Supra Forums banner

1 - 11 of 11 Posts

·
REVTECHRACING.COM
Joined
·
2,675 Posts
Discussion Starter #1
curious to know how much power is lost on the dyno with a th400? is there a exact % of drivetrain loss to go by?
 

·
TH400 Club
Joined
·
809 Posts
curious to know how much power is lost on the dyno with a th400? is there a exact % of drivetrain loss to go by?
I was wondering that myself, but I assume there is a 3rd factor in the equation. The Stall! My loose unlockable stall will hold down my dyno #s more than a stall that is tight.
 

·
Banned
Joined
·
3,794 Posts
I was wondering that myself, but I assume there is a 3rd factor in the equation. The Stall! My loose unlockable stall will hold down my dyno #s more than a stall that is tight.
bingo, converter plays the biggest role in determining the DT loss.
 

·
REVTECHRACING.COM
Joined
·
2,675 Posts
Discussion Starter #4
bingo, converter plays the biggest role in determining the DT loss.
i have a pi convertter stall is about 3800-3900 ish. manual lockup switch .should i lock it up on the dyno or no need when i stab it in 3rd gear.i have a rev. pattern no engine braking setup on my th400 with a manual lockup switch. no trans brake in use. curious to know about when should i stab it wot on the dyno and if and when to hit the lock up switch????????
 

·
Registered
Joined
·
4,600 Posts
The consensus has always been to not lock our converters under WOT. Never understood it cause the V8 & Buick V6 guys do it all the time.

Just use the dyno for tuning, not to make big numbers. At the track is where the auto will make everyone forget about the lower HP numbers!

Al
 

·
Registered
Joined
·
205 Posts
The consensus has always been to not lock our converters under WOT. Never understood it cause the V8 & Buick V6 guys do it all the time.

Just use the dyno for tuning, not to make big numbers. At the track is where the auto will make everyone forget about the lower HP numbers!

Al
The issue with LU @ WOT is the capability of the LU clutch to hold the power. LU clutches are very small and any converter with a single LU clutch is not going to hold up for very long. I used to see about .2 and 2mph when I locked my 4.1L Buick V-6 in 3rd but it is hard on the LU clutch. The answer is a somewhat expensive multi-disc LU converter.

As for the HP loss using a TH400, ignore the Internet chatter. There probably is not a car that switched to a TH400 that did not go quicker. If you must have LU for cruising or ridiculous 1/4-mile trap speeds, then the TH400 is not for you. The drag race is won off the line and you spend almost 2/3 of the ET getting to the 1/8-mile and that is where the TH400 shines. Not to mention it is probably the strongest passenger car auto tranny in existence.
 

·
REVTECHRACING.COM
Joined
·
2,675 Posts
Discussion Starter #8
well thereason why i ask is when on the dyno recently we seen the line that should be straight across the screen get wavy up top when it should be dead straight across. so either the trans is slipping or the tires grow and bounce around a bit or spin. im no pro dyno man so im kinda clueless.and i lu the converter in the middle of 3rd. plus i want to know the crank hp when using the th400 vs. rwhp. or the % lost through the th400? someone must know the rule of thumb of what is lost.????
 

·
Registered
Joined
·
5 Posts
i dont think you can give an exact number because there are allot of other factors that can play into drivetrain loss like drive shaft and rims. not to mention what clutches you are running in your th400 or if you have a upgraded drum in the th400 so i dont think the question can be answered. with the dyno cuve there could be allot of things that make it wave is the a/f staying the same at that point? what do you have for tire and how much power are you makeing?
 

·
Premium Member
Joined
·
11,271 Posts
You can expect anywhere from 20% to 33% loss depending on the converter. PI converters always lose the most as they are the most inefficient.


Larry
 

·
REVTECHRACING.COM
Joined
·
2,675 Posts
Discussion Starter #11
its a pi converter 3800 .w/ maual lockup
i had my 15" bogarts on that are 28" tall. they were at 25psi. the a/f was dead locked in at 10.8 all the way across. the multiplyer is great. timing was still very conservative at +7 degrees. i wanted a conservative tune since im gonna beat it on the strteet and track were ill load it up more.
i want to know of a more closer% of rwhp loss with a pi 3800 converter please....???
 
1 - 11 of 11 Posts
Top