[Sean's Jaguar XJS Tech Pages]
Sounds Jaguars Make

Last modified 2005 APR 07 04:40:22 GMT

Okay, so there isn't much here right now - that's not for a lack of interest in collecting up some material to post here, but rather time and of course that I'm not experiencing anything that generates odd noises just yet. I hope to collect up some other sounds - transmission, differential, steering, fuel pump, bearings, injectors, the "thump" over a pothole sound, misfire (both in the engine compartment and the sound of the "$100 bill" over the exaust pipes test as well). There's a lot of sounds which could be recorded - what I'd like to do is provide some which help diagnose certain known failures.

If you have sounds to wish to share, PLEASE don't just email them to me. Contact me via email and indicate what sounds you have and their relative quality (mine are digitally recorded - straight from a digital video camera, so there's no static and hiss to detract from the sound). These need to pertain to the Jaguar XJ-S and Jaguar V-12 engine - general automotive sounds are nifty, but are not the focus of this project.

These files are in MP3 format -- you'll need an MP3 player such as WinAMP to play them. If you want to copy a file to listen to it over and over and over again, you're welcome to do that, but please right click it and SAVE IT TO YOUR COMPUTER rather than just downloading it a bunch from here. HREF abusers - people schlepping the files to be served from here, but played from their own sites - will be dealt with harshly. Please respect copyright.

The sounds currently offered here were all recorded from my 1985 XJ-S project car, which needs a lot of attention to put it right. The engine compartment is appreciably more noisy than my 1988.

An attempt to start an HE V12 with a bad ignition amplifier -- you hear it want to almost start, but it's just not getting good spark. This same engine will turn over just fine by swapping out the AB14 ignition amplifier box with a good one.
If you inadvertently disconnect the coolant temperature sensor (on the front of the B bank), or if it has gone "open circuit" (possibly after it has run warm), this is what starting will sound like. Note the subtle difference between this and the above sound -- there's no "almost fired" sound here, because there's no fuel being injected to be ignited. Note that you could get the same sound with no fuel and/or a dead fuel pump - but presumably you'd have excluded these possibilities first.
This ignition amplifier is marginal.
This is the same marginal ignition amplifier. Note that it seems to start and idle fine, but as throttle is applied, it stumbles. Notably, it runs nicer when the engine is unloaded (in neutral gear), but when you put it in gear and apply throttle (towards the end of the recording, after the 1 minute mark), the car doesn't really want to go. The recording has several "rev ups" - where I apply light throttle (only to about 2000 rpm or so), demonstrating how sometimes, but not always, rather than revving up, it stumbles. Note that this was recorded with the microphone right next to the wiper grille, whereas the above sounds were recorded with the mic on the roof of the passenger cabin, where it is obviously preferrable to capture from.
Tony Parran, owner of a 1984 XJ12, provided the audio for this sound. The racket given off by a starter with what his repair shop called "a broken brake assembly within the starter unit, used to decellerate the starter once it has been disengaged." Unfortunatley, there is no such thing - chances are, this is actually a bum Bendix.

Technical information for the curious

I use a Sony DCR-TRV310 Digital-8 Handicam. This is an early generation digital video camera - I'd love to have a newer generation semi-pro one, but this one suits my needs and I cannot justify the cost of the upgraded model I'd like to switch to (and by the time I can, it'll be a totally different model anyway). This camera stores video and sound digitally -- I transfer this data from the camera to the PC via Firewire (IEEE-1394), which means it remains in digital format in moving it into the PC (versus inputting it through the analog inputs on a sound card). Once in the PC, I crop the audio channel to the portion of interest and save a 16bit stereo 44.1K sample to disk as a standard WAV file. I then bring the WAV file into a WAV->MP3 encoder and generate a MONO (stereo separation being unimportant to the sound samples in question) file at a reduced sample rate (which doesn't really detract from the sound quality). None of this is rocket science, and it isn't Pro-grade (nor do I make any claims that it approaches it), but it results in a good quality sound sample.

Someone asked if I use external mics on the camera -- no, while I do have a couple of lapel mics (not used for the current samples), I don't currently use a stereo separated mic pair. I have considered producing tube and stethoscope mic attachments so that I can use the camera to record "remote" sounds - either injectors, or sounds down in locations difficult to reach. A stethoscope mic for instance would be sufficiently isolated from ambient sounds so as to pick up (and amplify) the sound from the primary contacted surface. When I get the time to return to the project, I hope to cover more details in an associated page.

Some time back, I considered the possibility of using stereo separated mics as a method of isolating the origins of a sound which occurs only during motion -- on a PC, you can fairly easily compare relative amplitudes of channels. Imagine using that to isolate where under your dash a squeak is coming from, or checking the exhaust note between banks under load.

From a computer analysis standpoint, the "sound" doesn't necessarily have to be a regular sound -- the audio recording on the camera could just as easily be a pair of TTL voltage signals, providing feedback from a couple of sensors -- perhaps a knock sensor or a pair of O2 sensors, though some signals would need appropriate conversion before you simply plug them into your camera. This basically turns the audio recording device into a low-rez oscilloscope. Bet you didn't realize you had one sitting around, did you?


Sean B. Straw
Post Box 751224
Petaluma, CA 94975-1224 USA

EMail to: Sean.Straw+Jaguar@mail.professional.org

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