Will Lower Octane Cause Detonation on Dyno Tuned GTO
Hey guys, I actually just made an account to post this because I am a little confused and I don't know much about goats. So I have a 2004 Pontiac GTO, 6 speed. It has a few modifications such as an intake, a full exhaust and it was dyno tuned (not by a handheld tuner). However, I have no idea what kind of tune it was because it was done by the previous owner. I assume it's some sort of 93 octane performance tune. My questions is if I, for whatever reason, put 87 or 89 octane in the car, will it cause detonation? Or, will the knock-sensors still be able to save the engine? I know that on the stock tune, the knock-sensors kick in and retard the engine timing (there-by hindering the performance), but would a dyno tune get rid of that fail-safe??
And I know I should run premium only, but I am quite clumsy and will most likely fill up on 87 or 89 one day and not realize until I'm leaving the gas station. I just want to know how bad it can get.
Any input will be greatly appreciated. Thanks in advance!
A dyno tune CAN affect how spark advance is pulled due to knock. If your tuner didn't mess with the tables associated with knock retard or the low octane spark table, you should be ok.
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Originally Posted by Andrea...
You don't need power steering fluid to drive in a straight line. Stop being a lowjo and run that bitch again!
A dyno tune CAN affect how spark advance is pulled due to knock. If your tuner didn't mess with the tables associated with knock retard or the low octane spark table, you should be ok.
^ +1
Your PCM will do magic in preventing knock and detonation. But, if the tuner has played with the timing, or the "low octane" spark tables, or even worse; desensitized your knock sensors! Then yeah, cheesy fuel can cause issues.
Take this ---> Lowest octane we sell is 91 (premium, unleaded) for $1.8/gallon, and 95 octane for $2.4/gallon!!! Full tank of premium unleded 95 for just $11!!! Gotta love this place!
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It certainly isn't a good idea to run low octane. Yes, after detecting knock for a while the PCM will start subtracting timing until it quits but in the mean time your engine is knocking and potentially causing damage. I run 93 and 91 is the lowest I would put in. Not remembering when you fill up is the first sign you'll be one of those old people that confuse the gas pedal and brake and your GTO will end up in the middle of the convenience store and on the news.
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"It's a well know fact that after you hit 400 HP you have to go with split dual exhaust like the LS2 GTOs. The '04s could get away
with single side because they were only 350 HP. With 400 HP and beyond the car wants to turn right at WOT from the thrust."
fuel door & factory & manual does not say 93 and over is required, only that 91+ is recommended, and that 87 is supported too.
87 octane is in fact fine for LS1 & LS2 and is *supported* by stock tune if you can deal with warm weather power loss due to occasional timing backoff.
I've run 87 all winter for decades and a few hundred thousand miles on GTO & Z28 V8s for which 91+ is recommended (but not required).
with these vehicles, mpg *improves* with 87 octane on long cruises compared to 91+.
take the savings to the bank and buy new suspension components with it, trust me you will need them .. :|
it's especially nice when 87 octane is $3.35 and 91+ octane is bizarrely much more like $3.99 or whatev.
my opinion: no matter what the nonfactory tune is supposed to do or not do,
if you want to run 87 octane, then return tune to stock.
fuel door & factory & manual does not say 93 and over is required, only that 91+ is recommended, and that 87 is supported too.
87 octane is in fact fine for LS1 & LS2 and is *supported* by stock tune if you can deal with warm weather power loss due to occasional timing backoff.
I've run 87 all winter for decades and a few hundred thousand miles on GTO & Z28 V8s for which 91+ is recommended (but not required).
with these vehicles, mpg *improves* with 87 octane on long cruises compared to 91+.
take the savings to the bank and buy new suspension components with it, trust me you will need them .. :|
it's especially nice when 87 octane is $3.35 and 91+ octane is bizarrely much more like $3.99 or whatev.
my opinion: no matter what the nonfactory tune is supposed to do or not do,
if you want to run 87 octane, then return tune to stock.
Merry Christmas yall.
Great! Now, all he needs is to keep saving for the next 76 years and he might be able to afford some bushings with his savings! LOL
warm weather power loss due to occasional timing backoff.
Occasional? There's an entire timing table dedicated to low octane fuel and it's quite significant.
And honestly, what's the point of buying a 400hp car only do choke it with low octane fuel and 350hp for a few measily dollars in savings? At 20 cents gallon savings that's $3 a fillup. On a normal 12k a year daily driver car, that comes out to about 4 fillups a month or $12/month.
If $12/month difference in gas bill makes or breaks your budget then you got bigger problems than running 87 octane in a V8 car.
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Originally Posted by Transmission Perform...
The cylinder heads became deformed because the air filter was so dirty they couldnt handle all the build up of air and oil coming through the air filter and the throttle body so i tried replacing the air tube with a cold air intake and i think the extra power blew out the cylinder heads and they crashed through valley pan into the crank. Then the crank spun hard and threw the pistons up to hard to cause a misfire
Occasional? There's an entire timing table dedicated to low octane fuel and it's quite significant.
And honestly, what's the point of buying a 400hp car only do choke it with low octane fuel and 350hp for a few measily dollars in savings? At 20 cents gallon savings that's $3 a fillup. On a normal 12k a year daily driver car, that comes out to about 4 fillups a month or $12/month.
If $12/month difference in gas bill makes or breaks your budget then you got bigger problems than running 87 octane in a V8 car.
Uh, OP said he's worried about a brain fart and accidently filling up with a lower octane, not because he's cheap.
And thank you to all who put in helpful inputs, I was just worried because I used to own a Mustang which only needed 87...
I tried talking to the previous owner but he's a bit daft in remembering what exactly was "changed". I have no problem running 93. Before buying the car I knew that's one of the commitments you should make. Given, even if i don't put 93 in a stock GTO and put 89, it would probably run fine as DD and not as a track car or whatever. However, does anyone know how STRICT the requirement becomes when a car is dyno tuned? I know it depends a lot on the tune...but if I were to put 91...would it cause pinging/knocking/bogging/detonation??
Also, the previous owner said that after tuning the goat, he managed to get 22 city and 29 highway mpg. That's a pretty big jump from what the car is known to give... I haven't gotten a chance to fully test it, but, is this possible or was he just exaggerating? (he told me this after i had already bought the car and he was the owner not a dealer).
Uh, OP said he's worried about a brain fart and accidently filling up with a lower octane, not because he's cheap.
+2. This board of sharks are always sniffing for blood.
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Not driving your GTO to keep miles off of it is like not having sex with your girlfriend so her next boyfriend will appreciate it more.
And thank you to all who put in helpful inputs, I was just worried because I used to own a Mustang which only needed 87...
I tried talking to the previous owner but he's a bit daft in remembering what exactly was "changed". I have no problem running 93. Before buying the car I knew that's one of the commitments you should make. Given, even if i don't put 93 in a stock GTO and put 89, it would probably run fine as DD and not as a track car or whatever. However, does anyone know how STRICT the requirement becomes when a car is dyno tuned? I know it depends a lot on the tune...but if I were to put 91...would it cause pinging/knocking/bogging/detonation??
Also, the previous owner said that after tuning the goat, he managed to get 22 city and 29 highway mpg. That's a pretty big jump from what the car is known to give... I haven't gotten a chance to fully test it, but, is this possible or was he just exaggerating? (he told me this after i had already bought the car and he was the owner not a dealer).
22 city mpg is higher than I ever get. I normally get between 19-20 in the city, and my worse was a single digit number... I have gotten in the low 30s on the highway. It really depends on traffic and your driving style.
Also I wish I could get a tank of 95 for 11 dollars!!!
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you're quite the manwhore now aren't you
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Originally Posted by mike5215@bellsouth.n...
Owing a GTO is like marrying a stripper. You know it's wrong and it's going to end badly, but the sex is so hot you can't help yourself.
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Originally Posted by Brians Goat...
No he ain't doing no freaking manwhoring, he has a collar around his neck lately, he rarely shows up anymore on Saturday's and when he does he usually has some HOT babe with him who causes him to constantly drool and walk funny!!!!!!!
warm weather power loss due to occasional timing backoff.
Occasional? There's an entire timing table dedicated to low octane fuel and it's quite significant.
And honestly, what's the point of buying a 400hp car only do choke it with low octane fuel and 350hp for a few measily dollars in savings? At 20 cents gallon savings that's $3 a fillup. On a normal 12k a year daily driver car, that comes out to about 4 fillups a month or $12/month.
If $12/month difference in gas bill makes or breaks your budget then you got bigger problems than running 87 octane in a V8 car.
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Originally Posted by redtan...
The kids that don't know how to read are always coming on here making false accusations
It would help if you included the username and post ID in a quote. I apologize for not taking you seriously enough to consider it worth my time to look back through an entire thread to make absolutely sure of the context of what you were quoting when you didn't bother to be considerate enough to use this simple feature. The authors of vBulletin have generously provided a means to automatically include the username of the quoted poster and a link to the appropriate post.
Its a performance car. Run high octane gas, all the time. PERIOD. As far as the crystal ball to tell you if it will detonate or not, I dropped it and it broke. IT DEPENDS. Only 11ty billion variables we don't know the values of.
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2004 GTO: TVS 2300, 14PSI. ETP Heads, EDC cam. Stock internals!
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And thank you to all who put in helpful inputs, I was just worried because I used to own a Mustang which only needed 87...
I tried talking to the previous owner but he's a bit daft in remembering what exactly was "changed". I have no problem running 93. Before buying the car I knew that's one of the commitments you should make. Given, even if i don't put 93 in a stock GTO and put 89, it would probably run fine as DD and not as a track car or whatever. However, does anyone know how STRICT the requirement becomes when a car is dyno tuned? I know it depends a lot on the tune...but if I were to put 91...would it cause pinging/knocking/bogging/detonation??
Also, the previous owner said that after tuning the goat, he managed to get 22 city and 29 highway mpg. That's a pretty big jump from what the car is known to give... I haven't gotten a chance to fully test it, but, is this possible or was he just exaggerating? (he told me this after i had already bought the car and he was the owner not a dealer).
Im going to have to say he was exaggerating... If your really in "city driving with stop lights" there is no way your going to get 22 mpg. All in All our cars do get good gas milage for what they are, if driven properly.
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Im going to have to say he was exaggerating... If your really in "city driving with stop lights" there is no way your going to get 22 mpg. All in All our cars do get good gas milage for what they are, if driven properly.
Amen to that one. The 29 on the highway I "might" be able to see if it was a fairly downhill commute. Mine has seen 27-28 on the highway before the heads and cam were added. When I lived in Vegas it was cemented at 12-13mpg with all the long ass stop lights there.
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Don't pump 87 if the car wasn't tuned for it, and/or you can't see what the tuner did.
With the proper timing, 91 or 93 should give you the right amount of miles per gallon, plus i'm sure you didn't buy a GTO thinking to hypermile the car did you ?
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I was down to 1/8 of a tank on a trip through Nowhere, NV. The only gas station for many miles was something that had pumps that looked like they were out of the 70's with the nozzle on the side and mechanical roller dials on the front. All they had was 87 octane. I filled up and figured I would need to take it easy. My LS2 is blown and tuned. I thought it would ping if I stomped on it, but it didn't. I eventually got on it and had it in cruise control at 110 mph for 5 or 10 minutes at a time until I approached the CA border. I filled back up in CA with 91 octane at the first place I could find, but I was down to 1/4 tank. That was about a year ago. No problems then or since.
Last edited by jkhollywood; 01-09-2013 at 08:40 PM.
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Never understood the kind of people that will buy a 15k car that recommends premium, and will not put premium in it because it's "too expensive". If an extra 4-6 bucks a fill up is too much for you, maybe you shouldn't have spent 15k on the car.
Same goes for HDTV. Some people throw down 2k on a 60" plasma, and then refuse to pay for an HD package from the cable company cuz an extra 10 bucks a month is too expensive for them. Really?! Some people are just absolutely retarded.
Put the premium in, can't believe no one else has brought this up yet, but how do knock sensors work?? Think about it the knock sensor only pulls timing AFTER it has already detected knock, so the knock sensors will pull timing but not until it has already been detonating due to you putting in 87 when your tuned on 93 octane timing tables. So the answer is YES use 93 octane always and if you forget and put 87 in then drive it nicely until it runs out and re-fill with the right stuff.
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Will Lower Octane Cause Detonation on Dyno Tuned GTO
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