ymsin,

What exactly did you have done to your 300se for the performance tuning?
I am wanting to get mine tuned, but I'm not sure what to do.

Thanks

__________________
Oliver

I drove up north 4 hours to see this chap who tunes the car pretty well. He cleans the fuel injectors and then tunes the car for maximum performance. After the tune, I get very responsive acceleration and the fuel usage is maximised.

There involves no modification of parts. Just straight tuning and configuration.

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

That is exactly what I need to do. I'm not after adding any high performance parts (other than the K7N air filter).
I just want the car to run well.

Thanks

__________________
Oliver

Sorry Oliver - I dont know how he does it. If I did, I would have loved to share it with you.

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

It's OK. Do you think a standard tuning shop would be OK, or would it need to be MB specialist?

Thanks

__________________
Oliver

Woah ... I think thats a very subjective question.

Of course, I'm inclined to believe that the MB garage would be a better alternative. However, sometimes independant may (or may not) be able to tune it well. I know my local mech. can't tune for nuts.

The good side is, once properly tuned, a W126 tuning can hold for a long, long time.

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

You don't notice knocks or pings because the knock sensor detects the knocking and retards the timing to prevent it. The timing is not the only thing that gets retarded, your power and fuel mileage suffer from this as well.

By using premium or mid grade the timing will be restored and fuel mileage and performance will be restored to some level. Remember, these are high compression engines, most of them 10:1.

It would take some scientific testing to determine the correlation of price per gallon versus change in fuel mileage. I expect that it would be cheaper to run regular, but I expect that with retarded timing, you may be asking for a carboned up engine.

Good luck,

The energy content of gas is just about the same regardless of octane rating. There should be no noticeable gain in performance by using higher octane fuel unless the engine is sensing knocking and retarding the timing. In this case you are simply getting worse gas mileage by putting low octane fuel in and your engine is getting lower gas mileage than it should.

The octane rating is a rating that determines the gasoline's resistance to spontaneous ignition upon compression, and is the percentage of the hydrocarbon chain that is actual octane. Octane numbers below 100 are a measure of the octane in the fuel while number over 100 are considered a "performance rating" since it is not possible to have an octane percentage higher than 100 but it is possible to have a fuel rated at higher than 100 octane. Fuels rated over 100 are simply more resistant to spontaneous ignition upon compression.

The aspect of your engine that determines what octane you need to use is the compression ratio. High performance engines need high octane fuels because they are generally high compression engines and need a fuel that withstand the high compression without igniting without the spark plug causing it to or very rapidly burning causing and an uncontrolled explosion in your engine rather than a slower, more controlled burn.

The fact of the matter is that using low octane fuel does not necessarily decrease gas mileage and performance because it is lower octane, this may only be the case if the engine is sensing knocking and compensating with a different, less efficient timing. The fact is that using low octane fuel causes ENGINE DAMAGE because it causing knocking. Detonation is not something that is good for your engine, it puts massive amounts of stress on the internal components of the engine.

If you have a low compression engine, you may be able to get away with putting a lower octane fuel in it. However, if your engine is high compression, you must use high octane fuel, or cost yourself much more money through very premature engine failure. Do not be cheap with your gas if you have a high compression engine.

-Ali Al-Chalabi, using 93 octane.

[Edited by Ali Al-Chalabi on 03-02-2001 at 01:53 PM]

Ali - if we use a premium fuel, is it an issue of pyschology that we think the Benz runs better than it otherwise would?

I sometimes think in this manner as the oil companies would spend millions - and not to mention, "technical bulletins" (read "propoganda"), to convince us that their new premium fuel works better ...

(And I'm one of those suckers who get sucked so easily ... )

[Edited by ymsin on 03-04-2001 at 10:23 AM]

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

Yes, I would definitely use premium fuel in any car that I own.

I think that part of the fact that our cars run faster with premium might be psychological. However, I do not look at it in such a manner that a high compression engine would run better on premium, I look at in a manner such that the car runs like it should on premium. If premium is not used, you will see a decrease in performance and gas mileage because the car will be retarding the timing to prevent knocking.

In conclusion, premium may not necessarily give a boost in gas mileage, but I would use it anyway. At least in the US, the price difference is not that significant in the scope of how much it costs to keep a car running anyway.

As a side, small airplanes require 100 octane fuel that typically costs around $2.50 a gallon in the US. In the UK this fuel can run over $6 a gallon!

[Edited by Ali Al-Chalabi on 03-04-2001 at 02:18 AM]

ymsin: I asked this very same question a few months ago when I bought my 91 300E. Here in Canada, we are going throught a rough time with gasoline prices at the moment... they are climing each week, with price gouging on weekends/holidays. I was of the opinion " gas is gas" and filled up with the cheapest price at the pump, until I read over my owners manual which stated the lowest octane I should use to maintain engine duribility and longevity was 91. Hamilton the price differance between 89 octane and 94 octane is about $0.10, which means I pay about $5.50 more for the 94 vs the 89 on a fill up of 55 liters. (prices flucuate every day/week) After I read the replys to my post (http://www.peachparts.com/shopforum/showthread.php?threadid=9867) I've been filling my thirsty 124 with nothing but high test. I think Kebowers said it best when he wrote "Gasoline is one of the major 'operating' costs of driving for many people since it costs $0.08 -$0.10/mile

Owning a MBZ for say 15 years and 150,000 miles costs at least $30,000 in depreciation and repair for a per mile cost of $0.20--roughly twice the fuel cost. Insurance costs another
$15K for another $0.10 per mile.

Trying to save 8% of $0.08/mi, at best, gets you $0.007 per mile, or maybe $100 a year tops. If that amount of money makes a significant difference to you--sell the car now, you
cannot afford it. You will collapse when the cost of 'hard parts' damage comes due."



ymsin - spend the extra few $'s and fill up with premium, then rest assure your treating your engine well.

Cheers for now;
EADG
91 300E