no2 to spool turbo

[Alky V6]

I should add something about the engine sim I use. No doubt software cannot always accurately mimic real world, but let me add this about this particular software. Of all the serious engine builders that I have run across that have taken serious time to work with this sim and then compare it to real world engine dyno pulls, it's absolutely amazing to me that every single one was able to come up with at least one instance where the software came to within 5 hp of an actual engine dyno test. I'm talking about an engine that was configured first in the sim and then built according to the specs in the sim, and then put on an engine dyno to measure real world bhp.
Not one builder could say he didn't have an experience like that. Not one.

 

[Dusty Bradford]

Don, Don't forget Titan runs over 60psi on a stock head to make the power they make with a 94mm.

Another good example are pulling tractors. Lots of them still run a stock diesel head but converted to alky. 60-70psi of boost is very common for them.

The reason your combo can exceed the normal hp range of a head with 210 intake flow is because of the bp ratio and alky. I thought that was the whole reason you chose the large turbo was to minimize backpressure. I'm sure Kenny was thinking of an ordinary combo when he stated 1200hp was it for the M&A head. I'm willing to bet he wasn't thinking of an engine on alky with less than 1:1 bp ratio when he made that statement. I think you have plenty of room to raise the boost. Turn the computer off and get to the track

 

[lazaris]

I should add something about the engine sim I use. No doubt software cannot always accurately mimic real world, but let me add this about this particular software. Of all the serious engine builders that I have run across that have taken serious time to work with this sim and then compare it to real world engine dyno pulls, it's absolutely amazing to me that every single one was able to come up with at least one instance where the software came to within 5 hp of an actual engine dyno test. I'm talking about an engine that was configured first in the sim and then built according to the specs in the sim, and then put on an engine dyno to measure real world bhp.
Not one builder could say he didn't have an experience like that. Not one.

But as you said, apparently way off in the cylinder head parameters in your case.

 

[Alky V6]

But as you said, apparently way off in the cylinder head parameters in your case.

But then, how accurate was the flow bench testing??? Garbage in, garbage out. That's something to always keep in mind when working with a simulator.

 

[Alky V6]

Don, Don't forget Titan runs over 60psi on a stock head to make the power they make with a 94mm.

Another good example are pulling tractors. Lots of them still run a stock diesel head but converted to alky. 60-70psi of boost is very common for them.

The reason your combo can exceed the normal hp range of a head with 210 intake flow is because of the bp ratio and alky. I thought that was the whole reason you chose the large turbo was to minimize backpressure. I'm sure Kenny was thinking of an ordinary combo when he stated 1200hp was it for the M&A head. I'm willing to bet he wasn't thinking of an engine on alky with less than 1:1 bp ratio when he made that statement. I think you have plenty of room to raise the boost. Turn the computer off and get to the track

LOL I hear ya.

 

[lazaris]

But then, how accurate was the flow bench testing??? Garbage in, garbage out. That's something to always keep in mind when working with a simulator.

They arent, thats the point....

 

[Alky V6]

They arent, thats the point....

This brings up another interesting anomaly about the sim that I think is very interesting.

Sure. I would expect that the flow numbers for the heads are not perfect. I gave the heads to a fella that usually ports V8 heads. The ports did come out beautiful. From all that I've read about porting techniques, they were all there in these heads. Still, I stuck with the 1.835/1.5 valves.
His flow testing of the heads, I'm sure, did not include all the trick things you would do for very accurate testing. For one thing, the manifolding was not included in the flow testing, and I'm not sure what dimensions were used to simulate the cylinder. I'm not even sure if any radius clay was used at the entrance to the intake port. I'm sure he just figured it was a silly V6, so why be so picky with the flow test.
Anyway, I would expect the flow numbers to be a little off. What's so interesting is how much I had to change the numbers in the sim to get things to match. Far from being a simple error in the flow bench testing. I'll dig the numbers up that I'm using in the sim and post them sometime. You'll be shocked!
The point is, I feel the software is having a problem accurately accounting for the manifolding dimensions that I've picked for this project, and I'm having to make up for a lot of it with the head flow numbers.
My manifolding dimensions are quite simple and the actual layout follows the dimensions in the sim very accurately. Not much room for error there. So what is forcing me to adjust the head flow numbers so much to get it to match real world? Remember, others have been able to come within 5 hp of the sim prediction without having to fudge the input data.

Is the manifolding, or the total combination as a whole affecting some kind of resonance tuning that the software is having a problem mimicking?

Starting to sound like The Twilight Zone, isn't it?

 

[Dusty Bradford]

This brings up another interesting anomaly about the sim that I think is very interesting.

Sure. I would expect that the flow numbers for the heads are not perfect. I gave the heads to a fella that usually ports V8 heads. The ports did come out beautiful. From all that I've read about porting techniques, they were all there in these heads. Still, I stuck with the 1.835/1.5 valves.
His flow testing of the heads, I'm sure, did not include all the trick things you would do for very accurate testing. For one thing, the manifolding was not included in the flow testing, and I'm not sure what dimensions were used to simulate the cylinder. I'm not even sure if any radius clay was used at the entrance to the intake port. I'm sure he just figured it was a silly V6, so why be so picky with the flow test.
Anyway, I would expect the flow numbers to be a little off. What's so interesting is how much I had to change the numbers in the sim to get things to match. Far from being a simple error in the flow bench testing. I'll dig the numbers up that I'm using in the sim and post them sometime. You'll be shocked!
The point is, I feel the software is having a problem accurately accounting for the manifolding dimensions that I've picked for this project, and I'm having to make up for a lot of it with the head flow numbers.
My manifolding dimensions are quite simple and the actual layout follows the dimensions in the sim very accurately. Not much room for error there. So what is forcing me to adjust the head flow numbers so much to get it to match real world? Remember, others have been able to come within 5 hp of the sim prediction without having to fudge the input data.

Is the manifolding, or the total combination as a whole affecting some kind of resonance tuning that the software is having a problem mimicking?

Starting to sound like The Twilight Zone, isn't it?

If your heads flowed 210 on the bench.......what # are you having to put in the sim? 190........240????

 

[Alky V6]

If your heads flowed 210 on the bench.......what # are you having to put in the sim? 190........240????

It's a complete flow curve that is input. This is the intake.

.100 68
.200 142
.350 230
.458 280
.500 272
.550 303
.600 310
.700 312
.750 312

[Ducking for cover]

 

[Dusty Bradford]

Interesting

I'm sure it accounts for alky as the fuel but how does it account for the back pressure the engine sees?

Seeing those #'s makes me wish I would have said what I was thinking earlier. The large turbo which allows you to run much lower back pressure than your average turbo engine SHOULD offset the intake flow as far as hp potential is concerned. It was just a thought that I feel has been proven by other means. Obviously by your #'s it's much more of an offset that I ever would have imagined.

I'm testing something now with my own car sort of related to this. We know a turbo when maxed out will see 2:1 bp ratio. For example a 350ci engine with a head that flows 340cfm will make 35psi with a 94mm. When the turbo is maxed out you will see 35psi and roughly 65-70 psi bp.

Now, I built a 531ci engine with a head that flows 485 and running the same turbo. It may only generate 21psi so the bp should only be 40-45psi. This should allow the engine to make more power with the same turbo. It goes against what every turbo manufacturer suggest's but it's something I want to test.

 

[Alky V6]

Interesting

I'm sure it accounts for alky as the fuel but how does it account for the back pressure the engine sees?

Seeing those #'s makes me wish I would have said what I was thinking earlier. The large turbo which allows you to run much lower back pressure than your average turbo engine SHOULD offset the intake flow as far as hp potential is concerned. It was just a thought that I feel has been proven by other means. Obviously by your #'s it's much more of an offset that I ever would have imagined.

I'm testing something now with my own car sort of related to this. We know a turbo when maxed out will see 2:1 bp ratio. For example a 350ci engine with a head that flows 340cfm will make 35psi with a 94mm. When the turbo is maxed out you will see 35psi and roughly 65-70 psi bp.

Now, I built a 531ci engine with a head that flows 485 and running the same turbo. It may only generate 21psi so the bp should only be 40-45psi. This should allow the engine to make more power with the same turbo. It goes against what every turbo manufacturer suggest's but it's something I want to test.

The sim does allow for the alcohol, and to a point different popular mixture ratios.
What I've done to match real world back pressure was to adjust the nozzle dimension (a/r) until the amount of back pressure in the sim results matched my real world b/p measurements.

Another thing. The adjustment to the head flow numbers was done when I was running the T76 when there was quite a bit more b/p than I'm getting now with the 91mm. So b/p alone does not seem to account for the anomaly.

 

[baadgn]

It's a complete flow curve that is input. This is the intake.

.100 68
.200 142
.350 230
.458 280
.500 272
.550 303
.600 310
.700 312
.750 312

[Ducking for cover][/QUOTE

 

[Alky V6]

This is exactly why I've always been such a stern advocate of the theory that resonance tuning does also occur with turbocharged engines, if you bother to tune to take advantage of it.

 

[cdsttype]

Interesting

I'm sure it accounts for alky as the fuel but how does it account for the back pressure the engine sees?

Seeing those #'s makes me wish I would have said what I was thinking earlier. The large turbo which allows you to run much lower back pressure than your average turbo engine SHOULD offset the intake flow as far as hp potential is concerned. It was just a thought that I feel has been proven by other means. Obviously by your #'s it's much more of an offset that I ever would have imagined.

I'm testing something now with my own car sort of related to this. We know a turbo when maxed out will see 2:1 bp ratio. For example a 350ci engine with a head that flows 340cfm will make 35psi with a 94mm. When the turbo is maxed out you will see 35psi and roughly 65-70 psi bp.

Now, I built a 531ci engine with a head that flows 485 and running the same turbo. It may only generate 21psi so the bp should only be 40-45psi. This should allow the engine to make more power with the same turbo. It goes against what every turbo manufacturer suggest's but it's something I want to test.

What would the compression ratio calculate to in both cases.Where on the
compressor map would we end up in both cases.How much does the squeeze
account for power vs flow?

 

[Alky V6]

It's a complete flow curve that is input. This is the intake.

.100 68
.200 142
.350 230
.458 280
.500 272
.550 303
.600 310
.700 312
.750 312

[Ducking for cover][/QUOTE

Tony. I hope you are grasping the significance of all this.

 

[lazaris]

Interesting

I'm sure it accounts for alky as the fuel but how does it account for the back pressure the engine sees?

Seeing those #'s makes me wish I would have said what I was thinking earlier. The large turbo which allows you to run much lower back pressure than your average turbo engine SHOULD offset the intake flow as far as hp potential is concerned. It was just a thought that I feel has been proven by other means. Obviously by your #'s it's much more of an offset that I ever would have imagined.

I'm testing something now with my own car sort of related to this. We know a turbo when maxed out will see 2:1 bp ratio. For example a 350ci engine with a head that flows 340cfm will make 35psi with a 94mm. When the turbo is maxed out you will see 35psi and roughly 65-70 psi bp.

Now, I built a 531ci engine with a head that flows 485 and running the same turbo. It may only generate 21psi so the bp should only be 40-45psi. This should allow the engine to make more power with the same turbo. It goes against what every turbo manufacturer suggest's but it's something I want to test.

Dusty, I guess it would also depend where the 35 psi and 21 psi fall on the compressor map as well. The 94 may be a lot more efficient at say 30 psi opposed to 21 psi. As well as how many lbs/min the exh wheel of the 94 can flow for the much larger cu in engine. Should be an interesting test.

 

[Dusty Bradford]

Dusty, I guess it would also depend where the 35 psi and 21 psi fall on the compressor map as well. The 94 may be a lot more efficient at say 30 psi opposed to 21 psi. As well as how many lbs/min the exh wheel of the 94 can flow for the much larger cu in engine. Should be an interesting test.

I'm probably wrongly ignoring all the paperwork that the turbo manufacturers use.

To me, the compressor flows x amount of air. Does it matter if it does this at 20psi vs 35psi??? How does the turbo know how much pressure it's making? If the psi on the map is so important, then in reality, you would also need to adjust ci and head flow to maximize the turbo. If the 94mm worked best at 35psi then you would need to adjust head flow and engine size to make sure it doesn't run at 30psi.

I have raced a 352ci Mustang with a 80mm on it. So far the best et is 5.28 at 135. It only makes 17psi but it also only makes 35psi of back pressure. I have taken what I see on this car and applied it to my own. It appears the lower back pressure helps the engine while the intake side is still seeing the same amount of flow, although at a lower pressure. Some will say head flow isn't that important on a turbo engine but I have seen that it is. Everytime the head flow increases, power increases and I feel it's because the intake is flowing just as much air at a lower pressure so the engine is seeing less backpressure.

My small block made 27psi. This big block has made 21psi at 3 seconds out but I have not found a track that can hold it yet Summer is gone along with the 150* track temps so I will be finding out what it can do.

 

[lazaris]

I'm probably wrongly ignoring all the paperwork that the turbo manufacturers use.

To me, the compressor flows x amount of air. Does it matter if it does this at 20psi vs 35psi??? How does the turbo know how much pressure it's making? If the psi on the map is so important, then in reality, you would also need to adjust ci and head flow to maximize the turbo. If the 94mm worked best at 35psi then you would need to adjust head flow and engine size to make sure it doesn't run at 30psi.

I'm not sure but it may matter in regards to wheel speed for a given amount of flow. If the wheel is only turning 20,000 rpm it may only flow x amount of air which only may equate to 10 psi boost. Now speed it up to 80,000rpm and will probably flow more at the higher boost say now 25psi.
It will be interesting what you find. :smile:

 

[Dusty Bradford]

I'm probably wrongly ignoring all the paperwork that the turbo manufacturers use.

To me, the compressor flows x amount of air. Does it matter if it does this at 20psi vs 35psi??? How does the turbo know how much pressure it's making? If the psi on the map is so important, then in reality, you would also need to adjust ci and head flow to maximize the turbo. If the 94mm worked best at 35psi then you would need to adjust head flow and engine size to make sure it doesn't run at 30psi.

I'm not sure but it may matter in regards to wheel speed for a given amount of flow. If the wheel is only turning 20,000 rpm it may only flow x amount of air which only may equate to 10 psi boost. Now speed it up to 80,000rpm and will probably flow more at the higher boost say now 25psi.
It will be interesting what you find. :smile:

What I'm thinking is the turbo operates at a given pressure ratio. It's maxed out at 2:1. I have to wonder if the engine will make more power when your pressures are 20/40 rather than 35/70. The turbo should have to turn the same rpm to generate the hp, but the boost pressures are just lower on the larger flowing engine. When the exhaust valve is open and the piston is pushing against the pressure to get the exhaust out of the cylinder. There has to be hp in the fact the piston is pushing against 40psi rather than 70psi. It may be a wash if the reduction in bp makes power but the compressor side isn't in it's proper range. I built this motor for the 114mm but have to run a class locally with a 94mm so it's a good way to test the theory.

It's been proven lower bp makes power which is why Don's engine will exceed the power normally acheived with that head design.

 

[Dusty Bradford]

On the topic of spooling turbo's with nitrous. A friend had a GN back around 1997 with a TA-49, stretch intercooler, ported heads. He used a 75 shot to spool the car at the street races but also used it for the entire pass. He didn't have to worry about the street racers burning him down because he could sit there barely above idle and spray it when the hands dropped. The car went 10.60's at 27psi. It would make 21psi off the hose, 27psi on it.