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No cons as long as it's unleaded. I'd personally just add a gallon or two of E85 to your 93 to boost the octane to 95 for a little additional safety net.
octane is not the issue, It's IAT, which puts the C8 into the low octane Table as long as air is coming through the blades and over the Catylist converters it's going to go to the low tables.
octane is not the issue, It's IAT, which puts the C8 into the low octane Table as long as air is coming through the blades and over the Catylist converters it's going to go to the low tables.
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I'm sorry. I don't understand. Can you explain further.
Running 105 unleaded is not a problem, but you would be better off with something in the 95-100 range. As far as performance goes, a few of us that track the c8 have found that the computer is extremely sensitive to air inlet temperature. When the temperature gets above a certain number the computer will switch from the high timing(octane) to the low (octane) table, which pulls a lot of power from the engine, regardless of what the actual gas octane is.
Main issue is where the air box and MAF are located. The air intakes pull air from the side pods, the air goes through ducts which are located above the exhaust, heating the air. It then goes to the air box which is bolted to the transmission further heating the air, then is measured by the MAF which also tells the computer the temp of the air. Once all that plastic heat sinks the computer thinks you are running on the “surface of the sun” and pulls a noticeable amount of power.
Running 105 unleaded is not a problem, but you would be better off with something in the 95-100 range. As far as performance goes, a few of us that track the c8 have found that the computer is extremely sensitive to air inlet temperature. When the temperature gets above a certain number the computer will switch from the high timing(octane) to the low (octane) table, which pulls a lot of power from the engine, regardless of what the actual gas octane is.
Main issue is where the air box and MAF are located. The air intakes pull air from the side pods, the air goes through ducts which are located above the exhaust, heating the air. It then goes to the air box which is bolted to the transmission further heating the air, then is measured by the MAF which also tells the computer the temp of the air. Once all that plastic heat sinks the computer thinks you are running on the “surface of the sun” and pulls a noticeable amount of power.
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Thank you. Excellent explanation. Any easy way to improve the IAT or fool the computer?
The fuel I have available is VP MS-109. In years past I thought I remembered seeing 105 octane. But I don't see that on the recent cans.
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Thank you. Excellent explanation. Any easy way to improve the IAT or fool the computer?
The fuel I have available is VP MS-109. In years past I thought I remembered seeing 105 octane. But I don't see that on the recent cans.
On your other thread you claimed you were getting peak iat of only 100 degrees. I mentioned you should double check that data.
Iirc you are suffering power loss during high speed events. Before making any changes I'd log the car and see what is really going on and post here or in tech forum.
Logs should includ
Rpm
Vehicle speed
Pedal position
Throttle body opening
Iat
Timing advance
Knk
Torque
Air mass
On your other thread you claimed you were getting peak iat of only 100 degrees. I mentioned you should double check that data.
Iirc you are suffering power loss during high speed events. Before making any changes I'd log the car and see what is really going on and post here or in tech forum.
Logs should includ
Rpm
Vehicle speed
Pedal position
Throttle body opening
Iat
Timing advance
Knk
Torque
Air mass
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The PDR had an IAT of about 98 F for both events. It also recorded a lot of data and none of it was out of bounds. There were no codes set.
But the only conditions under which I have problems are on a 90 degree day after running an average 140 mph for 30+ miles with a lot of heavy late entry breaking and extended runs at 167 mph.
This is a tough scenario to duplicate. Track events and short courses cause no problems.
This opportunity only comes up every six months and costs me $2000+. And I'm trying to win a race.
There is not much room here for data collection. I may never find out what is happening. So if I don't change something in the way I am driving or what the car is doing, the outcome is likely to be the same.
Changing the gas is probably not the solution, but it is on the list of changes I can make and possibly improve the outcome.
I do not know what is causing the car to slow down. The tire temp I mentioned previously is probably a false lead, a red herring, but it is the only event I know about that is common to the times the car decided to slow down.
I have received a lot of good advice and suggestions from experienced forum members. I have a list of all of the ideas and how they could be tried.
GM Engineering and GM Quality have both been going over all the data I collected and the state of the car. They have seen the videos with the data showing the accelerator at 100% for almost 25 miles and the car only going 140 mph.
As of today, they don't have an answer. But they are giving it alot of attention. I provided them about half the data items you suggested from the PDR data. I'm certain they wish they had the rest of the data items.
The GM people I have talked to are very proud of this car. They do not want an outlier anaomaly like this to tarnish the image.
I’m working on a project but it will involve cutting the rear deck
Props. I’m working on a few ideas for this next project myself. Same manner you’re planning. Haven’t rushed it for I want this well thought out. It’s a must for us. Keep us posted if you don’t mind.
Props. I’m working on a few ideas for this next project myself. Same manner you’re planning. Haven’t rushed it for I want this well thought out. It’s a must for us. Keep us posted if you don’t mind.
Most the track guys already know what my NA solution was.... it helped but wasnt the end all be all in terms of IAT's. The map sensor in the intake manifold is still getting temp (IAT3 for those using a scan tool), there comes a point that you can only pull so much heat out. Now i'm battling this to a greater degree with being supercharged and trying to make that survive on track. I made about 4 of these things, 2 were trashed, 1 is on my car and 1 was sent out, never heard if he installed it or not.
Everyone should just buy a Porsche GT3; until this car has a real tuning solution we are throwing crap at a wall, lol.
If it’s the MAP sensor getting heat soaked a solution would be a MAP sensor relocated to a different location. This is done on FI builds on a regular basis. If it’s the MAF, which i was told it was it can be relocated also, but not using the factory style air box.
No problem with mixing in some 105oct for highspeed driving. It is a good idea for track events especially in states that are limited to 91oct. These engines are very knock sensor-centric and knock is the limiting factor.
Most the track guys already know what my NA solution was.... it helped but wasnt the end all be all in terms of IAT's. The map sensor in the intake manifold is still getting temp (IAT3 for those using a scan tool), there comes a point that you can only pull so much heat out. Now i'm battling this to a greater degree with being supercharged and trying to make that survive on track. I made about 4 of these things, 2 were trashed, 1 is on my car and 1 was sent out, never heard if he installed it or not.
Everyone should just buy a Porsche GT3; until this car has a real tuning solution we are throwing crap at a wall, lol.
Tell me what this is doing. What are your results?
I got conflicting sensor info. So does the MAP sensor in the intake get the temp, or is it the MAF?
hahaha, you know as well as me what this answer is because this car is ridiculous... Both. both sensors pull temp. The MAF and the MAP (TMAP) sensor's pull temp.
I know how the tune on the procharged car works, it uses the MAP sensor as its intake air temp to determine which timing table it should use based on temp, it uses this sensor because it is post intercooler. I'm not confident that this is how the normally aspirated car works because the procharged stg 2 car is using the torque tables and what not off of a supercharged Cadillac application, so its definitely reading the car as if it was force induction out of the factory. I have to believe that the NA car is still using that MAP Sensor data to some degree, again you can see the temp from the MAP sensor by looking at "IAT3"
Most the track guys already know what my NA solution was.... it helped but wasnt the end all be all in terms of IAT's. The map sensor in the intake manifold is still getting temp (IAT3 for those using a scan tool), there comes a point that you can only pull so much heat out. Now i'm battling this to a greater degree with being supercharged and trying to make that survive on track. I made about 4 of these things, 2 were trashed, 1 is on my car and 1 was sent out, never heard if he installed it or not.
Everyone should just buy a Porsche GT3; until this car has a real tuning solution we are throwing crap at a wall, lol.
Right!!
But here we are still pushing the platform for every bit of time out of different Motorsports. We all here have got the Motorsports formula. Spend a lot to get a little. Lol. You want to win a million dollars. Start with two.
Running 105 unleaded is not a problem, but you would be better off with something in the 95-100 range. As far as performance goes, a few of us that track the c8 have found that the computer is extremely sensitive to air inlet temperature. When the temperature gets above a certain number the computer will switch from the high timing(octane) to the low (octane) table, which pulls a lot of power from the engine, regardless of what the actual gas octane is.
Main issue is where the air box and MAF are located. The air intakes pull air from the side pods, the air goes through ducts which are located above the exhaust, heating the air. It then goes to the air box which is bolted to the transmission further heating the air, then is measured by the MAF which also tells the computer the temp of the air. Once all that plastic heat sinks the computer thinks you are running on the “surface of the sun” and pulls a noticeable amount of power.
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So, I am running 93 unleaded with ethanol on the first leg of my race. The weather is cool I have never had a performance problem.
At the turn around I put in about 8 gallons of 91 octane. The temperature is now pushing 90.
During the second leg when the intake air temperature hits about 105 is when I see a performance reduction.
Instead of a complete fill with 91 octane, I can buy 5 gallons of MS109 and top it off with the 91 octane.
My blended gas octane calculator says that should be about 98 octane.
Will this keep the knock detector from retarding the timing and reducing the engine performance?
