05-06-2010, 09:25 AM | #61 |
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I did
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05-06-2010, 10:18 AM | #62 |
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Got it... nice....
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05-06-2010, 10:20 AM | #63 | |
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I think the idea of a dual mapped system does not make much sense in the real world. If you are running a ‘typical’ turbo engine with a single injector per cylinder set up you cannot optimize the system to run both fuels. If you run boost up to 20psi you will need the full range of duty cycle available from the injector (minimum turn on time to 100% duty cycle). If you calibrate your system (injector size and fuel pressure) for gas it won’t be able to deliver enough E85 to achieve the same power (boost) level – in fact you will have to limit your boost to quite a bit lower or turn your fuel pressure way up to run the same max boost. (14.7 vs 9.76 stoich mixture) . So the thought of having two maps and being able to switch back and forth does not really work well in the real world. You either have to swap injectors or make a significant change in fuel pressure to swap between the fuels. If you add secondary injectors you can do it…. And yes to your original question - that advantage is that you can run more timing without fear of detonation. This is mostly due to the significant amount of charge cooling available from the E85. (interesting fact – top fuel dragsters are cooled by the fuel – not by coolant). You can add more timing but you will run out of injector duty cycle before you can make more power than a well tuned gas system running the same injectors / fuel pressure. Sorry, no cake and eat it too deal here…
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05-06-2010, 01:14 PM | #64 | |
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So, have a piece of cake and take a big bite!
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05-06-2010, 01:38 PM | #65 | |
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When you get to / above 400rwhp the 72lb injectors (regardless of displacement) get maxed out before 20 psi on gas – so the E85 boost would be a bunch lower. I haven’t sat down and done the calculations but I would guess that for the same volume of fuel gasoline has a much higher power output. So I guess you can have your cake and eat it too as long as it’s a small piece than you had before! The other ’functional’ problem is having straight gas or E85, if you start mixing the two you now need a ‘blended’ map. Its not exactly proportional (ie – if you run a E85 – gas mix at 50/50 you can’t depend on ‘splitting the difference’ between the two timing curves). Yeah, it will work but there are some compromises that make it less than optimal. As I have mentioned before – if E85 was available around here I would build a motor just for it(much higher compression) – and a tune specifically for E85 as well. I do like the EV14 1000cc injectors….!
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05-06-2010, 03:26 PM | #66 | |
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I ran strictly E85 for quite some time until I got tired of making very frequent trips to the pump. The additional fuel required with E85 becomes very apparent if you have a heavy right foot! For daily driving, running less boost and getting a bit better mileage turned out to be the "smarter" option. I pitched the arguement to the refinery selling the E85 that it takes 30% more fuel to run this stuff, so why isn't it 30% cheaper than standard pump gas?!? I never had the chance to maximize the full potential of E85 on my 2.5L cause I ran out of injector with the 72lb'ers. But, the real world benefit I saw in using this fuel was the fact that in the blistering heat of the AZ summer (105-110F), I was only able to run 15 psi with 91 pump before detecting knock and with E85 I could run 19 psi and more timing advance without any problems! Within the Vi-PEC there is an option now available for supporting a GM E85 fuel sensor so mixing fuels becomes less of an issue. For the trouble it would take to install this sensor, I'd prefer taking the approach of using either all pump or all E85. I'm looking forward to trying E85 again with the EV14 1000cc injectors. I am so happy with how these injectors are performing - definitely a step in the right direction for injector options.
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05-06-2010, 05:03 PM | #67 |
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You can have your cake and eat it, no matter the size of the motor. There are 2000cc injectors available that work great. The Subi/JDM crowd has been doing it for a year now. You just need to branch out of the 944 world.
Yes, the LinK has the E85 input too. Brian(the edge) is trying it out on his Extreme. |
05-06-2010, 05:52 PM | #68 | |
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Sorry....... |
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05-06-2010, 06:32 PM | #69 | |
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I have a hard time believing you ran 20 psi on E85 with 72lbs injectors. I haven't done it before, so I could very much be wrong, but that's a smallllll injector for 20 psi. My calculations beg for a much larger injector. |
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05-06-2010, 09:11 PM | #70 |
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Hi DDP,
just for comparison, we run 1.5bar(21psi) on patricks engine with E85, 3 bar FPR, on i think 80lbs injectors. we were using a 928HV fuel pump but couldnt get any more fuel in past 3000rpm or thereabouts. we then upgraded to the 044 pump and that allowed us to run the fuel we needed.
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05-06-2010, 09:19 PM | #71 | |
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Tricky,,,,very tricky. You almost had me for a minute
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05-07-2010, 12:29 AM | #72 | |
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Well, all I can tell you is that I lived it man - 20 psi with 72lb's on E85. On the dyno, the AFR was still showing a "safe" number but any more boost and I was starting to lean out no matter the fuel settings.
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05-07-2010, 12:33 AM | #73 |
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No wonder I'm going thru so many clutches! Nice catch.
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05-07-2010, 01:05 AM | #74 | |
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For us, race fuel is $4-$5 per litre which is about $15+ per gallon! E85 costs .99c per litre at this pump so it's a no brainer. When we used it at the track though you can go through a tank in approx 1 hour so you have to take plenty of Jerry cans. |
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05-07-2010, 03:24 AM | #75 |
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Isn't it amazing at how clean the stuff burns?!? Every time I'd pull my plugs I was just stunned at how clean they were. Pulled my intake a couple of times and the intake valves were as clean as when I had the head rebuilt. I didn't have any soot in the tailpipe or residue on the bumper either - the stuff works good.
.99c / litre is a bargain for the performance you get out of it. Too bad it's not daily driver friendly. I just couldn't keep my foot out of it when I was running that fuel. I regularly averaged around 8-10 miles per gallon from a full tank of gas. Wayyy to much fun to maintain (or even attempt) any sort of restraint!
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