spraying nitrous

[Rootie524]

hey. my plans are to build a high compression engine w/ a strip cam. i was going to leave it NA..but im power hungry..so im wondering if its ok to spray a high compression engine with nitrous. id probably only ever do a dry kit. i didnt know if its like a turbo and needs low compression or not so thats why im asking.

[mickaz]

nitrous is better with a high compression engine, but I recommend going with a wet kit. If there is no tuning a dry kit will kill your engine pretty quickly.

[Rootie524]

oh awesome. so it will work better with what im doing. and i was always under the impression the a wet kit is more harmful to the engine. how would that be installed on the 3400 anyway? can something go on the fuel test port..that AN thing its called iirc.

[robertisaar]

wet kit is MORE harmful than a dry?

quit reading ricer forums, that's the level of intelligence in that statement.

N2O basically adds a shitton of oxygen instantly, and if you spray after the MAF, the PCM won't know about it and will NOT add the extra fuel that the extra oxygen requires and you'll quickly melt a motor. if you sprayed before it, you may max it out or damage it(AFAIK, MAFs don't play well with it, but i may be wrong) and revert to speed-density, which won't register the added oxygen either, resulting in a lean condition.

best advice from me on this: if you really feel the need for N20, go wet or direct port(if you have the money) and use VERY rich numbers on the fuel nozzles and lean out if you have some idea of what the AFR actually is and is too rich for max power.

[Rootie524]

i dont get why im being yelled at and told i read ricer forums. from what u just said it sounds like a wet kit is indeed the candidate for more engine wear risk. which is what i had previously said. call me stupid if im still wrong..cuz then i dont get ur point.

wet kit will "quickly melt a motor"....

[robertisaar]

there isn't any yelling going on...

how would a wet kit be more destructive? wet injects the extra fuel necessary for proper combustion from the same nozzle that the N2O comes in from, as opposed to a dry kit just hoping that the ECM knows to dump extra fuel...

too rich: you buy spark plugs, too lean: you buy pistons.

[Rootie524]

i just think i dont understood ur post. when u said this : "if you spray after the MAF, the PCM won't know about it and will NOT add the extra fuel" were u still referring to a dry kit but just spraying it after the MAF. i assumed u were talking about a wet kit after the MAF there..but now it makes sense that u gave me the scenarios for a dry kit before and after the maf.

[3400-95-Modified]

Never spray straight nitrous into a maf... that wont work at all. You will freeze the sensor and the ECM will go haywire. There is no need to switch to speed density either, you could EASILY compensate for a dry shot if necessary, BUT only if you have a wideband sensor to verify your getting enough fuel when running N/A.

Nitrous is ALWAYS to be induced AFTER the MAF sensor and typically just before the TB opening, OR after it if you have a spacer plate. If your doing direct port then you need to be in the same location or extremely close to where the injectors are for best performance.

And Dry is for ricers who don't have the money for a wet kit and want NAWZZZZ, OR for someone who runs a carb fueled dragster and it never hits the street and is properly jetted for that induction type.

Wet kits allow you to run 100% normal on the street and at WOT with no spray because your not dumping extra fuel all the time to compensate for the nitrous. The only way you can run a dry kit is to have the ECM running at 10 a/f when at WOT with no spray, so once you are spraying it will drop to about 11.5 a/f... Problem with that is your running so rich all the time on the street.

I use a wet kit and I have run a 100 shot on a stock 3400 and had very little issues... I popped a few headgaskets but most were due to unlevel heads and also using cheap felpro gaskets that got eaten away by coolant. Hell the pistons I sprayed the most on are still in the car I was driving daily back and forth to work, that motor is still all together and none of the hard parts had to ever be replaced. I think if I had the head studs on that motor and a set of GM gaskets and a GM timing chain I probably wouldn't have had as many problems as I did with it.

[Guest]

......


"Dry kits" do have a way of adding fuel, but it's not as easily metered as wet kits, nor is as predictable in the way the addtional fuel will be added, or rather how much. Dry kits will have a connection to the fuel pressure regulator that through using the pressure of the nitrous (and a meterting jet), will put pressure on the diaphram, to close off the FPR. The problem with this is that not all FPRs, especially stock ones will be able to close off any more than when no vacuum is present. This is part of why Dry kit is kept to lower HP increases, typically less than 50 HP, which is really a misnomer, since it is rarely ever exactly 50 HP.

I've also never seen a dry kit used on "race only vehicles".

The tuning that could be need to make a dry kit run on a vehicle will not cause you to run rich, at least not all the time, especially when tuned correctly. The increased delivery of fuel would only need to be above the RPM at which the nitrous would be activated, typically no lower than 3000 RPM, and if you know enough about tuning you can use PE vs TPS tables to add the additional fuel only above certain throttle angles. But really this is getting way more in depth than it would need to be.

There is an issue with wet kits on engines that run MPFI, since most of these intakes are of the "dry flow" type, meaning they transfer only air, except for maybe the last couple inches of the runners. Because of this dry flow design many of these types of intakes will have poor fuel distribution, and can cause some cylinders to be rich, while others will be lean (there are reasons to tune systems like this, but that's very in depth nitrous tuning). This poor fuel distribution can cause blown head gaskets, damaged pistons, etc. Ford 5.0L engines of the mid '80s to early '90s had fuel puddling problems, where fuel would come out of suspension and et deposited in the botom of the plenum, and many times would ignite, causing the intake to blow apart. The 3400 intake isn't nearly as bad, for puddling, but not sure how the fuel distribution would work out, I could see problems though.

There have been people that have been successful in spraying nitrous before the MAF, and it works because the MAF wire is cooled, causing the ECM to read an increase in air flow, which will add more fuel (longer injector pulse width), but it's not a recommended way to do it, only very experianced people should even attempt it.

I guess I need to get rid of that dry kit I have, don't want to be a "ricer".

[Rootie524]

thanks all for the help so far. sounds like im going wet haha

but anyway 3400modified..how do u have ur kit set up and did u take it to the dyno to get some numbers when NA and with ur 100 shot? and id definitely get the cometic head gaskets and have the heads milled so its flat and use the arp bolts w/ a double roller timing chain and new pistons and the naiper rings that wot tech sells to eliminate hopefully all sources of potential problems while being sprayed. and would this involve bigger injectors or would i be fine? i think after my engine build ill need to end up going to the 28#s for the trailblazer

[3400-95-Modified]

When I was running it on my stock 3400 yes I did bring it to the dyno, I got around 143whp n/a with the auto, and then 206 with the 100shot of spray. and IIRC I was still on the rich side. And remember this was also on a OBDI.5 non tunable ECM so I couldnt do anything but spray and monitor the A/F and adjust the fuel jet to get it right. This also brought me from a 15.3-15.4 to a 13.811 (best time ever with the stock 3400 spray)

As far as what The_Raven said... he took a lot of what I said either out of context OR tried to further explain what I said in hopes to try to prove me wrong. Sorry I was not specific enough for the dry tuning comment, but I was referring to anytime you go WOT with out the spray the car will be running pig rich if you tune it for spray.

Also yes a lot of these intakes are a dry flow type, which is why a 1 jet fogger setup is not optimal and just for small shots or starters. Trust me I'm trying to figure out a way finacially and realty wise to get a direct port system on my car to eliminate any chance of the intake I decide to use to impeede my delivery system.

I only have larger 28# injectors due to the mods to my motor to run it N/A alone. If you get a larger cam you may need the same. I do not rely on the injectors to provide extra fuel for the nitrous though. As far as a pump goes, I have a Walbro 255 HP pump installed right now and that is almost a must when doing this, especially since I run 63PSI at WOT for the trailblaizer injectors, and do not have a secondary pump for the nitrous sytem. I tap off of the fuel rail to provide the fuel for that.

[Rootie524]

can u take a pic or two of ur setup?

[Guest]

As far as what The_Raven said... he took a lot of what I said either out of context OR tried to further explain what I said in hopes to try to prove me wrong. Sorry I was not specific enough for the dry tuning comment, but I was referring to anytime you go WOT with out the spray the car will be running pig rich if you tune it for spray.

No, not out of context...

I don't know why anyone would tune the base fuel delivery (fuel injectors and/or ECM) to compensate for nitrous, that just doesn't make sense, since every nitrous system available has dedicated ways of adding fuel, either through an extra nozzle (or secondary passage in the primary nitrous nozzle) or increasing the fuel pressure.
I was explaining however that if you did tune that way, that only WOT above a certain RPM would possibly run fat, if it was tuned for optimal torque increase.

There is a lot of what you posted that makes me question just how much experiance you really have with nitrous, I've been around cars that use this and tuning nitrous since I was a kid, quite literally. It's not magic in a bottle, ok it is, sorta, LOL, it's just mixing a chemical reaction in a desirable way. I see far too many people saying that one system is better than another simply because they don't want to be considered a "ricer", or because they heard from someone else that one is better than another. Different applications require different parts.

[pocket-rocket]

too rich: you buy spark plugs, too lean: you buy pistons.

Sig'd!

[robertisaar]

Sig'd!

it may have been said numerous time before by countless amount of people, but i first head it and understood it from Bruce Plecan (Grumpy from TGO). RIP