no2 to spool turbo

[HighPSI]

This is how I look at it. The heads are going to hit the velocity wall before I will get the needed exhaust mass to turn this big turbine wheel to supply big boost numbers. Especially, with the absense of back pressure.
It's going to take a lot of exhaust mass to spin this turbo to that boost level. If the intake side chokes before I can obtain the needed exhaust mass, I'm not going to see big boost numbers. Those are my assumptions since I don't have any real world experience to guide me.
I figure the best I'll be able to do is around 35 psi boost, with an upgraded fuel system.

Velocity wall? You are already capable of driving the turbo to 28psi of boost with only 23 psi of exhaust pressure. Since the intake is so restrictive, why won't the boost go higher than 35? I assume your wastegate is still open through the pass. I say, block off the wastgate and let her eat

 

[Alky V6]

How much fuel are you flowing ? and do you know at what point the velocity of flow becomes a restriction are you able to measure this in real world ?

Isn't that what a flow bench does? Math then allows you to determine the flow velocity through the port at different rpms and densities.

 

[Alky V6]

Velocity wall? You are already capable of driving the turbo to 28psi of boost with only 23 psi of exhaust pressure. Since the intake is so restrictive, why won't the boost go higher than 35? I assume your wastegate is still open through the pass. I say, block off the wastgate and let her eat

The fuel system I described will be maxed out very soon. At 312 kPa MAP/7800 rpm the DC on the e-injectors are 80%. I may push it to 85%, but that will be it until I upgrade the fuel supply system.

It takes exhaust energy to create boost. If the intake chokes, the amount of exhaust mass to turn the turbo also chokes.

 

[Alky V6]

How much fuel are you flowing ? and do you know at what point the velocity of flow becomes a restriction are you able to measure this in real world ?

There are different schools of thought as to what the optimum mach number through the intake port is, but generally it's around .5 mach. Half the speed of sound. After .5 mach, intake flow becomes very restrictive. It's a physics thing.

 

[Quint]

ok yes, uhhhh and what whre you saying again . Damn this is out of my league, but I like it. I may just learn something here

 

[Black Power]

Sure its limiting, the turbo will push thru the flow. At 28# of boost is his heads only flowing 210 cfm ? so what if you took it to 40# what would the heads flow be then? small heads = more boost- big heads = less boost

I gotcha there, but if heads didn't matter, you TSO guys would be running stock 8445 heads :tongue:. So if he ran stage 2 heads he could make the same hp at less boost, but wouldn't you want to make the hp that way? It's a lot easier to flow a lot of water through a garden hose than a straw, after all :biggrin:

Keep in mind, that 210 cfm only has to feed a 37 ci cylinder.

If it's not top secret TSO info, what kinda cfm are the the stage 2s and Champions (not sure which Champions you are using Rs?) flowing?

There are different schools of thought as to what the optimum mach number through the intake port is, but generally it's around .5 mach. Half the speed of sound. After .5 mach, intake flow becomes very restrictive. It's a physics thing.

I'd like to hear more of this also!

 

[Alky V6]

The way I understand it, Stage II heads are flowing around mid 300s and Stage I heads are up to or a little past 300 cfm.
A head that's capable of over 300 cfm will give you the potential for 1600 bhp. As was discussed earlier, it all depends on the total package, but the intake flow capacity has to be there.

 

[antiquettype]

So let me recap what I am reading. You use nitrous to spool an oversize turbo for the small cubic inch. You use a motor with small cubes and small intake ports. I don't know that I agree that you can't get the turbo maxed out with the right tune, but you say you can't so, you can't make big boost pressure because the motor never makes enough energy to get the turbo up to speed. 28lbs with that motor is not a lot of air. I would think that that turbo would make 50lbs+ with that combo. In fact, the disparity in the numbers is suspicious. Is your map sensor calibrated properly? LOL. I think you have made some errors all this time in choice of turbo. It doesn't just have a hard time spooling on the line, but imo 28lbs with your combo it never spools. If you listen to yourself, it is clear. I think innovation is great, and thinking things through is priceless in the understanding, but seeing that the plan is not working out is all part of innovation.

 

[HighPSI]

Once again, we are just dealing with theories until you turn the boost up. Much like you exceding your 700hp goal, I think you are selling your combination short and predict you will make a lot more boost than 35 when you get the car ironed out. Heck, your already flowing enough air now to make (according to you) around 1200hp and turn 7800rpm.

Now, I'll ask the question :smile: Since your original design goal was 700 hp. Why did you chose that turbo? As much research as you do, I would have thought you would of come up with something else. Especially since you now think it is going to limit you from making as much hp as a "cookie cutter" turbo. Cost can't be the issue when you consider how much you have had to put in NOS. It can't be turbo efficency when considering your original goal. It wouldn't be the "bling" factor of having a huge turbo, you have the NOS purge for that :wink:

 

[lazaris]

Just to add something with all this talk about port flow. It made me remember an article written by one of the top engine builders in the country and with many years of testing flow/performance etc. (Reher-Morrison) Its titled,
Flow Bench Fallacies

I'll post a link to the article which is very enlightening but here is a quick quote.

"An engineer will tell you that an engine requires a prescribed amount of air and fuel to produce “X” horsepower. In a perfect world, that may be true - but we race with imperfect engines. The shape and cross-sectional area of the runners are absolutely critical to performance. For example, I have two sets of Pro Stock cylinder heads that produce nearly identical flow numbers, yet one pair produces nearly 150 more horsepower at 9,200 rpm than the other. The flow bench can’t tell the difference between them, but the engine certainly can.
There are software programs that claim to be able to predict an engine’s performance based on airflow numbers. Unfortunately, a critical shortcoming of many of these programs is that they are based on inaccurate information or false assumptions. A computer is an excellent calculator, but it is not an experienced engine builder. The software doesn’t know whether a port’s short-turn radius is shaped properly, whether the flow is turbulent at critical valve lifts, or whether the flame speed is fast enough. Racers have a tendency to believe that computers are infallible, so they accept the software’s solutions as gospel, when in fact they may be badly flawed."

Heres a link to the complete write up.
#16- Flow Bench Fallacies Reher-Morrison Official Blog

 

[Bent6]

I knew that's why I keep sticking it out with the 91.5mm and the spray .......it's the "bling" factor!

I do have to agree with the fact that DW seems to be selling his combo short due to the "on paper" factors of small cubes, small heads, etc. I say get the fuel system in order, crank the boost up and let her eat. We all know boost can overcome wimpy heads to an extent.

Some engine combos like big boost while others can get away with less. So far my new engine combo seems to make pretty good power at lower boost levels but it is a lighter car with a killer set of Stage 2 heads. It's set up for up to 40# but I don't know that I have the balls to run that much even though I know Cal would like to see it.

 

[Alky V6]

So let me recap what I am reading. You use nitrous to spool an oversize turbo for the small cubic inch. You use a motor with small cubes and small intake ports. I don't know that I agree that you can't get the turbo maxed out with the right tune, but you say you can't so, you can't make big boost pressure because the motor never makes enough energy to get the turbo up to speed. 28lbs with that motor is not a lot of air. I would think that that turbo would make 50lbs+ with that combo. In fact, the disparity in the numbers is suspicious. Is your map sensor calibrated properly? LOL. I think you have made some errors all this time in choice of turbo. It doesn't just have a hard time spooling on the line, but imo 28lbs with your combo it never spools. If you listen to yourself, it is clear. I think innovation is great, and thinking things through is priceless in the understanding, but seeing that the plan is not working out is all part of innovation.

Way too early in the game to give up on it. I see the potential, and until I hit the wall with the tuneup, we're never really going to know. I'm just lately getting the launch tune to a point where I can't say I'm sorry for going with the 91mm. The launch is much more controllable with the present setup than it was with the T76. It was easy to over boost at the launch with the T76. Granted, I wasn't using timers like I am now, but you get the idea.
Now that the launch is basically taken care of, with only a pro launch routine to work out, it's time to put the boost to her. I'm only guessing up to this point what's going to happen. I have only the science to go by. I've never pushed a set of small heads on a small motor with a large turbo like this. Not sure anyone has before. We'll see what we see.
I do know that I've heard mention of a comment that Kenney D. said to someone once. M&A heads are done at 1200 bhp. We'll see how true that is.

 

[cdsttype]

Velocity wall? You are already capable of driving the turbo to 28psi of boost with only 23 psi of exhaust pressure. Since the intake is so restrictive, why won't the boost go higher than 35? I assume your wastegate is still open through the pass. I say, block off the wastgate and let her eat

i agree with that and with those small cubes i would raise the rpm by a grand

 

[cdsttype]

I knew that's why I keep sticking it out with the 91.5mm and the spray .......it's the "bling" factor!

I do have to agree with the fact that DW seems to be selling his combo short due to the "on paper" factors of small cubes, small heads, etc. I say get the fuel system in order, crank the boost up and let her eat. We all know boost can overcome wimpy heads to an extent.

Some engine combos like big boost while others can get away with less. So far my new engine combo seems to make pretty good power at lower boost levels but it is a lighter car with a killer set of Stage 2 heads. It's set up for up to 40# but I don't know that I have the balls to run that much even though I know Cal would like to see it.

I ran a small cube engine with less head than don has in tsm the fun did not begin until 35psi!!!Remember boost dose not kill the engine i have guys
in street cars running 27 psi on pump gas and alky.:biggrin:

 

[Alky V6]

Once again, we are just dealing with theories until you turn the boost up. Much like you exceding your 700hp goal, I think you are selling your combination short and predict you will make a lot more boost than 35 when you get the car ironed out. Heck, your already flowing enough air now to make (according to you) around 1200hp and turn 7800rpm.

Now, I'll ask the question :smile: Since your original design goal was 700 hp. Why did you chose that turbo? As much research as you do, I would have thought you would of come up with something else. Especially since you now think it is going to limit you from making as much hp as a "cookie cutter" turbo. Cost can't be the issue when you consider how much you have had to put in NOS. It can't be turbo efficency when considering your original goal. It wouldn't be the "bling" factor of having a huge turbo, you have the NOS purge for that :wink:

You guys keep coming up with questions that I've answered over and over again in other threads. I mean, I don't mind answering them, but I'd have thought you guys were sick and tired of me going over the same stuff over and over again. The 'Novel', as some of you have put it, that I authored covers everything about my project including why I've made the choices I did. Maybe some of you should reread that before I turn this thread into another novel.

To answer your question Cal,
the original hp target for the project was 700 hp. That was mainly due to my lack of experience with the relationship of head flow potentials to hp potentials. This engine was basically my first 'designed from the ground up' engine. Let alone a turbocharged one.
Back in those days when I was putting the engine configuration together, 66mm turbos were considered real big. Bigger turbos were reserved for the Stage II headed monsters.
When I received the flow numbers for the heads, 210 cfm on the intake side, I could not help but be modestly optimistic about the hp potential of the configuration. 210 was only slightly above what a stock head could deliver. I looked around me to see what other people were doing at the time and figured, OK, I should be able to get 700 bhp out of these heads and went with that. That thinking dictated my turbo choice. That was a T70.
I figured that if I broke into the high nines, I would be a happy camper. Although, I was more sure I would end up in the tens, somewhere.
The first time down the quarter with the car was at the 2005 WCNs. I think I had just put on the T76 because of a porcelain accident while learning the alcohol with the T70. I don't remember my train of thought that led me to upgrade to the T76. It may have been due to seeing a few others around me trying out the T76 or the sim was showing me that there was potential with it.
The engine sim that I used to basically come up with the original configuration and that has been tweaked along as the project has progressed has had a lot to do with my choices with the engine.
Anyway, at the 2005 WCNs the car did a low nine pass. I was shocked. It was beyond my wildest dreams. Imagine expecting a low ten pass maybe and then coming out of the gate with a low nine second pass. That's almost an 8 second pass!
Well, after that the sim went through a lot of tweaking. There were obviously a lot of inputs that weren't relating well to real world. Most of the tweaking involved the head flow numbers.
Once those were tweaked to a point where the sim better matched real world, it allowed me to play with different turbos and get a better picture of what turbo would be the most efficient for the engine. I was only slightly concerned with max hp. I realized the heads were going to be the limiting factor. I strictly looked for the most efficient turbo. The 91mm was it. The sim was crazy for it. For this head configuration, this turbo is smack dab in the middle of the eff island at 1200 bhp. 78% efficiency, with the data point rising right up through the middle of the efficiency islands as boost is increased.
Spooling was not a problem that I completely ignored. The sim also showed me that this turbo would be an absolute bear to spool. Yes, I was warned way ahead of time about this problem. Knowing that I would be using nitrous to spool the turbo, I wasn't too concerned.
Another interesting thing about the sim. When I was using the T76, that was when I really started to use the nitrous to spool. The sim told me I would need a 200 shot to spool the T76. I went straight to a 200 shot, and it worked perfectly.
When I was doing the sim work for the 91mm, before I even bought the 91mm, the sim was showing me that I would need a 400 shot to spool it. Of course, I didn't go straight to a 400 shot. I worked up on it, but look at where I'm at with it now. 364 shot port injected with a 50 shot into the turbine housing. Pretty amazing isn't it.
The sim also has shown that this engine combination will be lucky to spool this turbo to 35 psi. That is what I'm basing a lot of my assumptions on. Now with the sim more dialed in due to real world comparisons, it's become pretty accurate at predicting how the setup will work.

As far as the bling factor. Yes, people like to see the nitrous purge, but when they come through the pits and see and hear that there is also a 91mm in the car,... double .

 

[Alky V6]

i agree with that and with those small cubes i would raise the rpm by a grand

RPM costs money. That's why I picked 7800 to be the redline.

 

[Alky V6]

Just to add something with all this talk about port flow. It made me remember an article written by one of the top engine builders in the country and with many years of testing flow/performance etc. (Reher-Morrison) Its titled,
Flow Bench Fallacies

I'll post a link to the article which is very enlightening but here is a quick quote.

"An engineer will tell you that an engine requires a prescribed amount of air and fuel to produce “X” horsepower. In a perfect world, that may be true - but we race with imperfect engines. The shape and cross-sectional area of the runners are absolutely critical to performance. For example, I have two sets of Pro Stock cylinder heads that produce nearly identical flow numbers, yet one pair produces nearly 150 more horsepower at 9,200 rpm than the other. The flow bench can’t tell the difference between them, but the engine certainly can.
There are software programs that claim to be able to predict an engine’s performance based on airflow numbers. Unfortunately, a critical shortcoming of many of these programs is that they are based on inaccurate information or false assumptions. A computer is an excellent calculator, but it is not an experienced engine builder. The software doesn’t know whether a port’s short-turn radius is shaped properly, whether the flow is turbulent at critical valve lifts, or whether the flame speed is fast enough. Racers have a tendency to believe that computers are infallible, so they accept the software’s solutions as gospel, when in fact they may be badly flawed."

Heres a link to the complete write up.
#16- Flow Bench Fallacies Reher-Morrison Official Blog

That's a very good point, and I agree with it completely. As I've already stated, the original quarter mile performance was way off of what the sim was predicting. You wouldn't believe how much I had to tweak the head flow numbers in the sim to match real world.
When I went back to the head porter and told him what the engine was doing with the heads he ported and flowed, his reaction was, , "I want to see those heads again!"

 

[Alky V6]

I knew that's why I keep sticking it out with the 91.5mm and the spray .......it's the "bling" factor!

I do have to agree with the fact that DW seems to be selling his combo short due to the "on paper" factors of small cubes, small heads, etc. I say get the fuel system in order, crank the boost up and let her eat. We all know boost can overcome wimpy heads to an extent.

Some engine combos like big boost while others can get away with less. So far my new engine combo seems to make pretty good power at lower boost levels but it is a lighter car with a killer set of Stage 2 heads. It's set up for up to 40# but I don't know that I have the balls to run that much even though I know Cal would like to see it.

I like to be cautiously optimitic. That way, if the boost does push past 35, I have a reason to go out to dinner and celebrate. :biggrin:
I have pushed to 30 a few passes for just a short spot at the end of a pass, and the engine does eat it up. Mikey does likes it.

 

[Quint]

Mikey needs to let her eat just a tad longer earlier in the run. After reading this post and seeing Cal say it again about letting her eat. it makes we want to re tune Fear to 35-36#'s, ikes!

 

[Alky V6]

Mikey needs to let her eat just a tad longer earlier in the run. After reading this post and seeing Cal say it again about letting her eat. it makes we want to re tune Fear to 35-36#'s, ikes!

LOL! In due time. I feel this latest engine build has stayed together as long as it has because of my very controlled strides forward.
My wife says, if I blow this one up,...?
I don't want to find out what the question mark means.