A4 power loss HELP NEEDED
Thread Starter
Registered User
Joined: Mar 1999
Posts: 219
From: Orange, Ca. USA
A4 power loss HELP NEEDED
I'm looking for some guidance here...
Basically I'm losing power thru the trans I think at the TC.
I caluated 9-10 MPH slip using Datamaster and math.
I have reason to belive the clutch packs are holding as
the TCC almost brings the slip to 0MPH for a short time
when applyed at WOT.
How much power HP and TQ could a bad TC or TCpressure
cost a Lt4 on the dyno.
Results 302hp/290tq
Expected 355hp/390tq
94 Firebird
Motor
New crate GM 4bolt shortbock
LT4 hotcam Kit
Lt1 heads/intake ported 2.02 / 1. 60 265@.550 on 350 bore
96 vented opti *new*
42lb accel injectors
BBK headers / Hi flow Cat
all EGR and IAC capped
Trans
4l60e built by me
5gear planets
Trans Go HD shift kit, Vac Mod and NoYoYo (2 washer)
custom sun gear and input drum
ALL Raybestos Blue clutches
3000 stall PI Vig TC
3.73 GM gears
GMPP driveshaft
PCM
done by me tunedbytad@aol.com
less than 2% blms at all times!!!
12.8 AFR on wide band pre cat
36deg spark adv at WOT
same header temp on every tube with in 50deg
Basically I'm losing power thru the trans I think at the TC.
I caluated 9-10 MPH slip using Datamaster and math.
I have reason to belive the clutch packs are holding as
the TCC almost brings the slip to 0MPH for a short time
when applyed at WOT.
How much power HP and TQ could a bad TC or TCpressure
cost a Lt4 on the dyno.
Results 302hp/290tq
Expected 355hp/390tq
94 Firebird
Motor
New crate GM 4bolt shortbock
LT4 hotcam Kit
Lt1 heads/intake ported 2.02 / 1. 60 265@.550 on 350 bore
96 vented opti *new*
42lb accel injectors
BBK headers / Hi flow Cat
all EGR and IAC capped
Trans
4l60e built by me
5gear planets
Trans Go HD shift kit, Vac Mod and NoYoYo (2 washer)
custom sun gear and input drum
ALL Raybestos Blue clutches
3000 stall PI Vig TC
3.73 GM gears
GMPP driveshaft
PCM
done by me tunedbytad@aol.com
less than 2% blms at all times!!!
12.8 AFR on wide band pre cat
36deg spark adv at WOT
same header temp on every tube with in 50deg
Last edited by TurboSS; Apr 21, 2003 at 09:03 PM.
Thread Starter
Registered User
Joined: Mar 1999
Posts: 219
From: Orange, Ca. USA
Injuneer
This is way beyond a basic bolt on user question
A good understanding of Datamaster, the 4L60E and automotive math is needed to even understand the question.
So on what basis is this a LT1 question not an Advanced question.
TAD
This is way beyond a basic bolt on user question
A good understanding of Datamaster, the 4L60E and automotive math is needed to even understand the question.
So on what basis is this a LT1 question not an Advanced question.
TAD
Thread Starter
Registered User
Joined: Mar 1999
Posts: 219
From: Orange, Ca. USA
"EXPECT" is a heavy word normally i would
just "GUESS" on the cars I tune without expectation
BUT, I built and installed the trans myself
also helped assemble and install the motor
also speced out and installed the ignition
and fuel system.
so the state of the car is 100% KNOWN good
and the combo is PROVEN
I tuned another car with the same exact motor setup with exception of vette exhaust *see pic below*
http://members.aol.com/_ht_a/protool...s/TCDyno01.jpg
currently I suspect 3 items
Bad pump (unlikely since the pressure have been tested to spec)
Bad TC (I want to think that the Vig / PI is not bad from the factory but everybody can make mistakes)
Bad 2/4 servo adjustment (I may have shimmed the 2/4 band too heavy. We plan on running a test and math to calc slip in 2 vs 3 tonight to see if the band is dragging in 3rd. I doubt it since i took digital pictures of the band after the servo install with a screw driver in the play /slop area between the drum and the band.)
TADout
just "GUESS" on the cars I tune without expectation
BUT, I built and installed the trans myself
also helped assemble and install the motor
also speced out and installed the ignition
and fuel system.
so the state of the car is 100% KNOWN good
and the combo is PROVEN
I tuned another car with the same exact motor setup with exception of vette exhaust *see pic below*
http://members.aol.com/_ht_a/protool...s/TCDyno01.jpg
currently I suspect 3 items
Bad pump (unlikely since the pressure have been tested to spec)
Bad TC (I want to think that the Vig / PI is not bad from the factory but everybody can make mistakes)
Bad 2/4 servo adjustment (I may have shimmed the 2/4 band too heavy. We plan on running a test and math to calc slip in 2 vs 3 tonight to see if the band is dragging in 3rd. I doubt it since i took digital pictures of the band after the servo install with a screw driver in the play /slop area between the drum and the band.)
TADout
Last edited by TurboSS; Apr 23, 2003 at 06:45 PM.
Registered User
Joined: Jul 2000
Posts: 520
From: MD
How much play do you have in the band? Should be able to get it to move around a bit, about 1/8” or so.
In theory if you’re datalogging you should be able to measure the difference between the engine rpm and gearing and the speedo output. Really the best way to do it would be to use a dyno equipped to measure slip, like some of the superflows. They measure tire rpm by using an optical sensor and a white line put on one of the drive tires. You should be able to log the difference between what you’re getting rpm wise and what the tire is seeing assuming you take into account the difference in gearing.
With everything working right you should be seeing 5-10% slip with the converter unlocked and 0 with it locked. I suspect that there could be as much as a 2 or 3% error in the speed readings, but anything more then that I would guess would be slippage.
To be honest, I suspect that you’re not getting any responses because more often then not people don’t see what they expect on a dyno and even something like a minor tuning issue or error on the dyno operator’s part could really hurt your final #’s.
In theory if you’re datalogging you should be able to measure the difference between the engine rpm and gearing and the speedo output. Really the best way to do it would be to use a dyno equipped to measure slip, like some of the superflows. They measure tire rpm by using an optical sensor and a white line put on one of the drive tires. You should be able to log the difference between what you’re getting rpm wise and what the tire is seeing assuming you take into account the difference in gearing.
With everything working right you should be seeing 5-10% slip with the converter unlocked and 0 with it locked. I suspect that there could be as much as a 2 or 3% error in the speed readings, but anything more then that I would guess would be slippage.
To be honest, I suspect that you’re not getting any responses because more often then not people don’t see what they expect on a dyno and even something like a minor tuning issue or error on the dyno operator’s part could really hurt your final #’s.
Thread Starter
Registered User
Joined: Mar 1999
Posts: 219
From: Orange, Ca. USA
W6TA
12.8 AFR on the MoTec Wide band and the same EGT within a slim range on every header pipe. 36 and 37 deg timing with no knock or spark retard.
I work with this dyno shop often. The dyno operator has been doing about 30+ pulls a day for 8+ years and has a set of ears and ***-o-meter that is more valuable than any flushmounted DynoJet. He said "I think its the trans."
here is a small snipit of my excel calcs I have been working with from datamaster data
rpm mph logged differential in mph
4225 86.03323324 69 17.03323324
4400 89.59673995 79 10.59673995
4700 95.70560858 85 10.70560858
5100 103.8507668 94 9.850766756
Vig TCC trying to apply
5300 107.9233458 105 2.923345845
5325 108.4324182 110 -1.567581769
5475 111.4868525 111 0.486852547
5775 117.5957212 115 2.59572118
5900 120.1410831 117 3.14108311
Hell a z28 with 3.73's intake and pipes should make more than
290tq!!!
even something like a minor tuning issue
error on the dyno operator’s part could really hurt your final #’s.
In theory if you’re datalogging you should be able to measure the difference between the engine rpm and gearing and the speedo output.
rpm mph logged differential in mph
4225 86.03323324 69 17.03323324
4400 89.59673995 79 10.59673995
4700 95.70560858 85 10.70560858
5100 103.8507668 94 9.850766756
Vig TCC trying to apply
5300 107.9233458 105 2.923345845
5325 108.4324182 110 -1.567581769
5475 111.4868525 111 0.486852547
5775 117.5957212 115 2.59572118
5900 120.1410831 117 3.14108311
Hell a z28 with 3.73's intake and pipes should make more than
290tq!!!
Last edited by TurboSS; Apr 25, 2003 at 01:54 AM.
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