Can someone explain why stage II heads are not streetable?

[Alky V6]

Don, i'm just thinking more boost = more air in = more power. If you could do some calculations on your software with some changes with valve size and intake CC',head cfm, comparing your heads to typical S2 heads I'd like to see something to support or disprove my theory of this whole debate, that the bigger heads will net no gains with lower rpm's and smaller cams over production heads. PLease take your boost numbers up to 40 psi with air to air inter cooling with a turbo flow about 115/lbs min and 1.28 ar. 1-7/8" headers, 90MM TB. Thanks Ttypewhite for your input, the thread title should be changed I agree. Also the dyno may not be the best to determine how fast the car will go, I agree but it does give some idea, on the direction I am need to go in.

After I had finished the sim work on my Stage I project, I soon thereafter began working on a Stage II configuration. Bear in mind that I spent months on the Stage I sim work. A little less than that on the Stage II project. The results were very interesting. I still have the files for both builds. Maybe one day I'll go forward with the Stage II build. The interesting thing was how at the low and mid rpm ranges, the power levels very closely mirrored each other. It was in the higher rpm band where the port velocities of the Stage I ports began to offer resistance to flow that the Stage II configuration just kept climbing as the Stage I configuration began to level out. At a certain point, the Stage II ports would also hit that velocity where resistance to flow began to level out the power level. You see, it's the optimum port velocity through the port and matching that port to a particular rpm band using a camshaft to match that is the key.
Long ago, I printed out a hp/tq graph that overlayed the Stage I and Stage II power curves. The Stage II power curve made the Stage I power curve look pitiful. But, the difference was only in the higher rpms. I still have that Stage I/Stage II graph comparison printout magnetted to my tool box at the shop. I'll try to remember to take a pic and post it. Or, just rerun the comparison and make a screen shot.

 

[WIKEDV6]

Ok guys I don't have any experience running stage II headed car on the street yet but I have done my research and talked to people who has done it with awesome results. My motor has been sitting on the engine stand for the past 5 years just waiting to be put in. To me the definition of street ability is; it should be able respond and perform above and beyond what I have in the car currently. It's an old school high 10'sec low 11 sec combo. (Never been to the track with it but she runs pretty good) I am not looking to light the world on fire with my stage II /stage II headed car, I just want to run mid 9's. Well then you guys say why bother running stage II heads/top end parts? Why not production style champions or something similar? Well I am cheap, by the time you price all the goodies with rocker arms and all we are talking over 3K for a production style set up. I have $750 in my stage II heads, rocker arms, valve covers. No brainer there. I paid $450 for a converted intake and $500 bucks for a good set of ATR stage II headers. Champion intake is 750+ and good production style headers are about$ 1000. I also got one of the last Kidney plate from ATR for next to nothing.



Mac's old car in the Chicago area and I was able to see as the new owner brought it to my house for me to check it out. The street was slightly wet so we didn’t go for a ride. Now the owner of Mac’s car also has another stout GN 109 built setup with all the goodies, Big stuff 3, roller cam and so on. I think the car ran low 11's on pump gas. He tells me that Macs old stage II headed street car pulls way harder at 12psi than his GN at 22psi. Had another friend that went for a ride in it said "Holy $hit Batman" that car is freaking fast. Now he started to think about doing a similar setup.



So is stage II heads street able? Well we are all impressed with Mac's old car, Just because it made to run into the 8's or 7's...you can still have fun on the street setup for low 10's or high 9's.



Just my $.02



Prasad

 

[Mac in SD]

Still friends?

No. I hate you.

You crazy mad scientist.

 

[Mac in SD]

Ok guys I don't have any experience running stage II headed car on the street yet but I have done my research and talked to people who has done it with awesome results. My motor has been sitting on the engine stand for the past 5 years just waiting to be put in. To me the definition of street ability is; it should be able respond and perform above and beyond what I have in the car currently. It's an old school high 10'sec low 11 sec combo. (Never been to the track with it but she runs pretty good) I am not looking to light the world on fire with my stage II /stage II headed car, I just want to run mid 9's. Well then you guys say why bother running stage II heads/top end parts? Why not production style champions or something similar? Well I am cheap, by the time you price all the goodies with rocker arms and all we are talking over 3K for a production style set up. I have $750 in my stage II heads, rocker arms, valve covers. No brainer there. I paid $450 for a converted intake and $500 bucks for a good set of ATR stage II headers. Champion intake is 750+ and good production style headers are about$ 1000. I also got one of the last Kidney plate from ATR for next to nothing.



Mac's old car in the Chicago area and I was able to see as the new owner brought it to my house for me to check it out. The street was slightly wet so we didn’t go for a ride. Now the owner of Mac’s car also has another stout GN 109 built setup with all the goodies, Big stuff 3, roller cam and so on. I think the car ran low 11's on pump gas. He tells me that Macs old stage II headed street car pulls way harder at 12psi than his GN at 22psi. Had another friend that went for a ride in it said "Holy $hit Batman" that car is freaking fast. Now he started to think about doing a similar setup.



So is stage II heads street able? Well we are all impressed with Mac's old car, Just because it made to run into the 8's or 7's...you can still have fun on the street setup for low 10's or high 9's.



Just my $.02



Prasad

Thanks, Prasad. I think I want it back.

 

[norbs]

Don please post up the comparison sheet you are talking about. I want to see the potential of the dumbed down heads.

 

[Squid4life]

Don please post up the comparison sheet you are talking about. I want to see the potential of the dumbed down heads.

Sexy new avatar by the way Norbs.

 

[Alky V6]

I'll get that posted up tomorrow. The papers are at the shop and I'm home today with a pinched nerve. It was done in 2006, so yesterday I was trying to update the Stage I powercurve to better match my particular latest real world results. The sim does not want to match what I've been able to do with the combination. The Stage I powercurve is low compared to what I've calculated the car has actually done using more current track timeslips.
The comparison I did in 2006 was with optimized specifications (at the time) for each combination (Stage I, Stage II). Different specs for each combination to squeeze the most out of each. Different turbo and spool rates too. After seeing the graphs again, the Stage II lags behind the Stage I until about 5500 rpm. I know from real world results now, that is wrong. My Stage I just begins to come alive at that rpm. But that could easily be due to the different turbos and turbine nozzle sizes that were chosen at the time. Unfortunately, I don't have a record of all the actual specifications used at the time to come up with those graphs. I do have the files, but they've been modified since 2006.
What I'm going to do is use my most current Stage I file specs, which are still outputting low numbers compared to my real world results, and will simply change the specs that Norbs requested, and we'll see what we get.
Norb, do you have any detailed flow specs of the heads you're going to be using? Detailed cam specs? I have the exhaust specs you posted. Compressor map, or any specs, other than the specs you already supplied, for the turbo you'll be using?
Now's your chance. The more detailed the input, the closer the results will be to real world. Closer, not exact.

 

[Alky V6]

Don, i'm just thinking more boost = more air in = more power. If you could do some calculations on your software with some changes with valve size and intake CC',head cfm, comparing your heads to typical S2 heads I'd like to see something to support or disprove my theory of this whole debate, that the bigger heads will net no gains with lower rpm's and smaller cams over production heads. PLease take your boost numbers up to 40 psi with air to air inter cooling with a turbo flow about 115/lbs min and 1.28 ar. 1-7/8" headers, 90MM TB. Thanks Ttypewhite for your input, the thread title should be changed I agree. Also the dyno may not be the best to determine how fast the car will go, I agree but it does give some idea, on the direction I am need to go in.

Moving this where I can find it easier.

 

[Alky V6]

First EAP comparison. DRW Stage I to Norb Stage II.
I need more detailed specs for the turbo, so I made all of Norbs changes except for the turbo. Both tests are using the FI91X 91mm turbo.
I used 15 inches length for the exhaust primary tubes for Norb's.
The cam for Norb's is 218/218 @ .050", 112 lobe sep, int centerline installed at 108.
My engine, off nitrous, does not spool as quickly as this graph is showing. I used turbine specs that would give an int boost to exh backpressure ratio comparable to my real world results. All the same turbo specs were used for both calculations.
Norb's lines are the dark blue and green.

 

[Alky V6]

For whatever reason, maybe different versions, the EAP on my home computer gives results for my Stage I that are very close to real world. The copy on my laptop is way off.
These last comparisons were done on the home computer EAP version 3.5.

 

[Alky V6]

I'm going to throw an 88mm on Norb's for this next comparison.
This one is interesting. I had to close the turbine nozzle size down to get it to spool. I used 1.8" diameter for the turbine nozzle.
This example is using a GT4718 (88mm) turbo.
Keep in mind, I'm still using the same bore and stroke as my Stage I. 223 cid.
The boost in my graph is 30.5 psi. That's the most the sim will push the 91X for me. The boost in this latest comparison for Norb's is 40.5 psi. In the next test, I'll move Norb's boost down to 30.5 for a better comparison of the two configurations.
This test on Norb's was using an intercooler eff of 85%.
edit: BMEP at 6200 for Norb's was 642 with this 40 psi test. In my book, that's too high. Especially with pump gas. The safe BMEP that I've established for myself is 620. I shouldn't say safe. I should say, the limit not to go above.

 

[Alky V6]

Here it is with 30.5 psi boost.
Intercooler eff. I'm using is still at 85%. That's well into liquid to air territory.
BMEP peaks at 537.
Notice the rpm that the boost in finally kicking in at. 6,000 rpm limit?
Norb. Find an available turbo model that has a published compressor map and specs close to what you plan on using so I can throw it in the sim.

 

[Alky V6]

Here's an interesting comparison. This is my current Stage I graph compared to my Stage II configuration I put together in 2006.
DRW Stage I Alky vs. DRW Stage II Alky.
No nitrous assist was used in either sim calc.
The turbine nozzle diameter spec is on the small side with the Stage II calculation, so the spool up is unrealistic. 2.1" dia was used.

 

[daves87gn]

Here's an interesting comparison. This is my current Stage I graph compared to my Stage II configuration I put together in 2006.
DRW Stage I Alky vs. DRW Stage II Alky.
No nitrous assist was used in either sim calc.
The turbine nozzle diameter spec is on the small side with the Stage II calculation, so the spool up is unrealistic. 1.9" dia was used.
View attachment 153973

Hey Donnie,

in the above graph which is stage I and which is stage II, i think i know just want to confirm my thoughts

 

[Alky V6]

I double checked the last test I posted and the Stage II config was using a turbine nozzle size of 2.1". Still, unrealistic for the size of turbo that was being used in that sim.
Here is another result using a turbine nozzle size of 2.4". Still small for the size turbo, but it's a little more realistic.
Dark blue and green lines are Stage II.
Peak BMEP of the Stage II config in this calc was 618. Boost ramping in and peeking to 42.3 psi by 8750 rpm.
Notice how, for the Stage II config, the larger turbine nozzle size slowed down the spoolup, but freed up some hp on the top end, with the engine still making good hp at even higher rpm. That's the affect of the larger turbine nozzle size lowering the exhaust backpressure, allowing the engine to breathe better at high rpm.
The age old compromise. Exhaust backpressure and top end performance versus spoolup quality.

 

[norbs]

Don, something must be off I should be at full boost at 4500 easy in the real world. I sent you some cam specs, head flow data and compressor maps for you play around with. Be interesting what you come up with. Thanks for taking the time do all this stuff. BTW valve size in the s 2 heads is 2.10/1.625 if you need that info. Also you can input another cam if you want.

 

[Alky V6]

The secret to keeping away from BMEP numbers that get too high to be safe, is to use a turbine side setup that will ramp the boost in, rather than peaking to the max boost setting early on in the rpm range. High boost at low rpm equals big BMEP numbers.
In other words, let's say you want to use 45 psi on a run. You would ramp the boost in through the rpm band and end up with 45 psi by the time you're getting close to redline rpm. So at 5700 rpm, you might only be at 30-35 psi boost. That would help keep cylinder pressures under control through that section of the powerband.

 

[Alky V6]

Don, something must be off I should be at full boost at 4500 easy in the real world. I sent you some cam specs, head flow data and compressor maps for you play around with. Be interesting what you come up with. Thanks for taking the time do all this stuff. BTW valve size in the s 2 heads is 2.10/1.625 if you need that info

Turbo size and turbine nozzle size will have a lot to do with how quickly the turbo spools. That's why I asked for more detail on the turbo you plan to use.
Did you send the info through email? I tend to not check my email regularly.
Nevermind. Found it.

 

[Alky V6]

We might as well throw in the correct bore, stroke and CR. What are they?
What about cam specs? I didn't see any cam specs in the two messages you sent.

 

[norbs]

4" bore 3.59" stroke 6.35 rod 8.5 compression. I sent you the cam specs for 2 cams? did you not get them? 1.7 rocker ratio intake, 1.6 exh on the 234 cam.