DTT 89% vs 91%

[jbolt]

To those of you who have been driving with either of these for a while what are your impressions?



Have any of you had both? How do they compare?



I do a lot of stop and go driving and a little towing but not heavy. My conversations with DTT had steered me toward the 89% but the installer I will use is pretty excited about the 91%. He has a setup similar to mine. He did say if I went with larger tires(which I may do in the future) that I would probably be disappointed with the off the line feel of the 91%



Is there anything else I should be aware of or thinking about? Every time I think I've covered all the bases more comes up.



Jay

 

[Power Wagon]

What converter you use would, in my view, depend on your turbo.



If you're running the stock turbo, or even a 16, non-wastegated exhaust housing, I would not use the 91.



If, like me, you have an extra 100 HP and are using t he wastegated 12, the 91 should work great.



The 12 gives you instant boost off the line.

 

[Snow man]

jbolt,from my experiences with both,I would have to say the 89 will be the one. Here's why i say this,you dont have the power to pull thru it at all,they are not much different in feel once you are under way,the 89 will get you out of hole quicker,with your 3. 54's this is important. I had the 89 in my truck with 450hp,and I didnt pull thru it. If you had the 4. 10 gears the 91 would work fine,but out of hole feel isnt going to be as good with the 91.

 

[BushWakr - RIP]

Jay,



My setup is fairly similar to yours. I dyno'd at 225 HP @ 2200 RPM.



Ok, here's my take on this for what ever worth you care to place on it... .



The 91% I had in (at the above HP level) was pretty doggy off the line... further, once it started to roll and I got some RPM on the engine it was hellatiously strong pulling. The main issue I had was two-fold...

1) I did not intend to go for alot more HP mods and was pretty certain that I'd stay right about were I was... maybe a bit of fine tuning, but no more major HP jumps.

So, the engine really got "pulled down" by the 91% for the first 100-150' or so, with WOT. I also had much more smoke on acceleration as well. Once I hit some RPM, ohhhh, say,,, 1450-1550 then it was hang on Nellie !!! Each shift pulled the engine hard to work for a living, so to speak, but it was harder pulling. All this was EMPTY.



2) When I loaded about 1000 lbs. into the back and put it on soft soil to simulate a soft dirt camp spot, the "hold back" was much more noticable. The smoke was more, and it took a few seconds more grunting to get it to roll. I normally carry about 2500-3000 lb. camper, plus a utility trailer grossed out at around 1200 Lbs.

With that much more weight I felt it was too tight a TC for me.

Now, having said all that, I know for sure that had I kept the 91, and 'chased an extra 50-60 HP (maybe 65 HP more) I'd be able to use that TC no problem.



I confirmed that fairly recently when I did some "one time" experiments and "opened up the pump settings and tried a few tricks". By G-Tech accelerometer figures I came up with, approx. 298 HP, nasty smoke, evil EGT's too. ( I would of course work to fix that if I was going to stay at that level) This thing is a bit tricky to set properly and the young fellow that loaned it out to me did the setup. I personally think that a more realistic figure would have been about 270 'ish RWHP.

At that 'test' level of HP, the 91% would have been pretty much perfect for me, no question.



Now I have to also say that Power Wagon has a point too... if you can spool up quicker, you'll hit your power band faster, no question. The thing is I personally believe that I cannot "pull through the 89% TC as it is. It is faster off the line. It lets the engine pick up another, ohhhh..... 125 or so RPM and gets rolling quicker. Once I'm into the 1600 PRM range she's ready to rock N roll, with the range between 1500-1600 being the big surge area for my setup now.



The down side... ... . the 89 does not quite have the "legs" that the 91% does when I hit the upper 60's//70 's MPH. It still pulls darn good, just not quite as firmly as the 91%'er.



Currently, at roughly 2800 RPM in OD, I'm pulling 100 MPH or there abouts. . with my highest top end so far (before jamming out) has been 106 MPH as shown by GPS + speedo.



I guess the whole key to this is a deadly honest completion of the "profile sheet" that is done before any recommendation is made on your particular setup. If you plan to aim for 280'ish HP, go for the 91% you'll be happy as heck, if not, choose the 89% in my opinion.

ps: I have the "towing VB w/firm shifts/medium engagements.



I hope that helps, and if I left anything out, or confused you, drop me a note and I'll try to explain further.







Bob.

 

[Tom W]

I had the 91 and changed to the 89. I have over 400 HP and am very pleased with the 89.

Tom

 

[jbolt]

Bob- that was exactly the kind of feed back I was looking for. Doing a “deadly honest” profile is not so easy. A year ago I had not even considered any “performance improvements”. Today I’m not certain what level of performance I may go after in the future but I do know my general driving habits and that is what I have to go with.



How would you compare the “off the line” feel from the stock trans to your 89%DTT? My trans now (stock) does not begin to pull hard until 2K on the tach but is does not take more than a few seconds to get there. Way better now with the PODs and 16 housing. A 14 mat be in my future….



Tom- What made you change from the 91 to the 89?







I’m 99. 9% sure I will go with the original recommendation by DTT. 89%TC and the towing VB but I will have a chance to test drive a 91% when I drop off the truck.

 

[BushWakr - RIP]

"... How would you compare the “off the line” feel from the stock trans to your 89%DTT? ... "



Jbolt, all I can say is you may as well get out and have a smoke...

There IS no comparison between stock/89%.....



Keep in mind the 89% allows for that bit of extra RPM compared to the 91%... . when compared to the stock TC, not even in the ballpark.....

Even at 1300 RPM the trucks wants to pull. By the time you're going into/past 1500 RPM you're pulling pretty much well beyond the stocker at 2000... at 1600 she's hookin real nice. .

Based on what you've said, I'd really think hard about this though... Bill was positive that I would go for more HP.



One other thing, if you do any towing/hauling at higher altitudes then the 89% is even more applicable.



Seeing what nascar mark, Piers, and one or two others have done for daily HP, I would likely put in the 91% exactly as Bill set it up originally, and make sure I had the extra HP's to use it.

Heck, those guys have kinda drawn me out a bit in terms of experimenting with higher levels myself... . you may well find the same thing down the road, so that's why I say, "deadly honest" profile sheet/usage needs is required.

Currently, for my application, it's pretty much perfect.

Look way down the road, knowing what you do now, seeing the numbers that are coming out of these trucks now, and going up...

I'd like to be running about 275-285 RWHP as a daily driver (that's what my break point would be) then the 91 is right for me.



Bob.