SCV8

I got a 92 Corolla for free, and drive that mostly instead of the SC, to try and keep the miles off the nice car. I tuned it for premium, and don't want to mess with it.
I have the piggyback ecu on the SC4 with the added timing advance, so it will ping a bit in hot weather after sitting in traffic, and the one I have doesn't even have as much advance programmed in as the rest of the Weapon R piggybacks did(early unit), feel bad for the others that have the other ones.

JspecSC3

iTrader: (4)

Geeeezzz 2.70 for 93 Octane??? That is a good deal. Here in San Jose, California we dont even see 93 around here. Instead we are stuck paying 2.96 - 3.03 for 91. But anyway, the Lexus manuals that come in your SC's reccoment that you use premium which im assuming is 91 and up.

2autumn

I use 87 in my SC300, drive really hard and have no problems, no knocks, pinging, or anything.

I used to work on an oil refinery and learned there that most cars can run on lower octane than specified. You might just slightly detect a small decline in performance.

If your car pings, just adjust the timing slightly and use the lower octane. I had an E Type Jaguar when I was at College (30 years ago) and no money, so always drove that on low octane, just adjusted the timing so the car only pinged slightly under hard acceleration. And, boy, I drove that car hard! I almost wrote it off several times over 6 years or so, but I never had the engine give up on me.

So low octane should be fine, and if your car pings too much, well just adjust the timing slightly, so you only hear it under hard acceleration.

CompuMan

Well SORKA. Perhaps my mechanic is an idiot as you say. But I have been doing just as he suggested and my 92 sc400 is running just great. Theory is OK, but practical experience trumps theory every time

sorka

What does your mechanic being incorrect have to do with your engine running fine.

Jimbo2828

gas prices in here
http://gaspricewatch.com/usgas_index.asp

CompuMan

/quote
You're mechanic is an idiot. It's true most cars will retard the timing if you put lower octane gas than required......but only AFTER the ECU has detected detonation which means damage could already be occuring. Yes that's right, the only way the ECU can retard the timing for lower octane is IF IT DETECTS DETONATION. Even worse, detonation cannot be picked up by the sensor under most of the RPM range.

Above was your remark. As far as I am concerned, it is just theory. My mechanic has been working on these cars for 20 years and May just know more that you!

sorka

The factory service manual is very clear about this. I'll trust the engineers that actually designed it rather than the word of gear head who obviously hasn't got a clue.

JCSOTW

what's run-on and how do you fix it once it starts occuring? I'm just not sure what the issue I'm having is called so I need a little help.

Thanks

CompuMan

Since you are obviously not thinking, I will break it down for you. When I buy high test it is 93 octane.
When I buy the next lower grade it is 89 octane. Now any one Should be able to add these together and divide by two to get the average octane. But, perhaps I need to do it for you:
93 + 89 = 182 / 2 = 91 octane. I am sure that the ECU can handle that. In fact it does on a regular basis. I NEVER said that I was using 87 octane!

sorka

Go back and re-read my original response to what your mechanic said. I challenged his assertion that it is safe to run lower octane because the ECU will adjust for it. I said nothing in my original response about what octane you were using.

The SC400 recommends 91, not 93. Running a higher octane than tuned for wont damage your engine, but it won't produce optimal mileage. Of course it all depends on what your base timing is actually set..

I myself run 89 most of the time without pinging.

Around here, the usual spread between grades (87 89 and 91) is 0.10 between. But occasionally, there are stations where the spread between 87 and 89 is very very large while only 0.10 between 89 and 91. In those cases. I mix 91 with 87 to get 89 at a lower price.

arunp1783

hey all,

I hear that about the crazy gas prices - I just paid 50 bucks to fill the 400.

But I was a chemist in past life; no joke & not for a gas/oil company - so will a lot of confidence I can say the you get what you pay for as far as gas goes - from my own experience - chevron and u76 do have some of the better gasolines - like i said I was a chemist in a past life - and my group and I did run experiments to findout exactly what additivies and amounts are in some of the gasolines we by

I've actually bit the bullet a couple of times and run 87 in mine when I absolutely had to, gas milleage is not as good nd the fuel burns faster. If you have to do it once in a while won't kill you, but I woun't make a habit of it

SCV8

Yup, mileage sucks with cheap gas, so not for me, would rather just try and keep my foot out of it.
With stock, lame ignition timing, I can see how you might get away with it though, since several here have obviously been doing just that. Pinging is also caused/made possible from carbon deposits in the motor too, and that will vary from each car.

Who make a decent water injection setup these days?
Haven't seen an interest in that since the seventies, way before all the neat little electronic controllers we have everywhere nowadays, but I know it works well to help the combustion process.

sorka

Water injection is talked about a lot over at www.twinturbo.net. There are a number of good kits in the $500 range that are far more reliable than the ones from just a few years ago.

Water injection is great for raising octane for high boost. Of course it has the side effect of making your combustion chambers bear metal clean.

For non turbo cars, water injection should be a lot cheaper because you're not overcoming postive manifold pressure.

AaronE

LOL. I'm with VS on this one. I run nothing but 87, and I'm not sure I'd know how to drive without WOT. Never a single ping. Just had a little sprint to 140+ last week and it was happy with that too...