Stan Weiss wrote: ↑Thu May 24, 2018 2:01 pm
One more try just as an experiment. If anyone just wants to look at the cam lift and duration numbers then you are not seeing the whole picture. While these number are not quite as close as the last set look at how much different the cam number are. This was done with real measured lobes data. Way more rocker arm ratio so I do not know how that would workout.
What Compression Ratio are you plan on using with this either actual or theoretical Engine ?
Larry,
Thanks. Yes it is a theoretical Engine. In my first I said pump gas and CR = ???. That said I look at 900 HP @ 7500 as more of a pump gas race engine than a real street engine. So while I was thinking in the 10.5:1 to 11:1 range I was also looking for input from others.
Stan,
I made up a few different models (Spreadsheets, EnginePro and Controlled induction). They hint that 7000 may be a more realistic RPM for 900hp. Solid rollers and race gas CR range help to get there too. Durations run from 276 to 290@.050" and ICL's 106 to 109. Other than running out of air they did not agree on much.
Stan
i ran your valve lift data through Prof Blair's 4StHead, program 23, and adjusted both lift and duration to get very close matching STA values compared with the targets.
The three screenshots follow.
You'll note that in order to match the targets, the required valve lifts are pretty formidable, especially the exhaust.
And this is only a computer exercise. !
You do not have the required permissions to view the files attached to this post.
pcnsd wrote: ↑Fri May 25, 2018 10:11 am
Stan,
I made up a few different models (Spreadsheets, EnginePro and Controlled induction). They hint that 7000 may be a more realistic RPM for 900hp. Solid rollers and race gas CR range help to get there too. Durations run from 276 to 290@.050" and ICL's 106 to 109. Other than running out of air they did not agree on much.
Vincenzo wrote: ↑Sun May 27, 2018 6:31 pm
Stan
i ran your valve lift data through Prof Blair's 4StHead, program 23, and adjusted both lift and duration to get very close matching STA values compared with the targets.
The three screenshots follow.
You'll note that in order to match the targets, the required valve lifts are pretty formidable, especially the exhaust.
And this is only a computer exercise. !
Ron,
Is it possible to get your cam files in S96 format?
Stan,
This is what I have. They are close on I durations and ICL and off on E durations and ECL, but overall better than before. The two performance models are saying 7050-7100rpm for Peak HP and 5640 for PT. I used that in the models that ask for a number. CI wants a bigger valve. Engine Designer warns of pinch point velocity and I couldn't find dimension numbers so I turned the function off in the model.
Engine Designer:
EDPontiac535Test1.png
EnginePro:
EPPontiac535Test1.png
My spreadsheet (OptCam from the HP Chain):
ECPontiac535test.png
Controlled Induction:
ECIPontiac535Test1.png
You do not have the required permissions to view the files attached to this post.
Just for the heck of it I ran Jon Kasse 851 hp 507 EMC Pontiac engine through DV's 25 year old Cam Master and it puts it around a 301 seat and a 106.5 LSA and the head seems good for that ci but for the 535 it goes to a 104 LSA unless you change it to a 2.4 valve and then it calls for a 107 LSA.
Pertaining to the cam choice, Kaase says, “With a couple of years’ data from other engines, we had somewhat of a baseline. We had two cams made for this engine–one with 257/261 degrees duration at 0.050 and the other with 261/268 degrees duration at 0.050. Though it didn’t produce much more power than the other, I decided to go with the larger cam. The 107-degree lobe-separation angle was based on previous tests, and we tried different rocker ratios, but the 1.8:1 ratio, which happens to be the highest ratio allowed in the competition, made the most power.”
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
the S96 files have been completed, but I'm unable to find a way to upload them to this forum, so will have to get them to you by some other means.
Both exhaust and intake files very closely match the Blair STA targets for the Pontiac 535 engine, details as per your opening post, but with the exhaust valve size correction included.
The designs match the STA targets, but that is all one can say. The targets themselves are at best general guides, for some engines they may be very good guides, and for others far off the mark. For this Pontiac engine I fear the latter is clearly the case.
pcnsd wrote: ↑Mon May 28, 2018 2:22 pm
Stan,
This is what I have. They are close on I durations and ICL and off on E durations and ECL, but overall better than before. The two performance models are saying 7050-7100rpm for Peak HP and 5640 for PT. I used that in the models that ask for a number. CI wants a bigger valve. Engine Designer warns of pinch point velocity and I couldn't find dimension numbers so I turned the function off in the model.
Paul,
I have a different version of Rick's software and used a few different inputs. I had it create S96 files and got these TA's.
Vincenzo wrote: ↑Sun May 27, 2018 6:31 pm
Stan
i ran your valve lift data through Prof Blair's 4StHead, program 23, and adjusted both lift and duration to get very close matching STA values compared with the targets.
The three screenshots follow.
You'll note that in order to match the targets, the required valve lifts are pretty formidable, especially the exhaust.
And this is only a computer exercise. !
Ron,
I got the S96 files. I am not sure what I am doing wrong but I do not get the same TA's
OK, I do not use the Time Area calculations in my software very often. What I found was a number of years ago when I changed one section from using curtain area calculated by valve diameter and lift to also using curtain area calculated by including valve size angle and valve seat width that I did not do that for this section. This is both the new and old time areas that i now get using Ron's S96 files.
Stan Weiss wrote: ↑Thu May 24, 2018 2:01 pm
One more try just as an experiment. If anyone just wants to look at the cam lift and duration numbers then you are not seeing the whole picture. While these number are not quite as close as the last set look at how much different the cam number are. This was done with real measured lobes data. Way more rocker arm ratio so I do not know how that would workout.
What Compression Ratio are you plan on using with this either actual or theoretical Engine ?
Larry,
Thanks. Yes it is a theoretical Engine. In my first I said pump gas and CR = ???. That said I look at 900 HP @ 7500 as more of a pump gas race engine than a real street engine. So while I was thinking in the 10.5:1 to 11:1 range I was also looking for input from others.
the S96 files are for those used in this computation in 4StHead. Note that the S96 files have an addition of E and I in the identification purely to relate to their location, exhaust or intake.
Note also, the valve lift designs feature opening and closing ramps, with tappet clearances included.
The 4StHead input and output pages show all details.
Despite the near matching STA's, when all the relevant data is run through EngMod4T and Blair's software, both computed outputs fall way short of the target 900 bhp at the stipulated 7500 rpm.
You do not have the required permissions to view the files attached to this post.
Vincenzo wrote: ↑Fri Jun 01, 2018 6:11 pm
Despite the near matching STA's, when all the relevant data is run through EngMod4T and Blair's software, both computed outputs fall way short of the target 900 bhp at the stipulated 7500 rpm.
This is the issue I have with the current "prescribed" STA values, I do not believe the targets for a 2 valve engine should be the same as for a 4 valve engine. And the various 2 valve layouts should each have separate set of target values. As I said before, there are tuners that developed their own values and use it very successfully but do not share. DV probably has the largest database of all by a large percentage but understandably he will not share as he makes his income from it.
“Ignorance more frequently begets confidence than does knowledge.” -Charles Darwin, The Descent of Man
