JamesyThompson Posted June 16 Share Posted June 16 (edited) Bit of an odd one. 1995 BPU Jap Supra, running in current configuration for years. When the car is started from cold and I take it for a run everything is fine and it boosts strongly as expected to over 1 bar, however boost disappears if you end up in heavy traffic or park the car up for 30 minutes. Opening the bonnet to let the heat out helps when you park it up. So far I've replaced the vacuum lines and ruled out boost leaks, although not sure why that would only be an issue when the engine bay is heat soaked. I've also recently replaced all the VSV solenoids as the IACV went faulty last year and there was no boost from the second turbo, I replaced the EGCV and EBV solenoids as preventative maintenance at the time too. I don't think the issue relates to the pressure tank as there are no issues when there is no heat soak in the engine bay, and I'm only seeing 0.1 or 0.2bar (so does not seem to be an issue with the sequential system). When the issue occurs, If you manage a few miles at a reasonable speed to get some airflow through the engine bay, boost starts to come back, and oddly modulating the throttle around the midrange seems to help boost pick up - albeit to less than usual ( 0.8'ish bar). I've a suspicion the rubber corrugated turbo link pipes might be the issue, collapsing on the inside and choking the intake, more noticeable when the engine bay is hot and the pipes may be more supple: Is there anything else I should be considering? Thanks, Jamesy Edited June 16 by JamesyThompson (see edit history) Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted June 16 Share Posted June 16 It screams electrical to me, heat soak, high resistance. Did you replace with new VSVs or used? The collapsed pipes would be collapsed hot or cold, that isnt the issue. Quote Link to comment Share on other sites More sharing options...
JamesyThompson Posted June 16 Author Share Posted June 16 (edited) I replaced the solenoids with new items, and if it was something electrical related to the sequential system I'd have expected to be seeing 0.6 bar from the first turbo. Suprajake seems to have had the exact same issue I'm having: Partially collapsed hose causing possible turbo issue? Edited June 16 by JamesyThompson (see edit history) Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted June 18 Share Posted June 18 Like I said though, heat wouldn't matter to the collapsed pipes, they'd be be collapsed when cold. Quote Link to comment Share on other sites More sharing options...
JamesyThompson Posted June 18 Author Share Posted June 18 (edited) 10 hours ago, Swampy442 said: Like I said though, heat wouldn't matter to the collapsed pipes, they'd be be collapsed when cold. I’d agree with that for sure, and I’d be starting with the VSV’s if they hadn’t been recently replaced. I’ve replacement link pipes here and will swap them out at the end of the month. I’m hoping the hotter temps might be making it harder for the first turbo to suck in enough air if its link pipe is restricting flow. Will update when I find out! Edited June 18 by JamesyThompson (see edit history) Quote Link to comment Share on other sites More sharing options...
JamesyThompson Posted August 3 Author Share Posted August 3 (edited) Promised I'd update this thread when I pulled the turbo link pipes, and I can confirm they were the cause of my issues. The car is now boosting like an absolute champion and lag is noticeably reduced with the turbos not having to work as hard to create boost. If anyone is having boost issues on their sequentials I'd recommend checking these. Jamesy Edited August 3 by JamesyThompson (see edit history) 4 Quote Link to comment Share on other sites More sharing options...
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