compression ratio 2.8l 30v
08-07-2005, 11:16 AM
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compression ratio 2.8l 30v
i have had this in the back of my mind for some time. has anyone ever tried giving a 2.8 a high compression ratio for more HP? there is a good quality tuning shop near me and i have been thinking about sending my car there to see what they can do. post a reply if you have had any expierence dealing with a high compression ratio and the 2.8 30v engine
07-21-2017, 11:14 AM
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Canned Responses to Boost
So Gentlemen:
I've read and read on boosting all kinds of audi engine configurations. The canned response seems to be: NOT on a 2.8L, NEED Low compression for boost, change your cams, add meth, blah blah bullsheet. Is everyone shilling for the aftermarket auto parts industry?.
Is everyone really building a professional drag Audi, a formula 1 racer or the like? I say, you are likely not going to do it successfully, you are not going to be competitive, and you don't have the capital resources of a racing corporation to do it, test it, and do it so it works.
So, then, why do it? It is possible, cost effective, and safe, apparently to boost a 10:1 compression ratio on pump gas and have a fantastic daily driver, adding an inter-cooler, with few other mods. You up the boost to just before detonation if you like, and you have an inexpensive, nice reliable faster than stock daily driver.
Okay...so I haven't done it, yet. But my infor gathering and clinky thinking tells me this is possible, and many have done it on other cars. Going "low compression" just seems like a sophomoric response to a multi-variable formula without assessing how one really drives and how much is enough extra power. Or, for that matter, what car you currently have.
In addition, going low boost with high compression brings on the power at lower rpm than 3000, which is where most of us really live. Do you really live at 6K rpms every day? I say...no! What good is a super model if you can reliably and comfortably have her when you need her, in bed, where it counts, when you can do it? I feel the same about my street cars.
Tell me why I'm wrong and tell me why I'm right.
If I am right, you can use a low boost application, and get her going sooner , faster, and with less money. As long as you avoid detonation and temp extremes. You avoid the cost of a supercharger, and possibly (just a teaser) you could use an electric supercharger, spooling up in like 200ms, and hit the boost EXACTLY where you want it, at will, with no added heat complications of using exhaust gasses, coking oil as much.
What say you...Audi enthusiast?! I meant no harm in my setup. Just my 2 cents...
I've read and read on boosting all kinds of audi engine configurations. The canned response seems to be: NOT on a 2.8L, NEED Low compression for boost, change your cams, add meth, blah blah bullsheet. Is everyone shilling for the aftermarket auto parts industry?.
Is everyone really building a professional drag Audi, a formula 1 racer or the like? I say, you are likely not going to do it successfully, you are not going to be competitive, and you don't have the capital resources of a racing corporation to do it, test it, and do it so it works.
So, then, why do it? It is possible, cost effective, and safe, apparently to boost a 10:1 compression ratio on pump gas and have a fantastic daily driver, adding an inter-cooler, with few other mods. You up the boost to just before detonation if you like, and you have an inexpensive, nice reliable faster than stock daily driver.
Okay...so I haven't done it, yet. But my infor gathering and clinky thinking tells me this is possible, and many have done it on other cars. Going "low compression" just seems like a sophomoric response to a multi-variable formula without assessing how one really drives and how much is enough extra power. Or, for that matter, what car you currently have.
In addition, going low boost with high compression brings on the power at lower rpm than 3000, which is where most of us really live. Do you really live at 6K rpms every day? I say...no! What good is a super model if you can reliably and comfortably have her when you need her, in bed, where it counts, when you can do it? I feel the same about my street cars.
Tell me why I'm wrong and tell me why I'm right.
If I am right, you can use a low boost application, and get her going sooner , faster, and with less money. As long as you avoid detonation and temp extremes. You avoid the cost of a supercharger, and possibly (just a teaser) you could use an electric supercharger, spooling up in like 200ms, and hit the boost EXACTLY where you want it, at will, with no added heat complications of using exhaust gasses, coking oil as much.
What say you...Audi enthusiast?! I meant no harm in my setup. Just my 2 cents...
07-27-2017, 07:07 PM
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Wilumodmepls,
The problem is detonation. Auto engines run near the ideal air fuel ratio and this that are port injected, throttle body or carb fueled all put that mix into the cylinder prior to compression. Compression raises the temperature of the incoming air and can get it hot enough to cause auto ignition, you know this as knock. Generally, the highest possible compression assuming "normal" outside temps are used for design and the compression ratio is pushed (in high efficiency or high performance apps) to the limit given this criteria. When you add a turbo or blower, you effectively add more compression and this adds additional heat and can put you past the auto-ignition temp. Of course most modern turbo or blower apps have intercolers, but this cannot return the incoming charge to ambient temperature. You usually get at least a 20 degree rise and that translates to nearly 200 of additional compression temp.
You lower the compression ratio to make room to run a higher charge air temp into the engine.
You can google on the various topics of: auto ignition temperature for gasoline, temperature rise from compression, and intercooler design.
Final bit is that if the engine runs direct injection you have more room since you don't have a fuel air mix that is compressed. You only compress air and the fuel is added to time with combustion, kind of quasi diesel like.
The problem is detonation. Auto engines run near the ideal air fuel ratio and this that are port injected, throttle body or carb fueled all put that mix into the cylinder prior to compression. Compression raises the temperature of the incoming air and can get it hot enough to cause auto ignition, you know this as knock. Generally, the highest possible compression assuming "normal" outside temps are used for design and the compression ratio is pushed (in high efficiency or high performance apps) to the limit given this criteria. When you add a turbo or blower, you effectively add more compression and this adds additional heat and can put you past the auto-ignition temp. Of course most modern turbo or blower apps have intercolers, but this cannot return the incoming charge to ambient temperature. You usually get at least a 20 degree rise and that translates to nearly 200 of additional compression temp.
You lower the compression ratio to make room to run a higher charge air temp into the engine.
You can google on the various topics of: auto ignition temperature for gasoline, temperature rise from compression, and intercooler design.
Final bit is that if the engine runs direct injection you have more room since you don't have a fuel air mix that is compressed. You only compress air and the fuel is added to time with combustion, kind of quasi diesel like.
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