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post #16 of 24 (permalink) Old 11-03-2017, 03:41 PM
racingvette
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Re: Just wondering

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Originally Posted by sdgearhe View Post
The car has only 1 mod. a CA intake. I also put in chevy dealer shop and had tune checked and updated to make sure it was stock tune.After cleaning MAF, Checked found and fixed air leak in CA intake,new plugs & wires and after sitting a few days started and ran very rough for about 20-30 sec. then ran great. I cleaned MAF again only this time I didn't care if I messed it up so I soaked it good inside and out with MAF cleaner but didn't have time to let it set before going to dealer. Dealer said after 3 days started and ran smooth. He ran his diagnostics on car and found nothing out of range.Following JR's advice I am now running Shell 93 oct. E10 gas with sea foam ( just started only about 50 mi. so far ) and cleaned air filter really good. So starting trbl. seams to be OK but still running rich by my scanner. Will post what happens after driving awhile.
buy the way corvette guy at Dealer said all is within normal operating range and I may be trying to fix something that is not broke
Thanks for taking time to read and your advice Steve
Steve I had the tuner email the recording data he was nice enough to look at for you as a favor to me and your doing a right path with the changes he told you to do and as he requested a drive with scanner recording now with and without E10 gas and see what the fuel trims are now like. Would take some driving before the fuel trims start moving leaner.
That data as shown below cold start at 59 degrees coolant and how rich both the long and short fuel trims been running quite rich for some time and Cats working harder to convert the rich exhaust to leaner out to mufflers

Let us know what the fuel trims look like now with the E10 and can judge what to do when seeing that data.
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post #17 of 24 (permalink) Old 11-03-2017, 04:05 PM Thread Starter
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Re: Just wondering

Thanks racingvette, you and JR have been a GREAT help to me. I think the starting trbl. is OK now. don't know exactly what fixed it. It's been rainy weather here and when it clears up I will run it a 100-150 mi and send JR or you the data. Again I can't tell you how much you guys have helped.
Thanks Steve
by the way this tank of fuel is a mix about 3/8 reg. 93 oct. & about 5/8 E10. next tank may do better
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post #18 of 24 (permalink) Old 11-03-2017, 05:23 PM
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Re: Just wondering

Good to hear Steve,
Your Welcome and glad to be of some help for your Z06 problems

Get a scanner recording and email to tuner as I asked him and he said it was OK to do so
Then let us know what he sees as to your fuel trim values.
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post #19 of 24 (permalink) Old 11-03-2017, 07:44 PM
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Re: Just wondering

Steve the tuner emailed me and asked if I would attach your last scanner recording values since you did not know to do it
Even though you mixed some E10 with the non Ethanol fuel and first drive the OBD-II scanner shows the fuel trims have already coming down and close what would
be seen with E10,
Once you get through that tank and then full tank of E10 the fuel trim values should be even better.
Values seen on this drive are about what was expected where before fuel trims were -17-20 plus percent rich and now about -8% rich and that is in 56 degree weather
You could look next year summer heat what fuel trims look like and decide which fuel is good at the 2500-3000 feet elevation but since you only do street speeds
it may not be worth the high cost of non Ethanol gas at that elevation since the GM tune is slanted for E10

Later on when not worrying about GM warranty you could consider having a custom tune done to allow for the better non Ethanol gas and the performance gains of that fuel
and tune gains

Nice to see the cold start issue now gone

Suggestions were :

Put that other half of Seafoam into intake manifold while at idle, if cannot do that put in engine oil
Since the engine has been running way rich for months is take sparkplugs out, clean and re-gap them
Take front O2 sensors out and use a propane torch to heat up ONLY tips of them to burn off any carbon buildup
To limit blowby and engine reverb is next time changing engine oil to go with a bit on oil viscosity

Use lower gears to use higher RPMs ( rather then high speeds) and loads to help blow out carbon and allow PCM to learn/adjust fuel trims for all engine loads
and allow the carbon breakup from the Seaform to exhaust out.
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post #20 of 24 (permalink) Old 11-04-2017, 07:02 AM
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Quote:
Originally Posted by racingvette View Post
Quote:
Originally Posted by garrettg View Post
The CAI is causing the issue, go back to stock hardware setup or make sure the CAI is sealed properly and have the car tuned by a professional. When its tuned they can also lean out the pe some as well. Run E10 or E0 but its not going to fix a vehicles rich condition in general. The way a car adapts during closed loop ltft processing will never be corrected by fuel type change if the maf transfer model is off due to hardware changes. In a full tilt situation E0 is preferred to E10 as it has more potential energy.
Not a good response, the OP has GM warranty and a tune is out of the question for him, that is is choosing
That is like putting a band-aid on a problem and hoping that will cure the problem

You really need to go learn about Ethanol, it is far proven it reduces fuel mileage, induces lean fuel trims so much so the feds had to put out notice out to NOT use Ethanol in most other gas engines.
Have no idea why since you do not know that history or the OPs Z06, nor looked at his OBS-II scanner recordings, nor understanding the ill effects of running 17-20 % rich what the effects are to internal of some engine parts, to O2 sensors or even the fact running that rich is degrading the life of the CATS,

No valid to want to run a non Ethanol fuel that runs richer when the fuel trims are at the trigger point for rich DTCs. OP needs to get engine BACK to leaner fuel trims
BEFORE going back to non Ethanol gas and his scanner will tell him when trims are back to normal

No do I have a clue why your on engine functions like WOT when the engine would not run correctly on a COLD start only

OP is doing the right thing, correcting things found by his tuner, cleaning out the carbon from running so rich for some time,
as changes he makes using the scanner to see if the fuel trims become normal and using some E10 gas to then see what the fuel trims are like
For a car that is not raced, it barely would see issues related to fuel trims but to determine rich fuel trims he is going the right path in
doing changes, even the gas to get fuel trims correct

Your method or mindset is not correct path for a stock Z06 that GM tuned richer solely because of E10 running leaner

-----------------------------------------------------
People are up in arms over recent EPA waivers that allow but do not require up to 15 percent ethanol to be blended into gasoline as E10 is already too lean for pre 2008 vehicles .
The 15 percent blend, called E15, would be available only from blender pumps clearly labeled “Passenger vehicles only.
Use in other vehicles, engines and equipment may violate Federal law.”

Here is the EPA’s list of vehicles that should not be fueled with E15:

Motorcycles

Vehicles with heavy-duty engines, such as school buses and delivery trucks

Off-road vehicles, such as boats and snowmobiles

Engines in off-road equipment, such as lawnmowers and chainsaws

Model-year 2000 and older cars, light-duty trucks and medium-duty passenger vehicles (later changed to model-year 2007 and older)

**** Because ethanol contains one-third less energy per gallon than gasoline, adding ethanol to gasoline leans out the fuel-air mixture, possibly enough to cause damage.
Several manufacturers have said they will not honor warranties if fuels containing more than 10 percent ethanol are used.
That includes GM.
Pre 2008 vehicles including Corvettes were not designed even for E10, GM had so many customer problems that cars like the C6 had to be slanted richer,
C5s the PCM used a algorithm of what fuel trims and O2 outputs to determine gas quality

In the end the OP has been doing as his tuner proposed and that found the airbridge leak, the dirty aircleaner, the coked up valves, piston tops and lazy O2 sensors
and final test of using some E10 gas will pinpoint if start problems are gone, what the fuel trims are now and then can go back to fuel he wants that work on a
stock engine under GM warranty.

A tune setup for using non Ethanol gas would have the most performance benefit but only when owner wants to go that route, and lastly learn about elevation, density and the grades of gas sold in higher elevation
The mindset is correct remove the hardware in this case cai and go from there if tuning is not an option. E10 is not going to solve an overly rich situation in a car that runs in closed loop. If the car only ran open loop then that is another story. If this guy fixed his car it's because the cai is now sealed or installed correctly.
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post #21 of 24 (permalink) Old 11-04-2017, 07:04 AM
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Quote:
Originally Posted by racingvette View Post
Steve the tuner emailed me and asked if I would attach your last scanner recording values since you did not know to do it
Even though you mixed some E10 with the non Ethanol fuel and first drive the OBD-II scanner shows the fuel trims have already coming down and close what would
be seen with E10,
Once you get through that tank and then full tank of E10 the fuel trim values should be even better.
Values seen on this drive are about what was expected where before fuel trims were -17-20 plus percent rich and now about -8% rich and that is in 56 degree weather
You could look next year summer heat what fuel trims look like and decide which fuel is good at the 2500-3000 feet elevation but since you only do street speeds
it may not be worth the high cost of non Ethanol gas at that elevation since the GM tune is slanted for E10

Later on when not worrying about GM warranty you could consider having a custom tune done to allow for the better non Ethanol gas and the performance gains of that fuel
and tune gains

Nice to see the cold start issue now gone

Suggestions were :

Put that other half of Seafoam into intake manifold while at idle, if cannot do that put in engine oil
Since the engine has been running way rich for months is take sparkplugs out, clean and re-gap them
Take front O2 sensors out and use a propane torch to heat up ONLY tips of them to burn off any carbon buildup
To limit blowby and engine reverb is next time changing engine oil to go with a bit on oil viscosity

Use lower gears to use higher RPMs ( rather then high speeds) and loads to help blow out carbon and allow PCM to learn/adjust fuel trims for all engine loads
and allow the carbon breakup from the Seaform to exhaust out.
If the vehicle is seeing -17 to -20 ltft then its either been tuned already or something mechanically is wrong. A stock GM tune will not be this far off regardless of E10 or E0 being used. A stock tune with a properly installed CAI should also not be causing drastic negative ltft either. A CAI assuming it actually works and didn't make air flow worse should flip the ltft to the positive side if anything. The simplest thing to do is validate the CAI is installed correctly or re-install the stock air filter. There are ways to identify if the vehicle has been tuned. If its a manual and the cags isn't being enforced and there is no local bypass hooked to transmission then its been tuned. Another easy way is to state at what temp the fan turns on while the car is stationary. Anyone here can validate if that fan temp is stock or not. Another way is to have someone with hptuners or similar pull the tune and compare to stock file. A car with that far negative ltft has either been tuned already or has a mechanical issue. There are many corvettes out there being driven by owners that don't know their vehicle has been tuned.

Last edited by garrettg; 11-06-2017 at 09:39 AM.
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post #22 of 24 (permalink) Old 11-13-2017, 03:01 PM Thread Starter
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Re: Just wondering

racingvette, Steve here, It seems my starting trouble ( rough idle ) is gone and I don't know what fixed it. Also since using E10 gas it seems the fuel trims are down to normal. Here in Va. the temp also came way down anyway I thank you and Tuner for all the help.
Steve
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post #23 of 24 (permalink) Old 11-13-2017, 08:08 PM
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Re: Just wondering

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Originally Posted by sdgearhe View Post
racingvette, Steve here, It seems my starting trouble ( rough idle ) is gone and I don't know what fixed it. Also since using E10 gas it seems the fuel trims are down to normal. Here in Va. the temp also came way down anyway I thank you and Tuner for all the help.
Steve
Steve it has been a few weeks since you did the cleanup and using E10 as suggested and being you also say once using E10 the fuel trims leaned out
I think you did the right thing and problem is gone

Stay with the E10, cold weather, you do not race, street driving, you do not need to spend the extra money for non Ethanol gas as GM tune is not slanted for that
Once weather gets hot check the fuel trims and decide if then it is worth non Ethanol fuel or have the PCM tuned for that gas if that is what you want to use.

Good job you did much better then the dealer having the car for multi days and not finding the problem but if they did as you did and saw the -17-20 % rich fuel trims
they would then zoom into that.
Keep using your OBD-II scanner, you will learn more and have the experience in using it.

Have fun with with your C6 Z06

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post #24 of 24 (permalink) Old 04-12-2018, 11:39 AM
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Re: Just wondering

That recommendation was probably made because E10 will lean the car out a bit. Stoichiometric AFR for E0 is about 14.7:1 and stoichiometric AFR for E10 is around 14.1.

Therefore your ratio is 14.1/14.7 so you would lean the mixture out across the board by about 4%.

Be careful though because if your running rich everywhere besides wide open throttle then you could run a hair lean at WOT after making the change. The car needs to be tuned correctly.
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