Don, a loose stall at 0 psi does not mean the converter will loose efficiency at the top. My PTC converter in the car now will produce 3000 rpm at 0 psi, but at 15 psi its 4500, at 25 psi its 4500 also. Actually it was behind a 1750 hp twin sbc before and it still stalled at 4500 the previous owner said. It all depends on they design the stator. My precision converter would stall at 2400 at 0 psi and go to 5700@25 psi and had a poor non lock up efficiency.
Best Converter
- Thread starter J-B Racing
- Start date
The stator does play a big part on stall characteristics, but is along for the ride soon after launch. Norb, what is the stroke on your engine? Stroke also plays a big part in the stall characteristics of any one particular T/C, and in spool up also. My stroke is only 3.06 making it an even harder choice.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
That's the advantage to this particular PTC converter. It was designed for great spool without sacrificing top end efficiency. It's true, a small ci motor with a large turbo is very difficult to make a converter for but the rpm capability of that set-up will make up for it if the user is willing to turn the rpm. In some cases nitrous or VSC is needed to help the converter when dealing with a very high hp or very small ci V6.
These units are at the point that a 5 degree change in stator or pump angles can really disrupt the workings of the converter. It's that close on both to make them work for the V6 guys. We recently tried just a 5 degree change on a stator for a customer and the car would barely do a burnout.
These units are at the point that a 5 degree change in stator or pump angles can really disrupt the workings of the converter. It's that close on both to make them work for the V6 guys. We recently tried just a 5 degree change on a stator for a customer and the car would barely do a burnout.
With my combo, boost doesn't really start to build until around 3500 rpm. You must understand that the use of nitrous to spool the turbo was always the plan. And after activation of the nitrous system, 16 psi and 4400 rpm is obtained at around .4 seconds. I haven't accurately measured the T/C slip at the end of the run yet. After it's tuned in better I'll take a closer look at it. The last time I tried to calculate it years ago, I believe it was 7 or 8%.
I should make a few things perfectly clear so that everyone knows where I'm coming from. I have absolutely no vested interest to sell anyone on a Neal Chance T/C. In fact I am a distributor for a different company which will remain unmentioned. I'm not here to solicit. I mentioned the quality and engineering that goes into the Neal Chance. I have never seen anything like it in any other T/C. It is clearly built for durability.
A little on my background. I have been in the transmission industry since 1981. I have seen plenty of cut open T/Cs, mainly for failure analysis. Mostly production units, but also racing units. When you compare the construction of a Neal Chance to your typical racing build, it's like looking at a totally different animal.
If anyone is interested, I will remove my Neal Chance and break it open if anyone wants to take a look. We'll need to set a date, because this will only happen once. I have some other units cut open also, that we can look at for a direct comparison. One production unit and another very popular racing unit.
Getting the stall and other characteristics of the T/C honed in is only 1/2 of the consideration when shopping for a T/C. The other half is, 'how long will it last under extreme punishment'.
A little on my background. I have been in the transmission industry since 1981. I have seen plenty of cut open T/Cs, mainly for failure analysis. Mostly production units, but also racing units. When you compare the construction of a Neal Chance to your typical racing build, it's like looking at a totally different animal.
If anyone is interested, I will remove my Neal Chance and break it open if anyone wants to take a look. We'll need to set a date, because this will only happen once. I have some other units cut open also, that we can look at for a direct comparison. One production unit and another very popular racing unit.
Getting the stall and other characteristics of the T/C honed in is only 1/2 of the consideration when shopping for a T/C. The other half is, 'how long will it last under extreme punishment'.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
I agree Don. I'm also here to post facts and share what I have seen and worked with. I have tried alot of converters over the years and have cut them open for inspection when they didn't act like I thought they should. I have been shocked at how plain and oem looking a lot of these racing converters are that we pay good money for.
IMO, PTC and Chance are in a class of their own.
Since you mentioned the extreme punishment? Does your's have a sprag or diode.
Ive seen a 9.5 billet statored PTC foot brake to around 3400 rpm at zero boost and couple really well up top for a slip around 4%. This was in Otto J's TSO car at BG. I was amazed when i saw the logs. Car picked up over 5 mph and rpm's crossing the line were down 600 rpm.
You have to be careful about the factors you're looking at when calculating T/C slippage on the top end. If a particular engine's power starts to fall off fast at, let's say 7500 rpm and is crossing the finish line at 7800 rpm, you can end up with a T/C slippage number that looks incredible. If you take that same engine and you've changed the gearing to cross the finish line at 6500, you will end up with a different slippage reading. Just some food for thought.
Contoured steel stator. Mechanical diode.
Rotating weight will always make a difference. N/C has been offering an aluminum cover with 6 mounting pads for their T/Cs for some time now.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Nice. Have you ever broken the diode?
Nope. Not yet.
I'm serious about pulling out the N/C for inspection. We could make a little 'get to know each other party' out of it. I need to change out the stator to a different one anyway. N/C sent me a stator that will give me a tad more stall. It's the last option before having to change to a negative angled pump. I'd rather stay away from that option. Negative angles make high stalls easier to attain, but efficiency is compromised.
That's an idea. I'm not looking for any freebies. It could be on a loner basis, just for comparison testing.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
I feel the Chance is a great product. There is a good bit of guys around here who have swapped back and forth from Chance to PTC or vice versa. Sometimes one can find something the other can't. They are both top of the line units. I'd be interested in a comparison from the diode equipped unit to a spragless design. In testing, it seems a lot of the design needs to be changed in each unit. Just installing a diode in a spragless designed unit made the car very difficult to get down the track. This particular car was a 2000hp car on a 29.5x10.5 tire. Chance seems to be on top of the diode design while PTC does best with the spragless design. Testing is currently on going in a couple other cars.
Dave Fiscus had just been sent a loaner from Billy T to try in his GT47/88 TSO car. Dave currently has a Chance that they can't seem to find the set-up for. Dave will be calling soon with feedback.
Dave Fiscus had just been sent a loaner from Billy T to try in his GT47/88 TSO car. Dave currently has a Chance that they can't seem to find the set-up for. Dave will be calling soon with feedback.
scot w.
GNSperformance.com
- Joined
- Feb 19, 2005
I think there should be a "opened up" comparison done on the most popular T/C's out there. I think every TB owner out there would like to see pic's of all the most popular makes opened up just to see what they look like inside.
*Example:
*Stock conv-
*PTC conv-
* (real art carr)9" 19930-
* Neal chance-
* Pat's-
* Vig-multi disc-
That would be neat to see! since 95% of the TB owners have never seen the inside of one.
Just an idea!
Scot w.
*Example:
*Stock conv-
*PTC conv-
* (real art carr)9" 19930-
* Neal chance-
* Pat's-
* Vig-multi disc-
That would be neat to see! since 95% of the TB owners have never seen the inside of one.
Just an idea!
Scot w.
Not in this case because gearing stayed the same and the engine was driving through the previous converter a lot harder and it wouldnt couple effectively compared to the PTC even at over 7k. In the post i stated that the engine speed was around 6500 after the swap and mph went up. Engine speed down and mph up tells me converter is working a lot better. If he was to add more rear gear the efficiency probably would have gotten even better. I doubt this TSO engine was out of breath at 6500 rpm. The car was being propelled like a rocket up top after the swap. 147mph before and 152.9mph after the swap.
