cal30_sniper

iTrader: (16)

Hey Fellas,

About to burn off my first chip. I've been working on it for about a week now, and I think it's ready. I'd like someone who knows what they're doing to confirm what I have done so far is correct. The vehicle is a bone-stock 1988 GTA, L98, running premium fuel only. Here's what I want to accomplish right now:

-Disable VATS
-Disable EGR
-Disable AIR
-Lower Cooling Fan Temps
-Cut fuel above 6500 RPM to protect from overreving in preparation for the 6-speed swap
-Ramp up the factory spark advance tables

I used the ABWT88ta.bin file from Moates as my baseline. Using that bin, I made the following modifications in Tunercat:
-Matched MAF Tables to each other (first and last values)
-Deselected EGR Diagnostic Switch (Err 32)
-Deselected VATS Diagnostic Switch (Err 46)
-Set Fuel Cutoff Constant to 6503 RPM
-Set Fuel Resume Constant to 6211 RPM
-Set Both Fan On-Points to 88C (190F)
-Set Both Fan Off-Points to 85C (185F)
-Set Min MAT to Enable EGR to 150C (302F)
-Set AIR Control Enable Coolant Temperature to 150C (302F)
-Averaged High Values in Main Spark Table between ABWT88TA and ARAP bins
-Pulled Spark 4-8 degrees above 92C (198F)
-Raised Maximum Spark Advance to 43.6 degrees

In order to build the spark advance table, I used both the ABWT and ARAP spark advance table. In the RPM/Load range where the ABWT was higher, I left it alone. In any location where the ARAP value was higher, I averaged the value from the ABWT and ARAP and plugged that in. Also, due to the lower fan temps and to help prevent pinging down here in these hot Texas summers, I pulled 4-8 degrees of timing in the Cool. Comp. Spark Adv. Vs. RPM Vs. Cool. Temp table. I figured this was a good safety measure until I get some good datalogging in case she gets warm with the increased spark advance.

This was the original spark advance table:


Here's my new spark advance table:


Here's the ARAP Spark Advance Table:


Here's the Coolant Spark Compensation Table after I modified it:





Somebody please give these a once over and make certain that I haven't royally screwed something up. I've taken many classes and labs on internal combustion engines, and I'm very familiar with timing and fueling theory (We ran an LT1 in the lab for literally hundreds of hours playing with stuff). I've also spent years doing mechanical and vacuum timing advance on carbureted cars. I've just never burnt a chip or messed with an auto computer before, so I'd like someone to take a gander and help keep me out of trouble.

Thanks guys,

-cal30sniper

RBob

iTrader: (1)

In the f-body's only one fan is ECM controlled. The other is controlled by the A/C system(?) and head temperature switch. In any case should stagger the temperatures a little so that they don't both turn on at the same time.

> Raised Maximum Spark Advance to 43.6 degrees

This needs to be set back to the stock value. It is a limitation of the distributor. It isn't the actual maximum amount of timing allowed. It is the maximum amount of advance that can be programmed into the distributor.

With the proper value of 42*, and the initial at 6*, a maximum at-crankshaft advance of 48* is available.

Note that ARAP was used on an aluminum headed 5.7l L98. And is on the aggressive side even for that engine.

RBob.

cal30_sniper

iTrader: (16)

RBob,

Thanks for the explanation on the distributor, I did not know that. Makes perfect sense though.

I should have been clearer on the fans. In Tunercat, there is a constant for the fan turn on with the A/C on, and a constant for the fan turn on with the A/C off. I set both of these constants to the same value, 88C and 85C in order to work with my 180 degree thermostat. I may get the lower temperature cylinder head switch to turn the second fan on at 200 degrees or so, I will just have to see how it goes next summer.

I had read that the ARAP was pretty aggressive, but some out there are running it on iron headed engines with premium fuel and not having to pull too much spark. The factory ABWT bin is set up to run with 87 octane. My reasoning is, as long as I run premium fuel, I should be able to split the difference between the two without a problem. Should boost midrange torque and gas mileage a considerable amount. I realize that the mileage increase will be cancelled out by the increased price of premium fuel, but that's what I run anyways. After the third or fourth tank of bad 87 octane I got around here, I switched to 93. Haven't had a problem since.

I won't throw in the chip until I get a chance to datalog it at the same time. I'm also going to use the HRD1 to read my factory chip once I get it out of the car and see what it's spark tables look like compared to the ABWT. May just decide to work off of that chip and bump up the timing. We'll see.

Thanks for the help,

-cal30sniper

RBob

iTrader: (1)

Gotcha' on the fan temperatures. I didn't even look at the calibration to see if it was set up for two separate fans. Have you considered moving to the '89 $6E code? It has a lean cruise highway mode in it. Will need to disconnect the connector for the CSI.

Once you start tuning see how far off the MAF tables are. Many here have posted that the MAF tables & scalars in ARAP are much closer and they run better.

RBob.

cal30_sniper

iTrader: (16)

I considered it, and I may do it in the new future. Disabling VATS is my main priority right now, the rest is just playing around with it. Other than burning a chip with $6E code on it and plugging the cold start injector, is there anything else that needs to be done to switch to the $6E code? If I'm reading the code correctly, $32 has a highway mode for spark control, but not enleanment. So the $6E code will enlean for highway mode as well. That's something to look into.

Well check on the MAF Tables when I get this chip burned. I also got ahold of the AKXY chip for an '88 L98. Looks like the ABWT was an '87 chip. Only differences I could find were a WOT spark advance in the '88 Chip, as well as a lot of timing pulled under low load conditions. Overall, the 87 Chip appears to have more aggressive spark advance. Why would they pull timing at low load levels for '88?

-cal30sniper

RBob

iTrader: (1)

Odds are it was done for emissions. Less SA equals lower HC & NOX. IIRC, the MAF cars don't have separate calibrations for Cali & FED. Don't recall where I got that from, but it would also explain the lower spark advance.

Which is also why in California emissions testing the base distributor timing checked.

RBob.

cal30_sniper

iTrader: (16)

I was suspecting it had something to do with NOX emissions. Earlier spark equals higher combustion chamber temperature and pressure, which means a greater chance for NOX to form.

Turns out the '88 bin actually did have a bit more timing at WOT. I was forgetting to add in the WOT Spark advance table in the '88. In the ABWT Bin, there is no WOT Spark Advance. In the AKXY bin, there is a separate table for WOT Advance that adds anywhere from 2-8 degrees of timing depending on RPM.

Am I correct in assuming that since WOT is 70% or greater TPS reading, and the max LV8 is 208, that Wide Open Throttle Timing Advance starts at 70% of LV8, or an LV8 of 145.6? When combining the two tables, should I just add the WOT Spark Advance table to the the main S/A table for LV8 levels of 144, 160, 176, 192, and 208? Or would 144 not be included since it is technically slightly below the 70% value of 208?

Thanks, I think I'm going to have a pretty good baseline to start with here...

-cal30sniper

camaro1185

Very good information here. I have been doing the same as you and fine tuning a stock 88 L98 just to get proficient at tuning before I build my motor. It must be an engineer thing....

cal30_sniper

iTrader: (16)

I reckon so. Like I said, I took several semesters of internal combustion theory and applications, and from what I learned, AFR and Spark Advance control almost everything as far as efficiency and power are concerned. I have a feeling that these engines had some very silly things done from the factory in both departments in order to help combat emissions. I've messed with mechanical/vacuum advance and jetting carbs for years. Still, as an engineer, it's nice to be able to look at things in tables and fine tweak to my hearts content. Hopefully it turns out as good in real life as it looks on paper.

For the benefit of those interested, I'm attaching my latest spark advance iteration. It's based off of the spark table that I posted in the first post, but has the WOT spark advance from the AKXY bin added in at 144+ LV8 levels. I'll also show the ABWT and AKXY tables for comparison. If anyone knows what the WOT spark advances for the ARAP bin are, I'd like to see those so I can finish filling it out as well.

Current Iteration:


The Factory ABWT Curve:


The Factory AKXY Curve (w/ WOT S/A added in)


The following chart is a combination of the two above charts. For every point in the table, I take the highest value between the ABWT and AKXY + WOT S/A table. This results in a "maximized advance factory table" between the two years:


ARAP Factory Timing (W/out WOT S/A Table)


Hope this helps visualize what I'm trying to do here. Might even help somebody else trying to do the same thing.

-cal30sniper

cal30_sniper

iTrader: (16)

Just a quick update, I've been tuning and datalogging all week now. So far, I've got the spark tables ironed out about perfect. I had to take some timing out in a few places to avoid spark retard, but all those spots have disappeared now.

For those interested, here is the finalized spark table: (Please note, this is only for PREMIUM FUEL. I'm running 93 octane)


Here's the best 3rd gear datamaster dynochart that I pulled up. I used the same parameters across all of the different tunes that I datalogged. These parameters gave an average of 232 hp during 3rd gear pulls with the factory tune. The spark table above with the factory MAF tables was good for an average of 263 hp during 3rd gear pulls. After adding in the ARAP MAF tables and playing with them a bit, I gained the final tune shown below. This tune average 278hp during 3rd gear pulls, with the best shown below:


Pretty pleased with the work so far. Now I get to see how gas mileage has improved. Next step, switching to $6E code to get the highway mode.

-cal30sniper

88WS-6

Nice job. I'm really thinking of diving into this type of programming if I'm able to fix my motor. Make sure you at least save a copy of that tune.

310cid

iTrader: (1)

I know this is a old post but what happened to all the pictures ?

RBob

iTrader: (1)

They were hosted on ImageShack, I guess either his account expired or the images were deleted. You can see the links in his post when you quote it.

RBob.

310cid

iTrader: (1)

hmm they come up blank squares. It must have been taken down like you said. Thanks

cal30_sniper

iTrader: (16)

They were lost in the great internet imageshack dump. Those things happen in six year old topics.