does it matter which type of gas you use for the dts? if so , which is better? 87 or 91,?
It may take a few miles for the computer to adjust to the Premium...but it will..thanks Jim, I've been running on regular also but I guess I'm going to do premium tomorrow when it runs empty ,thanks for the tips, and my car didn't come with a manual , but I know the guy who use to own my car lives somewhere on this base because he stopped me when I was at the gas station on post, maybe I'll run into him again and ask him if he has it,
If your engine isn't running smoothly on regular, then there's something wrong. There is literally no difference (as far as the PCM is concerned) between octanes under most driving conditions. The ONLY time a change is made, is IF AND WHEN knock is detected. Again, there is no way for the PCM to tell what octane fuel is flowing through the injectors. There will be a slight power difference, slight, and not throughout the power band, only at higher RPMs/high engine load when detonation (gas knock) is most likely to occur, and only IF it occurs. Any noticeable difference in how the engine runs, is just psychological.billdaman said:Sorry I completely disagree..Hands down Premium makes the engine run much much smoother, better power and as Jim said better gas mileage. In my vehicle a night and day difference between Regular and Premium. The engine will run fine on Regular. It behaves like a different engine on premium.
As to your first question... that is possible, I suppose.Could it be that the Performance engine is more sensitive to the octane than the standard lower HP engines?
We have the standard 275 HP engine. I typically fill it with 91 octane non ethanol, but then my wife takes it and fills it with 87 octane with ethanol. I can't say that there is a noticeable difference in how it runs, but it seems like the mileage is better if I drive it more. The Fleet Farm gas stations around here have an 89 octane without ethanol that I want to try running for a while.
That is NOT monitoring octane, that's detecting knock. Hence the engine having KNOCK sensors, not OCTANE sensors. Ambient temperature, humidity, altitude and driving conditions, all contribute to if and when knock may occur, not JUST octane.Superjim said:Actually the engine DOES monitor the octane... the higher octane the fuel is, the less spark knock and the more timing the ECM will add to the engine to take advantage of it.
Or when you KNOW how your car runs on Premium and how much distance you need to pass another car at highway speeds ... then you decide to run Regular in it for a while... just to see how it runs..FWIW, pre '00 Northstars had a higher compression ratio than '00+. Premium was recommended, but it was also fine to run regular with slightly reduced performance. In '00, the owners manuals began recommending 87 octane, and 91 octane for optimum performance. The (FWD) Northstars really haven't changed much mechanically since then.
Not to call anyone a liar, but unless you have drag strip time slips, or dyno results showing a significant difference in power output between the two octane fuels to prove otherwise, any perceivable performance improvement is due to the placebo effect.
Since when do threads on CF stay on topic? :hide:billdaman said:Isnt this thread about which type of gas is better for the DTS? The debate has morphed into spliting hairs as to weather the ECM monitors and responds to inputs from either Octane or detonation.
Amen, that is my exact reasoning on the matter. The discrepancy is negligible to the point that arguing against supreme does not make much sense. Notably, as I mentioned earlier: the battery of tests were run by Gm and they deemed that 91 makes the engine run at optimal and safe levels. Once again, in the owner's manual, the difference between "use" as an imperative and "may" as a potentiality is where I draw the line. If 4$ is an issue for a Cadillac owner IMO, maybe the choice of the car brand was incorrect. Unless the owner were to live in another country where the discrepancy is not as negligible or the gas prices are sky high like in Canada where it cost me not too far from 100$ for a full tank of 91 when I was visiting, going with 91+ will cost you less than a Big Mac trio more on a tank than 87.So, in short, the engine was designed to run on 91 octane, take a moment to price out the cost of replacing the above mentioned components and ultamatly, you decide if saving $4.00 per fill out wieghs the cost of replacing the components you may be damaging in the process.
So, please sum it up. Which octane would you recommend for 2006 DTS Performance? Your post is way above my level.I use 3 ScanGauges - the car and 2 trucks. I have nothing to do with the company, simply a satisfied user who bought them at different times online. You can now daisy-chain 2 units for a total of 8 gauges visible at one time.
In my STS, running 87 octane Shell, the idle speed ignition advance sits between 5 to 12 degrees BTDC depending on engine electrical or A/C load. Open road steady speed at 60 or so it hovers around 33 degrees, occasionally 35 degrees BTDC - the system will advance no further whether I run 87, 93, or dump in 5 gallons of 106 octane avgas (Cecil County Dragway preps). At any other time, timing in these Northstars is incredibly dynamic: it varies rapidly from 12 degrees BTDC during passing maneuvers back to 33 or anywhere in between. The slightest gas pedal change (TPS/MAP/MAF/RPM) affects the advance. You will never be able to track it with any degree of certainty. At 135 mph, advance sits about 22 degrees BTDC, foot in the firewall, 3rd gear. During a full power acceleration run, timing drops quite a few degrees at each shift - as engine load again increases. FWIW, there is NEVER any timing retard to an ATDC value. Even a mechanical/vacuum distributor, with a static setting of 8 degrees BTDC, can never go below that value.
In these management systems "retard" is a relative term and is a moving target. Do not believe for one second that these engines run anywhere near full advance all the time - far from it, in fact.
Also, the maximum variation I have seen in 1/4 mile times, using different fuel mixtures, is 0.35 second, and that could be caused by a heartbeat gas pedal hiccup. The 10.0:1 compression ratio and management systems for the Northstar are very tolerant of a wide range of fuels - but the systems will NOT advance past the max value set into the "computer" by GM.
The PCM for the later (2004+) FWD Northstar engines may or may not allow advances beyond 35 degrees BTDC (I doubt it) - that would have to be graphed by a GOOD scan tool or a Tech-II (GM) tool. Get into the V- cars and all bets are off.
So-called "octane boosters" and their "advantages" are a cruel joke.
What do I do for a living now (retired Navy and retired Johns Hopkins U research vessel captain) ? I build Olds 455 and GM 454 marine engines - all the way from kittycat workboat engines to OMG !! 600 hp sleepers. I live and breathe MSD, Taylor, Pertronix and ACCEL ignition systems.