javadoc Posted March 8, 2006 Report Share Posted March 8, 2006 But if you double that at 2 bars boost you get 928 into 109 which is... oh wait.... umm 17:2 Oh you had to do that, didn't you? Link to comment Share on other sites More sharing options...
Che'_Moderator Posted March 8, 2006 Report Share Posted March 8, 2006 Chat room is populated btw. Link to comment Share on other sites More sharing options...
855R Posted March 8, 2006 Report Share Posted March 8, 2006 Is it possible that some of us have got cylinder pressure confused with compression ratio. I'll admit I don't really know a whole lot on this but I do know you can change the cylinder pressure while having the same compression ratio. For example changing valve timing, intake or exhaust will have an effect on CP. So increasing boost levels is in a abstract way like leaving the intake valve open longer and allowing more mass into the cylinder right? If thats the case and you have more pressure inside the cylinder your ignition timing and I suppose octane will need to be adjusted to get the most power with out blowing up. Ok now flame me cause I'm dumb. Link to comment Share on other sites More sharing options...
lax01 Posted March 8, 2006 Report Share Posted March 8, 2006 So let me get this straight twice as much air in the same space, but its not compressed any more. Maybe the compression ratio is not any different but the compression is.what is so hard to understand about this?COMPRESSION RATIO DOESN'T CHANGEDENSITY OF AIR INSIDE THE COMBUSTION CHAMBER DOES CHANGE DUE TO FLOW/EOM Link to comment Share on other sites More sharing options...
Che'_Moderator Posted March 8, 2006 Report Share Posted March 8, 2006 So twice as much air in the same space and it's not compressed any more.Uh huh. Right. So, what's the purpose of a turbo any ways if it doesn't increase the compression?Pardon me but you don't know WTH you are talking aboutOK sick of being nice. Listen up clit trickle while I explain the basic issue here. Compression Ratio C/R is the ratio of volumetric compression. Not mass. If the cyl holds 10 liters, of air and you compress it to 1, you have a C/R of 10:1. If a liter of air weights 1 pound at 1 bar than 10 liters would be 10 pounds. 10:1 still 10 pounds. Ok now two bars. 20 pounds of air into 1 liter.. Yes the density has gone up but that has nothing to do with CR. You still took 10 liters and compressed it to 1 liter. Don't tell me I don't know what I am talking about when you will not listen long enough to realize its a factor of volume not mass. Link to comment Share on other sites More sharing options...
Guest 300+_T5R_855 Posted March 8, 2006 Report Share Posted March 8, 2006 Relative to atmosphere @ 15 psi boost in a 10:1 engine you are 20:1 compression ratio . Relative to volume it is still a 10:1 ratioturbo boost calculator Link to comment Share on other sites More sharing options...
Che'_Moderator Posted March 8, 2006 Report Share Posted March 8, 2006 Relative to atmosphere @ 15 psi boost in a 10:1 engine you are 20:1 compression ratio . Relative to volume it is still a 10:1 ratioCR is only relative to volume. But I have a feeling this is as far from obtuse as you get. At least we all agree now that you cannot change CR with more or less boost. If somone searches hopefully they can learn something from this thread. Link to comment Share on other sites More sharing options...
Guest 300+_T5R_855 Posted March 8, 2006 Report Share Posted March 8, 2006 turbo boost calculator Link to comment Share on other sites More sharing options...
850Nate Posted March 8, 2006 Report Share Posted March 8, 2006 Alright Well Im 15 and cant even drive ,but here I go. Yes there is such thing as running too much octane. Octane has very strong bonds. Stronger bonds = more energy required to separate/Combust it. But more energy is required to speparate there for it can withstand heat/compression of turbo engines or higher compression engines like BMW. So if you put to much octane you engine is gonna have more trouble igniting the gas.So Like anything else octane is all about finding the right balance. The only way to find the right octane for you is try and then try again. Now I have a q for u guys. I have a 95' 850 turbo and plan on doing stage 0. Then a Downpipe, Ignition, Filter and exhaust. Im not getting a ecu/chip/module. I think they sacrafice too much reliability unless you invest some money in internals. Is 93 optimum for my car. Could I see gains by adding maybe a quart of 100 every fill up?Edit: when I say higher compression engines like BMW i mean higher compression ratio. I see some people have not fully graped the concept yet sry bout tht. Link to comment Share on other sites More sharing options...
SkyWriter Posted March 8, 2006 Author Report Share Posted March 8, 2006 and PV = NRT, but that doesn't seem to make a difference either here edit: by the way Scott gave an opinion on the original post: http://forums.swedespeed.com/zeropost?cmd=tshow&id=54810 Link to comment Share on other sites More sharing options...
Guest 300+_T5R_855 Posted March 8, 2006 Report Share Posted March 8, 2006 This sums it up. This is what I am talking about.turbo boost calculator Link to comment Share on other sites More sharing options...
Che'_Moderator Posted March 8, 2006 Report Share Posted March 8, 2006 This sums it up. This is what I am talking about.turbo boost calculatorGood tool. When it asks for standard compession thats C/R which does not change. Link to comment Share on other sites More sharing options...
Guest 300+_T5R_855 Posted March 8, 2006 Report Share Posted March 8, 2006 Good tool. When it asks for standard compession thats C/R which does not change.I didn't explain it well, but compression does change under boost as illustrated by this too. It also illustrates the need for varying octane depending on amount of boost and VE Link to comment Share on other sites More sharing options...
Che'_Moderator Posted March 8, 2006 Report Share Posted March 8, 2006 I didn't explain it well, but compression does change under boost as illustrated by this too. It also illustrates the need for varying octane depending on amount of boost and VEIf you have 10:1 CR at 14.7 atmospheric pressure without boost and you add 15psi boost you in effect have 29.7 absolute psi. This in essence doubles your volume in the same compression chamber. Which increases the CR to 20:1 It is call dynamic compression ratio.Schools out.Did you forget posts 43-80 so quickly. Link to comment Share on other sites More sharing options...
Johann Posted March 22, 2006 Report Share Posted March 22, 2006 This sums it up. This is what I am talking about.turbo boost calculatorCan you get me 107 octane somewhere? Link to comment Share on other sites More sharing options...
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