224 Stage I Single Turbo Buick V6 does the impossible. 8.76 @ 158.7

[baadgn]

So what's the point you're trying to make? QUOTE]



What we been saying all along throw your sim in the garbage, cause your feeding it info and its spitting out crap. you get my point now!!!

 

[Alky V6]

This way works ONLY if the stall is higher than the transmissions actual rpm drop.
With the ratios a turbo 400 has what would the shift drop to if it shifted at 7000 and it had a lockup convertor?

If you shift at 7000 and it drops to 6600 i would say the TRUE stall is 6600.

A convertor someone calls a 3200, this is the stall i would expect at 0 #s of boost and where it flashes to upon snapping the throttle open.

That same convertor once it comes into full power goes to 5800.
I would say this is a 5800 rpm convertor.

This is the difficult part of pinning down what the stall is with this TC.
At WOT (no nitrous), on the transbrake, I don't care how long you sit on the throttle, the rpm will stay at 3200 rpm and the boost will not build. Without nitrous in the picture, this turbo will not begin to spool until the engine is at a high enough rpm to supply the needed exhaust energy to spool it. That's around 6500 or 6750 rpm, if I remember right.

When the nitrous first hits, the stall jumps to about 4300 rpm where it sits for awhile as the turbine speed catches up. After the turbine speed catches up the rpm ramps up with boost pressure. How high it goes depends on the tuning of the nitrous system. Without the AB, the rpm will settle at around 5300 rpm. With the AB, rpm rises to ? I haven't had the balls to find out where the rpm stops with the present nitrous setup, but it's over 6200 rpm. I can't remember what the boost was at that point, I know it's in one of my other threads, but I do know it's much more boost than I would ever look to launch the car with.
Once the rpm spikes from the nitrous and from the turnoff point of the nitrous, the rpm will slowly drop to about 5400 rpm and 175-180 kPa Map. The only reason it drops is because the BOV and wastegate are causing that. If I clamped the wastegate and BOV shut, the rpm would continue to rise after nitrous shut off and until I got out of the throttle, if I remember correctly. I believe that was how I had the boost control systems setup during the videos showing the anti lag testing.
So you're probably right about this TC stalling way up there in the 6000s. The problem is, if one were to tighten it up, spool time would increase, which is what I don't want, and the target launch rpm would become a moving target for the converter tech. At least now, the rpm and boost can overshoot and I can control it down to a launch target. I would rather have that than strain the powertrain to inch up to the target rpm and boost.

 

[Dusty Bradford]

I don't understand. If I take a car with a stock TC and shift it at 4800 rpm and it drops 1000 rpm, does that mean the stall is 3800 rpm?

At that power level, yes you could say the flash stall of the converter is 3800 rpm. But in the real world it's not going to drop that low.

The converter won't have a constant rpm that it drops. Say 1000rpm

It will not work this way. Shift the car at 5000 and it drops 1000 rpm. Then shift the car at 6000 and it drops 1000rpm. They just don't work like this.

This is how you know the true flash stall of the converter at a given power level. If you shift at 5500 and it drops to 5000, it should also drop to 5000 rpm if you shift at 6000rpm. So the converter in this example has a true flash stall of 5000 rpm at this power level.

 

[it's just a six]

Yes, I have. It's close to .85-.95:1, exhaust to intake.

Ok,in laymens terms,,so your running 31 psi,so your exhaust back pressure is?

 

[Alky V6]

Otto is right. This is what most will call the true flash stall of the converter.

Talking stall's on turbo combinations would be another 20 page thread.

You have the initial flash stall which is where the engine flashes to at the hit of the throttle and the boost reads 0-1#. Then you have the true flash stall which is where the rpm drops to on the gear changes.

Otto made another good point about the gear ratio's. Just the change from a T-400 to a glide will change the rpm drop as well because the amount of ratio change is different. A t-400 will drop less on the gear change than a glide.

Yes. I understand that about the gear changes. True flash stall is new to me, though. I'll have to think about that one. How does that work when you shift at different rpm levels and the amount of drop is different? That's starting to tie in the power curve more, isn't it? And how do you pick what shift rpm to use to determine a true flash stall rpm number since the drop can be different if you pick to shift at say 7000 rpm versus 7400 rpm? Or does it always fall to around a same number? I watch for consistencies like that in the datalogs and I don't recall the shifts always falling to a specific rpm no matter what the shift rpm was.

 

[baadgn]

Otto is right. This is what most will call the true flash stall of the converter.

Talking stall's on turbo combinations would be another 20 page thread.

You have the initial flash stall which is where the engine flashes to at the hit of the throttle and the boost reads 0-1#. Then you have the true flash stall which is where the rpm drops to on the gear changes.

Otto made another good point about the gear ratio's. Just the change from a T-400 to a glide will change the rpm drop as well because the amount of ratio change is different. A t-400 will drop less on the gear change than a glide.

Whats amazing is that less than 50% of the racing world understands this.

 

[Otto J]

Yes. I understand that about the gear changes. True flash stall is new to me, though. I'll have to think about that one. How does that work when you shift at different rpm levels and the amount of drop is different? That's starting to tie in the power curve more, isn't it? And how do you pick what shift rpm to use to determine a true flash stall rpm number since the drop can be different if you pick to shift at say 7000 rpm versus 7400 rpm? Or does it always fall to around a same number?

You would want to figure out where your engine peaks power and make this your shift point for best ET and use this for reference.
I wouldnt think you would have a engine tha makes power to 7000 and shift it a 6500 IF you were going for best ET.

 

[Alky V6]

So what's the point you're trying to make? QUOTE]



What we been saying all along throw your sim in the garbage, cause your feeding it info and its spitting out crap. you get my point now!!!

Well, I'd probably be eager to do that if I hadn't already gone 8s with 1.835/1.5 valved heads after having used the sim exclusively to come up with all the specifications for this engine. Get it, Tony?

 

[Dusty Bradford]

This is the difficult part of pinning down what the stall is with this TC.
At WOT (no nitrous), on the transbrake, I don't care how long you sit on the throttle, the rpm will stay at 3200 rpm and the boost will not build. Without nitrous in the picture, this turbo will not begin to spool until the engine is at a high enough rpm to supply the needed exhaust energy to spool it. That's around 6500 or 6750 rpm, if I remember right.

When the nitrous first hits, the stall jumps to about 4300 rpm where it sits for awhile as the turbine speed catches up. After the turbine speed catches up the rpm ramps up with boost pressure. How high it goes depends on the tuning of the nitrous system. Without the AB, the rpm will settle at around 5300 rpm. With the AB, rpm rises to ? I haven't had the balls to find out where the rpm stops with the present nitrous setup, but it's over 6200 rpm. I can't remember what the boost was at that point, I know it's in one of my other threads, but I do know it's much more boost than I would ever look to launch the car with.
Once the rpm spikes from the nitrous and from the turnoff point of the nitrous, the rpm will slowly drop to about 5400 rpm and 175-180 kPa Map. The only reason it drops is because the BOV and wastegate are causing that. If I clamped the wastegate and BOV shut, the rpm would continue to rise after nitrous shut off and until I got out of the throttle, if I remember correctly. I believe that was how I had the boost control systems setup during the videos showing the anti lag testing.
So you're probably right about this TC stalling way up there in the 6000s. The problem is, if one were to tighten it up, spool time would increase, which is what I don't want, and the target launch rpm would become a moving target for the converter tech. At least now, the rpm and boost can overshoot and I can control it down to a launch target. I would rather have that than strain the powertrain to inch up to the target rpm and boost.

This is the perfect example of why stall ratings for turbo cars are basically useless. You can make it stall whatever you want on the transbrake because the engine just continues to build torque as boost increases. The nitrous just throws another large torque builder into the mix.

This is the battle you will have with this combo. Chances are a tighter converter may slow the car's e.t down unless you leave the nitrous on for a portion of the run.

 

[Alky V6]

Ok,in laymens terms,,so your running 31 psi,so your exhaust back pressure is?

Less than 31. I think. Exhaust back pressure might start to catch up to intake pressure as boost climbs to higher levels. Haven't tested at 31 psi.
There is a thread about my change to the 91mm that details what the test pressures were when I came up with that ratio. I believe the boost pressure was 28 psi in that test.

 

[baadgn]

Well, I'd probably be eager to do that if I hadn't already gone 8s with 1.835/1.5 valved heads after having used the sim exclusively to come up with all the specifications for this engine. Get it, Tony?

No i dont... cause it told you feed more nitrous to your NC convertor and it will work remember ? it was "VERY CLEAR" did you forget that you have a 91 turbo at 31# of boost with 400hp of nitrous running on alcohol feeding them heads

 

[Alky V6]

Whats amazing is that less than 50% of the racing world understands this.

Well then guess what, Tony. I'm in the 50% that doesn't understand. So why don't you just string me up for it and beat me with a stick. Would that make you happy?

 

[Dusty Bradford]

Yes. I understand that about the gear changes. True flash stall is new to me, though. I'll have to think about that one. How does that work when you shift at different rpm levels and the amount of drop is different? That's starting to tie in the power curve more, isn't it? And how do you pick what shift rpm to use to determine a true flash stall rpm number since the drop can be different if you pick to shift at say 7000 rpm versus 7400 rpm? Or does it always fall to around a same number?

Look at your logs. The rpm the engine drops back to should always be the same at a given power level.

If you shift at 7000 and it drops to 6500, it should also drop to 6500 when you shift at 7500. That's because the true flash stall of the converter is 6500. You should also see that the rpm will climb quickly after launch to 6500 before the rpm begins to flatline. This is where the converter is coupling and pulling the engine down. 6500 will be the true stall of the converter.

Keeping the engine in it's rpm range is where the rpm drop comes into play. If the engine needs to turn 7500 to make peak power, a tight converter that only flashes to 6000 will most likely slow the car down. Sure the slip may be low but the car will e.t faster with a looser converter. This could very well be the case with your combo. A converter that slips only 4% will put more power to the tires but it won't necessarily make it faster.

 

[Alky V6]

Talking stall's on turbo combinations would be another 20 page thread.

Hmmm. Maybe Tony has time to explain it to me.

 

[Alky V6]

You would want to figure out where your engine peaks power and make this your shift point for best ET and use this for reference.
I wouldnt think you would have a engine tha makes power to 7000 and shift it a 6500 IF you were going for best ET.

I'm not sure where the power peak is, but I see little difference in the timeslip shifting from 6700 or 7800 rpm. What does that mean? I suspect that means the power band is pretty flat between there.

 

[Dusty Bradford]

To add to the above. When you look at some of my customer logs, the rpm line will seem very flat like the engine isn't accelerating. To the untrained eye you would think the converter is slowing the car down because it's not gaining rpm.

But if you have enough data logging equipment, you will see that the converter is holding the engine in it's usable power range as the converter continually couples. This puts more power to the tires without dropping the engine out of it's power range.

 

[HighPSI]

LOL
Funny you should bring that up. My ecm firmware has been recently upgraded and I think I saw something about a speed sensor input. I'll check it out. Hmmm. I may install that DSS sooner than I thought.

Since I consider myself somewhat of a tuner, I am interested in your ecu. Does it also have the ability to datalog digital or analog inputs? Are you recording backpressure? I'm sure it's posted in one of your other threads, but tell me again what brand it is.

 

[Alky V6]

This is the perfect example of why stall ratings for turbo cars are basically useless. You can make it stall whatever you want on the transbrake because the engine just continues to build torque as boost increases. The nitrous just throws another large torque builder into the mix.

This is the battle you will have with this combo. Chances are a tighter converter may slow the car's e.t down unless you leave the nitrous on for a portion of the run.

I was leaning towards the same conclusion. Thanks for backing that up.

 

[Dusty Bradford]

I'm not sure where the power peak is, but I see little difference in the timeslip shifting from 6700 or 7800 rpm. What does that mean?

What does the rpm drop to on both of these shift points?

Does the boost fall when you shift it higher? Like the engine is having a hard time recovering from a massive rpm drop?

 

[baadgn]

Well then guess what, Tony. I'm in the 50% that doesn't understand. So why don't you just string me up for it and beat me with a stick. Would that make you happy?

What is that you do for a living again.... im sorry that you have other people do for you because of your success. Remember don you started this post so beating is what your going to get a little bit at a time using quotes of your own words. I told some time ago dont try to rub are noses in your crap when are you going to GET IT!!!!!!!!!!!!!!!!!!!!!!!