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crm
Dodge Dakota
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7/06/2002
13:43:19
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 Subject: more dyno results...
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hey guys, got my truck dyno-ed again this morning. hoping for a little help on reading the 2 runs i've done so far. here are the links:
http://www.milkmonkey.com/qcsp/images/dyno-6-29-02.jpg
http://www.milkmonkey.com/qcsp/images/dyno-7-06-02.jpg
the first dyno was run in 2nd gear. the first run where it hit 212 needs to be disregarded because it spiked when we hit the speed limiter. same thing happened today when the dyno operator didnt turn the key fast enough (it hit 221). the only difference in the second test was the addition of a Fastman TB - "true" 68mm.
it's kinda hard to compare the 2 dyno runs because they were run differently. like i mentioned above, the first time i took it he hit the speed limiter in 3rd (98mph) and ran the next 2 pulls in 2nd gear. this of course lowered my tq numbers. today i had them turn the key to disable the speedo and we got 3 very consistent pulls. i was hoping to get a little more out of the TB, but it's hard to tell when yer comparing apples and oranges. it appears the TB moved the powerband a little way into the lower rpm's. also looks like it added maybe 3-4 rwhp and another 5-7 rwtq.
this may have to be my baseline dyno cuz i dont wanna rely on the first dyno sheet due to the differences in the torque in 2nd as opposed to 3rd gear. i'd really appreciate any input you guys can give in helping to decipher the 2 dyno runs.
btw, does torque measure the same way as rwhp? i.e. rwhp x 1.25 = crank hp? cuz right now i'm looking at about 208rwhp and 260 at the crank. would be interested to find out what the crank torque numbers are.
thanks in advance for any help!
-adam
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crm
Dodge Dakota
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7/06/2002
13:44:45
| RE: more dyno results...
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oh btw, i noticed the A/F ratios were different. can someone help me understand what it means?
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Duner
Dodge Dakota
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7/06/2002
14:49:32
| RE: more dyno results...
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I think you will have to disregard the first dyno
pull you made because they were using some sort of
curve smoothing filter with the software which
averaged out the curves. The 2nd set of pulls
looks like it was down by 20 hp or so at 5500 rpms
even with the larger TB. It's so difficult to tell
what's going on when different scales and software
filters are used for two different pulls. They
did't do you any favors there!
The A/F ratios are richer for the 2nd set of pulls
also. The A/F mixture should have been leaner
with a larger TB not richer. My experience has
been that the 4.7 is programmed with too much fuel
to begin with. I think the earlier part of the
first dyno pulls are not at WOT until after 4000
rpms or so, but here again - it's tough to tell
with the filtering they were usin
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crm
Dodge Dakota
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7/06/2002
18:07:22
| RE: more dyno results...
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Message:
so is it safe to say that i should just use this second set of pulls as my baseline and throw out the first?
or is there anything to show that the TB actually hurt/helped performance? not really sure what tot hink about the AF ratio, what is it normally? man, i really need to get a custom flash....ugh, hoped it would be a lot easier to gauge the gains, etc.
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Dakoda
Dodge Dakota
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7/07/2002
09:29:11
| RE: more dyno results...
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I wonder why the dyno operator switched scales from the first set of dyno runs? It is hard to tell. Just think, 280-285 ft. lbs of torque at the rear wheels equates to about 350 at the crank ! Your probably pushing 250 horses at the crank! Not to shabby for a 287 CID motor. Especially that much torque.
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crm
Dodge Dakota
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7/08/2002
10:51:37
| RE: more dyno results...
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yeah, the more i look at the first dyno run print-out the more i get frustrated. but at least this latest pull had 3 very consistent runs. and since this is an automatic tranny, i figure an average of 208.4 * 1.25 = 260.5 at the crank :) overall, not a bad baseline but wish i coulda had something better to compare to for the sake of seeing how much the Fastman TB added.
and do they measure crank TQ the same way as crank HP? i am having a hard time believeing that i'm pushing 360 ft/lbs of TQ at the crank?!?! wow, thats a pretty big number.
anyone got any input on the A/F ration measurements? does it look like it's running a bit too rich for all the mods i've done? or are the numbers just about right?
thanks...
-adam
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Dakoda
Dodge Dakota
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7/08/2002
21:36:07
| RE: more dyno results...
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Iam not sure if the same amount of drivetrain loss of 20-25% is the same for tq. as hp. I do not know anything about the A/F ratio.
Thanks for the info. Oh, BTW I have a 2000 SLT+ CC w/ 4.7L auto, 3.55 LSD. Only mods so far are:
homemade intake w/ K&N filter, and I replaced the stock muffler w/ a Cherry Bomb Vortex muffler. The muffler is similar to a flowmaster. I like the sound as its is different than any other. This truck blows away my last car which was a '88 Monte Carlo SS w/ 305 180hp.
-Dave
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Duner
Dodge Dakota
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7/08/2002
22:31:07
| Vedddyy Intedestingk....
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After looking over the dyno charts....
The first chart's A/F ratios look like the truck
was run-up above the starting rpm and then the
operator eased into the throttle so it wouldn't
downshift into the next lower gear to get the
pull. That starting point of 15.5:1 A/F ratio
tells me that it was coasting or decellerating at
that point since it was on the lean side of
things. Since he eased into the throttle - the A/F
ratio isn't as rich until he hit WOT and open
loop... which looks like it was about 3800-4000
rpm or so on the first set of pulls.
For the second pulls it looks like he leaned into
the throttle a little earlier at the beginning of
the run so the A/F ratio doesn't show that lean
area. For some reason the larger TB appears to
have hurt the power output after 4600 rpms - which
is the exact opposite of my experiences.
Generally, with too much fuel - adding airflow
should help. Here again, I think it's more a
software thing than the actual pull. The A/F
ratios are improved over the first pulls, and was
probably making more power but doesn't show up
compared to the first ones because of the
"smoothing".
On both sets of pulls notice how the A/F ratio
noses over at the same time the HP and TQ curves
do. Once the engine starts to lay down and not
make power.... it has too much fuel for that
airflow and it shows in the A/F ratio. More air
at that point or less fuel would help the A/F
ratio and also make more HP. More than likely, the
catalytic convertor is choking the engine off at
that 5000 rpm area. A larger cat would help and
it would show an improvement on all of the curves.
A reprogrammed PCM would also show improvement in
that area.
The driveline loss is applied to both, since in
reality we're talking about torque... the HP
numbers are derivative. I'm not sure that some of
that high torque number isn't a result of how they
actually have to do the pull to begin with.
(run-up of the dyno to speed and then ease into
the throttle to get it to pull but not downshift).
The curves from manual trans vehicles always look
way different at the beginning since they can
start the pull from a lower rpm.
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crm
Dodge Dakota
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7/23/2002
12:23:48
| RE: more dyno results...
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Message:
wow, great info duner! sorry i havent had a chance to respond to this earlier, but now i have a much better understand and feel a bit better about the whole ordeal.
a better (or gutted) cat is definitely next on the list. dont know if i'll be able to do the cams and intake as soon as i had hoped, but those as well as a PCM flash are on the list sooner or later.
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