AFR readings help

[NSXonwheels]

AFR readings help (share your safe AFR ranges)

Hello, I have a hi-boost CTSC with water/meth injection.

When I first bought the car I was seeing 11.5-11.9 AFR at wot all the time. Now I can't seem to get it under 12.0 at wot and I'm afraid to get it past 6k rpm to see if it goes lower. I have to say it has been very cold out here in Houston these last few days.

My question is, am I just being paranoid and this is all normal AFR ranges? Is there a different method that I should be using to safely log my AFR numbers to make sure I'm at the right range?

The car feels very strong, it always has, but without putting the car in a dyno or connect to a computer, are there a few things I can do while driving to monitor AFR and make sure my numbers are safe?

Any input is appreciated. My fuel pressure seems good, 38psi at idle, gets up to 55psi at wot. I'm keeping the water/meth tank full so I'm always pumping that during boost to keep things cool.

So am I good or is there something I should be concerned about? Fuel pump, injectors, etc.

Any help will do. Like if I'm on 3rd gear and floor it at 3k rpm my AFR should be this to this. Or if I'm in 5th and floor it at 2k rpm AFR should be around this much, etc. just some parameters for me to test on my next drive and see if I'm within those ranges.

 

[doc_tai]

I would clean and flow test ur water/meth make sure it doesnt clog up. What ems u running? U might need to take back to ur tuner to set up fuel vs temp table to run correct in cold weather

 

[NSXonwheels]

Hey Doc, thanks for the suggestion. I havent cleaned the meth injector but I'm always filling up the tank so I know it's going somewhere. I have AEM EMS, it was tuned by Tony Palo from Dallas, TX in 2007, but I hear he's doing only GT-Rs now so I'm trying to see if there's a few things I can test myself before going to a tuner.

How does the meth/water affect the AFR while it's being sprayed?

 

[doc_tai]

Because meth is also fuel so it does effect afr. Lets say ur water/ meth used to spray 400cc per min but now it clog up and only spray 200cc per min which means less fuel thats why ur car running lean. Water/meth clog up a lot so u have to clean the filter and nozzle a lot to keep it from running lean

 

[NSXonwheels]

Ahhh, that makes perfect sense Doc. I'm on it. Cleaning the nozzle tonight.

 

[LMR]

Is 55psi at WOT normal for that setup? If not there may be your problem. My low boost setup is 101psi at WOT.

 

[NSXonwheels]

LMR, I'm not 100% sure but I think the low boost raises the fuel pressure with a FPR to get enough fuel in the engine, mine has the Walbro 255 fuel pump, and 525cc injectors, which I think deliver the needed amount of fuel at less psi, but if anybody knows better please chime in.

DOC, I cleaned out the meth nozzle last night, there's a video on YouTube on how to do it, super simple, just soak in lime away or CLR, dry and blow air through it. It definitely needed it, had a lot of deposit build up on it and now it looks brand new again. I also have a big bottle of Techron fuel injector cleaner in the tank, once I run that through the injectors, I'll get a fresh fill up and log AFR numbers again.

Does anybody know an easy tip on how to test the water pump? Would that be the next thing I should be looking at?

 

[LMR]

LMR, I'm not 100% sure but I think the low boost raises the fuel pressure with a FPR to get enough fuel in the engine, mine has the Walbro 255 fuel pump, and 525cc injectors, which I think deliver the needed amount of fuel at less psi, but if anybody knows better please chime in.

I forgot about the bigger injectors on that setup.:redface:

 

[NSXonwheels]

Can anybody else share some recommended AFR ranges in different throttle/load/gear scenarios?

 

[racer9x]

Any up dates?