Cadillac XLR LH2 V8 Tuning – Tune 10B MBT

Tune 10B uses MBT values, adjusted for static retard and VVT adders, as the main spark table.  MBT, or minimal timing for best torque, is a table that shows Cadillac’s calculated ideal timing.  Often it cannot be reached without knock.

XLR Tune 10B Comparisons

The results look very good — 327/313 for one run, 323/309 corrected 2nd gear HP/Torque for the other.

XLR Tune 10B VirtualDyno Comparison

The virtual dyno results for the same two runs were similar — 269/256 and 263/252 which divided by 0.8 for automatic losses would be 336/315 and 329/315 Hp/Torque.

XLR Tune 10B-0457

There was some slight KR in one run, although it did not repeat in the other run.

XLR Tune 10B-0747

All in all I am happy with 10B and will keep gathering more data on this tune to see where to go from here.



Cadillac XLR LH2 V8 Tuning – Tune 10a #HPTuners #Tuning #Cars

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.

Overall Tune 10 was a good result, in that it continued to show no KR and showed that we can get equivalent results with less timing, which leads to locking our KR.

XLR Tune 10a-1 Calc Hp and timing discussion

The dark blue and red lines are hp and torque on the left axis; the other lines are test result advance, test result KR (green at bottom), MBT advance (goal timing in maroon), and Tune 10B advance planning in light blue.

I was missing a degree of advance til 6000 then around 3 degrees by 6700.

XLR Tune 10a Virtual Dyno Comparison

The Virtual Dyno runs were in a range, at 264, 266, 271, 274 whp.  The red line at 266 whp is for the same calculated data in the first graph; 266 whp / 0.8 trans losses = ~332.5 hp.

XLR tune 10 timing planning

This is my worksheet to consider the MBT timing based on the cyl air pressure ranges, what the engine is currently doing in the test, and what I would like it to do in the next tune 10B.

XLR tune 10a hptuners gauges

The HPTuners graph suggests that power was increasing in step with timing advance until the timing went flat at 27 degrees at 6400 rpm.  I am hoping that if the timing continues up to 30 degrees at 6800 rpm as suggested in the MBT table then we will see an increase in power above 6400 rpm.

Suggestions, corrections, or discussion welcome — hit the comments!


#Cadillac XLR LH2 V8 Tuning – Tune 9B #Tuning #VirtualDyno

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

XLR Tune 9B and design for tune 10

Tune 9B tests ran almost no KR, so removing the IAT adders helped there.  The totals were good at 317-320 2nd gear HP.

XLR Tune 9B VirtualDyno with 9A

Both 9B runs were pretty wavey but overall 9B made at least as much WHP as 9A.

In the first graph it is clear that Tune 9B is running MORE timing than the MBT table.  For Tune 10 I am zeroing out PE/COT timing adder and touching up the base timing to pull timing down to the MBT timing shown in gold.