Contour Enthusiasts Group Archives Forums Modifications Forced Induction Nitrous and Compression

How does compression corrolate to use of Nitrous Oxide? Is it in anyway similar to a supercharger or turbo setup?

no, absolutely not.

Um, rethink before you post. Compression plays a VERY important role in ANY forced induction!

High compression is very ill-advised when using a super or turbo charger. You can use high compression with nitrous, because you have to severely retard ignition timing. This is partly because nitrous has the effect of drastically speeding up combustion. The pro-mod engines drop compression from 16:1 to 14.5:1 when going from N/A to spraying, but this is an extreme example. For any street application using nitrous you can run as much compression as N/A, but good fuel and retarded timing is a must. The retarded timing does help guard against detonation, but it is mostly necessary because of the rapid combustion process nitrous causes, and power loss is much less than with a N/A application. This is of course because of the extremely high cylinder pressures encountered in a nitrous engine.

Ok, I thought about it and typed an answer. I stand by what I originally stated, as the question was how does comp ratio correlate with nitrous, is it similar to turbo/super charged applications...not how does compression ratio correlate with forced induction. 2 entirely different things, nitrous and turbo/super charging.

Very well put GSXRTURBO1 , couldnt have said it better myself!! He is right though, and by the detail he said it i think he knows his stuff!!! good job my man!

Maybe the following links will help you understand nitrous a little better:

"Intro" to Nitrous

Nitrous Oxide and Pistons - Technical

Before installing nitrous oxide on my Cougar, I did a ton of research and actually bought a great book ... the title escapes me now ... I will look it up when I get home. Anyway, one thing I learned is that nitrous increases cylinder pressure just as a supercharger or turbo would, but with some special side effects.

Because cylinder pressure is increased, spark timing is critical! Too soon and you could be dealing with failed head gaskets and rings, or even runaway detonation if you nitrous/fuel mix isn't just perfect or slightly rich. Too late and your exhaust temps go through the roof and you end up burning valves and frying exhaust components.

However, when nitrous brakes down into it's nitrogen and oxygen atoms are released, we now have two nitrogen atoms, that tend to stay together (N2), which act as a buffer to detonation. So, if the timing is exactly perfect, higher compression can be run safely.

Due to the exactness that is required though, I would agree with the assessment in the second link ... better off running regular compression and putting all your efforts into getting as much nitrous in the engine and make sure that it is properly mixed with enough fuel.

Good reading, and I think the book you mentioned was referred to in the second link:

The book titled "Nitrous Oxide Injection" by David Vizard, published by S-A Design is stocked in any good speed shop and should be required reading by anyone wanting to run nitrous successfully.

I have this book, it been around for awhile, but the info is all good and really never goes out of date.

Tuning is the reason some people will put a 40 shot on a car and go quicker/faster than someone with the same car and a non-tuned 80 shot.

Good links, I always enjoy reading good technical material.

Actually, it's a completely different book ... did a search on Amazon and found it:

Nitrous Oxide Injection Guide - by Joe Pettitt

I would tend to agree with the reviews of the book in general, but if you notice, these reviewers where looking for a specific application. This book is more about nitrous oxide injection in general and has few specific application references, most of which are carb or muscle cars. The import owner would be disappointed that his VTEC isn't listed with step-by-step instructions for the complete moron who doesn't care about how it works or impacts your engine, they only want NAWWZZZ! However, it is true that many passages are repeated, which can be annoying, but I think that the author was simply trying to drive the points home that were repeated.

I'll look into that one. Yet another good one is "Nitrous Wars" black book, or something like that. I've been told to get it, but haven't yet. Maybe I'll get that and the one you recommend this weekend :p

I would pass up the one I have and check out Joe's other nitrous book for imports ... seems he address my concerns without me knowing about it

Sport Compact Nitrous Injection - by Joe Pettitt