I've got a GTD autocrosser update!
For the first time in months, I put a little attention to my Rabbit GTD 1.6lTD autocrosser. You guys might recall last time I worked on it (look up four posts in this thread), I reset the cam timing and adjusted a couple valve shims to make them less tight. That was after I had fixed an excess voltage drop problem across the starter solenoid (which boosted cranking rpms... although still not enough to be able for a boosterless cold start), and after that, checked the compression to find peak cranking pressures were low, although even. Busy finishing off a master's degree, I have just let the project sit under the car cover since then.
Now, feeling good following the success of VNT-turbo'ing dad's Rabbit 1.6, I decided why not take the car cover off my Rabbit and see if she might actually start? I didn't try recharging the battery (which is a miniature, lightweight racing style), but found it checked out at a touch over 12.5 volts - seemed OK. I got in the car and gave it a good full glow plug cycle as I usually do for hard starting motors. I recalled waiting for the glow plugs to switch off let the engine crank over a little quicker, so that was my strategy. I had also since the over-revv incident, installed a slow glow relay into this car, but man does it seem to take a long while until I actually heard it click off... over 40 seconds I'd say and it's not like it's that cold out. I was imaging my battery draining and draining...
As soon as I heard the glow plug relay click and shut off current to the glow plugs, I started cranking. It cranked quite brisky, feeling as if it might start, although after a few seconds it still hadn't reached RPMs with were self-sustaining. The RPMs were starting to drop now, for sure the battery voltage was dropping. I stopped cranking,and felt my heart sink a bit. Decided to make one last attempt at starting the motor on this several-month old battery charge... I gave it a little bit of glow plug, just a few seconds this time - perhaps just long enough to make the light go out - and with glow plugs still blazing, switched on the starter. It cranked over, yes, a little bit more briskly now... quickly increasing in speed quick enough, and yay - was running all by itself!
I started the thing without even recharging the battery after letting it sit for months!
Driving it was like being reunited with a good friend. I enjoyed being reacquainted with it's characteristic mufflerless motor roar and turbine whine. This thing is such a high performance machine... especially after getting used to driving dad's daily driver Rabbit (which has bilstein HDs, stock GTI springs and swaybars) the GTD autocrosser just handles like crazy, despite decades-old, bald tires; one of them even showing some cord! (I know I need to do something about the street tire situation.) Engine still pulls like crazy, just as long as I don't lug it so much as to keep the turbo working. But with some shifting attention, the close-ratio five speed allows that, and the peloquin torque sensing diff puts the power down nicely. With the copious fueling quantities, even off-boost it gets decent acceleration. And it's just pretty crazy with the foot in the floor when the boost comes on!
And I became reminded there are still many old problems I've got to fix before I can start racing it again... there is a clunking/knocking I can feel through the pedals/floor when the clutch is engaged. The fuel injection still needs some fine-tuning to make it easier to control the throttle - sometimes the RPMs don't want to return back down at all. There is a bit of oil coming out of the blowby vapors I need to deal with and make it clean, even if it means installing a bulky and pricey MANN pro-vent. The clutch pedal needs adjusting. And I previously took the carpet out to clean, which I need to re-install along with all the trim that goes over the carpet. But anyway, I was thrilled to have started it up on the first try (ok maybe second try.)
Just wanted to let you guys know... I think the cam timing and/or loosening up the intake valve clearances made a difference with making the engine easier to start! VW powertrain engineers knew what they were doing when they designed the intake valve to close as early as it does.
I can't help think there was something that happened to the motor either during those brief few seconds when it was over-revving, or after when I was putting the head back on, that reduced it's low-speed compression. High-speed compression, FWIW, seems great to me, at least if engine power is any incication. I remember when I had the head off and was prepping for reinstalling the new one, cleaning off all the carbon deposits from around the tops of the cylinders... maybe I shouldn't have done that? I remember taking the scotch-brite pad into the area where the top ring sealed, although I tried moving the pad in the same direction as the hone marks and also thinking the scuffing was only very light. I also remember thinking that the bores looked as good as I could imagine they could, at least by my untrained naked eye. I am wondering if I should try putting some non-synthetic oil in the sump and taking it for a long hard drive, to see if I might be able to get the top compression ring to reseal.
Anyway, even if I can't make it any easier starting, I can probably use it "as-is" for another racing season or two. I could lug around one of those big 40-lb optima batteries with me in the trunk to events and use it if the standard battery can't get the cold starting job done. Maybe I could mount it to a little cart and hook up some big booster battery cables with a quick-release connection engaging to the main starter cables for some starting voltage assist. But of course, if it's possible to cheaply do, I would love to try and raise the compression back up and make the engine start as easily as it used to. Actually if I could get the engine compression as good as it used to be, it should not start better than it used to with the voltage drop in the starter solenoid fixed.
I am looking forward to getting this car prepped for racing again and taking it out to the local events... I haven't even raced on my new custom CNC-machined / lightened racing wheel centers yet!
