Now im going to don my flame suit....

I know the Gm reflash is crap......trust me I know! I plan on either getting a tune or keep reading so I can tune myself. But anyways..

In the future I plan on getting meth/water injection. I currently have a issue with knock on the gm flash and I think ive tracked it down to crappy fuel.

Alot of guys locally have issues with their high end cars knocking like crazy on our fuel and yet can go over the border and get zero knock on a fuel 2 grades lower. So now im kinda stuck. So I was thinking..

First of all im fully aware that to get the most gains, benifet I have to tune for it but....

Would a person be able to get away with running water/meth with a small small nozzle to help combat the knock (raise the octane)?

Im going to experiment with fuels from different stations. I currently get Chevron 94 but apparently guys are seeing less knock on Shell 91. So Im going to try it.

If your issue is fuel yes it could make a difference.

What is your afr's?



FU Tuning

AFR is 14.2-14.9 under normal driving conditions and once in pe it drops down to 10.8 or so.

I feel the issue is gm commanded pe to only enact when its floored. (Sorry if my terminology is not right)

I talked to another person with the reflash and he witnessed the exact same numbers and situation but is experiencing next to no knock...He is running 93 but in the states.

I do have access to another reflashed pcm, so im going to give it a try and see if that changes anything but I dont think it will since my afr's are normal and the exact same as another persons.


**Again I know I need a real tune...Im trying to learn how to....its hard..lol.

This might sound kinda weak, but have you tried adding a bottle of Octane boost to a full take a gas to try and bring it up to par?

I have found the Ecotec will show knock from running to rich (really any motor can). 10.8 is pretty rich.

Leaning it out (a tune) could fix it. If you run meth you will make it richer, and might not cure your problem.



FU Tuning

Ill know more after this weekend.

Going to try usa gas and see if i get more or less or the same knock.

I'm going to add that the knock isn't in the time I'm rich.

It starts when the car is in boost and asking for 14.7 afr. It'll spike up. And then usually follow by the incremental recovery period.

If my pe was enabled at like 30% throttle there would be zero issues I feel other than being to rich.

Addicted to meth wrote:I have found the Ecotec will show knock from running too rich (really any motor can). 10.8 is pretty rich.

Leaning it out (a tune) could fix it. If you run meth you will make it richer, and might not cure your problem.

I second that! There seems to be a happy middle, depending on your type of forced induction, around 11.5:1.

Just a theory, but overly rich leads to a slower burn in general, which leads to higher EGTs (potentially still burning as it exits), which eventually leads to pre-ignition. Again, just my theory.

Philly D wrote:I'm going to add that the knock isn't in the time I'm rich.

It starts when the car is in boost and asking for 14.7 afr. It'll spike up. And then usually follow by the incremental recovery period.

If my pe was enabled at like 30% throttle there would be zero issues I feel other than being to rich.

That is an altogether different problem too lol. Needs to be tuned in the end.

oldskool wrote:

Philly D wrote:I'm going to add that the knock isn't in the time I'm rich.

It starts when the car is in boost and asking for 14.7 afr. It'll spike up. And then usually follow by the incremental recovery period.

If my pe was enabled at like 30% throttle there would be zero issues I feel other than being to rich.

That is an altogether different problem too lol. Needs to be tuned in the end.

DING! DING!! We have a winner.



FU Tuning

I'm going to plug in my reflash and log timing advance & knock retard on 93 octane for him. If his timing advance numbers are significantly lower than mine could that be indicative of poor quality fuel? I know there are other factors but I'm trying to find more proof that poor quality fuel is at least partly to blame. I had almost no knock with my reflash when I took a "spirited" drive last night. Didn't log timing advance that time unfortunately.


"In Oldskool we trust"

Yah...so time to learn it is....

Was hoping I could band aid things for the time being till I learn.

Ill be starting a tuning thread soon I guess..cause I still have alot of questions that I haven't been able to find answers for yet.

On that thought......If I get the injector constant correct in theory I should be able to limp back and forth to work?

I've always wanted to learn for myself too but I just don't have the time. Then again you have way more motivation than me since I have a GREAT tuner nearby who charges fees that are beyond fair.


"In Oldskool we trust"

If I had one of those guys even remotely close id drive days to get a tune.

Hell ive contemplated flying someone over here to the west coast for a tune.

In short....im jealous...lol

lol. Well at least you get to learn a new trade. I'll definitely be trolling your progress with hpt in the future.


"In Oldskool we trust"

our knock sensors are too damn sensitive. wether its just a crap design or if gm intended them to be THAT quirky, i dont know. it might help to simply wrap the threads with teflon tape and see what happens. do this at own risk, though lol

i dont quite understand how "your" fuel wouldnt be as good as anywhere else's but if its been known to cause issues i simply would not buy that fuel and go elsewhere.



It's nice to be injected but I love being blown.

-Z Yaaaa- wrote:our knock sensors are too damn sensitive. wether its just a crap design or if gm intended them to be THAT quirky, i dont know. it might help to simply wrap the threads with teflon tape and see what happens. do this at own risk, though lol

i dont quite understand how "your" fuel wouldnt be as good as anywhere else's but if its been known to cause issues i simply would not buy that fuel and go elsewhere.

Brad this is a Ecotec. And yes they might use the same knock sensor, they are different in regards to knock etc..

I firmly believe the LD9 has true ghost knock. Maybe the design of the motor, I'm not sure.

Ecotec no.



FU Tuning

Its knock....ive heard it.

Thats why I dont get to enjoy my car.

Philly D wrote:
On that thought......If I get the injector constant correct in theory I should be able to limp back and forth to work?

I would say no to that. If your air flow maps aren't correct, your AFR will be all over the place. The injector constant defines the flow characteristics of your injectors, it has little bearing on the amount fuel commanded.

Sparkey05 wrote:

Philly D wrote:
On that thought......If I get the injector constant correct in theory I should be able to limp back and forth to work?

I would say no to that. If your air flow maps aren't correct, your AFR will be all over the place. The injector constant defines the flow characteristics of your injectors, it has little bearing on the amount fuel commanded.

With a correct injector constant it would be safe to drive as long as you did not go wot.



FU Tuning

Yah thats cool....its stop and go and I usually cruise at about 2000-2500 rpm if that.

I dont feel I have a problem with the injector constant just all the other stuff thats confusing me...

Time to start looking for hpt.

Y3llowCav wrote:I've always wanted to learn for myself too but I just don't have the time. Then again you have way more motivation than me since I have a GREAT tuner nearby who charges fees that are beyond fair.

you son of a bitch!


04 Cav. 2dr. 5spd. My DD. 'Nuff said.

blu04DD wrote:

Y3llowCav wrote:I've always wanted to learn for myself too but I just don't have the time. Then again you have way more motivation than me since I have a GREAT tuner nearby who charges fees that are beyond fair.

you son of a bitch!

"In Oldskool we trust"

To be honest I've charged piddlesticks for some tunes and spent 10-14 hours on them... usually making all of $15 an hour once all is said and done.

You guys would be very very surprised how long a "good" tune really takes... If a tuner tells you $800 for a full out tune that's actually not as bad as you think, especially if it includes time on the rollers.

Most people do not want to pay what a tune is worth. My general rule of thumb is whatever you spend to build the engine/driveline expect about 30% more for a tune. So if you spend $3000 for a full turbo build expect it to be around $900 with dyno time all tuned. The more you spend and customize the harder and more involved a tune is.

For example, when I tune - 20% of my time is used getting the car to idle properly, cold/hot start the way I would expect any car to do so... 30-40% of my time is used to get the car to drive perfectly at LOW speeds. We're taking 5-15 mph, stop and go, parking lot and back road time... everything a driver needs every single day... those are the critical times when the car cannot fail you and bog out or stall... nobody wants to get crushed pulling out into traffic or making a left hand turn. 15 % of the time is spent on tuning while cruising around and doing daily driving to ensure at mid throttle the car is behaving the way as expected, has good response, good afr's, no knock and has proper DFCO... and then 10-15% of the time is spent on WOT dyno tuning watching Knock, AFR's, spark timing and response to tertiary mods such as meth, boost controllers, etc.

If you do a full out build and a tuner tells you they need 4 hours on the dyno for WOT pulls, you can figure out how much the rest of the tune is going to take. Everybody is so concerned about max HP and highway pulls that they forget the most important aspect of the car is the other 85% of the time you drive it. How many people do you see give up on a car because they say "The car pulled like a freight train but it was just not practical daily... bogging down and jerky and hard to start some days." That is a poor and unacceptable tune.

I'm pretty sure that anybody who has spent any significant time tuning can agree with this philosophy.

Dyno #'s are nice but if a car I tuned is un-driveable otherwise then that means I failed to give them what i promised.

-Chris-


-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...