eyefi Posted August 9, 2004 Share Posted August 9, 2004 ive heard this term used in a couple of different situations, can someone confirm its meaning. ive heard it used to describe the sudden stopping or reversing of the compressor when letting off the throttle and also to describe a (usually) low rpm situation where there is not enough gas to spin the turbo correctly. looking at a compressor map i would assume the latter is correct? Link to comment Share on other sites More sharing options...
Ian C Posted August 9, 2004 Share Posted August 9, 2004 Compressor stall is what you first describe. Surge is, I think, when the turbo supplies more air than the engine can ingest, and it backfeeds onto the turbo. I'm not sure of the exact mechanics but it's to do with a turbo design not being compatible with the target engine's air cfm requirements at certain boost pressures and turbine rpms... -Ian Link to comment Share on other sites More sharing options...
MONKEYmark Posted August 9, 2004 Share Posted August 9, 2004 Originally posted by Ian C Compressor stall is what you first describe. Surge is, I think, when the turbo supplies more air than the engine can ingest, and it backfeeds onto the turbo. I'm not sure of the exact mechanics but it's to do with a turbo design not being compatible with the target engine's air cfm requirements at certain boost pressures and turbine rpms... -Ian i was just going to say that too you beat me to it Link to comment Share on other sites More sharing options...
eyefi Posted August 9, 2004 Author Share Posted August 9, 2004 so this occurs below the point a bov will open? Link to comment Share on other sites More sharing options...
eyefi Posted August 9, 2004 Author Share Posted August 9, 2004 Originally posted by MONKEYmark i was just going to say that too you beat me to it it was a real shame u didnt get to say that, it would have been awesome Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 9, 2004 Share Posted August 9, 2004 Originally posted by eyefi so this occurs below the point a bov will open? Yes. Common when unmatched turbos and cams are used. Sometimes unavoidable on race engines with massive WOT air demands that are then asked to have "drivability". Common on twin turbo Skylines with certain mods too. Link to comment Share on other sites More sharing options...
eyefi Posted August 10, 2004 Author Share Posted August 10, 2004 is that only when cams r too small? Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 10, 2004 Share Posted August 10, 2004 No. Usually when a fair amount of overlap occurs with a large turbine exducer size. Link to comment Share on other sites More sharing options...
eyefi Posted August 12, 2004 Author Share Posted August 12, 2004 is there anyway to calculate this or is it just a "black art" thing? do u have to b very near or on the surge line for this cam effect or can it happen anywhere on the map? i suppose im saying how do u match cams to turbos or vica-versa. Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 12, 2004 Share Posted August 12, 2004 Originally posted by eyefi is there anyway to calculate this or is it just a "black art" thing? do u have to b very near or on the surge line for this cam effect or can it happen anywhere on the map? i suppose im saying how do u match cams to turbos or vica-versa. IMHO there are 2 people in the UK who I would trust to *PROPERLY* be able to recommend turbo sizing, and even then, at their own admission, they could only get within a couple of A/R sizes either way, and would expect you to experiment around a recommended sizing. Expensive with twin turbos... It's NOT a black art, but nor is it one where a definitive "best" size can be just given, and be 100% correct. It's a bit like an F1 car suspension. They can design spring and damper rates to be close, and set the cars geometry up within a (tight) ballpark, but then further, on track, experimantation is needed for optimisation. Link to comment Share on other sites More sharing options...
Steven Cordiner Posted August 12, 2004 Share Posted August 12, 2004 If your interested in reading a bit about turbo sizing this was quite good for explaining some of it. Its not a formal technical document but quite good none the less. http://cybrina.mine.nu/MR2_Docs/compressor_flow_maps.htm Link to comment Share on other sites More sharing options...
Adam W Posted August 12, 2004 Share Posted August 12, 2004 Before I bought my turbo I spent a fair few hours looking at turbo compressor maps, working out my air requirements, all sorts of lovely sums In the end though, I bought one that the yanks recommended after I told them when I wanted to hit full boost. I know Chris is pulling a face at this point but there are enough Supras out there with upgraded turbo(s) to figure out which combinations work well with a good degree of accuracy. I checked the unit they recommended against my sums, it all looked sensible, and the turbo works beautifully on my engine. No surge problems at all, boost comes on right where I planned it. Link to comment Share on other sites More sharing options...
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