hoffman900 wrote: ↑Tue Sep 20, 2022 8:56 am
skinny z wrote: ↑Tue Sep 20, 2022 8:21 am
digger wrote: ↑Mon Sep 19, 2022 11:06 pm
When i looked at this in ENGMOD4T this seemed to be reasonable provided you were only looking at WOT maximum average power in the 3-7k rpm range.
I think this is also fundamental to the rule.
Although, peak torque may be more of an emphasis. The average would fall into place. Of course, there are exceptions.
I think the first thing people need to do is to create a histogram rpm plot on how they drive. We use 104-106 LSA (104/104 centerlines, or around 102/106 centerlines) on road race engines. Work great, make a lot of power for something that redlines around 7200rpm, but no way would I call that streetable and I bet most people with these kind of Chevy’s are spending most of their time below 3000-3500rpm (where most dyno pulls start). The 128 rule of thumb also only works for symmetrical valve lift profiles. It’s not going to work with Harold’s lobes, some of Mike’s, and a handful of Comp’s lobe families.
Also, I need to caution about lobe profiles when you simulate. You really need the actual lobe / valve lift profiles you want to test. I have bought cams specifically to have CamDr’ed for simulation work (and sold them). You can kind of rough in one, but it’s not the same and you will be missing a bunch.
In this case, it'll be a tale of two engines.
One would be the typical street/strip/highway deal. As such, the approach to development may be a little different from engine number two. That being a more dedicated racing engine.
From my experiences, and even from the modest simulation work I've managed to do, there doesn't seem to be a lot to choose between what one might get custom ground or something I pull off the shelf with respect to engine number one's performance. The application is too broad I think to be able to determine that any one performance metric is better than another. I.e. drivability vs drag strip results vs fuel economy, etc.
Engine number two on the other hand, would be more defined. RPM range tightened up, and outright power the ultimate goal given the collection of parts already in hand. All that remains is a cam spec really. Then maybe some of the usual experimentation with carb spacers and or carbs, intakes, etc.
This is why I'm intrigued by the TM program because the results provided are quite different from what been spec'd from those aforementioned multipurpose engines.
Anyway, this is all part of the process. The feedback and dialogue are at this time, what's driving the project forward. Scheduling is preventing this from moving along in the hard parts sense until the new year. Maybe a little sooner.
As for simulations, with my limited access to the best programs, I'm typically looking for trends more than anything. All well documented by others but I still look for what happens with a tighter LSA or a split pattern vs a single pattern. Or a small change in CR as examples.