Flex Fuel
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Me, yes and yes.
I have a ZZP fuel cam & stock LPFP, and run E48ish doing 30 minute HPDE sessions.
You'll obviously need a tune, but even with stock fueling you can run E30. The acceleration difference between 93 and E blend really has to be felt to be appreciated.
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Stock vs 93 tune only is a dramatic difference. If you have experience with that, you know. Going from 93 tune to E60-70 tune (max out the stock turbos) is just as dramatic of a difference. Each upgrade adds about 100 whp onto the lower power setup. If you’re not going to run fueling mods you’ll be limited to about E30. That will get you a noticeable upgrade in power though. From what I’ve seen a 93 tune will put you just under/around 500 whp. E30 will put you low/mid 500s. E60 will get you in the low 600s.
Also mixing gas and E to get your desired blend is super easy. I originally thought it would be a pain but it really isn’t at all. I purchased an ethanol test kit and there are several ethanol calculators and apps available for free on your phone. When I first started using E85 I used my test kit to check the fuel at my local stations several times. They were all about E77-78 every time. Now I just use my ethanol calculator and I get within 2 points of my desired mix each time. You will also require a gauge or a laptop/tablet with hp tuners to read your ethanol percentage after each fill up so you know what exactly is in your tank. That is a requirement to run ethanol so add it to your list in addition to the flex fuel kit.
I say it is definitely worth it if you have a few E85 stations near your house. I happen to have 3 in the city I live and I have no complaints about lack of fueling. I also recently did a 4 hour trip in my car and I was able to plan where I stopped for E85 along my route. I didn’t have to go out of the way at all.
My car has full supporting mods to run E60+. I have a flex fuel tune and a full send E60+ tune. On the flex fuel tune you can feel the car picks up some spice around E30-40 vs 93 octane. Once you hit E50-60 you pick up even more spice. Then the full send E60 tune is a quite a bit more spice than the maxed out flex tune. I believe my whp numbers with the flex tune range from 470 with E0 (so pump 93 with no ethanol what so ever) to 570 at E75.I’m not sure if the hp progression as E content rises is linear or exponential but it feels pretty linear. The full send E60+ tune is about 620 and makes the flex tune feel like child’s play even with E65 in the tank.
I have 11” wide wheels and 305s on the back and they can manage everything the flex tune can provide pretty well when already rolling. Not so much with the full send tune, I spin all way to 60-65mph at times. If the tires are warmed up real well maybe only until about 50 mph.
Lastly ethanol absorbs moisture. If your car sits a lot you’re gonna have problems. Your injectors or anything else fuel system related could clog up and the fuel can start to separate. As far as ethanol “gumming up” my test kit does show that for sure, it’s all kinds of sticky from not being cleaned and sitting around. If you drive the car frequently and keep the fuel level high to deter moisture absorption you’ll likely be fine. You can always add Stabil to your gas tank to help with that as well. As far as the fuel system/rubber being capable of handling ethanol fuel…many guys have been running ethanol for years without issue. If you want to be extra safe run a tank of 93 through the car every so often to flush things out.
That’s all the basic numbers and real life advice from my own research and first hand experience.
Also mixing gas and E to get your desired blend is super easy. I originally thought it would be a pain but it really isn’t at all. I purchased an ethanol test kit and there are several ethanol calculators and apps available for free on your phone. When I first started using E85 I used my test kit to check the fuel at my local stations several times. They were all about E77-78 every time. Now I just use my ethanol calculator and I get within 2 points of my desired mix each time. You will also require a gauge or a laptop/tablet with hp tuners to read your ethanol percentage after each fill up so you know what exactly is in your tank. That is a requirement to run ethanol so add it to your list in addition to the flex fuel kit.
I say it is definitely worth it if you have a few E85 stations near your house. I happen to have 3 in the city I live and I have no complaints about lack of fueling. I also recently did a 4 hour trip in my car and I was able to plan where I stopped for E85 along my route. I didn’t have to go out of the way at all.
My car has full supporting mods to run E60+. I have a flex fuel tune and a full send E60+ tune. On the flex fuel tune you can feel the car picks up some spice around E30-40 vs 93 octane. Once you hit E50-60 you pick up even more spice. Then the full send E60 tune is a quite a bit more spice than the maxed out flex tune. I believe my whp numbers with the flex tune range from 470 with E0 (so pump 93 with no ethanol what so ever) to 570 at E75.I’m not sure if the hp progression as E content rises is linear or exponential but it feels pretty linear. The full send E60+ tune is about 620 and makes the flex tune feel like child’s play even with E65 in the tank.
I have 11” wide wheels and 305s on the back and they can manage everything the flex tune can provide pretty well when already rolling. Not so much with the full send tune, I spin all way to 60-65mph at times. If the tires are warmed up real well maybe only until about 50 mph.
Lastly ethanol absorbs moisture. If your car sits a lot you’re gonna have problems. Your injectors or anything else fuel system related could clog up and the fuel can start to separate. As far as ethanol “gumming up” my test kit does show that for sure, it’s all kinds of sticky from not being cleaned and sitting around. If you drive the car frequently and keep the fuel level high to deter moisture absorption you’ll likely be fine. You can always add Stabil to your gas tank to help with that as well. As far as the fuel system/rubber being capable of handling ethanol fuel…many guys have been running ethanol for years without issue. If you want to be extra safe run a tank of 93 through the car every so often to flush things out.
That’s all the basic numbers and real life advice from my own research and first hand experience.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Thanks for all the info. So if I install a fuel cam, LPFP is just padding but I will likely do this too. Then the flex sensor and a tune? I assume the flex tune will work with either 93 or E at whatever percentage it ends up at? Also, the full 'send it' tune sounds nice, will that flex to low E as well as E60?
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BoilerUp is pretty accurate with those expectations. Whatever you decide to go with talk to your tuner first and see what he can offer you/recommends based on the upgrades you choose. Things to know are 1) ZZP offers a fuel cam with a much larger lobe than Tapout offers. If you go with ZZP do not upgrade the HPFP internals because the cam will overdrive the internals and those internals will fail. 2) Tapout may be offering a stage 2 LPFP soon so if that interests you I’m sure they could shed more light on that if you ask. The stage 2 pump should let you run full E85 with Tapout’s cam and HPFP upgrade.
My vehicle has Tapout cam, HPFP internals and LT4 LPFP (stage 1). My max E content is E75 but E70 is a very common max with that setup. Honestly there’s not really anything to gain hp wise after E60 so a max of E70 is plenty.
To answer your questions, 1) the high side runs out of room first and the LPFP upgrade is to “prop up” the fuel system as a whole. Just keep in mind the low side feeds the high side so I wouldn’t neglect either. They work in tandem. 2) The flex fuel tune will cover straight 93 to whatever your max E content is for your setup. The more E in your tank the more hp you’ll have on tap. The tune will automatically adjust to the E content. 3) The full send tune is designed for max timing and max boost. In my car that requires at least E60 in the tank to support the timing and boost the ECM is commanding. If I have less than E60 in my tank with that tune I risk full sending my motor to the junkyard. Again, in my case my max E content is E75. So I require E60-75 for the full send tune, no other blend of fuel would be adequate for that tune.
Just be aware It’ll take 2-3 miles of driving for your fuel to mix and your flex fuel sensor to accurately adjust and read your most recent fill up regardless if you’re on the flex tune or full send tune. Do not drive the car hard until you’ve driven a few miles, your fuel levels out and your ECM is properly reading the fuel blend that is actually in the tank.
My vehicle has Tapout cam, HPFP internals and LT4 LPFP (stage 1). My max E content is E75 but E70 is a very common max with that setup. Honestly there’s not really anything to gain hp wise after E60 so a max of E70 is plenty.
To answer your questions, 1) the high side runs out of room first and the LPFP upgrade is to “prop up” the fuel system as a whole. Just keep in mind the low side feeds the high side so I wouldn’t neglect either. They work in tandem. 2) The flex fuel tune will cover straight 93 to whatever your max E content is for your setup. The more E in your tank the more hp you’ll have on tap. The tune will automatically adjust to the E content. 3) The full send tune is designed for max timing and max boost. In my car that requires at least E60 in the tank to support the timing and boost the ECM is commanding. If I have less than E60 in my tank with that tune I risk full sending my motor to the junkyard. Again, in my case my max E content is E75. So I require E60-75 for the full send tune, no other blend of fuel would be adequate for that tune.
Just be aware It’ll take 2-3 miles of driving for your fuel to mix and your flex fuel sensor to accurately adjust and read your most recent fill up regardless if you’re on the flex tune or full send tune. Do not drive the car hard until you’ve driven a few miles, your fuel levels out and your ECM is properly reading the fuel blend that is actually in the tank.
Regarding fuel system mods, especially for the M6 cars-- my car was closing the throttle in the low to mid 3000rpm range because of fuel rail pressure drops and that was with a super mild lower boost 91 octane tune. It was very obvious and you could feel it as well as see it on the data logs. Ended up changing the tune slightly to bring the extra boost in at a higher RPM until I upgraded the fuel system to make up for the lack of stock fuel system capacity around that lower RPM range.
Rail pressure drop with the stock fuel system in the 3000rpm range is more of an issue for M6 cars as you can stand on it at a low RPM in a higher gear and the transmission won't automatically downshift and the engine has to pull through that lower RPM range where the volume of the stock fuel system is inadequate to support a tune. With an A8 car, the transmission would downshift (unless you're in manual mode) as soon as you put your foot in it and once the RPMs come up and the engine is out of that lower RPM range where the stock fuel system is inadequate.
Running the fuel system on the ragged edge is asking for trouble IMO; personally, I wouldn't do any tune without a fuel cam and LPFP upgrade so there's no risk of running lean anywhere in the RPM range. After I installed a Tapout fuel cam and ZL1 LPFP there were no more rail pressure drops around 3000rpm and Scott changed the tune to bring the boost in earlier.
I never did a flex fuel sensor or an E tune on my car as there are no E85 stations within a reasonable driving distance of my house, but the power differences are substantial. Just mind the extremely hygroscopic nature of ethanol and don't let the car sit very long with higher ethanol content in the tank or you're asking for corrosion issues.
Rail pressure drop with the stock fuel system in the 3000rpm range is more of an issue for M6 cars as you can stand on it at a low RPM in a higher gear and the transmission won't automatically downshift and the engine has to pull through that lower RPM range where the volume of the stock fuel system is inadequate to support a tune. With an A8 car, the transmission would downshift (unless you're in manual mode) as soon as you put your foot in it and once the RPMs come up and the engine is out of that lower RPM range where the stock fuel system is inadequate.
Running the fuel system on the ragged edge is asking for trouble IMO; personally, I wouldn't do any tune without a fuel cam and LPFP upgrade so there's no risk of running lean anywhere in the RPM range. After I installed a Tapout fuel cam and ZL1 LPFP there were no more rail pressure drops around 3000rpm and Scott changed the tune to bring the boost in earlier.
I never did a flex fuel sensor or an E tune on my car as there are no E85 stations within a reasonable driving distance of my house, but the power differences are substantial. Just mind the extremely hygroscopic nature of ethanol and don't let the car sit very long with higher ethanol content in the tank or you're asking for corrosion issues.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Another Question along this journey.
I have the Stage 2 LPFP from Scott at Tapout.
For the HP Fuel, it looks like the ZZP cam is 40% more stroke at the cam lobe, the Tapout is about 20% but makes up for the volume with the HPFP internal kit. Is one better or worse than the other. My car is basically a DD and gets ~7K miles a year
I have the Stage 2 LPFP from Scott at Tapout.
For the HP Fuel, it looks like the ZZP cam is 40% more stroke at the cam lobe, the Tapout is about 20% but makes up for the volume with the HPFP internal kit. Is one better or worse than the other. My car is basically a DD and gets ~7K miles a year
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A 20-21% fuel cam with upgraded HPFP and upgraded LPFP can basically run full pump E.
A ZZP fuel cam isn't compatable with an upgraded HPFP due to its spec fuel lift - it'll ultimately destroy the HPFP - and tops out around E65 with an upgraded LPFP.
My car is a semi-daily driver and I do HPDE (not drag racing) with it, so I elected to go with a ZZP fuel cam and run E48 and "only" have 601whp. I've accidentally run a 30 minute session around E56 with 'just' a fuel cam due to a fuel mixing screwup on my part...VCM Scanner showed strong fuel pressures at WOT down a 2200' straight but I wouldn't do that on a regular basis.
I think for MAX horsepower on a dyno or drag strip, Tapout or XDI fuel cam, upgraded HPFP, and upgraded LPFP is the ticket.
A ZZP fuel cam isn't compatable with an upgraded HPFP due to its spec fuel lift - it'll ultimately destroy the HPFP - and tops out around E65 with an upgraded LPFP.
My car is a semi-daily driver and I do HPDE (not drag racing) with it, so I elected to go with a ZZP fuel cam and run E48 and "only" have 601whp. I've accidentally run a 30 minute session around E56 with 'just' a fuel cam due to a fuel mixing screwup on my part...VCM Scanner showed strong fuel pressures at WOT down a 2200' straight but I wouldn't do that on a regular basis.
I think for MAX horsepower on a dyno or drag strip, Tapout or XDI fuel cam, upgraded HPFP, and upgraded LPFP is the ticket.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Thanks for the info. That was the route I was heading (Tapout cam and HPFP upgrade) but saw the ZZP cam when I was looking at the cam sprocket tool.
Thanks!
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Is there an easy way to test water content in E85 fuel? I have some sealed containers that have been sitting for a while and want to make sure all is good before using in the car.
Thanks...
Thanks...
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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I agree. I probably will not need the full capability, but I would enjoy knowing I have extra overhead in case.
And you are correct. Probably be running around E30 - E40 but might like to play at higher levels from time to time
. From discussions maybe up to E70 is possible.
And you are correct. Probably be running around E30 - E40 but might like to play at higher levels from time to time
. From discussions maybe up to E70 is possible.
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I have all Tapout stuff: Stage 1 LPFP, HPFP internals and the cams. I asked Scott for the widest E range possible while still being safe and he got me to E75. I don’t make anymore power above E60 but I wanted the extra margin in case I mix wrong or the ethanol has an unusually highly content that throws my calculations off. Just remember the more E in the tank the harder the fuel system works. There’s no reason to tax the system more than you have to and I try to keep my max mix at E63-65.I agree. I probably will not need the full capability, but I would enjoy knowing I have extra overhead in case.
And you are correct. Probably be running around E30 - E40 but might like to play at higher levels from time to time
Honestly if you go all out on the fuel mods…Once you put that kill tune in that’s what you’re gonna want to run majority of the time. It’s way faster than the flex tune you can get and it can be addicting. If you’re thinking you’re going to spend all this money and not use the car to it’s potential you’re probably mistaken.
Here’s my experience and advice, specifically if you’ll be dyno tuning: I have the kill tune and the flex tune only. I only use the flex tune when I want to run 93/switching between kill tune and 93. If I knew what I know now I would have gotten a tune specific for 93 when I had the work done. My point is if you’re going to run E and you have a fully upgraded fuel system, you’re gonna put E60+ in it, I promise you. As far as running ethanol (at least for me) the flex tune is necessary to allow the fuel to mix while driving after filling up, or going on a road trip, but that’s about it. I don’t ever find myself thinking I just want 75% performance this week so I’m stopping at E40. I’m either putting 93 in or I’m taking advantage of the capabilities I paid for with the E60+ tune.
The flex tune is great and necessary but if you intend on using specific various fuel levels like E30 or 93 then get tunes specifically for that as well so you can optimize the vehicle for that fuel. The flex tune is versatile and makes great power but you’ll give up performance at any specific fuel level for the versatility. For instance my flex tune makes between 464 at E0 and 570 at E75 to the tires. A 93 specific tune for my setup should make around 525. An E30 tune would probably be around 550. You can see how much power I’m leaving on the table with the flex tune at any E% vs a specific tune. I’m probably giving up 40whp with 93 octane and an E30 tune is encroaching on the max my flex tune does with E75. The flex tune is necessary and I’m glad I have it but if you’re going to run a couple specific fuel blends get tunes for those in addition to the flex tune. Use the flex tune for road-trips or when switching fuel concentrations, otherwise pick the fuel you want and run a tune for it. Do it all at once while you’re on the dyno and then enjoy the car.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Great advice! Thanks. I will likely get a few specific tunes based on your experience.
Back to testing for water, is there an easy way to test some X85 fuel for water content. The barrels have been around for a while but never opened.
Back to testing for water, is there an easy way to test some X85 fuel for water content. The barrels have been around for a while but never opened.
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Water is more dense than fuel and will settle to the bottom of the barrels. You could transfer some fuel to a clear container, like a large beaker, and see what if anything settles out.
Similar to a general aviation "fuel sump" test, but if you've got a barrel of fuel you can't exactly sump water out the bottom.
Similar to a general aviation "fuel sump" test, but if you've got a barrel of fuel you can't exactly sump water out the bottom.
I have heard there's some ATS-V's that are experiencing smoke during WOT. One theory was that all of V's were running high % of E and causing the turbo seal accelerated wear. Not sure if that's the cause, but I can imagine the possibility of this happening. I tend to run 93 more than E30-E50, and factor in traction limitation if I'm not on a sticky tire.
P.S. I was never told what high % of ethanol equaled.
P.S. I was never told what high % of ethanol equaled.
Bunch of resullts here: test for water in e85 fuel - Google Search
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I’m not a scientist by any means but if you purchase an ethanol tester kit you might be able to get a good idea if your fuel is good still. The kits work by adding a little water with your fuel into the kit/container. You shake the container and the fuel will separate from the water. Where the separation occurs in the container will correlate with what your ethanol % is. If you’re ordering E85 by the barrel it should be exactly E85 or whatever it is that you ordered. If you use your test kit and you’re getting a result lower than what you purchased then that should tell you water is getting absorbed into the fuel. Or you got a bad barrel I guess. Assuming quality control isn’t the problem a reasonable explanation your fuel reads a lower E% is it’s not as pure as it should = water is being absorbed = less fuel and more water into your test kit = test kit shows a lower E% than what you ordered. Maybe that isn’t 100% scientific but it should give you an idea. I recommend reaching out to the manufacture describing your situation (how old the fuel is, sealed/never been open, where it’s been stored, temperature and humidity of where it’s stored, etc) and see what their opinion is. If you used a reliable company they should stand by their product and tell you the truth one way or the other. They want happy customers using their fuel and they don’t want pissed off customers who blew their car up with fouled fuel.
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