928 engine death.....knock....answer. E85
05-28-2018, 10:42 PM
#16
Nordschleife Master
Here are some relatively readable research results on how gasoline and E85 burn differently inside the engine: https://dspace.mit.edu/bitstream/han...953430-MIT.pdf
05-29-2018, 12:02 AM
#17
Pearson fuels is now distributing e85 through ARCO stations all across SoCal. It’s a no brainer.
Wity the c7 vette and 11.5 compression, it’s almost required for the **** 91 octane.
Wity the c7 vette and 11.5 compression, it’s almost required for the **** 91 octane.
05-29-2018, 05:29 PM
#19
Brendan, I'm not so sure about that. The link below states for recommended fuel - "premium recommended, not required"
C7 Specs
Based upon that, you're good to go with Cali premium.
I hope you're enjoying your C7, it's a beauty!
C7 Specs
Based upon that, you're good to go with Cali premium.
I hope you're enjoying your C7, it's a beauty!
So no - not really good to go. Maybe for the normal grey haired grandpas driving the car to a show and then going back and rubbing it down with baby diapers.
05-29-2018, 11:47 PM
#20
Drifting
Oh man. Ha. No. Yeah, it runs. But the difference between high IATs and lower IATs in the afternoon and evening is clearly noticeable, which of course is because of the knock-limited fuel. I have NO idea how it would even remotely be acceptable to run less than 91. I know for a fact that 93 octane can net more power even in a normal higher compression car. JUST putting the sensor on, hooking up the pin, and enabling the ECU to react to the input gains more than some bolt ons.
So no - not really good to go. Maybe for the normal grey haired grandpas driving the car to a show and then going back and rubbing it down with baby diapers.
So no - not really good to go. Maybe for the normal grey haired grandpas driving the car to a show and then going back and rubbing it down with baby diapers.
To imply a stock Z51 needs E85 is disingenuous at best.
Perhaps something is wrong with your car if you're having problems running premium in your NA Z51 C7.
05-30-2018, 12:03 AM
#21
05-31-2018, 01:36 AM
#22
Common man. I own one. I have driven it more in 60 days than those old farts on cf do in 3 years.
It runs. As I said. It is also consistently fighting detonation and is pulling timing. It is made for 93.
To to be able to drive around in over 75 degree weather (oil temps at above 220 on any drive not cruising) the car needs better octane fuel to not be in a compromised state. Fact.
91 octane is a compromised fuel and cars with high compression or forced induction are worse off running it. Increase the octane by just a few points to 93 and it gets better. E85 opens up worlds of opportunity.
These are are the same forums where they ask questions about what tires to put on so rocks don’t hit the wheel wells. These people would not hear ping if it slapped them in the face first.
It runs. As I said. It is also consistently fighting detonation and is pulling timing. It is made for 93.
To to be able to drive around in over 75 degree weather (oil temps at above 220 on any drive not cruising) the car needs better octane fuel to not be in a compromised state. Fact.
91 octane is a compromised fuel and cars with high compression or forced induction are worse off running it. Increase the octane by just a few points to 93 and it gets better. E85 opens up worlds of opportunity.
These are are the same forums where they ask questions about what tires to put on so rocks don’t hit the wheel wells. These people would not hear ping if it slapped them in the face first.
NOBODY on the Corvette Forum, in all three of the C7-model forums, have complaints with premium. That includes owners of Calloway C7 Z06's with WAY more horsepower than a Z51 C7.
To imply a stock Z51 needs E85 is disingenuous at best.
Perhaps something is wrong with your car if you're having problems running premium in your NA Z51 C7.
To imply a stock Z51 needs E85 is disingenuous at best.
Perhaps something is wrong with your car if you're having problems running premium in your NA Z51 C7.
05-31-2018, 01:41 AM
#23
There is a stop watch in the dash and is triggered by speed. 40-100 is fun on the way to work. 4 gallons of e85 and the rest the **** 91 octane - consistently .2 sec faster at least today. When there is less knock, the ecu is not required to pull timing like it does quite often normally - equals more consistent power.
Most of todays higher performance cars cars are compromised on this crap gas we have here. It’s why so many go to the corn.
Most of todays higher performance cars cars are compromised on this crap gas we have here. It’s why so many go to the corn.
05-31-2018, 08:41 AM
#24
Administrator - "Tyson"
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05-31-2018, 10:55 AM
#25
Nordschleife Master
There is a stop watch in the dash and is triggered by speed. 40-100 is fun on the way to work. 4 gallons of e85 and the rest the **** 91 octane - consistently .2 sec faster at least today. When there is less knock, the ecu is not required to pull timing like it does quite often normally - equals more consistent power. Most of todays higher performance cars cars are compromised on this crap gas we have here. It’s why so many go to the corn.
05-31-2018, 02:58 PM
#26
Does this car have a flex fuel sensor in that it adjust the stoichiometric AFR automatically as you blend ethanol and gasoline? Because if it doesn't, then what might also be going on is that the engine is tuned by factory to run rich at WOT for safety reasons and you're just leaning it out a bit to produce more torque. This would be an especially likely explanation if the ECU doesn't detect knocks with either gasoline or ethanol-gasoline blend.
05-31-2018, 03:13 PM
#27
Nordschleife Master
It wouldn't detect detonation, for example, if the engine isn't actually detonating. It could, for example, have calibration that makes it very conservatively rich and retarded when IAT is high. Too conservatively. I would argue, such that it doesn't knock at all. Hence no detonation detected.
If this is the case, then, with some ethanol blended in, the car goes faster simply because the combustion gets leaner. Suppose that the engine is calibrated to run at AFR = 12, and this makes it too rich with gasoline, as gasoline is stoichiometric (lambda =1) at 14.7 AFR. At AFR 12, it's actually running at lambda 0.82. Suppose that you mix in 20% ethanol with 80% gasoline. Since ethanol's stoichiometric AFR is 9, you'r brew has stoichiometric AFR of about 13.6. Now, you're at lambda = 0.88, which is will likely make more power than lambda = 0.82.
Not saying that this is what's going on, just that it's a possibility. One way to test this hypothesis is to measure the knock counts, one way or another. Another way is to fill it up with high octane gasoline and see if it's still much faster than on 91 octane gasoline. If going from 91 to say 93 octane gasoline doesn't pick up much speed, then it's probably not knock retard that's slowing the car down but the conservatively too rich WOT + high IAT fuel table.
If this is the case, then, with some ethanol blended in, the car goes faster simply because the combustion gets leaner. Suppose that the engine is calibrated to run at AFR = 12, and this makes it too rich with gasoline, as gasoline is stoichiometric (lambda =1) at 14.7 AFR. At AFR 12, it's actually running at lambda 0.82. Suppose that you mix in 20% ethanol with 80% gasoline. Since ethanol's stoichiometric AFR is 9, you'r brew has stoichiometric AFR of about 13.6. Now, you're at lambda = 0.88, which is will likely make more power than lambda = 0.82.
Not saying that this is what's going on, just that it's a possibility. One way to test this hypothesis is to measure the knock counts, one way or another. Another way is to fill it up with high octane gasoline and see if it's still much faster than on 91 octane gasoline. If going from 91 to say 93 octane gasoline doesn't pick up much speed, then it's probably not knock retard that's slowing the car down but the conservatively too rich WOT + high IAT fuel table.
Last edited by ptuomov; 05-31-2018 at 06:54 PM.
06-06-2018, 02:27 AM
#28
Three Wheelin'
With lots of recent discussion about blown race 928 engines it makes me question fuel? E85 has an octane rating above 110 and is nearly impossible to knock. Sure your fuel system must flow around 30% more to support it, but given its cost is well under $3 per gallon and high octane race fuel is over 10 it seems like a viable option for racers, especially those running boosted 928’s
an example a friend has an Apha-N GTR with its twin turbo 3.8L v6. On street 91 it makes 870 awhp....on 100 octane race gas it makes 1040awhp....on e85 it makes 1135awhp.....nice 30% boost on e85 with zero worries about knock... i believe George’s ORR racer is above 500whp now...... not sure what fuel he runs, but 650whp on e85 surely will go faster....assuming his fuel cell holds enough to make it the distance...
i experienced knock on casper, running 91 octane Sunoco at 9-1 cr at 34’ timing around torque peak.....I thought it was a miss.....tried adding fuel...nope....once I got smart and turned spark down at torque peak it ran great....better than ever.....I just wonder how much damage I did while figuring it out.....the engine did run fine for a few more events.. live and learn I guess.... the stand alone ecu on Casper allows unlimited tuning of spark-fuel every 250rpm. Yes it runs crappy at idle and part throttle....but sings at wot
sure I don’t have a dog in this fight as I don’t own a race car now....but if I did I would seriously consider upgrading fuel system and running e85 just to eliminate a well documented failure issue..... e85 costs 70% less that race fuel, but you burn 30% more...well worth it i’d say.....even if your burn rate is 20-25 gallons per hour.....it’s cheap insurance.....Casper at 265whp burned around 10-12 per hour....at track prices of $8...let’s call that $100 per hour. The e85 much more powerful race is around $60 per hour...Casper power level would be at most 16 or $50 per hour.
I recall gt3 cups at the 25hour fueled once per hour....with a 100L cell.....I was told they burn 20 gallons per hour of 100 octane....easy $200 per hour fuel. Nobody said racing was cheap
an example a friend has an Apha-N GTR with its twin turbo 3.8L v6. On street 91 it makes 870 awhp....on 100 octane race gas it makes 1040awhp....on e85 it makes 1135awhp.....nice 30% boost on e85 with zero worries about knock... i believe George’s ORR racer is above 500whp now...... not sure what fuel he runs, but 650whp on e85 surely will go faster....assuming his fuel cell holds enough to make it the distance...
i experienced knock on casper, running 91 octane Sunoco at 9-1 cr at 34’ timing around torque peak.....I thought it was a miss.....tried adding fuel...nope....once I got smart and turned spark down at torque peak it ran great....better than ever.....I just wonder how much damage I did while figuring it out.....the engine did run fine for a few more events.. live and learn I guess.... the stand alone ecu on Casper allows unlimited tuning of spark-fuel every 250rpm. Yes it runs crappy at idle and part throttle....but sings at wot
sure I don’t have a dog in this fight as I don’t own a race car now....but if I did I would seriously consider upgrading fuel system and running e85 just to eliminate a well documented failure issue..... e85 costs 70% less that race fuel, but you burn 30% more...well worth it i’d say.....even if your burn rate is 20-25 gallons per hour.....it’s cheap insurance.....Casper at 265whp burned around 10-12 per hour....at track prices of $8...let’s call that $100 per hour. The e85 much more powerful race is around $60 per hour...Casper power level would be at most 16 or $50 per hour.
I recall gt3 cups at the 25hour fueled once per hour....with a 100L cell.....I was told they burn 20 gallons per hour of 100 octane....easy $200 per hour fuel. Nobody said racing was cheap
Good info here. My own information along this line is that alcohol is good. When I was building my 6.5L about 10 or so years ago, I wanted safety from detonation and of course more power. I built a alcohol injection system to spray 200 proof ethanol into the air intakes for my ITB intake. I used water mister nozzles to atomize the alcohol. The type nozzles as used in greenhouses to evaporate water for cooling and increased humidity. Each nozzle has a check valve inside so alcohol won't dribble out of the lines and leave you with empty lines when you need the alcohol. I set the ECU to output a control to turn on the pump when I was at more than 75% throttle opening. The pump puts out 60 psi pressure to the nozzles. I had to set the ECU to output less gasoline at above 75% throttle too to keep the overall mixture to around 9:1 IIRC. The amount of alcohol injected was not critical at all. Just have enough. I found that the most power increase came from advancing the timing. I think I went to 6 degrees more advance when the alcohol was on. I had a consistent 545 rwhp on 92 octane gasoline and 595 to 603 rwhp with alcohol. It works reliably. This way I can have the benefits of alcohol when I need it and keep 100% gasoline for good starts and smooth cool weather operation. I used ethanol because it has less corrosive tendencies than methanol. For some more fun, use a mixture of 50% alcohol and 50% nitropropane. or propylene oxide.
Stainless steel lines are for the alcohol spray above the air inlets.
06-08-2018, 01:53 AM
#29
Rennlist Member
Louie,
Great information from you as well.
Where do you source nitro propane or propylene oxide from?
Do you still build 928's for racing? If so, are any of your creations for sale?
Regards,
Dave
Great information from you as well.
Where do you source nitro propane or propylene oxide from?
Do you still build 928's for racing? If so, are any of your creations for sale?
Regards,
Dave
06-08-2018, 03:42 AM
#30
Three Wheelin'
Nitropropane is available from Klotz. http://www.klotzlube.com/power_additives.html
I see that they don't show nitropropane as a separate item for sale. I think I had to call them to get it. They do have something calledNitro Power Additive with Koolinal. It is 50% nitropropane and 50% of knock suppressant and cooler. The knock suppressant (koolinal) is probably mostly alcohol. Nitropropane is a knock enhancer which you don't want. The alcohol should take care of that problem. Ethanol is about 106 - 108 octane by itself.
I'd suggest trying their Nitro Power Additive first.
You'll have to search for propylene oxide. I can't remember where I got mine. It was expensive at around $100 for a gallon.
It has been probably 10 or more years ago when I was experimenting with this. Either Nitropropane or propylene oxide full strength will melt/soften normal fuel lines so check that first.
I don't build 928s for racing. I am considering selling my '90GT with the good 6.5L engine and a ton of other things. It is really a 928 engine made for the track with track mods done to the car with no creature comforts removed.
Louie