So baseline is 10 degrees BTDC. Can this be advanced at all on 87 octane? How much can it be advanced on 93 octane? And how much increase in power / fuel economy can be expected from the change?
Thanks all, 86 GT.
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09:30 PM
PFF
System Bot
lateFormula Member
Posts: 1048 From: Detroit Rock City Registered: Jul 2002
I've been wondering that for a few years now. Not just for my Fiero, but for just about any car with a distributor. Current generation ignition systems that employ a knock sensor are able to provide the most ignition advance within their programming.
I wouldn't expect that you can advance the timing a whole lot more, probably less than four degrees at most. I have wanted to test this on an engine dyno to see what can be done. I believe that the end results would be a marginal increase in fuel economy (1-2 MPG), and possibly a more responsive throttle - the engine would rev a bit quicker.
[This message has been edited by lateFormula (edited 10-17-2011).]
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10:45 PM
Patrick Member
Posts: 38569 From: Vancouver, British Columbia, Canada Registered: Apr 99
Unless you also plan on increasing the compression ratio of your engine, using anything other than Regular gas is a complete waste of money with the stock 2.8 or duke.
However, that doesn't negate you from experimenting with the ignition timing. I've advanced the timing on both my '86 GT and '84 duke. Makes for slightly better gas mileage and performance, but also makes for a "dirtier" running engine.
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11:00 PM
masospaghetti Member
Posts: 2477 From: Charlotte, NC USA Registered: Dec 2009
a waste means, run the oct rating just above where pinging stops. Higher octane is less flamable, so to speak. You would have to test advanced timing, vs octane, vs price difference.
Advance base timing then ECM just retard it back. Too much base timing them ECM in hosed but doesn't trip a error code... Because there Isn't one... DTC 42 usually means ignition module or wires between module and ECM is bad.
Base timing affects engine starting.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Higher octane fuel isn't a total waste on an engine with carbon built up on the piston tops and cylinder tops (basically every engine that hasn't been rebuilt). The added octane lowers the likelihood of pre-detonation and pinging due to hot spots and/or increased compression due to the lower volume at TDC.
Also, in Canada it isn't a "complete waste" for another reason (although the benefits are marginal). The higher the octane rating, the more detergent additives there are which keep your injectors running more evenly.
Also, in Canada it isn't a "complete waste" for another reason (although the benefits are marginal). The higher the octane rating, the more detergent additives there are which keep your injectors running more evenly.
Like in US, May depend on which brand... Some use better detergent in all grades, others only on higher grades. Here Chevron/Texaco uses Techron® in all grades but in Canada? Not sure... FAQ page is hosed... Web site for canada look like all grades meet Top Tier spec, which may means all grades gets Techron. http://www.chevron.com/prod...usttech/toptier.aspx
imperialoil.ca (Esso/exxon) says
Esso gasolines also help keep your engine clean while you drive All Esso gasolines include cleaning agents in their formulations. Routine use of Esso gasoline should help keep fuel injectors and intake valves clean, and reduce future engine problems.
TOP TIER All grades of Esso branded retail gasolines meet TOP TIER Detergent Gasoline Standards.
Just use the regular it was designed for at a stock advance. You CAN advance it far enough it wont turn over with the starter. Your not going to gain anything by using premium in a stock engine...except depletely funds faster. I ran 110 octane aviation gas in my racecar locally. Timing was way above stock and the gas cost almost double. Of course it was far from a stock motor too. Id never have done either to run it on the street.
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03:38 PM
Patrick Member
Posts: 38569 From: Vancouver, British Columbia, Canada Registered: Apr 99
Higher octane fuel isn't a total waste on an engine with carbon built up on the piston tops and cylinder tops (basically every engine that hasn't been rebuilt). The added octane lowers the likelihood of pre-detonation and pinging due to hot spots and/or increased compression due to the lower volume at TDC.
Blooze, I would've agreed with you 30 years ago, but is carbon build-up anywhere near as much of a problem now with computerized fuel injection as it was in the "old days" with carburators and no computerized monitoring/fuel adjustments?
Engines in this day and age shouldn't be running rich, and therefore they shouldn't be building up a lot of crap in their combustion chambers.
quote
Originally posted by Bloozberry:
Also, in Canada it isn't a "complete waste" for another reason (although the benefits are marginal). The higher the octane rating, the more detergent additives there are which keep your injectors running more evenly.
With all due respect, I've heard that's total bunk. The oil companies would like us to believe that, just so those of us who only require Regular gas waste our money on their higher priced fuel.
The carbon isn't from running rich so much as it is from burning oil due to poor valve stem sealing, especially on tired engines, so yes... it is still a problem. As for the hype about detergents, your guess is as good as mine about the truth behind the added detergents... all I know is what the gas companies tell us. I also clarified my statement by saying it was a marginal benefit at best.
If it's a stock 2.8L don't waste your money, advancing timing beyond stock may or may not provide more benefit and it's limited at that. There is a point where additional timing advance does not cause detonation or provide any performance increase whatsoever under those circumstances. The best way to determine the benefit is on the dyno as has already been mentioned. The closer to top dead center that combustion takes place the more load your rod bearings are likely to be subjected to and most of us know they wear out fast enough without help. If you must, 89 octane and 2 additional degrees is about as premium as you should go. No matter how much timing you add it will not change the fact that you are still igniting the same compression ratio which dictates the octane requirement.
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05:27 PM
Patrick Member
Posts: 38569 From: Vancouver, British Columbia, Canada Registered: Apr 99
Patrick: A complete waste, by that you mean the added spark advance gains you nothing?
That's not what I said.
quote
Originally posted by Patrick:
I've advanced the timing on both my '86 GT and '84 duke. Makes for slightly better gas mileage and performance, but also makes for a "dirtier" running engine.
Masospaghetti, using anything other than Regular gas is what I considered "a complete waste" (of money).
quote
Originally posted by Patrick:
Unless you also plan on increasing the compression ratio of your engine, using anything other than Regular gas is a complete waste of money with the stock 2.8 or duke.
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06:06 PM
Patrick Member
Posts: 38569 From: Vancouver, British Columbia, Canada Registered: Apr 99
The carbon isn't from running rich so much as it is from burning oil due to poor valve stem sealing, especially on tired engines, so yes... it is still a problem.
My Fieros would never puff blue.
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06:10 PM
sardonyx247 Member
Posts: 5032 From: Nevada, USA Registered: Jun 2003
Wrong, there is no knock sensor on a stock 2.8 so the ECM will NOT retard it back. The ECM does not "know" what you set it to, it assumes it is set to match the constant set in the code. If base timing is set wrong, it will be that many degrees off through out the whole code.
An example where advanced timing is used for more power is the "hypertech" chip, it bumps up timing, up to about 6 degrees, BUT only at high rpm and under WOT. BTW that is all the hypertech chip does, nothing else. (I looked over the code.)
Higher octane is good for higher compression, and/or boost.
