Kevin Fennell

So NASA just surprised all of us with forced induction with a new rule. Basically if you have FI you only use your 4 highest horsepower points (measured at 250 RPM intervals). For me this means my horsepower at 7750, 8000. 8250 and 8500 RPM vs the old way of measuring at 7000, 7500. 8000, 8500. This new rule gives me an extra 10+ HP that I have to ballast out which would mean 142!!! lbs of weight in a currently 2230 lb car. It seems excessively silly since I can't run a super close ratio sequential or anything to take advantage of this imaginary small power band without being penalized already.

So I would like to avoid this with tuning my throttle to close a little after 7750 RPM and maintain a steady HP over the last 750 RPM 15 AVG HP lower then it is now. Since the 7750 data point doesn't need to change, what really happens is the 8000 goes down 9 HP the 8250 goes down 15 and the 8500 goes down 21. For roughly a 15 HP average drop or 7%. of the average HP that I am actually making during a lap (around 225 but this could be off by a few).

On the two tracks I have good data I can see that I am accelerating and above 8000 RPM for 5.3 seconds at MSRH and 4.7 seconds at COTA or 8% and 5% of the time that I am accelerating during a lap.

This gives less then half a percent reduction in total power output over a lap right? This has to be less effect then a 100 lb weight increase (or 4.5%). Right? Or did I get way out of line somewhere here. I know that HP will not equate directly to weight when expressed as a percentage, but it has to be less then 9 times more important right!?

Kevin Fennell

Also I hope someone builds a 7000 RPM max K24 that makes 290 HP over 1900 RPM and 4 HP 100 HP below that because the throttle closes in the tune. and mates it with a close ratio transmission and gets around this to show how pointless it is to target only FI builds.

wanna911

Has nothing to do with forced induction. Everyone had to do it. This is actually better as it evens the playing field.

Kevin Fennell

Nope check the new rules as of the 10th. They revised them again and FI needs to use 4 data points at any RPM, whereas the first draft had me using 8 and actually gaining a small HP advantage because they only cared about how many RPM you use.

wanna911

Ah, ok. Didn't realize the new rules were out. . The thing about it is that you can easily build torque monster turbo (or high Displacement low revving NA) cars so thIs might help out higher revving lower torque motors in the Hp department for top end speed and less shifts per lap. Maybe they should just add in a calc for torque as well. That being said, every rule is for helping Corvettes so don't be surprised.

Kevin Fennell

The thing is I HAVE a low torque high rpm motor. I make something like 156 ft lbs across the board. But because i do this by making 8 lbs of boost with a supercharger I'm penalized.

wanna911

Wow, really? What kind of car? Not stock I assume. Unfortunately for you, your build is the worst possible for this method of parity and classing. I haven't run numbers yet based on the smaller sampling but it's gonna hurt in sure. Fortunately for me I'm near the top end, so at 3300 I get a hefty weight concession. With so many new cars going to turbos though, more and more will be in that category. However in my opinion, NA is still best and quickest for anything short of unlimited. It doesn't need any handicaps.

edit: Just ran the numbers and the new rule would cost me 8 Hp vs dividing by 6 (only rev to 6800 rpm) But that's only 50 lbs for a TT1/ST1 car. How are you coming up with 142 lbs ballast? Even at 8 data points difference is 14 Hp and that's still "only" 85 lbs.

911racer

I am having a hard time seeing this change. Here are the rules. Changes in red

https://nasa-assets.s3.amazonaws.com...ries_Rules.pdf

Oh, My bad, I thought this was GTS, not TT or ST.

Thanks
Ed

Kevin Fennell

it is a slightly not stock TT3 exige. Running like 2 extra lbs of boost and full bolt ons.

in TT3 its 9.4 lbs per hp for me plus the change in tire points for 245 size tire.

docwyte

Yeah, well I used to run in TTC. NASA basically deleted my class, as the new TT5 rules pander to the TTD cars. Not only would I have to demod my car, I'd also have to add weight AND detune it to fit into TT5. So instead I get to be massively underpowered and uncompetitive in TT4. Or spend thousands and thousands of dollars trying to make more power by either adding forced induction or doing a motor swap.

So I'd say you got off easy....

AudiOn19s

I was ready to jump into TT3 a couple yeas ago when it was still 9:1. The rule changes making 3 go to 10:1 thwarted those plans for me. Thought the average power thing was going to help me out but my power curve is soo flat near the top it didn't really help at all. I'd have to modify the heck out of my car to be competitive in TT2. Is what it is.

wanna911

Sorry Andy, but have to call you on this one. Based on your lap times, you would have won every TT3 event at Mid Ohio since 2015. And you would have won every TT2 event except one, where you would have placed 3rd (while in TT3 trim).

There may be a reason you aren't doing TT. But competitiveness isn't one of them.

And isn't your car still street legal?

docwyte

You left alot of free Hoosiers on the table there Andy!

AudiOn19s

[excuses]

Fair...too much focusing on bench racing track records vs. actual results I guess. The TT2 record from 2013 is 1.2 seconds faster than I've ever gone

It's never quite been TT3 legal, under the current rule set it's a 8.75:1 car... In '15 it was a little heavier and closer to 9:1 but would have still needed 60 lbs or so. I'd have to add almost 350+lbs to make current TT3 rules. That said, in looking at actual results I'd agree...I could have, in theory, done well in TT2 in 2017...and there were decent car counts for the first time in the last few years.

[/excuses]


Correct, fully street legal with full interior still.

z06801

Hey I need all the help they'll give me Dez! How will I look under the rules? Weight at 3250 and 508 hp and running slicks going to try to make it to nationals at COTA.