Dyno Experts, Please Help Me With Dyno Graph!

uhoh5.0 · Jan 27, 2007

Converter Lock-Up Problems

Got my car dyno tuned today with SCT software. Numbers were 247rwhp and 286rwtq.

Horsepower mods are:
MAC 2.5" Pro-Dumps
C&L Upper Inlet Pipe and K&N Filter System
UPR Catted X-Pipe
BBK Shorty Headers
Ported & Polished Plenum and Throttle Body (70mm FRPP) + Steeda Plate
1/2" Billet Plenum Spacer
4.10s
j-mod Valvebody
Atlantic Coast Converters 3200 Stall Billet Converter
TCI Deep Aluminum Trans Pan (+2 quarts)
Steeda Trans Cooler
Steeda Underdrive Pulleys
180* Thermostat
Car weighs 3300 lbs. (+ driver)
With passenger seat and front sway bar removed, car weighs 3250 lbs

Problem was, when commanded to stay locked, the converter is unlocking in third at around 5250. Maybe this is in anticipation of the shift into 4th gear (O/D) but we had 4th gear locked out. Looking at the dyno graph you can see what I am talking about. Has anyone experienced this? Recommendations???

speed545 · Jan 28, 2007

I would love to help but i cant and love to know.

Did you post on SCT forums? Probably the best place to go.

BurningRubber · Jan 28, 2007

Where did you get it tuned at?

DarrinB · Jan 28, 2007

That sure doesn't look like what you are being told it is. I don't know whats going on, but I don't think thats it.

Darrin

uhoh5.0 · Jan 28, 2007

What does it look like to you Darrin? Not a converter issue?

uhoh5.0 · Jan 28, 2007

I have a wierd power loss in both torque and horsepower between 5250 and about 5600 rpms. I'm not sure what it is, my tuner thought that maybe my torque converter (auto car) is unlocking in third for some reason. But that seems weird that it sorta recovers at 5600. I wonder if maybe that shows the shift into overdrive if they didn't lock O/D out. Or could I have a bad plug, coil, injector??? My air fuel looks pretty good to me though. WTF???

You have to view the attachment at this link:

SaleenGT2001 · Jan 28, 2007

i cant see anything on your graph. its too light

Dirtyd0g · Jan 28, 2007

I highly doubt the converter clutch would start slipping at that rpm and then catch back up. If it were converter clutch slippage caused by the converter it would never catch back up at higher rpms. Maybe it is unlocking and the hydraulics of the converter are catching up with it. You need to measure input rpm and output rpm, the numbers will never match perfectly but they should be close to each other without gaps where they spread apart. That will show you a lockup slippage issue. Do you have a picture of this converter maybe if I had an idea what I was working with I might have more insight. It is highly possible there is something in your tune causing the clutch to disengage. I have seen many issues like that where one minor thing needed to be changed causing this. It's actually pretty common as a tuning problem.
Alan

04YELLOWGT · Jan 28, 2007

If they dont lock O/D the graph looks crazy trust me, so I dont think its that. It could be going rich in that spot. When I first had my car tuned there was a cetain point where it would go super rich and then lean out and I would drop in power.

uhoh5.0 · Jan 28, 2007

I had my converter built by a local converter shop called Atlantic Coast Converters in Conway, SC. Believe it or not it looks exactly like the BC Automotive converters. 11 inch billet cover with big area for clutch (~twice the size of stock) then that funny lookin' ring then a 9" or 9.5" cover. Stalls at about 3200 rpms. Does my dyno graph look like a lock-up issue?

uhoh5.0 · Jan 28, 2007

I wonder if that might be the issue, because my air/fuel starts to fluctuate a little there too. The only weird thing I have is one of the billet blocks on my fuel rail for a fuel pressure gauge, and theres a plug in the other side so you could add a fuel hook up for a wet kit, then the electronic fuel pressure reader goes in the top. It could have a leak at one of those points, maybe thats it???? Fuel pressure would be pretty high at that rpm, and maybe as fuel pressure is rising it springs a tiny leak and that side of the rail gets a lean spot??? Air/fuel goes from about 12.9:1 down to 12.1:1 ???

uhoh5.0 · Jan 28, 2007

The tuner thought it was a lock-up issue, but what if its a fuel issue:

I wonder if that might be the issue, because my air/fuel starts to fluctuate a little there too. The only weird thing I have is one of the billet blocks on my fuel rail for a fuel pressure gauge, and theres a plug in the other side so you could add a fuel hook up for a wet kit, then the electronic fuel pressure reader goes in the top. It could have a leak at one of those points, maybe thats it???? Fuel pressure would be pretty high at that rpm, and maybe as fuel pressure is rising it springs a tiny leak and that side of the rail gets a lean spot??? Air/fuel goes from about 12.9:1 down to 12.1:1 ???

LaserRed01GT · Jan 28, 2007

3 threads going on this huh? You can look at your turbine speed and trans input shaft speed on the scanner. If the TCC solenoid is engaged, they should be very close.

That dip looks very much like the TCC is being momentarily disengaged. If it were a shift into OD, it would be a much larger dip at a steeper angle. There are many things that can cause the converter to unlock in 3rd. Under normal conditions the TCC is locked once the trans shifts into 3rd and stays locked. Try to re-upload your current tune. It's not uncommon for a trans/converter related table to have corrupt values upon the upload of the tune.

Superhereaux · Jan 28, 2007

12.9:1 down to 12.1:1 is actually going richer

blubullett · Jan 28, 2007

Are you guys data logging it while its on the dyno? That should tell you almost everything. If you were leaking fuel you would see it. If your a/f ratio was good i would check to see if its pulling timimg or something. It looks like it recovers at 5600 and when my coils went bad they were just ****ed after 4100, no chance of recovery, so i dont think its your coils. Is the mass air voltage still within specs? You should have a flat a/f ratio so it looks like your tuner needs to work on the fuel table a little bit more.

san~man · Jan 28, 2007

I merged your two threads since they're both related.

uhoh5.0 · Jan 28, 2007

Thanks for the merge!

My tuner said he adds a little fuel in that rpm range to cool the cylinders. So, the fuel block theory is out. This is what he said about the converter:

No I think the reason the fuel flutters is because the converter was unlocking so we didn’t have the load I think the reason the converter was unlocking on the Dyno was because we weren’t accelerating the drum basically the drum was caching up with the wheels and the tyranny thought we where letting off so it released the converter if you notice on the street it doesn’t unlock some times you just get weird things on the Dyno with autos I could definitely feel it unlock on the Dyno

Darin & DirtyDog is that reasonable?

03gtmustang · Jan 28, 2007

uhoh5.0 said:
Darin & DirtyDog is that reasonable?

Hey Sean, its Dan. Youve got the right people helping you here (Darrin and Alan). Im not sure if what your tuner told you is correct or not. I didnt have any problems on the dyno like that. How is it on the street?

LaserRed01GT · Jan 28, 2007

uhoh5.0 said:
No I think the reason the fuel flutters is because the converter was unlocking so we didn’t have the load I think the reason the converter was unlocking on the Dyno was because we weren’t accelerating the drum basically the drum was caching up with the wheels and the tyranny thought we where letting off so it released the converter if you notice on the street it doesn’t unlock some times you just get weird things on the Dyno with autos I could definitely feel it unlock on the Dyno

That doesn't make much sense. The only way the drum "catches up with the wheel" is if you are spinning your tires on the roller. With the RWHP you are making that would be highly unlikely. The AOD-E/4R70W uses an actual clutch in the converter to provide lockup under EEC control, rather than the fixed 60% lockup in third and full lockup in 4th gear system of the older AOD. The 4R70W converter clutch is partially applied or "slipped" under electrical PWM (pulse-width-modulation). There are all kinds of things within the EEC/PCM PWM/trans or tune that can create a momentary partial release of the TCC solenoid. I have seen it all the time with auto cars. Auto cars can act very weird on the dyno and the graphs on auto cars rarely reflect the way the car will actually perform on the street/strip.

Like I said, it would be a good idea, to either to go for a test drive or get it back on the dyno, and monitor the turbine speed and transmission input shaft speed. Then you would know for certain if the TCC was being momentarily disengaged. With my new Snap-On Solus, I can graph those two inputs and you would be able to immediately see if the TCC solenoid was activated or not.

uhoh5.0 · Jan 28, 2007

It doesn't seem to be doing it on the street, but I am fairly new to this to be able to tell for sure. Exactly what would it feel like? Also, my tuner drove the car both by himself and with me and mentioned something to the effect that often times with auto cars some strange things can happen on the dyno but he believed all was good on the street. Could a data log a couple of WOT runs and then would we be able to look at turbine speed and input shaft speed. If we can, that should let us know if the thing is unlocking in 3rd. So if my understanding is correct this is what we want: 1st gear unlocked, shift into second, delay, lock in second, unlock and shift to 3rd, shorter delay then lock in third and stay locked.

***For the converter guys, it sounds more like a tune issue than a lock-up issue. I mean, it may be nothing and just a weird reaction to the dyno, but even with the limited knowledge I have of transmissions and converters I am puzzled as to how the design of the converter would effect this. Alan?

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