|
SOME OTHER DIFFERENCES The ports on the new head are slightly different than those on earlier versions. The valve-guide bosses protrude further into the port area of both intake and exhaust ports. Since the springs sit lower and closer to the port area on the hydraulic head in order to make room for the hydraulic lifters, the head contains less aluminum above the valveguide bosses. This makes the valveguide boss even more important to longevity than on earlier heads. The mechanical lifter which heads the hydraulic head has slightly smaller exhaust ports than the mechanical-lifter heads, which,, combined with the larger guide bosses, can only hurt gas flow and performance. The cam has one less cap than the earlier heads, in furtherance of reducing internal engine friction. Though anything that loads the new cam, such as a timing belt that is too tightly adjusted, will produce cam wear about 20 percent quicker than on the earlier heads, normal use should give no problems. It is this attention to detail that gives the new VW engines such excellent gas mileage. The injector bosses for the fuelinjector nozzles protrude further into the head than on previous designs, and are designed to improve emulsification of fuel-air mixture. Those VW left unchanged, feeling that any modifications would probably hurt performance more than help.
The Techtonics StreetPort Head is not a full-on race head offering only high-rpm at the expense of the bottomend torque and a lifetime counted in laps instead of in years. It isn't an allout, high-bucks conversion, using bigger valves and requiring changing the factory valve seats. It is not the result of flowbench testing conducted without the more important dyno results. And finally, it isn't the answer to doubling your horsepower with a relatively simple bolt-on task. The Techtonics StreetPort Head is the application of Techtonics and Darrel Vittone's years of experience with Volkswagen stock and high-performance engines. Not only does it reflect performance goals, but it also represents the basic philosophy that shows itself in any product Techtonics sells. A high performance engine doesn't haue to haue a much shorter life span than a stock engine. This same philosophy applies to the high-quality Techtonics Big Bore pistons, to a TechtonicsTuned 2020cc motor or the trick TechtonicsTuned exhaust system for the pre-1985 cars. All add power, fit right and last a long time. It is therefore no wonder that the modifications and port work in the Techtonics StreetPort head stress longevity as well as performance. The StreetPort head for the hydraulicengined cars is priced at $399.95 exhange, complete. Here's what you get: The production work belongs on a seasoned cylinder head in good condition. Techtonics tries to keep a stock of StreetPort modified cylinder heads on the shelf, ready to exchange with your head in order to minimize any downtime for your car. Modifications begin with a complete disassembly, cleaning and inspection of the cylinder head. A competitionstyle three-angle valve job and attention to the valve-seat area come first. The stock valves and seats are not changed. It is Techtonics' strong feeling that few, if any, aftermarket valves equal the quality and longevity offered by the stoc~ VW valves. rhey also feel that any increase in horsepower that larger valves would provide (particularly on stock-displacement engines) would not be worth the possible reduction in engine life. Like the stock VW head, a Techtonics StreetPort head is intended to go 100,000 miles plus. The combustion chamber is left as it came from the factory, as any grinding would lower the compression ratio and probably hurt performance more than help it. Examination of the chambers and piston tops in the thrashed dyno motor show good, even combustion with no indication of hot spots, so it looks as though there is little need to modify the chamber. |
Next, the careful porting begins, with most of the time being spent in the critical valve-throat area. The valveguide boss is retained, but is streamlined. Techtonics feels that the hydraulic heads in particular require the extra support in that area. While removal of the guide boss is a first step on a race motor and one that will always give better flow, Techtonics feels that it is not appropriate on a street cylinder head. Both intake and exhaust ports are enlarged, following guidelines based on Darrel Vittone's and Techtonics' many years of experience with high-performance cylinder heads. When it comes to grinding a StreetPort head, gas flow velocity, port shape and driveability are as important as all-out horsepower. When the hours of noisy porting are over, the head is cleaned, assembled and placed in stock" ready to ship. BASELINE INFORMATION The engine used for baseline testing is the same one used in our February and April reports. The stock 1800cc bottom end, (actually 1781cc) "HD" series motor from a 1985 GTI was tested with a NeuspeedlTechtonics 268:degree chamshaft, first with the stock head and then with the Techtonics StreetPort head as described above. For the Techtonics dyno tests a 1986 ignition box was used, with the initial ignition timing set at 12 degrees BTDC. The stock CIS-E fuel injection, stock VW throttle body and stock intake manifold are used. The engine also contains the complete Lambda oxygen sensor system, and the fuel injection is set to stock specs. In order to simplify the testing and allow as many of the tested parts to be returned as possible, the baseline and subsequent tests of the Techtonics StreetPort head were done with Techtonic's standard dyno exhaust setup: an early-style cast-iron manifold and Techtonics twin-tube downpipe with the Techtonicruned exhaust system. Darrel Vittone has conducted enough dyno test with this engine to know that while this exhaust system is not identical to the system used in the cars, the results will be accurately transferable. Again, as with any test situation, the proper perspective places most importance on the relative gain achieved, not the absolute numbers. The accompanying graph shows the results quite clearly. As is standard procedure at Techtonics, all tests are done with a VW cooling system and corrected for temperature and barometric pressure. The average of three test runs is used for each data point. We were at Techtonics for the initial test sessions and had an opportunity to inspect the piston surfaces before the StreetPort head was installed. Dyno testing puts a much greater load on an engine than does just about any real-world driving. Any wear or problems shows up much more quickly on a dyno than in the real world. It was interesting to see that despite an enormous amount of dyno testing, the piston surfaces of the GTI motor indicated excellent, even combustion. There was no indication whatsoever of any oil burning or pre-ignition problems. Those of you who have written asking how test changes, such as timing, affect engine reliability, would be heartened to see that despite all the heavy load and high-rpm testing, everything looks perfect. CONCLUSlON As the test results show, the Techtonics StreetPort cylinder head on a stock displacement gives an added boost to low- and mid-range torque and horsepower, with no loss at high rpm. That low- and mid-range boost are what's felt most in street driving. Techtonics does not recommend a StreetPort head as the first step in modifying your engine, but rather as the step after the ignition timing, exhaust and cam have been handled. It's the last step before getting serious with a Techtonics 2020 motor! Next issue we'll be taking a look at that big 2020, featuring a 94.5mm crank and Techtonics Bigbore pistons. Tests will include both the stock and StreetPort heads. The StreetPort head will probably give even better results on the large motor. 16-VALVE TEASER Techtonics
16-valve tests are under way, as promised. We'll keep you informed
of the results as they arrive, but for a teaser, the stock motor
made 123 hp as advertised. The quick gain from advancing the
timing did not work on the 16-V. By adding a Euro-exhaust cam
and downpipe from Automotive Performance Systems, the horsepower
jumped to 136, a I0-percent increase. |
