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S14 sr20det t28 laggy - Hardtuned.net

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S14 sr20det t28 laggy 

t28 lag
9 replies to this topic

#1 Myles_SR20

  • Joined:15-December 13
  • Location:Australia QLD
  • Car:S14

Posted 20 March 2017 - 02:49 PM

Hey guys, recently took my car to the tuner after my rebuild. The cars a s14 sr20det 9.0 comp with a t28 on 14psi. He started to tune it but realised it wasnt coming on full boost until 4000rpm and it should be there by 3250-3500rpm. Any ideas what would make it lag this much? He mentioned it may be the vtc gear stuck or the cat being blocked. Seems really odd

#2 Scotties15

  • Joined:08-May 05
  • Location:Australia QLD
  • Car:S15 200sx

Posted 20 March 2017 - 08:51 PM

Vct stuck ?

Cas properly timed or aligned?

Blocked cat or restrictive exhaust yes possible.

Could also be split cooler pipe work.
Anything really.
Including the tune.

#3 pmod

  • Joined:13-May 10
  • Location:Australia NSW
  • Car:Fruity 180sx

Posted 21 March 2017 - 08:26 AM

Are you sure the wastegate isn't stuck open to some degree? That will kill response.

#4 chris_c30

  • Joined:29-December 12
  • Location:Australia SA
  • Car:s14a 200sx

Posted 21 March 2017 - 09:30 AM

Pull the exhaust off before the cat, that would rule one problem out

#5 Myles_SR20

  • Joined:15-December 13
  • Location:Australia QLD
  • Car:S14

Posted 21 March 2017 - 11:32 AM

 Scotties15, on 20 March 2017 - 08:51 PM, said:

Vct stuck ?

Cas properly timed or aligned?

Blocked cat or restrictive exhaust yes possible.

Could also be split cooler pipe work.
Anything really.
Including the tune.

Yeah Ive heard of a vct gear wearing out and ticking but never stuck in the retarded position...

Ive aligned the cas correctly, checked multiple times before fitting the rocker cover.

I will have to try putting the back pressure gauge on or removing the exhaust. But was told it wouldnt even make 14psi boost if it was blocked?

Just made a boost leak tester, will have to try it out this arvo.

There was a crack in the turbine housing where the wastegate flapper sealed but didnt think it would make that much of a difference??

Edited by Myles_SR20, 21 March 2017 - 11:33 AM.


#6 wrmdma

  • Joined:28-October 11
  • Location:Australia VIC

Posted 21 March 2017 - 12:37 PM

Can confirm wastegate leak will lead to a very bad time. Fixed my t28bb's kowabunga actuator preload by a couple mm and went from 16psi at 4500rpm to 16psi at 3500rpm plus way better transient response. Prior to finding that I checked for boost leaks, dead vtc, collapsed cat, knock sensor etc. If that crack has enlarged near your wastegate then there's a chance it could be replicating the same effect.

Edited by wrmdma, 21 March 2017 - 01:45 PM.


#7 Scotties15

  • Joined:08-May 05
  • Location:Australia QLD
  • Car:S15 200sx

Posted 21 March 2017 - 08:10 PM

Yeah exhaust leak and actuator problems will cause issues. And same with the crack if its big enuf.

I have a fucked VCT and still in by 4000 with gtx2876 and 260/12 cams. Wouldn't think it's the issue.
Vct won't retard anything. Just make down low a bit sluggish if worn out. And rattle like mofo.

Also check for bolt tightness on turbo, manifold, dump pipe etc etc.

#8 Scotties15

  • Joined:08-May 05
  • Location:Australia QLD
  • Car:S15 200sx

Posted 21 March 2017 - 08:15 PM

Manual boost controller?


#9 blingcommander

  • Joined:05-October 06
  • Location:Japan
  • Car:Scooty-Puff Jr.

Posted 21 March 2017 - 09:07 PM

Yep. Cracked housing is the issue. Had one that did the same. Was shit as

#10 Myles_SR20

  • Joined:15-December 13
  • Location:Australia QLD
  • Car:S14

Posted 23 March 2017 - 06:22 AM

Yeah I have a manual boost controller.

The crack is only about 5mm long, so not very big.





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