Tiger Rag

I'm the same way, maybe someone who knows can help a brother out. My only guess is that there is more time for nitrous and the charged air to become a more homogeneous mixture if introduced prior to the intercooler. If you're spraying in the air horn could it be that it doesn't get thoroughly mixed, maybe only getting to certain cylinders where that stream flows directly? I know, I confuse myself sometimes. Hopefully someone will set us straight on this.

HOHN

I think you're on to something. Keep in mind that the nitrous being injected is a liquid, and it has to "boil off" as it's injected to fully evaporate. As it does, it's absorbing heat from the airflow. It's like when you rubbing alcohol on your hands, it evaporates and cools your hand. But the maximum quantity of heat removed is when you let the alcohol evaporate completely.

It's possible that injecting the nitrous Pre-CAC has nothing to do with the heat rejection of the intercooler and everything to do with the TIME it takes for the nitrous to evaporate.

I mean, you can't really argue that the SAME amount of nitrous injected into 300º air will cool that to a lower temperature than if it was injected into 200º air. But that assumes that the nitrous completely evaporates in both cases. What if the nitrous doesn't evaporate?

Well, I assumed that the nitrous would completely evaporate, because in gassers, you see direct port injection systems, and even in that short amount of time, the nitrous still evaporates enough to not cause problems.

But a turbodiesel is different in two key ways with respect to nitrous. First, you are mostly trying to inject nitrous into a pressurized environment. Suffice it to say, the physics tells us that the evaporation of any liquid is different at different pressures. So the nitrous that has no problem evaporating in a 14.7PSIA environment will need more time to evaporate in an environment of of 60+PSIA. Just as water evaporates much faster in the reduced atmospheric pressure of high altitude than it does at sea level.

The other diesel-unique feature is the fact that we're attempting to initiate combustion using heat. So if we over-cool the intake charge, it will hinder the initiation of combustion. In a gasser, you don't need the heat to initate combustion because the spark does that. It's not practically different than how a diesel struggles to start in cold weather under conditions where a gasser will fire right up.

So I was right-- in the sense that injecting the nitrous POST-CAC will cool the intake charge more than pre-CAC, but only if the nitrous evaporates completely.

But I was dead wrong to assume that 1) the nitrous WAS completely evaporating, and 2) that we really want maximum cooling. It *IS* possible to cool the intake charge too much.

An interesting anecdote here is how In noticed much truck had a LOT of power when I was running on the hwy in ambient temps of 18º. I had just blocked the wastegate and was fooling around. The stock HX35 can make a surprising amount of boost in 18 degree temps, not only because the incoming air is so incredibly dense, but because once it DOES finally get off the map, the intercooler can dump a LOT of heat at hwy speeds in 18 degree temps!!

And that, my friends, is today's epiphany. Man, I learn something new every day!

Justin

Mike D

This has been a great thread. Thanks to everyone for their input. If I get around to putting a nozzle pre-CAC, I'll report back.

So far, I'm loving my little $300 system, dropping 6 tenths in the 1/4 puts a smile on my face.

Mike D

Actually, he broke the output with a second gear launch, it's still a bad deal no matter which gear it was...

I give Matt credit, he's out there running his truck. Not on the web internet racing.

John_P and myself have broken numerous output shafts (stock and billet) on our trucks along with other parts in the transmission. Unfortunately for Matt, I don't believe there's a billet output for the 5600.

If you don't break you're not trying, right.

Edit: Just to clarify. The comment about internet racers wasn't directed towards you John. We all know you run your truck all over the country.

John_P

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Glad to see you "edited" that Mike D.! As I read it, I thought maybe I was going to have to call you and "discuss" some things with you!

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John_P

joefarmer

and just to rub it in... the bigger system I run drops 2.3 seconds off my 1/4mi.

Mike D

You run a 13.7 on fuel only!

Man! I guess you do need that big o' nitrous kit!

97CTD

Wow...I have learned a lot about nitrous in this discussion...I am almost excited about toying with it some once I start modding my truck...At $300+/- I actually am excited about it....Hehehe....if someone would like to give me some more details on the components of this 300 dollar kit as far as a source for parts and what have you it would be greatly appreciated...

oil_burner

I have a .108 nozzle pre-cac. It's done wonders cooling my intake during pulls. I've playing around with more for the cooling effect than a shot of power . Now i hoover around 1300-1400 when before I'd peg my guage within 150' mark. but sitting here reading this thread maybe try to move the nozzle post-cac and see the difference.

chris

Ph4tty

How did you manage that Matt? Jeez I haven't broken anything yet launching in 4th Where's the carnage pics?

Mike D

I'll answer for Matt. He has a new tranny on the way along with a new upgrade clutch from SB.

From my understanding it's not totally uncommon to break the output on the NV5600.

1-5-3-6-2-4

bump for a great thread..........


any new developments for anyone?



I'm now in the market for a good dose of juice, so I'm researching.........

HOHN

All I can say is that I've come to the conclusion that properly tuning a nitrous system requires air temp readings at key points.

I think the reason the pre-CAC installs are making so much power is because they 1) let the nitrous evaporate completely and 2) prevent excessive cooling by using the CAC to actually WARM UP the air.

Think about it. If I have 400º air coming out of my turbo, it will do a great job of evaporating all that nitrous when I have a big hit setup. The nitrous will also cool the charge down a LOT-- quite possibly below even ambient temperatures.

So when I uncork that massive shot of nitrous, and its drops the air charge down to 40º or so, the CAC will actually transfer heat from the ambient air to the charge, warming it up closer to ambient outside temps.

So when you inject that big hit of spray pre-CAC, you end up with a more homogenous mixture that is closer to the optimal intake temp the engine wants.

When you go post-CAC, there's a good chance you will not have a homogenous mixture of nitrous and air, and also a very good chance that you will be OVER-cooling the intake charge to where it inhibits combustion.

But for a small shot of nitrous, these problems tend to go away.

So in the end, I'd say this-- there is a certain unknown shot size that delineates where it would be better to inject your nitrous. Smaller than that point, and AFTER the CAC is better. Bigger than that point, and BEFORE is better.

So the "ideal" nitrous system IMO would involve two stages and two nozzles. You'd have a small system with a pretty small pill injecting as far from the intake as possible, but still after the CAC (say, near the elblow exiting the CAC). Then your second stage would come online BEFORE the CAC with a much larger shot.

A good location for the pre-cac nozzle would actually be as close to the turbo's compressor discharge as possible. If you rapidly cool the hot air just as it exits the turbocharger, the effect is almost like you are "sucking" the air out of the turbo.

This would reduce the required drive energy of that turbine and should drop drive pressure when the full spray is on (which you want, because drive pressure will be an issue with all that extra combustion product on the spray).

At least that's my untested theorization.