Alky percentage to fuel ratio and tuning for it, numbers not matching

[norbs]

I have been struggling with some issues trying to figure the best safe af ratio by volume, and the numbers are not right to what most are seeing in the real world. It looks like if we have a dual nozzle alky kit this is what I have come up with.

As an example we have an Alky kit running a single m10 nozzle, and a m15 nozzle. The system pressure is 140 psi at WOT.


M10= 10gph@100 psi

M10 new flow rate @140psi= square root (140/100)=1.18 x 10gph=11.8 gph
M15 new flow rate@140psi= 1.18 x15 gph=17.7 gph

Give us a total of 29.5 gph however 1 gal methanol weighs 6.63 lbs

So 29.5 x 6.63=196 lbs/hr you will be injecting in the motor.

At almost 200/lbs that is a lot of alky by volume to fuel.


Lets say we were running 95 lb injectors at 70% duty cycle

95 x 6 injectots=540 lbs x 70%=378 lbs hr

This means that on a ratio scale we have 196lb/378lb x100=52% alky to fuel ratio does this not seem off?

That means we would need an equivalent af ratio shown on your wideband using the gas scale as

new af= (meth% * meth stoich)+(1-meth%)*stoichGAS)
new af=( .52*6.4)+(1-.52)*14.7
=(3.328+7.056)
=10.38

Which means to run 10.38 would mean the same as running at 14.7

This seems way off. I need the experts to chime in please!

 

[murphster]

I would look at the methanol as a percentage of the total fuel. The total fuel would be 196 from meth + 378 from gas = 574 lb/hr. So the meth % would be 196/574 = 34%. That would be the meth% to use for a/f calcs if all the meth injected were burned in the combustion process. But as you alluded to this still seems like too high a %. The corresponding safe a/f ratios would be much lower than what we know works.

I did some quick calcs for the amount of fuel I'm injecting and what I know some of my friends are injecting for low 10sec cars. Using some calculators to guess what fuel the engine needs for those Hp levels I come out with about 22% more fuel needed than what we are injecting. So if we use 22% meth for a dual nozzle setup the equivalent a/f ratios correspond pretty well to what a/f ratios we know works at those power levels (10.3-10.4 or so).

So we are injecting 34% meth but only burning 22% in this case it seems. So what happens to the unaccounted for meth? Maybe even though that extra meth doesn't get burned its still needed to run the higher boost/power levels on pump gas as it cools down the cylinders and prevents detonation.

(Here's where I got my numbers from:
For my low 10sec car, I run around 274lb/hr of total fuel injector when on alky (~55% duty cycle on 83lb injectors). Now, if I use the handy TRX Performance calculator, it says I should be using a total of 350 lb/hr of injector to support my horsepower. I'm missing 76lb/hr, about 22%. If that 76 lb/hr is coming from meth, that number seems more along the lines of the % of meth we are burning to use in the a/f calculations. The corresponding a/f ratios for the 22% meth seem to follow what people have run/recommended for low 10 sec alky cars (say 10.3 for a 11.76 gas a/f ratio). For a high 9 sec car you might want to run closer to an 11.5 gas a/f ratio which would give you an corrected 10.1 a/f ratio for 22% meth.)

 

[bison]

Norbs try using my #'s. 45psi baseline pressure on 3105's@ 72%dc. Two 10gph nozzles, estimated pressure is 180psi. I dont know the exact pressure but it's around 180psi.

 

[norbs]

I would look at the methanol as a percentage of the total fuel. The total fuel would be 196 from meth + 378 from gas = 574 lb/hr. So the meth % would be 196/574 = 34%. That would be the meth% to use for a/f calcs if all the meth injected were burned in the combustion process. But as you alluded to this still seems like too high a %. The corresponding safe a/f ratios would be much lower than what we know works.

I did some quick calcs for the amount of fuel I'm injecting and what I know some of my friends are injecting for low 10sec cars. Using some calculators to guess what fuel the engine needs for those Hp levels I come out with about 22% more fuel needed than what we are injecting. So if we use 22% meth for a dual nozzle setup the equivalent a/f ratios correspond pretty well to what a/f ratios we know works at those power levels (10.3-10.4 or so).

So we are injecting 34% meth but only burning 22% in this case it seems. So what happens to the unaccounted for meth? Maybe even though that extra meth doesn't get burned its still needed to run the higher boost/power levels on pump gas as it cools down the cylinders and prevents detonation.

(Here's where I got my numbers from:
For my low 10sec car, I run around 274lb/hr of total fuel injector when on alky (~55% duty cycle on 83lb injectors). Now, if I use the handy TRX Performance calculator, it says I should be using a total of 350 lb/hr of injector to support my horsepower. I'm missing 76lb/hr, about 22%. If that 76 lb/hr is coming from meth, that number seems more along the lines of the % of meth we are burning to use in the a/f calculations. The corresponding a/f ratios for the 22% meth seem to follow what people have run/recommended for low 10 sec alky cars (say 10.3 for a 11.76 gas a/f ratio). For a high 9 sec car you might want to run closer to an 11.5 gas a/f ratio which would give you an corrected 10.1 a/f ratio for 22% meth.)

I just wonder where the extra alky is going?, now I based those numbers @140 psi, maybe a dual nozzle kit is not running at 140 psi all the time. This also may mean if the ramp starts at 100 psi, we could run a leaner af ratio at the lower pressure, and ramp the af in sequence with alky flow. If you don;t have a stand alone system this would almost be impossible to do.

 

[norbs]

Norbs try using my #'s. 45psi baseline pressure on 3105's@ 72%dc. Two 10gph nozzles, estimated pressure is 180psi. I dont know the exact pressure but it's around 180psi.

I have some data from Julio m15 and m10 dual nozzle was running about 135 psi. But here we go, with dual M10s @180 psi


OK your 83 lb injectors running at 45 psi now flow the equivalent of 84.9 lbs hour x72%= 61.13 lbs/hr x 6=366.80 lbs hr fuel

The alky portion is 20 gph= 26.82 gph@180 psi
26.82x 6.63 lbs gal meth= 177.90 lbs hr alky

177.90+366.8=544.7 lbs total combined fuel

177.90/544.7 x 100= 32.6% alky ratio


NEW AF=[(.326 x 6.40)+((1-.326)*14.7))/14.7] x 11.5
6.4 is the stoich of meth, 11.5 is our af target
[(2.0864+9.9078)/14.7] x11.5= 9.38


If we redo it at 12.00 AF it would be
[(2.0864+9.9078)/14.7] x 12.0=9.8

9.8 AF is what your wideband would show now.



Scott do you want to figure this out at 22%?

 

[bison]

I have some data from Julio m15 and m10 dual nozzle was running about 135 psi. But here we go, with dual M10s @180 psi

OK your 83 lb injectors running at 45 psi now flow the equivalent of 84.9 lbs hour x72%= 61.13 lbs/hr x 6=366.80 lbs hr fuel

The alky portion is 20 gph= 26.82 gph@180 psi
26.82x 6.63 lbs gal meth= 177.90 lbs hr alky

177.90+366.8=544.7 lbs total combined fuel

177.90/544.7 x 100= 32.6% alky ratio

NEW AF=(32.6 x 6.40)+(100-32.6)*11.5)/100
6.4 is the stoich of meth, 11.5 is our af target
208.64 + 775.1=9.84 AF

If we redo it at 12.00 AF it would be

NEW AF=(32.6x 6.40)+(100-32.6)*12)/100

208.64+808.8=10.17 AF is what your wideband would show

Scott do you want to figure this out at 22%?

And it shows 10.2-10.3:1 so I'm leaner would be considered safe. But the cooling effect in the cylinder and retarded timing is keeping the cylinder temp lower. A fairly high volume of alky is feeding a low% of the actual hp. Like 10% or so.

 

[norbs]

I still think you would be considered safe. The question is, what is your actual alky pressure at the nozzle ? You need to datalog this in the fast or some other device. Easily done on XFI but not on a classic box.

 

[bison]

I still think you would be considered safe. The question is your actual alky pressure at the nozzle you need to datalog this in the fast or some other device, if you have a classic fast, instead of an XFI.

I'll put a transducer on it eventually. I was at 16v

 

[norbs]

I'll put a transducer on it eventually. I was at 16v

How many volts does the pump usually run at??????

 

[murphster]

With the default settings in Razor's PAC, a good pump, and no leaks you'll easily hit over 140psi on a dual nozzle kit. You'll probably hit that before 20lbs boost. Typical psi is at least 170-180 I'd guess. I have my ramp adjusted so that the alky pressure peaks at about 21psi and comes in linearly. You need the tester to adjust this correctly but I lowered the turn on and initial while increasing the main gain knob to do this. On the default setting the alky comes in a lot harder.

I'll run some numbers when I get to a computer.

 

[bison]

How many volts does the pump usually run at??????

Idk. Not anywhere near alternator voltage though. I've never checked at the pump when the alternator was putting out 16v

 

[murphster]

I was looking over some of my numbers. I used the TRX Performance calculator to estimate how much injector is needed to run my HP level. But that may be at normal a/f ratios on pure gas. With meth injection we run a richer a/f so the total injector requirement is higher. Sort of like with E85 you need more injector. Running some quick numbers with 25% meth, the total injector requirement goes up roughly the same amount. So the total fuel required for running 25% meth for me would be 350 lb/hr x 1.25 = 437.5 lb/hr. And I have a correction, I ran 67% injector last time out so I injected 334 lb/hr of gas. That means I burned 103.5 lb/hr of meth, about 24% meth.

For Bison, he injected 366.8 lb/hr. With two M10s I will guess he's burning 20% meth. The TRX calculator says you need about 381 lb/hr of gas to run 140mph. At 20% meth that means the requirement is 381 x 1.2 = ~457 lb/hr. If he's injecting 366.8 lb/hr of fuel that means he's burning about 90 lb/hr of meth to get to 457 lb/hr. I estimated I was using 103.5 lb/hr on a M15 and M10 so that seams reasonable since he's using two M10s. So for whatever reason, even though we inject a lot more meth than this, the amount burned seems to be a lot less.

Norb, the formula you posted for corrected a/f is not quite right. It should be:

NEW AF=[(.326 x 6.40)+((1-.326) x 14.7)) / 14.7] x 11.5
which is basically: new stoich ratio/14.7 x desired gas a/f ratio

so for Bisons #s we get a new stoich ratio of: 2.084+9.9078 = 11.9918
This gives a NEW AF of 11.99/14.7 x 11.5 = 9.38

So obviously he isn't buring all of the meth he is injecting if he's running fine at 10.2 a/f.

 

[norbs]

I was suspect of the formula, when I changed the stoich from 14.7 to a new target of 11.5. The formula was correct if I would of left the stoich at 14.7 for gas. Using decimal as % just eliminates the /100 step. Good observation, but I don't like the results your getting, puts us even more off target. I have fixed my mistake in the formula.

 

[norbs]

If we do some more math it looks like Bison could be running at 12.5 AF ratio if his WB showed 10.2


11.99/14.7 x 12.5= 10.19

 

[bison]

I'm not happy with any of these formulas. Doesnt seem possible I could be at 12.5:1. There's definitely a window where it will work without melting cylinders and not excessively rich to where it will hurt power. Charge air temp plays a larger role in my tuning then the amount of alky injected. Probably because I don't have an exact alky volume # to use. But like I've mentioned before I turn the alky pump speed down considerably when the temps drop and pull timing at the same time. When I did this in the past the whp was nearly the same and nearly predictable. Most just don't get that when it's hot you actually can add timing with the alky. The charge air is less dense and the alky has a higher vaporization % so it will pull heat out of the air better. The timing offsets the lost mass flow because of the higher inlet temp. Using egt tuning could cause problems with this type of tuning since the tuner might associate a lower egt with a slight richness at higher inlet temps but it's not since the timing is keeping more heat in the cylinder on the power stroke and the mass flow is less. Fwiw a typical non oxy race fuel engine with the same combo minus the alky would be at 78-80% dc with the same mph I ran but 2* more advance at the boost I ran.

 

[murphster]

If we do some more math it looks like Bison could be running at 12.5 AF ratio if his WB showed 10.2


11.99/14.7 x 12.5= 10.19

I agree, thats why I doubt that we should use the injected meth % for these a/f calcs.

Using the values of 15% for a single M15, 20% for 2 M10s, and 25% for an M10 and M15 seems to give us the a/f ratios that have worked historically and Julio recommends. This would assume we are getting >140psi out of the pump.

I also log EGTs and if we were really running that lean it would show up. On the run I referenced I was 10.4-10.5 a/f and 1469 EGT max on a 10.2@135mph run. The a/f table says I was running an equivalent gas a/f ratio of 12.0 which seems on the lean side. But thats why I use EGT to back it up. I'm running lower timing than I used to also so I could probably bring my EGTs up but I'm trying to stay on the conservative side at 10.4 a/f ratio, high 1400 EGT, and 19* timing.

 

[tonka]

Very interesting topic. One thing I'll throw out there that makes a small difference in the calcs, is that if the gauge used to measure the alky line pressure isn't referenced to intake manifold pressure you need to subtract that before figuring out the alky flow into the intake. In Bison's case, that would mean 180-25=155 psi across the nozzles.

 

[norbs]

Very interesting topic. One thing I'll throw out there that makes a small difference in the calcs, is that if the gauge used to measure the alky line pressure isn't referenced to intake manifold pressure you need to subtract that before figuring out the alky flow into the intake. In Bison's case, that would mean 180-25=155 psi across the nozzles.

Wow good point, also I just thought of this also. The nozzles are designed to flow water, alky has a different specific gravity, so how will this effect flow?

The specific gravity of pure methanol is .792 @ 68° F

Using another formula 1/.792 and we take the square root of that we get a multipler of 1.124 approx. So it looks like a water jet running on meth will flow 12% more volume compared to water.

 

[tonka]

I'm not happy with any of these formulas. Doesnt seem possible I could be at 12.5:1. There's definitely a window where it will work without melting cylinders and not excessively rich to where it will hurt power. Charge air temp plays a larger role in my tuning then the amount of alky injected. Probably because I don't have an exact alky volume # to use. But like I've mentioned before I turn the alky pump speed down considerably when the temps drop and pull timing at the same time. When I did this in the past the whp was nearly the same and nearly predictable. Most just don't get that when it's hot you actually can add timing with the alky. The charge air is less dense and the alky has a higher vaporization % so it will pull heat out of the air better. The timing offsets the lost mass flow because of the higher inlet temp. Using egt tuning could cause problems with this type of tuning since the tuner might associate a lower egt with a slight richness at higher inlet temps but it's not since the timing is keeping more heat in the cylinder on the power stroke and the mass flow is less. Fwiw a typical non oxy race fuel engine with the same combo minus the alky would be at 78-80% dc with the same mph I ran but 2* more advance at the boost I ran.

Curious, when you decrease alky flow and ignition timing to compensate for low air inlet temps, do you still target the same A/F ratio as when you are tuning for high inlet temps?

 

[bison]

Curious, when you decrease alky flow and ignition timing to compensate for low air inlet temps, do you still target the same A/F ratio as when you are tuning for high inlet temps?

I go slightly richer.