Meth before or after the sensor. This mostly depends on whether your meth setup has a safety switch (window switch). If it does, and meth activation is being read and taken into account, the the sensor will should (with few exceptions) be place BEFORE the meth nozzle. This is where the reading will be most accurate and slop for improper atomization for the water/meth doesn't have to be accounted for. Meth activated = More timing and leaner fuel curve. Meth not activated mean less timing and richer fuel curve. Regardless... if your tuner is worth his sand, he has a method for tuning and specific reason for doing it that way. You need to ask question of him and have him explain why he does it the way that he does.
The ideology there is correct, but it's not feasible. You have one problem (and it's a BIG one). How does a stock ECM know if the meth is spraying or not? I know if you're using one of those flow meters, it can set off bells or whistles or lights or whatever, but it still doesn't tell a stock ECM to adjust the timing or fuel. If you add timing and remove fuel for the methanol in the tune, and then, for whatever reason, the methanol doesn't spray, YOU ARE SCREWED. In my case, the check valve stuck closed, and this was the result:
On a stock computer that doesn't accept external inputs (i.e. flow meters, etc.), there is only one way to properly tune methanol (and the IAT sensor HAS to accurately read the actual temps coming into the motor):
1. Turn the meth off for the tune.
2. Tune the car. Set the AFR at a safe level (12.0ish). Set the timing at a safe level as well (13ish is typical for a non-intercooled 8-9 pounds).
3. Now turn the meth back on.
4. Go back into the tune and add timing based on the cooler IATs. Exactly how to do this depends on the setup and how much the IATs vary. On my setup, the meth easily brings the temps to less than 120, while the temps are well north of 200 without. So if the IATs are less than 140ish, then we KNOW that the methanol is spraying, and it throws the timing to it (from 13 degrees max up to 24 degrees max). If the temps are over 140, then we know that the meth isn't spraying, and the computer simply sticks to the original tune.
5. Finally, and this is CRUCIAL. DO. NOT. ADJUST. THE. AIR/FUEL RATIO. The wideband is going to read that it is richer with the methanol, but because the computer doesn't have a way to adjust the fuel to account for the meth, leaning it out can/will cause the motor to go dangerously lean if the methanol doesn't spray.
And while we're talking about AFR, it needs to be made clear that methanol doesn't richen up the mixture as much as the wideband indicates. A wideband doesn't measure the AFR, it measures lamda and then calculates the AFR based on the stoichemetric ratio we have it programmed for (14.7 is most cases). Because methanol's stoichemetric ratio is much less than gasoline's (6.5 vs. 14.7), the lamda value read by the wideband is going to be lower, as is the actual stoichemetric ratio. However, since we aren't reprogramming the wideband for this lesser stoichemetric ratio, it is going to read richer than it actually is.
I haven't done the calculations myself (yet), I've been told by some folks that know that my setup is only enriching up about .3-.4 point, even though the wideband indicates that it's over a point richer. And I am spraying a LOT of water/meth (14 GPH of 70/30 water/meth).
Water/Meth doesn't show on a dyno. It most certainly DOES show on a dyno but as suggested by someone else in this thread, before and after would be relative to the baseline of that SAME dyno and should not be compared to a similar combination belonging to mother's cousin's Aunt's next door neighbor's car who lives 1200 miles away and that their dyno done at Bob's garage on a 30* day with zero humidity. Water/meth effectively decreases ambient air (in this case blower discharge air) temps and increases fuel octane. It's worth quite a bit in terms of timing and Air Fuel Ratio. On my setup, I saw an 80 HP difference and even more torque and this was through much of the power band.
My suggestion would be (since you're running meth) is to run more boost. I wouldn't expect that meth on a vortech making only 8 lbs of boost would be a HUGE difference but meth injection become more and more efficient as the air that it's trying to cool becomes hotter. Add a couple more lbs of boost and you will notice that the water/meth cooled air is not significantly higher than what it is right now with only 8 lbs of boost.
Hope that helps.
It shows on
some setups. You gained 80 rwhp; Winters has showed nice gains on his Vette; I know others that have as well. But it simply does not show on some setups. I just went and looked at my dyno graph from when it was tuned; I gained 13 rwhp and 0 rwtq on the methanol. However, on the same tune, same car, same weight, same track, same time, same EVERYTHING except the flip of a switch, here is what my car did:
No methanol:
With methanol:
Yes, that's a full 7 mph and .4 second difference. 13 rwhp my ass.
We did some tweaking on the tune (added timing in down low) to get it to come out of the hole stronger, and picked up another .15 seconds and 1 mph a week later.
Couldn't agree more on comparing different cars on different dynos. Apples to oranges.
Also agree on running more boost, but only if he
actually is cooling the temps down. I'm spraying 14 GPH methanol on 8 pounds of boost, which cools it down perfectly, but most people don't/won't spray that much (for whatever reasoning).
Not trying to bash anyone here, just trying to make it understood that dyno numbers aren't everything.
