Max boost for compression
01-25-2008, 12:09 PM
#21
This is exactly what I am talking about. If you look into doing some more research you will find that to run higher boost levels the ideal way is to lower the CR. This also allows you to run on pump gas without detonation.
If you don't believe me and refuse to do more research, start a poll in the FI forum and just ask others in here on what the ideal CR is for a high boosted motor. I garuntee the ones with experience from doing it a while or from learning the hard way from a blown engine will tell you that if you plan on high boost, you don't want a high CR.
Simply stated, high CR + high boost = detonation. You can help your chances of staying away from detonation to a certain extent by raising the octane level, but it will only go so far to help you before detonation cannot be contained.
If you don't believe me and refuse to do more research, start a poll in the FI forum and just ask others in here on what the ideal CR is for a high boosted motor. I garuntee the ones with experience from doing it a while or from learning the hard way from a blown engine will tell you that if you plan on high boost, you don't want a high CR.
Simply stated, high CR + high boost = detonation. You can help your chances of staying away from detonation to a certain extent by raising the octane level, but it will only go so far to help you before detonation cannot be contained.
I run higher compression than most here but its pretty low compared to what a lot of faster cars run. Dont confuse safety with making horsepower, the way you run fast is to run it on the edge - no way around that.
01-25-2008, 12:46 PM
#22
I was mentioning pump gas because most can't afford or have the means to find C16 at the pump every time they're on empty, so its an added bonus of running a lower CR and boost.
When it comes down to it its all about detonation and how close you can come to it without getting it. The higher CR, the more detonation issues you will have to work out, even with C16 at a point. A lower CR can see much more boost and not get nearly as close to detonation. Now, run high boost, with a low CR, AND C16, and you are talking about the most ideal power maker of them all.
01-25-2008, 08:00 PM
#28
Ideal for who? This is about making more power not what makes a more reliable daily driver. No matter what way you want to say it your living in the past. I know it always used to be low CR for boost as a safty net but now that tuners are getting better the faster cars are not using super low boost anymore. Same build, same boost, same gas, the car with higher compresion is going to make more power just like N/A. It may be on the more dangerous side but that's how power seems to work, the more you make, the more risk you take.
01-26-2008, 07:25 AM
#29
Ideal for who? This is about making more power not what makes a more reliable daily driver. No matter what way you want to say it your living in the past. I know it always used to be low CR for boost as a safty net but now that tuners are getting better the faster cars are not using super low boost anymore. Same build, same boost, same gas, the car with higher compresion is going to make more power just like N/A. It may be on the more dangerous side but that's how power seems to work, the more you make, the more risk you take.
High CR with big boost is NOT a good idea. It wasn't in the past, and it isn't now even with race gas. If you think I am alone on this and that I am out of my mind, check out this thread I started just for you non believers on this> https://ls1tech.com/forums/forced-induction/852295-cr-big-boost.html
It specifically asks others on this board what the best CR is for high boost with race gas, and it comes to no surprise to me that everyone so far has voted that it should be a low CR (one guy voted for a high CR but then stated he didn't see the specifics on the thread and wanted to change his vote to low CR).
Last edited by CALL911; 01-26-2008 at 07:30 AM.
01-26-2008, 08:49 AM
#30
anybody wants to make as much horsepower as possible without detonation
if you have not yet come to the detonation threshold but are unable to change cubes, boost, power adder type, ignition... then upping the compression is a way to make MORE power.
look at the article more like HOW compression works with boost w/ supporting math. it is not just telling you more is just better all the time. of course low cr at 20# has less power potential than high cr at 20
for example they didn't go over how the low compression engine was ready to have another 10psi on top of it at the same octane w/out detonation
if you have not yet come to the detonation threshold but are unable to change cubes, boost, power adder type, ignition... then upping the compression is a way to make MORE power.
look at the article more like HOW compression works with boost w/ supporting math. it is not just telling you more is just better all the time. of course low cr at 20# has less power potential than high cr at 20
for example they didn't go over how the low compression engine was ready to have another 10psi on top of it at the same octane w/out detonation
01-26-2008, 09:30 AM
#31
anybody wants to make as much horsepower as possible without detonation
if you have not yet come to the detonation threshold but are unable to change cubes, boost, power adder type, ignition... then upping the compression is a way to make MORE power.
look at the article more like HOW compression works with boost w/ supporting math. it is not just telling you more is just better all the time. of course low cr at 20# has less power potential than high cr at 20
for example they didn't go over how the low compression engine was ready to have another 10psi on top of it at the same octane w/out detonation
if you have not yet come to the detonation threshold but are unable to change cubes, boost, power adder type, ignition... then upping the compression is a way to make MORE power.
look at the article more like HOW compression works with boost w/ supporting math. it is not just telling you more is just better all the time. of course low cr at 20# has less power potential than high cr at 20
for example they didn't go over how the low compression engine was ready to have another 10psi on top of it at the same octane w/out detonation
To be specific, I totally agree with you. Mostly with the last thing you said. You have more potential to run more boost without getting into detonation with a lower CR. However high CR with boost will make more power than that boost level with low CR (I can't argue that fact). I guess to specify I had been trying to say that for a high boost car, even with race gas, you will get more boost without detonation with a low CR vs a high CR.
Now the real specific question. Which would net more power given that both are tuned to the point where detonation is close but not present? A low CR with high boost? Or a high CR with moderate to low boost? I think both may be the same and the variables would be hard to have a definative answer. The facts are that if you max a car out on boost with race gas, and then you increase the CR, you will see detonation.
01-26-2008, 11:58 PM
#32
David, I would consider you a person of great knowledge on this subject given your background. I repect your word over many others, and we have talked in the past.
To be specific, I totally agree with you. Mostly with the last thing you said. You have more potential to run more boost without getting into detonation with a lower CR. However high CR with boost will make more power than that boost level with low CR (I can't argue that fact). I guess to specify I had been trying to say that for a high boost car, even with race gas, you will get more boost without detonation with a low CR vs a high CR.
Now the real specific question. Which would net more power given that both are tuned to the point where detonation is close but not present? A low CR with high boost? Or a high CR with moderate to low boost? I think both may be the same and the variables would be hard to have a definative answer. The facts are that if you max a car out on boost with race gas, and then you increase the CR, you will see detonation.
To be specific, I totally agree with you. Mostly with the last thing you said. You have more potential to run more boost without getting into detonation with a lower CR. However high CR with boost will make more power than that boost level with low CR (I can't argue that fact). I guess to specify I had been trying to say that for a high boost car, even with race gas, you will get more boost without detonation with a low CR vs a high CR.
Now the real specific question. Which would net more power given that both are tuned to the point where detonation is close but not present? A low CR with high boost? Or a high CR with moderate to low boost? I think both may be the same and the variables would be hard to have a definative answer. The facts are that if you max a car out on boost with race gas, and then you increase the CR, you will see detonation.
What's the point of running more boost on a low CR when you could make just as much power on lower boost with the higher CR and be just as safe? Running more boost only leads to other problems like lifting heads, belts slipping and turbos building too much heat. Just like all the other threads about intakes and other N/A factors that can give you more hp power at lower boost, I'll take the most power with the least boost. The up the boost to compensate argument is bull ****.
01-27-2008, 12:23 AM
#33
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What's the point of running more boost on a low CR when you could make just as much power on lower boost with the higher CR and be just as safe? Running more boost only leads to other problems like lifting heads, belts slipping and turbos building too much heat. Just like all the other threads about intakes and other N/A factors that can give you more hp power at lower boost, I'll take the most power with the least boost. The up the boost to compensate argument is bull ****.
01-27-2008, 01:16 AM
#34
What's the point of running more boost on a low CR when you could make just as much power on lower boost with the higher CR and be just as safe? Running more boost only leads to other problems like lifting heads, belts slipping and turbos building too much heat. Just like all the other threads about intakes and other N/A factors that can give you more hp power at lower boost, I'll take the most power with the least boost. The up the boost to compensate argument is bull ****.
01-27-2008, 08:22 AM
#36
you cant compare 'best' compression when airflow is your limit to 'best' compression when octane is your limit.
torque is the stress on an engine, not the boost psi in the intake
01-28-2008, 07:08 AM
#38
I agree that you want to be using race gas if you plan to use the high compression combo. I also said before "ideal" isn't the same for everyone depending on if your car is intended to be a fast DD or a race car you cruise with on the weekends. I use race gas and plan to build my new set-up with that in mind. In my opinion, running higher compresion can give you more power potential. That doesn't mean I think it's a good idea for someone that plans to use pump gas.
