Flat HP curve...could something be up?
03-12-2018, 10:47 AM
#1
Flat HP curve...could something be up? I don't have my dyno graph but I can tell you my mods and what the graph was doing at what RPM. First off I will say this is a TIGHT dyno. It will hurt your feelings...seriously. It is highly accurate and very well maintained and that's all that matters here so don't judge my numbers too harshly. A cammed/stalled 6.0 truck did less than me and a cammed LS2 vette did really similar numbers.
My mods-RCSB s10
LS1, stock 243 heads, LS7 lifters, Trunion upgrade stock rockers, MS3 112 LSA, dual .660 springs, stock Vic jr, 4150 TB, 42lb injectors, 4L60E, Yank SS4000, 31 spline 8.8, 3.73 gears.
I made 7 3rd gear pulls for a final total of 341hp @ 6850 RPM.
My issue is this...the HP ran up hard to 5200 rpm and was making right around 300 hp at this point then by 6200 it had jumped up to the mid 330s rolled off flat and only gained 2-3 hp by the peak and never fell off. The graph was not smoothed so I wasn't getting visible float and she pulled hard all the way to 7k.
I took it to the track later that day and could not get it to stick out of the hole. It was the first night the track was open and I was having issues keeping the tail end from walking out from under the truck for a proper burnout. The Hoosier DR2s did get me two 1.90 60' spinning hard but I had to set my shift points VERY early to get a full pass. My best run shifting at 5600 rpm was 13.14@105 with a 2.185 babying it out of the hole so it wouldn't spin.
I will eventually be sending the 243s and Vic to AI for port work but I'm curious about that flat HP curve...any ideas?
My mods-RCSB s10
LS1, stock 243 heads, LS7 lifters, Trunion upgrade stock rockers, MS3 112 LSA, dual .660 springs, stock Vic jr, 4150 TB, 42lb injectors, 4L60E, Yank SS4000, 31 spline 8.8, 3.73 gears.
I made 7 3rd gear pulls for a final total of 341hp @ 6850 RPM.
My issue is this...the HP ran up hard to 5200 rpm and was making right around 300 hp at this point then by 6200 it had jumped up to the mid 330s rolled off flat and only gained 2-3 hp by the peak and never fell off. The graph was not smoothed so I wasn't getting visible float and she pulled hard all the way to 7k.
I took it to the track later that day and could not get it to stick out of the hole. It was the first night the track was open and I was having issues keeping the tail end from walking out from under the truck for a proper burnout. The Hoosier DR2s did get me two 1.90 60' spinning hard but I had to set my shift points VERY early to get a full pass. My best run shifting at 5600 rpm was 13.14@105 with a 2.185 babying it out of the hole so it wouldn't spin.
I will eventually be sending the 243s and Vic to AI for port work but I'm curious about that flat HP curve...any ideas?
03-12-2018, 01:05 PM
#3
I used the FOD to do the dyno tuning. I have a much better filter for normal driving but it's more restrictive. During tuning we gained across the board so it wasn't just reacting in certain RPM ranges as much. It was fat down low so we pulled some fuel and it gained everywhere so we started balancing fuel and spark a bit and I was happy with the last pull. I have no doubt there is more to be had but 7 pulls felt like a good stopping point for the day.
03-20-2018, 08:26 AM
#4
Might have figured this out...it could also explain why it pulled flat and steady...TRANSMISSION SLIP! I took it out for a spin and made a couple passes and it felt like I blew the tires off from a dead stop but I noticed it went perfectly straight and didn't leave any black marks on the road. My cousin actually thought this while we were dyno testing.