Laust's Jalpa Project

 

Page 6 - Minor annoyances and repairs since March 2006.

 

The main current activity is tuning the car for optimum fuel and timing. Using a narrow band O2 sensor my approach is to first tune the fuel map for stoichiometric and then add fuel for high load conditions and subtract fuel for low load conditions. The timing is initially set about 2 degrees less than pinging on 87 octane fuel. Later I'll create a map for 91 octane with more aggressive timing. It turned out that the spring in the blow off valve (BOV) was a little weak and possibly the pressure signals are contaminated with some dynamic pressures, so the BOV was leaking some air at wide open throttle (WOT). I corrected this by pulling on the BOV spring (taller free height), which pushed the turbos into surge conditions (very ominous sounding) under very quick throttle release.

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P3020054C (3-2-2006): One day when I returned to my Jalpa in a parking lot the passenger side mirror was dangling in its wires. Apparently broken by someone bumping into the mirror combined with the fact that the spring loaded swing mechanism was seized. A few days later the drivers side mirror just fell off when driving again (fortunately) dangling in its electrical wires. In both cases the mounting eye on the cast aluminum base was broken and with some effort I managed to repair both with some aluminum brazing and hopefully strengthening them a bit in the process. The spring loaded swing mechanisms were lubricated and now work as intended. 

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P3060066 (3-6-2006): On a trip to San Diego (2x230 miles) I blew an exhaust gasket as seen to the left. That particular flange on the high pressure side of the exhaust (between the heads and turbos) is a bit flimsy and I may have to upgrade that next time the engine is out. For now it appears that I can get away with gasket which I made out of 1/32" high temperature material covered with a thin brass sheet wrapped through the inner hole (crummy picture quality, camera didn't focus properly).

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P4280125C (4-18-2006): For some reason the air bleeding from the electric waterpump did not purge air as it should since the flow was going in the opposite direction of what I expected. I then designed and installed a recovery tank, simply consisting of a long thin aluminum tube with inlet designed to always be immerged in coolant and outlet designed so ensure maximum coolant level at the top. It seems to work as intended.

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P4210122C (4-21-2006): The car suffered from sagging suspension springs to the extent that the shock absorber bump stops were all crushed and sometimes the front wheel scraped the fender when turning. Having looked at pictures of many other Jalpas it appears to be a generic problem. Aesthetically the car also looked "slammed" (an official ricer term for extremely lowered). So I first designed some aluminum spacers (~10mm height) which can be seen at the bottom of the spring and since this was not enough I designed some Delrin spacers to be used between the coil windings, which also stiffen the springs by N/(N-1) with N being the total number of coil windings, which corresponds to a 15/13% increase front/rear. The car looks and handles much better now.

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PC190243 (12-19-2006): The front suspension just didn’t feel right so after some probing I discovered that after the front end had been manually lifted it would settle down ˝” higher that before, meaning that there must be some friction involved. I then looked for strut insert alternatives and found Koni 8610-1437 (one-way adjustable) as a very likely candidate. I purchased a set, took the front suspension off, which actually was quite easy and disassembled the struts. As can be seen the bellows were torn and bump stop crushed (sagging springs). It also turned out that the shock absorber shaft had some scraping sounds and was precessing ~3 mm when rotated. Otherwise the shocks were actually working well enough to get a sense that the compression was very soft and rebound maybe twice as hard. The new Konis had maybe 30% harder compression and I adjusted the rebound proportionally harder (than the OEM), which ended up as 1.5 turns from softest towards firm. The Konis needed a ˝” spacer at the bottom and some machining on the cast iron fitment ring (OD from 44.0 mm to 42.2 mm) and inside the very lower section of the large compression nut (ID from 42.4 mm to 44.0 mm).

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PC200248 (12-20-2006): As the picture shows, I also machined a single 1.0” spacer for the sagging springs, while having a ˝” split spacer ready is need should be. It turns out that I should have filled the strut tube with oil for better heat conductivity and I was also unable to find a dust bellow to cover the shaft. Those two things will have to wait for next time. A short test drive showed that the upgrade was worthwhile.

 

As of January 2007 the following functions have not yet been connected/activated:

1) A/C hoses have not been connected to compressor

2) Port water injection has not yet been connected

3) Serial-parallel switching of the turbos has not been debugged. Switching the intake to serial connection for mysterious reasons eliminates the boost and the exhaust switching is getting a little difficult, since there now is a lot of friction in the triple butterfly valve. Maybe my tolerances were too tight or it just needs some exercise. It is currently set at parallel for both intake and exhaust and the boost comes on strong at 3000 rpm.

~o0o~