FI, meth, and tuning question...
10-19-2008, 01:36 PM
#1
FI, meth, and tuning question... When my car was tuned last with the meth injection, it was tuned on the safe side of things. I have a Snow Performance meth injection kit and was using a 50/50 water meth mix. The meth was setup to start spraying at 4#'s of boost and at 10#'s of boost was to achieve max spray. Now, with my wideband 02's at WOT it would usually sit about 11.5 until the meth came on, then it would dip down into the 10.6-10.8 range. Now I believe Bryan Herter to be one of the best tuners available. Especially considering that I am running my setup all on the stock 95 PCM, however it seems a little rich IMO to be running at mid to high 10's in the AFR. Ideally, I would think I would want 11.5.
Yesterday my car went on the dyno, and while on the dyno the guy shut it down a few times as he noticed my AFR was bouncing between 11.5 and 12. I assessed things and noticed that my methanal injection was not coming on. We did a few more pulls that remained in the 11.5-11.8 range AFR wise, but still no meth.
I'll be checking the meth injection setup later this week when I have more time, but my question is; wouldn't ideally the car make most safe power at 11.5 AFR? I am guessing that potential power is lost when the meth is coming on and its at 10.6 (sometimes as rich as 10.4). Now, I also know that the meth has cooling cababilities as well, so without the meth I am sure my IAT's are hotter, and am closer to detonation.
Ultimatly I am asking, should I be seeking a true 11.5 AFR with the meth spraying? Or am I better off just getting the meth working again, and running with AFR's of 10.6-10.8 at WOT?
Yesterday my car went on the dyno, and while on the dyno the guy shut it down a few times as he noticed my AFR was bouncing between 11.5 and 12. I assessed things and noticed that my methanal injection was not coming on. We did a few more pulls that remained in the 11.5-11.8 range AFR wise, but still no meth.
I'll be checking the meth injection setup later this week when I have more time, but my question is; wouldn't ideally the car make most safe power at 11.5 AFR? I am guessing that potential power is lost when the meth is coming on and its at 10.6 (sometimes as rich as 10.4). Now, I also know that the meth has cooling cababilities as well, so without the meth I am sure my IAT's are hotter, and am closer to detonation.
Ultimatly I am asking, should I be seeking a true 11.5 AFR with the meth spraying? Or am I better off just getting the meth working again, and running with AFR's of 10.6-10.8 at WOT?
10-22-2008, 02:43 PM
#2
One thing to keep in mind with meth. injection, is the stoich point of methanol,
depending on the size of your nozzle, you can be injecting a whole lot of methanol into your motor under boost, which means in order to achieve an "actual" safe A/F, you need to take into account the methanol content of your fuel...
depending on the size of your nozzle, you can be injecting a whole lot of methanol into your motor under boost, which means in order to achieve an "actual" safe A/F, you need to take into account the methanol content of your fuel...
10-23-2008, 11:30 AM
#5
No, the stoich point of methanol is 6.4 : 1, gasoline is 14.7 :1.
Therefore, for optimum combustion you want 14.7 parts air to every 1 part gasoline, or 6.4 parts air to every 1 part methanol.
since the meth is going to give you a margin of safety ( due to high cooling effect and octane) you don't need to be spot on, you should however try to figure out about how much meth is being injected in proportion to fuel.
say you have 60 lb/hr injectors. and 1 meth nozzle flowing 625ml/min (assuming you have the snow kits biggest nozzle, which you should).
at this point your probably only seeing 60% - 75% duty cycles (all a guesstimate, but work with me here...)
so, theoretically, your flowing anywhere from 3000 - 3700 cc/min of fuel under boost, and 300 or so ml of meth (remember, 50/50 mix).
that being said, meth is really only about 10%, if less, of your total fuel.
i don't really know where to go from here to tell you what your ideal a/f should be under those conditions, but your tuner should. Ask him.
hope this helps a little.
Therefore, for optimum combustion you want 14.7 parts air to every 1 part gasoline, or 6.4 parts air to every 1 part methanol.
since the meth is going to give you a margin of safety ( due to high cooling effect and octane) you don't need to be spot on, you should however try to figure out about how much meth is being injected in proportion to fuel.
say you have 60 lb/hr injectors. and 1 meth nozzle flowing 625ml/min (assuming you have the snow kits biggest nozzle, which you should).
at this point your probably only seeing 60% - 75% duty cycles (all a guesstimate, but work with me here...)
so, theoretically, your flowing anywhere from 3000 - 3700 cc/min of fuel under boost, and 300 or so ml of meth (remember, 50/50 mix).
that being said, meth is really only about 10%, if less, of your total fuel.
i don't really know where to go from here to tell you what your ideal a/f should be under those conditions, but your tuner should. Ask him.
hope this helps a little.
10-23-2008, 11:33 AM
#6
Sorry, I kinda got lost in all that.
Basically what im trying to say, is that because meth has a substantially higher (or lower, however you look at it) stoich. point, you need MORE of it than you would gasoline for a given horsepower, nearly double in fact ( maybe more even).
So, under boost, with meth on, you want a richer A/F than without meth.
How much richer, I can't really help you with, I don't know, thats why i dont tune cars. but like i said, ask your tuner.
Basically what im trying to say, is that because meth has a substantially higher (or lower, however you look at it) stoich. point, you need MORE of it than you would gasoline for a given horsepower, nearly double in fact ( maybe more even).
So, under boost, with meth on, you want a richer A/F than without meth.
How much richer, I can't really help you with, I don't know, thats why i dont tune cars. but like i said, ask your tuner.
10-23-2008, 12:09 PM
#7
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What happens if you are under boost and the meth injection stops working? That would put you a point higher. All things equal I like a bit rich, but that is me. Detonation does not take long to eat pistons.
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10-23-2008, 03:52 PM
#9
Personally I have a bright green light that turns on whenever the meth is on. I know when I am just starting to get into boost that if the light doesn't come on, I just get out of the throttle.
Or you can do the less efficient way of just having it tuned extra rich that if it doesn't come on, you still will be okay, but IMO that is just wasted power as when everything is working as it should, you don't need to be that rich.
Back to the original question, Julio from Alky-Control stated that with my particular setup (single nozzle, 50/50 water/meth mix) that I should be aiming for around 11.0 AFR. So "yes" it should be more rich than that of 11.5 which is what ideally you would want on a FI car running just gas.
10-24-2008, 03:30 PM
#10
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Making this short on blackberry now
What im trying to say when spraying meth into the intake. Your not shooting for the normal a/f. And your need to figure out how much meth you are adding.
I am running a 15gph and a 10 gph nozzle at 100 psi. Which adds up to 25 gph total. Right ?
Wrong my pump maxes at 150psi. at max boost im flowing close to 32 gph of meth into the engine. with that much meth at a 10.1 a/f . The Spark plugs look a little lean but still good. I run the track than i shut the engine down and pull the spark plugs to check.
stock ls2 with 14.5 psi of boost pushing a 4000lb car. yes i know the engine about to blow but holding so far. and im running almost 60/40 91 octane gas / alky
Try running 100 meth mixing water in is not the best way of doing it. You get more cooling/higher octane added/ less water/meth acid affect. Check it out Get two glass jars put alum and brass metals in both one 50/50 one pure meth. the one with water will start to rust/oxidizes what in the 50/50 jar
What im trying to say when spraying meth into the intake. Your not shooting for the normal a/f. And your need to figure out how much meth you are adding.
I am running a 15gph and a 10 gph nozzle at 100 psi. Which adds up to 25 gph total. Right ?
Wrong my pump maxes at 150psi. at max boost im flowing close to 32 gph of meth into the engine. with that much meth at a 10.1 a/f . The Spark plugs look a little lean but still good. I run the track than i shut the engine down and pull the spark plugs to check.
stock ls2 with 14.5 psi of boost pushing a 4000lb car. yes i know the engine about to blow but holding so far. and im running almost 60/40 91 octane gas / alky
Try running 100 meth mixing water in is not the best way of doing it. You get more cooling/higher octane added/ less water/meth acid affect. Check it out Get two glass jars put alum and brass metals in both one 50/50 one pure meth. the one with water will start to rust/oxidizes what in the 50/50 jar
Last edited by BigRich954RR; 10-24-2008 at 06:00 PM.
10-24-2008, 04:48 PM
#11
Making this short on blackberry now
I am running a 15gph and a 10 gph at 100 psi. Flowing a lot of meth at 10.1 a/f. Spark plugs look a little lean to good on a run than shut down check. But remember if your pump goes passed a 100psi u are flowing more then rated nozzles. are showing
Try running 100 meth mixing is not the best way of doing it. You get more cooling/higher octane added/ less water/meth acid affect. Check Get two glass jars put alum and brass metals in both one 50/50 one pure meth.
I am running a 15gph and a 10 gph at 100 psi. Flowing a lot of meth at 10.1 a/f. Spark plugs look a little lean to good on a run than shut down check. But remember if your pump goes passed a 100psi u are flowing more then rated nozzles. are showing
Try running 100 meth mixing is not the best way of doing it. You get more cooling/higher octane added/ less water/meth acid affect. Check Get two glass jars put alum and brass metals in both one 50/50 one pure meth.
