Car feels slower, laggier after FMIC install

[JoeyGST]

I installed my HRC FMIC last night.

The car now feels slower, and laggier. It feels weak in low RPM's,
and picks up a little more in the high RPM's (near redline, so for
practical everyday driving, it kinda sucks).

I also have what appears to be a 2-3psi pressure drop. Is this normal?
I thought there was only supposed to be 1psi drop.

On top of this, running 17psi, I knock like crazy up top now. You can
feel the car yanking back and forth from the ECU pulling the timing.

I'm hoping all this disappears when I play with my Pocketlogger
and tune the car a little.

-JoeyGST

 

[DSMu4ia]

Fix your boost leaks.

Car will feel a little laggier with addition of a FMIC.

 

[JoeyGST]

Originally posted by DSMu4ia
Fix your boost leaks.

Car will feel a little laggier with addition of a FMIC.

What boost leaks? Everything is locked down tight.

Car feeling laggier is normal? Is it actually faster, but feels laggier,
or is it simply slower in low RPM's and a little faster in high RPM's?

 

[CornerHard]

Originally posted by JoeyGST


What boost leaks? Everything is locked down tight.

Car feeling laggier is normal? Is it actually faster, but feels laggier,
or is it simply slower in low RPM's and a little faster in high RPM's?

Did you run an intake leak test, or just wiggle the pipes? Knocking at 17psi w/ FMIC sounds like it might be a boost leak. Pressure drop with a FMIC is normal.

 

[awild]

Simple physics says the pressure drop is normal. You were pushing air through a small SMIC, lets say size X. Now you have a much larger FMIC which is at least 2X. Same air through something bigger = less pressure.

As for you car feeling "laggy" and slower, I'd say theres a boost leak somewhere.

 

[JoeyGST]

Originally posted by awild
Simple physics says the pressure drop is normal. You were pushing air through a small SMIC, lets say size X. Now you have a much larger FMIC which is at least 2X. Same air through something bigger = less pressure.

As for you car feeling "laggy" and slower, I'd say theres a boost leak somewhere.

DSMu4ia just said above that laggier with FMIC is normal. But you're
saying theres a boost leak?

Also, pressure drop is normal, yes, but 2-3psi of drop? I thought it
was just supposed to be 1psi. I think maybe my wastegate
response value isn't set properly on my Apex AVCR boost controller.
I'm gonna fiddle with the car more tonight after work.

Could someone point me to a VFAQ or something on how to do an
intake leak test? Thanks.

 

[DSMu4ia]

You say you are feeling knock. Most likely you are feeling boost leaks.

FMICs add to the lagginess of a turbo.

Boost leaks contribute.

Shitty timing due to boost leaks mess up a car's performance as well.

 

[CornerHard]

If you just go to vfaq.com and look in the Intake section, you'll find the instructions for the tester: http://www.vfaq.com/mods/ICtester.html

These are only $5 or so in parts, and really easy to make. After I did mine, I found my UICP wasn't sealing properly with the intercooler, and my intercooler had two small holes in it!

 

[kpt4321]

First of all, pressure test for boost leaks. I guarantee you have some.

You were pushing air through a small SMIC, lets say size X. Now you have a much larger FMIC which is at least 2X. Same air through something bigger = less pressure.

I don't know where you even came up with this. The air is not flowing out of the turbo at a set rate, the pressure is being regulated by the MBC. The boost pressure should remain very close to the same thing, and it often goes up due to the freer flowing intake tract.

...Kyle T.

 

[Generation X]

I have a large GReddy fmic, and I get about a 1.5 psi in pressure drop. 1.5 psi of pressure drop is about the norm for any fmic, but no more than that. It definitely sounds like you have some type of boost leak somewhere.

 

[DCJ98GST]

Originally posted by Generation X
I have a large GReddy fmic, and I get about a 1.5 psi in pressure drop.

How do you know that? Do you have two boost gauges?

 

[Generation X]

Originally posted by DCJ98GST


How do you know that? Do you have two boost gauges?

No, I don't have two boost gauges . I knew that because of what my previous boost setting was according to my VDO boost gauge, before the fmic install. I had to make up for it by cranking the mbc up another 1.5 psi. Peace!!

 

[KingTSI]

i got a spearco FMIC on my VR4 and i didnt experience any extra lag, then again its a Twin Turbo V6 setup not a single turbo that might make a slight difference...a FMIC is going on my Talon soon, ill let you know the outcome...

 

[DCJ98GST]

Originally posted by Generation X
No, I don't have two boost gauges . I knew that because of what my previous boost setting was according to my VDO boost gauge, before the fmic install. I had to make up for it by cranking the mbc up another 1.5 psi. Peace!!

So you actually you saw a 1.5 psi difference between the stock IC and the Greddy FMIC set up. And your total drop is somewhere above 1.5 psi.

Darn I was hoping you did have two gauges b/c I always wondered what the drop is between the turbo outlet and Manifold pressure for these front mounts.

 

[Generation X]

Originally posted by DCJ98GST


So you actually you saw a 1.5 psi difference between the stock IC and the Greddy FMIC set up. And your total drop is somewhere above 1.5 psi.

Darn I was hoping you did have two gauges b/c I always wondered what the drop is between the turbo outlet and Manifold pressure for these front mounts.

Yes

 

[JoeyGST]

I made the intake leak tester as shown in the VFAQ and tried to test
for leaks, but the system is not pressurizing. I keep pumping air,
but the boost gauge doesn't read any pressure. Is there anything
I should check?

 

[TwoLiterV8Eater]

What are you using to pressurize the system?

 

[JoeyGST]

Ok, first of all, you guys were right.
I have a huge leak by the Jpipe joint to the Big16G outlet.

My gasket was cracked, and the RoadRace Engineering J-pipe was
leaking by the flange welds. I guess in true "Fast and Furious" fashion,
I had blown the "welds on [my] intake".

I put JB weld all over the J-pipe and made a gasket from "Gasket
Material", put RTV on the flange and put it back together. Then when
I started pumping air again, I got about 3psi and no more. I guess I
still have a leak somewhere, but I can't hear any leaks. It may also
still be leaking by the J-pipe, although slower.

I'm pressurizing using a bicycle pump, haha. It takes forever.

Anyone know where I can find the metal gasket that goes on the
turbo outlet? I'm told that it's an obscure part, found only on 1G's?

 

[pneumo]

3psi on a bike pump is OK, but not the greatest. I'll bet you fixed the biggest leak, and all the rest could be leaking out through normal seepage past head, piston rings, PVC valve, etc. Just make sure you give the RTV time to cure before driving.