1badasZ

is it better to have higher compression or lower compression for nitrous. i have heard both ways but need to know from somebody who knows what they are talking about. thanx in advance

RacinLT1

higher is better IMO. car will run better n/a and nitrous doesnt care. if you are building,go as high as practicle for your combo

MEAN_SBC

According to one of David Vizzards small block chevy books he says that the faster cars have less compression, and more nitrous... The higher the compression you run, the higher the chance you run of melting pistons, and blowing head gaskets... Lower compression engines actually respond better to nitrous as well, this is in the same book. This is why my new combo is lower compression, Gusto nitrous... I had an 8.5:1 $325 dollar short block in my old combo, with cast pistons, and 175 shot.. It ran a best 11.34@119.....

Wild1

Good point... what is your engine going to be used for. If it sees a lot of street driving and limited track... the ultra low compression may not be desirable. If you are only track racing, then drop the compression low.

You shouldn't melt pistons unless you lean out. Head gaskets are always a problem with boost (chemical or supercharged). People throw a lot into their engines with high compression.

David Visard is right about low compression and high N2O. I've got his book. There is more to compression than a Static Compression Ratio. You can have low SCR and high cylinder pressure or DCR.

RacinLT1

i dunno,im happy with my stock 10.5:1 and 175 shot going 11.0's. Vizard has different views then pro builders,so it's more of go with what works better for you.

rskrause

Low to medium nitrous go with high CR. Huge amounts of nitrous will want a lower CR. By huge, I mean 350-400+ hp.

Rich Krause

Wild1

Yep, my target now is to build a 395 with a 150 shot. The DCR is around 8.38:1. SCR is 11.4:1.

RacinLT1

very interesting,thanks guys........gives me something to think about for my solid roller/nitrous buildup.

JWINN

I'm not sure who David Visser is and more then likely he writes books? I'm curious as to how many nitrous motors he has built that have been winning combinations? In the past 5 years that I know of I have never heard of this guy and have not seen any of his engines winning races at the NMCA/NSCA events. Point I'm getting at is don't believe everything you read!

High Compression will typically offer more more with the correct combination thus nitrous creates cylinder psi. This with high compression will offer more power than a low compression N20 combo.

The fastest nitrous cars out will have compression ratio's of 15.1 to 17.1 compression. Let me tell ya first hand that if you ever get the chance to drive a high compression car vs a low compression car your going to get a difference in power of at least 100hp! A high compression motor has a sound all to its own.

I can say this much I had one of the top nitrous tuners setup my nitrous system and flow it and I was told if I went with anything less than 13.1 I would be giving big power up! And that is considering the fact the motor will see a min of 350 shot of nitrous to 600 shot. My motor is well over 13.1+ compression and my engine builder knows what amount of nitrous the engine is in store to see and the compression fact he agrees with. Most people just are not willing to run good race gas all the time.

Personally if your not willing to run race gas I wouldn't even start with a nitrous combo but infact put together a tubo or supercharger combo. You will by far enjoy it more not to mention the power is always there.

rskrause

I have no disagreement with what Jim said, but I think he is talking about fully built race motors designed for race gas. For a street or street/strip combo, if you plan to use large amounts of nitrous at the track you will do better with a moderate CR, IMHO.

David Vizard is/was an engine guru who has done thousands of dyno tests and built many race motors. He has done work as a consultant for a variety of big names. He wrote a great series of books on high performance motors. The books are a bit out of date, but the basic priniciples haven't changed. I wonder if he is still active, as I hadn't heard much of him lately?

Motors for a large amount of nitrous have more to them than just the correct CR though.

Rich Krause