Tuning Experts.....Pls Chime In!

[Ellis]

Finally giving in to asking about my knock retard. I have been in search of resolving this issue for about three months; so syty tuning gurus; please feel free to chime in. It's a stock rebuild on a 93' motor. It currently has about 1000 miles on the rebuilt engine. On the rebuild, I replaced all caps, rotors, plugs, wires and had the stock injectors cleaned and flow matched. It has a Waller turbo, ATR cam, roller rockers, AFPR and a 255L Walbro fuel pump, ATR Pitbull Chip and a 160 degree thermostat. Fuel pressure is set at about 44 psi.

I have been monitoring my knock retard on datamaster and have never been able to go WOT. I am currently registering knock at about 8-10 lbs of boost. My knock retard is generally in the range of of about 5-8 under those conditions. In an effort to try an resolve my knock issue, I have pulled and changed the plugs several times. The most recent check of them revealed they were tan in color.

Here's my input based upon significant datamaster values. Upon idle my engine temperature is about 176 degrees, spark advance at idle is at 23.9, IA Temp is at ranges between 125 - 135 degrees, short term values are at about 112 and my long term values are at about 124, AFR is 14.7

Changes under throttle..............my engine temperature lately has been starting to rise upwards to about 195 degrees (might be a fan clutch problem), my spark advance I have seen drop as low as 3.9, my AFR has never dropped below 13.0 regardless of the amount of boost and I very seldom see my O2 values in the 900 range unless I'm decelerating. So tell gurus; what do you initially think is going on. My AFR value leads me to think it's a chip problem surrounding the lack of fuel.

 

[JSM]

Re: Tuning Experts.....Pls Chime In!

Here's my input based upon significant datamaster values. Upon idle my engine temperature is about 176 degrees, spark advance at idle is at 23.9, IA Temp is at ranges between 125 - 135 degrees, short term values are at about 112 and my long term values are at about 124, AFR is 14.7

Changes under throttle..............my engine temperature lately has been starting to rise upwards to about 195 degrees (might be a fan clutch problem), my spark advance I have seen drop as low as 3.9, my AFR has never dropped below 13.0 regardless of the amount of boost and I very seldom see my O2 values in the 900 range unless I'm decelerating. So tell gurus; what do you initially think is going on. My AFR value leads me to think it's a chip problem surrounding the lack of fuel.

Where are you getting your AFR values from, datamaster or do you have a wideband installed?

The 124 says its a tad lean at cruise/idle and pulling fuel. It tells us nothing of fueling under boost though. You mentioned the 14.7 at top, in closed loop the ECM will find 14.7, in your case by pulling 4 pts from the long term counts to bring it back to 14.7. ECM is doing what it is told. Under boost though ST and LT counts mean nothing really.

 

[Ellis]

Re: Tuning Experts.....Pls Chime In!

Where are you getting your AFR values from, datamaster or do you have a wideband installed?


...datamaster!

 

[Ellis]

Re: Tuning Experts.....Pls Chime In!

Where are you getting your AFR values from, datamaster or do you have a wideband installed?

The 124 says its a tad lean at cruise/idle and pulling fuel. It tells us nothing of fueling under boost though. You mentioned the 14.7 at top, in closed loop the ECM will find 14.7, in your case by pulling 4 pts from the long term counts to bring it back to 14.7. ECM is doing what it is told. Under boost though ST and LT counts mean nothing really.

Now I always understood the value of 128 as being equal to zero and if it falls under that value; fuel is being taken away and if it is above that value, fuel is being added in and effort to compensate. So if it is at 124 is fueling rich or lean?

Reading the last datamaster file; fueling values under boost are Long term dropping to 116 and Short term increasing to about 152 under 12.5 lbs of boost.

 

[JSM]

Re: Tuning Experts.....Pls Chime In!

datamaster AFR values have as much value as the pontiac production line does right about now.

So may reasons you could get knock, its something your going to have to work through. Install a true WB AFR can be a big help though.

 

[turbodig]

Re: Tuning Experts.....Pls Chime In!

Now I always understood the value of 128 as being equal to zero and if it falls under that value; fuel is being taken away and if it is above that value, fuel is being added in and effort to compensate. So if it is at 124 is fueling rich or lean?

Reading the last datamaster file; fueling values under boost are Long term dropping to 116 and Short term increasing to about 152 under 12.5 lbs of boost.

<128 Fuel reading is rich, fuel is being pulled. >128 fuel is lean, fuel is being added.

The stock o2 sensor is of really limited value in tuning. At WOT, it's of pretty much no value at all.

I can tell you this much - the chip you have doesn't match your build even remotely. It's likely very lean in places, and/or delivering the wrong timing.

You'll need someone to do a custom chip for you, or do one yourself (code59.org). This doesn't preclude any mechanical issues, but having a better calibration would be a good start.

 

[Ellis]

Re: Tuning Experts.....Pls Chime In!

<128 Fuel reading is rich, fuel is being pulled. >128 fuel is lean, fuel is being added.

The stock o2 sensor is of really limited value in tuning. At WOT, it's of pretty much no value at all.

I can tell you this much - the chip you have doesn't match your build even remotely. It's likely very lean in places, and/or delivering the wrong timing.

You'll need someone to do a custom chip for you, or do one yourself (code59.org). This doesn't preclude any mechanical issues, but having a better calibration would be a good start.

Turbodig; I guess I was slowly and unwittingly getting to your assessment. I did buy some chip burning equipment a while back so I guess it's on to Chip Burning 101 class for the next couple of months unless someone thinks they have a chip suited for my build that I might be interested in.

Thanks guys for looking and for your current and future comments!!!!!

 

[Ellis]

Re: Tuning Experts.....Pls Chime In!

....so; just to see if it would make a difference, I replaced the pitbull chip from atr with the original stock one. As a result; my knock retard decreased significantly. If I had to put my finger on a couple of changes in the data; I would say that under boost (in the 12 - 15 range) my AFR values dropped from 13.0 to 11.7, 11.6. My Spark Advance remained in the double digit numbers instead of dropping down in the single digits (this is probably due to the lack of Spark Retard).

In fact in one of my runs just shortly after starting and going into closed loop; I was able to build boost up to 14.8 lbs with no Spark Retard. Does anyone know what were the significant differences in the ATR Pitbull Chip and the Stock Chip? I think if I am going to eventually do a custom chip; starting with the Stock one might be the way to go.......thanks in advance!!!!

 

[UR50SLO]

Re: Tuning Experts.....Pls Chime In!

I don't think you read the part in the above post from Jeff... DO NOT RELY on the datamaster AFR Reading. It is not remotely close to correct.
Purchase a real wideband and then rely on those numbers.

Code 59 is a great way to get a truck tuned for changes you've made and will make later. It allows you unlimited access to SES light disable for annoying codes (EGR ect) and you can taylor fuel and timing to your truck's needs as needed.
You can watch the narrowband 02's at WOT but again.. they are not real reliable above or below .500mv.

Definatly resolve the fan issue. with a 160t-stat it shouldn't be hitting 195.
~Scott

 

[JSM]

Re: Tuning Experts.....Pls Chime In!

Here is why a narrowband sensor is useless for anybody aside from 14.7

If you look it is a switch, above 14.7 you will see 100mV or so, below it jumps to 800+mV.

Now lets assume your truck under boost wants to run at 11.8 AFR. With a brand new sensor that is PERFECT you will see according to chart maybe 990-1000mV, but the truck is actually running at 13.2 AFR (which would be lean under boost). 13.2 would show maybe 970mV according to chart?

970 vs 990 you would think hey I am close when your really not at all. And these numbers are with a perfect sensor.

Now if you look you will also see as the temperature of the sensor changes the output does also. Now you really have data that is useless unless you also know the temp of the sensor at the instant the sample was taken.

Now look at a wideband.

the voltage swing is 0-5v, not just 0-1v. So resolution is already 5 times more.

The output is also linear. Now 13.2 would be 1.5volts and 11.8 would be .9volts We can also predict the output via a very simple formula. This formula happens to be programmed into code59 when it reads an aftermarket WB.

The AFR ready datamaster shows with a stock chip/o2 sensor is nothing from the sensor itself but more part of some math the ecm is doing to figure out how much fuel you need/want. It is not a direct reading an any way.

 

[WyoSyclone]

Re: Tuning Experts.....Pls Chime In!

Definatly resolve the fan issue. with a 160t-stat it shouldn't be hitting 195.

This (160 t-stat) kind of falls into that urban myth category.
Once the thermo opens, coolant temp is governed by the effectiveness of the radiator (and fan when needed). The 160 degree mark is simply the point at which the system begins cycling coolant through the radiator - the T-stat can't bring the temp back down.
Normal engine operating temp is 85 to 95 degrees C (183 to 202 degrees F). Engine temp should steadily rise to about 195 degrees F, then stabilize (160 T-stat will cause engine to warm up more slowly. Stock 188 thermo will allow engine to come up to temp more quickly).
A high temp coolant light will be set when the coolant temp reaches 270 degrees F for 3 seconds, or longer (according to the manual). The boiling point of the coolant is ~257f with our recommended 15psi radiator caps - at this point the cap vents expanded coolant into the overflow tank.
IIRC, the fan clutch engages at approximately 200 degrees f.

Hope this helps..... 195 temp is OK. Somebody please slap me if I've spewed poor information!

 

[UR50SLO]

Re: Tuning Experts.....Pls Chime In!

This (160 t-stat) kind of falls into that urban myth category.

:chair: Ok.. I could not find a slap smiley.. Lol..

The newer engines are designed to operate at higher temps for emmissions. The higher temps decrease power over all and limit timing and promote detonation in our trucks/performance cars.

IF you have a good operating coolant system that is properly sized for your engine it will maintain 160degrees. My Camaro for example with stock radiator 160T-stat stays between 159-164degrees...even on a low 10second pass!!!! It'll go up 2-3degrees.

The wife's 98Turbo Jimmy has a 180T-stat and stays right around 180.

With a weak fan or improper coolant system ect (Problems) I agree that regardless of how low of a T-Stat you install it will not keep the cooling system any "Cooler" It just delays the inevetable overheating since there's somthing wrong.
~Scott