MaroonMonsterLS1

So I read alot about dry nitrous and MAF's and can't seem to find the info I need anywhere. Maybe I just suck at the search function so if I've missed a thread, feel free to link it in here.

Otherwise, I'm wondering if you can see a difference in MAF frequency based on jet size. For example, N/A at WOT my stock LS1 sees around 9500-9800 Hz.

With a dry shot pre maf, lets say a 75 shot, will I see around 11,000

Then with a 125 I'll see 12,500

so on and so forth.

Or will the cold nitrous just damn near max the maf no matter what jet size?

MaroonMonsterLS1

anyone?

GM1697

iTrader: (1)

I think most guys are just running wet shots.

Anyone knowledgeable enough to be referencing MAF frequencies would most likely be smart enough to use a wet shot.

In my experience most of the guys running dry shots aren't very knowledgeable when it comes to tuning.

MaroonMonsterLS1

I've tuned wet kits and I'm just not sure where your "smart enough to know better" comment comes from

Monte Smith (I'm sure if you're in the nitrous section you know who that is) built loads of dry kits for some of the biggest names in the game

Typically these are tuned with aftermarket ecu that controls nitrous on its own, but the benefits of the dry kit are the same

Very easy to dial in fuel, much simpler/cleaner install, less cost and solenoids, etc

I know dry kits have gotten a bad rep from people not knowing what they are doing...but the same used to be true for all nitrous considering how many guys would just toss it on a 350 or 302 and grenade their **** cuz they didn't know what they were doing.

So, back to my question...can different frequencies be seen. Or am I going to be stuck with a single kit? I was hoping to see enough variance that I could tune for 2 kits at once with the same tune file

smokeshow

iTrader: (16)

Yes, you will observe different frequencies...so long as the MAF and controller can support it. As I recall the gen 4 and up MAFs had some pretty impressive flow range. So essentially as far as MAF capability is concerned on a gen 4, you would theoretically be good to go. The caveat is that the specific heat of nitrous oxide is lower than that of air, so while the cold temperature of the n2o will artificially skew the frequency reading higher to provide more fuel it will not be linear with regard to the mass flow that actually makes it through the MAF. Unfortunately in this case since the specific heat is lower, as you increase your dry shot size the apparent flow offset from the cold nitrous oxide won't be effective enough to counter the gas itself not carrying as much heat away from the MAF and will go lean. This is why people tend to blow their **** up with dry shots through a MAF. They expect it to be linear and happy but it isn't. You could jack up the MAF calibration to sort of compensate, but it will be fairly sensitive to seasonal DA differences. Calibrate for a 100 shot on a 100 degree summer day and it will start going pig rich motor only in 50 degree fall evening air. Do the opposite and you'll be picking up pieces of grenaded engine as you walk home in the summer heat.

MaroonMonsterLS1

thanks for the info. I was planning on tuning the maf curve (with n2o) using a wideband. Plan on a 2nd stage on a button and wanted to make sure that stage could also be dry.

Tuning for weather will be fine, I will always be checking/adjusting the tune base on the wideband.

I just wanted to make sure that in the tune I would he able to see say a 150 shot vs a 200 shot dry so that when I add the 50 shot on top of that 150, I can add the appropriate amount of fuel too

kbracing96

iTrader: (26)

Just tune it like a you would a boosted setup. You're going to need to map out the MAF curve while spraying. Start with a 35 shot, dial in your AFR in the MAF, then bump it to a 50 and tune the MAF then a 75, ect ect till you either run out of MAF or get to your 200. The more data points you have, the better your N2O part of your MAF curve will be. Keep it on the safe side and you should be fine no mater what pill you have in it.

Keep in mind that dry shots are very common in the after markets ECMs because they run a closed loop WB O2 setup so it's constantly trimming the AFR when they are spraying as well as have already added fuel in a table in the tune for the N2O via the injectors when they turned on the N2O. They have no need to run a wet shot. The factory ECM is not as smart and can only do what is programed. It can't "think" for it's self like closed loop WB can.

MaroonMonsterLS1

Absolutely agree with all your points. I start small and work towards big with every car. I was just worried that with the nitrous being so cold, it would just MAX the maf on any size shot.

Thanks for the helpful info, I hope I can make this work the way I want!