FST94TSI Posted January 4, 2003 Report Share Posted January 4, 2003 I'm using a stock 1st gen. crushed blow-off valve, and when I let off of the gas it flutters really loud instead of a smooth release. This fluttering sometimes causes the car to feel like it dumps all power in between shifts. Does anyone know what this might be? Quote Link to comment Share on other sites More sharing options...
kenny Posted January 4, 2003 Report Share Posted January 4, 2003 Compressor surge. Quote Link to comment Share on other sites More sharing options...
Turbo Ben Posted January 4, 2003 Report Share Posted January 4, 2003 Sounds like you're getting compressor surge. Are you sure you're not running more boost than the BOV can handle? Quote Link to comment Share on other sites More sharing options...
FST94TSI Posted January 4, 2003 Author Report Share Posted January 4, 2003 How do i go about solving compressor surge? Quote Link to comment Share on other sites More sharing options...
Doug1647545489 Posted January 4, 2003 Report Share Posted January 4, 2003 buy a better BOV Quote Link to comment Share on other sites More sharing options...
nocab72 Posted January 5, 2003 Report Share Posted January 5, 2003 one of two things is happening: 1) your BOV isn't large enough to "release" enough air to prevent compressor surge. 2) your BOX is large enough, but you have it set too tight (try loosening it) BTW: since you probably don't know what compressor surge is, or you would have reconnized the sound, it's what happens after you let off the throttle (closing throttle body, etc) and the boost pressure you have built pushes back against the turbo...that makes the sound you describe as "flutter". Some people say it is bad for the turbo, others say it won't hurt them. Personally I can see how pressure thrusting back against a turbo could benefit the turbo's longevity, so I try to avoid that ugly fluttering sound w/my car... smile.gif K Quote Link to comment Share on other sites More sharing options...
Renner Posted January 5, 2003 Report Share Posted January 5, 2003 Just fyi, some bov's do cause a fluttering noise even when they are not causing compressor surge. You will hear this a lot on some true race cars using a bov with a large displacement spring mounted very close to the throttle body(s). If you have ever watched the Top Gear movie where he test drives the Porsche GT1 around the track, you will hear a perfect example of this. I am pretty sure that Shepard still uses a crushed 1G bov on his race car too, since he says he has no problems with it holding boost correctly. The Greddy R-type is one of the aftermaket ones that will continue to flutter even after the boost has dropped way down, just due to the valve design. Personally, I think it sounds pretty cool. smile.gif Quote Link to comment Share on other sites More sharing options...
FST94TSI Posted January 5, 2003 Author Report Share Posted January 5, 2003 Thanks for the help. I thought that maybe it was compressor surge, but this only started happening after I went from the factory IC to a front mount. I used the same blow off valve with both setups. That is what left me scratching my head. Could changing the intercoolers have caused the blow off valve to work diferently? Quote Link to comment Share on other sites More sharing options...
nocab72 Posted January 6, 2003 Report Share Posted January 6, 2003 Originally posted by FST94TSI: Could changing the intercoolers have caused the blow off valve to work diferently? Extra volume of air in your "compressed system" (due to the larger displacement of the new intercooler) that needs to be expelled via BOV may require BOV adjustment, yes. K Quote Link to comment Share on other sites More sharing options...
FST94TSI Posted January 6, 2003 Author Report Share Posted January 6, 2003 You guys are the shiznizil thanks. Quote Link to comment Share on other sites More sharing options...
20G TSi Posted January 6, 2003 Report Share Posted January 6, 2003 crushing the BOV will hinder flow. You're getting compressor surge - the valve isnt opening as far anymore. How much vacuum does it take to open the BOV? Quote Link to comment Share on other sites More sharing options...
20G TSi Posted January 6, 2003 Report Share Posted January 6, 2003 This is the best explaination of the DSM BOV you'll find. Copied from DSMTALK.com: It is not ONLY the vacuum that opens a bov. It is the pressure differential between the boosted pipe that it mounts on and the vacuum in the manifold. When you are at WOT the manifold line has similar (almost the same) pressure as the UICP. With equal pressure on both sides of the valve it would only require a couple of pounds of spring pressure to hold it closed (it is a game of tug-a-war). However when you go into partial throttle the the TB will create a slight differance in pressure between the UICP and the manifold, it will now require a little more pressure to keep the valve closed. This may cause the BOV to flutter the extra pressure out. When you are coming off of full boost, and allow the throttle to close completely (take your foot off of the gas) the UICP has say 20psi in it while the manifold has 17inhg of vac. This extreme pressure differential easily overcomes the spring pressure, it forces the BOV to suddenly be blown open by the pressure and simultaniously be sucked open by the vacuum. What I am getting at is that it is a combination of the vacuum and boost that operates the BOV. So to crush a valve so that it required 18 PSI of vacuum alone to open the valve would probably hold more boost at closed throttle than desired. A loose BOV will open to oftenly at partial throttle and hurt performance. A BOV that has to much spring pressure will not allow enouph boost out at partial throttle or closed throttle and you will experience a mild to bad case of turbo surge (excessive turbo wear). I am not sure what the actuall desired spring pressure is ( it will varry slightly from car to car) but I prefer my BOV to be a little tight, this will retain more boost in the system in between gears.Find another 1G BOV and do the correct fix: http://www.thedodgegarage.com/turbo_bov_mod.html GL Jason Quote Link to comment Share on other sites More sharing options...
nocab72 Posted January 6, 2003 Report Share Posted January 6, 2003 lol...I thought "crushed" was some crappy brand of BOV I had just never heard of...lol...guess I'm not up on my DSM lingo... K Quote Link to comment Share on other sites More sharing options...
20G TSi Posted January 6, 2003 Report Share Posted January 6, 2003 Originally posted by 100% Rice: lol...I thought "crushed" was some crappy brand of BOV I had just never heard of...lol...guess I'm not up on my DSM lingo... K Yeah, you basically put it in a vice and crush the top of it, increasing the spring pressure. Too much crushy = no worky. Even when done right you get what this guy describes. its the lazy way of making a stock 1G BOV hold boost above 18psi, regardless of results. Quote Link to comment Share on other sites More sharing options...
SupraGlue Posted January 6, 2003 Report Share Posted January 6, 2003 There is also a mod where you can drill a hole in the top and add an adjustment screw. That would seem to me to be a better route than crushing the top. You DSMers are a crazy bunch of MacGyvers, that's for sure. lol I love reading your tech articles. smile.gif Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.