91 octane now vs 91 octane then

[iwantatta]

Just curious what makes todays gas worse for higher performance cars than gas in the 80's. Isn't 91 octane now the same as 91 octane then.

Seems like these cars TTA's and GN's cannot run without knock on 91 octane gas with stock boost levels. Why is this?

Wasn't 91 octane the best you could get in California back then?

 

[750H.P.V6]

The largest difference between the gas we get now and the gas back in the 1980's is that it's oxegenated with MTBE or Ethanol. I'm not a petro chemical enigineer but I can tell you first hand that it sucks. There is a bunch of info on the CARB (California Air Resource Board) website that details the addition of oxegenates to gasoline to reduce emmissions. This coupled with the fact that we used to get 92 octane back in the 1980's is why even stock turbo Buicks are finicky on the poor overpriced gas we get here in CA.

http://www.arb.ca.gov/homepage.htm

Neal

Just curious what makes todays gas worse for higher performance cars than gas in the 80's. Isn't 91 octane now the same as 91 octane then.

Seems like these cars TTA's and GN's cannot run without knock on 91 octane gas with stock boost levels. Why is this?

Wasn't 91 octane the best you could get in California back then?

 

[iwantatta]

I didn't realize they had 92 octane back in the 80's. But then again i wasn't driving a car. Anybody know when they made the transition to switching to 91 in California?

It's strange that the MTBE crap they put in gas was for environmental reasons (smog) but turned out to be hazardous in other ways (water pollution).

 

[Lhorn]

How much boost are you guys with BONE STOCK setups able to run with 91 octane? I'm getting knock around 10 psi and trying to figure out if it's just @hit gas or if something else is wrong.

 

[iwantatta]

I have not had a way to adjust boost on my TTA (belive stock is about 16.5psi).

On 91 it was showing 5-10 degrees of knock retard under most conditions. From a stop or a roll.

I was throwing VP 103 in until i could get a chip burned and replaced all the little things like fuel filter, plugs, etc. Replacing the fuel filter seemed to help the most. With the race gas i was getting no knock but i was tinkering a lot with correct mixtures. Too much 91 in the tank and it would still knock.

With my 91 TT chip i'm not getting as much knock. Every once in a while i'm peaking about 4. But not as frequent as before.

 

[turbo39151]

I'm running an 86GN almost all stock on 91 oct. It runs ok. When I punch it, then she gets cranky and gives me problems like a poping sounds and some hiccuping after she hits 25lbs of boost! I'm working on dialing that down and getting some new injectors. However, when I ran an OTC 4000 scan on her, there was no knock at all! Nothing...

BTW, do you guys have anyone you'd recommend in SoCal (San Diego area) for a "once over" and maybe proper tuning? I have no idea what I'm doing and I prefer not to "learn" by blowing up my engine :biggrin:

 

[iwantatta]

Did i read that correctly? 25lbs of boost on 91 octane and no knocking?

 

[turbo39151]

Yup! don't ask me how because I have no idea. Either way, even though the sonsors read like everything is running fine, the car doesn't pull nearly as hard as my old 86 T-type. I still have a few kinks to work out.

BTW, I am running a 62mm tb/ and ported plnum with an RJC spacer. Also running Dutt neck intercooler. (I was told by one of the guys at a track event I went to that the addition of these items to his car virutally eliminated knock- so I put it on my car.) Boost gauge is VDO cockpit series.

 

[Turbo Brian]

The family "T" was purchased new. Back in 87, 92 was the standard for premium fuel in this area (1300' elevation). The car drove OK on 92, but there was light audible knock, so we used 93 that was available at only a few stations around here. Even with the 93, there was knock on a hot day.

On a trip to the east coast, Sunoco 94 was available and the car ran better than it ever ran here. The car pulled much better, since there was no KR pulling timing from the motor.

Today, there is not a station in town that has anything higher than 91. Finally admiting defeat, as of this year that car now has a chip with 19 degrees of timing vs the stock 22. The throttle response is worse, but at least knock is under control. Alcohal injection is the next step to protect this otherwise stock car.