Jump to content
CaddyInfo Cadillac Forum

Tuning the Cadillac XLR


Recommended Posts


XLR-First-Tune-Stoic-IAT-ECT-4-Compariso

First tune: Move stoich to 14.4:1 due to E10 fuel, reduce ECT retard, reduce IAT retard

Result: Loss of 8 hp / 5 lb ft of torque on average

Read more: http://caddyinfo.com/wordpress/initial-tuning-steps-cadillac-lh2-v8-engine/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Tune 2:

Cadillac XLR LH2 V8 Tune 2 – slightly leaner – 2015-08-29 http://caddyinfo.com/wordpress/cadillac-xlr-lh2-v8-tune-2-slightly-richer-2015-08-29/

XLR-Tune-2-4-Comparison-SAE-unzoom.png

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

XLR-Tune3-Run1-Comparison.png

Tune 3 - 5500-6400

Cadillac XLR LH2 VVT V8 Tune 3 http://caddyinfo.com/wordpress/cadillac-xlr-lh2-vvt-v8-tune-3/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

The LH2 V8 added variable valve timing (VVT) based on the Premium V6 schema of the same time. Interestingly, the LH2 and the LC3 use the same base cam timing, which reinforces how much the LC3 Supercharged V8 in my STS-V is a supercharged 4.4L LH2. It may also give us some insights into how the LH2 VVT is programmed vs the LC3 VVT.

http://caddyinfo.com/wordpress/cadillac-northstar-lh2-4-6l-v8-vvt-tuning-hptuners-motorama/

lh2-vvt-intake-and-exhaust-cams.png

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

XLR-Tune3MAF-to-Tune4.png

There are several things you don’t want to have happen when you are tuning a car:

  • Tuning laptop crash
  • Communication / connection / gadget problems
  • Unintended tune changes
  • Changing conditions

I think I saw them all today, but here is what I think I learned.

Read more: http://caddyinfo.com/wordpress/cadillac-xlr-tune-3-maf-tuning-tune-4/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

XLR-Tune5B-to-Tune-5.png

Today’s road test is a repeat of the previous test to add to the baseline for Tune 5. The only change from previous was to decrease the TUTD shift speed by 1 mph to 81, and to change the PE ramp from 0.1 to 1.0 (range 0.01 to 2). This value effects how quickly the engine attempts to reach the PE fueling value. Since the commanded air fuel ratio is now set constant from low RPM to high, we would expect this to have impact only just after wide open throttle is reached.

Read more: http://caddyinfo.com/wordpress/cadillac-xlr-tuning-lh2-v8-tune-5b-pe-ramp/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

The default XLR programming includes 0.5 AFR richer tuning at 6000 RPM to cool the pistons. Ideally there would be a timer associated with it — say after 10 min at 6000 RPM it added — but there is not. For this tune I removed that variable in order to study the impact from 6000-6400. Since there were few other changes in the tune we are focused on the 6000-6400 RPM range.

Specific Changes in Tune 5D:

  • raise piston protection rpm to 8192
  • reduce IAT retard
  • point advance reductions around 5400 rpm to eliminate slight KR

http://caddyinfo.com/wordpress/cadillac-xlr-tuning-lh2-tune-5d-piston-protection-afr/

XLR-Tune-5D-test-1.png

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

One change for the Cadillac Northstar in the LH2 variant was the addition of variable valve timing. Today's test is a slight change in the VVT timing on the intake and exhaust to see what impact on our test results. I also restored the IAT retard at higher temps (no impact today).

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-4-6l-v8-tuning-vvt-tune-6a/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Updated with a tune that retards the intake cam at 5200 rpm and matches the exhaust cam retard exactly with intake cam retard.

See update at the bottom of blog post http://caddyinfo.com/wordpress/cadillac-xlr-lh2-4-6l-v8-tuning-vvt-tune-6a/

Retarding the intake earlier at 5200 rpm caused a hp jump from 5200-5600 rpm

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Today’s test Tune 6D was to keep the early VVT changes from Tune 6C with some late changes back from Tune 6B.

Moving back to a copy of 6B next, re-establish baseline from there, and then modify.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-tune-6d-better-is-not-always-better/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

For Tune 6E I returned to Tune 6B, except I further corrected the MAF signal in high frequency to a smoother curve.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-vvt-tune-6e-maf-adj-baseline/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Today’s Tune 6F uses the High Baro MAF calibration from 6B except from 4200-5200 rpm, where it pulls the air fuel ratio slightly (2%) richer. What I hoped to see is a very flat air fuel ratio in the NBO2s, because that’s what we are commanding in the PE (12.5 AFR or 1.176).

The test setup had another freeze ahead of the test. This time at least the XLR didn’t tilt, and after a few stop, turn the engine off, reassemble all connectors, restart the software, it started scanning again.

My prediction was that we would see the same result as Tune 6B, with better support from 4200-5200 RPM due to no fueling dip there. Overall the result was not what I expected, but then, I’ve come to expect that.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-tune-6f-mixed-maf-recal/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

XLR-Tune-6F-Compare-Calc-HP-to-VDyno-Out

The blue and red lines are the calculated torque and hp. The high yellow line is the corrected hp for atmospheric conditions. The orange and light blue lines are the virtual dyno w-torque and whp. The Green line is the Virtual Dyno line with a factor applied to move it up to the calculated hp. The green line is a smoothed line (average of averaged of values) but appears to be a good fit for the calculated hp curve. This surprises me as I was thinking that the virtual dyno and the calculated hp frequently do not follow one another based off of the detailed data.

http://caddyinfo.com/wordpress/caddyinfo-cadillac-chat-2015-09-17/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Instead of running more 6F baselines I decided to retry the early intake VVT and late exhaust retard from Tune 6C along with the other current settings from 6F. 6C was a confusing test result, as it was intuitively an improvement to 6B but tested worse. Because of the reset on Virtual Dyno, and method to correct for Humidity, and analysis that the 6B result was better than baseline for Tune 6B, (or any repetition since), I moved forward to 6G.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-tune-6g-earlier-vvt/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Data table created from the Cadillac engine dyno curve for the LH2 VVT 4.6L V8:

http://caddyinfo.com/wordpress/cadillac-lh2-engine-dyno-curve-data-table/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Added more timing, got more KR -- except interestingly near redline, so out with the low timing, most study high.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-tune-7a-timing/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

7B: pull out the KR, keep the high RPM, go to 12.8:1 tune.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-tuning-tune-7b-less-timing-low-lean/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Tune 8A commands 12.8:1 AFR from 1500-6700, where Tune 7A was at 12.5:1 AFR. The VVT in 8A has some minor cleanup in an unused area. The piston protection in 8A is at 8192; in 7A 6400 rpm. 7A was the ‘just advance the timing’ run, so 8A has 2 degrees less timing from 2300-5600 more or less, with -3 at 4200-4400.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-v8-tuning-tune-8a/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Tune 9A goes back to OEM VVT Tuning, and pulls 2 degrees of advance near redline where combined timing was above MBT. Timing elsewhere was returned to OEM. KR attack and decay were modified. Unfortunately for comparison today’s test was much warmer than yesterday’s test conditions.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-v8-tuning-tune-9a-oem-vvt-plus-less-adv-high/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Tune 9B removes IAT multipliers below 6000 RPM from Tune 9A to keep them from causing KR.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-v8-tuning-tune-9b-tuning-virtualdyno/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Tune 10a reduced the timing advance from Tune 9B across much of the range to sync up with the MBT timing in the appropriate cyl air ranges.

That was the plan at least — it turns out I didn’t account for static retard, which is a per-cylinder retard programmed in at the factory in certain RPM ranges. On average that reduced the timing at redline by almost a degree. I also halved the IAT adder multiplier from 6000-6800, so we were missing 1.6 degrees there. So instead of running 30 degrees at 6800 I ended up flatlining at 27 degrees from 6400-6800.

http://caddyinfo.com/wordpress/cadillac-xlr-lh2-v8-tuning-tune-10a-hptuners-tuning-cars/

Bruce

2023 Cadillac CT4-V Blackwing

Follow me on: Twitter Instagram Youtube

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...