Or you can switch to speed density and completely avoid the issue.
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