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Antihero
Antihero New Reader
3/31/16 3:32 p.m.

Never used it but it's looking like it'll be in my challenge car build.

I've decided on a wet system and it'll more than likely be installed in a carbed sbc. What should I look for in a cheap decent setup?

The Hoff
The Hoff UltraDork
3/31/16 3:44 p.m.

Make sure the floorboards are properly secured?

84FSP
84FSP HalfDork
3/31/16 4:40 p.m.

This is relevant to my interests. Can't do much and stay legal with the rabbit gti in FSP. Was thinking a nitrous setup that could be easily removed/disarmed might maker a bit more spunky with a 50-75 shot....

dropstep
dropstep Dork
3/31/16 4:52 p.m.

Make sure the tune up is safe. Start small and step it up. I used a peiced together plate kit on my capri. The tank and plate were part of a used sniper kit. Adjustable 75-150. Keep a spare selenoid!

When i switched to nitrous we went one range colder on the plugs and pulled ten degrees of timing too start. Mine was hooked up with a WOT switch not a button.

84FSP
84FSP HalfDork
3/31/16 6:42 p.m.

I like the wide open throttle switch option. In case anyone missed it, Pep Boys fill nitrous tanks at a normal going rate as well...

patgizz
patgizz UltimaDork
3/31/16 7:55 p.m.

for brand new budget friendly i really like the nitrous express mainline kit. however, some of their bottles ship with goofy valves that don't accept blowdown tube fittings. i called and they sent me a prepaid ups label, fitted my bottle with the newest(not even out yet for retail purchase) highest flow lightning valve and shipped it back to me free of charge. for that customer service, i'll keep buying their kits. i have one on my challenge car(datsun Z) and one on my belair. will be putting one on my impala ss too.

Antihero
Antihero New Reader
4/2/16 3:33 p.m.

Thanks for the responses.

I'm gonna have to drive my challenge car 2700 Niles one way so I really want to make sure it doesn't effect streetability. I may just swap to colder spark plugs in the parking lot etc.

I've read stories about slamming huge shots of nitrous into stock sbcs but I doubt ill eclipse 100hp shots. Wot switch seems safest and easiest too

pimpm3
pimpm3 Dork
4/5/16 11:19 a.m.

Does the nitrous need to have extra fuel added somehow? If so how does the computer deal with that? I am thinking of adding a 100 shot or so to my LT1 powered Trans Am. Is it as simple as jetting it into the intake, and a set of colder plugs or is there more to it?

dropstep
dropstep Dork
4/5/16 11:50 a.m.
pimpm3 wrote: Does the nitrous need to have extra fuel added somehow? If so how does the computer deal with that? I am thinking of adding a 100 shot or so to my LT1 powered Trans Am. Is it as simple as jetting it into the intake, and a set of colder plugs or is there more to it?

A dry shot is the easy button but not neat as safe. Id do a little research on the motor itself and see if theres any advice on what it can handle dry.

A wet kit isnt much harder too plumb and provides its own fuel. Im not sure how you deal with timing on something fuel injected short of a tune for it.

rslifkin
rslifkin HalfDork
4/5/16 11:55 a.m.

Timing depends on how the ignition system is done. If it's single coil and distributor, you can put a retard box between the ECU and the coil to delay the spark slightly when the nitrous is spraying.

Opti
Opti HalfDork
4/5/16 1:06 p.m.

Dry system just injects nitrous pre MAF and lets the stock fuel system deal with additional fuel.

Wet systems inject both nitrous and fuel.

They both have their advantages, I prefer wet kits.

You can retard timing with an ignition box like the MSD 6a or Mallory 685.

You can use a window switch were it will only spray at certain rpms, that way you dont shift into the wrong gear and spray at 1500 rpm.

WOT switch, where it will only spray at WOT

Fuel pressure safety switch, it will not spray if your fuel pressure drops below a certain threshold.

pimpm3
pimpm3 Dork
4/5/16 1:19 p.m.

Opti:

I know you are familiar with the LT1, what kind of a setup would you recommend for a 97 LT1 being built for this years challenge. I have never used Nitrous before and am a complete novice in that regard

Keep in mind the car is being built entirely in the parking lot of the hotel the day before so tuning is not an option. It needs to be a plug and play. I am fine with a smaller shot that is safer, I need the engine for 2017 for that years challenge S10.

Opti
Opti HalfDork
4/5/16 1:45 p.m.

If its a stock motor untuned, either would probably work. Id use whatever I could find cheap and used, I'd spray 150 on it.

I used to frequent a local pool hall and there was a really ratty WS6 there and the guy who drove it did not seem very mechanically inclined or smart and he sprayed a 150 dry shot on a car in questionable condition for many years.

As far as building your own kit for cheap, thats above my pay grade.

thatsnowinnebago
thatsnowinnebago SuperDork
4/5/16 2:38 p.m.
rslifkin wrote: Timing depends on how the ignition system is done. If it's single coil and distributor, you can put a special box between the ECU and the coil to delay the spark slightly when the nitrous is spraying.

FTFY.

ssswitch
ssswitch HalfDork
4/5/16 4:17 p.m.

I've been really curious about this too but it seems like for most sport compact applications much more than a dry 50-shot is not safe.

What I came away from quick research was, once you've got the engine management you might as well just go Chinacharger for less total money and hassle. I hope to be proven extremely wrong by this thread.

I saw one setup (the Holley dry kit) that appeared to be using a tee with vacuum on one side and nitrous pressure on the other to decide who gets "control" over the OEM fuel pressure regulator to provide the necessary fuel but that seemed really sketchy (and also, as has likely already become apparent, I do not understand fuel pressure regulators).

Do the wet kits just tee off of the existing fuel feed line and have their own injector? I can't imagine wet kits run a second pump, feed and return lines for the nitrous line.

edit: Cool, I just reinvented what a wet kit is instead of googling it. Maybe I should call back that HR person at NASA after all..

To answer my own question, since probably other people are curious and I would have loved to read this sentence before I made my ignorance known to the entire internet: the wet nitrous kits have a fuel solenoid and a nitrous solenoid, and the fuel solenoid is fed from a hole tapped into the fuel rail (the fuel pressure test port, if you have one - I have one). They're both brought down into a single carb-style jet on the intake plumbing so that when you activate both solenoids you get a nitrous/fuel mix. As long as you don't run out of fuel capacity it's fed better and can be metered more accurately to the demand than the dry kit.

edit 2: I called back the HR person; I didn't get the NASA janitor position after all. Need a double Ph D in janitorial services.

dropstep
dropstep Dork
4/5/16 5:14 p.m.

Yeah you can run a prettygood sized wet shot that way. Alot of the guys with 2-3 kits run a seperate fuel pump just too feed the nitrous.

bentwrench
bentwrench Dork
4/5/16 6:44 p.m.

I would not even consider a dry setup, Nitrous is an oxygenator you HAVE to add fuel or you will have the equivalent of a cutting torch or worse a bomb.

A conventional EFI system uses a fixed fueling table at WOT and will not compensate for added oxygen.

You do not want to use nitrous at part throttle, a WOT switch is a good thing, a window switch is a bonus.

So a wet system is the only reliable and sane choice. Plate systems work but high power shots need to be port injected fuel and NO2 to provide matched cylinder to cylinder NO2 and fuel. A plate system suffers from distribution issues which usually end bad for any big shots.

Also when using NO2 you want to short shift and limit RPM, grab gears and make it eat. Torque peaks at a lower rpm than without spray. Torque is what moves the car, HP is a mathematical expression used by salesmen to impress farmers.

Opti
Opti HalfDork
4/5/16 7:24 p.m.

A plate system isnt all bad and is generally good for about 150-200 on a normal V8 intake with a front mounted tb (or rear or side).

A plate mounted on a single plane carb style intake doesnt have the cylinder distribution issues as much as stuff like a TPI/LT1/LS1 intake.

HP wins drag races in an optimized setup.

People have used dry setups for quite a while with good results, I wouldnt rule out a dry setup especially on something were they are well documented, and budget is a concern.

I see no reason to shift early, because a normal nitrous setup doesnt care what rpm your at, as long as the window switch is engaged, and sprays the same amount of nitrous and therefore you would be safer spraying at a higher rpm, since less nitrous will be used per power stroke, hence lower cylinder pressures. Thats the whole reason window switches are used. Thats why when you look at a nitrous dyno, with a non progressive or staged setup, there is a huge jump as soon as they start spraying and it tapers off as rpms rise. The system is spraying the same amount of nitrous through the whole rpm range.

rslifkin
rslifkin HalfDork
4/5/16 7:30 p.m.

They do also make multi-step systems where it can have 2 or 3 different size nozzles and steps up as the rpms increase.

Opti
Opti HalfDork
4/5/16 8:42 p.m.

And they also make progressive controllers so nitrous flow is stepped up to the full amount over a given time, to alleviate the massive torque spike when you first spray and its affect on the chassis/drivetrain/motor/traction

Paul_VR6
Paul_VR6 Dork
4/6/16 5:54 a.m.

Some thoughts...

Safe shot size rule of thumb is 50% of stock power, you can do more easily but it will require some thought

Wet with efi is a pain, and on a small shot I would run dry (fuel compensation by n2o pressure to the fpr, or by the ecu if you have control over it)

V8 carb plate setups are everywhere and stupid cheap, use them if you can

Think about timing, fuel and plug choice when over the 50% rule above

Its addictive, be warned.

rslifkin
rslifkin HalfDork
4/6/16 8:11 a.m.

Wet shouldn't be any problem with most EFI. And a lot of EFI systems don't have a fuel pressure regulator, so unless you tune on the assumption that you'll always be spraying, you're SOL for a dry shot. And if you tune that way, then it would run unbearably rich if you ever go WOT without spray.

Paul_VR6
Paul_VR6 Dork
4/6/16 8:35 a.m.

Wet shouldn't be a problem on EFI? How many have you tuned with good results? My list is small and the caveat list of making it work well makes it not worth it for the n2o neophyte.

In my experience with a small shot on EFI (3bar+ base pressure) it's VERY hard to tune because of the fuel jet size needed to not make it extremely rich. I have had problems with the small orifices clogging even on well filtered setups, which can become disasterous. You can make some older low pressure EFI work well with wet setups, OR run a dedicated low pressure fuel system for the nitrous. Now if we're talking a big shot, it's a different story, but I was under the assumption that we're talking reasonable ranges and not doubling or tripling stock horsepower.

Very few EFI systems don't have a fuel pressure regulator. Only the newest ones (which likely aren't in a challenge budget anyway!) have fuel pump control to maintain pressure. Dry shots are the easy button for EFI on a small hit.

That being said my favorite part about nitrous is when you are wrong, you can usually tell how wrong by what's left on the track.

rslifkin
rslifkin HalfDork
4/6/16 8:39 a.m.
Paul_VR6 wrote: Wet shouldn't be a problem on EFI? How many have you tuned with good results? My list is small and the caveat list of making it work well makes it not worth it for the n2o neophyte. In my experience with a small shot on EFI (3bar+ base pressure) it's VERY hard to tune because of the fuel jet size needed to not make it extremely rich. I have had problems with the small orifices clogging even on well filtered setups, which can become disasterous. You can make some older low pressure EFI work well with wet setups, OR run a dedicated low pressure fuel system for the nitrous. Now if we're talking a big shot, it's a different story, but I was under the assumption that we're talking reasonable ranges and not doubling or tripling stock horsepower. Very few EFI systems don't have a fuel pressure regulator. Only the newest ones (which likely aren't in a challenge budget anyway!) have fuel pump control to maintain pressure. Dry shots are the easy button for EFI on a small hit. That being said my favorite part about nitrous is when you are wrong, you can usually tell how wrong by what's left on the track.

Chrysler moved their pressure regulators to the pump module in the 90s. That is a good point about the small jets though. I wasn't thinking about issues with supplying a small enough amount of fuel at 50-ish psi.

dropstep
dropstep Dork
4/6/16 8:45 a.m.
Paul_VR6 wrote: Wet shouldn't be a problem on EFI? How many have you tuned with good results? My list is small and the caveat list of making it work well makes it not worth it for the n2o neophyte. In my experience with a small shot on EFI (3bar+ base pressure) it's VERY hard to tune because of the fuel jet size needed to not make it extremely rich. I have had problems with the small orifices clogging even on well filtered setups, which can become disasterous. You can make some older low pressure EFI work well with wet setups, OR run a dedicated low pressure fuel system for the nitrous. Now if we're talking a big shot, it's a different story, but I was under the assumption that we're talking reasonable ranges and not doubling or tripling stock horsepower. Very few EFI systems don't have a fuel pressure regulator. Only the newest ones (which likely aren't in a challenge budget anyway!) have fuel pump control to maintain pressure. Dry shots are the easy button for EFI on a small hit. That being said my favorite part about nitrous is when you are wrong, you can usually tell how wrong by what's left on the track.

When i first started thinking about nitrous on my capri i talked to an old guy at the dragstrip about how to tune for it. His recomendation was keep going up a jet until something broke.

Then go back down a jet with the new motor. Your line about parts on the track reminded me of that.

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