db&HVWs dyno tests

I thought it would be interesting to see the graphs of some dyno tests of modified 1600-based engines in a recent (Feb. 1996) 'dune buggies and hot VWs' article. I entered the chart into a little graphing program and plotted the results. Results subject to typos, naturally. Note that the curves drawn through the points are not to be taken literally, as they're just the 'interpolation' function of the graphing program and are just intended to make the plots easier to look at. Also beware that the scaling from plot to plot may not be exactly the same. What I did was to plot each test against the stock engine test. It was a quick and dirty thing, so I just went with the default axis labelling and churned them out. The verticle axis unit for all plots is horsepower. You can download the data and replot at will. (Sorry, they're in sci. notation.)

I liked the idea of these tests and I think that the results are interesting. While reading the article, there were a couple of funny things that I noticed:

• Why did they do the test only down to 2500rpm? Is it to hide that the highly modified engines will only idle at excessive speeds?
• After Test #9, they noticed that all the intake valves were leaking and the valve springs were thrashed. At what point did that happen? Test #6? Test #8? Also, they said they used 25gallons of gas in their entire test. Is dyno testing that hard on an engine? Or are some of their mods ill-conceived?
• When they added the 009 mechanical advance distributor, they were very excited about the 4hp gain at the top end. The test before had been done with a vac./mech stock distributor. Both tests w/ dual Kadron carbs. Now, at a steady-state dyno rpm, shouldn't both dizzys be at full advance at the max rpm? Doesn't this just mean that they had the two engines timed for different max advances, so that the top-end benefit of the 009 is simply due to different timing? I don't get it. (Hey dude, for about forty bucks I can throw a 009 on my Bug and get almost 10% more horsepower! Rad! Sano!) Hmmm, is this all about $elling 009s or high performance? Hmmmm...
• From the pictures, it doesn't look like they used air cleaners in any of their tests.
• Are dyno tests reliable to four significant figures?
• When they replaced the Dellortos from Test #15 with the Kadrons (Test #16) the peak power only went down by about 4% or so... hmmm. I seem to recall folks saying that the number of barrels isn't as critical as their diameter... (flame bait???)

The base engine (Test #1) is an align-bored GEX 1600 with 7.0:1 compression ratio.

Test #2: 1-3/8inch header, single QP

Test #3: remove QP, install stinger w/ baffle

Test #4: remove stinger's baffle

Test #5: remove stinger, reinstall QP; replace manifold center section w/ fancier one

Test #6: induction system replaced with a pair of 40mm Kadron/Solex carbs

Test #7: stock distributor replaced w/ 009 @ 32deg max advance

Test #8: stock rocker arms replaced with 1:1.4 ratio arms; stock push rods replaced with steel push rods

Test #9: single QP replaced with dual QP

Test #10: valve job done to replace ruined valves; ruined valve springs replaced with stiffer ones; Engle 110 cam and Scat lifters installed; stock 1:1.1 ratio rocker arms reinstalled (appropriate for cam); swivel feet adjusters installed

Test #11: Kadrons replaced by a pair of 40mm Dellortos

Test #12: replaced dual QP with single QP; carb jetting changed

Test #13: GEX align-bored case replaced by Rimco align-bored case cleared for 90.5mm jugs and stroker crank; plumbed for full flow oil; 90.5mm pistons installed; same GEX innards in the new case; compression ratio corrected to 7.0:1 to match previous tests; 009 set to 28deg max advance

Test #14: 009 returned to 32deg max advance, dual QP mufflers reinstalled

Test #15: exhaust replaced with 1-1/2inch 'competition' system with merged collector and larger inner diameter mufflers

Test #16: Dellortos replace by the Kadrons used above

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Greg Merritt (gregm@vwtype3.org)