verbs

I talked to a few individuals that said they independently tested different Premium octane pump fuels in AZ. They said that together, the premium pump fuel we buy averaged out to be about 87.8 octane, no where near the "advertised" 91 octane.

How can I go about proving what they said to be true? How easy is it to test octane, are there places locally I should look for to test this??

<small>[ December 22, 2002, 09:06 PM: Message edited by: verbs ]</small>

Sears

There are several ways to advertise octane. I would make sure the tested octane and advertised octane are of the same description.

Justin

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Jsears8:
<strong>There are several ways to advertise octane. I would make sure the tested octane and advertised octane are of the same description.

Justin</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't know what it means, but the octane testing formula on all the gas pumps is (R/M)/2 .

<small>[ December 22, 2002, 09:44 PM: Message edited by: verbs ]</small>

Fenris Ulf

I really doubt they tested the gas correctly. If you had really been cruising around on less than 88 octane gas your 5.3L headed car would be toast.

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fenris Ulf:
<strong>I really doubt they tested the gas correctly. If you had really been cruising around on less than 88 octane gas your 5.3L headed car would be toast.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">that is what I thought too....especially at 10.8:1 compression in the desert heat.

verbs

After doing a bit of research, it seems I can take gas here for independent testing:

http://www.testapg.com/ovr.html

Supposedly the AZ dept. of weights and measures takes care of the testing of our gas...

http://www.weights.az.gov/Consumer/A...AtThePumpT.htm

Here is some info on what octane our gas has to be labeled as depending on octane:

Identifies the grade of motor fuel as:

a. Unleaded or UNL, regular or REG for unleaded gasoline with an octane of at least 87;

b. Midgrade or MID for midgrade, extra, or plus for gasoline with an octane of at least 88;

c. Premium or PREM for super, high performance, or premium for gasoline with an octane of at least 90; and


So a bad batch of gas at 89.5 octane could be rounded up to 90 octane and still be considered Premium. Damn.

<small>[ December 22, 2002, 10:04 PM: Message edited by: verbs ]</small>

Unreal

AZ gas seems good to me. Car loves it in fact. 100x better than the california crap I was feeding it. Runs 22-23psi on "91" octane.

99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by verbs:
<strong>
So a bad batch of gas at 89.5 octane could be rounded up to 90 octane and still be considered Premium. Damn.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">About a year ago, local TV station did a random test of 93 octane gas to see if it really was what it was being sold as. Worst result they found was a 92.5

If your worried about the octane and limited to 91, be sure and buy your gas at a very busy station. The fuel will be quickly turned over and you'll have the best chance of getting the gas with the octane closest to 91 at a busy station, rather than stale stuff that's been still underground for a few months at a slow station.

I have a friend at work and her husband tests, various stations for weights and measures. He makes sure the pumps delivery the amount they show. He gets samples to test octane. Most of the time the octane is very close and the if the pumps error they usually error in the customers favor.

Also with the overlap your 230/224 cam has I would think the 91 should be ok. My 224/224 runs fine on 93 with no KR and I have less overlap and more compression.

Let us know what your learn.

<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Fenris Ulf

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 99 Black Bird T/A:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by verbs:
<strong>
So a bad batch of gas at 89.5 octane could be rounded up to 90 octane and still be considered Premium. Damn.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">About a year ago, local TV station did a random test of 93 octane gas to see if it really was what it was being sold as. Worst result they found was a 92.5

If your worried about the octane and limited to 91, be sure and buy your gas at a very busy station. The fuel will be quickly turned over and you'll have the best chance of getting the gas with the octane closest to 91 at a busy station, rather than stale stuff that's been still underground for a few months at a slow station.

I have a friend at work and her husband tests, various stations for weights and measures. He makes sure the pumps delivery the amount they show. He gets samples to test octane. Most of the time the octane is very close and the if the pumps error they usually error in the customers favor.

Also with the overlap your 230/224 cam has I would think the 91 should be ok. My 224/224 runs fine on 93 with no KR and I have less overlap and more compression.

Let us know what your learn.

<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Just so you know, a larger overlap bleeding off cylinder pressure might save you at idle and part throttle, but detonation will still set in at WOT.

Fenris Ulf

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by verbs:
<strong>
So a bad batch of gas at 89.5 octane could be rounded up to 90 octane and still be considered Premium. Damn.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It would have to be a minimum of 90.0 to be accepted.

99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fenris Ulf:
Just so you know, a larger overlap bleeding off cylinder pressure might save you at idle and part throttle, but detonation will still set in at WOT.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">At higher rpm and WOT, the cylinder filling is reduced so while the mechanical compression is high the actual compression can still be low enough that detonation isn't present.

Depends on the set up, just so you know.

<small>[ December 23, 2002, 12:39 AM: Message edited by: 99 Black Bird T/A ]</small>

Fenris Ulf

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 99 Black Bird T/A:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fenris Ulf:
Just so you know, a larger overlap bleeding off cylinder pressure might save you at idle and part throttle, but detonation will still set in at WOT.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">At higher rpm and WOT, the cylinder filling is reduced so while the mechanical compression is high the actual compression can still be low enough that detonation isn't present.

Depends on the set up, just so you know.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Actually at higher rpms, more overlap promotes better cylinder filling (thats why larger cams tend to peak higher).

99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fenris Ulf:
Actually at higher rpms, more overlap promotes better cylinder filling (thats why larger cams tend to peak higher).</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yet the cylinders do not fill as easily at higher RPM as they do at lower RPM, so (case specific) the actual compression can be fine without denotation.

Maybe you've noticed that stock LS1's often ping and denotate on 93 with the stock cam and stock heads with lower compression. Many stock LS1's will sound like a can full of bear bearings rattling around at high rpm. A correctly set up heads and cam car with higher compression 11 to 1 will not do that on the exact same 93 octane gas, with the correct cam selected and good tuning.

My car pinged and denotated at high rpm when it was a bolt on car. Not bad but the car would do it a little. With heads and cam it doesn't do it at all. Atap confirms no KR and the graph is very smooth, unlike before when the pinged.

Again the key being properly matched parts and tuning. A stock cam with 11 to 1 compression and stock overlap, could have real issues.

Happy Holidays

<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

<small>[ December 23, 2002, 10:13 AM: Message edited by: 99 Black Bird T/A ]</small>

SStrokerAce

iTrader: (2)

Just to add some to this.

I recently ran some very good street gas 92 octane on the dyno. Well PHR posted the test results of this gas in the magazine this month. What was interesting is the way the gas was made makes a big difference on when it produces knock and when it doesn't.

I started off doing the dyno tests on a traditional SBC with Sunoco 94, there was no problem with the gas in the engine even though I was running 11.75:1 and 25 deg of advance at 2500 and 35 @ 3500 and up. There was a little rattle but it made good power so I let it go. Then I started in with the 92. Well guess what, it worked as good or better. The test results showed what I thought they would. There are two Octane numbers one is Research Octane and one is Motor Octane. The average of those two gives you the advertised octane number. The two parts however effect the detonation t different levels. The research number is good for full throttle operation (which I was doing) and the Motor number is better for part throttle detonation. Well the fuel ended up having 96.6 Research Octane and 87.6 Motor Octane. That explains why it was as good as the 94 Sunoco.

The point is that a old SBC with 23 deg heads are never going to burn as fast as the LS1 heads, so 91 octane and 10.8:1 should be fine.

Bret

verbs

I'm not so worried about how the gas will affect my car in particular (since I went with a lower compression ratio), I'm more curious than anything to see if the pumps actually hit the ratings they claim.

SStrokerAce, I'm curious to find out which types of gas have more research octane vs. motor octane. I'd be all over the ones with the most research octane.

02 SOM WS6

Gas formulation changes all throughout the year for different reasons(time of the year, prices for different blend stocks for instance) and also varies from one locale to another. Never the less, the gas should always be very very close to what it is advertised as or the pipeline or who ever ships it will send it back before it ever gets to a gas station. I work in the second biggest and certainly the most complex refinery in the U.S. Used to be Amoco, now BP.

Les