996 turbo IST
#17
10-16-2014 | 07:36 AM
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Joined: Feb 2011
Posts: 1,075
From: Lewisville, NC
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In the US, we tend to talk about the air fuel ratio instead of Lambda. It's basically the same thing, just on a different scale.
Very simplistically, you would want an a/f ratio of 14.7:1 (14.7 parts air to 1 part fuel) when cruising down the highway, or at idle for great gas mileage when the engine is not under a significant load. For a none turbo car, you can run the engine leaner when under load/full throttle, but still need to be closer to 13.7:1 (13.7 parts air to 1 part fuel). On a turbo car, because of the increased cylinder pressure and heat, you will need to run even richer to stop detonation, so your goal will be around 11.0:1 (11 parts air to 1 part fuel. These are just ball park numbers, but you get the idea.
The octane of the fuel has vary little effect on this number assuming it's gasoline and not ethanol or some other alternative fuel. This is simply how much you have versus fuel you're using.
Here's a good read.
http://www.austincc.edu/wkibbe/lambda.htm
Later, Steve
Very simplistically, you would want an a/f ratio of 14.7:1 (14.7 parts air to 1 part fuel) when cruising down the highway, or at idle for great gas mileage when the engine is not under a significant load. For a none turbo car, you can run the engine leaner when under load/full throttle, but still need to be closer to 13.7:1 (13.7 parts air to 1 part fuel). On a turbo car, because of the increased cylinder pressure and heat, you will need to run even richer to stop detonation, so your goal will be around 11.0:1 (11 parts air to 1 part fuel. These are just ball park numbers, but you get the idea.
The octane of the fuel has vary little effect on this number assuming it's gasoline and not ethanol or some other alternative fuel. This is simply how much you have versus fuel you're using.
Here's a good read.
http://www.austincc.edu/wkibbe/lambda.htm
Later, Steve
Last edited by Steve Jarvis; 10-16-2014 at 07:39 AM.
#18
10-16-2014 | 10:09 AM
Registered User
Joined: Aug 2009
Posts: 650
From: Philadelphia, PA
Rep Power: 106
In the US, we tend to talk about the air fuel ratio instead of Lambda. It's basically the same thing, just on a different scale.
Very simplistically, you would want an a/f ratio of 14.7:1 (14.7 parts air to 1 part fuel) when cruising down the highway, or at idle for great gas mileage when the engine is not under a significant load. For a none turbo car, you can run the engine leaner when under load/full throttle, but still need to be closer to 13.7:1 (13.7 parts air to 1 part fuel). On a turbo car, because of the increased cylinder pressure and heat, you will need to run even richer to stop detonation, so your goal will be around 11.0:1 (11 parts air to 1 part fuel. These are just ball park numbers, but you get the idea.
The octane of the fuel has vary little effect on this number assuming it's gasoline and not ethanol or some other alternative fuel. This is simply how much you have versus fuel you're using.
Here's a good read.
http://www.austincc.edu/wkibbe/lambda.htm
Later, Steve
Very simplistically, you would want an a/f ratio of 14.7:1 (14.7 parts air to 1 part fuel) when cruising down the highway, or at idle for great gas mileage when the engine is not under a significant load. For a none turbo car, you can run the engine leaner when under load/full throttle, but still need to be closer to 13.7:1 (13.7 parts air to 1 part fuel). On a turbo car, because of the increased cylinder pressure and heat, you will need to run even richer to stop detonation, so your goal will be around 11.0:1 (11 parts air to 1 part fuel. These are just ball park numbers, but you get the idea.
The octane of the fuel has vary little effect on this number assuming it's gasoline and not ethanol or some other alternative fuel. This is simply how much you have versus fuel you're using.
Here's a good read.
http://www.austincc.edu/wkibbe/lambda.htm
Later, Steve
Given the contents of post #5, I suspect ghostofpain is conflating two different fuels: high octane (race) gasoline and E85.
E85 is not "race gas" in how these things are typically defined, IMHO.
#19
10-16-2014 | 01:43 PM
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From: Germany
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To be honest, i dont know if these two fuels (E85 and race gas) behave the same way. E85 is dangerous without ECU change. Thats for sure.
Anyway. If you use race gas the ECU should be specified for it too, to gain any power. If you dont, it probably wont hurt the engine, but it will not make you faster. So makes no sense to use it without ECU programed adaption.
Here you can buy 100+ octane gas. The 9ff guys usually specify the ECU for this or even E85. But after that you cannot put any other gas in the car.
The turbo engine is specified for 98 octane gas.
Anyway. If you use race gas the ECU should be specified for it too, to gain any power. If you dont, it probably wont hurt the engine, but it will not make you faster. So makes no sense to use it without ECU programed adaption.
Here you can buy 100+ octane gas. The 9ff guys usually specify the ECU for this or even E85. But after that you cannot put any other gas in the car.
The turbo engine is specified for 98 octane gas.
#20
10-19-2014 | 08:23 PM
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From: Alberta
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Thanks for all the input guys, but I now have bigger problems... bearing noise in the transmission in 5th and 6th gear, waiting to hear back from a couple dealers to see price and availability.
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