Picking a New Full Race Stall Speed

[Alky V6]

I know you need less stall when nitrous is involved.

Never mind.

But here's the tricky part. How much less stall?

Not only can you get away with less stall. Also, larger a/r, larger turbine wheel/housing, larger turbo, larger exhaust tubing, bigger cam specs, shorter crank stoke.

In short, nitrous immensely increases the choice that a turbo tuner has at his fingertips.

 

[it's just a six]

But here's the tricky part. How much less stall?

I would say,if you got some money for a converter,make an eductaed guess for a converter with the info you have gathered so far,,,since your combo is completely different than anything out there. Nobody will know what your engine needs.

So if you purchase a converter & it does not work,most places give you a free tweak one time., correct?

If that still does not work,youll be a lot closer to what your needs are for your engine.
Hey it's only money,& looks like you spent a lot anyways.

Racing costs money,& only with some R&D w/different parts will get you what you are looking for.

It's all in the combination, like you said yours is completely different.

You will have to throw down the $$$$ & experiment, sorry to say something you allready know.

Two cents & no offense.

 

[Dusty Bradford]

Now, let's pretend for a moment that you're paying attention to what "I" am trying to accomplish. I want to build as complete of a dialed in fuel map as possible. That takes priority to adjusting the stall. Not that adjusting the stall might become the focus later on down the road, but with the fuel table still being worked on, the priority is to build as complete of a fuel table as possible for open loop operation and for simple research into the affects on the fuel table by an uncommonly large turbo cam and intake and exhaust manifold tuning. Remember, this is a learning and research project.

So, with that primary goal in mind, and having just changed the turbo to a larger turbo, would you suggest taking the opportunity to adjust and study the fuel map with the new turbo and keeping the old TC until the fuel map is dialed, maybe providing more insight into the combination, and then, having a more concrete idea of how changing the TC stall has affected the past work on a dialed in fuel map? Treat this as a college experiment. You're studying the affects of different changes to the engine configuration on a dialed in fuel map.

Remember what I said about basic troubleshooting and tuning procedures 101? One change at a time? I wanted to thoroughly study the affects of one change to the engine configuration, before I decided on the next change, or task.

When I put together an entirely new combo I take a guess at the converter. I get it running, dial in the fuel map down low in loaded situations on the footbrake and then start making transbrake pulls. I can tell right away if the converter is raceable or not. If it's clear the converter is too tight I will swap immediately. Tuning in the fuel map with the wrong converter is a waste of time and $$$ because if the new converter operates in a different area of the map, that area is now irrelevant. I'm not concerned with the fueling needs of an engine in an area it will never operate. I'll put the new converter in, tune it on the brake and then off to the track.

Once a car is tuned and running properly, if the turbo is changed I always suggest running the same converter to get an idea of what the new combo needs. Unless of course it is a huge change and I know right away it will need more stall rpm.

 

[Alky V6]

I would say,if you got some money for a converter,make an eductaed guess for a converter with the info you have gathered so far,,,sense your combo is completely different than anything out there. Nobody will know what your engine needs.

So if you purchase a converter & it does not work,most places give you a free tweak one time., correct?

If that still does not work,youll be a lot closer to what your needs are for your engine.
Hey it's only money,& looks like you spent a lot anyways.

Racing costs money,& only with some R&D w/different parts will get you what you are looking for.

It's all in the combination, like you said yours is completely different.

You will have to throw down the $$$$ & experiment, sorry to say something you allready know.

Two cents & no offense.

No offense at all. To the contrary, I congratulate you. This is one of the most intelligent responses so far.

 

[Dusty Bradford]

So you're saying that if you had seen the initial stall tests with the T76 combination, and knowing nitrous was involved, and not knowing what the rest of the engine performance was going to be, you don't know what you would have thought. It's OK. Who could have known with such a different combination.

What I would have thought about what exactly??

I would know for certain it would be impossible to spool the 91mm without nitrous. I would also have a good idea as to the converter needs to couple enough power to run 9.0's at a given shift rpm.

For example, if a guy with a twin turbo 4.6 mod motor wants to run 8's and shift at 6500 rpm, I know what stall is needed to couple that amount of power at that rpm. Then when he gives me the turbo size info I know right away if he will have trouble spooling.

 

[Alky V6]

When I put together an entirely new combo I take a guess at the converter. I get it running, dial in the fuel map down low in loaded situations on the footbrake and then start making transbrake pulls. I can tell right away if the converter is raceable or not. If it's clear the converter is too tight I will swap immediately. Tuning in the fuel map with the wrong converter is a waste of time and $$$ because if the new converter operates in a different area of the map, that area is now irrelevant. I'm not concerned with the fueling needs of an engine in an area it will never operate. I'll put the new converter in, tune it on the brake and then off to the track.

Once a car is tuned and running properly, if the turbo is changed I always suggest running the same converter to get an idea of what the new combo needs. Unless of course it is a huge change and I know right away it will need more stall rpm.

You're still ignoring the customer's primary concern in the question I presented to you. It is not the question of what you would do in the situation of a simple race car. It is what you would think would be the proper course of action if one was exploring the fuel table of an uncommon engine combination and you wanted to see the affects of that uncommon combination over as much of the fuel map as possible. That would mean being able to put loads on as much of the fuel table as possible.

Pretend that this is not your project and it's the customer's project with his own set of unique requirements for information that he wants to get out of this project.

 

[Alky V6]

What I would have thought about what exactly??

I would know for certain it would be impossible to spool the 91mm without nitrous. I would also have a good idea as to the converter needs to couple enough power to run 9.0's at a given shift rpm.

For example, if a guy with a twin turbo 4.6 mod motor wants to run 8's and shift at 6500 rpm, I know what stall is needed to couple that amount of power at that rpm. Then when he gives me the turbo size info I know right away if he will have trouble spooling.

You're focusing on a very narrow part of the whole project. Again, this started out as a learning project. Another word I should include is research, research, research. The whole target of this project is not to just reach a target ET or MPH. That seems to be the only thing you're focused on here. Part of the target of this project is to research how this odd combination is affecting the fuel table. And not just a small section of the fuel map. As much of the fuel map as possible.

Let me try to put this another way. A simple question to you. If someone wanted to explore as much of his fuel map as possible, would he use a high stall, or a low stall TC? I don't need to know what you would do. Just high or low will do.

And how does nitrous expand that range of the fuel map that can be explored with a low stall TC compared to a high stall TC?

 

[Dusty Bradford]

But what if the final performance of the engine is unclear? This is a combination that no one has ever dealt with. What would you think then? Would you really start changing around TCs where the tune was only to the point of achieving a clean stall test?

Final performance up top or where?

I never like to change a converter based on a simple stall test unless you can tell right away the converter is too tight. If it's one of my converters I would know it would also be too tight up top so would change immediately. Of course WOT data would be great to verify nothing is going on with the transmission causing it to be too tight. For example a plugged trans cooler. Since we're talking about your app specifically I'll address that......

That's why in your case I would want to know the specific details of the converter. By gathering the specific details of your converter I could make an estimate of how much rpm drop you would have. At that point I could say for example, it's going to be slow to spool but will be close to right up top. I could then spec another converter to deliver the same efficiency and rpm drop but spool easier.

 

[Dusty Bradford]

Let me try to put this another way. A simple question to you. If someone wanted to explore as much of his fuel map as possible, would he use a high stall, or a low stall TC? I don't need to know what you would do. Just high or low will do.

That would depend on what area of the map you want to explore. If you can't manipulate the stall rpm as needed to get into the particular area your focused on, the stall would have to be adjusted accordingly.

I see you edited the original....your just wanting me to say a low stall would be better because you can manipulate a tight stall to be looser, but you can't manipulate a loose stall to be tighter:biggrin:

 

[Alky V6]

That would depend on what area of the map you want to explore. If you can't manipulate the stall rpm as needed to get into the particular area your focused on, the stall would have to be adjusted accordingly.

I see you edited the original....your just wanting me to say a low stall would be better because you can manipulate a tight stall to be looser, but you can't manipulate a loose stall to be tighter:biggrin:

Mmmm. Dang, you're getting close.

If you knew that a looser TC would be required, but at the moment you had a tight TC installed, AND THE PRIMARY MISSION was to EXPLORE AS MUCH OF THE FUEL MAP AS POSSIBLE, would you be quick to change out the TC to the high stall? Or,... would you take the time to explore the sections of the fuel map that was still available to you while the tight TC was still in the car?

I only edit posts in an attempt to make this clearer and easier for you to understand the main focus of my project. You're overthinking these simple questions.

 

[Alky V6]

Final performance up top or where?

I never like to change a converter based on a simple stall test unless you can tell right away the converter is too tight. If it's one of my converters I would know it would also be too tight up top so would change immediately. Of course WOT data would be great to verify nothing is going on with the transmission causing it to be too tight. For example a plugged trans cooler. Since we're talking about your app specifically I'll address that......

That's why in your case I would want to know the specific details of the converter. By gathering the specific details of your converter I could make an estimate of how much rpm drop you would have. At that point I could say for example, it's going to be slow to spool but will be close to right up top. I could then spec another converter to deliver the same efficiency and rpm drop but spool easier.

Final performance would be a complete hp and torque curve based on an engine that was optimized.

A stall test is but a small fraction of that curve. Not to mention how a change in nitrous shot size can affect just that small section of the torque curve of an engine.

 

[Alky V6]

That would depend on what area of the map you want to explore.

As much of the map as possible. I know it's impossible to explore the whole map, but again, as much of the map as possible. Fuel map.

 

[Dusty Bradford]

So what are you looking to learn from exploring in a low rpm, moderate KPA area of the fuel map especially if you know it's an area the motor will not operate in?

 

[Alky V6]

Quote from Dusty: So what are you looking to learn from exploring in a low rpm, moderate KPA area of the fuel map especially if you know it's an area the motor will not operate in?

You're right Dusty. Dealing with a high stall TC makes building a fuel map much, much easier. Less area in the fuel map will be passed over by the operating range of the engine. If the hope is to make the fuel table tuning as quick and simple as possible, then the higher the stall the better. As stall speed is increased, less of the fuel map will ultimately need focused attention. This makes the job of the person building the fuel map sooo much easier. Of course, you don't want to go higher with the stall speed than the combination calls for. That just introduces more slippage and waste of energy.

Now, let's pretend for a moment that you're paying attention to what "I" am trying to accomplish. I want to build as complete of a dialed in fuel map as possible. That takes priority to adjusting the stall. Not that adjusting the stall might become the focus later on down the road, but with the fuel table still being worked on, the priority is to build as complete of a fuel table as possible for open loop operation and for simple research into the affects on the fuel table by an uncommonly large turbo cam and intake and exhaust manifold tuning. Remember, this is a learning and research project.
So, with that primary goal in mind, and having just changed the turbo to a larger turbo, would you suggest taking the opportunity to adjust and study the fuel map with the new turbo and keeping the old TC until the fuel map is dialed, maybe providing more insight into the combination, and then, having a more concrete idea of how changing the TC stall has affected the past work on a dialed in fuel map? Treat this as a college experiment. You're studying the affects of different changes to the engine configuration on a dialed in fuel map.

Remember what I said about basic troubleshooting and tuning procedures 101? One change at a time? I wanted to thoroughly study the affects of one change to the engine configuration, before I decided on the next change, or task.

Read the posts.

 

[Alky V6]

I think what's confusing some people is that there is more than one simple agenda connected to my project than just going 'real fast as soon as possible'. I've explained the purpose of my project many, many times, and some are amazingly and narrowly focused on one thing only. This project is a journey, and I plan to learn as much as I can while I'm on it.

 

[Alky V6]

Let me throw a little bit of information at you that I've learned by playing around with a low stall TC. This will go over most of your heads, but maybe someone might find it interesting.

When people talk about long duration, high overlap cams, they usually envision a powerband that starts higher up in the rpm range of an engine. Typically, the useful powerband also becomes narrower as duration and overlap are increased.

When you talk about a long duration, high overlap cam being used in a turbo engine, you envision more turbo lag and more rpm needed to spool a turbo. The natural solution would be to pick a high stall TC to get the engine rpm up in the advertised powerband for the camshaft and help the turbo lag that you tend to get with a long duration, high overlap cam. Also, turbo selection becomes critical to help with the turbo lag problem. Generally, the selection ends up being a compromise between spool characteristics and top end efficiency.

to be continued...

 

[Dusty Bradford]

Quote from Dusty: So what are you looking to learn from exploring in a low rpm, moderate KPA area of the fuel map especially if you know it's an area the motor will not operate in?

Read the posts.

Yea, I read that part and it still is nothing more than a vague answer. You wonder why people get frustrated. Rather than arguing with you I'm trying to see why you are doing certain things.

You give a vague answer and then act like it's much more complicated than we can comprehend so you skip to something else.

Your trying to build a very efficient engine that will also run well at the track..am I right? So spending so much time exploring an area of a fuel map that the engine will never operate in tells you what exactly????

With my own stuff I do worry about how the cam performs and try to use the fuel map as an indicator, but I don't do it on a part of the map where the engine will never operate.

 

[gnxtc2]

Donnie some advice...... Give Dusty a call, give him the answers to the questions he asks, you pay him, he builds you the converter and you install it. After you install it, you say to yourself "I should've gotten the converter from Dusty long time ago." And everyone is happy

Billy T.
gnxtc2@aol.com

 

[Alky V6]

You're right Dusty. Instead of boring everyone, no one's reading this junk anyway, I'm going to pull a Cal and just say, "I've said too much already".

 

[antiquettype]

we're not worthy

I am just not smart enough to understand why a guy would spend so much time and money to have a perfectly calibrated fuel map in areas the engine shouldn't operate in. I know the car shouldn't be on the street, cause a Prius would rear end you leaving a light, so that can't be the reason.
I am just not smart enough to understand why a guy would make insults to people who try to help in a non insulting way (at least initially). Maybe it is not the direction you want to go, you already said you didn't care your car is slow as long as the fuel map was perfect.
I am just not smart enough to understand why you keep posting knowing almost no one here is smart enough to understand.
We all have cookie cutter cars. But I like having a fast car with time for a life other than the darn car. Geez, I use the same round wheels as everyone. I guess when my kids grow up and I retire maybe I will invent a new wheel, maybe a sphere or something, course it wouldn't have much patch on the ground so I could....oh heck, no one is smart enough to follow what I would do.

Dusty, what a professional you are. Your knowledge, dedication and most of all patience is second to none. Keep up the good work.