For those running meth...
03-10-2011, 07:30 AM
#1
For those running meth...
What AFR are you commanding in boost, and at what timing? I've been slowly and carefully bumping timing up, up to 16° now with no KR. Want to bring it up to 18. Commanded AFR has been at 12:1, and it still dips into the high 9s at full boost cause of the huge meth nozzle. Also looking to lean it out by a 1/4 point.
03-10-2011, 07:55 AM
#3
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Every tuner does it different, but if it were my truck I would get it dead on first then use the meth as a octane/cooler and not rely on it to make the truck richer. Anything like a failed pump or run out of meth and things go bad quickly.
My tuner told me when i added meth he would tune the truck a little harder and use it as a back up safety, rather than rely on the system to use the boost and timing. Hope this helps and gives ya a little info. Its all a personal preference on how hard you want to push your truck!
My tuner told me when i added meth he would tune the truck a little harder and use it as a back up safety, rather than rely on the system to use the boost and timing. Hope this helps and gives ya a little info. Its all a personal preference on how hard you want to push your truck!
03-10-2011, 08:32 AM
#4
Every tuner does it different, but if it were my truck I would get it dead on first then use the meth as a octane/cooler and not rely on it to make the truck richer. Anything like a failed pump or run out of meth and things go bad quickly.
My tuner told me when i added meth he would tune the truck a little harder and use it as a back up safety, rather than rely on the system to use the boost and timing. Hope this helps and gives ya a little info. Its all a personal preference on how hard you want to push your truck!
My tuner told me when i added meth he would tune the truck a little harder and use it as a back up safety, rather than rely on the system to use the boost and timing. Hope this helps and gives ya a little info. Its all a personal preference on how hard you want to push your truck!
True true true statement. A failed pump or no meth on a system that relies on it will be certain destruction if not at least lay the grounds for a future failure.
However, to really get the BIG benefits of it, my opinion is you need to push into that danger zone. That can be done with safety measures. I use meth only when I run nitrous and thus have my wideband setup to turn nitrous off if the AFR gets over a certain point. A tad different than what you are doing, but you can still use the same philosophy. Just set it up with a timing box or something so the circuit adds a certain amount of timing if it goes over the afr target. Don't have a wideband? Get one. A freaking must if you are looking to go betond the norm in modifying your truck IMHO. There are ways to accomplish this if you have tuning software or want to buy the needed items for this. Otherwise, you must accept you are in dangerous territory when tuning for meth on the street. But alas, wouldn't be fun if ya didn't.
That moves me onto the actual question. People's answer on this afr target is loaded. That target depends on the ratio of gas to meth you are using and at what boost (if any) on what compression. Sure, we can all answer generalities to get you a number, but each system and how much meth they use is different. With a 75shot of nitrous I use "butt loads" (actual scientific measurement) of meth WITH 110 octane and 90 octane and will not accept anything higher than 11.4-11.5. Otherwise I shut the nitrous off (through the afr cutout feature on my wideband setup). This HAS contributed to my engine still being alive today. That's my accepted limit, my run is usually 11.0:1. Which is all BS because meth has a different stoich anyway.
03-10-2011, 09:15 AM
#5
I'd love to use the meth as an octane/cooler and not rely on it to make it richer, because that would be like having the benefits of a meth injection system without the over-rich disadvantage it also presents. I am trying to alleviate this over-rich disadvantage by leaning out the actual AFR, not the one I am commanding. However to do that, I would need to lean out the commanded AFR.
I understand that there is the risk of damaging the engine if the meth system ever quits, but I didn't buy the best meth kit on the market for nothing. I have faith in Julio's kit, as it's a quality system.
I'm not looking for a perfect mixture, and am willing to stay richer than optimal to prevent engine damage. I am using a 15gph meth nozzle at 10psi with 9.5:1 CR. Dewey, I assume that by "shooting for" an 11:1 ratio, that is the ratio you look for on the WB? I am also looking for a number like this to shoot for. Granted I am no chemistry major which is why I am ok with staying on the safe/rich side at the expense of a few horsepower. I know alcohol fuels like to run richer...just looking for some wise words on the matter
03-10-2011, 09:37 AM
#7
like Dewmanshu said, it's going to be different for each user, type of compressor etc. My engine LOVES higher AFR, I try to keep it ~11.7 under full boost (~12psi) Lower it dogs. As far as timing, same situation, I don't think Turbos love timing as much as a modified roots.
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03-10-2011, 09:48 AM
#8
I've noticed that, guys with roots blowers always run way more timing than other types of FI. Never really figured it out though... Bottom line, I'd like to at least get it consistently out of the 9s. Mid 10s, even still being slightly rich (safe), and I'd be happy. There's certainly some cylinder washing in effect in the 9s, but to bring it out into the 10s at full boost I may need to command up near 12.5:1.
03-10-2011, 09:59 AM
#9
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you need a controller for the meth. Several companies sell them aem, devils own, snow and many others. It will allow you to control the amount of meth and how fast it comes on to help with tip in kr and wot being too rich! You set up your tune and then add the meth as needed by turning a dial!
