Torque Converter/Turbo size

[notlimah]

Starting a new thread so we don't clutter up other threads with this talk and we can have it in one dedicated thread.

 

So @jlbayes you're the second person now I've seen post in the last couple days saying that the lower stall speed was terrible. Seems weird that builders like @Dynamic are using the slightly lower stalls, but the end user isn't happy. Is it just a preference on your end or is it actually performing bad? @Dynamic you said that the slightly lower stall speed was good up to around a 62mm sized turbo right? @jlbayes what size charger and stall speed where you running?!

 

Tagging for sa purposes: @CSM @Silverdodge @Me78569 @JAG1

[Me78569]

RPM IE: exhaust flow is the best thing you can do to get a turbo going.  

 

If you have a tight stall converter then leaving the line you will not build as many RPMS, and thus have less exhaust flow to get a turbo going.  

 

A loose stall converter will allow for more revs off the line and a quicker light of the turbo.  

 

 

Personally I like my super low stall converter, but my VGT spools yesterday compared to bigger turbos.    

 

 

It really comes down to driving style and purpose of the vehicle.  Drag racing and big turbos then you want higher stall in order to light the turbo.   

 

[notlimah]

Yea, I'm not really looking for the speed aspect, more towing and daily driving ability. I definitely trust Jon to set me up with what'll work best for my needs and turbo setup but definitely nice to be more educated on the subject.

 

When you say tight/loose stall are you meaning low/high stall? How differently does the VGT spool compared to similarly sized NON VGT turbo?  

[jlbayes]

I had a low stall approx. 300rpm lower with a combination of 3 different turbos and 2 sets of injectors. First was an he351cw with 7x.010s. Next was a 66/67 with the 7x.010s and then a set of 6x.013s. Last was a 67.7 with the 6x.013s. The lower stall did not fit my driving habits or expectations. Same converter from 500hp to 650hp. The 2nd to the last converter was a 2800rpm goerends with the s467.7 & 6x.013s. It was magical. Ran it with 3 different s400s and was always spot on for where it needed power etc. Current is stock stall with a totally asinine setup lol.

Edited March 24, 2017 by jlbayes

[notlimah]

Again, I'm just quoting what I talked to @Dynamic about but he told me he runs a 2-300rpm lower then stock converter for a stock turbo up to about a 62mm turbo. Anything bigger then that and it gets laggy, and he (I think) recommended a stock stall speed converter or slightly higher for the bigger turbos.

 

He also mentioned that the majority of torque converter manufacturers use the same materials, with possible the exception of Goerend because they have a lot of machinging equipment in house so it's possible they use their own, but the biggest thing to look for in a converter was good welds and a consistent stall speed. That's why he uses the converters he does.

[jlbayes]

And I am speaking from personal experience and perception of what my situation was. Which is going to be different than everyone else's. I was very less than impressed especially when moving to bigger singles. I am not a fan of messing with stall speed any more. At the time (he351) it should have been a good idea. 

[notlimah]

Sorry if I was coming off in a way that said you should feel differently about your experience. Completely understand your point and value your opinion.

 

I was just trying to point out that it seems weird that trans builders and recommending one thing and then guys are running it with sub satisfactory results.

 

Maybe it's just 100% user based opinion and subjectivity regardless of whatever 'the right way' is. Or maybe just an expectation that isn't realistic given the setups? I don't really know as I'm still on a stock trans but in a couple months I'll have a different opinion so I'll chime in with first hand experience then.

 

Again, sorry if I came across like I was trying to tell you your experience should've been any different then it was. 

[Me78569]

5 hours ago, notlimah said:

When you say tight/loose stall are you meaning low/high stall? How differently does the VGT spool compared to similarly sized NON VGT turbo?  

yes tight = low stall loose = high stall. 

 

Well I can drive, tighten then housing, my VGT pretty hard, I don't generally do this as I don't have a driving style that supports needing to be on boost all the time.  

 

People that drive the truck always comment how fast it spools, but if it does or not no idea.

[pepsi71ocean]

I have a 500 lower in mine. And with my smarty, injectors and the way Ive come to drive, I'm happy.

Then again, I question things now about my truck so ymmv

 

 

[CSM]

A converter will stall differently depending on load.  However, it will fall within a general range.  You can think of it as the RPM the converter changes from a turbine that converts a given torque and RPM (horsepower) to a different RPM and mathematically required torque for that RPM (think a variable gear ratio).  After stall, the converter becomes must less like a turbine, and becomes closer to maintaining the same RPM.  There is always some loss, turned to heat, unless you are in lockup.  Old cars prior to the mid 70s didn't have lockup, and always had a few hundred or more difference in RPM after stall from the engine to the transmission input.  

 

To determine what you want requires a little thought.  The basic concept is that you want to look at your power curve, turbo curve, and determine where on the RPM band you want the engine to fully load up.  

 

Examples.  

On a race car, you see converters up to 7000rpm or more.  These allow the engine to flash to high RPM where the engine develops peak horsepower before stalling.  

 

On my truck that is built for daily driving, I wanted a stall that would load the engine at around 1300 RPM, as I felt that I had enough horsepower there to roll off the line.  I don't like it as much now with my bigger turbo, and wish I had a 1700-1800 stall converter. When towing, I don't have enough torque there in first gear sometimes. The engine is held at 1200-1300 RPM which is too low for the turbo to spool without copious amounts of extra energy put into the turbo (fuel = excessive smoke).  

 

On a race truck, you might want a higher stall converter, same as the race car mentioned above. 

 

At low altitude, my setup is perfect.  I don't smoke, I can run the smarty & TST stack hard enough to max my injectors flow, and it runs amazing.  Once I moved back to Colorado however, I have to baby it off the line on hot days as I don't have enough smokeless power to accelerate quickly. If I had a higher stall converter, it wouldn't be a big deal.  

 

Another variable, the rest of the truck should be considered too. If I had 4:10 gears and standard tires, my lower stall converter would be just fine, as the power required to get moving with those lower gears wouldn't be as high. 

 

Last note, I have had an intermittent lockup hunting problem that I haven't yet found the fix for.  The low stall converter is much less violent than a high stall when it moves in and out of lockup.

 

Edited March 25, 2017 by CSM

[Russ Roth]

I have had Jon build 2 trannies for me.  The '01 has a slightly tighter stall with 3.54 gears than the '02 with 4.10 gears.  The gears were not why Jon chose the tighter stall on the '01.  He just felt a looser one would be better and what he now uses.  I forget what the difference was but I am sure he can tell you.  I think I would have liked the tighter convertor for my driving style but there was a year from the time the '01 got wrecked and the time I drove the '02 with upgraded tranny so it might be partly my imagination.        This one seems a bit softer off the line (for me) and it definitely has a bit less pull coasting.  I have a long straight to where I turn to our home road and I usually make a long coast to it.  I know each spot I could kick cruise off and just make the turn almost without braking.  And yes, some if the neighbors don't like that but they could pass if they wanted.     How much the different gearing might have to do with this I don't really know.  So I guess it is not a perfectly straight comparison but it's what I have.  I still have the '01 sitting here but I darn sure am not going to swap converters so you can say I was pretty happy with both of them. I think Jon said he would have used a Goerend  but didn't have or couldn't get one in my time frame.  I think I would have liked that but I sure like what I have.  Hope this is helpful.  BTW, Jon and his family are REALLY nice people too!  

[notlimah]

Thanks for that @CSM makes sense! My thing is I pretty much know the biggest turbo I want to use is a 62/65/12, I'll probably have (soon) no bigger then 285 tires, and 3.55 gearing. Don't tow much and if/when I do it's going to more then likely be less then 10k. So hopefully that's enough info to figure out what a good stall speed would be for me.

 

@Russ Roth appreciate your take on your two trans. Once it gets a little closer I planned on touching base with Jon again to go over some final stuff. I figure stall speed will be one of those topics, but ultimately I trust his judgement on what he thinks is best!

Edited March 25, 2017 by notlimah

[Russ Roth]

You won't be unhappy.

 

[notlimah]

22 minutes ago, Russ Roth said:

You won't be unhappy.

 

 

Yea I can't imagine being disappointed haha!

[CSM]

Hopefully it helps!  Either way, i doubt dynamic will steer you wrong.  

[CTcummins24V]

I like stock stall better, my preference. I had a 15 blade low stall, too laggy and smokey off the line.

http://goerend.com/goerend-triple-disc-torque-converter-5-9l-cummins-1994-2007/

[notlimah]

2 hours ago, CTcummins24V said:

I like stock stall better, my preference. I had a 15 blade low stall, too laggy and smokey off the line.

http://goerend.com/goerend-triple-disc-torque-converter-5-9l-cummins-1994-2007/

 

Thanks! I like how they break out which stall they recommend for each truck, turbo size and elevation. 

 

Where you running a bigger turbo with that converter?

[CTcummins24V]

Ran a 56 and 58mm wheel and cover on a Holset WH1C(old HX35), and 12cm and 14cm turbine housings, as it sits now in a box 58/60/14. Now I have a super b s300 57/65/14, which has more lag than the Holset. 

[notlimah]

hmm weird. That falls right into what they recommend. Was it just a preference thing for you personally or was it performing bad?

[CTcummins24V]

Preference. Once the turbo lights, it's great. Just can't have a heavy foot off the line or I'd black out the intersection. CSM touched on this, with the tighter/lower stall converters, you get fluid coupling and power transfer in low rpms, so the turbo is slower to spool.