Opening day: car still seems down on power (updated post 5/12/14)
02-17-2014, 09:22 AM
#1
Opening day: car still seems down on power (updated post 5/12/14) Went to opening day yesterday. Good news is the 400ft DA is the best we will probably get there all year. Bad news is that the track was green and slick as snot so 60ft was out the window even at half throttle...
My best traps all day though were 91mph 1/8th and 113mph 1/4 in 465ft DA.
This is down from my bests last year of 94mph 1/8th and 114.5 1/4 in 840ft DA.
Car has brand new valvesprings, plugs, and oil change. Wasn't able to log passes due to dead computer battery.
I noticed one o2 sensor has been switching slow so I am going to try replacing those and cleaning the MAF really well. Past that I'm running out of ideas where to look for the lost power unless the engine is just getting a little tired.
The trans was rebuilt but it was built the same as before except for the addition of the HD 2-3 shift valve which allows you to run in 3rd and it holds the over run clutches on. I tried a pass in OD yesterday which will leave them off just to make sure they were robbing power, but the car went slower that way.
I did smoke test the engine while the valvesprings were off and there is 100% no vacuum leak or I'm sure 6psi of smoke would have found it.
The car feels really strong on the street and can't be missing much, but I would like to get back to where it was at least. Best ET before was a pair of 11.67 and 11.68, based on my times and traps yesterday I don't think it would have gone faster than 11.85 even if it had hooked.
My best traps all day though were 91mph 1/8th and 113mph 1/4 in 465ft DA.
This is down from my bests last year of 94mph 1/8th and 114.5 1/4 in 840ft DA.
Car has brand new valvesprings, plugs, and oil change. Wasn't able to log passes due to dead computer battery.
I noticed one o2 sensor has been switching slow so I am going to try replacing those and cleaning the MAF really well. Past that I'm running out of ideas where to look for the lost power unless the engine is just getting a little tired.
The trans was rebuilt but it was built the same as before except for the addition of the HD 2-3 shift valve which allows you to run in 3rd and it holds the over run clutches on. I tried a pass in OD yesterday which will leave them off just to make sure they were robbing power, but the car went slower that way.
I did smoke test the engine while the valvesprings were off and there is 100% no vacuum leak or I'm sure 6psi of smoke would have found it.
The car feels really strong on the street and can't be missing much, but I would like to get back to where it was at least. Best ET before was a pair of 11.67 and 11.68, based on my times and traps yesterday I don't think it would have gone faster than 11.85 even if it had hooked.
Last edited by thunderstruck507; 05-12-2014 at 11:39 AM.
02-18-2014, 11:08 PM
#2
TECH Fanatic
I would like to think it would mph better if the track was good but i dunno. I would just make sure the tune is spot on and make some runs when the track is good and go from there.
02-19-2014, 09:08 AM
#3
New Denso o2 sensors are on the way. I know the last time I did logging my idle fuel trims which were at 2-3% after my last tune touch up have climbed to 10.3-10.5%. So I'm thinking either them or the MAF is have an issue with fueling. I will be putting the wide band back on the car once the new sensors are in.
I am also considering a compression and leakdown, when the heads went on there was one exhaust valve that almost didn't want to lap in correctly and I'm wondering if that one small spot on it might not have become a hot spot that affected sealing? (this might be a stretch, I'm just trying to think of anything possible)
I had the same thought about the track, I know people say if you spin it can actually improve MPH, but I am not sure if that is still true if you have to pedal the car as bad as I was or if it only applies to spinning while maintaining WOT. I was literally having to lift 100% to get the car to shift into 2nd then quickly roll into it once it shifted and hooked so that it didn't downshift back to first. This might be where the problem is more than anything.
I am also considering a compression and leakdown, when the heads went on there was one exhaust valve that almost didn't want to lap in correctly and I'm wondering if that one small spot on it might not have become a hot spot that affected sealing? (this might be a stretch, I'm just trying to think of anything possible)
I had the same thought about the track, I know people say if you spin it can actually improve MPH, but I am not sure if that is still true if you have to pedal the car as bad as I was or if it only applies to spinning while maintaining WOT. I was literally having to lift 100% to get the car to shift into 2nd then quickly roll into it once it shifted and hooked so that it didn't downshift back to first. This might be where the problem is more than anything.
02-19-2014, 09:32 PM
#4
TECH Fanatic
New Denso o2 sensors are on the way. I know the last time I did logging my idle fuel trims which were at 2-3% after my last tune touch up have climbed to 10.3-10.5%. So I'm thinking either them or the MAF is have an issue with fueling. I will be putting the wide band back on the car once the new sensors are in.
I am also considering a compression and leakdown, when the heads went on there was one exhaust valve that almost didn't want to lap in correctly and I'm wondering if that one small spot on it might not have become a hot spot that affected sealing? (this might be a stretch, I'm just trying to think of anything possible)
I had the same thought about the track, I know people say if you spin it can actually improve MPH, but I am not sure if that is still true if you have to pedal the car as bad as I was or if it only applies to spinning while maintaining WOT. I was literally having to lift 100% to get the car to shift into 2nd then quickly roll into it once it shifted and hooked so that it didn't downshift back to first. This might be where the problem is more than anything.
I am also considering a compression and leakdown, when the heads went on there was one exhaust valve that almost didn't want to lap in correctly and I'm wondering if that one small spot on it might not have become a hot spot that affected sealing? (this might be a stretch, I'm just trying to think of anything possible)
I had the same thought about the track, I know people say if you spin it can actually improve MPH, but I am not sure if that is still true if you have to pedal the car as bad as I was or if it only applies to spinning while maintaining WOT. I was literally having to lift 100% to get the car to shift into 2nd then quickly roll into it once it shifted and hooked so that it didn't downshift back to first. This might be where the problem is more than anything.
02-21-2014, 09:56 AM
#5
Pedaling the car wont do the MPH any favors.
If you are going to test the motor, a leakdown test is superior. You can listen to where any leakdown is coming from. All a compression test does is wear the battery down, and run the rings up and down the dry cylinders.
Good luck with it.
Al
If you are going to test the motor, a leakdown test is superior. You can listen to where any leakdown is coming from. All a compression test does is wear the battery down, and run the rings up and down the dry cylinders.
Good luck with it.
Al
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02-21-2014, 12:18 PM
#8
What's the part number on the densos you purchased? I am looking for the four wire flat with a wire long enough to reach my header bung.
Also, I think your problem was the track. Had you spent more time WOT I think your results would've been where you were expecting.
Also, I think your problem was the track. Had you spent more time WOT I think your results would've been where you were expecting.
02-26-2014, 07:13 AM
#10
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hopefully you get it figured out , in october i switch my maf and my car dropped .5mph in the 1/8 and 2mph in the 1/4 i didnt think it would change anything but switched them back and mph went back up next track visit.. i dont have tuning software that would've helped me . just thought i would share my experience .
by the way, your car is pretty bad ***!!
by the way, your car is pretty bad ***!!
02-26-2014, 08:36 AM
#11
New o2 sensors are in and now the car surges at idle constantly. Let it do a quick idle relearn and it still does it.
Haven't had a chance to see why yet but that's fairly frustrating. Hoping it's something as simple as the having received recent idle adjustments in the tune on the old sensors and redoing it with the new ones will correct it.
Haven't had a chance to see why yet but that's fairly frustrating. Hoping it's something as simple as the having received recent idle adjustments in the tune on the old sensors and redoing it with the new ones will correct it.
03-12-2014, 08:35 AM
#16
Well, I don't know for sure I found the problem...but this damn sure wasn't helping anything (the silver spot is where I touched it with my finger):
NOTE I do run a Saxon screen but I popped it out to inspect the sensor, it was put back in after it was also cleaned (it wasn't nearly this dirty for some reason)
After a good cleaning:
It seems like it might have been partially dirty the last time I touched up the tune because now that it is clean my fuel trims are nearly always at negative 13-15%.
Got that cleaned and also installed new Denso o2 sensors which look to be switching great. Now I need to run through the tune to get all my trims back in line and see what she does. Also going to see if I can do a speed density tune for it and see if it speeds up any at the track with nothing but a velocity cone on the throttle body.
NOTE I do run a Saxon screen but I popped it out to inspect the sensor, it was put back in after it was also cleaned (it wasn't nearly this dirty for some reason)
After a good cleaning:
It seems like it might have been partially dirty the last time I touched up the tune because now that it is clean my fuel trims are nearly always at negative 13-15%.
Got that cleaned and also installed new Denso o2 sensors which look to be switching great. Now I need to run through the tune to get all my trims back in line and see what she does. Also going to see if I can do a speed density tune for it and see if it speeds up any at the track with nothing but a velocity cone on the throttle body.
05-12-2014, 11:38 AM
#17
Ended up just correcting the tune.
Went back to the track Friday night and it was still a little slick but on 2 passes I was able to do a quick roll into WOT and cut some low 1.8 60fts. Still only ran a 7.7@91 1/8th and 12.1@112 1/4. DA was ~1650ft.
So it's still down a bit but not quite as bad it seems.
I did do a compression test and came up with 185 lowest, 200 highest, and all the others were 195.
Don't currently have the tool to do a leakdown but I'm going to try to get one.
Went back to the track Friday night and it was still a little slick but on 2 passes I was able to do a quick roll into WOT and cut some low 1.8 60fts. Still only ran a 7.7@91 1/8th and 12.1@112 1/4. DA was ~1650ft.
So it's still down a bit but not quite as bad it seems.
I did do a compression test and came up with 185 lowest, 200 highest, and all the others were 195.
Don't currently have the tool to do a leakdown but I'm going to try to get one.
05-19-2014, 09:02 AM
#18
My fuel system setup would get some "naughty" finger shakes from people because I have a pre filter then my Walbro then the corvette filter/regulator. I do this because it seems there is a LOT of dirty fuel around here.
Pulled the pre filter (large fuel filter for a 05 Mustang GT) and it was difficult to blow through, replaced it and the fuel pump is audibly less strained on prime.
Thinking it might have been partially obstructed last time I did my touch up tune, going to go over it again to double check fuel trims and WOT afr.
I was a little mistaken on my DA calculations as I had accidentally used them for AM instead of PM. The car was actually only around 1.5mph slow DA corrected. I'm also wondering if since my car sucks up hot engine bay air anyway if it just dislikes high humidity DA more than high DA caused by temperature. The other day we had cool air but 85% humidity...the car might just run better with hot air and low humidity.
Pulled the pre filter (large fuel filter for a 05 Mustang GT) and it was difficult to blow through, replaced it and the fuel pump is audibly less strained on prime.
Thinking it might have been partially obstructed last time I did my touch up tune, going to go over it again to double check fuel trims and WOT afr.
I was a little mistaken on my DA calculations as I had accidentally used them for AM instead of PM. The car was actually only around 1.5mph slow DA corrected. I'm also wondering if since my car sucks up hot engine bay air anyway if it just dislikes high humidity DA more than high DA caused by temperature. The other day we had cool air but 85% humidity...the car might just run better with hot air and low humidity.
05-20-2014, 08:44 AM
#20
I could not (long story short even if I had degreed it the car had to go back together) but it ran great with the cam as is. Just in between Spring and Fall of last year it started slowing down.
I changed the fuel filter and it was hard to blow through so I'm going to hope that was part of it, need to check air/fuel again and see if it's still on or needs to be touched up.
I changed the fuel filter and it was hard to blow through so I'm going to hope that was part of it, need to check air/fuel again and see if it's still on or needs to be touched up.