Running 87oct in my Turbo'd GSX

Onefast99gsx · 03-21-2005

Looks like this summer i'll probably crank the boost way down and just run 87 octane. It has a 50trim turbo. What do you think is a safe level of boost to run with that octane? Less than 12, less than 10psi, none?? Then before a race day, i'd run her dry and put 92 octane in it.

92 Octane is just under $2.40/gallon here in central Wisconsin. Supposed to go up another 12 cents before the end of March and then on the rise for the Memorial Day in May. I guess i'm expecting gas to be around $2.60 to $2.75 late May and even more if the cost of crude doesn't come down well below the $56 per barrel that it's at right now. We might even see $3.00/gallon if there is a major supply disruption according to many sources.

**JET** · 03-21-2005

Well, the thing is that the price is the US is being artificially raised. Investors are buying up the reserves and causing the price to rise. Once it gets to a certain point they are going to start dumping it and the price will drop. If they don't do something about it soon I would expect the government to step in.

Anyway, if you have a FMIC, then 12 psi should be ok with a 50 trim.

Onefast99gsx · 03-21-2005

Thanks JET. I watch the price of oil probably more than anyone i know. Being in the banking business, it makes me a smart consumer. At the bank we are seeing more NSF(Insufficient Funds) more than usual so it is already hurting us the consumer. This really pisses me off. Back in October of last year oil hit a record high of $55/ barrel. Then it went down to low $40's and gas settled to $1.77/87 oct. where i'm at, in which i can deal with that price and maybe even a dime more. Now after Xmas it shoots up again to a new record high last week. Raising the price doesn't necessarily make us use less so somebody is lining their prockets awfully good right now. They better step in and do something soon. I hear nothing of decreases in the near future. As a matter of fact i just watched CNN at noon and Algeria is talking about a possilbe oil worker strike because of unfair labor conditions or something. Even if you drive a short distance to work, this still affects you more than you think.

JiN · 03-21-2005

what about on a FPT28? Whats a safe level of boost. I dont have a FMIC. I probably will keep getting 97octane, just to be safe. But i'm curious.

**1ViciousGSX** · 03-21-2005

What about just chunking up the extra 10-20 cents for the good stuff, especially if you know you're going to pound on it, and you know you will.

The thing with low octane in a performance engine is this, if the ecu picks up excessive amounts on knock/clatter, even under light throttle, it will start retarding the timing through the "octane" tables. This will reduce the engine's ouput level and will cause your fuel economy to drop. So you could save a dime per gallon, reduce your engine's power and then use more gas to drive the car around. Where's the savings?

p.s. Shouldn't this be in a tech section?

ACRucrazy · 03-21-2005

agreed.
IMO if u have a modded FI car, run premium.. or drive a honduh.

A//// Guy · 03-21-2005

Yea I agree. Either get a geo metro and get sweet gas mileage or just pay the extra 5 bucks for a fillup each time. I wouldnt recommend using 87 for even a stock car, it will not like you for it.

Onefast99gsx · 03-21-2005

I actually looked at a GEO over the weekend but it was a manual tranny and every panel including the hood had a dent of some sort on it. It was a pile of shit. I wanted it to replace my Grand AM daily driver. Since i posted this earlier today, 87octane went to $2.23 just a bit ago. Fucking A. I predict you're gonna see some sort of acts of national terrorism inside our country by our own people if this continues. You watch. And i don't mean just gas skipping acts either.

**JET** · 03-21-2005

I love the little 92 sentra I have. It is a great work car. 33 - 35 mpg and it was cheap as hell. Here is a link to a story about oil prices. It looks like they might be going down soon as production is going to increase.

http://news.yahoo.com/news?tmpl=stor..._ge/oil_prices

AJ · 03-21-2005

Yeah, I can't wait to try and sell the 1.8 (soon) as it will probably move fast for those looking for a reliavle car that gets good gas milage.

JustROLLIN · 03-21-2005

Heres the thing... On ANY car with a knock sensor you can make up the cost difference when running premium gas. The ECU will advance timing until it sees knock, regardless of throttle position, except for WOT. As the ECU sees knock, it will pull the timing back and do it all over again. The ECU is designed to drive the car on the very edge of knocking for high efficiency. So, when running the 87 you are losing the MPG and in turn using nearly as much money, if not more. Not too mention, you can use the thousands of dollars of high performance goodies you bought for the car. So, logic dictates once again. Using 92 will not only allow you to push the pedal through the floor, but also net a better economic position when you arent into it.

**Shane@DBPerformance** · 03-22-2005

Quote:

Originally Posted by JustROLLIN

Heres the thing... On ANY car with a knock sensor you can make up the cost difference when running premium gas. The ECU will advance timing until it sees knock, regardless of throttle position, except for WOT. As the ECU sees knock, it will pull the timing back and do it all over again. The ECU is designed to drive the car on the very edge of knocking for high efficiency. So, when running the 87 you are losing the MPG and in turn using nearly as much money, if not more. Not too mention, you can use the thousands of dollars of high performance goodies you bought for the car. So, logic dictates once again. Using 92 will not only allow you to push the pedal through the floor, but also net a better economic position when you arent into it.

That is not true. Most knock sensor equipped cars do not tune themselves based off of knock. DSMs run off of hardcoded timing tables, it will retard timing when it sees knock, but it will not run more timing than what is in the tables on its own.

JustROLLIN · 03-22-2005

Quote:

Originally Posted by ecoli

That is not true. Most knock sensor equipped cars do not tune themselves based off of knock. DSMs run off of hardcoded timing tables, it will retard timing when it sees knock, but it will not run more timing than what is in the tables on its own.

When you say "most" remember the fact that DSMs are not "most" cars. I was unaware that DSMs will not push that ragged edge, but I can assure you that "most" cars do in fact run like this. Granted DSMs are a different breed seeing as they are turbo-charged. But, cars equipped with knock sensors do in fact push the limit in the name of gas mileage.

MATCHBX · 03-22-2005

Yeah, the 30-something mpg on 87 is awesome!!!! I'm almost having second thoughts about putting the talon back together. It's amazing how much that CRX keeps saving me. Even with 220,000+ miles on it.

I am very tempted to get a bike this year as well. I only have a 10 minute drive to work on backstreets.

95tsi · 03-23-2005

Who cares if prices jump up 20 cents... on a DSM it will cost you an extra $2.00 to fill the tank watch out. Are you gonna stop driving if they get super high?? Probably not. Just think of all the people driving over seas and what they pay, we got it good.

**Shane@DBPerformance** · 03-23-2005

Quote:

Originally Posted by JustROLLIN

When you say "most" remember the fact that DSMs are not "most" cars. I was unaware that DSMs will not push that ragged edge, but I can assure you that "most" cars do in fact run like this. Granted DSMs are a different breed seeing as they are turbo-charged. But, cars equipped with knock sensors do in fact push the limit in the name of gas mileage.

Some newer cars and motorcycles may do this. But the 1990-2000 Hondas, Supras, 240sx, 300zx, etc with knock sensors only use it to retard timing from their base timing maps.

**Kracka** · 03-21-2005

Shit kids, even my VTEC is getting premium no matter the cost. I bought a performance car for a reason, might as well enjoy it. If I have to pay an extra 15 cents per 25 miles I drive then so be it. Jesus, people complain about having to pay $2.50 to drive 25 miles, but $4 for a 10oz coffee is no big deal. In reality, filling up with premium over regular is about an additional $2 per tank...skip the candy bar and pop and you're kosher.

JustROLLIN · 03-21-2005

Well said Chris. When I had my Talon I went through the same thought process as you apparently. Honestly, what is 2 bucks per fill compared to the happiness of boosting when you want to.

IndiEP · 03-22-2005

Even if you were to unhook your wastegate flapper and run 87, w/such low compression and what Justrollin said about the ECU, that thing is gonna be a dog around town.

Emcee gsxtc · 03-22-2005

Well here's the solution to my gas mileage.