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Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, octane boost in Cadillac SRX Forums; ^ not here to argue, you are right it highly depends on the engine but I was only talking about ...
  1. #16
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    Re: octane boost

    ^ not here to argue, you are right it highly depends on the engine but I was only talking about cadillacs here, I have both Cadillac engines v6 in my SRX and V8 in my STS, I'm just stating how the car feels when filling the car with higher octane (premium) vs regular.
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    Re: octane boost

    mjcaddy...I knew what you meant...you're just fine...

    Bill

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    Re: octane boost

    Butt dyno really should not count.

    It also depends on the ECU, if it is set up to run 87 the 91 is wasted as it does not have the map for it so you wont really get any more out of it.

    My AutoX car is tuned to run on C16 and if I run a lesser fuel I have to change stuff so I don't burn it down, but if I run higher I see no gains, well I may gain a bit but not that I could tell without a dyno. The car in stock form will listen for knock and pull timing as needed when running poor fuel, much like the SRX does but it cant detect awesome fuel and keep pouring timing to it past what the engineers set up.

  4. #19
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    Re: octane boost

    I have only an opinion on this... The 3.6 has a oddity to it.. It burns oil from "leakage" through the fixed pcv valve. This causes a high particulate issue. This leaves a large amount of carbon on the pistons, valves and slowly but surely damages the exhaust cat converters.

    I'm thinking the fuel you used also has some extra detergents added with the higher octane rating... So I'm sure you felt better response, from the system cleaning up a little... This of course is a estimated educated guess.

    Note:when I bought my 2008 SRX... V6...3.6 there was a large deposit of oil in the cold air intake elbow... Cleaned it and checked car fax... The cats had been replaced at 45k miles... Thus, confirming the known issue.

    Seems GM has been aware of the issue (Google search cadillac srx 3.6 and "pip") it should come up with the info that says look for irregular oil consumption, and the a list of actions for a dealer/mechanic to address the issue.

    I personal run a burn rate modifier, which allows the fuel to be burned at a more efficient rate... As well as lowering the exhaust particles by about 30 persent, and has other plans cleansers as well.

  5. #20
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    Re: octane boost

    Higher octane fuel does not have more detergents in it. Tier 1 gasolines do. And an octane higher than what the manufacturer recommends/requires for an engine does NOTHING to enhance performance. Repeat: NOTHING. PJ.

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    Re: octane boost

    yes higher octane gas does nothing if your car's computer cannot compensate for it...but sometimes higher octane DOES have more detergents...I try to use Top Tier myself...

    Bill

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    Re: octane boost

    Quote Originally Posted by PJ1520 View Post
    Higher octane fuel does not have more detergents in it. Tier 1 gasolines do. And an octane higher than what the manufacturer recommends/requires for an engine does NOTHING to enhance performance. Repeat: NOTHING. PJ.
    sorry what did you say? couldnt hear you?

    what ever to the gasolines, and detergents... not sure if you could know every gas and its compisition. winter fuels and summer fuels.

    as for Octane - my car manual says it can run on 87 but i get better fuel milage and pereviable smoother idol with better octane fuels, and subjectivly have noticed .7 more miles a gallon with 95 octane compared to 87... both havin (at least listed on pump)10% crap in it.

    plus, just to through this out there... my guess if a person made any modifications to exhaust or intake of cold air - more octane would mean more efficency.

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    Re: octane boost

    As I have stated before, and not going to argue, but the 87 octane recommendation is only for the target marketing to those wanting a CTSV but budget is less. This applies to the cheaper Dexos blend oil VS full syn V8 recommendation.

    The 3.6 DI NEEDS a superior oil due to the design of the timing chain set and oil dependent tensioners....same with the fuel. 11.3:1 and 11.5:1 compression ratio.....which any tuner that has logged one of these will tell the ECU is constantly pulling timing due to detonation vs when we run 93 and see little to no detonation. It can be 15-20 plus whp and the fuel economy is proof as well. Any time an engine is not running at optimized timing advance, power and economy is lost.


    The screaming bold caps post may apply to a 9:1 CR non DI passenger car engine that will not benefit a bit running a higher octane. Apples & oranges here when your talking high compression DI vs low compression port injection.

    The .7 amcon realizes is on the low end, we have seen 1-2 mpg improvement running 93 over time.....but pj is correct that detergents are not part of octane, all bulk fuel is the same...the detergent additives of the top tier fuel companies is added at the bulk plant when pumped into the transport tanker, and while they are very effective with a carbureted or port injected engine running 45-55 PSI injector pressure, on a DI engine they have zero effect as the fuel never touches the intake valves, and with DI injectors operating with 2,000-3,000 PSI, the fuel injectors are kept clean and deposits cant form at those pressures. But for any non di engine, always use a top tier.

    How port injection with detergent present top tier fuels keep intake valves clean for 100-200k miles:




    How DI engines it has zero effect:
    RX Performance Products/RevXtreme.com 941-721-1826

  9. #24
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    Quote Originally Posted by amcon
    pereviable smoother idol with better octane fuels,
    Octane has ABSOLUTELY NO EFFECT ON IDLE. he ONLY time the PCM makes any adjustments from lower octane, is if and when detonation occurs. And that is NOT happening at idle. It's all placebo effect.

    MPG will only be effected if the PCM is compensating for detonation (aggressive acceleration/high load/ high RPM conditions) I'm curious. How many tanks did you run with 87, and how many with 95, under identical, controlled conditions before arriving at your .7 MPG figure?

  10. #25
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    Re: octane boost

    good question, not really sure, i normally get gas from the same station, same pump... i can say when ever i do a test - remember its just me in a car and not anything overly sientific, i look to eliminate as many variables as possible. (not comparing long express way trips to around the town trips) and always do at least three full tanks per test.

    as for the .7 that is what i have documented at least... i have had other times where it has been higher. however, quoting high findings is never productive... i like to quote the least, if another person finds more... thats great.

    as for idle the key word is precieved. (placebo effect? i already know higher octane fuel gets me better milage... so at idle i already think it feels better- the key word here was PRCEVED)

    and as for fuels all being the same across the board -

    there is a difference in summer fuels and winter fuels... that can not be disputed. also, content of ethonal... a gallon of american gas is at a range of btus... one documents btus at 127,500, where at another documents a gallon at 119,500 btus. the point is in quotes below - says it best.

    "One US gallon of gasoline contains 114,000 BTU of energy; depending on the time of year, and depending on what is in the gasoline. It is getting harder to find gasoline's that does not contain 5 to 10% of Ethanol. Ethanol is ethyl alcohol; the kind of alcohol in beverages; beer, whiskey, bourbon, vodka, cocktails, etc.. It takes one and a half US gallons of ethanol to equal the energy in one US gallon of gasoline; the reason... because ethanol only has 76,100 BTU's of energy per gallon. Less energy means less miles per gallon." http://www.hho4free.com/gasoline_vs_ethanol.htm

    of corse we can get more scientific than this but it makes the point very well... not all gas is the same.

    question: you said "the detergent additives of the top tier fuel companies is added at the bulk plant when pumped into the transport tanker, and while they are very effective with a carbureted or port injected engine running 45-55 PSI injector pressure, on a DI engine they have zero effect as the fuel never touches the intake valves"

    so, the fuel never touches the valves (or top of pistons???), if there was any consentration of motor oil in the fuel, (for example: my 3.6 v6 motor, is know for high oil consumption, and also know for the cats going bad from 35k to 70k miles) wouldnt that leave carbon deposits on the pistons, rings and valves? i dont think the fuel would "burn off" all the oil ... just a thought, would love to know yours.

    ----------

    I have other posts on here about increasing gas milage... i will general recall the numbers - removing the resonator + 2 miles per gallon, noticable increase in sound (in a good way) and increase in performance. changing to a K&n air filter - 0 increase (went from a normally dirty air filter, to a K&n filter), no noticable change in performance. increase cold air flow through the airbox - loss of 1.8 miles per gallon, very noticable performance increase. swapped out cat back custom exhause system (magnaflow 2 1/4 in and out) for the old system, much better sound, maybe just a slight slight increase in performance... may just be that cuz it sounds deeper and tighter that i think its better. lol

    my point is that i have been playing around with the car seeing what changes are good ballances.

    at this point i get just over 17 miles a gallon with a heavy foot ...

    ----------

    I have other posts on here about increasing gas milage... i will general recall the numbers - removing the resonator + 2 miles per gallon, noticable increase in sound (in a good way) and increase in performance. changing to a K&n air filter - 0 increase (went from a normally dirty air filter, to a K&n filter), no noticable change in performance. increase cold air flow through the airbox - loss of 1.8 miles per gallon, very noticable performance increase. swapped out cat back custom exhause system (magnaflow 2 1/4 in and out) for the old system, much better sound, maybe just a slight slight increase in performance... may just be that cuz it sounds deeper and tighter that i think its better. lol

    my point is that i have been playing around with the car seeing what changes are good ballances.

    at this point i get just over 17 miles a gallon with a heavy foot ...

    ----------

    MPG will only be effected if the PCM is compensating for detonation (aggressive acceleration/high load/ high RPM conditions) I'm curious. How many tanks did you run with 87, and how many with 95, under identical, controlled conditions before arriving at your .7 MPG figure?

    again to adress this again... no idea what your saying with the pcm and compensating of detonation...

    but!!! using my daily driver, doing my daily driving, to my daily activities, with me in the car ... not compensating for humidy, or wind direction as well as smog levels or even high or low daily tempetures, and def not tracking fuel densities or moisture contamination.

    i just reset my computer, and drove in a way that eliminated variables as much as possible - and tried not to make comparsons if i did abnormal type drivin.

    and that is how with out carbon testing the fuel or doing btu tests or desity fuel testing i came up with the numbers... always another issue to look in to... more efficency in an engine will give either or type results... you either get more fuel milage or more performance... both do not equate to better gas milage shown on the dash board.

    if i feel more power when i step on the gas pedal do i let up? or keep the pedal down and enjoy the more power?

  11. #26
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    Re: octane boost

    I think what he is saying is about the computer and octane...Octane allows the PCM (computer) to advance or retard timing (among other things) within the programmers parameters for performance without causing spark knock...if your PCM cannot take advantage of octane beyond, say 87...the higher octane gasoline choice and subsequent price is wasted...there may be higher detergents or some other additive but really...the extra expense is wasted as the engine cannot take advantage of anything in Mid grade or Premium grade gasoline...

    ...buying from a Top Tier gas station is a separate matter as Top Tier is a group of gasoline sellers that agree to a higher level of standards than some other gasoline sellers...you should be getting better fuel from Top Tier and that's why I seek them out for purchase...

    ...since first trying higher octane fuels in my cars since 1985, I have seen no advantage in cars that couldn't exploit the higher octane (by settings before computers and by settings within the computer when they became available)...my C5 Corvette and GTO recommended 91 or better...sometimes they got 92, 93 or 94 but I never saw any "better" performance...some people use lower than 91 and report that for the most part...they see (feel) the same performance when drive normally...but when performance is required...timing is retarded in the PCM (or whatever that cars version of a computer or chip has) and the cars run poorly...my departed 1999 Bonneville SSE recommended 87 octane and I tried both 89 and 92 without any benefit in the octane bump...in fact...my car performed worse and mileage suffered.

    ...bottom line...it is your car and you may choose to do with it how you like...your results are your results...I just don't see how higher octane in an SRX V6 will create any benefit unless you change the PCM parameter engineered at GM (provided you haven't changed the PCM as that changes the rules either good or bad)...

    Bill

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    Re: octane boost

    What he said.

    Your computer does not know the fuel is better and is not looking for it so it will not use it. Also you would need a battery pull or a few tanks before the computer will relearn, it takes away timing fast but does not give it back so fast to protect the engine.

    When I got my SRX tuned at Westers he asked if I wanted the tune for 87 or 91, he told me straight out I will get more mpg from the 91 tune and fuel, if I use a lesser fuel the ecu will pull timing and be safe but if I use 94 the ecu has no idea what to do with it.

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    Re: octane boost

    Quote Originally Posted by silversport View Post
    I think what he is saying is about the computer and octane...Octane allows the PCM (computer) to advance or retard timing (among other things) within the programmers parameters for performance without causing spark knock...if your PCM cannot take advantage of octane beyond, say 87...the higher octane gasoline choice and subsequent price is wasted...there may be higher detergents or some other additive but really...the extra expense is wasted as the engine cannot take advantage of anything in Mid grade or Premium grade gasoline...

    ...buying from a Top Tier gas station is a separate matter as Top Tier is a group of gasoline sellers that agree to a higher level of standards than some other gasoline sellers...you should be getting better fuel from Top Tier and that's why I seek them out for purchase...

    ...since first trying higher octane fuels in my cars since 1985, I have seen no advantage in cars that couldn't exploit the higher octane (by settings before computers and by settings within the computer when they became available)...my C5 Corvette and GTO recommended 91 or better...sometimes they got 92, 93 or 94 but I never saw any "better" performance...some people use lower than 91 and report that for the most part...they see (feel) the same performance when drive normally...but when performance is required...timing is retarded in the PCM (or whatever that cars version of a computer or chip has) and the cars run poorly...my departed 1999 Bonneville SSE recommended 87 octane and I tried both 89 and 92 without any benefit in the octane bump...in fact...my car performed worse and mileage suffered.

    ...bottom line...it is your car and you may choose to do with it how you like...your results are your results...I just don't see how higher octane in an SRX V6 will create any benefit unless you change the PCM parameter engineered at GM (provided you haven't changed the PCM as that changes the rules either good or bad)...

    Bill
    The first paragraph you have dead on. With any non DI engine of a lower CR running octane above what the engine can use is a waste no argument. The second paragraph is also dead on in relation to non FDI engines where the fuel coats the valves, and the injectors operate on a low pressure 45-55 PSI....not so with a DI engine where no fuel touches the valves...and the injectors operate at 2-3000 PSI not allowing for any deposits to form. DI engines the added cost of a top tier fuel is useless in these areas where it was, and is critical to any older port injection of carbureted engines.

    On the DI engines, the factory parameters are set to take advantage of 93 octane....it is the knock sensors detecting detonation that the ECU/PCM then commands the timing to be pulled. THIS is why we see better fuel economy running 91-93 over 87...and you are also correct that to be real accurate, a controlled test needs to be done.....but hundreds have posted results on highway trips showing just that, and any tuner will verify they see the detonation and timing pulled under load (moist is correct, no effect at idle at all) while doing road tuning or on the dyno.

    Just ask VMax motorsports Pete Incaudo who developed the iceolator and CNC patteren ported TB's.....he has done testing like no one else and if the car to be tested has 87 in it the gains are greatly reduced by the detonation detected.

    I think the confusion here is some are basing this on old carbureted and port injection lower compression engines/cars where it is a complete waste of $ to run a higher octane than the CR of the engine needs...in fact put 110 race fuel in a 9.5:1 engine on the dyno and you will make LESS power as the higher the octane the more stable and controlled the burn rate....and if you don't have the CR to support it, your throwing away $$. Todays DI engines are 11.3-11.5:1 CR so it is impossible to NOT perform better on 93 than 87.
    Quote Originally Posted by conedoctor View Post
    What he said.

    Your computer does not know the fuel is better and is not looking for it so it will not use it. Also you would need a battery pull or a few tanks before the computer will relearn, it takes away timing fast but does not give it back so fast to protect the engine.

    When I got my SRX tuned at Westers he asked if I wanted the tune for 87 or 91, he told me straight out I will get more mpg from the 91 tune and fuel, if I use a lesser fuel the ecu will pull timing and be safe but if I use 94 the ecu has no idea what to do with it.
    Partly correct. We can tune the standard timing tables to 1-2 degrees more max advance so it will do even better than the stock/factory tune, but on 87 the ECU/PCM will still pull timing under a load. We see it every time a car is on the dyno when were logging it...and I expect that is what he is reffereing to.
    RX Performance Products/RevXtreme.com 941-721-1826

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    Re: octane boost

    Keep in mind none of us have a DI engine.
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  15. #30
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    Re: octane boost

    right...we have a variable valve timing version...

    Bill

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