RomRaider

I'm starting this thread as a basic how to when using meth injection. I've read so many post about guys trying to use this stuff and really have no idea what they are doing. I've seen so many guys trying to run anywhere from 12 to mid 13 total afr on meth while not knowing what there actual gas afr was. This stuff is dangerous if not tuned correctly.

To begin with, you need to know your actual afr with meth and your actual gas afr. The actual gas afr being the most important. Rich best tq for gas is between 11.8-12.7 lean best tq is between about 12.8- 13.3. That may vary some depending on were you are getting your information. On a forced induction engine I prefer to keep afr in the rich best tq range.

The true gas afr is were you will be making the most power using fuel. Timing and boost are also used but im just going to overview how to tune your fueling for max power on meth. Meth injection by itself does NOT make horse power. In fact, it actually will cause you to lose power if just hooked up to your current tune and sprayed. The water and meth takes up space in the cylinder that could otherwise be taken up by gas and air. Gas and air is what makes power. Meth injection only helps to cool the intake charge and absorb heat in the combustion chamber. It adds an octane affect by doing this. It has been tested and proven that you get the best cooling affect with a 50/50-50/75 water to meth mix.

After the kit is installed, log afr before you turn the meth injection system on. Note wideband afr. Meth injection can be set to come on anytime between 1-22 psi. I prefer 10 psi because I run a lean spoolup afr up to around 10 psi, 15 psi on a larger turbo.

Now turn on the injection system. Do a pull and note afr with meth injection on. If your afr drops richer by a point or more, you are spraying to much meth. On most setups, a .50-.75 drop in afr is all that's needed. If your gas afr was 11.0 (no meth) and now its 10.3-10.5 (with meth) your golden. If its richer you need to either A) turn down pump pressure or B) install a smaller nozzle. The less meth injection you can use to deter det, the more power you will be able to make.

Now you've got the correct amount of meth by the afr drop. Now turn your boost up to desired boost level. If you experience det, either 1) back off of timing or 2) you may be trying to run to much boost for your setup. You may increase your meth spray amount down to a 1 point afr drop if needed. Don't go more than 1 point richer afr drop or your just going to kill your hp numbers. Nine times out of 10 as long as your turbo is efficient you may run 25-27 psi with no sign of det on a .50 richer afr drop. A lot more depends on that like compression ratio etc etc. But on a typical setup on a wrx/sti, this how to applies farely well.

With your meth spray amount set correctly and your desired boost amount set, you can now begin to tune your fueling. Let's use a gas afr of 11.0 and you have enough meth spray to give you a .50 afr drop (10.5). You can now start leaning out your total afr. You want your true gas afr to be in the rich best tq range to make the most power from the fueling part of your tune. If you are able to tune your total afr to 11.7, that will give you a 12.2 true gas afr. Try to lean out to a total afr of 11.9-12.0. That will give you a gas afr of 12.5. That will put you right were you are able to make the most power with your afr.

If your setup naturally has a low det threshold, you may have to run your true gas afr on the rich side of rich best tq. This will raise the det threshold without having to add water/meth. Remember, water/meth does not make power. If you do have to add more meth spray, Do Not lean your total afr back out to 11.9-12.0. That would put your gas afr at 13.0 or leaner. Always be aware of your true gas afr and the total afr drop you will see with meth. As I stated earlier. If you are seeing more than a full point in afr drop, you are probably spraying to much meth/water.

Now that meth spray, boost and true gas afr are all set, you can try to add a little more timing. I'm not big on throwing a s*** load of timing at a motor. But I will add a couple more degrees if the tune will let me. Some tuners may tune with meth so there true gas afr is in the lean best tq range. Thats ok too on a built motor. But if your having to spray so much meth that your afr drops more than a point, you are killing your hp numbers.

This how to is for typical wrx/sti setups. If your putting down over 500hp to the wheels, you may need to have a lower than one point afr drop on meth. But that isn't typical of most setups. I hope this helps some newbs trying to use meth injection. If you have further questions feel free to ask.

Ed

Thank you for this great write-up! I am in the process of installing a water/meth kit, and am researching the tuning process.

Just so I'm clear on the terminology,

Total afr is what is seen by the wide-band?

True gas afr is what is targeted in the primary open fuel table?

For instance, say I've tuned the car for 11.3 afr gas only as seen by the wideband, introduce the water/meth injection, see that it has now dropped to 10.8 afr on the wideband. Remove fuel from the POLF table until I again see 11.3 total afr on the wideband.

Is this correct?

And if so, is it then ok to tune to 11.7 total afr seen by the wideband as long as there is no det?

Thanks!

Your true gas afr is the afr without meth. Not what is in th open loop table. Chances are your gas afr won't follow the exact changes you make in the open loop table. Just know what your afr drop with meth is and depend on the wideband for total afr. Then you can figure what your true gas afr is from the set afr drop with meth.

Only depend on the wideband, not values in the open loop table.

Great write up, clear and concise.

Quick question - I'd like to relook at my meth setup, about to upgrade it, and I know that it's currently overspraying (was set up that way when installed, I never got round to adjusting it...).

My MAF scale was adjusted up at the top end to reflect wideband = open loop fueling table. So in working backwards now, I believe the workflow should be:

* Adjust the high load areas in the fueling table to a safe AFR (currently 11.5) - say 10.5 AFR
* Adjust the MAF scale upwards in those cells (4.5 upwards for me) that were adjusted - to reflect true gas AFR
* Tone the boost down to something reasonable, say 1.2bar
* Do a couple of WOT runs, make sure the MAF scaling is lining up tightly at the top end.
* Switch meth on, note how much AFR is dropping. I'm running a Dom 3 XTR and high boost (26~27psi) so I might need a little more than 0.5 AFR drop I think? It's a built block (sleeved as well)
* Adjust fueling table back to 11.5, maybe 11.7 AFR and boost up again.

Here's my question - would the MAF scale need to be readjusted then in those cells (so open fueling table = wideband AFR)? Otherwise, I assume one would see say 11~11.2 when the tables are calling for 11.7?

Thanks again for the write up.

You can use either the maf, open loop map, or both. It doesn't really matter what values you end up with in the open loop table. You have different ways of adjusting IPW. Use what works for you and what your comfortable with.

The most important thing is the wideband. Just know your true gas afr and your total afr with your meth drop.
I personally will mostly use the open loop table over the maf scale. You obviously will have a higher load with the boost up to 25 psi or more. You can taylor the open loop table to meet your fueling needs while on meth and while not on meth. Use your load axes to do this.
The open loop values will more than likely not match afr.

The amount of meth to spray will depend on different factors. If you are spraying enough meth to drop afr more than a point, and your making 350hp you need to stop and rethink your tuning strategy. At 350hp, a .50 afr drop should be plenty of spray. On your setup (dom 3) I would say that a 6-8 gph nozzle would be ideal. You can fine tune the spray amount by the line pressure.

Its really hard to tell everyone how to tune a setup without writing a whole book with different formulas and reasons. This is a generalized writing at best. The tuning part or the process used to achieve a goal is up to the individual tuner. if your engine is a high compression ratio, your tuning strategy will change. But, for a typical stock compression motor making typical hp numbers, this generalized writing should help you achieve more hp out of your setup than would otherwise have been possible if you don't know how to use meth/water injection.

Ed

Many thanks, Ed - that clears it up for me nicely.

I'm sure that I'm losing power at the top - and I never thought to check on whether the meth had really been set up properly by the shop / tuner when it was set up. Only now that I'm working with a new kit, have I realised that it must have been spraying if I'm not mistaken close to 2 AFR points from true gas, ridiculously too much - which also explains why I was not getting what I should get from the top end.

I'll start tweaking it, and see how it goes.

Hey Ed,
Sent you an email, hope you get back with me!
-Just incase you dont check that email-

Turns out I Cant do that yet.
fastblueufo, can you get in touch with me im developing my own Methanol Inj, and i could use help with working out a few questions.

Email me at yahoo.com

I know these kits can be expensive, anyone know what pumps are good and what else is needed?

Thanks

For the money you can't go wrong with the snow performance kit. To me its one of the better on the market for under a grand.

when spraying 100% water, what AFR change is generally expected given the nozzle is correct per installed fuel injectors?
any tips on tuning with water only?

I haven't started to tune with methanol yet. But my guess would be a leaner afr when tuning with water only (if temp sensor is before meth nozzle).

When tuning with water the afr will still go richer when spraying. You are displacing oxygen molicules with water molicules. The wideband senses this and shows a richer afr because of the displaced oxygen.

so that means I also have a choice of leaner AFRs or more timing, right?

hmm... timing it is then!