2007 DYNO RUNS- NISSAN F54 L28
These three runs were done at Bristol Dyno in East Hartford Connecticut on a Dynojet 248 inertia dyno
My L28 engine in September 2007
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My Dyno excuses:
In a perfect case of Murphy's Law my alternator actually failed on the way to the Dyno. I was actually starting my first run when I realized my cooling fans wouldn't come on because the battery was only at 9 volts @#$%^. So my first run was actually with an undercharged battery, the other two on a battery charger. That says something about an MSD ignition's ability to run at low voltages.
Also I had just put in a new ZX distributor the day before and afterwards discovered the rebuilder had put the reluctor wheel on upside down. The reluctor is unidirectional part and would have run the ignition pulse "square wave" in reverse. And...I found later my carb needles were not flush with the piston bottoms as well, and I think the float bowl levels were wrong. Lots of excuses...I guess I shouldn't have gotten it dynoed with so many tuning problems, but that's the point...do baseline runs to locate and correct any problems.
FUEL RATIO
Sadly, Datsun never created a SU needle for the L28, so for 30 years people have had to use L24 needles for performance. While there are lots of SU needle profiles on the market you'll notice those are for the British SUs (Jag, MG), not Japanese Hitachi SUs. This is why the SU books on the market never mention our N27 or N54 needles. Luckily back in the 1970s someone determined that the British "SM" needle was good for Z performance which has made it pretty much the only choice for performance L28s since then. Some people claim the SM is perfect, some people claim it's too rich. Who's right?
- 14.7 is considered the best stoichiometric fuel ratio for emissions
- 12.8-13.2 is considered the best range for performance with high quench chambers and hot ignitions.
When I had my engine above dynoed I had them sample the 02 levels in the exhaust. Guess what they found? It turns out that SM needles on my engine produced a mixture of 12.1 to 13.5 from 2300 all the way to 7,000. This put it squarely in the performance range. The one deviation was a rich spot between 3k-4.5k. I use 15 weight carb oil, I suspect using 10w (ATF) will quicken the rise of the carb piston and lean it out in that range.
VERDICT: SM carb needles are worthwhile for performance on a free-breathing L28. NOTE: the spikes at 7k are from letting off the throttle.
HORSEPOWER RESULTS
My dyno runs were to gauge rear wheel horsepower. Rear Wheel takes into account drivetrain losses and tire squirm. Flywheel horsepower is based off the motor only and is generally about 20-25% higher depending on who you ask.
My mods raised the stock horsepower peak from 5200 to 5800 which is perfect for a hot street engine. In fact the peak HP holds steady from nearly 5300-6100rpm...with 150+hp on tap from 4600rpm all the way to 7000. Since the fuel mixture is OK at 7k I believe the drop-off visible at 6.5k is due to the cam grind and/or carb flow. Interesting that the 3-4k rich spot in the fuel mixture above corresponds to a slight horsepower dip.
The 1st run was with the intital timing set to 12btdc. For the next two runs I bumped it to 14btdc. It looks like that move picked up a couple of HP at the top end. I also leaned the mixture nuts out a 1/4 turn after the 1st run, but I don't think it affected anything. So I can say truthfully that my engine produces 200+ horsepower but in reality only 165 hits the street.
TORQUE RESULTS
Even more interesting is that the torque peak jumped up from 4000 up to nice peak at 4800. In fact I got over 150ft/lbs from 2400 all the way to 5800...and from 3800-5800 it's over 160ft ft/lbs. I believe the cam I'm using contributed to this as well as my compression boost to 10:1.
So is it worth tweaking a 25 year old 6-cylinder to see if I can pickup more horsepower when it's common today for a 4-cylinder to pull 200HP? YOU BET!!
There aren't too may cars anywhere that have the excitement per hosepower ratio of the Datsun Zcar.
2007 DYNO RESULTS F54 L28 with SU CARBS
STOCK ENGINE
145hp @ 5200
156 ft/lbs torque @ 4000
MODIFIED
165.6 hp @ 5800rpm (207 flywheel)
169.6ft/lbs torque@ 4800
O2 mixture 12.1-13.5, 2300rpm to 7000
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