Hello all, long time member, but havent posted in years.

Anyways, just got my 1989 GTUs up and running again (was down since 2008,) had a Mazda reman with 30k and great compression swapped in about a month ago. Ive really been enjoying being back in my RX-7, (been in a Miata for the past few years,) but I am now looking for more power. Mind you, I have NO prior experience with nitrous at all, I have just done my research and plenty of reading.

Please dont muck up this thread with how nitrous sucks, blah, blah, blah... I know, it wouldnt usually be my first choice, but when thinking about low cost performance and an engine that will still pass smog, this is about it for N/A.

First off, Im planning on running a wet 50 shot, with a wot switch and also rpm switch (thinking 3500-7500 engagement.) I want to keep it as safe as possible and protect my engine.

Secondly, I am currently premixing (half oz per gallon) in this engine, hoping to keep it going for a long time, as it consistently sees high revs weekly. My question here is and yes, I searched, am I going to run into a problem running premix through the fogger?

Third, related to the second question (havent been able to find an answer through searching,) should I be running 91 octane (Im in California) all the time or can I just either fill up with 91 prior to nitrous usage OR can I use a octane booster? Again, this is another situation where I have no experience or knowledge, do octane boosters work for this application, do they even work at all? Ive got no clue. (Currently running 87 in this engine even when revving high.)

Last, Id appreciate any helpful tips or comments from anyone with nitrous experience or maybe even someone who has installed nitrous on their own S5 N/A.

Thank you all,
Eddie

 

I'm about in the same positiion as you right now. I have a NOS wet kit, fuel pressure, nitrous pressure gauges, all ready to mate up to my aeromotive A1000 fpr, wideband O2 and walbro 255 fuel pump. All mandatory stuff in my opinion. I am planning on running a larger shot than you though.

The reason I'm not on spray right now is because I haven't found a satisfactory way of retarding timing on the stock computer. Timing boxes are expensive and I have my doubts as to them functioning properly on a FC CAS. You could also run the CAS full potato but then it will idle poorly, get **** fuel economy, and lack power until you change it back. When my engine first sees nitrous, it will be controlled by a megasquirt.

 

Suscribed.

I also have a NX kit waiting

I still haven't figured out the air/fuel ratio when spraying.

 

Over the counter octane boosters are a great way to lower your RON a point or two.

Filling up prior to using nitrous wouldn't make a damn bit of difference to the ecu which would have to be reset... and the fuel system free of the lower octane fuel.

 

I don't know anything about nitrous but I do know it's best to run high octane in an RX7 all the time.

 

That information is incorrect.

 

and where did you get that info from? there is almost no difference in an n/a rotary in using 87 or 91+ octane.

i wouldn't worry about premix with the wet kit, the nozzles are always going to be soaked in fuel. if it were to be left to dry out then it could become a problem such as storing the car for many months with the fuel system open after using premix.

with the nitrous i would just run 91 all the time. if the tank is half full of 87 and then you top it off with 91 then the net result is going to be 89 octane and you don't want to really risk it with any serious power adders.

there's a few articles about octane boosters, some are pure garbage, some work very well at increasing octane ratings. do your research before grabbing just anything.

 

Thank you for the replies all.

So from the posts thus far, Im gathering that if I want to use nitrous 10% of the time, I SHOULD pay the extra for 91 octane 100% of the time?

 

do you put 87 gas in a modified turbo rotary when commuting even though you may not be using the boost?

yes, you could. is it wise? not really.

 

Lol, obviously true, but I am running a stock port, S5 N/A engine.

My concern is just with the 91 octane the rest of the time I am just driving around normally? Ive always used 87 in my N/A, I understand higher octane for a modified turbocharged engine, but from what I understand, it provides no benefit in the N/A engine (to be more specific, Ive always "heard" that using 91 actually decreases performance in the N/A engine?) I have never been able to understand why this is a common saying in the community, mind you, my knowledge is very basic when it comes to engines.

https://www.rx7club.com/2nd-generati...ou-use-822404/

Not to make this into a thread about octane, but since it is an important factor to any nitrous build mine as well get all the facts out.

 

nitrous does not work on the same principle that natural aspiration does, since you are filling the chamber with more oxygen it could be construed more closely to forced induction. it just uses a chemical process to add that oxygen versus a mechanical compressor. what this means is, you can pitch out standard natural aspiration rules.

 

Conclusion; this will be pricey.

Hahha, anyways, in all seriousness, what type of fittings/adapters is everyone using to plumb from the fuel rail (banjo bolt?)

 

...

 

Hi Eddie,
Back in the day I had an Fb with a 4 port (street port) 13b, holley set up with all the bolt-ons etc. I ran a couple different size shots from 75 hp up to 150 and then I added a blower. Anyhow, when I was just running the nitrous the car was "finicky". I had to use race plugs and I learned through experience you wanted to run the car richer than what the kit suggested. It is not cheap and if you have any issues be ready to rebuild the engine. I went through a couple. I had the bottle warmer as well.

I would step on the throttle an engage the nitrous at 4 grand and above, you don't want to be any lower before it comes on. When it comes on it really hits. I ate up gearboxes and rear ends but it was sure fun.

If you are going to run it in your FC make sure you have a good flowing exhaust system, as in header etc., and start off with overly rich jetting and keep it on the richer side.

There are better and cheaper ways to make power. Exhaust is the first way. Oh and no, octane booster from the local car parts store doesn't work, I always mixed race gas.

 

No.

Octane requirements are factor dependent on the size of the nitrous shot, the fuel jetting respective to the nitrous jet, the plugs you run, and engine timing.

 

Engine specs? Any way to monitor egt's?

 

Thank you all for the very helpful replies! Much appreciated!

Anyways, so like I mentioned in my op, I just want to run something REALLY small and as safe as possible, all while keeping it very simple, (no timing change, no big fuel modifications, etc.) I understand pump and regulator, doesnt seem like I can get around that and also, I dont know the condition of my injectors, so I dont want to run a dry set up.

Oh and one other thing, my tps is completely wacking out now, am I going to have to purchase another one? These things are so finicky, even when adjusted numerous times.

 

I have a zex kit ready to install in an S5 also,can this be used with the air pump? or can I remove it? also the zex manual says you can run a 75 shot without messing with the timing,is this true for a rotary?

 

I always run a minimum of 1oz per gallon. I don't get too scientific. The amount it lowers the octane rating of my fuel is almost nothing.

I'm sure when the nitrous is being added, the fuel will also be increased, so you won't need premix shooting through the fogger.

Another way to help with the 91 octane here in CA is running water/meth injection.

I would waste my money and run 91 octane, 1oz per gallon premix all the time, better than buying another engine