Best converter for mpg?
Best converter for mpg? Hey guys, I just bought a '98 Z28 A4 for a daily driver. It has a 2800rpm stall in it, but with a broken lockup switch. The gas mileage freakin' sucks. It's stock as far as the engine is concerned and has 3.08 gears in the back so I just want to get the most efficient converter for it. What do you suggest? Just getting a stocker?
Thanks!
Thanks!
My mileage changed none between stock and TCI 3000, and
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
if your goal is strictly economy then I would say a stall around 1200 rpm heavy duty towing type. If you want performance with a economy compromise get a stall with a very low STR for the best efficency
__________________
My mileage changed none between stock and TCI 3000, and
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
This car does have a moser 12-bolt rear, but with 3.08's. I just bought it so I'm doing the plugs, fuel filter, etc. this weekend so maybe that'll help a little.
At 70mph I'm cruising about 2150rpms. 18" wheels. Does that sound right?
TCC valving, I can pull the belly pan and change all of that, right?
What can I look for with the transmission still in the car? I can pull it, but I would like to have a reason/direction before doing so.
Thanks a lot for the help gentlemen.
My mileage changed none between stock and TCI 3000, and
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
didn't notice anything big going to Fuddle 3500 either (but
did not do the same kind of checking). If you keep your foot
out of it and buy an efficient converter the difference will be
small. Unless it fails to lock. If you romp, you pay.
There is no lockup switch on a '98. Maybe something is holding
off lockup (brake switch, misfires) or maybe the clutch or TCC
valving is toast. It's something that ought to be figured out
before the expense of a new converter.
If the lockup switch is broken (and I don't even know what is "broken" about it, so this may be a stupid question) can it be fixed on the unit or does that usually necessitate a new converter?
Thanks,
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
The PCM commands lock-up which is accomplished by the TCC valve in the valvebody. It may be bad but the problem is probably elsewhere as Jimmy suggested. You can pull the valvebody and inspect it if you know what you're looking for. I assume you don't have a SES light, but you may want to scan the computer for any codes first.
Any stall converter is going to increase slippage which is going to negatively affect mileage (unlocked). I lost 1-2 mpg in town with my TCI 3000 and it seems worse after installing a 3600 recently. An A4 is not going to get anywhere near the mileage of an M6.
Your rpms are high @70 for 3.08's b/c your converter is not locking.
Any stall converter is going to increase slippage which is going to negatively affect mileage (unlocked). I lost 1-2 mpg in town with my TCI 3000 and it seems worse after installing a 3600 recently. An A4 is not going to get anywhere near the mileage of an M6.
Your rpms are high @70 for 3.08's b/c your converter is not locking.
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Okay, I'm starting to get it.
The previous owner had told me that the converter was bad and wouldn't lock up (why the **** he installed it anyways, nevermind...). So I'm going to get the transmission out and get a stocker to throw in there.
Unless anyone can suggest something better than stock with good gas mileage. But the motor is always going to be stock so I'm guessing the converter should be too.
Thanks guys
The previous owner had told me that the converter was bad and wouldn't lock up (why the **** he installed it anyways, nevermind...). So I'm going to get the transmission out and get a stocker to throw in there.
Unless anyone can suggest something better than stock with good gas mileage. But the motor is always going to be stock so I'm guessing the converter should be too.
Thanks guys
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Verdad Gallardo The PCM commands lock-up which is accomplished by the TCC valve in the valvebody. It may be bad but the problem is probably elsewhere as Jimmy suggested. You can pull the valvebody and inspect it if you know what you're looking for. I assume you don't have a SES light, but you may want to scan the computer for any codes first.
Any stall converter is going to increase slippage which is going to negatively affect mileage (unlocked). I lost 1-2 mpg in town with my TCI 3000 and it seems worse after installing a 3600 recently. An A4 is not going to get anywhere near the mileage of an M6.
Your rpms are high @70 for 3.08's b/c your converter is not locking.
Any stall converter is going to increase slippage which is going to negatively affect mileage (unlocked). I lost 1-2 mpg in town with my TCI 3000 and it seems worse after installing a 3600 recently. An A4 is not going to get anywhere near the mileage of an M6.
Your rpms are high @70 for 3.08's b/c your converter is not locking.
Are you getting any check engine lights with codes? This will help us point you in the right direction on what to look at. As far as the switches you are referring to. There is a solenoid that is located in the pump and also another that is called the pwm solenoid that is located in the valve body. Also there are two valves for lock up operation that are used in this trans. One being in the pump that normally does not have any issues and then a regulator valve in the valve body that we do see some issues from time to time. We do replace the oem valve in the valve body in our rebuilds with a valve from transgo.
I'm not getting any check engine lights. I actually spoke to the previous owner again and he told me it's definitely the converter. He bought a 2800 from someone and they failed to mention to him that the lockup portion was broken until confronted later. So I have a stock converter coming from someone else on this board and I will swap it. Hopefully that alleviates the issue. It sounds like it's only going to put my revs around 2k even at 70 so it doesn't sound like it's going to make a big difference as far as fuel economy is concerned.
Going froma 2800 with out lockup to a stocker wth lock up you should get a pretty substaintial milage increase on the highway and around town, I know even with the stock converter if lockup is not working it can cost you 2-3 MPG on the highway.
__________________
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
The thing about the stock converter is that is so pig heavy. It weighs in at about 50lbs., whereas a 10" aftermarket converter comes in about 30lbs. The stock converter has a lot more inertia, but I'd imagine that once you're locked up and rolling, it wouldn't affect mpg appreciably.
