what makes a TC 89,91 or 93%?

[Mactruck]

In talking with all the Torque Converter guru's out there I've gotten plenty of recomendations as to what % TC I should go with. I was recomended to go with the 89% because it eliminates lag (especially with 295 tires and a 3. 54) and I'm going with ddII's and an EZ. What is the difference between that and a 91% or a 93%. If I had a 93% I would see more lag but would I see more Higher RPM power? Alot of people that tow have higher % TC's. Wouldn't they want an 89% to eliminate lag? Is the 91 or 93% Stronger?

Help me out here?

 

[CumminsAholic]

Well, I'm not an expert, but... One isn't stronger than the other, they're all the same. You'd want the 89, otherwise when you take off it'll have really bad turbo lag. I haven't driven any of their trucks, so I don't know what the difference is once you get moving, I'm sure it isn't a night and day difference though.

Corey

 

[Fred Swanson]

Kevin, I like your front bumper.

I have a customer that has what your describing. 295's and 3. 54's, DD2's and an EZ. He tows about 8,000 lbs and is running the 91% DTT convertor.



The % is accomplished in part by the pitch of the stator blades. I'm sure you've seen pictures of the different ones out there. The higher the efficiency, the more HP it takes to get moving. With your setup either the 89% or the 91% would work.

Yes, the 89% would allow slightly more slip to get started out easier. The 93% is for the power hungry crowd out there.



In essense, the % is how efficient the TC is in an unlocked only condition under throttle. Hope this helps shed some light.

 

[SlyBones]

Well here is my question while were on the subject. I didnt think that installing a 91% or 93% caused turbo lag. It only makes it more obvious. In some conditions. However the general way people phase things is in terms of it causing turbo lag. So my question is how does installing a 93% TC "CAUSE" turbo lag?



I think of turbo lag as the time between when I mash the pedal and when the boost gauge starts moving. Is this correct?



I am thinking of this from this point of view. Stock TC turbo lag is 3-4 seconds. Install a 89% and it goes to 4-5 seconds, 91% = 5-6 ceconds and 93% = 6-7 seconds. I dont think so. So how is it causing lag?



EDIT, Corey I am not thinking of your response. I have read this many times. And I just finally had to ask.

 

[John]

I have the first production DTT 93% TC in my Ram... and love it!!!! I drove both the 91% TC in a DTT customers Ram and the 93% TC in Bill's Ram (BTW, he reinstalled the prototype 93% TC in his Ram several days before I arrived at his shop because he knew I was really interested in this TC..... how's that for customer service?!!!). Even though he tried his best to talk me out of it, I wouldn't budge. I love that 93% TC and wouldn't even think of going to anything else in my Ram. Keep in mind this choice was based on my specific usage of my Ram, current and proposed power levels, etc.

 

[Lsfarm]

Lag with 89, 91, 93%

Kevin, while I haven't driven the 93%, I have an 89%, and have driven the 91%.



And of course, I've driven the stock version, about a 70%



I'll attempt to explain how I think about turbo lag. With the stock TC, when I mashed the throttle from a standstill, the RPM went up to about 2000, and of course the fueling went up to start creating more power and more RPM. It is the volume of hot, expanding air thet is forced through the turbo while the air is still expanding that causes the turbo to spin. The greater the volume and pressure, the quicker and faster the turbos spins up.



So, when floor the throttle with a stock TC, the rpm goes up to 2000, there is a lot more hot air coming through the exhaust manifold and turbe at this rpm than with the 89% TC.



When I floor the throttle with 89% TC, the engine can only rev to about 1400 RPM, and there is a lot less hot expanding air going through the turbo trying to spin it up. Therefore it takes a second or two longer to get an effective amount of turbo rpm. [eg. Boost]



With an even tighter TC like a 93%, the rpm when the throttle is floored from a stand still will be lower yet, causing more time to get the turbo spinning.



When you add a load, or tall tires, the effect is worse, because it takes more power to get the truck moving, which allows the engine rpm to climb, which generates more hot air for the turbo etc. etc.



So with the original factory TC, I had virtually no lag, the turbo had plenty of hot air to spin it up quickly, with the 89% I have a slight lag, and it is so slight that I have to pay attention or try to create lag to notice it.



Slight throttle with brakes still applied, about 950-1000 rpm eliminates any lag. Any more RPM with brakes applied results in leaving rubber on the pavement!



With a tighter TC, with more lag, I'm sure it would/could be annoying.



With 4. 10 gears, it might be less noticeable.



Clear as mud, right??







I hope this helped, Greg L

 

[Timinator]

So, for conparison, what is the approximate efficiency of the stock TC? Are there also stall speeds that can be compared in a meaningful manner?

 

[chuck3]

Stock TC

I have heard the stock TC is about 68 to 70% eff.

 

[SlyBones]

lsfarm,



I have a 91% TC and am familiar with the effects at a dead stop and mashing the pedal.



I will go with the idea that maybe the fact the engine is not allowed to rev as high makes it so less air is moving and therefore boost builds slower. More input is needed. But I will go with this... .



However the concept that with the stock tc you had virtually no lag, is the point of my question. Are people confusing how fast the truck starts to roll, versus how fast the boost gauge starts to roll?



First like Fred Swanson said, the tighter the TC the more power it takes to get moving. So with the stock TC I recall my truck reving to more like 2400 RPMs or more at WOT. This produces enough power for the 70% TC to start the truck rolling. But this does not mean we have boost and the is no turbo lag. -- Versus now with the 91% tc revs to maybe 1600-1800 or so. Been a few weeks. Anyways at that RPM and having the tigher TC it needs the boost to come in to get enough power to start rolling.



I agree with larger tires and 3. 55/4. 10 prolly make a difference. But it because they make it so you need more or less power, I dont think they cause turbo lag.



So Back to my question, and all this rambling is really meant to build background for my question not state fact, does this mean it CAUSED the lag, or just the fact in emphasized the effects of it.



I would like to add for those with the stock TC, dont let this scare you away. At light throttle the truck rolls out much better than it did stock. Just go read a post a guy wrote a week or so about his first ride in a DTT truck and how well it started moving. Go and check his impressions. Once it is rolling would rather have 70% power transfer or 89%, 91%, etc. There are way too many plus sides and only this lag thing that I can see as a down side. And since I dont race people off the line, and stuff like that I really dont care. -- Maybe once in a great while in rush hour traffic when you are trying to make a quick lane change. But I am learning to deal with it. And I plan on talking to Bill at my next visit. Maybe there are some adjustments we can make.



I use DTT and it will never be anything but DTT.

 

[Mopar-muscle]

i'll give you some impressions , i never really looked at the RPM the truck started rolling and now that i have an HX40 and a 93% TC the lag is pretty big .



i think slybones is correct in his assumption , the lag was always there , the tighter TC just makes it more noticeable .



i towed a bobcat yesterday , i just figured out a 410 RWHP race truck does not make a good work truck , the turbo lag is noticeable and heavy load on the back made it worse . there are a few things i am going to change and Bill tells me a smart controller will help me out the few times i tow something like that .



i had to tow about 6 miles at 30 mph , with 3. 54 gears and LT265 tires it was not easy , if i left it in 3rd the engine would lug and EGT was a constant 900 , if i down shifted to 2nd EGT came down but i couldn't go above 30 , 35 made the truck want to shift into third because of the increased gov pressure , also my gov soleniod is on the fritz , this probably made the condition worse . the truck towed it fine on the highway , though i was being careful not to overheat the trans .



4. 10 gears would have made this a piece of cake , it would have brought the RPM's up to keep the egt down .



after talking to Bill i'm going to put back a 91% TC and i may in the future switch to 4. 10 gears and a taller tire .



mactruck , for you i would go with the 89% . if i wasn't racing this pig i'd switch the the 89% ... oh the stock convertor is about 76%

 

[Lsfarm]

RE turbo lag

Slybones, I agree totally with you on all accounts, and I LOVE my DTT Torque converter and VB.



I was attempting to offer some explaination for the more noticable lag that a lot of people report with the tighter TC.



I do believe that if a person were to measure the time from zero boost to say ten psi boost with a stock 70% TC and compare it to the same interval with an 89% TC, that there would be a measureable difference. I doubt that is it a very big difference, maybe a second or so.



And with the greater power needed at a lower rev to get the truck moving with a little more lag, the perception is that with the higher revs [stock TC] that the truck is moving sooner.



We are discussing semantics her, is it lag?, or truck movement? And this seems to be comparing apples and oranges to me.



I do believe that the turbo does spin up faster with the 2200-2400 rpm blast of hot air when the throttle is mashed with a stock TC, compared to the 15-1700 rpm blast of hot air from the tightly controlled engine with the tight TC.



As I stated, just a slight amount of throttle totally eliminates the lag. And once launched, there is no comparrison, The DTT TC and VB really do the job.



I wouldn't be surprised if Bill K has done some study of this lag discussion, maybe he will chime in here.



If I were asked, I would never say to not go with the DTT mods, but there are a lot of variables about what is expected, how it is driven, and what it it used for.



I'm all smiles with my 'new truck'



Greg L

 

[SlyBones]

You are right I was picking a little on symantics. And I am gonna go with you explanation as being a contributing cause. At least until I get better input. But yours is as good and anyone has offered so far and it makes sense to me, so I will use it.



For me the symantics was important, because I am not going to get rid of my 91%. I am going to focus on things that reduce lag. Like MoparGuy filters with Mallory mounts and stuff like that. Piers says he has some goodies I can get. -- But for me this make the path clear. The lag was there. Lag is now more apparent. My plan is not to remove the item that made it more apparent, but reduce the root cause. The lag that was there in the first place.

 

[Lsfarm]

I agree

I agree: every turbo has lag, by virtue of how it works it has to have some lag.



And I believe that if you take a truck with a tight TC, and run it next to a truck with a stock TC, all else being equal, I wouldn't be surprised that the truck with the most real or percieved lag, [with the tight TC] still beats the stock TC to the 50' point.



For actual getting-the-job-done performance, I believe the DTT TC will move the truck further, faster just because it transfers the power to the ground better.



This would have to be with a light unloaded truck, I'm sure that a heavy load would give the nod to the quicker spooling turbo, but only to about the 50' mark, then look out!!



Another thing about the 'percieved lag'. I think we feel the lag a bit more with the tight TC because we can really feel when the turbo does spool up. With the loose stock TC, the rpm just goes up, the rate of acceleration doesn't seem to change that much with spool up.



When the turbo spools up in my truck, from a standstill, the truck had better be on good pavement and pointed straight, or I'm going to be busy keeping it straight!



I hope Bill K can add some experience and insight to this 'issue'.



Damn I love my 'new truck'!! and no tickets yet!



Greg L

 

[Jim Fulmer]

LS Farm

Like Sly bones said..... Just go read a post a guy wrote a week or so about his first ride in a DTT truck and how well it started moving. Go and check his impressions.



Well that was me, what I did was ride in the installers truck(inarush76)and I'll tell you this his truck will drive(move out) at 1500 like mine does at 2000, normal speed building, but what is even more funny are two things, lockup is a slight option not manditory in the stock case and running through the gears is cool cause it moves through the RPM like a gas motor instead of varring only a few hundred. Mine the way it is right now at a stop mat it and rpm goes to 3k and boost to 30 like that, cool for showing of in a parking lot but that's it, This all makes more since when you hear a car go down the track at 7k and never really changes tone(blowing through the converter) Mines does the same, I will tell you nothing, I mean nothing will change my mind on what to do. My T/Q selection will be based on two things HP present and HP future and recommendations from the bosses.



Jim

 

[Big White Beast]

I got the heavy truck......

10K of Ram and I'll tell you what. I can gaurantee that my truck takes off better with the 89% TC than it did stock. When I hit the gas now I move, when it was stock I hit the gas and crept up to speed. You couldn't even tell when the turbo spooled up only when the TC went into lock up, that was like a power surge.



I posted a while back (So that's what turbo lag is) because it was so noticeable after the transmission mods. It was always there just not noticable and its not like the truck doesn't move till spool up it's just so noticeable when it does. Now when it spools up the power actually goes to the ground instead of just jumping up RPM's.



A word of caution though. When your at an intersection don't let off the brake. I used to on uphill intersections and the truck just sat there. Now it climbs right up at idle. Had a close one right after the install. Now the brake stays firmly engaged.



Garrett

 

[BushWakr - RIP]

I had the great fortune to drive Bill K's truck when he had an 89% TC then a while later the 93% TC. A major difference. With no EZ (I think it was) on the truck hauled apples like crazy with both TC's.

BUT there was a noticeable difference in how quick boost came on because of the tighter 93% TC, it just plain took a bit longer,, not alot, but some.

With his EZ on... . well... just hang on and hope for the best is all I can say. Both TC's hooked up like no body's business. The shifts are firmer, R and D engagement is a bit more severe with the 93%'er and Bill recommended to me, based on my mod's and usage I would be best off with the 89%'er. He felt any tighter would result in 'bogging down' until I gained some RPM.

Now I will say that in relatively stock mode (no EZ) his 93%'er still hauled out big time. I gotta trust (and do) that he would make the right recommendation for my application. He and Stephan both said that if I took the truck up to the next level of enhancements then I might look at the 91 or 93% TC.

He also recommends using neutral when in stop and go traffic to limit heat build-up because these things just want to go all the time.



FWIW



Bob

 

[cullyguy]

According to Bill K a stock TC is about 72% efficent on a 300 HP motor. Measured the way DTT does it. I asked this question on DTT's web site (Trans talk) and this answer is posted there.

 

[HoleshotHolset]

I can vouch for the 93% DTT TC and their good VB. Simply amazing how much different the truck drives... .

Keep your foot firmly on the brake pedal when in traffic... . they just want to go and go and go!!!



Matt

 

[Timinator]

Can you really benefit from one of Bill's TCs if your engine is stock? I have a '95 with 160 hp. Would it bog down too much?

 

[BRoth]

Why change the %

The transfer efficiency of the convertor is based on the stator design but isn't the slippage caused by the power that is being tryed to transfer through it.



If we can determine the amount of power that the engine has prior to installing a certain model stator should we not be able to accomplish a peak or the same percentage of efficiency for all engines.



We work on 3 areas in the stator and they all have a different effect. The size of the window between the stator blades, the angle of the stator blade and the length of the stator blade.



The often called stall speed does not have to effect the % of rpm you are transferring.



Brian@bd-power