MaxDuo

Ok, I have a T2 that just got rebuilt. And I was wondering.... Since it'll be around 1,000 miles for a good break in and all... I'll be going a long time without boost, and since lower octanes is good for n/a rotaries... It'd be fine for me to run 87 octane during the break-in period wouldn't it? Since it wouldn't be getting any boost or serious driving...

Just wondering. Because I'll definitely not give her any boost until she's broke in well, hahah. And with a new clutch as well.....

eriksseven

iTrader: (6)

good question...

RotaryResurrection

iTrader: (8)

yup.Hell, if you look in the owners manual, stock t2's were set up to run 87 from the factory. ONly when modded is it necessary to run higher.

MaxDuo

Hrmm.... But higher to be safer. Not to mention I will be modding it and stuff later, hehe.

RotaryEvolution

iTrader: (30)

is there a rule you can't boost while breaking in the motor?

i see alot of people babying their motors, which isn't a bad thing but i'm just curious because i was boosting mine within a mile of the rebuild but it had been run for about 45 minutes prior.

i'm not saying there is a right or wrong way and i'm not trying to hijack this thread but i am curious how many people say one way or the other, i'm sure it probably isn't great on the seals until they have fully worn in but i was never all that easy on piston rebuilds either and i have never had a problem with a rebuild grenading due to improper break in, because technically there is no proper way to break in a motor, it is all just personal preference so far as i have seen but i'm still curious as to who feels one way or another on the subject.


and to note, on a thread a short while ago i believe we found the owner's manual said not to use below 92 octane in a T2 and recommended 87 in the N/As.

i don't use less than 91 because that's all we can get aside from race fuel, i also add 100:1 premix to my gas, which consequently lowers the octane again but the added lubrication helps cool the housing and rotor and help prevent detonating anyhow.

ddub

Wrong! This is straight out of the official 1988 Mazda RX-7 Owner's Manual for Turbo and Non-Turbo cars. Notice it says this for both and doesn't say anything about turbo requiring higher.

RotaryEvolution

iTrader: (30)

look it up in the S5 manual, it claims 92 before you go telling me i'm wrong.

but it was partially my fault for not posting the discrepencies between the S4 and S5 manuals and rotors...

also to note, it is better to run 91 or 92 or higher in a T2 because it will fight detonation which is a good thing in a forced air injection motor.

ddub

Yes of course higher is better to fight off detonation, but does it absolutely NEED it? Doubt it. Definitely not s4's, s5's might be more tricky since they have higher compression, but I still don't think it'd be that bad.

Besides the poster has an s4, so he can use 87

RotaryEvolution

iTrader: (30)

i didn't see him post the year/series so i wasn't sure, better safe than sorry, especially during the break in but i like to play rough with my young-uns!

RotaryResurrection

iTrader: (8)

From an engineering standpoint, there are 2 reasons to break in a rotary easily, as compared to a piston engine.

1) most rotary rebuilds are used housings these days, so there is bound to be a little wear somewhere on them, grooves and such. Because of this, you dont have great compression to begin with, in fact there is a gap between the seal and housing in certain areas. As rpms and combustion chamber pressure go up, apex seals are driven harder into the housing by centrifugal force. I choose not to drive mine into grooved housings too hard, but rather let them wear in on their own terms.

2) piston engine rebuilds have a crosshatch on the bores to *cause* the rings to wear in a pattern and seal, this is why you're supposed to run the engine hard for the first couple of hours, to seat the rings against the crosshatch before it wears off. Rotary housings have no such crosshatch, nor should they. They're a fine chrome surface which cannot readily be machined or repaired. So why would you take a rotary out and try to break it in hard?

I'd like to see an 89 manual. BUt, even so, running 87 in an s5 (or even FD) for a road trip or easy breakin is perfectly acceptable. I ran my FD (12psi nonsequentials, stock ecu, full exhaust) all the way to atlanta and back. Ive been doing this for years. You only need protection against detonation, under conditions that detonation could occur. Light/mid throttle, low or no boost, and cruise are not such conditions.

True, but during a road trip or breakin, you're not really using any boost, so it's just a waste, IMO.

ddub

Sure I guess, but if you're not putting any boost into it then why run higher octane? It's pointless really. I mean for the first 1000-1500 miles or something like that on a turbo engine break-in you arent supposed to give it any boost.

RotaryEvolution

iTrader: (30)

but a few extra bucks aint a bad idea for a $1000+ investment is what i'm trying to say. not that you always have to run higher octane fuel, that is a whole nother discussion. when driving hard it is good to use higher octane fuel in just about any type of combustion engine, on road trips under light loads and mild acceleration i also use lower octane fuel.


it makes sense to not break in a rotary hard now i guess but it probably still is personal preference, i have seen ALOT of mechanics give me wierd looks when i go peeling out of the lot in a brand new rebuild on a piston engine but then i see them doing the same in a PDI right off the car carrier, it is the same IMO, rather my rebuilds have assembly lubes to also help protect them whereas the manufactured engines just use a mild engine oil..

breaking in a rotary could be viewed like breaking in a set of brakes then, if you break them in too fast they will not seat properly. (kind of a wierd analogy i know, because brakes do not eject pads...)

ddub

Excuse me? "when driving hard it is good to use higher octane fuel in just about any type of combustion engine" You including the n/a's in that? Because it is in fact way worse to use higher octane in an n/a under any driving conditions, hard or not.

RotaryEvolution

iTrader: (30)

there is always exceptions, i did not say ALL.

BklynRX7

This forum shows me the true intellgence of ricers. i am the only rotary owner in my group of honda owning friends and i have learned never to listen to them again. I just developed an interest in cars over a year ago when i got my first car, my fc, and these people were my main source of car knowledge. they lead me to believe that the higher octane fuel has a higher rate of cumbustion and therfor more power. they go and spend 20+ dollars on octane booster every saturday night for their n/a hondas thinking they were helping themselves, meanwhile their losing what little power they have left. THANK YOU RX7CLUB

13bpower

The reason 87 octane is *recommended* for rotarys is its lower resistance to burn. This is better in rotarys for the reason that the combustion chamber is really long and a higher octane rating would make complete combustion more difficult. This is also the reason we have 2 spark plugs to each rotor.

That being said a higher octane just *might* make more HP on a NA piston motor. In the correct application that is.

MaxDuo

I didn't think there'd be anything wrong with using 87, just wanted to check and see what others said first

Hrm... I got into cars about a year ago myself, but I thought Hondas did have rather high compression... So I'd think higher octane would be helpful for some? I remember someone saying turbo'ing S2000's was tricky because they already had tons of compresion......


Anyway, back onto topic... I figure most would get it... But when 13brotor said the combustion chamber was real long... That was also to sort of mention that there wasn't as much compression going on there... And that a larger area needs to experience combustion... Lower octanes burn faster.. So they're better in the n/a's because it's harder for them to detonate from the lower compression (ugh, typed "combustion about 5 times, deleting right after each time, then wrote again.... too tired) and they need to burn faster to be fully used and give more... I dunno... oomph.

Ok, I don't know how that last paragraph came out... Probably look like an ***/idiot or something, but I'm suddenly exhausted haha, bedtime now.