Nitrous Injection!

[More Power]

What are the advantages/disadvantages of injecting nitrous oxide before/after the intercooler?

I would imagine injecting nitrous before the intercooler (turbo outlet) would allow for an enhanced cooling effect of the hot boosted air and a more complete mixing. However, most kits inject close to the intake manifold. Why is that?

Jim

[BMDMAX]

Cheap and easy would be my guess. Tapping in to the plumbing post turbo, pre CAC is more difficult.

I have seen excellent results pre CAC. Better mixing and more consistant results.

[xwing]

It is better to inject the nitrous AFTER the intercooler (IC) because it will cool the intake air more.

The reason is the delta T (change/difference of temperature) across the IC after the turbo is HIGHER when it hasn't been PRE-cooled by the NOS. The higher the delta T across the IC (atmospheric temp to compressed air), the MORE heat is removed by the IC at that step.

POST IC, this cooler air is THEN injected with SUPER COLD NOS; because the delta T here is very high, it cools the "somewhat cooled" air even MORE. It is like dual stage turbocharging; the IC cools it step 1; the much colder NOS cools it step 2.

If you inject NOS BEFORE the IC, you have ALREADY cooled it alot and the IC doesn't DO AS MUCH, because the air is ALREADY colder...less delta T means less heat sucked out!

It is the most logical stepwise utilization of cooling effects, in the way that sucks out the MOST heat. I think it is along the lines of countercurrent heat exchange in some supercooling systems, like for refrigeration. Either place of NOS injection will WORK, but if you ask what the BEST way/the way that sucks out the MOST heat is, post-IC NOS is best smile.gif

[BMDMAX]

Originally posted by xwing:
It is better to inject the nitrous AFTER the intercooler (IC) because it will cool the intake air more.

The reason is the delta T (change/difference of temperature) across the IC after the turbo is HIGHER when it hasn't been PRE-cooled by the NOS. The higher the delta T across the IC (atmospheric temp to compressed air), the MORE heat is removed by the IC at that step.

POST IC, this cooler air is THEN injected with SUPER COLD NOS; because the delta T here is very high, it cools the "somewhat cooled" air even MORE. It is like dual stage turbocharging; the IC cools it step 1; the much colder NOS cools it step 2.

If you inject NOS BEFORE the IC, you have ALREADY cooled it alot and the IC doesn't DO AS MUCH, because the air is ALREADY colder...less delta T means less heat sucked out!

It is the most logical stepwise utilization of cooling effects, in the way that sucks out the MOST heat. I think it is along the lines of countercurrent heat exchange in some supercooling systems, like for refrigeration. Either place of NOS injection will WORK, but if you ask what the BEST way/the way that sucks out the MOST heat is, post-IC NOS is best smile.gif How many nitrous passes have you done on your truck? Have you tested pre, post, and a combo of pre and post like I have? Have you considered changing atmospheric conditions, heat loading on the CAC and the power imbalances that the stock intake runners have?

I do agree with you that if you only consider heat removal that post CAC is correct but when you consider all the variables in play there are better methods.

[More Power]

I do know that a #78 nitrous jet will put the fire out on a launch unless you're making good boost and the engine is making lots of heat.. Nearly killed the engine at SLC... trying to beat BMDMAX, by getting on the bottle a teensy bit too soon. :D

I think I'll reinstall the 20# boost switch so it can't inject unless it's making 20 or more PSI boost pressure. smile.gif

Jim

[madmatt]

hey Jim! What ever become of that mess you thought you made in SLC???

[More Power]

No problems since.... Even when running on nitrous at more than 500 hp... :D However, I set a code P0093 yesterday while performing a mild run (14 sec run) with the new GTech Pro performance meter (collect data for an upcoming story for the web site). Either the fuel level was a little low (sucked a bubble of air) or the fuel filter needs changed.

Jim

[madmatt]

nO PROBLEMS....NICE!

[Trippin]

Originally posted by More Power:
I do know that a #78 nitrous jet will put the fire out on a launch unless you're making good boost and the engine is making lots of heat.. Nearly killed the engine at SLC... trying to beat BMDMAX, by getting on the bottle a teensy bit too soon. :D

I think I'll reinstall the 20# boost switch so it can't inject unless it's making 20 or more PSI boost pressure. smile.gif

Jim I leave the line at 20# of boost. :D

[More Power]

I can't do that with Lil Red... A few psi - kinda depends on braking ability and amount of front wheelspin after the brakes are released. Gotta get the 60' times down... ;)

Jim