The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Morrison Fabrications
Join us at the 2023 Shootout!

Spool problems under heavy acceleration.


10+ Year Contributor
Jul 20, 2012
757, Virginia
Ok, so I installed a FMIC a few weeks ago had a problem with performance and idle and found that I had a boost leak. I installed custom upper inter cooler piping on the car today, and the car operates fine until 10psi roughly unless you slam the pedal to the floor were it seems to want to completely die out and hesitate before making its attempt to high speeds fast.

I have a MBC installed on the car. When the SMIC was installed I had it set to 13psi on the stock T25. I installed a FMIC on my t25 turbo and the boost did not drop, is still steady at 13psi when it is not cutting out. Just out of curiosity I was under the assumption that with a bigger core installed that my boost pressure would drop and have to be adjusted with the MBC after the install.

I did a boost leak test on the car this morning and there were no apparent signs of leaking from any of the pipes, new and old. I will check again in the morning to see if maybe under driving it has developed another one somehow. If this is not the culprit does anyone have an idea of what might be causing this, what I can check for. I am trying my hardest to have everything set up nicely and it seems to be kicking my tail. Thanks for the help and advice guys. Hope to hear some answers.

Another Question:

I looked over vacuum diagrams to see if I have my lines ran correct and so far my understanding is

Vacuum hose runs from manifold to manual boost controller and is also spliced for the blow off valve and runs into the MBC. And then exiting the MBC it is going into the t that connects the waste gate and boost source on turbo. Are they both supposed to be T into the MBC or is the boost source supposed to be blocked off?



15+ Year Contributor
Nov 5, 2007
RIpley, West_Virginia
the boost won't always drop. depends on how the boost controller is setup and what turbo... you're lucky it stayed high on the little tiny turbo sometimes i have seen the smaller turbos give airflow issues due to the volume of air betweeen it and the TB relating to how fast it can fill that volume as well as spooling thus giving issues running correctly due to the air volume being metered but not getting to the TB in the right amount right away..basically the turbo pulls the air, the MAF reads it and ECU adjusts fo it but the slight delay in filling the FMIC and piping causes a stumble in running when making a large transisiton in pedal position (opening from low speed suddenly) this is more common on subarus's in my first hand experience but they are picky as hell even about the intake pipe to the turbo on stock ECU's.... another reason i'm a big fan of speed density, because instead of reading air pulled in at the filter youre reading air pressure and speed at the manifold it's self


10+ Year Contributor
Jul 20, 2012
757, Virginia
That is for sure very valuable information and makes a lot of sense. I can see what you are saying about the core being bigger and causing a delay. I plan to buy a T28 Turbo in the very near future. I got the FMIC as a gift. I was planning to do the turbo then the FMIC but it ended up happening backwards.

A perfect example of what happened I was coming down my street at a slow and moderate pace. I wanted to test the car out to see if it was pulling alright. Nailed the gas, boost spiked up and then car suddenly dropped all power. Seemed to try to pull it back in, but before it was able to I let off of the accelerator because I knew something was at fault, and noticed the idle dropped tremendously to the point that the car tried to stall for a split second. Limped it on home and did a visual check of pipes but it was dark so I said I would check for boost leaks in the morning. When I steadily stay on the gas and let boost build it seems to pull fine to 10psi, I tend to let off after that. No need going higher at regular cruising. Only time I am having the issue is when I punch the gas to get up and go.
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds