How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
03-15-2005, 10:03 AM
#11
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
I am not an engine builder but I was told by Mike D'Anabell(spelling) that 100LL av fuel is the next best thing to raceing fuel.Much better than 93 pump fuel. He told me that the lead that was in it, is a great lubricate and that the valves would love it.
I had 598's with 8.75 c/r and ran 9#s of boost. This was actually set up on the dyno to run 91 oct, but AV fuel was easily available so that is what I ran most of time, I did run some straight 93 at times though. Just my experineces. Oh yea, I was turning about 6200RPM.
I had 598's with 8.75 c/r and ran 9#s of boost. This was actually set up on the dyno to run 91 oct, but AV fuel was easily available so that is what I ran most of time, I did run some straight 93 at times though. Just my experineces. Oh yea, I was turning about 6200RPM.
03-15-2005, 11:06 AM
#12
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
Originally Posted by RumRunner
DO NOT USE AV GAS!!!!
DO NOT USE AV GAS!!!!
DO NOT USE AV GAS!!!
Aviation fuel is engineered to run at a lower RPM than standard, or racing gasoline. Most aircraft run at about 3400 RPM Max. It is also designed to run in the thinner atmosphere of altitude. Mixing it with unleaded can actually hurt your performance. I’ve seen many people have problems, and hurt there engines trying to run AV Gas. I have personally done it without any problem, but you have to richen up your mixture to be safe, and then add some lubricants. You’re better off building the engine to run on 89 Octane, and use 93, or add in a little true race fuel.
As far as how much boost you can run with that much compression there are too many variables to answer it with a definitively. Chamber design, Cam selection, porting, headers, head material, ignition timing, and etc. will all play factors. I’ve seen people run as much as 8 lbs of boost on top of 9.5:1 compression. The rest of the engine was built around these factors. Normal cruising however was limited to 4 lbs of boost.
DO NOT USE AV GAS!!!!
DO NOT USE AV GAS!!!
Aviation fuel is engineered to run at a lower RPM than standard, or racing gasoline. Most aircraft run at about 3400 RPM Max. It is also designed to run in the thinner atmosphere of altitude. Mixing it with unleaded can actually hurt your performance. I’ve seen many people have problems, and hurt there engines trying to run AV Gas. I have personally done it without any problem, but you have to richen up your mixture to be safe, and then add some lubricants. You’re better off building the engine to run on 89 Octane, and use 93, or add in a little true race fuel.
As far as how much boost you can run with that much compression there are too many variables to answer it with a definitively. Chamber design, Cam selection, porting, headers, head material, ignition timing, and etc. will all play factors. I’ve seen people run as much as 8 lbs of boost on top of 9.5:1 compression. The rest of the engine was built around these factors. Normal cruising however was limited to 4 lbs of boost.
This is news to me RumRunner. I ran AV in my ProCharged 8.5cr 7.5#'s boost for a couple years. I did'nt have any problems but maybe I was lucky. I know 100's of people on Havasu that fill up weekly with AV. Some use a little Mystery oil in it and others don't. Thanks
03-15-2005, 11:33 AM
#13
Registered
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
The compression ratio vs. boost question comes up a lot because it is a pain to change pistons. But if you were thinking about changing heads and currently have 120cc chambers, many aftermarket aluminum heads can be purchased with 140cc, which is a better way anyhow.
Adding a blower and then restricting yourself to low boost is kind of a poor return on "investment". You might only see a 25% gain, when changing to the proper compression ratio and increasing boost will gain 50% or more depending on blower eff, intercooler eff etc.
Still, I believe everyone should have a blower, so go for it and change the compression at your next rebuild.
Adding a blower and then restricting yourself to low boost is kind of a poor return on "investment". You might only see a 25% gain, when changing to the proper compression ratio and increasing boost will gain 50% or more depending on blower eff, intercooler eff etc.
Still, I believe everyone should have a blower, so go for it and change the compression at your next rebuild.
03-15-2005, 11:38 AM
#14
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
Originally Posted by tomcat
The compression ratio vs. boost question comes up a lot because it is a pain to change pistons. But if you were thinking about changing heads and currently have 120cc chambers, many aftermarket aluminum heads can be purchased with 140cc, which is a better way anyhow.
Adding a blower and then restricting yourself to low boost is kind of a poor return on "investment". You might only see a 25% gain, when changing to the proper compression ratio and increasing boost will gain 50% or more depending on blower eff, intercooler eff etc.
Still, I believe everyone should have a blower, so go for it and change the compression at your next rebuild.
Adding a blower and then restricting yourself to low boost is kind of a poor return on "investment". You might only see a 25% gain, when changing to the proper compression ratio and increasing boost will gain 50% or more depending on blower eff, intercooler eff etc.
Still, I believe everyone should have a blower, so go for it and change the compression at your next rebuild.
03-15-2005, 12:00 PM
#15
Registered
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
"D'Anniballe".....
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
03-15-2005, 02:25 PM
#17
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
Originally Posted by RumRunner
"D'Anniballe".....
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
03-16-2005, 12:13 AM
#18
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Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
Originally Posted by RumRunner
"D'Anniballe".....
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
This information comes from the feedback we've gotten from customers, and from lab information from the fuel manufactures themselves. I know of one guy that ran his boat here on the east coast fine, went to Havasu, put in AV Gas, and burnt it up... Not to say this will always be the case, but I'd be very careful with it. We see street / strip guys hurting engines on a regular basis. I've run both ways, it all depends upon how good you are tuning.
Always be aware of the specific gravity of the fuel you tune with because even if you change brands of fuel with the same octane there can be a big difference in specific gravity. If you look at guys that run big NOS this is one of the most important facts they look at because a little difference means disaster even with the same octane.
Bottom line if you tune with AV gas or blend with it make sure you always do it the same. I have personally never had problems with AV gas if I tuned it with it first.
03-16-2005, 11:27 AM
#19
Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
I think that's the key to it. I always run my boats a little fat. Maybe that's why I had 350hrs on a ProCharged 454mag bottom end. All I did was change heads, intake , and carb, 7.5#s boost. Still running strong.
03-16-2005, 11:44 AM
#20
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Re: How Much Intercooled Boost Can Be Run On 9.5 Comp Ratio
Originally Posted by NOBODY
I think the biggest issue with running AV gas is the specific gravity of the fuel. If you tune your motor for race gas or 93 oct. pump fuel, it has a pretty high specific gravity of usually around .750 and then put in AV gas with specific gravity of lets say .680 you motor will be lean and it will probably melt over a long WO run.
Always be aware of the specific gravity of the fuel you tune with because even if you change brands of fuel with the same octane there can be a big difference in specific gravity. If you look at guys that run big NOS this is one of the most important facts they look at because a little difference means disaster even with the same octane.
Bottom line if you tune with AV gas or blend with it make sure you always do it the same. I have personally never had problems with AV gas if I tuned it with it first.
Always be aware of the specific gravity of the fuel you tune with because even if you change brands of fuel with the same octane there can be a big difference in specific gravity. If you look at guys that run big NOS this is one of the most important facts they look at because a little difference means disaster even with the same octane.
Bottom line if you tune with AV gas or blend with it make sure you always do it the same. I have personally never had problems with AV gas if I tuned it with it first.
