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.
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?
I had a great time with my Cadillac STS-V this morning at True Street Motorsports in McKinney. We did a baseline dyno run on my 2008 Cadillac STS-V, then installed a Spectre custom intake for the STS-V, and ran a new dyno for before/after tests. The Spectre intake was custom ordered through Streetsideauto.
Cadillac STS-V on the Dynojet dyno
As soon as I arrived the True Street Motorsports crew got the Cadillac on the dyno and off we went.
A first casualty of the day were the batteries in my flip camera, so I switched my kodak to video mode and captured videos of the dyno runs:
True Street Motorsports uses an in-ground Dynojet dyno. A dyno reads horsepower at the wheels, after losses through the transmission and rolling losses.
One might expect an STS-V to put 360-370 hp to the wheels based on other results I have seen; my STS-V today did 356.8 whp and 350.2 ft-lb of torque, so a bit below average.
Once we had a baseline, the team started removing the intake and replacing it with the Spectre custom STS-V intake.
STS-V LC3 Engine Compartment with side covers and front cover on
This was the dirty picture from after I first removed the beauty cover to give an idea of the original intake tubing in place.
For the first run it was 92.9F 29.64 in Hg Baro, humidity 15%. By the ‘after’ runs it was 99.4F.
Spectre intake parts ready to go in
The new intake parts replaced all the factory intake from the box to the intake pipes leading around the engine.
Spectre Intake installed STS-V
The OEM intake has baffles to reduce the supercharger characteristic whine; the new intake is lighter and has no sound baffles.
OEM intake piping with baffles
With the intake installed, coolant hosing routed appropriately, and fuel trims reset, we were ready for the AFTER dyno pulls
UPDATE: replaced the ‘after’ video with higher rez combination of the two video files.
This chart shows the before/after dyno runs on a single comparison chart:
2008 STS-V Before/After dyno runs
Lots of things to consider in these results. First, I am happy with the Spectre Intake and the support from StreetSideAuto, and I had a blast at TrueStreet Motorsports, so thanks all around to everyone. I’ll be doing more dyno runs at True Street Motorsports in the future.
The results were somewhat worse than hoped — I was hoping to see +40 whp before/after and we saw +19 whp. If the 356.5 whp was 469 hp at the crank “before” (24% losses) under perfect conditions, then the after reading of 375.4 whp might equate to 493 hp at the crank “after” with only the Spectre Intake mod, or +24hp.
It was very hot here in Texas, and although the dynojet uses a correction factor to ‘standard’ conditions, that may or may not compensate adequately for the actual hp lost due to the hot air for a supercharged Cadillac.
HP vs Torque across all 4 runs exported Run Viewer
This chart is the same data done using the raw files and the dynojet viewer. Click on the image for a larger copy, then hit back to return.
Next I want to wait a couple of weeks, then rerun a ‘check’ dyno, and swap the MAF to a different lot of the same p/n MAF and retest.
