1996 Volvo 850 Non-Turbo Questions about Performance

Post by **Troy** » 26 Feb 2008, 00:40

I've been looking around the forum for information about my non-turbo 850 but haven't come across much for performance; I checked all nine pages of performance topics and only found a couple of items for it, which were fairly short in length - unlike it's turbocharged brethren.

In reading about my engine, the B5254S, I learned that it has a 10.5:1 compression ratio which is higher than I realized. I have been running regular gasoline (lowest octane) in this vehicle and know that higher compression typically dictates higher octane to avoid early detonation; I haven't heard any pinging or felt like the car has been sluggish, but I am concerned that this is not the right thing to do.

Am I causing long term problems for my engine by running low octane fuel, or just losing performance?

I would be grateful if someone could point me to a performance thread for the non-turbo engine so I can start considering my options.

Thanks,

Troy in Alaska

Post by **Troy** » 26 Feb 2008, 01:20

Here is a link that J_Guynn provided about octane on a different post (thanks).

http://www.streetrodstuff.com/Articles/ ... /index.php

I'm still looking for more non-turbo performance info

Post by **tjts1** » 28 Feb 2008, 10:36

The quick and dirty NA intake in 3 easy steps

Install an early 960 throttle plate.
http://volvospeed.com/vs_forum/index.ph ... try1168946

Fix the airbox thermostat.
https://www.matthewsvolvosite.com/chat/p ... 0&start=36
The stock airbox and filter is not a significant restriction to the intake. The problem is the stock snorkel going to the airbox. It starts with a 1.5x4" oval and ends with a 3.25" circle at the airbox. So get a 3.25" piece of flexible tubing.
https://www.matthewsvolvosite.com/airbox.php
For a temporary experiment, take off the stock snorkel (takes all of 30 seconds, no tools) and drive it around the block a few times. This only works if you have already fixed the airbox thermostat.

cheers
Justin

sony2000 · Post by **sony2000** » 11 Mar 2008, 15:18

If the computer hears the detonation it will change the timing, and you won't hear it again for a while, because it made its calculation. If you put in the highest octane and step on it, the theory is the computer will advance the timing to generate the biggest bang for you, unless this produces detonation again. Higher octane will produce more MPG because each drop of gas produces a bigger bang. than a drop of 87. You pay more, but you get some of it back in more MPG.

Post by **tjts1** » 13 Mar 2008, 09:24

sony2000 wrote:Higher octane will produce more MPG because each drop of gas produces a bigger bang. than a drop of 87. You pay more, but you get some of it back in more MPG.

Not true. 87 octane contains more BTUs than 91 or 93 octane. High octane is only useful at high load when accelerating hard. In normal driving at part load you will get better fuel economy with 87 octane. At part load the engine is running full advance no matter what the octane. It only makes a difference under high load. The knock sensor is constantly listening to knock and is adjusting advance accordingly all the time.

sony2000 · Post by **sony2000** » 13 Mar 2008, 14:59

So if I can find some 80 octane, and keep a light foot, my MPGs will be better.

Post by **Troy** » 11 Apr 2008, 22:35

I appreciate the input. Thanks for the links Justin; it will interesting to see if I can feel the difference. I would be happy if it just increased my mpg by a few notches.

Troy