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Discussion Starter · #1 ·
I finally got rid of my iPhone 4S and went back to android (thank god). I ordered the Bluetooth adapter immediately and the TQ app was my first download.

I started playing with it today. I didn't have time to sort everything out and configure all the logging options, but i paid close attention to the real time data while driving for about an hour.

I set an alarm to go off when 2* of knock retard are reached, and set a graph for real time knock info, as well as airflow, timing, boost, and other parameters.

Only mods are K&N Drop in and intake resonator bypass. 89 octane fuel, 44* ambient air temp 48-55* IATs.

INFO

First observation is this car is CONSTANTLY fighting knock on the stock tune with 89 octane. My 2 degree alarm went off before i got out of my neighborhood. Throughout the drive every time i touched the throttle the KR graph was moving around in the 0.5-1.5 degree range. Every now and then it would trigger the 2* alarm (maybe every 5 minutes), and once read as high as 4* of knock in typical driving. At WOT it seemed to knock on the hit, pull a little timing and be pretty much right on the knock threshold, with occasional flecks of KR in the 1.5-2.5* range.

When cold the car makes 7psi of boost @WOT. After 190* or so boost typically hovers in the 9-10psi area, with occasional bumps up to 11-12. Peak boost was mid 12.x psi, but it doesn't make that regularly or sustain it.

Timing advance on spoolup is around 2* as the turbo comes on. At peak TQ (3K RPM) it's in the 4.5*-5.5* range, and at peak hp (5.5K) its around 12.5*...out the back door it hits 17* right at the rev limiter...but at that point boost has tapered off to 7psi.

I watched airflow during a 1-2 pull and the car spiked to 116g during 1st gear but could only generate 98g in 2nd, i'll have to pay more attention to this.

I need to start properly logging the car so i can get a better handle on things.

More info to come as i play with it. :) I wonder if the mild intake changes are contributing to the knock. I can only imaging what the knock looked like while towing in the middle of the summer. :uhh:
 

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Discussion Starter · #2 ·
For some reason i cannot read IAT2. Does that function just not work? Would really like to check intercooler efficiency.
 

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First observation is this car is CONSTANTLY fighting knock on the stock tune with 89 octane.
Since new about once every other tank I have severe knock event that my dealer "can't duplicate". When I say severe it sounds like someone shacking a can of marbles for a couple seconds proceeded by a loss of power. This is running nothing but top teir gas either 89octane or premium. I have been trying to figure out exactly what causes this to happen & when to maybe get my dealer to look harder before something breaks.

It always seems to happen after a period of constant easy speed around 35-55mph, you hit a steep hill/grade which requires more throttle to maintain speed, if you are easy & the trans doesn't downshift there is a small chance it will happen. One route I take about 4times a week it wont happen 9 out of 10 times, yet those fluke times it happens.

Two days ago it was 36degrees outside & I had only been driving about 20minutes, car was fully warmed up & sure enough hit one of those steep grades on this route & it started knocking right before the trans downshifted. once in the lower gear I proceeded up the hill like it never happened. This was with Shell Premium. I have had this happen with Kwik trip & mobil gas(actually mobil 93 octane was first time I noticed it).

I would say it never happens in flat roads, but one day in 50degree weather I was accelerating from a dead stop, between 25-40mph (in 4th gear I beleive) around 2,000-3,000rpm right before the shift it started knocking with a loss of power. Again this was after a 3+ miles stretch of easy driving.

Its almost as if fuel is loading up in the cylinder when driven easy at 25-45mph & once I increase engine load or need to accelerate is when all the excess fuel is detonating.
 

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Since new about once every other tank I have severe knock event that my dealer "can't duplicate". When I say severe it sounds like someone shacking a can of marbles for a couple seconds proceeded by a loss of power. This is running nothing but top teir gas either 89octane or premium. I have been trying to figure out exactly what causes this to happen & when to maybe get my dealer to look harder before something breaks.

It always seems to happen after a period of constant easy speed around 35-55mph, you hit a steep hill/grade which requires more throttle to maintain speed, if you are easy & the trans doesn't downshift there is a small chance it will happen. One route I take about 4times a week it wont happen 9 out of 10 times, yet those fluke times it happens.

Two days ago it was 36degrees outside & I had only been driving about 20minutes, car was fully warmed up & sure enough hit one of those steep grades on this route & it started knocking right before the trans downshifted. once in the lower gear I proceeded up the hill like it never happened. This was with Shell Premium. I have had this happen with Kwik trip & mobil gas(actually mobil 93 octane was first time I noticed it).

I would say it never happens in flat roads, but one day in 50degree weather I was accelerating from a dead stop, between 25-40mph (in 4th gear I beleive) around 2,000-3,000rpm right before the shift it started knocking with a loss of power. Again this was after a 3+ miles stretch of easy driving.

Its almost as if fuel is loading up in the cylinder when driven easy at 25-45mph & once I increase engine load or need to accelerate is when all the excess fuel is detonating.
That is pretty strange. Datalogging it and showing it to the dealer would be my first recommendation.

Fuel doesn't get stored up in the cylinder. Most of what enters is burned off, and if you have extra, it will only reduce the combustion chamber temperature and make detonation less likely. That is, unless each burn is incomplete enough to cause detonation, and that brings us back to your spark plug gaps.
 

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Discussion Starter · #5 ·
Your car is actually triggering the knock sensor every time you touch the pedal. Seems shocking, but i will graph it and post up. My car knocked yesterday while gently accelerating through the gears behind a school bus. More than 1* in EVERY gear, at a very low rate of acceleration.

It's not loading up with fuel, the car just has too much ignition timing. Timing gets advanced when you're gently part-throttling it, and when you add load/throttle the car holds a bit more timing than it should until the knock sensor goes off and it begins to pull it. The low octane tables are aggressive for 87, and the high octane tables are aggressive even for 93.

I spent 6 hours researching our ECM yesterday because i plan to tune my own car instead of purchasing a tune (used to tune Mitsubishi's, but GM tuning is completely new to me and a lot is different). There's no info on here, but several people with HPTuners and EFI Live have been exploring the stock ECM. One guy found that he had to pull 3* of timing out of his stock car to get it down to 0 knock on 91 in normal conditions.

Many cars are tuned like this now because the ECMs have gotten so fast in their knock responses.
 

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Discussion Starter · #6 ·
That is pretty strange. Datalogging it and showing it to the dealer would be my first recommendation.

Fuel doesn't get stored up in the cylinder. Most of what enters is burned off, and if you have extra, it will only reduce the combustion chamber temperature and make detonation less likely. That is, unless each burn is incomplete enough to cause detonation, and that brings us back to your spark plug gaps.
It's all in the ignition timing. Adding a bit of fuel during spoolup could help offset this.

One guy on EFI Live showed a 12* KR (extremely severe knock) on the stock tune at about 2200rpm.
 

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Pretty interesting stuff Hoon. Kinda curious myself...I tried a tank of 87 recently once it got cooler and it feels like my car "hiccups" once when I'm about 3/4 of the way on the throttle at 2000 RPM after shifting. I've never felt the pulsing others describe, but I'm fairly sure that's it severely adjusting the timing for a second.
 

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I notice mine doing it again at low rpms and say 50% throttle in a higher gear(30 mph in 4th gear) at the end of the last tank. It was a mix of 87 and 89. Now it has mostly 89, not seen it happen. Hoping adjusting the plug gaps to .032" will not aggravate it and actually help it.
 

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what is the car supposed to be doing? ive used torque too and i have the knock sensor on my front page and i see the timing advance, but how much is too much? the most ive seen is 2 .
 

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Discussion Starter · #10 · (Edited)
I'm pretty sure knock is the reason cruze dyno graphs look like they were drawn by someone with Parkinson's.

I had the opportunity to play around a lot more tonight. It's incredible how lean this car is tuned. At full throttle the commanded AFR is 13.7:1 until you hit 3.5K rpm, at which point it gradually goes richer. In the high rpm it can command anywhere from 12.5 - 10.7 from what i've seen. I'm not sure what exact parameters the ECM uses to decide the AFR. During some pulls it would be down near 11:1 above 5.5K and during others it wouldn't go richer than 12.5 all the way up to the limiter.

The car is tuned that lean for fuel economy, which is why it's so prone to knock with low boost and timing levels in high load situations. 89 Octane, IATs in the 30s.

A typical highway hill:




Full throttle 3rd gear pull 3500-6500:



Timing vs PSI:





More to come.


what is the car supposed to be doing? ive used torque too and i have the knock sensor on my front page and i see the timing advance, but how much is too much? the most ive seen is 2 .
The car is doing exactly what GM says it should. Running lean as **** and pulling timing constantly to keep the motor safe and put 42mpg on the window sticker.

2* is fine, no worries.
 

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I was trying out the app earlier too. I need to sit down and read up on it and play with it in the car. It feels quicker 0-60 than the run I made, 10.2 sec. Wasn't a great launch....lol. What are you guys shifting at?
 

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I shift between 3-4000 normally, except when I feel like saving gas and going long distances

Sent from Ru5ty's galaxy S III
 

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Discussion Starter · #13 ·
I was trying out the app earlier too. I need to sit down and read up on it and play with it in the car. It feels quicker 0-60 than the run I made, 10.2 sec. Wasn't a great launch....lol. What are you guys shifting at?
Yeah I don't think it's accurate at all. I did 2 pulls, one was 10.1 and one was 10.3 (spun the tires a bit).

I ran one out to the 1/4 mile and it said i ran 18.5, and there's no way that's accurate. It was a better launch than anything i had at the track (only did 2 passes) and i went 16.8 at the track.

Full throttle i shift around 5500. In a 1/4 mile do not shift to 4th, wind it out in 3rd. Your 1/4 mile time and trap will suffer regardless of how fast you shift. The car just doesn't have the steam to pull hard in the taller gear and it costs 3mph at the traps in a stock car.
 

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I shift between 3-4000 normally, except when I feel like saving gas and going long distances

Sent from Ru5ty's galaxy S III
3-4K before shifting. Wow. I very rarely see 3000 while accelerating and don't have any issues keeping up with traffic leaving a stop light. I found that if I shift at 2500 I come out of the shift at 2000 and the turbo reengages fast enough that I don't have to worry about acceleration.
 

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Yeah I don't think it's accurate at all. I did 2 pulls, one was 10.1 and one was 10.3 (spun the tires a bit).

I ran one out to the 1/4 mile and it said i ran 18.5, and there's no way that's accurate. It was a better launch than anything i had at the track (only did 2 passes) and i went 16.8 at the track.

Full throttle i shift around 5500. In a 1/4 mile do not shift to 4th, wind it out in 3rd. Your 1/4 mile time and trap will suffer regardless of how fast you shift. The car just doesn't have the steam to pull hard in the taller gear and it costs 3mph at the traps in a stock car.
That kind of verifies what I was feeling last night. Winding to 6K is worthless on a stock tune. Except in 1st because it winds out so fast. I also thought it was quicker than that. My butt dyno still works pretty good......lol.
 

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Discussion Starter · #17 ·
Nice charts there. I don't think I want to know what this car would look like on 87 octane.
Started 87 octane testing today.

When i switched from 89 to 87 the car was using the timing it's been used to for the last 12K miles. I've been watching the timing and knock readings closely for about 150-200 miles. In that time the highest knock reading i've seen was about 3.6 degrees. As soon as i switched to 87 i got the most severe knock the car has seen, with a KR of 4.9.

Every time i touched the throttle the car would trigger my 3 degree alarm, which was only happening maybe once every 20 minutes on average before.

Fast forward 7-10 minutes and i could no longer get the car to knock above 3*. I beat on the thing hard...full throttle pulls all the way to the limiter, flooring it in 6th at 1500rpm or less for extended duration, etc...whatever i could do to trigger kncok and still could not get more than 2.5 degrees.

Within 10 minutes the ECU had completely adapted to the 87 and was running 1-2* less timing depending on load and rpm, keeping the knock threshold exactly the same on 87 as it was on 89.

So there you have it. The engine will run a bit stronger on 89 than 87, but there is very little, if any safety advantage to the higher octane.

93 Octane soon.

This is full throttle at 2K rpm, 87 octane. Note the peak of 4.9*, and the motor knocking with almost no timing in it. I wouldn't see this on 89 unless it had a bit more timing:

 

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Discussion Starter · #19 ·
You threw out 1-2 degrees. Based on how much KR you really hit that time, I'm wondering if it pulls more static timing than that. Is there any way to tell exactly how much spark advance you are getting between the two?
Yes sort of, but it sucks because you can only do a line graph for one thing at a time. If i do one for spark advance it doesn't factor in things like coolant temp, IAT, Command AFR, and other things that can affect the knock threshold. Real tuning software is more than i want to spend at the moment. Eventually i'll be able to do this stuff much more accurately.

What i'll have to do is graph the spark advance in the most controlled environment possible on the street...like go to a deserted stretch of road and floor it at say 1000rpm in 3rd gear and run it out to the limiter...then repeat at the exact same place in similar conditions on higher octane fuel....then over lay the graphs afterwards.

It's not completely accurate but should be good enough for our purposes.

At low revs timing seems to be down in the 0-1* range, about 11.5 at peak hp.

This is down from the 1-2.5* range with 12.5 at peak
 

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Great work i cant wait to see the results with 93 Octane.
 
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