Question about a DRY NOS setup


Not quite normal
May 25, 2001
I once read that the "dry" systems inject nitrous before the maf and the computer will then automatically compensate with addittional fuel.

Is this true and would it work on a TR?

I am going with a T+ and LT1/LS1 maf and trying to decide where to put the maf (pre or post turbo/ic). I might someday want to run a nitrous shot to aid spoolup. I would assume that I am not going to exceed 255 g/s but would be at WOT and under 3500 rpm.

umm.. well that would be a waste of NOS only because you shoot it that early and it still has to travel through the turbo, intercooler, up-pipe then the TB before it is effective. The NOS will disperse and give the motor a real effective charge as if you shot it into the up-pipe. And i dont think the MAF knows what NOS is anyhow to adjust the computer for proper fuel... but what do i know.
Maybe I wasn't clear enough. I would be shooting the nitrous into the uppipe before the relocated MAF.

Anyway, I think I found the answer on the Holley/NOS site. Their dry systems either increase the fuel pressure or the injector pulse width to provide the extra fuel.

I wouldn't rely on it that's for sure, will a dry system work with our fuel pressure regulator?

Don't they make psuedo pressure on the vaccum side of a typical regulator to rasier fuel pressure. So does the solenoid (or whatever) that does this have an input too, so that it will add fuel on top of you fuel at max boost.

You might end up needing a serious fuel pump. Seems awful easy to lean out a turbo motor as is. Maybe that's why people like Red Armstrong got away from NOS so quickly.
I'm pretty sure several of the ls1 guys are doing what you suggest. Inject a dry shot in front of the maf, the maf sees the extra oxygen and in turn increases the fuel going into the engine.
I'm almost positive that if they are using the LS1 kit from NOS that it has a hookup to the fuel pressure regulator which increases the amount of fuel coming from the injectors. And besides that there are a lot of differences between the LS1/LT1 MAF and our old school GN MAF's. was eating me alive so I looked it up, you're right that is how it works. Scary, I wonder how it works. It's got to plug into the maf and tell it when the NOS is activated.....or something. This is from Jeg's website.

LS-1 System ''Dry''
Turn your late model Camaro into a 12 second rocket. This is a ''dry'' system that only injects nitrous oxide into the intake tract and
relies on the factor E.F.I. to provide the extra fuel necessary, its that simple. Easy to install and tune and yet delivers an honest 125
horsepower. All required electronics are included to enable the OEM computer (ECU) to compensate for the extra fuel requirement on
demand. Jets are included with the kit that allow the user to adjust power outputs to match available traction. The system can only be
activated at wide open throttle and comes with a saftey shut-off in the event fuel pressure drops below what is required to maintain an
adequate flow. As with other NOS kits, everything required for a complete professional installation is included (hardware, electriacal,
plumbing and detailed instructions). Includes a big 15lb. bottle, Super Hi-Flo valve and nitrous pressure gauge.

Getting the right amount of matching fuel can be hard enough by itself, but that's only half the juice equation IMO. Personally I would never put 125 hp of nitrous on my factory tuned LT1/LS1 without timing retard of some kind. They run max timing as is for max efficiency, and then some expect it to combust and deliver another 125+ hp worth of air/fuel without rolling back the timing. Well that's like waving a reg flag while standing in front of senor Bully IMO ;-) Eventually you'll be wishing you had a platoon of rodeo clowns around you to get senor Bully off ya ;-) Plus alot of these folks apparently think they can still do all that on pump gas too <sigh>.

Most of the matching fuel schemes are pretty kludged up too IMO. Not saying they can't be made to work, just backyard as h*ll and very risky. But something is probably better than nothing, at least for awhile.

I couldn't agree more. Sometimes I wonder if NOS and engine buidlers have a behind the scenes deal. Oh well, throwing caution to the wind is like pissing away money.
I see that Granetelli has a dry nos version of their maf. It is supposed to be calibrated specifically for the dry nos systems.

Niether that fact, nor the Jegs blurb really confirms that the MAF is sensing the extra oxygen benefit of the NOS, IMO. But it makes me wonder.

The Holley/NOS site did specifically say that the difference was that THEIR wet systems inject the fuel with the NOS and THEIR dry systems manipulate the fuel pressure or injector pulse width. Doesn't say whether directly via electronics or indirectly via the automatic sensing of the NOS by the MAF.

Even that Jegs blurb mentions "All electronics are included...".

Soooo, does anybody out there KNOW the answer?

Either way I wouldn't try a setup with a turbo car of any sort unless I was ready to tear the heads off the car on a regular basis. Due to the fact that a lean condition at spoolup is going to be compounded by faster spoolup and more lean air fuel. Assuming all of this happens before the ECM can catch it, I would think spikes of KNock would be pretty drastic using nitrous, and all of the 10 sec or faster GN's I know aren't using it, some of them have been owned by the same dude since 86 too, there has to be a reason they aren't using it. Don't try to reinvent the wheel, only try to put your own spin on it.

I agree that the maf shouldn't have the ability of sensing the difference between NO2 and ambient air. However, I know that Thrasher has mentioned trouble with an over rich condition on SC3800's when Nitrous is sprayed in front of the MAF. This is the reason for them making their nitrous plates.
I have seen probably 20 Dry Kits on LS1s. YES there is no Fuel enrichement. The Maf senses the Denser air charge and richens the car up. Its that easy. Run a line to air box and Spray it.

Think about the GN, We already max out the Maf at 255, so spraying NOS (sorry its shorter) through it will not add any fuel. I asked this before about using a translator since it will read higher but I dont think anyone has tried it. I wouldnt.

I would make sure to use a Wet Kit, NOS and Gas Solinoids....

Just my 02s...
If you got the extender chip, translator+, and the larger 3.5" MAF wouldn't that read beyond 255 for better fueling?

Not an expert but maybe that is a solution to the dry system problem?

Good point Salvage....

I wonder how the MAF does that, does it also have a temp sensor? Even then you'd think that -20 degree air wouldn't have as much o2, as NO2 does.

Here's what I was thinking about the matter though.

LS1 NOS kit = $500-600
NOS accessorys needed with kit = $100-300
LS1 MAF = $200-300
MAF Translator + = ?? $250

That's anywhere between $1050 and $1450, that'll buy a lot of whosyourdaddy for even the most stock turboregal/TTA.
Airflow cools the "resistor"... and... NOS cools the resistor, making it think it needs more fuel. Fueling is based on a long equation where the MAF is one variable.

The LS1 Kit I just looked at will add the same amount of fuel whether its jetted for 75 or 1,000,000 HP - since "cold" is "cold". Lower HP will likely be rather rich.

You guys nailed it: Wont work on a TR. Airflow works the same way but not enough resolution... not sure about the extender setups. Good question.

I think you mean "not enough range"? Too bad our MAFs and 8 bit reading peaks at 255 g/s.

Meanwhile we have several LS1's around here in the upper 120's mph with minimal ecu tweaking, and one even ran 10.80 at 135.x last night with a small hose shot on top of intercooled Vortech. Too bad we didn't have that sort of MAF sensing and control range stock.