True, my last post was stabbing towards the "reality factor" not the "how much am I giving up factor".
Yes, E85 isn't listed, and not ALL fields can be calculated by mixing numbers, as many things have dynamic effects on the fuels. But some things like the latent heat of vaporization scale very linear in the blend. The evidence of this can be seen in how well certain aspects of flex-fuel tuning work all the way from E10 to E85 and anywhere in between with simple table extrapolation. While we can get stuck in the details of science, real-world tuning application says that most things blend linearly just fine.
Well, as discussion basic bowl cleanup, mild unshrouding, and intake port centerline lifting will all be done. I'd be surprised if I'm not flowing over 190cfm on the intake side. But speaking of just dividing numbers, you also didn't note the difference between the number of intake runners when comparing here. But anyway, the main compounder of heat in force induction is PSI, and the restriction of the air pump is directly related. I think we've both proven we understand that 100psi of boost might make 100 hp on some motors, and other motors might make 1,000hp with just 10psi. It's all about flow. That said, The G25 turbos should match stock-to-hot street L28 builds nicely, though I think it's a bit low on flow potential on the turbine side for a real hot L28 trying to chase world records. The compressor on the G25 I think is slightly biased towards higher PSI than I think most would really want to run on a L28 unless you're going to run low compression. This is also evident in the recommended displacement range Garrett advertises of 1.4-3.0 litres. An L28 is knocking on the door of that, but would likely be just fine as it's a mild flowing head. This is a turbo that WANTS to live around 2.5 pressure ratio and will work up to 3.5 in extreme cases. In my use case I'd be living between 2 and 2.5 pressure ratio, and where I land on the efficiency would depend on how well the head is flowing, which would also determine achieved power.
Good point, though they're dynoing over 2khp now , so there is that.
All true, and I agree and knew all this ahead of time. My point of including it in the discussion from the get-go is that they weren't running an intercooler, and were still running sub 7 second 1/4 miles and added an intercooler NOT because of heat management issues, but heat CONSISTENCY issues" Their goal with the new build was all about keeping times consistent.
Carburettors suffer from icing for a few reasons or might be more accurate to say that they have a few things working against them that leads to icing. And it should be noted that icing is an issue in LOW power setups, not just HIGH-performance application. First off, is that in order for carburettors to work properly they need a venturi, and the associated pressure drop from the venturi effect is actually the most fact proven reason for carb icing, and why low latent heat of vaporization gasoline can still have carb icing in 100 degree weather. Now, when you combine the venturi effect with poor atomization you end up with a very localized heat transfer as the fuel makes it's lazy path to vapor.
Likely a fair statement. Though most of the guys I've seen running without an intercooler with E85 and with fuel injection are still the V8 crowd. I think this is likely the fact that they run WIDE on compressor maps, with high flow and low-pressure ratio. These guys are making peak power around 6,000 in many cases, and have no issue spooling a large turbo by 2k rpm and don't mind turbo lag because of the off boost power available. There's no reason they couldn't run a setup with a higher pressure ratio, but the that starts to be a pretty serious street engine that few actually shoot for or attain. Also, a lot of the real world examples I've talked to of guys making 1,000+hp on methanol with blown small blocks and 12:1 compression aren't drag motors, they're in BOATS. And not drag boats. These are engines built to happily run cracked open producing 75% of its available power for an hour or more. I've never bothered to ask them how much they spend on fuel... But my point is that the engine builders in this market segment do this regularly and it's no big deal. They're running high compression, and no intercooler. And it's fine because of the relatively low pressure ratio. The fact they're running a carburetor should only be hurting them, as evidence that nearly all carb to efi conversions allow for more aggressive timing, which can only be attributed to fuel distribution being more even, along with in chamber charge temps being lower.
Yeah, I was looking at the HX35... back when I started this thread. How many years ago was that? I was also thinking I'd be doing all this on the cheap. Last year I spend 2k on an OEM Subaru turbo for my outback. The idea of spending that kind of money on a fancy aftermarket turbo isn't a huge deal in my mind anymore. I'm also aware that I'm going to be in a fairly small group in the Z community running a setup like this.
IMO, that guys issues were likely 100% tune related. Guy even says he suspects his head gasket blew from timing. I think a better example is Perrin's article on the STI engine:
Personally, think their biggest issue was that they were still running gasoline in the port. It'd have been a different story with E85. I say that because I've seen an STI go from 375whp range and be VERY timing restricted (as in, they go from being down 30hp to knocking within a 1 degree spread) to being 450whp and nearly not caring about timing on E85. Was it intercooled? Yes. Was it low compression? Yes. But the timing map showed that for that power level, that 2.5 liter engine would have done just fine adjusting those variables, as it had timing to spare.
This is something I've considered since I'll be injecting e85 far back near the plenum. A small thermistor style sensor would be pretty easy to poke through a small hole and seal up with minimal flow restriction. Also, knock sensor would be a very crude way to measure this. The real facny way is to install in cylinder pressure sensors, but that's beyond most of our budgets.
Yeah, I'm not sure it really does in the grand scheme of things. If all the fuel vaporizes, it has the same net effect. The struggle is that some engines have a hard time vaporizing all the fuel in certain load/rpm regions with carburettors. Why do you think there's always a mid range torque increase with EFI swaps on V8's? Usually a drop in peak HP is due to airflow restrictions, but that huge mid range change can't all be attributed to flow....
Now, let's look at some other maths since we're interested in known things we can actually look at and consider.
For example, for any given system we can calculate INLET AIR TEMP -> Compressor Efficiency -> PSI -> Outlet Air Temp
100 degree inlet air temp (either higher underhood temp or hot day ram air)
75% compressor efficiency (which I admit is high, but the G25 compressors reach 79 peak...)
targeting 20psi boost
at sea level pressure
Our turbo outlet temps will be a scorching 309 degrees.
Now, an intercooler that's able to achieve a crappy 50% efficiency would drop us all the way down to 203 degrees, which is "managable" and I've seen people tune around IAT temps in that range pretty often.
So the question becomes "how much does E85 drop temps"? This might be hard to answer definitively with data sheets on a paper, but some of these guys seem to have foumulas that match their real world experience:
Specifically post number 11
You can see they're just doing latent heat of vaporization by weigh compared to AFR. Though maybe simple it seems to be pretty effective and doesn't try to get into "real world modifier math modifiers" to compensate for lack of initial math function viability.
Now, the one thing I'd point out, is that using a lambda of 1.25 might be "ball park" for most people, but that's a bit on the lean side of your window to work with. The 1.25 figure is relating to the lambda equivalency ratio that you'd see on a chart like this:
Lean max torque for E85 lands at bout 1.15 while rich max torque lands all the way up at 1.40. That's a BIG range for "max torque" let alone "will burn without issue". I've seen E85 lambda readings down to .55 without ill effect on spark.
If we plug that kind of insane AFR into the calculation:
770/(9.8/1.8) = 141 (Celsius) * 1.8 = 254 (Fahrenheit)
That's 250+ degrees of temp drop capability. Now, some of that will "bleed" into intake and head temp cooling, since we're not using direction injection (would would still have some loss to head temp, but a lot less overall loss since there's no time spent in the intake and no pooling at the valve). All told, that's a massive amount of cooling capacity. But even if we look at this in the more realistic realm of .7 lambda we get this:
770/(9.8/1.4) = 110 (Celsius) * 1.8 = 198 (Fahrenheit)
We're still looking at enough cooling to match a crappy small intercooler, or even best it.
The obvious question though is: "If you're only going to drop the temp AS MUCH AS an intercooler, why do you think you can still run high compression if the net in chamber temp is the same?" Well, the answer to that is more to do with the way E85 burns than it does temperature. In my experience, E85 burns in a much more controlled fashion and much less explosive than gasoline. This allows you to approach minimum required timing and test max available timing for peak power in much safer and controlled way. Now, if you're stupid it'll still blow head gaskets at will since running too much timing for a given condition can still create insane pressure spikes, but if you're running on a steady state dyno doing timing traces you'll see the power drop off with timing in a much broader range before detonation becomes the limiting timing factor.
Overall, I expect to leave power on the table. I don't expect to win any dyno awards here. What I do expect, is to have a very responsive engine that starts up with ease and doesn't eat seals (since it'll run gasoline at start and shut down), while making more than enough power to be traction limited in almost all scenarios (trying to keep with either 225 or 245 max tire).