so I got my scan gauge today (i'll be writing more about it in the other thread after i get a good handle on it). first thing i did was warm up the car and take it for a spin.

i took it at WOT a few times from say 20-60mph or so. my knock retard is reading ~5.5. I don't know a ton about what's normal, cause i'm slightly new to the scanning thing. i read that you usually lose abour 2 hp per degree of KR...
its about 85 degrees outside with moderate humidity. air intake temps were sitting around 92.

my mods are: Intense PCM, wizaired CAI, 180* t-stat.
i've been running higher octane gas, but i have 87 in my tank now, so i could scan KR with it.

so i'm wondering if this is good, or bad, or normal. i know the intense messes with that stuff, and i'm tempted to swap my stock pcm back in and scan. maybe its just too frickin hot out.

by the way, the aeroforce scangauge is really cool! looks slick and seems to work nice. more about it later!

thanks,
Bill

I want to hear more about the amount of knock your aeroforce gauge reads vs. the scan tool. Are they similar?

the "scan-gauge", as they call it, is the only thing i'm using.

almost on empty...i'll probably throw a quarter tank of 94 in there tonight.

Oh sorry, I misunderstood and thought you got a scan tool and the gauge.

Canadian GTP had a thread awhile ago where he was troubleshooting his KR (led to his purchase of a downpipe). You might find some things in that topic with regards to normal amounts of KR.

Zuul, get that 87 octane out of your tank if you're running with a reprogrammed PCM.
I know the PCM's for GTP's require premium (92+ octane). The reason you might be getting KR is because of the low octane fuel matched up with reprogrammed settings from the PCM.
Put your stock PCM back in and scan it. See if your KR improves. If it does, then your problem is with the low octane fuel in your tank & your PCM.

What if the premium they offer around here is 91? Is that considored regular for you?

I get 93 in Austin. I think most of TX gets 92.

Fuel stations in the higher altitudes generally see lower octane at the pumps. It has to do with that whole air density issue. 91 in denver is like 93 in L.A. And yes if your running a reprogramed PCM you need to run higher octane fuel. Remember the reprogrammed PCM uses more aggressive timing and fuel tables so you need the high octane.

91 is premium around here usually. I use the "Ultra" 93 though for ~ $0.05/gal more since I don't want to mix gas and some stations here use 93 as premium with no 91. Some of the Sunoco stations here offer 94 for ~ $0.20/gal more than 91 too, but it's not worth it.

Higher octane is the one sure method of reducing KR for those that need to worry about it. If your not modded and running a stock pcm I wouldn't worry about going higher then what the owners manual calls for. A STOCK GT will be fine on 87 and see very little if any gain out of higher octane.

my car is mostly stock and I'll never put 87 in it...the cleaner that engine burns (read that more efficent) the longer its going to run without giving you problems...you can skimp when you go to the pump but it saves you nothing...more KR will mean poor mileage and less power...so you'll just use the cheap stuff faster...my car never gets anything less than 89 and if I modded it more it will move up to the premium stuff.

hey guys thanks...
i usually run 91 or 93, i just threw a quarter tank of 87 in to check the KR.
we have 87,89,91,93,94 in the area. 94 is usually 30-35 cents more than 89.
we'll have to see how things go with 91 now.
thanks again,
bill

I wish I could get 94 here. I'd gladly pay the extra money for it.

we have 93 and 94 here and generally run 20 cents more a gallon then 87. And when you total it up for a 12 gallon fill up its $2.40 more a tank.

Actually, if you don't need higher octane and experience no KR, there is no need for it.

Higher octane is just for reducing KR. Knock occurs when the gas explodes too soon during a piston compression. Once you get passed the point where the gas explodes correctly during a compression, anything more does no good.

Also, 93 contains just as much detergents as 87.
“But the advertising says Super gives me really clean gas”
Marketing strategy so you can buy the more expensive gas. Noticed they never advertise 93 contains more detergents than the lower 87.

Thunderbat:
If you have a mostly stock GT, you are just wasting your money by getting Super or racing fuel. It drives different because the higher octane explodes differently. Don’t believe me? Have someone put gas in your car for three times. Don’t let them tell you what they put in. You may like the quick responds of 87. You aren’t treating the car w/ Plus or Super. You can get a 87 and replace the fuel filter more often.

Zuul:
Now, you do need it because the reprogrammed PCM changed the ignition timing in the car. The web site where you got the reprogrammed PCM probably mentions this.

There's no difference in the detergents in regular or premium. It can actually hurt the engine if you use a higher octane than the car requires. High octane is NOT better gas, it simply has more chemicals that resist explosion.

Some info on gas.
http://www.pontiacstreetperformance.com/psp/Mythsgas1.html

Thats way more than I ever wanted to know about octane.

Interesting though.

well i ran her as dry as i could and filled up with some 93. drove for 10 minutes, and checked KR at WOT and got 5-6 degrees. i'm going to assume that the computer just needs to learn the gas or something? i'll give it some more time.
-bill

Also, if you replaced the PCM with a reprogrammed one, you have to do a CASE learn so the PCM knows where the crankshaft is positioned.

If you just had it reprogrammed, then you don't need to do this.

Yea, the computer will need a few miles to get used to the new octane. Check it after a few more days. If you are still getting knock, you probably want to upgrade the exhaust to free up some back pressure.

still getting 5.8 degrees at wot on the way home from work this afternoon.
what worries me is that the change from 87 to 93 didn't change ANYTHING yet.
waiting patiently....

Did you have the U bend replaced? Won't help much but it may take it down a degree.

Put the stock PCM back in and see what kind of KR you read.

ill be doing the ubend and exhaust tips eventually...soon as i find some tips.

i'm doing that m90 SS conversion as soon as zzp releases that kit. i hope i dont have a billion degrees of KR then! i wont be using the intense pcm, as it says not to. it looks like dhp or stock pcm for that.

well after 8 days of running 93ish, it didn't help... its actually worse.
now its giving me 6.5 degrees KR!

probly throw the stock pcm in after an upcoming trip (not me driving). anyhow, that doesn't seem like a solution...i like my intense!

Any update on this? I am questioning the AeroForce reading.

See if someone else has a scan tool. Surprised to see a PCM do THIS to a car.

Plus if you put in super and you are getting more, then there is something wrong with the car itself such as plugs, fuel filter, dirty throttle, e.t.c.

Downpipe may help.

You lucky asses

There's only ONE station that sells 92...everybody else has 91 .. And it sucks

Somebody said AutoZone or someone will Scan for KR for free??

I don't know if they'll scan for KR because you need to have it on the road or a dyno but they do scan for trouble codes.

That's because of your altitude. At that elevation 92 is like 94 for us here at sea level.

yup.

no update on this yet... i've been on vacation all week.
i gotta replace the fuel pump resistor when i get back, ill probly reset the PCM at the same time, and see how it goes from there.
any advice on how to treat the car during the 'learning' period?
after a few days if theres no change i may swap the intense with the stock pcm to see if thats the culprit or not.
ubend is coming soon. downpipe i probably will not touch....

thanks,
bill

Drive normally but vary. Highway + city.