Street Torque Converter Preference

Lock-up and switch pitch converters are 2 totally different animals. A lock-up converter is still considered a fixed stall converter, as you can not change the actual stall speed under load, you can only lock it up once you reach cruise speed. I'm pretty sure Larry doesn't want to have to hit 5 grand just to leave a stoplight.

 

Larry,

Thank you for starting this conversation. After reading through the 11/12 second combo thread, I felt I had to do some investigating on this subject. Most converter shops can make a converter do similar things, so to me, this isn't about which converter company makes a better converter. This is about the mathematics of the drive train and your operating comfort.

A low stall converter will reach its best efficiency (3 to 5% slip) at lower RPM's.
A high stall converter will reach its best efficiency (3 to 5% slip) at higher RPM's

So today I RANDOMLY called a few converter shops. In specific I asked the three questions below....

1. How will a high stall converter differ on the street at lower operating speeds?
2. How will a high stall converter differ while driving on the highway?
3. How much less efficient will the high stall converter be on the highway?

Consensus answers YOUR CONVERTER COMPANY may have differing opinions! I respect that and would like to hear those opinions.

A street strip converter is a 2800 to 3500 stall whereas a higher stall converter is a 4000 to 4100 stall.

1. It will take more RPM to get the car moving. It may or may not bother you.
2. The high stall converter will be less efficient at mid operating RPMs.
3. To go 55-60 MPH at an engine RPM of 2500 with a low stall converter, it will take an engine RPM of 2600 to go 55-60 with a high stall converter. There is only about a 3% loss of efficiency at this operating range.

NOTE: Fluid temperatures are a concern with higher stall converters therefore a quality transmission cooling system is a must!

Honestly I was shocked to hear there would only be a 3% additional loss. This makes me rethink a few things!!!

 

i have one of jw's 9.5" 2800 converters in mine that repalced an 11" that flashed around 2200. the motor comes up on it really nice but i do notice my gas milage is gone, especially on a highway run, cruising around 75 mph with 3.08 gears and a 26" tall tire.

 

Had I known J,W, was selling converters 4 years ago. I would of bought his. Didn't know till a while after I bought mine. All that being said I read my peak numbers and gears and car weight ect. over the phone to the guy and got a 9.5 , 2800 stall lock up converter. I love it. Touch the gas and it starts to turn the tires at a dead stop. Floor it from about a 15 mph roll and it is instantly burning rubber and just north of 5000 rpm. Waaaay quicker than my old manual 4-speed. Never tried flooring it from a stand still, it would just turn the tires over , hate when that happens:laugh:. Larry,when its time the 9.5 is the way to go. I droped 30 something pounds off the rear at my fly wheel. I have a question , I remember the guy telling me the 9.5 converter would have around 1.5 tq multiplication, The smaller the better it is. Not sure what all that means. Any thoughts ?
What does the TQ multiplication mean and can a 9.5 TQ converter fit a switch pitch tranny? If it wont work on it what would you have to do to get it to work?

 

Thanks Larry. I think I remember the guy telling me 2.5 now that you mention it. It was my first performance TQ converter and still don't know everything about them. :TU:

 

That does sounds awesome Jim. 258mm is about a 10" converter. You are saying that your converter is rated at 4000 stall yet it drives exactly like a stocker on the street? That would be absolutely perfect. I didn't think that was possible

Yes it is! I can very happily say. I was a non-believer myself til I drove the GS and couldn't wipe the smile from my face. :grin::grin:
One of my best friends has a 9 second Chevy 2 and he convinced me to go with Coan at the time. He has a 5000 stall from them behind a 434 stroker SBC, I have been in his car many times and it performs awsome.
My motor starts to make over 500 ft/lbs of torque at a tad under 4000 and that's the info Coan received.
And yes your correct, it's Coan's 10" and I run a TH350 with a full manual/column shift.

 

Has anybody used one of these Hughes converts? I got the converter with a car that I bought that had a new trans and no motor. I have not installed it yet as the car is waiting for the body shop. Do you think it will work well with my engine build? My car is for street use not track. I got a little carried away with the engine build and modifications but it still looks all stock to the eye.

Thanks for any help

Nelson


Hughes Performance Street Master Torque Converters GM25BPO400BP
Torque Converter Usage: Street/Strip Advertised Flash Stall Rating (rpm):2,500 rpm


Engine info: 464
T/A stage 1 high flow severe duty valves and PAC spring replacement. Massaged the heads a little and had them cut for the PC seals.
Exhaust manifolds opened up to 2 . Stamped rocker arm assembly.
T/A SRP 20 CC .038 forged pistons
Update the front and rear seal
Scott Brown cam & lifters 226/240113, roll master timing setup. T/A dual groove cam bearings. Custom fit pushrods, message rods, block, timing cover, oil pump and balanced assembly.
Plugged the heat cross over. Stock intake with some modifications.

Rear: 3.42 posi

 

Yes, $1000 does ring a bell, I'd have to dig a bit to find the exact cost but around a grand sounds about right............and that was 6-7 yrs ago. Not sure what they charge now. But for me it was a no-brainer, I had invested alot of money into the rest of the car and I sure wasn't going to scrimp on the converter. I've had a couple of "crappy" converters over the years and understand how important of a role the converter plays in the combo. Lesson learned for me :grin:

 

A good example of this is guys taking junkard LS engines and running high 8's to low 9's in the quarter mile.

$300-$500 4.8/5.3 LS engine.
$400 or less ECU control system or OE PCM and HP Tuners.
$400 Ebay turbo
$100 fuel pump
$200 4l80e with transgo shift kit
$500 car
$100 8.8 rear axle with welded gears
$1300 torque converter

There is almost 2 seconds to be gained on these combinations from a stock torque converter to the right torque converter.

 

Torque multiplication can vary, it is mostly controlled by the stator its self combined with the blade angle etc. So by changing the stator you can change the torque multiplication, it is not fixed.

There was a time that people would try and figure out the multiplication using what was called the K factor that, and don't quote me on this but I seem to remember it being off a base rating of around 450 for the TH400. This method is pretty much gone by the way side.

---------- Post added at 05:42 PM ---------- Previous post was at 05:37 PM ----------

Coan Torque Converters is consider to be top shelf. Here is the link to there web site. Fill out there spread sheet and see what they come back with. Dyno#s are best if you have them. http://www.coanracing.com/CustomerCarSpecs.asp?Action=FORM

 

The K factor changes with trans type. You would be hard pressed to find anyone that uses it anymore because its pretty much a thing of the pass.

Trying to put a number to how much torque multiplication there is from said torque converter is just a guess game hence why K factor is the thing of the past. Most base there stator combo's etc from data accumulated from past builds/combo's/dyno#s/gear ratio's etc. ie: if you miss the combo you can some times ad more gear to help lock up the converter.

Here is the basic operation of the non lock up torque converter. http://www.tciauto.com/tc/torque-converters-explained/

Just some basic's to think about here also, and it really won't matter to much for street car combo's unless you go to a trans with a lock up converter but and forged vs billet thing is not as much a HP thing as it is really about strength, consistanty and stability in the material and for this reason you will almost never see a forged cover on any high performance or towing application using a lock up converter.

It is fine to use in a non lock up application but that said, in a torque converter that the end user is looking for ET the billet converter will bring a solid foundation with less material because the forged cover has to be thicker to gain its strength. I think one of my converters in the shop is a billet with a inverted cover that saves weight. I can take a pic if you guys are interested in seeing it.

There are many different stator's out there, I remember that the North star stuff was the ticket for a while but I think that kinda dried up. There are different company's stators etc but in the past covers etc have come from the big 3.

There is a Canadian Company called TCS which makes there own covers, stators etc and I remember back in the late 80's early 90 when they made there first steel stator. Most of the light weight drums etc you see out there comes from them.

 

I have the same Coan Maximum Performance converter in my convertible that Jim N has, and my review is identical! Mine is also 6-7 years old and I worked through Mike Phillips to get the converter, as he has a good working relationship with Coan. It wasn't $1000, I think more like $700-$800 at the time. Seems like people like to throw stones at high-priced converter companies, which Coan is, but at least you are going to get a good product. What I've never understood is which someone would spend $15k++ on an engine and fret over few bucks on a converter when we all know a converter can and will make or break a combination (not directed at anyone, just an observation that I've seen over the years).

One thing that I really like about Coan is that profits from their routine work fuels innovation, and some of the parts that are in the TH400 in the "X" that allow it to live aren't made by a small-time trans or converter shop.

There are plenty of outstanding converter shops, big and small, that can and will listen to your needs. I am 100% satisfied with my Coan Maximum Performance 258mm 4000 converter for street and strip use. The fact that neither Jim N. nor I can remember the exact price yet are completely satisfied should raise some eyebrows.

 

Larry,

I know this is going to sound really bad... but i am kind of hoping this does not work for you. I only say this because I have a SP TH400 in the Apollo. If this works, I will most likely be spending more$$$$.

For real though... I believe any converter company can do what you want. Some get it on the first try and some get it on the second try or more. Using a company that has a great deal of data go to on helps.

I would rather pay for a good quality piece, get it right the first time, and be happy. I have never been dissapointed when I purchased the best that i could afford.

For me, Continental Converter in CA and Coan make great product!

Good Luck and Keep us posted!

 

I just recently had my Circle D 245mm torque converter re-stalled from a 2800-3000 stall range to a 3600-3800 stall range. I must say, performance is one thing and driving experience is another. I will share the driving experience differences and the measured performance differences.

The first thing I noticed is that where the tighter stall pulled down the idle from 950 RPM to 750 RPM when putting it in gear the new looser stall did not pull the engine down. When driving at very light throttle they felt pretty much the same. As the throttle application gets more aggressive the looser converter really lets the RPM come up more. Moderate part throttle acceleration that one might consider "normal" driving around town, the tighter converter would find efficiency at about 2400 to 2800 RPM as the car went through the gears while the looser converter would settle in about 3200 to 3500 RPM. Going up hills and overpasses the RPMs were also notably higher.

My car has a lock up equipped transmission (200-4R), so cruising at higher highway speeds (50-80) slip is not an issue when the lock up is engaged. However, without the lock up engaged overdrive is marginalized noticeably by the looser stall converter. This is especially notable on hills, overpasses and at lower speeds. Even the tighter converter has a notable lack of engaged feeling just cruising around compared to a stock torque converter, and as you would assume, the looser converter more so.

Now, the fun part is that the looser converter really flashes up quick on aggressive or full throttle and it keeps the engine right in it's peak power range. Where the old tighter converter had an RPM drop on the shifts of about 1800 RPM, the new looser converter only drops about 900 RPM. So, the engine raps up quick, slams you back in the seat and keeps you pinned there. The car feels much faster and more powerful. My car literally feels now more like it did on the nitrous with the old converter.

At the racetrack, as you would expect, the car is quicker. Fortunately for comparison's sake, the weather and wind were near identical for these two track trips. Here is the breakdown of the gains:
Old 2800-3000 converter:
60 ft 1.64
1/8th 7.19
1/8 MPH 96.7
1/4 11.27
1/4 MPH 120.5

New 3600-3800 converter:
60 ft 1.52
1/8th 7.00
1/8 MPH 96.8
1/4 11.07
1/4 MPH 120.8

The launch at the drag strip is really different. The car has always left strong, but now the RPMs just snap up and it pulls the left front wheel on the launch even with the front shock setting set 8 clicks from loose. The 2 tenths faster times are almost all realized by the 330 foot mark. So, it is really getting out quicker now.

One worry is that the car will loose MPH due to a reduction in efficiency with the looser converter. My MPH did not change at all. I did not measure the new converter slip at the finish line yet, but the old one was 8% on the nitrous.

My summary of the two converters is this: My old Circle D 2800-3000 RPM converter was a GREAT hotrod converter. It was loose enough to the the cam work and get a good strong launch, but tight enough to where it was not overly loose for cruising. The new Circle D 3600-3800 converter is a GREAT street/strip converter. It really delivers nearly all of the ET capability of my combination, but is still streetable enough for the more hard core enthusiasts.

 

Larry, I found my receipt -- on 7-3-2007 Coan's 20320-B Maximum Performance converter through Mike Phillips was $665 to my door. I think the 20320 is now $895 according to Coan's website. If you are considering Coan, you may to call Mike. He'll need a copy of your dyno sheet. 4000 may be too much for your cam, but he or Craig at Coan will be able to tell you that.