Andy Blyth Posted March 27, 2008 Share Posted March 27, 2008 I've spent a while searching for an answer to this but found nothing yet... As I understand it, the boost produced by the first turbo should go up to and hold at 0.7 bar until the engine reaches 4000 rpm when the second spools into play. What I am looking for is a description of how the first turbo comes in, e.g. at what engine speed does it start boosting and by what engine speed does it reach full boost? I ask this because I believe mine is boosting particularly weakly. For example, if I cruise at 2000 rpm in third then open the throttle, there is no spooling sound or movement of the boost gauge until at least 2500 rpm, maybe 3000 rpm. After this the boost increases fairly linearly (although sometimes there are oscillations of around maybe 0.2 bar superimposed on this, intermittent) to around 0.5 bar at 4000 rpm. Of course, after this the second turbo comes online and the boost raises quickly, and peaks at 0.9 bar. For reference, the car has a second decat and a custom 2.5" decat back exhaust. Also, pulsing the throttle with no load on the engine never results in any boost; the BOV makes no sound. BOV operation is normal when driving under load. Am I entirely mad in thinking my car is a little less responsive than it should be? Thanks for any help guys! Quote Link to comment Share on other sites More sharing options...
Jspec Germany Posted March 28, 2008 Share Posted March 28, 2008 Sounds normal to me. Quote Link to comment Share on other sites More sharing options...
bodilx6 Posted March 28, 2008 Share Posted March 28, 2008 error post -sorry Quote Link to comment Share on other sites More sharing options...
TrickTT Posted March 28, 2008 Share Posted March 28, 2008 You dont get boost without load on the engine, but you should start to see positive boost building from 1500 - 2000rpm on load up to about 0.6 bar at 3500rpm. There should be a slight dip as the second turbo prespools, then you should hit full boost (anything up to 1.2 bar depending on spec) by 4500 rpm. Quote Link to comment Share on other sites More sharing options...
Andy Blyth Posted March 28, 2008 Author Share Posted March 28, 2008 You dont get boost without load on the engine, but you should start to see positive boost building from 1500 - 2000rpm on load up to about 0.6 bar at 3500rpm. QUOTE] Thanks TrickTT, I thought the operation should be similar to this. Something I forgot to mention in my post last night is if I spool the turbo up against the brakes (so the engine load is 100%) with an engine speed held to approx. 3000 rpm the boost will top out at 0.5 bar. It takes up to a count of "5 elephant" to get to that level of boost. If I do the same thing at 4000 rpm, the boost will go straight to 0.9 bar (and the pitch change of the turbos is noticably quicker) within about a second or so. Quote Link to comment Share on other sites More sharing options...
Andy Blyth Posted September 13, 2014 Author Share Posted September 13, 2014 It's taken a little while but I believe I've now found the culprit: The Exhaust Gas Bypass Valve is not attached to its actuator, leaving it to flap around and divert exhaust gases away from the first turbo. I've been wondering what that ringing noise when off boost was for years! Quote Link to comment Share on other sites More sharing options...
JamieP Posted September 13, 2014 Share Posted September 13, 2014 Lol, 6 years Quote Link to comment Share on other sites More sharing options...
RobUK Posted September 13, 2014 Share Posted September 13, 2014 Holly post revival! Quote Link to comment Share on other sites More sharing options...
Benjy Posted September 13, 2014 Share Posted September 13, 2014 I've been wondering what that ringing noise when off boost was for years! How have you just continued to live with it!? Lol Quote Link to comment Share on other sites More sharing options...
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