Anyone know anything about foot stall vs flash stall in a 9" convertor?

[c&cgn]

Just curious....

I just got the tranny done and a 9" convertor installed. I asked for a 3000 stall in the convertor to go with my PTE52 but I'm not sure if I have enough or not. I foot braked the car without adjusting the prop valve and built 5psi on street tires @ 3200 rpm. That seems pretty good to me.The thing is it doesn't seem to spool the turbo much faster than when I was running the D5. (BTW the D5 was toasted and may have been quite a bit looser than most ??)

So my questions is can they adjust the "flash stall" of the convertor without messing with the current foot stall of 3200+ ? I don't want to end up with a slushy 3600 stall convertor or anything like that. So can it be done or is it all related?

 

[Spoolinup]

The torque of your motor will reflect the flash and foot stall. Sounds like you have not recieved the right stall info on that converter. Your already over it on a foot stall and I am sure it flashes a few hundred on top of that.

The 9 inch should of had more stall and more k factor than the d5 so you should notice something better when leaving.

As far as flash adjustment with no change in foot stall, from what I know, not a chance. They are both kindof attached at the hip.

You should move this one to the trans section and maybe Tolle will see it, he can give you the 411.

 

[TurboJim]

GENERALLY:

Foot or brake stall, is the max RPM the motor will go to with the wheels or trans locked.

Flash is how high the converter goes if you nail it.

My 0 pump PI will stall to 3300 on the brake, but flash at 2800-3000 if I whack it at a traffic lighnt

 

[c&cgn]

Originally posted by TurboJim
GENERALLY:

Foot or brake stall, is the max RPM the motor will go to with the wheels or trans locked.

Flash is how high the converter goes if you nail it.

My 0 pump PI will stall to 3300 on the brake, but flash at 2800-3000 if I whack it at a traffic lighnt

I understand what they mean, but it is the overall feel that I am questioning I guess, since I've never had a high stall convertor before.

At this point, I was able to build 5psi @ 3200 rpm (frankly I thought I would have more boost at that rpm but, whatever). I am sure that with slicks on a sticky track and the prop valve adjusted I should be able to get more boost and a couple hundred more rpms, which means my convertor will foot stall to 3400+. It just doesn't seem like it is flashing very high, because it doesn't feel like the turbo is spooling much faster than when the D5 was in there a few days ago. I figured I would be frying the tires left, right and center. Not the case so far. I guess I'll just have to work on my tuning and see if that helps.

 

[Steve Wood]

Clayton, stall is kinda hard to define with a turbo car, IMO. Brake stall has to be whatever rpm you can hold with the brake, obviously but as we know, that can depend upon the torque of engine in the approriate rpm band, condition of the brakes, what kinda tires, etc. If not loose enough to allow the turbo to begin to make power, the engine will not be making enough power to push the converter. Kinda a catch 22. Flash stall is generally a little higher but the two are not independent of one another with regard to the converter construction.

I think the converter is a bit tight. I would like to have seen at least 10# of boost (at 3200-3300)in order to assure quick spooling. In my mind, the converter is not quite loose enuf to let the turbo help make power against the converter and thereby quickly spool when you let go.

 

[c&cgn]

Thanks Steve. That's kinda what I was thinking, although it seems tight whie driving and yet "loose" enough to stall @ 3200+ (so far). I guess if I have the convertor company loosen it a tiny bit it will flash stall better in daily driving and hopefully still end up around 3200-3300 rpm @ 10psi at the track. I'll talk to them on Monday and see what they have to say. Thanks for your help.

 

[TurboBob]

Stall rating.

On a turbo car, specifying stall speed without stating a boost pressure makes it impossible for a converter company to know what you want.

If your converter is stalling to 3200 at 5 psi I will guess that it is about 2600 at Zero psi. So to one guy, it's a 2600 stall converter, to another it's a 3200. To the guy with a trans-brake {trans-break...} it could be a 4000 stall converter .

I would think that's a pretty good converter for your application, stall speed wise. It's about 500 RPM looser than the stocker. For a street car you have good "tightness" and high STR , meaning it feels tight at part throttle. Most guys like this tight feel in a GN.

And, all the different factors of the converter are related, If you want it to flash higher, it will feel looser driving around (more slushy) some guys like it this way (not me).

When I get my TE52 back (getting bearing'd) I may be in the same boat as you. We can compare more notes then (this turbo is new to me, I have a '44 now). I have a Yank 2600 (tight)

BTW, what kind of 'verter is it? Do you have any long-pull WOT DS scans with it (to complete my collection.)?

Bob

 

[REDS HOT AIR]

are you holding it at that rpm?

if you stall it up slowly to that rpm and have 5# if you hold it there while very slowly trying to bring it up more the exaust temp. in the motor should rise and the boost should come up more even at the same rpm.

if you hold the brake and just jab the throttle to that rpm then you actually spray extra fuel on the jab of the throttle that will cool the exaust temp and give you a lower boost till the motor starts to lean back down and exaust temp starts to climb.

yet?

 

[c&cgn]

Bob, it is a TCS 9" convertor. Not the TCS in Arizona, but a local company that has built 7 or 8 of them for fellow club members over the last 7 or 8 years. It is a l/u unit made for l/u on the street and the track.

They said they would build it to a tight 3000 stall but it was never really specified at what boost etc. No 1/4 mile DS runs yet, just testing runs. I've only had the car back since Saturday. It is definately quite tight in street driving but I feel like it is a little too tight maybe because I was expecting it to spool the 52 the same as I was able to spool the TA49 with the D5 (and that was lightening fast). I will be running the car at the track next weekend so I will send you some files when I get back.

Red,

I only attempted foot stalling it twice. Once I was interuppted by a car coming down the road (I was doing it on a seldom used backroad) when I was still slightly in vacuum and around 26-2700 rpm. I figured I would be into the boost by then. The 2nd time I am not sure exactly when it hit boost but i was @ 5psi at 3200rpm. I built it slowly both times.

I have not tried the "launch assist" that is in the Extender chip yet so I may give that a try and see how it goes. Thanks for all of the replies guys.

 

[TurboBob]

Cool. get some data.

Get some DS files locked, unlocked.

Be sure your defaults in DS are 26.1" tire diameter and 3.42 gears.
Launch assist will definately help, hope you have good tires,

Bob

 

[Spoolinup]

It sounded like you had the art carr, but Tcs and a local shop?
I would find out what the k factor is of the converter. This is probably not be as high as the art carr or the vigilante. That converter might be close to the stocks k factor.

 

[c&cgn]

Just went out and has some fun

Got the convertor to stall @ 3550 rpm @ 8psi. Again, on street tires and no adj of the prop valve. The rpms seem kinda high to me for only 8psi. I was able to get 8psi out of my D5 @ 2600-2800 rpm.

What again is the definition of "flash stall" in a turbo car? Is it the rpms after: you start to move, you hit boost, or you hit full boost? That is what I want to check next.

I also ported the whole on my exhaust housing recently, maybe the puck on the THDP is not covering the hole entirely? Dunno.... Either way the car pulls like and SOB @ 23psi and when the convertor locks it feels like another gear

BTW, at one point during the foot stall I noticed that the spark on DS showed 43* I am guessing that the launch assist (which I haven't tried yet) may make a huge difference here. TurboBob ????

 

[Steve Wood]

Flash stall would be the rpm that the converter immediately goes to when you stomp it...it will be before full boost is obtained most likely...if you look at a ds recorded run, you will see that the rpm goes to a point and then hesitates while the car is initially accelerating...at some point the speed catches up to the converter and then the rpm climbs again. I think it is a more fuzzy term with regard to turbo cars and depends a lot on the speed and torque at the time you hit it.

The affect of boost on the torque curves has a large affect on stall.

 

[fubar2.5]

I beleive flash stall can only be measured in 3rd gear at maximum torque.You really need a manual valve body do do this.In other words you drive at say 2500 rpm and mash on it with out it shifting down to get flash stall as this puts the most load on the converter.I suppose you could duplicate this on a tranny dyno.