Nitrous: Direct Port vs Single Nozzle on a boosted vehicle

[420]

I was talking about this subject with some friends, and figured I would get the Turbo Buick community's opinion, as I know there are several great minds on here

The question was which would work better on a boosted application: Single Fogger Nozzle in the intake piping, or a Direct port setup? Let's assume the following:

- Vehicle is on good gas (C16)
- Using Methanol Injection
- Making a fair amount of power (800+ hp)
- Advanced EFI (XFI, BS3, Accel Gen7+, etc.)
- Individual Cylinder EGT monitoring

The reason for the question was that by using a single nozzle in the intake pipe, you are reducing intake temps significantly in addition to adding oxygen to the combustion cycle. I was concerned that by using a direct port system, you would lose the benifit of cooling the intake charge. Yes, I know the Methanol does that as well, but the cooling effect of the nitrous must be ten fold (at least) that of the methanol. The trade off of the direct port route being the tunability of individual cylinders.

So, Pro's & Con's:

Single Nozzle:

Pro: Greater reduction in intake temps
Con: Decreased tunability


Direct Port:

Pro: Individual Cylinder tunability
Con: Decreased / No reduction in intake temps

So...

- Am I missing any variables?
- Which is better on a serious boosted application?

Let's talk

- Matt

 

[Grumpy]

ran NOS back in 86.... single nozzle worked great ..then NOS came out with the "6 pack" a plenum with 6 nozzles mounted in it ... looked great !!!! single nozzle WORKED better... sucked at the time to pay $500 for the 6 pack and took it off within a week and went back to the single nozzle in the plenum tube

 

[420]

ran NOS back in 86.... single nozzle worked great ..then NOS came out with the "6 pack" a plenum with 6 nozzles mounted in it ... looked great !!!! single nozzle WORKED better... sucked at the time to pay $500 for the 6 pack and took it off within a week and went back to the single nozzle in the plenum tube

Ok, talk to me What worked better about the single nozzle?

 

[TurboTR]

Well I think you'll get the air temp reduction either way, so would take that out of the a/b decision process. You just won't be able to readily measure it with the port setup, and the control system won't see it either. But you'll have coverage for that lack of air temp drop sensing built in to your fueling amount basically, so it will be covered anyway. It'll just be a "hardwired" coverage in that case, but will be fine in practice.

If you plan to run C16 I'm wondering why the methanol injection as well? Is any extra benefit worth the added complexity here? Or maybe it's already on the car I guess for lower power pump gas coverage or something. IMO the air temp issue is covered by the nitrous alone- it will substantially cool the air charge. If it doesn't cool it quite as much as the added methanol injection would on top of it all, well just put in a bigger nitrous jet to bring in more O2 to make up for the slightly reduced air density w/o the methanol injection. Problem easily solved- I like that

So that would leave anti-detonate properties. Probably not necessary at the ~800 hp level with 100% C16, but also not a bad thing for some extra insurance. If you can successfully manage the added complexity of the 2 systems (ie control, a/f ratio, reliability, etc).

If you have an advanced control system then you can of course adjust individual cylnders a/f ratio by tweaking the fuel. So I'd probably take that out of the a/b decision process too. Unless you want to try and use spray to make up for some bad air distribution properties of your manifild setup.

The lone nozzle in the intake pipe is very attractive IMO because of its relative simplicity and much lower cost. The individual nozzle system has alot more bling. I think it really boils down to that choice basically.

Anyway just how I see it. YMMV.

TurboTR

 

[420]

Any other throughts on this?

 

[Grumpy]

well I was told back in 86/87 from some guy in Cali named Ken something that the flow was better with the single nozzle .. I used both and went back to the single nozzle

 

[Alky V6]

My thoughts on this are, depending on the HP rating of the system, either system could work well.

I would tend to use the single nozzle system for low HP shots and step up to a direct port system on larger shot systems.

I would always worry about distribution with a single nozzle setup, especially a wet system. With a low HP system, the distribution problem would be exceptable. As the HP rating increases with a single nozzle system, the distribution problem becomes much more acute. I'm not sure what the HP rating should be before considering moving to a port injection system, I just know that if you don't want to worry about distribution problems, go port or go with a darn good single nozzle system to keep distribution problems to an absolute minimum. There are enough variables to worry about.

Here's a thought. If you go port, mount the nozzle at the entrance of each port, aiming square down the middle of the port. That way, the jet stream of the nitrous can actually help increase overall port flow. Like you need that with nitrous anyway. That will require mounting some plumbing of the system inside the plenum. Might be worth it with a large system, or even a small one.

 

[J-B Racing]

When Don speaks about NOS....it`s worth it..

 

[Grumpy]

mine was just a stock gn in 86 ..

 

[aze12677]

with nos do i need to run methanol at higher boost or can i just use the nos

 

[Boost231]

has anyone run a temp sensor in the intake to see what the temp drop is from running NOS.

 

[Alky V6]

I sense there is a growing interest in nitrous. Learn all you can about the stuff and don't just jump into it. I've read all the books I could get my hands on about nitrous and I've only dented the subject.

If you're planning to use it with pump gas and keep it on for the whole pass, please start out with a small shot. 50 or less. Check your data and work slowly.

Remember. Methanol is a fuel and nitrous is an oxidizer. Sure, they both cool, but it's what they do after that. Don't think they are similar. If you're going to use pump gas and plan on stepping up the shot after getting your feet wet with nitrous, I would keep that methanol injection system handy.

 

[Alky V6]

Start out with low boost settings to make sure you don't end up overspooling when the nitrous hits. I tried keeping my 200 shot on for the whole run only once. I should have had more alcohol to feed the monster, the wastegate was too small, turbine housing too small, boost went crazy, timing retard should have been more and the ground electrodes melted into a stubby ball. I'm going to be very careful if I try that again. I will definitely make sure there is plenty of fuel.

This was with alcohol and nitrous. A very cold combination, but it still melted the ground electrodes soon after the shift to second.

Nitrous will make burn time speed up and add a bunch of heat to the process. Don't skimp on the fuel. A buddy of mine runs his naturally aspirated application just into black smoke rich. That's after burning several pistons up.

 

[TurboTR]

The cooling effect is substantial. I saw about 45 deg IAT downstream of the hose if I recall.

If I had melted or otherwise hurt plugs I'd be pretty darn upset. Major engine damage is not far behind. Something is/was drastically wrong in your approach, at least for a moment to see that damage (as you no doubt know).

TurboTR

 

[Boost231]

just trying to figure how to drop inlet temps.

 

[bobc455]

If you are looking to drop air inlet temperature and not necessarily looking to spool faster, have you thought about spraying your intercooler with nitrous or CO2?

-Bob C.

 

[Pronto]

I don't know how well it works but it's not allowed at NED...

 

[bobc455]

Interesting, I've never heard that before. I'll have to re-read the rulebook. I can't imagine why it wouldn't be allowed.

-BC

 

[Razor]

Depends on how much nitrous. I mean for a 75 shot.. I wouldnt sweat the direct port deal.

For a 250 shot.. then we're talking

 

[420]

Depends on how much nitrous. I mean for a 75 shot.. I wouldnt sweat the direct port deal.

For a 250 shot.. then we're talking

Well the concern was unbalancing the distribution on an 800-1000 hp application. Sure, the nitrous is only a 75 shot, but if it causes one or two cylinders to run lean... ouch