Sterling Doc wrote:


Thanks for the data! You don't have any of the tq plots do you? I'd be interested in slightly lower than 4k, too. With the wide gearing in our transaxles, 3.5k is important. There are a lot of corners where you "bog" down low in third, because you'd run out of revs too quickly if you use 2nd.

I will try to get some of my own dyno information together over the off season. I think I could get 3-4 of the Texas cars on the dyno for some investigation.

I'm willing to bet that I can find a few secrets in these motors. I don't like secrets in a spec series, so I will of course share anything I find. As much as I'd like to build every spec motor in the country, I don't want this to become like some other spec series where you have to buy a $20k motor from a shop that knows the recipe for the secret sauce to run out front.

-bj

-bj

loftygoals wrote:


BJ, I entered all the data using the original plots, and a ruler, as each dyno was on a different scale. The look much more different when put on the same plot! It would take me a while to go back, and do the TQ, or 3,500 RPM plots. I'll see if I can get to it, but it will be a while.

I very much agree that keeping this info public is best for the series, and appreciate the help that you and others have given to make it so. We are looking into many options to balance the motors cost effectively, but we need to do some testing first. We are in the process of gathering the motors, and parts to do this right. We need GOOD data, more than we need it fast...

Have you double checked the port volumes? I've never heard the ports themselves were different between the early and late heads, just the combustion chamber shapes. This would be good information to have verified.

Post up your info when you get it.

Thanks!

Sterling Doc wrote:


Just for the record, your engine has 9.5:1 pistons and max shave (0.892"?). My engine has 10.2:1 pistons and the head was shaved to 0.935", so it's not really an apples-to-apples comparison.

I'm not sure we can isolate the ports in the 6R head as the cause for your power drop-off at high rpm. There are other variables which we don't know, such as:

- Do we know your fuel and ignition systems were working perfectly? I seem to recall you were running below 12.0:1 A/F.
- Do we understand the effects of reshaping the combustion chamber by shaving the head to min for 9.5:1 pistons? This effectively removes the shallow "shelf" above the spark plug.
- Perhaps something else is wrong mechanically? I have found intake manifold gaskets installed incorrectly, effectively blocking off a portion of the intake runner.

So basically we need to take a step back and look at this as a system first.

BJ- may I ask how were the volumes of the ports measured? If this was done with the valves installed, different valve types and seat heights will affect this measurement.

loftygoals wrote:


Because no idle control valve screws up the idle. The ISV and Aux Air Vavle are designed to make the car idle properly when cold or hot. When they are missing or don't work you get funky idle. Bad things can result. Nothing terminal, but it is a pain. IMHO the cars work better when the idle properly in all conditions.

Don't forget also there is a slight revision to the late cam vs the early cam. I believe the exhaust duration changed slightly. Not to metion a cam can wear down and cause issues of its own.

Also there could be other factors such as oil weight, or gearbox oil weight that could be a small influence. The thing to consider is that when looking for 2-4 hp type numbers on a chassis dyno there are lots of noise factors. Carefull planning can try to deal with these, but at somepoint you have to just say the dyno method can't resolve below a certain HP spread. I tend to think that at 2 hp forget it. Trying to determine a 2 hp difference between two cars is frought with challanges. Once you get 4 or 5 you are starting to see something.


We also need to put in perspective that 2-4 hp range is pretty good considering we are using old motors with various number of hours on them and initial produced over a 5 year period. At somepoint you just have to say enough.

To me we do need to understand the impact of 10.2:1 pistons vs 9.5:1 and have some understanding on how shaving can close the gap. Even so we can never ensure two cars on grid will have idential peak power or power curves. If we were dealing with all new motors and had the money to spend to ensure all motors were perfectly identical then maybe. However given that fact that mostof our best part sources are junk yards we have realize we can never be 100% equal. We just need to do the best we can.

Dave, I certainly agree that my result seems like an outlier, and are in no way conclusive, only interesting.

We don't have AFR's on the compliance dyno, but the particular dyno I referenced on my car was done on earlier the same day, and does have AFR's, though I'm not sure they are ones I trust - the probe fell out of the exhaust halfway through the second run, and was pretty variable when it was "in" . My recorded AFR's varied between 13 and 14 until about 5,200, and then went up to between 14 & 15 from there. Based on that data, I moved my AFM one click richer, but did not have time to retest. Strangely, when I went for my compliance dyno later that day after the race, that change cost me nearly 5 HP, and 8 ft. lbs or torque (DOH!) I need to go back, and look at what my Traqmate recorded my AFR's at, as I'm not sure the dyno AFR's were correct. The configuration of my exhaust may have caused issues with the AFR readings.

I have another shaved 6R head on that motor now (though slightly less shaved than the other one). It wold be interesting to retest this, and swap AFM's, etc.