Need help with Boosted 5AT
08-23-2012, 02:35 PM
#1
Need help with Boosted 5AT
So long story short, I upgraded my vortech setup to make more power. Now, when I'm on the dyno getting tuned, we have a 1000 rpm discrepancy and my tuner telling my my trans is probably slipping, also no more HP made but a good amount of TQ.
WTF is going on? I thought trans wasn't supposed to slip until 450hp or so? I'm only making ~370. Now this is on a notoriously low reading mustang dyno, tuner told me I'd be at around 400 on a dynojet but still... I've always taken good care of the trans, changed fluids, monitored temps. I also installed the transgo shift kit which is awesome. Trans only has 60k miles on it, 20k with the shift kit and 10k boosted. I've done a few Auto-X and a track day but I don't really beat the car to death. Everything feels smooth while driving normally and it performs well under load but I have noticed lately that when I start getting on it in first and second gears I hear the engine rev but I just don't feel like I'm moving as fast as I should be.
Just some points to note.
Previous to new mods I was putting down 368hp/281tq @ 7psi in April. Weather was a lot nicer then here in Dallas, TX.
I installed a 2.87 pulley (from 3.12,) a fuel return I put together, and a fluid dampr crank pulley. When I went to get retuned it was a hot day in July, around 100f and I noticed my intake temps were pretty high at 65c. So I know I need to do something about intercooling that air. I'm sure part of the reason it was so hot was because I was now boosting around 10.5 lbs. My new numbers were 366hp/319tq. No idea where all the TQ came from but I was disappointed with the lack of HP gain. Something doesn't seem right to me.
Anyways. Here is my dyno plot with the mysterious missing 1000rpm. Please note, the car was rev'ed out the same in both sessions. The dyno was also calibrated multiple times at 3k rpms so we are attributing that loss to something in the transmission. Hopefully some of the wise experienced folk here could shed some light onto what is going on.
WTF is going on? I thought trans wasn't supposed to slip until 450hp or so? I'm only making ~370. Now this is on a notoriously low reading mustang dyno, tuner told me I'd be at around 400 on a dynojet but still... I've always taken good care of the trans, changed fluids, monitored temps. I also installed the transgo shift kit which is awesome. Trans only has 60k miles on it, 20k with the shift kit and 10k boosted. I've done a few Auto-X and a track day but I don't really beat the car to death. Everything feels smooth while driving normally and it performs well under load but I have noticed lately that when I start getting on it in first and second gears I hear the engine rev but I just don't feel like I'm moving as fast as I should be.
Just some points to note.
Previous to new mods I was putting down 368hp/281tq @ 7psi in April. Weather was a lot nicer then here in Dallas, TX.
I installed a 2.87 pulley (from 3.12,) a fuel return I put together, and a fluid dampr crank pulley. When I went to get retuned it was a hot day in July, around 100f and I noticed my intake temps were pretty high at 65c. So I know I need to do something about intercooling that air. I'm sure part of the reason it was so hot was because I was now boosting around 10.5 lbs. My new numbers were 366hp/319tq. No idea where all the TQ came from but I was disappointed with the lack of HP gain. Something doesn't seem right to me.
Anyways. Here is my dyno plot with the mysterious missing 1000rpm. Please note, the car was rev'ed out the same in both sessions. The dyno was also calibrated multiple times at 3k rpms so we are attributing that loss to something in the transmission. Hopefully some of the wise experienced folk here could shed some light onto what is going on.
Last edited by SexyRob; 08-23-2012 at 02:39 PM.
08-23-2012, 05:27 PM
#5
Probably your trans I take it that 1k drop wasn't there when you dynoed N/A before.
Can't you run a SC NA by taking of belts. If you can see if the dip is still there or maybe your belt is slipping from going to the 2.87. GL with whatever the problem hopefully it's not the trans.
Can't you run a SC NA by taking of belts. If you can see if the dip is still there or maybe your belt is slipping from going to the 2.87. GL with whatever the problem hopefully it's not the trans.
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08-23-2012, 06:12 PM
#11
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Dash is ur tranny still stock? The trans in the market place is already sold. I told him to buy it but he didn't listen. I went 6mt to avoid all the issues
08-23-2012, 06:59 PM
#14
My turbos are likely good for 700+ whp now, so I may end up doing a 6MT swap also. The sad part is I will likely have a slower car!
5AT's seem to be as fast as most 6MTs with 75-100 more whp (on the airstrip 
)
Last edited by rcdash; 08-23-2012 at 07:02 PM.
08-23-2012, 07:19 PM
#15
the car was taken to redline on the dyno on both runs. It wouldn't go any farther. So basically, the car said it was doing 6900 rpm but the dyno said it was doing 5900... dyno was calibrated multiple times and same thing happened. Runs were done in 3rd gear.
08-23-2012, 07:28 PM
#17
Doesn't look like he hit the rev limit though... you SURE he ran it all the way out? The stock tach climbs faster than actual RPMs... mine is at least 500rpm higher than my datalogs on pulls. If you have a video of the pull I'll tell you what RPM you're hitting.
08-23-2012, 07:41 PM
#20
slipping shows up as engine speed goes up while tq goes down. I'm not seeing slip here.
Looking more closely at the two overlays it look like it's not picking up your RPM signal correctly -- the new chart is squished to the left (A/F, boost, tq and all). I'll put money that the dyno run is ****ed. HP is simply a function of TQ x RPM and the tq and boost looks legit.
Looking more closely at the two overlays it look like it's not picking up your RPM signal correctly -- the new chart is squished to the left (A/F, boost, tq and all). I'll put money that the dyno run is ****ed. HP is simply a function of TQ x RPM and the tq and boost looks legit.
Last edited by djamps; 08-23-2012 at 07:49 PM.