Can someone explain why stage II heads are not streetable?

[Alky V6]

Donnie, your basing your head flow numbers in the calcs against real world hp numbers. This also means with stage 2 heads and putting flow numbers in, could also be way off from real world results.

That is correct. That is exactly what I was trying to explain in a recent earlier post. Something to realize, though. Many other people, including big name engine builders and tuners, have used this engine sim software with predictions that would later turn out to be within 5 hp of real world results. Verified on an engine dyno. Kenny and Mike at TA Performance use this software. Mike told me once about the story where this software came within 5 hp on an 'engine dyno challenge' engine he put together using the software to come up with the specs. He won that engine challenge.
The point being, what is it about my Stage I combination that required me to make such a drastic change to the head flow numbers to make the sim match real world numbers? What was the sim unable to take into account?

It is impossible for a M@A head to flow near 340 cfm with your valve sizes. You are having good results with your heads I do agree.

I completely agree. On a typical test flow bench, you are correct. Now, let's consider the help you can get with pressure pulse tuning. As far as I know, that cannot be simulated on any current cylinder head port test flow benches. And, it seems cannot be properly simulated by the engine analyzer software, either.

 

[Alky V6]

The original peak flow number for the intake port that was given to me by the person who ported and flowed the heads was 210 cfm.
How many people have done 8s with 30 psi boost on an intake that test flowed at only 210 cfm?
I would have thought it to be impossible, right up to the exact point where I actually did it.

 

[norbs]

The original peak flow number for the intake port that was given to me by the person who ported and flowed the heads was 210 cfm.
How many people have done 8s with 30 psi boost on an intake that test flowed at only 210 cfm?
I would have thought it to be impossible, right up to the exact point where I actually did it.

No one that I know, expect you. Doing some calcs I am coming up with a wall of 1150 hp @30 psi @7000 rpm, and970 ftlbs@4500 rpm, which is exactly the rating of the tubo, isn't that odd. I think that is enough for me!


IMEP@570 psi

Thanks for your insight

Norb

 

[norbs]

Pulling 30% flow out of the heads 220cfm , looks like the stage heads are worth 120HP over production style heads@6000 rpm and 200HP at 7200 rpm, at 5000 RPM about 50 HP difference. Does this make sense to you?

 

[Alky V6]

Pulling 30% flow out of the heads 220cfm , looks like the stage heads are worth 120HP over production style heads@6000 rpm and 200HP at 7200 rpm, at 5000 RPM about 50 HP difference. Does this make sense to you?

Yes, it makes sense.
What is the BMEP where you're seeing the IMEP of 570?
Take note that for the sims of your combination I was using blower rich gasoline and 100 octane. Also, take note of the knock index readout. Anything between 1 and 2 for the knock index is a maybe for knock. Anything above 2 is considered likely.

 

[Alky V6]

Norbs. What the knock index is telling you is that the power curve is not realistic for real world use with the parameters you're using. You need to play with the typical parameters that would be used to lower knock to get that knock index down. When you finally get that knock index down below 2.0, you'll have a power curve that is more realistic for real world use. Anyone can come up with a power curve that looks very impressive on a sim, but will it translate into something that can work and be durable once it's built?
You'll notice that as you play with the parameters to get the knock index down, the power curve is going to change a lot.

 

[norbs]

I got the knock index in the 3's which is not good. I'll have to check some stuff over for sure. I did some more fooling around, I put a 210/210 hyd roller cam in the sim and it seems the cam size does not make that much differernce, maybe 50hp at 7000 rpm?

 

[Alky V6]

I got the knock index in the 3's which is not good. I'll have to check some stuff over for sure. I did some more fooling around, I put a 210/210 hyd roller cam in the sim and it seems the cam size does not make that much differernce, maybe 50hp at 7000 rpm?

You would find that it might make more difference if you found the right manifolding specs for each camshaft. The heads, cam and manifolding should be treated as a system. If you make a change to one, you need to make changes to the others to optimize the 'system' to the new change.
Just for kicks, start lengthening the primary tube length 2 inches at a time and see how it affects the power curve. You have a lot of options with the exhaust system. You will be surprised how much of a difference the exhaust manifolding makes.

 

[Alky V6]

7,000 rpm for a Stage II head, I would consider to be mid-range for those heads. It makes perfect sense that you would be able to get away with less duration with the flow capacity of those heads. But, if the plan is to turn it to 7,000 rpm. The right valvetrain has to be in place.
I really feel you would be cutting those heads short by limiting your rpm to 6,000 rpm.

 

[Alky V6]

You'll find that the exhaust tuning is more effective with the larger durations.

 

[Alky V6]

When you start getting used to tuning in the exhaust system, the next component to include in the 'system' is the turbo. Backpressure is fun to play with. That can make some amazing differences.
Keep in mind, the little advances that I got out of the sim by tweeking this and that, translated into big differences real world.

 

[norbs]

Don, Im limited to header design, I have no plans to remove the AC from the car. But even though the calculations can be off it seems that the turbo and heads create the most power, and those people who want to dumb down the heads with a smaller cam can still make good power, sure the bigger cam will help to get maybe 50-100 hp more, but not needed if you want to runs 9s and have the car"streetable" How fast was/is Mac'sd car in street mode?

 

[Dusty Bradford]

7,000 rpm for a Stage II head, I would consider to be mid-range for those heads. It makes perfect sense that you would be able to get away with less duration with the flow capacity of those heads. But, if the plan is to turn it to 7,000 rpm. The right valvetrain has to be in place.
I really feel you would be cutting those heads short by limiting your rpm to 6,000 rpm.

I agree. 7,000 rpm is as low as I'd want to turn a Stage 2 head. If 6,000 rpm is the limit something like an out of the box GN1 is more than enough.

The Stage 2 heads are just as streetable as any head if streetable means it can be driven on the street. The issue is the large port hurts low end torque because it's more ideal for higher rpm ranges. I have seen as much as 400 rpm difference in stall speeds with Stage 2 cars, especially if the cam is too big. They are down right lazy down low under 3200 rpm. If I wasn't going to turn the engine at least 7,000 I would go with a conventional head.

As for the cam. A 274ci engine with Stage heads and a cam in the 232-236 range will make power to 7500 so the cam for a 6,000 rpm stage head could be back in the 218-220 range. IMO this low of an rpm target for a stage 2 head is a poor combo.

 

[Alky V6]

Don, Im limited to header design, I have no plans to remove the AC from the car. But even though the calculations can be off it seems that the turbo and heads create the most power, and those people who want to dumb down the heads with a smaller cam can still make good power, sure the bigger cam will help to get maybe 50-100 hp more, but not needed if you want to runs 9s and have the car"streetable" How fast was/is Mac'sd car in street mode?

You'll have to ask Mac. I don't know that he ever did get the car dyno'd or tested on the track after putting on the Stage II heads.
I would expect that you should be able to do 9s with a small cam. If I couldn't at least do 9s with the Stage II heads, I for one would be embarrased to have the heads on the car.

 

[daves87gn]

This is a great-running car. Don't believe that S2 heads are dogs on the street: this thing will roast the tires at any speed you floor it. Only had it to the track once in current configuration: on pump gas with 12 pounds of boost and worn out M&H Racemasters, it went 11.20 at 122. Again-that's 12 pounds - not even in the envelope for a T-76.

here is what Mac posted when the car was for sale, big heads, small cam, low boost dont know anyone that wouldnt be happy with 11.20 @ 122 with 12PSI, wonder what it would do at 25-28PSI

 

[norbs]

I agree. 7,000 rpm is as low as I'd want to turn a Stage 2 head. If 6,000 rpm is the limit something like an out of the box GN1 is more than enough.

The Stage 2 heads are just as streetable as any head if streetable means it can be driven on the street. The issue is the large port hurts low end torque because it's more ideal for higher rpm ranges. I have seen as much as 400 rpm difference in stall speeds with Stage 2 cars, especially if the cam is too big. They are down right lazy down low under 3200 rpm. If I wasn't going to turn the engine at least 7,000 I would go with a conventional head.

As for the cam. A 274ci engine with Stage heads and a cam in the 232-236 range will make power to 7500 so the cam for a 6,000 rpm stage head could be back in the 218-220 range. IMO this low of an rpm target for a stage 2 head is a poor combo.

I understand what your saying dusty but the stage II stuff is actually 1/2 the cost of the champion head stuff, and will require less boost to make equivalent HP, even at 6k rpm, according to the calcs.

 

[Mike E]

Which is more important to you max power or streetability. You asked about streetability, but the last two pages have been about power curves. That's two completely different things.

These calculations you guys are throwing around are for wide open throttle. If your worried about max power at WOT, the stage heads will win. But when was the last time you used WOT with a 1000 hp motor on the street.

It's a whole different ball game at 10% or 20% throttle. No sim program or calculator is going to tell you that. Dyno numbers are a very small part of the equation.

 

[norbs]

Which is more important to you max power or streetability. You asked about streetability, but the last two pages have been about power curves. That's two completely different things.

These calculations you guys are throwing around are for wide open throttle. If your worried about max power at WOT, the stage heads will win. But when was the last time you used WOT with a 1000 hp motor on the street.

It's a whole different ball game at 10% or 20% throttle. No sim program or calculator is going to tell you that. Dyno numbers are a very small part of the equation.

Sorry Mike we are getting off track, I agree. I guess I will have to drive it around and see how I like it on the street. My friend has a S2 headed car for street use and the throttle response is quite well.

 

[Camarosnake]

Sorry Mike we are getting off track, I agree. I guess I will have to drive it around and see how I like it on the street. My friend has a S2 headed car for street use and the throttle response is quite well.

I am the person in question, I have a stage 2 276 cu in.. the heads have 2.19 intake valves and 1.75 exhaust... The heads are chapmans... flow numbers are 340 intake and 260 exhaust... rockers 1.64 intake and 1.57 on exhaust. This car at 19 lbs did 9.64 @ 141... did 6.19 in 1/8th @ 119... 4oo turbo tranny and engine is in a 1968 camaro... Not sure what to expect this car to run around 30 lbs. By the way, this car is street driven daily... on the 9.64 pass it was driven to the track 2 hours one way and back again 2 hours....

 

[Camarosnake]

I am the person in question, I have a stage 2 276 cu in.. the heads have 2.19 intake valves and 1.75 exhaust... The heads are chapmans... flow numbers are 340 intake and 260 exhaust... rockers 1.64 intake and 1.57 on exhaust. This car at 19 lbs did 9.64 @ 141... did 6.19 in 1/8th @ 119... 4oo turbo tranny and engine is in a 1968 camaro... Not sure what to expect this car to run around 30 lbs. By the way, this car is street driven daily... on the 9.64 pass it was driven to the track 2 hours one way and back again 2 hours....

Was

Was done with a 88 mm precision turbo, solid cam with isky lifters, 250 seat pressure and 550 over the nose pressure.