air fuel ratios and meth
Jan 12, 2008, 06:53 AM
#31
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Ok I'm a little bored lets see what my target stoich will be. Lets go over my fuel setup:
stock injectors
m5/m10 nozzle 100 meth
First we need to know my combine # of cc's for gasoline we are spraying. Here's a little formula to help out.
Stock injectors are 560 cc @ 42lbs, now I'm still on the stock 1:1 regulator/fuel rail. With my fuel gauge I see about 44lbs of static pressure @ idle and 77lbs in fuel boost. My old pressure will be what the injectors are rated @ (42) and the new is when I'm full boost (77). Do the math, I get about 758 cc's of fuel (dont forget to square root it after dividing the pressure). Now due to the fact that you pull fuel out and scale your injectors, we need to know the actual % of fuel spraying. First I need to know find IDC:
IDC = IPW * rpm / 1200 = % (Mine is 78%) by the way still stock fuel pump
Next I need plug in IDC to find the true % of fuel
IDC * (scaling/actual injector size) I got 71%
758cc*4 injectors*71%= 2152.72 (total cc's of gas)
Now moving to meth side of the house.
m5 flows 379cc @ 150psi
m10 flows 771cc @ 150psi
Meth is = 1150.12 cc's
To find the % of meth to gas would be
total meth cc's (1150.12) + total gas cc's (2152.72) = 3097.72
Now 1150.12/3097.72= 37%
So my car is 37 meth/63 gas setup. My new stoich is 13.3
Now 1.0 lambda = 13.3 (my new stoich)
My target afr shold be 11.3-10.64 (.85-.8 Lambda)
Now you see why lambda is important, if you keep it for gasoline (14.7) when mixing different type of fuels it will be offt. example say if you ran a straight methanol car would you tune it for 12's. probably not since stoich for meth is 6.5 and any thing above is lean. Plus it produces it most power @ 4.5. So i think around the 4.3 to 1 sounds good
stock injectors
m5/m10 nozzle 100 meth
First we need to know my combine # of cc's for gasoline we are spraying. Here's a little formula to help out.
Stock injectors are 560 cc @ 42lbs, now I'm still on the stock 1:1 regulator/fuel rail. With my fuel gauge I see about 44lbs of static pressure @ idle and 77lbs in fuel boost. My old pressure will be what the injectors are rated @ (42) and the new is when I'm full boost (77). Do the math, I get about 758 cc's of fuel (dont forget to square root it after dividing the pressure). Now due to the fact that you pull fuel out and scale your injectors, we need to know the actual % of fuel spraying. First I need to know find IDC:
IDC = IPW * rpm / 1200 = % (Mine is 78%) by the way still stock fuel pump
Next I need plug in IDC to find the true % of fuel
IDC * (scaling/actual injector size) I got 71%
758cc*4 injectors*71%= 2152.72 (total cc's of gas)
Now moving to meth side of the house.
m5 flows 379cc @ 150psi
m10 flows 771cc @ 150psi
Meth is = 1150.12 cc's
To find the % of meth to gas would be
total meth cc's (1150.12) + total gas cc's (2152.72) = 3097.72
Now 1150.12/3097.72= 37%
So my car is 37 meth/63 gas setup. My new stoich is 13.3
Now 1.0 lambda = 13.3 (my new stoich)
My target afr shold be 11.3-10.64 (.85-.8 Lambda)
Now you see why lambda is important, if you keep it for gasoline (14.7) when mixing different type of fuels it will be offt. example say if you ran a straight methanol car would you tune it for 12's. probably not since stoich for meth is 6.5 and any thing above is lean. Plus it produces it most power @ 4.5. So i think around the 4.3 to 1 sounds good
your equations have some flaws with them...
first, your fuel pressure does increse in the rail because of the 1:1 FPR. however, the fuel pressure differential (pressure difference across the injector) does not change from the base fuel pressure. for example, 20 psi boost pressure means there is 20psi in the manifold side of the injector, and there is 63psi in the rail. thats a delta of 43 psi still.
next, i'm not sure where you got that equation for scaling/actual injector size. if you have a IDC of 100% with 550cc injectors, thats 550cc/min of fuel. the scaling has no effect on how much fuel is delivered, other then telling the ecu what size injectors are being used. also, the flow rate of the injector is usually determined at a certain pressure level, although i don't know what the stock ones were rated at, i would assume it is something close to 40psi. thus, just use 550cc/min as your pump gas.
next you calculate your stoic ratio with your fuel mixture, but forgot that with a gas calibrated wideband, even if you are running 100% methanol only, if you are running rich (say lambda of .8), it will show up as 14.7*.8 = 11.8 AFR on the wideband. this does not mean you are actually running methanol at 11.8:1 AFR, its just a post process calculation to get a AFR value from lambda. you will still really be running 6.4*.8 = 5.12AFR. does that make sense?
to clarify, if i target 12:1AFR with pump gas and methanol mix, with a gas calibrated wideband, that is a lambda of .82. sense we are running a mix, (we'll use your adjusted stoic ratio of 13.3), in actuality we ARE running a ratio of 13.3*.82 = 10.9 AFR. but sense we leave the wideband calibrated for gasoline, it shows 12:1. i would strongly recommend against recalbrating your wideband for this because at idle and any time your only using gas, it will show a stoic ratio of 13.3 instead of the 14.7 you want., also sense the ratio of meth/gas changes depending on the RPM and boost level your calculated stoic ratio will only be correct in a couple points on your fuel tables.
if you target 10.9 AFR on a gas calibrated wideband with a meth mixture your really in the 9.8:1 AFR if the stoic is 13.3. thats a lambda of .74, which is very rich for any fuel.
last, as for running cars at 10.8:1 afr on a gas calibrated wideband, i have done it a couple times (once not on purpose, it only happened in 6th gear), and the cars buck and misfire like crazy. if you have a gas calibrated wideband, target 12.5-12:1 AFR and see how the car runs (and your gas mileage will go up too). also, we've gone from a very rich mixture to a leaner mixture with slowcars car on the dyno and the power went way up. he can comment on this as he knows what % mixture meth he is running...
Last edited by KevinD; Jan 12, 2008 at 06:57 AM.
Jan 12, 2008, 07:00 AM
#32
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just curious...why dont wideband makers just show lambda because what the wb is actually is a residual oxygen analyzer? afr just does not mmake sense...pounds of air to pounds of fuel...
Last edited by SlowCar; Jan 12, 2008 at 07:08 AM.
Jan 12, 2008, 07:16 AM
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the zeitronix always shows lambda, and you can log with it. i always read AFR though because thats what most people know. its funny trying to tell someone, "DANG, your car is running .74 lambda! we need to fix that..."
Jan 12, 2008, 08:29 AM
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your equations have some flaws with them...
first, your fuel pressure does increse in the rail because of the 1:1 FPR. however, the fuel pressure differential (pressure difference across the injector) does not change from the base fuel pressure. for example, 20 psi boost pressure means there is 20psi in the manifold side of the injector, and there is 63psi in the rail. thats a delta of 43 psi still.
I understand that, but that would mean i would have to do the same thing for meth when it sprays, due to the manifold pressure. So I left it alone
next, i'm not sure where you got that equation for scaling/actual injector size. if you have a IDC of 100% with 550cc injectors, thats 550cc/min of fuel. the scaling has no effect on how much fuel is delivered, other then telling the ecu what size injectors are being used. also, the flow rate of the injector is usually determined at a certain pressure level, although i don't know what the stock ones were rated at, i would assume it is something close to 40psi. thus, just use 550cc/min as your pump gas.
so your saying that scaling has no affect on fuel delivery. Then why does your fuel trims change when you alter your scaling. So after you rescaleyou would have to go back into your WOT fuel map and readjust the fuel points. You take more or less depending how much you increased or decreaed scaling. Ex. like most of the evo9 guys would be stock or close to it they do the math and would get close to 100% of IDC which I highly doubt they like that. But most injectors are rated @ 42psi
next you calculate your stoic ratio with your fuel mixture, but forgot that with a gas calibrated wideband, even if you are running 100% methanol only, if you are running rich (say lambda of .8), it will show up as 14.7*.8 = 11.8 AFR on the wideband. this does not mean you are actually running methanol at 11.8:1 AFR, its just a post process calculation to get a AFR value from lambda. you will still really be running 6.4*.8 = 5.12AFR. does that make sense?
I disagree. O2 sensors arent "calibrated" for any particular fuel. They measure oxygen content. Thats why more advance widebands have the option to change lambda becaue they know people run more than just gas
to clarify, if i target 12:1AFR with pump gas and methanol mix, with a gas calibrated wideband, that is a lambda of .82. sense we are running a mix, (we'll use your adjusted stoic ratio of 13.3), in actuality we ARE running a ratio of 13.3*.82 = 10.9 AFR. but sense we leave the wideband calibrated for gasoline, it shows 12:1. i would strongly recommend against recalbrating your wideband for this because at idle and any time your only using gas, it will show a stoic ratio of 13.3 instead of the 14.7 you want., also sense the ratio of meth/gas changes depending on the RPM and boost level your calculated stoic ratio will only be correct in a couple points on your fuel tables.
your still thinking in gas and not taking in the account for meth. I was more less saying while you were tuning the car when meth spraying you would have a different target lambda. Your not running on meth for cruising or @ idle so why would you leave the stoich value for a mixed gas
if you target 10.9 AFR on a gas calibrated wideband with a meth mixture your really in the 9.8:1 AFR if the stoic is 13.3. thats a lambda of .74, which is very rich for any fuel.
yes thats really rich for gasoline but a car running 100% meth probably wouldnt run and would be consider to be lean because its over its stoic value. But I see what your trying to do with using gas' stoich but when are not running 100% gas its mixed meth/gas. When I said 11.3-10.9 (.85-.8 lambda) it was for wideband set to 13.3 stoich. lambda is nothing more telling you how far you are from stoich or your target stoich if your using a different gas. Thats why you should us lambda, afr values can confuse you. LM-1 is a great wideband to have with tuning meth, I dont know if can change your lambda value.
last, as for running cars at 10.8:1 afr on a gas calibrated wideband, i have done it a couple times (once not on purpose, it only happened in 6th gear), and the cars buck and misfire like crazy. if you have a gas calibrated wideband, target 12.5-12:1 AFR and see how the car runs (and your gas mileage will go up too). also, we've gone from a very rich mixture to a leaner mixture with slowcars car on the dyno and the power went way up. he can comment on this as he knows what % mixture meth he is running...
again you werent running enough timing, or boost. meth takes more energy to burn. step up that cylinder pressure. Like I said it depends on how much meth your spraying. The less meth the more closers you are to gas's stoich. ex lets say person another with stock fuel with same IDC as me injecting 945 cc's of meth. His target stoich is 14.6, very close to gas'. So like you said lean it out to 12 (.82 lambda) would make the most power. But me I'm a meth head and spray quite a bit. LOL
first, your fuel pressure does increse in the rail because of the 1:1 FPR. however, the fuel pressure differential (pressure difference across the injector) does not change from the base fuel pressure. for example, 20 psi boost pressure means there is 20psi in the manifold side of the injector, and there is 63psi in the rail. thats a delta of 43 psi still.
I understand that, but that would mean i would have to do the same thing for meth when it sprays, due to the manifold pressure. So I left it alone
next, i'm not sure where you got that equation for scaling/actual injector size. if you have a IDC of 100% with 550cc injectors, thats 550cc/min of fuel. the scaling has no effect on how much fuel is delivered, other then telling the ecu what size injectors are being used. also, the flow rate of the injector is usually determined at a certain pressure level, although i don't know what the stock ones were rated at, i would assume it is something close to 40psi. thus, just use 550cc/min as your pump gas.
so your saying that scaling has no affect on fuel delivery. Then why does your fuel trims change when you alter your scaling. So after you rescaleyou would have to go back into your WOT fuel map and readjust the fuel points. You take more or less depending how much you increased or decreaed scaling. Ex. like most of the evo9 guys would be stock or close to it they do the math and would get close to 100% of IDC which I highly doubt they like that. But most injectors are rated @ 42psi
next you calculate your stoic ratio with your fuel mixture, but forgot that with a gas calibrated wideband, even if you are running 100% methanol only, if you are running rich (say lambda of .8), it will show up as 14.7*.8 = 11.8 AFR on the wideband. this does not mean you are actually running methanol at 11.8:1 AFR, its just a post process calculation to get a AFR value from lambda. you will still really be running 6.4*.8 = 5.12AFR. does that make sense?
I disagree. O2 sensors arent "calibrated" for any particular fuel. They measure oxygen content. Thats why more advance widebands have the option to change lambda becaue they know people run more than just gas
to clarify, if i target 12:1AFR with pump gas and methanol mix, with a gas calibrated wideband, that is a lambda of .82. sense we are running a mix, (we'll use your adjusted stoic ratio of 13.3), in actuality we ARE running a ratio of 13.3*.82 = 10.9 AFR. but sense we leave the wideband calibrated for gasoline, it shows 12:1. i would strongly recommend against recalbrating your wideband for this because at idle and any time your only using gas, it will show a stoic ratio of 13.3 instead of the 14.7 you want., also sense the ratio of meth/gas changes depending on the RPM and boost level your calculated stoic ratio will only be correct in a couple points on your fuel tables.
your still thinking in gas and not taking in the account for meth. I was more less saying while you were tuning the car when meth spraying you would have a different target lambda. Your not running on meth for cruising or @ idle so why would you leave the stoich value for a mixed gas
if you target 10.9 AFR on a gas calibrated wideband with a meth mixture your really in the 9.8:1 AFR if the stoic is 13.3. thats a lambda of .74, which is very rich for any fuel.
yes thats really rich for gasoline but a car running 100% meth probably wouldnt run and would be consider to be lean because its over its stoic value. But I see what your trying to do with using gas' stoich but when are not running 100% gas its mixed meth/gas. When I said 11.3-10.9 (.85-.8 lambda) it was for wideband set to 13.3 stoich. lambda is nothing more telling you how far you are from stoich or your target stoich if your using a different gas. Thats why you should us lambda, afr values can confuse you. LM-1 is a great wideband to have with tuning meth, I dont know if can change your lambda value.
last, as for running cars at 10.8:1 afr on a gas calibrated wideband, i have done it a couple times (once not on purpose, it only happened in 6th gear), and the cars buck and misfire like crazy. if you have a gas calibrated wideband, target 12.5-12:1 AFR and see how the car runs (and your gas mileage will go up too). also, we've gone from a very rich mixture to a leaner mixture with slowcars car on the dyno and the power went way up. he can comment on this as he knows what % mixture meth he is running...
again you werent running enough timing, or boost. meth takes more energy to burn. step up that cylinder pressure. Like I said it depends on how much meth your spraying. The less meth the more closers you are to gas's stoich. ex lets say person another with stock fuel with same IDC as me injecting 945 cc's of meth. His target stoich is 14.6, very close to gas'. So like you said lean it out to 12 (.82 lambda) would make the most power. But me I'm a meth head and spray quite a bit. LOL
Like I told ya man it doesnt hurt to try it. I was the same way a couple months ago and acutally tried.
also if you do the math and your stoich value is higher than gas's then your not saying in enough meth to affect gas' stoich. since its the majority of the mix. The target afr/lambda will be same as your using it for gas. and use the injection for a cooling factor.
Last edited by bnice01; Jan 12, 2008 at 10:46 AM.
Jan 12, 2008, 08:46 AM
#39
50/50 mix in the right volume will lower A/F 1/2 point. 100% meth will lower a little over 1point. A 50/50 mix is about 113 effective octane when used with a 91 octane base fuel.
With a normal A/F of 11.5, you enable the meth and should see the A/F drop. Now you can do one of the following: remove fueling, add timing or increase boost. Any of the three will then lean out the A/F. A good target A/F with meth on an Evo is 12.2-12.4, if you are running a fail safe like our IFS-10, or other. If you don't have a fail safe, do not lean it out more then 12.0 with 50/50 or 11.5 with 100%.
Best regards,
Dan
With a normal A/F of 11.5, you enable the meth and should see the A/F drop. Now you can do one of the following: remove fueling, add timing or increase boost. Any of the three will then lean out the A/F. A good target A/F with meth on an Evo is 12.2-12.4, if you are running a fail safe like our IFS-10, or other. If you don't have a fail safe, do not lean it out more then 12.0 with 50/50 or 11.5 with 100%.
Best regards,
Dan
Just to be clear on all these comparisons, are all these measurements taken with a wideband calibrated for normal gas - (IE 14.7 to 1)
Keep in mind spraying meth will not only change your AFR but it will actually effect the readings of the Wideband. The lambda will still be accurate but the AFR won't be.
However, as long as everyone is using a wideband calibrated for Meth we are still ok to make comparisons.
Keep in mind spraying meth will not only change your AFR but it will actually effect the readings of the Wideband. The lambda will still be accurate but the AFR won't be.
However, as long as everyone is using a wideband calibrated for Meth we are still ok to make comparisons.
Jan 12, 2008, 01:37 PM
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Yo kevin after lookin @ slowcar's "stats" he is spraying about 945 cc's. So the example I used in my post above would make sense why low 12's worked best for him. maybe the guys you tuned before were not injecting enough meth to make a differnece to gas' stoich
Last edited by bnice01; Jan 12, 2008 at 01:45 PM.
Jan 12, 2008, 01:49 PM
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i use 2 x 1.0mm jets...they put out 525cc/min water each
meth has lower viscosity/surface tension...dubbleugly calculated once, iirc is 20% more compared to water
meth has lower viscosity/surface tension...dubbleugly calculated once, iirc is 20% more compared to water
Jan 12, 2008, 05:06 PM
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whoops my bad I thought its 945, but still close to gas' stoich
your catching up to me :P, i need to quite being lazy and get this direct port finished
your catching up to me :P, i need to quite being lazy and get this direct port finished
Last edited by bnice01; Jan 12, 2008 at 05:08 PM.
post some pics 
Jan 12, 2008, 05:24 PM
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so your saying that scaling has no affect on fuel delivery. Then why does your fuel trims change when you alter your scaling. So after you rescaleyou would have to go back into your WOT fuel map and readjust the fuel points. You take more or less depending how much you increased or decreaed scaling. Ex. like most of the evo9 guys would be stock or close to it they do the math and would get close to 100% of IDC which I highly doubt they like that. But most injectors are rated @ 42psi
thats not exactly what i said. i said scaling has no effect on the fuel delivery when you have IDC and the rated flow rate of the injector. the scaling is used by the ecu, injector duty cycle is a percentage of the total open time in a given cycle. if your at 50% duty cycle you are approximately using 50% of the total size of the injector. 100% duty you are using 100% of the size of the injector as it is open continously. the only thing changing the scaling does is change the multiplier for how long the injector is open for. for example, if you have a stock injector and run it with the stock scaling, it will work fine. but if you rescale the stock injector to be 1000cc injectors, the car will run extremely lean (and most likely wont run at all). this is because the size of the injector didn't change but the ecu reduces the pulse width because it thinks it is a way bigger injector. try it, take a stock injector and rescale it to be 780cc injectors. you will have to go through your fuel tables and add about 40% more fuel in order to get the tune the same as before. and you will find your IDC will end up being about the same as before you rescaled the injectors (assuming both tunes are hitting the same AFR). so IDC * by the size of the injector is the max CC used, regardless of scaling factor.
I disagree. O2 sensors arent "calibrated" for any particular fuel. They measure oxygen content. Thats why more advance widebands have the option to change lambda becaue they know people run more than just gas
that is also correct (well kinda, you contradicted yourself with the second sentence). for the o2 sensor itself, it doesn't make a difference what fuel is used. lambda will work the same way no matter what fuel is used. but for the case when your wideband will read out in AFR, then you need to rescale the AFR values depending on what the stoic ratio is. i've used some of the most expensive widebands availible (motec), and they would read out in only lambda. it didn't matter what fuel we were using, gasoline, E85 or M85, lambda would always readout about 1 for idling. we had to go in and rescale the output to the laptop though, which would be in AFR.
your still thinking in gas and not taking in the account for meth. I was more less saying while you were tuning the car when meth spraying you would have a different target lambda. Your not running on meth for cruising or @ idle so why would you leave the stoich value for a mixed gas
you are making this way more complicated then it is... i use a wideband that reads AFR for gas, of course the meth changes what the scaling for the AFR conversion would be, but i'm not going to change the scaling factor and tell people they are hitting 10.9 AFR when on the wideband it might show 12:1. most people only know AFR in a 14.7 scaling.
yes thats really rich for gasoline but a car running 100% meth probably wouldnt run and would be consider to be lean because its over its stoic value. But I see what your trying to do with using gas' stoich but when are not running 100% gas its mixed meth/gas. When I said 11.3-10.9 (.85-.8 lambda) it was for wideband set to 13.3 stoich. lambda is nothing more telling you how far you are from stoich or your target stoich if your using a different gas. Thats why you should us lambda, afr values can confuse you. LM-1 is a great wideband to have with tuning meth, I dont know if can change your lambda value.
in your last statement you said why would you set your wideband for a different stoichiometric ratio. now you are saying you set your wideband for 13.3 AFR. you know that ratio is only good at the point you calculated your mixture? unless you actually mix the fuels together and use the same delivery system (i.e. the injectors), the mixture will be different for every RPM and every boost level. if the mixture is different, your stoic ratio will be different. if you are going to that trouble, just say everything in lambda, it will be much easier.
again you werent running enough timing, or boost. meth takes more energy to burn. step up that cylinder pressure. Like I said it depends on how much meth your spraying. The less meth the more closers you are to gas's stoich. ex lets say person another with stock fuel with same IDC as me injecting 945 cc's of meth. His target stoich is 14.6, very close to gas'. So like you said lean it out to 12 (.82 lambda) would make the most power. But me I'm a meth head and spray quite a bit. LOL
i'm not sure what you're trying to say here, but i was tuning the car on a dyno. and since i know how to tune a car (not as simple as adding more timing or more boost), i can assure you that the mixture the AFR was tuned to was optimal. in fact we could have gone even leaner, but since we didn't have EGT's to work with its better to be a little safe. adding more timing induced knock at the boost level we were running. and slowcar ran a ton of meth too....
Like I told ya man it doesnt hurt to try it. I was the same way a couple months ago and acutally tried.
also if you do the math and your stoich value is higher than gas's then your not saying in enough meth to affect gas' stoich. since its the majority of the mix. The target afr/lambda will be same as your using it for gas. and use the injection for a cooling factor.
i am saying i target 12.5-12:1 AFR with a 14.7:1 stoic ratio, or a lambda of .82-.85. we have the same lambda which is the important part.
i didn't know you were stating your 10.9AFR with a 13.3 stoic. no one ever changes the stoic ratio when stating AFRs with meth injection. if you specified E85, M100 or any constant mixture fuel it would make sense. but with a mixture that constantly changes it doesn't make sense.
