Car seems to be consistently down 25-30rwhp
05-12-2014, 09:19 AM
#1
Car seems to be consistently down 25-30rwhp Since last year my car has slowed down considerably in the 1/8 and 1/4.
Was running consistent 7.4-7.5@93-94 mph and 11.6-11.7@114-115 mph (with a slight rev limit bounce on the 2-3 shift).
In similar (and several times in better) DA it is now down to 90-91mph and 111-112 mph.
So far I have changed:
freshened up 4l60e with new band, 3-4 clutches, pump
rebuilt Yank SS3600
new Tooley valvesprings
new front o2 sensors (delphi)
new TR55 plugs gapped at .050"
cleaned MAF and gigantic cone filter
double checked tune for 12.7 afr and 27.5* timing, no KR
replaced Everstart battery with a Optima yellow top
I did a compression test and my lowest was 185, highest was 200, and all the others were 195. Engine had a similar pattern to this last time I checked it several years ago.
Aside from cutting open my filter on the next oil change and looking for metal from a cam going flat, I am about out of ideas here. Car feels fine and shows no signs of anything wrong, doesn't even have a noisy valvetrain. Fuel mileage is still good and no excessive blowby is getting caught in my catch can.
The car has recently started blowing enough oil mist from the filler neck area to make the valve cover and inner fender a little damp but not severely. Could this be an indication of something? The filler neck is on the passenger side of the engine which is also the side with the lowest compression cylinder (2nd from the front). The rear cylinder on the same side had minor deposits on the fresh plug. My fuel rail is flipped so fuel enters from the passenger side.
The only other change made to the car from when it was running good until now is I swapped hoods. Old hood had the cowl induction area cut open to allow air in, new hood is blocked off like they were from the factory because I haven't had time to cut it out yet. I seriously doubt this could be a problem but at this point I am open to any ideas.
Only other idea I have is maybe too much timing chain slack is letting the cam retard.
Was running consistent 7.4-7.5@93-94 mph and 11.6-11.7@114-115 mph (with a slight rev limit bounce on the 2-3 shift).
In similar (and several times in better) DA it is now down to 90-91mph and 111-112 mph.
So far I have changed:
freshened up 4l60e with new band, 3-4 clutches, pump
rebuilt Yank SS3600
new Tooley valvesprings
new front o2 sensors (delphi)
new TR55 plugs gapped at .050"
cleaned MAF and gigantic cone filter
double checked tune for 12.7 afr and 27.5* timing, no KR
replaced Everstart battery with a Optima yellow top
I did a compression test and my lowest was 185, highest was 200, and all the others were 195. Engine had a similar pattern to this last time I checked it several years ago.
Aside from cutting open my filter on the next oil change and looking for metal from a cam going flat, I am about out of ideas here. Car feels fine and shows no signs of anything wrong, doesn't even have a noisy valvetrain. Fuel mileage is still good and no excessive blowby is getting caught in my catch can.
The car has recently started blowing enough oil mist from the filler neck area to make the valve cover and inner fender a little damp but not severely. Could this be an indication of something? The filler neck is on the passenger side of the engine which is also the side with the lowest compression cylinder (2nd from the front). The rear cylinder on the same side had minor deposits on the fresh plug. My fuel rail is flipped so fuel enters from the passenger side.
The only other change made to the car from when it was running good until now is I swapped hoods. Old hood had the cowl induction area cut open to allow air in, new hood is blocked off like they were from the factory because I haven't had time to cut it out yet. I seriously doubt this could be a problem but at this point I am open to any ideas.
Only other idea I have is maybe too much timing chain slack is letting the cam retard.
05-13-2014, 12:21 PM
#4
Sounds like the cam might be an issue. You had one go flat before?
You can check valve lift at the rocker as an easy test if you have a dial caliper.
If that checks out, then your cam is probably okay. I would take it to a dyno, rent it for 3 pulls and get a look at the top end of the graph. See if it's nosing over with valve float or something. The BTR springs and EPS lobes should be happy tho...
You can check valve lift at the rocker as an easy test if you have a dial caliper.
If that checks out, then your cam is probably okay. I would take it to a dyno, rent it for 3 pulls and get a look at the top end of the graph. See if it's nosing over with valve float or something. The BTR springs and EPS lobes should be happy tho...
05-13-2014, 01:30 PM
#5
The car had Patriot golds and I changed to the BTR springs last fall as preventative maintenance but did find 2 crushed valve seals at that time.
The previous cam was a 230/224 comp that went flat due to valve float issues since I ran it too long on beehives. So I replaced the cam, put on the 799 heads, and installed new lifters.
The previous cam was a 230/224 comp that went flat due to valve float issues since I ran it too long on beehives. So I replaced the cam, put on the 799 heads, and installed new lifters.
05-13-2014, 01:50 PM
#6
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if it was my car and the motor seems strong i'd call a trans specialist & see if theres an easy test to perform to verify if your trans or converter are slipping?? just my one cent.
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05-13-2014, 02:20 PM
#8
I can, just hadn't considered it since my last logs were showing good AFRs. Def can't hurt to take a look though, pretty sure my gauge will reach the hood/cowl gap
Dano: car started slowing down then busted the converter/trans pump at an autox, so the converter was sent back to Yank and we rebuilt the trans, it's stronger than ever. I def agree with you though I was assuming it was the trans until we put a new one in it and it ran exactly the same haha
Dano: car started slowing down then busted the converter/trans pump at an autox, so the converter was sent back to Yank and we rebuilt the trans, it's stronger than ever. I def agree with you though I was assuming it was the trans until we put a new one in it and it ran exactly the same haha
05-19-2014, 09:01 AM
#10
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.
05-19-2014, 09:35 AM
#11
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What plugs were you running before? Have you checked all your plug wires? The gap seems a little big, could the spark be getting blown out on the top end? For 1.5 mph it could be any small thing really, or multiple little things that need attention.
05-19-2014, 09:49 AM
#12
Same plugs as before just fresh and actually a tighter gap than before. All the wires were inspected again as well.
And I agree, now that the fuel filter thing has been addressed anything remaining is probably a matter of poor track conditions not allowing a max effort launch. If not I will just run it and start saving for a short block and some more head porting to buy around tax season so I can focus on other things the car needs for now.
And I agree, now that the fuel filter thing has been addressed anything remaining is probably a matter of poor track conditions not allowing a max effort launch. If not I will just run it and start saving for a short block and some more head porting to buy around tax season so I can focus on other things the car needs for now.
05-19-2014, 09:59 AM
#13
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I'd even check tire pressure all the way around, they could have slowly deflated and are just dragging you down. I always check the simplest things first even though they're often skipped over.
05-19-2014, 11:05 AM
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Cool, not too far.
I haven't dyno'd it yet, I wish I had the time. Right now I'm running on a Frost mail order tune that seems pretty damn close. The thing has tons of torque, but seems to fall off pretty quickly above 6,000 rpm. I think this LS6 intake may be choking it...
I haven't dyno'd it yet, I wish I had the time. Right now I'm running on a Frost mail order tune that seems pretty damn close. The thing has tons of torque, but seems to fall off pretty quickly above 6,000 rpm. I think this LS6 intake may be choking it...
05-19-2014, 11:42 AM
#19
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Geoff said that the cam would probably peak around 6500, but mine seems to peak around 6000. With a FAST, larger throttle body, a 3" cat back and/or cutouts I'm sure it would pull a little harder up top. What did your car dyno?
05-19-2014, 01:03 PM
#20
Yeah he said the same to me, peak at 6400-6500 and carry to 6800.
Mine did 389rwhp with the converter unlocked and exhaust capped
NOTE: trans kept downshifting and I didn't have the laptop hooked up so I rolled the throttle in slow and wasn't fully WOT until 5k or so
Mine did 389rwhp with the converter unlocked and exhaust capped
NOTE: trans kept downshifting and I didn't have the laptop hooked up so I rolled the throttle in slow and wasn't fully WOT until 5k or so