Ian C Posted June 13, 2002 Share Posted June 13, 2002 Zounds. I get my nice Walbro pump in and it works. Now I seem to get overboosting on #1 turbo. All is normal until about 3000rpm. Then the boost starts creeping up and I feel a drop off of power. Everything seems OK at 4000rpm+ but I didn't really push it for obvious reasons! The speed of the creep seems to vary, I had it whip round from 0.7 to 1.0bar in 4th, but creep in 6th to 0.9 over ten seconds or so. WTF? Is it #2 coming online early? I don't think so. Why would #1 go doolally? Why the immediate and noticeable drop in power? No pipes are off, but I haven't checkled for splits (as its 1:30am). Is it fuelling related? I now have UK spec injectors and a fuel pump capable of feeding them. The fuelling is set to overfuel for now (I'm off to see CW about it next week) but is it related to this or should I hold off until I've found out the cause of the problem? Is it a VSV not opening/closing when it should? If it is #1 overboosting, why the power dropoff as soon as boost goes over 0.7 bar? #1 can't be running that close to the edge of it's efficiency! Answers on a postcard to the usual address. Cheers. http://www.ian.chisholm.clara.net/gfx/images/brokencar.gif -Ian Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted June 13, 2002 Share Posted June 13, 2002 maybe I'm being dumb but I'm confused as to the sequence of things..... Start from 0mph and then hit the accelerator... what do you get??? Are you saying as you accelerate #1 boosts up to 1.0bar, then in the transistion when #2 is prespooling it drops to 0.7bar and then with #1 and #2 on line it creeps back up again?? Or something. Sort of like this....??? Sorry but the best I could do... ------------- / / _ / / \_/ / / ---------------- and you are expecting........ ------------- / / / / / / ---------------- Pete. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted June 13, 2002 Share Posted June 13, 2002 Great! That worked......NOT. It stripped out all my leading spaces Ahhhh! Might be that #2 isn't being pre-spooled early enough now due to your mods and #1 is running just over it's efficiency peak and there's a small delay before #2 really kicks in? This is just due to the fueling upgrade isn't it or are you saying it's suddenly happened? Pete Quote Link to comment Share on other sites More sharing options...
Ian C Posted June 13, 2002 Author Share Posted June 13, 2002 Nice drawing I never did it from 0mph. I'm still pussyfooting around the car as the fuelling isn't sorted, but now I have all the kit in place to overfuel. Thinking back on it, what I used to to was ease the throttle open until I'm getting 0.5 to 0.7bar on #1 turbo. Then at 4000rpm I would find that I hadn't got the throttle open enough for any more boost off #2, as I was trying to keep it down to 0.8/0.9 anyway. Now I have the stuff in place fuelling-wise, I might have planted my foot a bit more in building up the boost on #1, and it's suffered boost creep. That means it could have been like this for a while -> BUT, I've never noticed it before even when accidently accelerating hard on #1 I only noticed it after fitting the Walbro pump (and I know it can't e related), so my driving style must have changed enough with a bit more confidence in the car to highlight this issue. Or, something split/fell off/stopped working at a highly coincidental time. It doesn't drop back off to 0.7 in the transition, the boost just behaves as if #2 is online, so it must be #1 overdoing things. It's the noticeable power dropoff that concerns me. -Ian Quote Link to comment Share on other sites More sharing options...
Alex Posted June 13, 2002 Share Posted June 13, 2002 Ian, I'll be at Aarons garage tomorrow...do you wanna bring your car over...we can then compare car behaviour. Though it sounds to me like a wastegate/VSV issue. Anyway I thought you wanted 1bar on the first turbo...that is why I'm making you that valve...(there is a delay on that due to Bob having to do it on the sly at work) Quote Link to comment Share on other sites More sharing options...
Ian C Posted June 13, 2002 Author Share Posted June 13, 2002 Don't need it now! But I did a bit more testing today, and the symptoms have gone more conventional. Going up through the rev range on 0.5bar = OK, pulls strongly as per normal until 4000rpm, then it acts like it's leaking boost sporadically Up through the rev range at full boost (0.7bar) - OK until 3200rpm, then it acts like it's got a really big boost leak, but still sporadic. Like, it will drop the boost to 0.3 or it will flutter the power delivery. Also I noticed a whine coming from the manifold side of the engine under minimal load conditions (blipping the throttle butterfly with head under bonnet listening!) Sound like a split hose to you? -Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted June 13, 2002 Author Share Posted June 13, 2002 Aha - I just had a snout around the engine bay by the manifold, and saw a shiny bit of metal that looked suspiciously like it should have a hose on the end of it... Lo and behold, there was a hose dangling nearby. I've reconnected, but have yet to test. It's the smallest pipe size you get (4 to 5mmish apeture?) and it goes from the throttle body, right near the throttle position sensor (just behind it) to a check valve, to a T junction, to some assorted metal pipework under the manifold. One of these T'd pipes had come off. I think the other T goes to the pressure tank, which would explain why things went screwy, as that tank T's off the feed to the exhaust gas bypass valve, which activates at about 3200rpm... So I'm off out to test it now... -Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted June 13, 2002 Author Share Posted June 13, 2002 Fixed! Hurrah! If in doubt, check your hoses! All of the little blighters... -Ian Quote Link to comment Share on other sites More sharing options...
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