First Flex Fuel C7?

[PST]

Or have you already beaten me to it Dave?

Got a local car wired/plumbed up. Turned on the flex fuel stuff in the tune, filled her up with fresh e85 and strapped it to the dyno. She made 40hp more without doing any actual tuning. Ran out of time, so will revisit the car monday and see what can be done in the tune.

[DSteck]

I've had it all since they were out. I have learned to just stay quiet though.

[PST]

Lol, I know you've been really quiet about it. Which made me wonder if you already did one. The hardest part for me was finding the actual wire terminals for the ECM

[LSxpwrdZ]

I've had one on the rollers as well. A 427 stroker with CNC heads and a custom cam with the upgraded lobes for the fuel pump. The stock injectors were enough to feed that engine on E85 which tickled me pink. Can't wait to see a good intake manifold for these cars cause that is the limiting factor on them at the moment.

[PST]

You make a very interesting point James. What makes you say the intake is a limiting factor? I'm sure if it is, that na 427 is finding it.

Also about the injectors, there seems to be quite a bit of room on this car, how much head room are you seeing on the 427 app?
From what I can tell, the stingray apoears to use the middle of 3 injector sizes produced by bosch. My guess is that the zo6 will use the larger set. One can hope that these injectors will support e86 on the zo6.

[LSxpwrdZ]

I've not found a definitive answer on duty cycle yet. Just logging the old duty cycle PID I was seeing 28-29% on this setup which had E70 in it at the time we were tuning it. On gasoline the duty cycle was showing 21%. This is also going to be skewed some from stock because I raised the rail pressure commanded to help combat maxing the injectors out in case they did get close. I ran the rail pressure up around 17.3Mpa

I was seeing a drop of 9-10kpa from 2000rpm up to 7000rpm. This was also on a ported stock intake that we did test and showed to already be 30rwhp better than the OEM stock unit.

[Ben Charles]

James that must be Ben at weapon X's car since he is the only one I know of currently running around in a 427 LT1 lol.

Dave I may give you a shout on the Flex fuel conversion kit for the C7 LT1, love to put one on my 15 A8, being a fellow tuner I need to come up to St Louis some time to meet you since your only a few hours away.

PST any more updates? Your power gains are a lot, is that 40 hp from stock to a tuned E85 car (I can see that)!!

[DSteck]

James that must be Ben at weapon X's car since he is the only one I know of currently running around in a 427 LT1 lol.

Dave I may give you a shout on the Flex fuel conversion kit for the C7 LT1, love to put one on my 15 A8, being a fellow tuner I need to come up to St Louis some time to meet you since your only a few hours away.

PST any more updates? Your power gains are a lot, is that 40 hp from stock to a tuned E85 car (I can see that)!!

Let me know. I have a shitload of money wrapped up in tooling just to be able to make the electrical harness. Lol.

[LSxpwrdZ]

James that must be Ben at weapon X's car since he is the only one I know of currently running around in a 427 LT1 lol.

It is his.

[Bluecat]

The muddy water so to speak on DI duty cycle is because every setup is different on how late you can spray into the compression stroke and still have a uniform enough mixture to burn correctly. However you want to look at, you have from SOI to "sometime" before the spark plug lights. Which relative to the default DC% displayed in HPT, is a matter of us having about a 1/3 of the time to spray vs the whole engine cycle we are used to on a port motor. Which as far as an exact number, both those points obviously are always moving. So (in single pulse mode) a PID of % theoretical max time would be ("Primary Duration" / ("Primary SOI" - "Ignition Timing")). Which doesn't mean shit since spraying any where near 100% of that time frame will result in it miss firing and breaking up.

But it's how ever you want to tackle it. You can keep the default DC% numbers and just know that once you get into the 25-30% range be ready for trouble. I like my displayed DC% to be relative to the max theoretical for DI so that my "window" is atleast framed to something relative. I don't normally log "Primary SOI", but I do keep "Primary Duration" so my over simplified "DI Injector Duty Cycle" PID I use is "([PID.6243] / 315) * 100". 315 is just an arbitrary number i picked because the at rpm the SOI is usually close to 330 and on a boosted LT1 the timing will likely be 15 or less. There is no reason you couldn't get the same data from just the InjPW like the default Injector DC% custom pid. ([SENS.112]*[SENS.70]/1200) * (720/315) should yield the same results if you wanted the 100% to be more relative. But again you can't spray that long anyway, so even with a more relative DC% scale, 65-70% you usually start seeing burn problems. If you wanted you could use 220 as the benchmark if you wanted a shown 100% to be the limit. Regaurdless, 30% Port, 70% DI, 5.5ms PW.... the key is being able to recognize that the injector is spraying late enough that it is a problem. Within the limits of your fuel system, keep the pressure up and the PW down as much as possible.

One of my DI peeve's is people saying that under boost you can't run richer than 12:1 in a DI motor. The problem isn't that a DI motor won't burn a 10-11:1 mixture under boost, its that the stock fuel system won't let you get there at high rpm. Your either are still spraying though the ignition lighting or sprayed so late that the mixture didn't mix and half the chamber is 12:1 and the other part 8:1. That's why the break up at high rpm when they are fat. Lessons learned long ago on DI Ecotec's.

[PST]

PST any more updates? Your power gains are a lot, is that 40 hp from stock to a tuned E85 car (I can see that)!!

To be fair, the pulls were done on different days with similar weather conditions. However, that gain was the result of just switching on the flex stuff without any tweaks to the table. Turned it all on, added pump e85 to an almost empty tank, drove the car around the block gently, then strapped it to the dyno. The alcohol % PID was showing 70% at the time of the pulls.

[yonson]

The muddy water so to speak on DI duty cycle is because every setup is different on how late you can spray into the compression stroke and still have a uniform enough mixture to burn correctly. However you want to look at, you have from SOI to "sometime" before the spark plug lights. Which relative to the default DC% displayed in HPT, is a matter of us having about a 1/3 of the time to spray vs the whole engine cycle we are used to on a port motor. Which as far as an exact number, both those points obviously are always moving. So (in single pulse mode) a PID of % theoretical max time would be ("Primary Duration" / ("Primary SOI" - "Ignition Timing")). Which doesn't mean shit since spraying any where near 100% of that time frame will result in it miss firing and breaking up.

But it's how ever you want to tackle it. You can keep the default DC% numbers and just know that once you get into the 25-30% range be ready for trouble. I like my displayed DC% to be relative to the max theoretical for DI so that my "window" is atleast framed to something relative. I don't normally log "Primary SOI", but I do keep "Primary Duration" so my over simplified "DI Injector Duty Cycle" PID I use is "([PID.6243] / 315) * 100". 315 is just an arbitrary number i picked because the at rpm the SOI is usually close to 330 and on a boosted LT1 the timing will likely be 15 or less. There is no reason you couldn't get the same data from just the InjPW like the default Injector DC% custom pid. ([SENS.112]*[SENS.70]/1200) * (720/315) should yield the same results if you wanted the 100% to be more relative. But again you can't spray that long anyway, so even with a more relative DC% scale, 65-70% you usually start seeing burn problems. If you wanted you could use 220 as the benchmark if you wanted a shown 100% to be the limit. Regaurdless, 30% Port, 70% DI, 5.5ms PW.... the key is being able to recognize that the injector is spraying late enough that it is a problem. Within the limits of your fuel system, keep the pressure up and the PW down as much as possible.

One of my DI peeve's is people saying that under boost you can't run richer than 12:1 in a DI motor. The problem isn't that a DI motor won't burn a 10-11:1 mixture under boost, its that the stock fuel system won't let you get there at high rpm. Your either are still spraying though the ignition lighting or sprayed so late that the mixture didn't mix and half the chamber is 12:1 and the other part 8:1. That's why the break up at high rpm when they are fat. Lessons learned long ago on DI Ecotec's.

Wow, good info as always!

So if I'm interpreting this correctly, using your over simplified DI IDC PID on a boosted LT1, you should keep the DC below 65%?

[Wnts2Go10O]

i thought the C7's were already capable of using e85 O_o

[uarperformance]

The muddy water so to speak on DI duty cycle is because every setup is different on how late you can spray into the compression stroke and still have a uniform enough mixture to burn correctly. However you want to look at, you have from SOI to "sometime" before the spark plug lights. Which relative to the default DC% displayed in HPT, is a matter of us having about a 1/3 of the time to spray vs the whole engine cycle we are used to on a port motor. Which as far as an exact number, both those points obviously are always moving. So (in single pulse mode) a PID of % theoretical max time would be ("Primary Duration" / ("Primary SOI" - "Ignition Timing")). Which doesn't mean shit since spraying any where near 100% of that time frame will result in it miss firing and breaking up.

But it's how ever you want to tackle it. You can keep the default DC% numbers and just know that once you get into the 25-30% range be ready for trouble. I like my displayed DC% to be relative to the max theoretical for DI so that my "window" is atleast framed to something relative. I don't normally log "Primary SOI", but I do keep "Primary Duration" so my over simplified "DI Injector Duty Cycle" PID I use is "([PID.6243] / 315) * 100". 315 is just an arbitrary number i picked because the at rpm the SOI is usually close to 330 and on a boosted LT1 the timing will likely be 15 or less. There is no reason you couldn't get the same data from just the InjPW like the default Injector DC% custom pid. ([SENS.112]*[SENS.70]/1200) * (720/315) should yield the same results if you wanted the 100% to be more relative. But again you can't spray that long anyway, so even with a more relative DC% scale, 65-70% you usually start seeing burn problems. If you wanted you could use 220 as the benchmark if you wanted a shown 100% to be the limit. Regaurdless, 30% Port, 70% DI, 5.5ms PW.... the key is being able to recognize that the injector is spraying late enough that it is a problem. Within the limits of your fuel system, keep the pressure up and the PW down as much as possible.

One of my DI peeve's is people saying that under boost you can't run richer than 12:1 in a DI motor. The problem isn't that a DI motor won't burn a 10-11:1 mixture under boost, its that the stock fuel system won't let you get there at high rpm. Your either are still spraying though the ignition lighting or sprayed so late that the mixture didn't mix and half the chamber is 12:1 and the other part 8:1. That's why the break up at high rpm when they are fat. Lessons learned long ago on DI Ecotec's.

Great info. Thank You for sharing!!