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Old 08-27-2004, 11:33 PM   #31
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There'* one, only like what 1,999 to go? haha but seriously, don't let this thread die. I'm sure there'* a ton of broke college kids out there scared shi#less to put less than premium in their car for all the wrong reasons. I think working this out will benefit a lot of people. Sometimes its about saving a buck, ya know?
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Old 08-29-2004, 10:27 PM   #32
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Quote:
Originally Posted by DrJay
As you may have noticed lately I've been putting a few myths to rest, most notibly the whole 'backpressure' issue.
I'm not so sure we put the issue of the 'backpressure myth' to bed. The majour reason for this is that in some cases backpressure will help you...but not at the race track.

In your link, it'* not really a usefull deabte if someone takes the standpoint of debunking extremes;

http://www.uucmotorwerks.com/html_pr...torquemyth.htm

I've never actually heard anyone say more backpressure is better and certainly when we speak of L67 engines, and L36s, the PCM is capable of adjusting fuel mixtures and of being programmed with Power Enrichment tables that won't cause you to burn exhaust valves.

If one takes the view of trying to understand the effect of backpressure on an engine'* performance, then certainly there is something to be learned. If on the other hand one were simply trying to exagerate extremes then it'* a moot point.

Some back pressure will help your part throttle response...but it won't help you at the track.

Since we ask so much of our engines over a wide range of conditions all aspects of it'* configuration are compromises. We could have variable valve and camshaft timing as well as variable exhaust length and volume if we hope to optimise all conditions, short of that we must make compromises.

Cheers,
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Old 08-29-2004, 11:24 PM   #33
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I know a way to settle this debate. Someone with a L67 will use nothing but 87 octane and see how long they can handle the low power and pinging/knocking noise coming from the engine. Also we can see how long the engine will hold up.

I'm no Gearhead but I can tell you that if your engine is knocking, there is something very wrong.

Err on the side of caution, the owners manual says to use Premium Unleaded fuel.
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Old 08-29-2004, 11:55 PM   #34
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My 95 SSEi says you can use 87 but 91 or better is recommended. It says right in the gas door UNLEADED ONLY PREMIUM RECOMMENDED....My 01 Regal SER2 car says PREMIUM UNLEADED ONLY.....By the way only 91 gets put in the Regal (till the mods come on heavy) and 91 with octane boost goes in the Bonne.
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Old 08-30-2004, 01:05 AM   #35
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*sigh* well if anyone can provide proof of this in documentation then the debate can continue. I've provided several web pages to counter but nothings been done in return. I've already put out all the info someone would need to figure it out on their own and I don't think at this point the debate is getting anywhere. If you look at the surface and it scares you then go with premium only but I think if you actually look at the reasons for detonation and the PCM'* ability to counter it you may find it safe to use a lower grade. But hey, I put it out there you decide.

Foghorn - As I'm doing with the above statement, I'd appreciate any sources you have for this information. Hey if I'm wrong I'm wrong but opinions and thoughts on the matter will only get us so far. If you can find an expert to agree with you it would help. That way I could look at the technical reasons behind it. This is all a learning game, right?
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Old 08-30-2004, 12:59 PM   #36
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I just wanted to point out that I used 89 for over 35,000 miles, and never noticed even light pinging, but like I said before, I don't abuse the car. I drive with a very light foot 95% of the time. I'm about to fill up on 87 this week as an experiment. I'll let you all know how it affects my performance and gas mileage. This is mainly my daily driver right now, so I'm not interested in performance, just economy. I drive a 2000 Mercedes C280 on the weekend (my wifes car), and that requires premium too, but the city gas mileage is better, highway about the same or slightly worse.

I would also say that if you are experiencing pinging on a regular basis, by all means use the highest octane available. I'm not advocating damaging your engine.
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Old 08-30-2004, 03:46 PM   #37
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yeah be sure to check out any audible pinging right now compared to 87 octane. This is only at WOT so if you wouldn't mind 1-2 romps... If you're able to hear it that means the computer can't compensate. If you can't, you never have to worry about using 87 and damaging your engine. Should be interesting
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Old 08-30-2004, 04:40 PM   #38
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I have romped on it with 91 and never heard pinging, but with a scantool, it did detect some knocks, and KR kicked in. I will run 87 through for one tank before I try WOT first, to let the computer learn the new gas. That'* a 3 week cycle for me, so it will be awhile before I can report back.
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Old 08-30-2004, 08:43 PM   #39
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Oh yeah you'll get KR on the scantool but as long as you can't hear it the PCM is taking care of things and there'* no real issue. THanks for doing the experiment phase of the debate haha
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Old 08-31-2004, 06:19 PM   #40
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I'm sorry but I don't believe this stuff about the knock sensor keeping the engine safe. Until I cleaned out my MAF I heard plenty of knocking, whatever the PCM was doing did not help. New knock sensor, no change.
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