What is an optimal compression ratio for N20 motors? Does it matter how much you are spraying?

Say it was going to be a 175 to 200 shot. Also, do nitrous pistons raise or lower the compression?

I have no idea what they should be at or around for an N20 motor. I have just noticed many people in my club have been blowing head gaskets and was under the impression that the compression was too high?

-Sean

 

I can't specifacally tell you what compression to use on that shot. However nitrous unlike boost likes compression, oxygen is released from the nitrous when its heated, more compression=more heat so low compression is not optimal for nitrous. You want to run as much as you can get away with basically.

 

depends on what kind of gas you want to run,is it a street car? race car? anywhere from 11-13.1.

Also Nitrous pistons can raise OR lower the compression,they call them nitrous pistons because the ring pack is loweron the piston to allow more meat/strength at the top of the piston.

 

So an 11/1 ratio is good for a street appliction?

If the compression is not the problem with the headgaskets, then why are they blowing their head gaskets? All who have were using a 150 wet shot with new stock gaskets and head bolts. Would it just be a bad gasket? FWIW they are all LT1s and have changed the gaskets from earlier failures.

I am curious because I am planning to use nitrous on my car, but the increase in head gasket failure in my club has gotten me a little worried. I don't want to change my head gaskets every few months.

-Sean

 

i guess it was bad gaskets.........i have run a 150 shot for over 1.5 years on a 100% stock LT1......havent blown a gasket yet.

 

havent blown a gasket yet....you could..150 shot. if you use it enough something will go wrong if its all stock

 

It really does depend on how much nitrous you are going to use, as well as many other things. There are two basic approaches to a high hp nitrous motor: low CR and huge amounts of nitrous and high CR with a slightly less huge nitrous shot. But neither of these have a lot of relevance to a street application. Here, I think what others have stated is true. The best combo is a relatively high CR with a stout piston and good gas.

On my blown+N2O application, the motor has a low CR. IOW, it's optimized for the blower with the nitrous added for some extra kick. I think the same concept applies to NA+N2O. Optimze it for NA operation, add nitrous "as needed".

Rich Krause

 

how much can you spray with absolute heads????

and what head gaskets.....????? feldpro???

 

im going on the assumption that your building a motor.

n2o motors are not like boosted motors in the matter of compression. with a boosted motor, most people go with a lower CR and add lots of boost. theoretically, you COULD have a huge CR and just add a little bit of boost, but from what ive heard from other peoples experience, thats not an optimal combo.

with a n2o motor, you can run as much compression as you want. however, as somone else stated, how much compression you run really depends on whether or not you want it to be a "street car". if your thinking about 13:1+, then more than likely youll be wanting to run somthing like cam2 or at least a mix of some kind, which will not be practical for the street. i would say if you drive it alot or just want to be able to drive it alot, then try and stick with somthing like 12.5 or prefferably lower.

then, add as much juice as you think your motor can handle!




jon

 

The practical limit is determined by the maximum cylinder pressure the heads can take without lifting. You take whatever compression ratio you want, and keep adding spray until you reach the critical point. I run a 300-shot on a 10.8:1 engine. No reason you couldn't start with a higher CR and just add a little less spray.

The thing I like about using more N2O is the fact that nitrous adds torque at about 1.25-1.50X the HP rate (e.g. a 200HP shot might net you 250 to 300 ft-lb). And all of that torque is available as soon as you hit the button. Obviously you don't want to spray too low, but you get a huge increase in "area under the curve" that way..... .

 

Would the impala head gaskets be ok to use?