P7100 cc's

D

dixiepc

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Joined
Nov 13, 2022
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I have a 190hp 12mm P7100 from a bus engine
that I had maxed and balanced and it came back at 750cc per 1000 revs at 1400 rpm's. Does that seem possible to anybody? I have my reservations about those numbers.
 
The most I have ever heard of from 12mm plungers is in the 650cc range from Columbus Diesel....I'm no pump guru, but 750cc from a bus pump seems like a pipe dream...

Chris
 
Snedge said:
Isn't 1400 RPM an odd place to have max fuel ?
Click to expand...

P7100 turns half engine speed, doesn't it? So, that would make it 2800RPM on the engine?

I mean, would be a towing monster if you could get the air to it LOL
Chris
 
dixiepc said:
I have a 190hp 12mm P7100 from a bus engine
that I had maxed and balanced and it came back at 750cc per 1000 revs at 1400 rpm's. Does that seem possible to anybody? I have my reservations about those numbers.
Click to expand...
Those bus 12mm plungers have a slightly taller helix than the 215 12mm plungers, so they can be tuned up a touch higher, say 25 to 50ccs. With Full Cuts, the highest I've done on a 215 plunger is 825 cc's. Keep in mind, some plungers can only go high 700's before they go solid meaning never open the spill port so the injection event is terribly long and injects fuel till the plunger tops out on the cam. (Long smokey, almost unburnable injection event). If barrels are turned far enough that the spill port never opens, a 12mm plunger can flow plus or minus 940 cc's, but on the dyno it will lose hundreds of horsepower with the barrels turned "solid" meaning no spill port end to the injection event.

In dyno testing 12mm pumps, there is very little peak power gain going from say 650cc's to 750cc's and arguably nothing gained at 800 cc's. The 750cc setting is so long, it requires more timing to burn the late fuel which is offset by negative torque from the high timing hurting the early portion of the injection event. Rough numbers here but realistic spreads: 650 cc's made 1230 rwhp at 35* up to 40* timing 472/GT55 106mm compounds. Higher timing on all fuel settings carried a little better at 4000+ rpm but peak power was the same and happened around 3600 rpm. 750 cc's made 1220 rwhp at 35*, and 1260 rwhp at 40*, but carried almost 100 more HP at 4800 RPM vs 650 cc's at the same timing. 750cc's peak came in at 3700 RPM so nearly the same peak power amount and RPM but slightly softer bottom end numbers below 3000 RPM. 800ish cc's made 1235 HP at 40*, more smoke, less EGT, richer AFR readings on the O2 sensor, and was down a little on boost everywhere; at 4500+ RPM the 800cc setting was maybe 75 HP better than 650 cc's, but worse than 750 cc's.

During the relatively short loaded dyno pulls, the lowest EGT runs were 650 cc's around 1550F, the next lowest was 800 cc's around 1650F, and 750cc's were hottest up around 1800F.

And to really throw in a wrench, 550 cc's made 1125 HP, same 3600 ish RPM power peak, only needed 30* timing to acheive max power, but down 200ish HP at 4500 RPM, clean as a whistle with AFR showing 5 to 10% leaner than stoic, and 1250 EGT. So 550 cc's is lean, clean, and cool, should run all day.
 
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