Gotta question about NL Converter Coupling

[TT/Ameasap]

Do you want to have the coupling occur where the RPM's are there the longest?

Take for instance:
PTC nl 9.5 that couples at 5300-5400. You wouldnt want it to couple at the max rpm because you are only there for a split second, nor minimum for shifts. So would you want it where its creeping to take advantage of the coupling effect?
Just trying to understand where the coupling range should be as a rule of thumb. I want to get every bit of HP to the ground this season.

 

[bison]

You want it to flash where the highest mass flow is occurring. This way the converter has to work and will keep the engine rpm at flash longer and achieve the most acceleration. The gearing plays a big role in getting a car down the quarter. The taller the gearing and the more torque the harder you work the converter Murder the converter through the 330' with a correctly setup car and you will usually wind up at the top of the food chain.


Sent from my iPhone using Tapatalk

 

[dank GN]

I Belive you want to couple where your peak torque is made

 

[TT/Ameasap]

So my cars peak power is at 5800. My converter is coupling at 5300. Turn your speakers up and listen to my car. I go from 1st (tranny brake) to 3rd and have the tranny shift by itself. The converter is coupling hard enough to hold the rpm and shifts at 5300. Notice my SES light is programmed to come on at 5500 rpm.

 

[Dusty Bradford]

You want it to flash right around peak tq. I'd work with the trans a little to get the shift points up if you want it to shift automatically. This will allow it to shift at 5800, then fall back to 5300. I don't remember what cam you have but keeping the motor falling back into the 5100-5300 range is probably where you want to be.

 

[TT/Ameasap]

You want it to flash right around peak tq. I'd work with the trans a little to get the shift points up if you want it to shift automatically. This will allow it to shift at 5800, then fall back to 5300. I don't remember what cam you have but keeping the motor falling back into the 5100-5300 range is probably where you want to be.

I bought a ratchet shifter to shift it in the range I want and will install it in a couple of days.
Here are the specs of the cam shhhhhhh.....Dont tell anyone...lol

 

[TT/Ameasap]

Dusty,
How much more power do I need to get the converter to tighten up from 1/8 to 1/4?
And are percentage numbers that are quoted (5-6%) at max power from above?

Also looks like my slippage is 10.3%

 

[TT/Ameasap]

TTT
Anyone

 

[GNVYUS 1]

What is your tire height, rear gear ratio, mph and trap rpm?

If you're seeing 10.3% with accurate numbers above, it could be the converter and trans slipping in combination. A fresh trans couples better so it might not be just the converter slipping.
What converter do you have?

 

[TT/Ameasap]

30'' 3.54 124 and 5500
Tranny is fairly new with all good parts. Its the PTC 9.5 NL converter
Thing is... I ran 26-28 mph on the back half with a slipping vigilante converter. No changes..Turned boost down 2-3psi... swapped to PTC and MPH fell off to 22-23mph. But, i gained 4mph in the 1/8th.
Im happy, but I want more on the big end to get me my number.
Just wanting to know when the converter will tighten up on the big end on power.
Or...do I need to get the converter restalled for tighter top end MPH? will that sacrifice the 1/8 tho? IDK
I think it is a balance to get it spot on, but i want to confirm before I hit it with 25-27psi boost.

 

[bison]

With a 30" tire even with 3.54 gear 10% slip isn't bad at all. That would be typical gearing for a 9 sec pass. You're going the wrong way with the boost. It needs to go up. The 330' time is a better indicator of how quick it will be and how well you are working the converter.


Sent from my iPhone using Tapatalk

 

[TT/Ameasap]

330 is 4.231 with PTC vs Vig. 4.424

 

[Dusty Bradford]

Turn the boost up where you want to run the car at and then see what the slip% is. As power increases, slip will also increase a little.

As Bison said. 10% isn't bad. It can be made a little tighter to get closer to the 6% range but you want the boost and rpm up where the car will be ran at in order to evaluate the slip at that power level. As rpm rises, the converter can get tighter.

 

[bison]

If you switched to a 28" tire Id bet slip drops into the 8's at the trap. If the car isn't 60' in the 1.38-1.42 range then you need to raise the launch boost, ramp and dial in the suspension to get the most out of the current gearing. Something good happened if the 330' time is .2 better and you're down 2-3psi boost. Adding the boost back in should help even more.


Sent from my iPhone using Tapatalk

 

[TT/Ameasap]

Thanks for the info Bison and Dusty.
I will post back with higher boost results.

 

[Dusty Bradford]

Bison is correct. The 28' tire will lower slip by reducing the load on the converter and by raising trap rpm.

The reason the slip is higher is because your crossing the traps at nearly where the converter is dropping to on the gear change (flash stall). To reduce slip we need to get the motor away from the flash rpm or by lowering the flash rpm by tightening it. IMO the 30" tires are causing the flash to be a little higher than expected. If your happy with the way the 30" tires are working I'd suggest tightening the converter. Before making a concrete decision I would run the car at 25-27psi where you stated you planned to run it. It's possible that you want to go 400 rpm tighter.

 

[GNVYUS 1]

What stator blade # did PTC give you? Ex. 18 etc.

I came up with 11.8% slippage running the numbers but regardless there's room here to improve.

A 28" at 5700 rpm netting 126 mph needs to be at least 6.5% so this might be your best case scenario. The smaller tire should 1/8 th even better if you can get it to hook. Good Luck

 

[TT/Ameasap]

http://www.4lo.com/calc/geartire.php
If you plug in my numbers (30, 26, 3.54)compared to a 28'' tall tire and stock gearing (3.27) It is nearly the same end ratio. I have way more traction on the street and track with the 30's tho.
like Bison says, I have enough gearing for 9's..... Thats my goal. I just thought my slippage would be less and wondered why my MPH on the big end suffered.

BTW,
Its a 17 blade

 

[Dusty Bradford]

There is room to go another 200 rpm tighter. That's getting into the range few V6's go but each car is different and yours may just want something tighter.

What are your valve spring pressures? Just wondering if you have enough pressure to get the rpm and boost up without the car laying flat.


Posted from the TurboBuick.Com mobile app

 

[TT/Ameasap]

You brought up a good point Dusty.
My valve springs need replaced as they are about 8 yrs old. I need to talk to Mike at Full Throttle to purchase the correct set because this cam needs plenty of spring pressure. However, they do hold up to the 5800 shifts. Maybe if I could get a little more RPM from new stronger springs 6100-6200rpm?