Odd spike in dyno graff.
05-15-2011, 02:29 AM
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Odd spike in dyno graff. I can and will post a pic of it later.
My build is a 408 with a 96mm dbb turbo. Around 4500 to 4800 rpm's we get a 50hp dip in power before it takes off like a scalded ape. We hit over 800 at wheel at 14ish #'s. My injectors are ID1680's and their duty cycle is 68%. The fuel map reads a steady 11.5 11.6 to 7k. We changed a dozen plug setups and my wires are new Taylors. My plug is an Autolite 103 gapped at 22. Any ideas?
My build is a 408 with a 96mm dbb turbo. Around 4500 to 4800 rpm's we get a 50hp dip in power before it takes off like a scalded ape. We hit over 800 at wheel at 14ish #'s. My injectors are ID1680's and their duty cycle is 68%. The fuel map reads a steady 11.5 11.6 to 7k. We changed a dozen plug setups and my wires are new Taylors. My plug is an Autolite 103 gapped at 22. Any ideas?
Last edited by CuNfUzEd; 05-15-2011 at 09:34 AM.
05-16-2011, 05:37 PM
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I know there isnt a knock at that time. We specificly thought we would see one when it hit. I am going to bypass the intercooler and see if it is the restriction. OUr timing on Q16 is 25-26 advance. I make the exact same power at 10#as I do on 21#. At 8# that dip costs me 100rwhp. At 21 it was 10-20 rwhp loss. Oh yeah, by 6k it flat lines at 800.
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05-17-2011, 05:51 PM
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Clutch spin was a consideration. The only issue is it dipped at the exact same spot each time. Also it woud move in the RPM range when we uped the boost. At 21# t was in the 5k range on the tach. At 10 it was 4k. At 15 4500. The chart you see is at 15# and 18#. See how the dip shifted with boost? The 2 that are simialar are 15# and the green is 18.
05-18-2011, 04:49 PM
#13
Does your dataloger show your recorded timing exactly the same as your commanded timing throughout the full pull, specifically that rpm range?
Were you dataloging ALL the timing advance/retard areas?
Engine -> Advance
AFR Advance
Base advance
Coolant Advance
Cranking advance
EGR Advance
IAT Advance
Idle Advance
Ignition timing advance
Smoothing advance
TQ Management advance
Engine -> Retard
Burst Knock Retard
Knock Learn Factor
Knock Retard
Startup Retard
It's worth looking at.
The times I have seen the cam drop power and come back up, it doesn't do it as sharply, it's a bit more smooth and over a longer rpm range, but that's in a NA motor. I can see the spool of the turbo affecting the recovery, but not the drop. I think it would still fall off a bit more smoothly then come back faster do to the turbo spooling, but that is a guess. What rpm is the turbo starting to build boost?
Here is a picture of my old 347 with a Trex/heads. The two graphs are obviously NA, one with an LS6 intake and the other is a Super Vic. But you can clearly see more of a mellow drop off in power. I'm not sure that the cam iss the issue.
Were you dataloging ALL the timing advance/retard areas?
Engine -> Advance
AFR Advance
Base advance
Coolant Advance
Cranking advance
EGR Advance
IAT Advance
Idle Advance
Ignition timing advance
Smoothing advance
TQ Management advance
Engine -> Retard
Burst Knock Retard
Knock Learn Factor
Knock Retard
Startup Retard
It's worth looking at.
The times I have seen the cam drop power and come back up, it doesn't do it as sharply, it's a bit more smooth and over a longer rpm range, but that's in a NA motor. I can see the spool of the turbo affecting the recovery, but not the drop. I think it would still fall off a bit more smoothly then come back faster do to the turbo spooling, but that is a guess. What rpm is the turbo starting to build boost?
Here is a picture of my old 347 with a Trex/heads. The two graphs are obviously NA, one with an LS6 intake and the other is a Super Vic. But you can clearly see more of a mellow drop off in power. I'm not sure that the cam iss the issue.
05-27-2011, 08:18 AM
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the cam is a 654/660 248 252 112+2. I am at 800 rwhp on 14#. I have ported L92's and a FAST 102/102 setup. My turbo is a T6 96mm dbb.
im wondering if my pre turbo exhaust isnt restricting. then headers go into a t4/t6 flange and then into the t6 turbo
im wondering if my pre turbo exhaust isnt restricting. then headers go into a t4/t6 flange and then into the t6 turbo
05-27-2011, 05:23 PM
#17
the cam is monsterous and is probably making life hard on you, but its not causing that hiccup.
tire spin or clutch slip also not an option.
i have little huumps and bumps like that on my graphs, but if the car runs good at the track, has a steady afr, and the timing is smooth PRIOR to the dip, then there really isnt anything to worry about
tire spin or clutch slip also not an option.
i have little huumps and bumps like that on my graphs, but if the car runs good at the track, has a steady afr, and the timing is smooth PRIOR to the dip, then there really isnt anything to worry about
05-28-2011, 12:57 AM
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the cam is monsterous and is probably making life hard on you, but its not causing that hiccup.
tire spin or clutch slip also not an option.
i have little huumps and bumps like that on my graphs, but if the car runs good at the track, has a steady afr, and the timing is smooth PRIOR to the dip, then there really isnt anything to worry about
tire spin or clutch slip also not an option.
i have little huumps and bumps like that on my graphs, but if the car runs good at the track, has a steady afr, and the timing is smooth PRIOR to the dip, then there really isnt anything to worry about
and do cams have a power limit?
05-28-2011, 01:08 AM
#20
I had a turbo Fbody I tuned one time, no matter what I could not make 700 rwhp out of it. It made 699.something numerous times. I tried letting it cool, running it hot, more timing, less timing, etc etc etc. Just wouldn't do it. Then the customer wants to know "you mean to tell me you couldn't crack 700 rwhp?" It was less than 1 hp away! LOL
