hirogx

hi i have a 88 Turbo II with the following major mods:

HKS F-CON w/ FCD
HKS Exhaust
HKS SSQ BOV
HKS Power Flow Intake

and i have been using 91 octane. since gas prices have sky rocketed, and am short of cash, would it be advisable to go with the cheaper gas and use 87 octane? i am the second owner of the car and i believe the previous owner has been using 91+ octane ever since...is it safe? i need explaination to why it is or isn't adviable to convert to 87 octane. you're help is appritiated. thx!! - vince

fusion-turbo

The OCTANE rating, put simply, is the amount of pressure the fuel can take before it spontaniously combusts.

Not only is 87 octane less efficient and less powerful (slightly) than 91 octane, it cant take as much pressure before BOOM.... the gas spontaniously combusts before the spark and= detonation or pre-ignition. Niether are very pleasant and can kill a motor quickly

I shouldnt see a problem as long as your not a lead foot and arent running advanced timing. Be forewarned though, detonation lurks even closer with .....*gasp* 87.....

koukifc3s

iTrader: (3)

i wouldnt run 87 on a TII

jon0886

iTrader: (1)

Great.... I'm a poor... er.... just graduated high school student. I only had $20 in my wallet and I filled up on 87 in my TII....

O well.... I'm still practicing stick a bit with my dad in the car - I dont think I'll be boosting too much. 3/4 tank of 87 in there.... I'm sure it'll go by quickly =P

SonicRaT

iTrader: (6)

Port your wastegate and don't run with a boost controller of any sort, this will keep your boost down around 5.5-6psi, around stock levels. This way you can run the cheaper gas until you get some more money then you can buy a boost controller and turn it up again with some better gas. If it makes you feel any better i run 12psi on a high compression motor on 87 (Though I REALLY suggest you do NOT try to do that!)

1SxyRXy

i dont care how little money i have, i always put the highest octane in my car

bingoboy

OverDriven

Look at it this way...run 87 in your TII and you WILL blow the engine. Thats alot more expensive than gas. You have a full exhaust and intake, and FCD and haven't even upgraded your fuel yet. I bet you are boost creeping to levels that are dangerous even with high octane gas. You need to port your wastegate at the very least, and don't romp on the gas if you're going to run 87.

-Joe

fong

iTrader: (77)

87 is ok for n/a, though. go get a n/a model. save gas money, more reliable

beefhole

iTrader: (29)

Keep the revs low and you may be ok. Stay away from the boost and the hot days.

Molotovman

iTrader: (49)

87, and then OCTANE BOOSTER.
get 87, 15.5 gallons, then put two bottle of octane booster in. It'll up octane 4 times depedning on how concetrated it is. just get two bottle that up octane two points per bottle. then you'll get 91. Its the cheap way

OverDriven

Sigh...ocatane booster will boost it to about 87.5. It doesn't work as well as they say it does.

-Joe

Colbert

Yeah so for n/a engines it is ok to use 87 eh? i was always under the impression that lower octane would be better for an rx-7, considering it was released in the 80's and probably designed to run on lower octane gas right? (Just taking a stab in the dark here)

JKM

On an N/A engine you are correct. Lower octane is better.

On a Turbo engine, the higher is better for reasons described abofe.

torean

for the price of those octane boosters...u might as well just pay the extra 10 cents per gallon for the 91....*remember to look under the seats and around the carpet....ppl tend to drop money in my car..

1987RX7guy

iTrader: (3)

read what "points" mean. They are like fractions of what you would think is an octane point(e.g. one point being 87->88)

casio

octane is a measure to the resistance to heat, i believe.
87 is not less powerful. if anything, its more powerful. the higher the heat, the more power (to a certain point).
i wouldn't be a "lead foot" if i were running 87 in a turbo, especially in the summer. i would keep the boost down (like what SonicRaT said) and not put a lot of load on the motor. drive very conservatively.

what does gas cost there, anyways? latest prices i've seen that seem to be common are:
87 $1.79
91 $1.89
93 $1.99
i think those are right. so every 10 gallons you lose an extra dollar. i'd rather run the right octane and lose a few dollars at the pump every couple of days than be weary of what octane i'm using.

SonicRaT

iTrader: (6)

****, gas is still $2.09 here (for 87)

casio

wow, i think our 93 got that high, but 87 dropped a few cents (maybe 10 actually) down to $1.79 a few days ago. minimum wage here is still i believe $5.15. i dont think its much higher there, though, so i guess that's irrelevant. damn i want an Insight. or to move to germany where gas is more expensive, but walking and bikes are more popular. everywhere, not just big cities.

fusion-turbo

With an increase in pressure, you also get an increase in heat.

Pretty much we are trying to say this: keep your rpm's down. The higher rpm you go, the faster that gas pressurizes and the more it heats up= closer to spontaniously combusting

BDoty311

Don't run 87 in a TII. You could easily blow your motor. If you can't afford 91, get another car.

I believe S4 n/as were actually designed to run on lower than 87 octane, but I am not 100% sure.

hirogx

thank you all so much..i think i shall sell the FC Turbo II after all...any takers? located in the Bay Area, CA.

Digi7ech

iTrader: (1)

Well You can also look at it this way.

NA motors ar higher compression than TII's.

So in theory you can try to boost a psi or two to reach the same compression ratio and still use 87.

So if you stay out of boost then you can run 87 all day because your lower compression than NA.

Scott 89t2

saving $5 in gas isn't worth paying $2000-3000 for a new engine.

and an octane point is 0.1 octane.... so you'ld have 87.4 not 91 with 4 points... plus 2 bottles is probably more money then just using 91....

jon88se

How about adjusting your driving? No boost, no revs above 3K and see what you mileage goes to. Make sure the tire pressure is right too...

This way you make your $ go further instead of cheaping out on the high octane the car needs.