B20 Dyno Testing

Dyno Session #1
Dyno Session #2

Dyno Session #3

B20Z vs. B20B

We did the best we could to compare the two engines. The intake manifold, intake, exhaust system, ecu and dyno facility are all the same. Only differences are the engine and the day tested. These runs are with the new cat.

The gains are impressive. 10 hp and 9 ft-lbs starting from 4500 rpm. I expected more of a gain through the low rpm band, due to the increase in compression from the 8.8 CR B20B, to the 9.6 CR of the B20Z. But the butt-dyno agrees that the gains are all in the upper range. I was actually worried that the Z had lost torque because the difference in power between the upper rpm range and lower rpm range was so large. The B20Z feels great. It really pulls hard from 4000 up. 1st gear is good till 7k. With 2nd I shift at 6.5k if I plan to run 3rd gear hard, or I run it to 7k, if that's about all the speed I need. As you can see, the torque REALLY falls off at the top. At 6.7K the torque is the less than at 2k!! You can feel it, and you quickly learn to shift early.

Exhaustive Testing

For this dyno session we tested 6 exhaust combos. Unfortunately the results were not very good. I had hoped not to gain significant power when the new cat with replaced by a straight pipe. But, switching to the straight pipe gained significantly on both systems we tested it on. Even worse, when analyzing the curves after we were all finished, we realized that removing the cat peaked out the limits of the stock fuel system. Basically, once the cat was replaced with a straight pipe, all four exhausts made the same power. The most likely explanation is that the system was running lean.
Systems tested:
    MagnaFlow Street cat back system.
    MagnaFlow Race rear section that bolted to the Street system piping.
    Greddy BL, old and well used, (painted flat black).
    Tanabe Racing Medallion rear section that bolted to the Greddy piping.

magnaflow race, tanabe, greddy magnaflow street, tanabe, mf race magnaflow race, tanabe magnaflow race, tanabe no cat, magnaflow piping


Dyno Results:
MagnaFlow Street with (blue) and without cat (red)
MagnaFlow Race with (blue) and without cat (red)
MagnaFlow Street (blue) vs. Race (red), both with cat
All four without cat (I am not telling which is which, because it statistically doesn't matter)

Sound files:
The sounds files are mono, mp3s that are autogain balanced. Because of this the actual loudness difference between the exhausts is not accurately represented. But the tone is accurate. Keep in mind that the JDM ITR 4-1 header adds a metallic blatty rasp to all the system. Sound is very subjective. So listen and make your own decisions on what you like. My comments are an attempt to be objective.

Magnaflow Street with cat Quiet, with a slight fluff sound
Magnaflow Street without cat Louder, fluff is more pronounced, JDM 4-1 blat more noticeable
Magnaflow Race with cat Loud, deep at low rpms
Magnaflow Race without cat Much louder especially at high rpm, deep and loud at low rpms. Plenty of JDM 4-1 blat comes thru
Greddy BL without cat Lower frequency, controls the R header blat
Tanabe RM without cat The loudest at all rpms, plenty of blat.

Final Curves and thoughts for next time

Final curve from the dyno session. No ign, fuel or cam timing tuning was done.

98 B20Z stock head and block, 94 P75/LS ecu
Intake: GSR stock cone filter and tube (no airbox), LS intake manifold, 64mm TB
Ex: JDM 4-1, test pipe, Greddy BL exhaust

Comments: 138hp @ 5700 and 132 ft-lbs @ 5200 to the wheels. Versus factory specs of 146 hp @ 6200 and 133 @ 4500 to the flywheel. So the flywheel numbers would look more like 156hp and 150ft-lbs. All that torque from what is basically just header, exhaust and a stock GSR cotton filter. I do want to find out why my hp peak is at 5700, and a stock 99-01 CRV is peaking at 6200. Probably running out of fuel.

Next time: Obviously some tuning is in order. Cam gears, FPR, the Shogun, and maybe a J&S will be added to the mix. Lets see what this baby can do.


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