dyno finally

[TZmb]

Last summer we finally got our 4DP on a dyno and finally, after 15 years got some rational data.
This started with a thorough base-lining of the carbs to Ed Sorbo recommendations and repeated fussy setting of the float heights. I was chagrined to find a substantial imbalance in the carbs and felt that I got them back together and adjusted decently.
Our starting spec on engine #1 was-
ignition 037000-2960
cdi 4DP-00
cylinders 4DP-01
heads 7.5cc
fuel Sunoco 110 'leaded'; 30:1
jetting 340/350

base-line average-----------------> 74.3 hp
2 sizes leaner jetting 320/330----> 76.7
retard ignition to 1.25mm---------> 73.1
advance ignition to 1.75mm-------> 78.4
1 step leaner jetting 310/320------> 77.5

Altogether a very satifying effort with what we consider nice numbers.
One puzzle remains. Between 9200 and 9800 rpm our horsepower and torque curves flatten out before resuming their climb. Unfortunately I am having trouble over file size posting the files from the Sport Devices dyno. Any idea where our flat spot comes from?

[vince24x]

good stuff mike.

speculation, but that rpm range where you're flat is where i believe the YPVS opens. might be something related to that. the 4DP bikes seem to generally like more compression and timing advance. for sure compared to the 5KE stuff....

did you use an inertia dyno or brake dyno? just curious.... i'm not familiar w/ sport devices.

vince

[galloway840]

Great work, Mike!

Any details on ambient conditions? temp, humidity, elevation?

[TZmb]

Vince,
Sportdyno V3.6, roller inertia:4.6
My view of the power-valves has them opening at some 7000rpm and this shows on the graph/data as a smooth floor for the hp climb. 9200 to 9800 plateau remains a mystery with flat hp and a slight dip in torque..

Galloway,
temp 24.4 c
humidity 51%
pressure 982.1 mbar
elevation c900' (Newtonsville, OH)

The best pictures of the runs show as SP.1 files opened with Sportdyno software but they print in a forshortened graph with data grid unique to the printed version. Printing even that as a pdf is still a 30+mb file too large for me to post here unless I am retrained.

[vince24x]

Vince,
Sportdyno V3.6, roller inertia:4.6
My view of the power-valves has them opening at some 7000rpm and this shows on the graph/data as a smooth floor for the hp climb. 9200 to 9800 plateau remains a mystery with flat hp and a slight dip in torque..

interesting.

most of my current knowledge is specific to 5KE. that said, i checked my data and all the YPVS stuff happens for me exactly in the rpm range in question: at 8400 i'm totally closed. begin opening at 8900. almost fully closed at 9750 and full close at 10 krpm.

are you SURE your valve opens fully that much earlier? it sounds a little funny.... or maybe it is opening that early and shouldn't, hence the drop/flat? anywho, not sure it is an easy thing for you to manipulate, but i'd keep the thought in mind as your forge forward. hth.

vince