Tag Archives: HpTuners

Updated Baseline Cadillac STS-V 0-60 time

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This morning it was a fresh 91F out, so I ran some new baselines for the STS-V.  Just tickling the 5 sec line at 91F.

Weather: 91.4F; Baro 29.12 Hg. (14.3 psi); Humidity 10%.  Fuel: half-tank.  Altitude: 600 feet above sea level.

My Cadillac is a 2008 STS-V with a Spectre Intake.  This is a 4,233 lb sports luxury V-Series sedan with a 4.4L supercharged & intercooled V8.

Today in hot weather it ran a 0-60 time of 5.42 sec (0 feet-5,280 feet), or 4.98 sec including 1 foot of rollout as at a dragstrip, (1 foot-5280 feet).

The 60′ time for this run was 2.3 sec.

Previous measured times for my STS-V with me driving were 5.39 sec w/rollout and 5.29 sec w/rollout, so today’s time of 4.98 sec w/rollout is an improvement of 0.3 sec.  Between the runs I have changed the tires, added the Spectre intake, and changed the MAF.  Side by side, today’s run would have been 17 feet ahead of the previous run at 60 mph.

w/rollout
Speed(mph) Time 0.44 Dist(f)
10 1.01 0.57 6
20 1.75 1.31 23
30 2.46 2.02 49
40 3.31 2.87 93
50 4.30 3.86 159
60 5.42 4.98 248

Here is the graph:

Here is a view from HPTuners of the peak near 60 mph for this run showing that I am getting -3.2 degrees of advance due to the ambient and IAT2 / MAT temps at this point; it heads as low as -4 degrees.

IAT Advance at -3.6 degrees

I believe that because the boost is calculated from Manifold pressure and barometric pressure, that it reflects boost after the pressure drop across the Laminova intercooler tubes.  So some pressure going in, 9.4 psi getting to the engine in this snapshot.

Here was a video of the HP Tuner scan of the 0-60 run:

I captured a second run at 5.45 sec w/o rollout or 5.08 sec from 1 foot.

w/rollout
Speed(mph) Time 0.37 Dist(f)
10 1.06 0.69 6.2
20 1.87 1.50 22.58
30 2.61 2.24 48.61
40 3.41 3.04 92.88
50 4.38 4.01 158.55
60 5.45 5.08 248.34

My rollout is still a bit high — taking too long to get from 0-1 foot.  I would like to see rollout around 0.3 sec.

Summary

Today’s run shows a clear improvement from the previous mark.  I would like to see under 5 sec without rollout considered.

The IAT Advance is pulling timing from the engine based on the incoming air temp out of the supercharger.  Either running the car in cooler weather (!) or improving the intercooler cooling perhaps would help.  This is with the stock calibration; it may be possible to simply adjust the tune to be somewhat less aggressive on IAT Advance.  Adjusting shift times and possibly RPM may also reduce 0-60 times.

Cadillac Video HPTuners Dashboard playback showing IAT2 trends

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Here is a short video capture of an HPTuners VCM Scanner output of a test run to monitor intake air temperatures through the MAF (IAT1) versus after the intercooler (IAT2) or ambient.

The source video was over 1080 pixels but Youtube offers it for viewing in up to 1080p so please select the highest resolution your playback can handle and hit the fullscreen gadget for the video then pop back and comment.

I am still synthesizing the data.  It appears to me that as the STS-V accelerates the IAT2 temp rises from 131F to 151F the slowly drops down again.

There is some Knock retard coming in at high RPM.  The V will also pull timing at higher IAT2 temps.

Let me know what you think about the run data and this method of reviewing it.

Monitoring IAT, IAT2 Cadillac STS-V

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This morning I did some data-logging with HPTuners up and down the highway.  I am still learning the software, so feel free to make suggestions.

I grabbed these screen shots of a couple of points: (click on the image for a zoom-in version, then hit back to come back):

HPTuners datalog screenshot 1

What the first screenshot shows is that at 69 mph and 6651 RPM the supercharger was making 10.7 psi.  During this portion of the run, ambient air temperature was 90F, IAT air coming into the MAF temperature sensor was 108F, and IAT2 air leaving the intercooler was at 151F.

Actually I would have expected the car to shift at 6500 rpm, but 6651 is close enough I suppose.

In the chart display at the bottom however, you can see that the IAT2 was already elevated before the higher-RPM event occurs.

The question for today though is how the IAT2 151F compares with ambient air 90F.  The Supercharger adds heat to the intake air in the process of compressing it.  At maximum RPM as here, the Supercharger is spinning at 2.1:1 and so 13,967 rpm.   This can add up to 200F to the air coming into the intercooler.   Today the air coming in to the supercharger was already 108F, so heating it by a couple hundred degrees puts some very hot air across the Laminova intercooler tubes. The goal for the Intercooler is to reduce the heated air back as close to ambient air as possible, pulling the air back from 200F+ down to 151F in this example.  The unachievable ideal is that the intercooler get the air down to the intercooler heat exchanger’s own cooling source, which is the ambient air coming into the front grill at 90F.

HP Tuners datalog screen shot 2

In the second screen shot, at 39 mph and 6502 rpm, ambient air was 88F, MAF intake air 108F, and IAT2 after the supercharger was 135F.

On a separate topic, long term fuel trims appear to be small, which I think is good.

Points to ponder:

How to reduce the IAT2 temperatures from 151F when accelerating at highway speeds

Why the max pressure seen was 10.7 psi instead of 12 psi?  Is this also temperature related?

How will these readings change in cool air?