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Discussion Starter #1
well early in January, i decided to get the CMR tune done right...on a dyno.

a local dealer became certified as a Chrysler CMR tuner, he already was for GM and Ford.

the results were great.
406rwhp and right under 420rwtq

after a while, a couple weeks, my LX club had a dyno day at a different shop.

my results were not the same.
366rwhp :worried:

took my car back to the original tuner shop for him to diagnose as i wasnt even feeling the original power anymore.

first pull.
360rwhp.
gettin worse.

after looking at the data logs, owner of the shop sees that there is 7 degrees of knock resulting in pulled timing, ergo loss of power.

he asked if i used different gas.
nope. chevron 93 all the time.

he checked his results and decided to test the bad fuel idea.
yep.
he adjusted timing and i immediately gained 25rwhp back.

he adjusted a little more and sqweezed a bit more power out of it but decided to not do anymore after getting to 389rwhp.
bad gas was his idea for the loss of power and due to the over-sensitive knock sensors, he didnt want to go any leaner just in case i come across some good gas or decide to add a little race gas on occassion.

i have always used the same gas and i guess it doesnt matter if ya do. there is so much crap gas out there nowadays that our cars suffer and we will never be able to tell if we are getting our good moneys worth from these theives at the pump.

chevron i think is supposedly the best in my area, but go figure.
 

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he didnt want to go any leaner just in case i come across some good gas or decide to add a little race gas on occassion.
well hopefully you start getting some good gas soon.

but i didnt get this statement above. the reason you were getting alot of knock, is because your gas was low on octane. so it was pre detonationg. if your tune is lean as possible right now, then it will only help you once you get some good gas in it.

but i assume what the tuner did was run it a little richer. along with retarding the timing a bit.

you could try running some octane boost with your fuel, and getting a retune. if you pull alot better results, than just run octane boost with every tank of fuel.
 

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Discussion Starter #3
well hopefully you start getting some good gas soon.

but i didnt get this statement above. the reason you were getting alot of knock, is because your gas was low on octane. so it was pre detonationg. if your tune is lean as possible right now, then it will only help you once you get some good gas in it.

but i assume what the tuner did was run it a little richer. along with retarding the timing a bit.

you could try running some octane boost with your fuel, and getting a retune. if you pull alot better results, than just run octane boost with every tank of fuel.

sorry, yeah i meant that it's running as lean as possible so when i do get better gas, it will be even better and ready for it without running too lean
 

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Don't add octane booster as it tends to foul the spark plugs, although we have not tried the Torco octane booster.

We see the exact same thing at our shop here in Virginia, not all gas is created equally. Around here the most consistant fuel seems to be BP/Amoco.

But, just reitterating that your CMR tuner was right on about the gas.
 

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Discussion Starter #5
yeah i wish we had amoco or sunoco or somethin good. even if it cost more, just to make the best quality gas available and consistent. never happen.

only have chevron, shell, exxon/mobil.

shell is worthless from experience. chevron seemed to be the best.
 

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yeah i wish we had amoco or sunoco or somethin good. even if it cost more, just to make the best quality gas available and consistent. never happen.

only have chevron, shell, exxon/mobil.

shell is worthless from experience. chevron seemed to be the best.

i know shell was poor in the past. they were responsible for buggering up fuel level indicators on alot of vehicles. but nowadays they are supposed to be one of the better fuels out there. shell is what i use all the time now. and i havent had any problems. but i dont have any data per se, to back them up.
 

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So here's my question.

After you pay to have the car CMR tuned. It is still adaptive? In other words the tuning will still change or the performance will change based orn bad gas, atmosphere, etc, etc....
 

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bad gas = more knock retard which = less power
 

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This is kind of interesting to me because I want to get this done soon, but it's not like you lose your CMR tune after it's set then - do you? What's the point of perfectly setting your A/F ratios if the car can just change them back? During a CMR tune when you dial it in, is it just for the exact atmospheric conditions and gas you are currently running while on the dyno?

Eric
 

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Once the CMR tune is on the car, it doesn't go away. The timing is what gets pulled if you get some bad (ie lower octane) gas. When the computer pulls timing...you lose power. As soon as you get good gas back in, the power comes back. The computer gets info from the sensors on the vehicle and then compensates as necessary, for example the knock sensors detect knock/detonation the computer pulls timing until the knock sensors stop detecting knock. Thats a simple explanation.
 

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Thanks DTP, I want one now for sure.

Eric
 

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Ok- So why did it seem like this guy had to get the car retuned?
 

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if all he had was a bad gas situation, he shouldn't have needed to retune
 

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Thanks dtpracing that's what I thought too. The car should simply adjust and then re-adjust back...
 

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Discussion Starter #15 (Edited)
what they said, i didnt need to get it retuned after all, it will perform according to the gas.

i figured since i use the same gas company it would always run well. i was wrong about that.
 

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Thanks dtpracing that's what I thought too. The car should simply adjust and then re-adjust back...
yes, it would adjust with an extreme retard in the timing. which correlates to a big loss in power. which he could feel. so he brought it in to the tuner to check it out. the tuner came to the bad gas solution by making a few tweaks.
 

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yes, it would adjust with an extreme retard in the timing. which correlates to a big loss in power. which he could feel. so he brought it in to the tuner to check it out. the tuner came to the bad gas solution by making a few tweaks.
Well, I got a question, will the puter adjust to "good" gas?....It's winter here in Ohio and the fuel companies put additives in that result in poorer performance.

So, If I get a cmr tune on this gas, when spring hits and good gas is available again, will the computer advance timing ect....I'm thinking it won't but would love some input on this.

Seems to me I'd be better off waiting to get tuned when I have summer gas mix...would this be correct?
 

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It all depends on how "good" the gas is in the winter. If the car is tuned and can run approx. 21 degrees without much KR (1 or 2 degrees is OK), then it will "adjust up with better gas. We have seen cars pull as much as 7 degrees of KR with "bad" gas.
 

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Well, I got a question, will the puter adjust to "good" gas?....It's winter here in Ohio and the fuel companies put additives in that result in poorer performance.

So, If I get a cmr tune on this gas, when spring hits and good gas is available again, will the computer advance timing ect....I'm thinking it won't but would love some input on this.

Seems to me I'd be better off waiting to get tuned when I have summer gas mix...would this be correct?
the computer doesnt "know" what quality of gas you are getting. it simply pulls aor adds timing depending on the amount of knock it is reading on the sensors.

so to answer your question. YES, the computer will adjust the timing to whatever quality gas you put in. good or bad.
 

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Since mine is a daily driver and we have the crap 91 Octane, I think I'm just going to do my custom tune for 93+ octane (half tank of 100 unleaded) for trips to the dragstrip and dyno results.

I don't want to optimize my 91Oct tune and then get a load of bad gas.
 
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