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October 26, 2005
Gearing Spreadsheet
http://www.skulte.com/z28tt/gears.xls
I whipped up a Excel spreadsheet that can help pick your shift points, based on maximizing your HP in the current and the following gears. It's filled with my info, but you can overwrite the cells (in blue) for your cars.
1. Enter Gear Ratios, Tire Diameter, and Rear Ratio (in blue). Current numbers are actuals from the Z28tt.
2. Enter approximate shift points (in blue).
3. Enter Horsepower Numbers on "Matrix" worksheet. Currently they are calculated from a 4th order polynomial that matches the Z28tt power curve from an old dyno run.
4. Play with shift points to max out "AvgHP", which is area under the curve. These are the intersection points of the HP vs MPH curves below. Change the shiftpoints to match the "Shift MPH" on the graph below. You'll see it affects the next gear as well, since that is the starting rpm for the next gear.
First step was to get the gear ratios, shift points, and the following gears starting rpm. That generates the gear drop chart below, and is good for figuring out what speeds are possible in what gears. Next was to get HP in there. I wanted to use a simple calc formula to get "area under the curve", based on my dynochart's polynomial equation, but I couldn't figure out how to make Excel do that, so I had to create a "true/false" matrix, based on whether the rpm is inside the gear's range (start and finish rpm), and only count the true cells in the average. You can overwrite the torque values in blue to get your own dyno curves in there. If you want to use a polynomial function, and just change values A-D, graph the HP as a scatter plot, finish that, and then click on "chart>add trendline" and click on "display formula on chart". You can enter those values into A through D. The worksheet is protected to prevent accidental overtypes.
Later on, I'd like to add a start and finish mph, so you can max out HP for specific straights between corners. This would let you pick rear ratios to optimize specific tracks, since we're not about to change internal gear ratios in the T56. If anyone knows an easier way of doing this, I'm all ears.
Posted by Z28tt at 7:58 AM
Oiling System Tests
My oiling issues first appeared with this new engine. The oil pressure would drop under sustained cornering (big bend at Limerock, the oval at Pocono, etc...). Added a 3 qt Accusump, but that didn't help much.
Oiling system is a wet sump, Melling 155HV
blueprinted pump (Canton), fed through -12's to a CM filter, through the cooler, and into the front of the block (Dart LittleM). All galleys were fed in parallel. I removed the engine, verified pickup clearance at about 3/8", and blocked off the front of the lifter galleys so the mains are fed first. Lifter galleys then get fed from the rear of the block through .1875 orifice plugs.
For my tests, I removed the intake manifold, and had my oil pump primer driven by my drill press head spinning at 590 rpm (1180 engine rpm effectively). There is a lab grade 5" pressure gauge at the oil inlet at the front of the block, and my Autometer gauge at the rear of the block (reads 4 psi low to the same source, but all numbers are corrected below).
Tests using 20W50 oil at 60 degrees air temp.
Test1 - Block off front lifter galleys, no plugs/orifices in rear Front gauge at 30 psi, and rear at 27 psi.
Test2 - Block off lifter galleys completely. Front gauge at 63 psi, rear also at 63.
Test3 - Feed lifters from rear with .1875" orifice plugs. 35 psi front, 27 psi rear
Test4 - Block off passenger lifter galley completely. Drivers has .1875 orifice. Pressure back at 60 psi.
Just realized the oil pump primer may be blocking the oil galley orifice, so I measured w/ the mic, and there is plenty of room in the groove. For kicks - I raised the primer slightly, and pressure jumped to 55 psi. Raised it again, and up to 60 psi. I think it's time to get the old dist, and turn that into a primer. Anyone know what kind of oil flow & pressure hydraulic roller lifters need? The "techs" at CompCams tell me not to restrict it, but can't tell me what sort of flow I need.
I then took an old distributor, bolted down the intake manifold, and ran the pressure tests - 63 up front and rear. I guess the generic $20 primer gave funny data. Anyways, I'll leave the orifices in place for now, and see if the lifters tick. I also considered making an engine run stand that I can rotate to 63 degrees to simulate 2g cornering (not that I come that close), and seeing if the oiling issue is drainback from the heads under hard cornering.
Tangent(tilt degrees) = Simulated G's
Tan(63.4)=2 G's
Posted by Z28tt at 7:50 AM
October 23, 2005
Oiling Systen
Late Model Camaro/Firebird Roadrace Pan (15-246) with 3 trap doors, teflon coated windage tray, full length recovery pouch, 6 qt sump for 7 qt capacity
Canton High Volume Pressure Balanced Oilpump (21-560) - Melling M155HV (4.5gpm@idle, according to Melling)
3/4" pickup, 3/8" above bottom of pan
Oil Pump Bypass Plugged
Canton Remote Oil Filter Boss (22-581) with inlet plugged by -12 O-ring plug
-12 90 deg O-ring hose end, 46" -12 Aeroquip Braided Stainless hose, 12 90 deg O-ring hose end
Canton/Mecca 6" tall billet oil filter (C/M 25-106) with long 8 micron filter element (26-100) and -12 o-ring bottom inlet and side outlet (flows 90 gpm?!!)
-12 o-ring to -12 AN male fitting
-12 straight hose end, hose, 45 deg hose end
-12 to 1/2" NPT male adapter
oil cooler
-12 to 1/2" NPT male adapter
-12 straight hose end, -12 hose (37.5"), -12 45 deg hose end
-12 to 1/2" NPT 45 deg adapter (with -4an welded on for turbo oil feeds)
Engine Block feed in front
Blocked off lifter galleys
Lifter galleys fed from rear after mains through .1875" orifice plugs
3qt Canton Accusump (24-006) with manual ball valve inside cabin fed through -10 firewall connector and -10 hose to 1/2" NPT feed at top rear of block
Posted by Z28tt at 7:26 PM