John, take a look at my dyno sheets on my website. You can see how the tq
curve flattens out with each of my mods. I found the same problem with my
A/F running way rich, now I have the opposite problem :-)
_______________________
Jon Smith--Raleigh, NC
jon@fast4x4.net
www.fast4x4.net
'95 Dakota 4x4 318 CC auto
----- Original Message -----
From: John Neff <jndneff@texas.net>
To: Dakota Mailing List <dakota-truck@buffnet.net>; DiRT <dirt@4x4wire.com>
Sent: Sunday, November 19, 2000 10:54 AM
Subject: DML: Dyno Pull
I took my Dak to Colvin Automotive in Austin yesterday for it's first ever
dyno run. I'm sure like most I had high hopes that I would be pleasantly
surprised, but had a feeling I would be slightly let down. To say that I
ended up being highly disappointed would be the understatement of the year.
As a recap, this is my Dak's current configuration and mods.
98 CC 4X4. 5.2L, Auto
Intense Performance intake tube with K&N cone filter
F&B stage 1 TB
Mopar computer
Mopar headers
MSD 6A with stock coil
Gibson cat back
Stock, published, numbers are 235 HP and 300 ft. lbs. TQ. These are at the
flywheel. I pulled 189.5 HP at 4400 RPM and 254.5 ft. lbs. at 3600 RPM. My
weather correction factor is 1.0. So, no loss from adverse weather.
Calculate back the 25% loss for the drive train and I end up with 252.67 HP
and 339.33 TQ at the flywheel. That's a gain of 17.67 HP and 39.33 TQ.
Lucky for me, the guys on the dyno were just as curious about all this as I
was, but noted that my torque started to fall off a bit too early for me to
make any kind of serious high end HP. After 3600, the TQ just slides off.
Because they were curious and had nothing better to do, they hooked up the
air/fuel meter (tail pipe sniffer) and gave me a couple of free pulls. The
end result? I'm going off the scale on the rich end at WOT. They wanted to
see about 12:1, but instead I went below 9:1. They suggested I either get
more air into the engine, or cut back on the fuel. Since we all know that
you need fuel to make power, I'd rather just get the air flow where it needs
to be. BTW, we made a pull without the air filter, and it make zero
difference.
Looks like it's time to start saving for an MPI manifold, and a Hughes cam.
I'm also thinking about having Bruce open up my old stock TB to 52mm and see
what that does for me.
Oh, one other thing, the dyno confirmed a suspicion I've had for a long
time. There is a noticeable flat spot in TQ from 2200-2800 RPM. At 2800, it
jumps then almost plateaus to 3600 where is starts to slowly drop off. That
would explain the lunge I feel the truck make just before 3000.
John
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:57:29 EDT