I switched my Turbo from the T25 Garrett to a 16g TDO5. I have been having to get my car beyond 3500 RPM before boost actually begins.

Is this a problem or is this normal before boost?

Should it kick in a lot sooner or am I doing something wrong?

Is there something that I am doing incorrectly or do I need different sensors and other components to go along with the turbo swap?

  • 1
    Was the car tuned? Did you do any supporting mods?
    – Ben
    Jun 12, 2016 at 20:17
  • What are supporting mods?
    – Keith
    Jun 13, 2016 at 5:03
  • stuff like fuel injectors or intake/exhaust etc... though it may not be needed in this case. you may just need a tune.
    – Ben
    Jun 13, 2016 at 9:39
  • Do you have a boost gauge? Does this happen in all gears? Has it always been like this, or was it better at some point?
    – rpmerf
    Jun 13, 2016 at 12:21

2 Answers 2


The TDO5 16g flows a lot more air than a T25 (520cfm vs. 405, according to this ), so you should expect it to be laggy. On the plus side, once you get higher in the power band, you should be making more power. If you haven't upgraded your fuel injectors (and possibly your fuel pump) you should keep a close watch on your A/F ratio, as if you exceed your injectors' flow rate you'll run lean and that's not a good thing. You can probably find some good advice on some Eclipse-specific forums.


An otherwise stock 2g Eclipse 4g63 with a 16g is going to be around 3500 RPMs just as you've seen. You really need to get it tuned for the new turbo. To take full advantage you'll also need to upgrade to at least 550 injectors, with some sort of fuel control, and add a boost controller of some sort. Replacing the upper IC pipe is supposed to help some with the lag, but I've never done a before/after test myself on that piece.

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