I recently moved to the area of Iowa City, Iowa. I also recently installed dual aeroforce Interceptors.
I've been looking like hell for 93 octane gas and can't find any. Cedar Rapids has some (about 50 minutes from where I live) but I'm not driving all of that just for 93. I'm also going to post in the regional forums to see if anyone knows if there is 93 nearby.

My questions for HERE are these.

At WOT I get about 2.9* KR. It holds spot on 2.9. I put in a can of octane booster and at midrange WOT it still holds about 2.9* KR but as it gets closer to redline it drops to near zero. It's a canned tune and I know very little about tuning but is it possible it's just tuned that way? Just to ensure maximum timing is there and let it pull it back a touch? Is 1.4-2.9* KR dangerous?

Also, a friend of mine had an idea of spiking my gas with 1 - 1 1/2 gallons of E85. Thoughts on this?

Thanks!

 

You could try mixing E85 and see what happens.

Sometimes i get random 3-4* of KR.

 

I wouldn't mix your gas with ethanol as you'll then need more fuel to compensate or you'll risk running lean and be back in knock territory.

I'd say de-tune for what's available. GMS1 is good with 91 octane as GM would have you believe. Maybe your tune is setup more for 93.

 

I did find this which might be useful to others as well.

Bottom of page

Miles Per Dollar Calculator

 

First and foremost, octane boosters are little bottles of snake oil aka, hopes and dreams. THAT'S IT. Don't waste your money on that crap.

In an ideal situation, you would never see ANY knock but I've come to learn that these motors have extremely sensitive knock sensors and do get ghost knock. The ghost knock typically happens on tip in though from what I've gathered. Midrange knock is probably real but 3* isn't a whole lot. If you've ever data logged a stock file car, you would be surprised how much knock the motor sees. That being said, its best to try and get rid of it as best you can.

The E85 will help tremendously so long as you can tune for it. It will raise your octane and it burns cooler so its like a dual benefit. The downside is that it does go faster b/c of its lower energy level (meaning you need to burn ~30% more of it) and it can be a pain if you travel and can't find any E85 stations.

Good luck.

 

I did mix in about 2 gallons of E85 into a full tank of 91 and now there is zero knock.
Still.... I want to find some actual 93. I'm getting a meth water kit soon anyway so once that happens then I won't worry.

 

If you have E85 easily available, I'd do that over Meth any day. I actually run E47 (50/50 93:E85) and it has done wonders for the performance.

Meth kits make me nervous. I've read one too many horror stories.

 

Ok, another quick question.

I got a progressive meth kit installed and it's pretty much dialed in. I'm not tuned for it. It's simply to keep knock at bay which it is doing just that. Working beautifully.

However, I do OCCASIONALLY get part throttle knock. About .5 - 1.5 degrees knock at 2-3 psi. Not always though.
I've researched and read that likely this is the ECU adjusting timing for best fuel economy. Anybody able to confirm this or at least say "Ah don't worry about it buddy. It's nothing".

 

I think the obvious thing to do here is get a real tune. and if you dont have 93 then just tune for 91 and your meth kit.

 

Mixing the E will raise ur octane, but have u tried a different brand of gas? There are some stations I can't fill at cause I get knock, I go to a diff one and it clear up. Shell is bad for me. Try another gas station first

 

Since people refused to answer my second question about "Low Load - Low PSI knock"... and EVERYONE on this site always recommends to get a retune... I did some research and found some information from a tuner for a large tuning company.

Info for anyone interested.

"
Many of you have noticed while logging your cars, that you see instances of high knock-correction values and low-rpm and low load situations. There has been much speculation about the cause and effects of these occurrences.

To put your apprehension to rest, Tim Bailey, one of our most experienced and knowledgeable tuners has offered the following explanation of this phenomenon:

Modern engine control computers (ECU) monitor and constantly adjust engine parameters including fuel delivery, variable camshaft timing, and ignition timing. Under light load (low boost or vacuum conditions) the objective of this active adjustment is optimized fuel economy and power.

An important component of this active adjustment is changes to ignition timing. Utilizing the highest possible ignition timing is a simple way to enhance the mechanical energy for any given combustion cycle. This enhancement extracts the most torque for a given quantity of spent fuel.

The processes that manage optimal ignition timing at light load are complex and vary by vehicle type. Some ignition timing adjustments are active and based upon sensor feedback. One such sensor is the "knock sensor." This sensor is a simple microphone that listens for engine noise. Complex signal processing inside the ECU helps discriminate detonation from other types of engine noise. The thresholds for noise vs knock vary not only by engine speed but by engine load. The ECU will react to engine noise by actively removing ignition timing. This low-load "knock correction" is a normal and desirable process that promotes optimal ignition timing.

Other timing adjustments are programmed compensations that are predictive in nature. For example, on some vehicles a sharp increase in throttle position predicts a fast change in engine load. In preparation for a predicted change in engine load the ECU will preemptively remove some ignition timing. This compensation is not really knock correction at all but is instead a predictive ignition timing adjustment. Similar compensations exist for a variety of conditions including but not limited to changes in load, air temperature, boost temperature, and acceleration. Tuning strategies for predictive corrections vary by vehicle but are present in some form in every modern ECU.

Unfortunately, the monitors that allow us to monitor the ECU’s activities do not discriminate between predictive timing adjustments and those responding to sensor input. However, regardless of the type of compensatory timing adjustment, at LIGHT load, these corrections are a normal means with which to optimize power and fuel economy. Under light load there is simply not enough cylinder pressure to allow engine damage. As a result, light load "knock correction" is not something to worry about. This is a normal process that is even more apparent when utilizing stock calibrations designed to utilize a range of fuel quality. "

 

Part throttle KR on an LNF is quite normal.

You can mix in 25-30% E if you like to raise the octane without a tune. Fuel trims go ~+10% and they carry into WOT and no CEL. That's how my ethanol experiment started on the LNF 3 years ago for the same reasons you have, but my KR was on 93. Over time many of us found E47 was the sweet spot on the LNF stock fueling system. E47 is 99 octane BTW when mixed with 93.

The LNF has a wideband 02 sensor to control fueling.

It is better to tune for it, but it'll run fine once the LTFT's compensate in a few miles.

 

Here's a calculator online for % E blends, octane results, ect.

http://www.intercepteft.com/calc.html

 

Ya that light load knock is normal, see it on stock tune since I bought car new

 

I have been having this exact problem with GMS1 and 91 octane. Carries almost 3 degrees of KR. Dropped in a gallon of e85 and it got rid of all of it.

Almost made a thread about it. I hadn't been watching my DashHawk and never noticed the KR. Wonder if it's always been like that or the summer gas sucks.

 

Find out if it is straight 91 or 87 with Ethenol in it. Places around where I live sale 91 and some 93 but all of the 93 and all but one place that sales 91 is just 87 with ethenol in it. That will effect things there. You can ask them (the gas station) or find out who the distributor is then talk to the distributor. The'll tell you where and what gas they take to different places. That's what I did to find out who has straight 91 and who blends theirs.

 

One thing that does help is to find the Top Tier gas stations and always try to get their gas. I did notice some difference.
WOT knock is gone now though thanks to a little meth.

 

Holiday is on Top Tier and their gas is ****.