Date: Thu, 15 Jul 1999 15:07:55 -0400
From: dg50@daimlerchrysler.com
<< It had been brought to my attention that there is a special reason why the
ST
displacement limit was raised from 2.4 L in its original form to the 3.1L in
its
current form.
There exists a GM 3.1L motor, found in the Sunfire and similar cars, that
unlike
all the other rice rocket motors is a _pushrod_ motor, not an OHC motor.
Accordingly, it needs the extra displacement to be able to run with the small
Japanese/Euro motors, as it's valvetrain limits the amount of RPM you can wind
out of it.
I had forgotten that GM still made pushrod motors. :)
This presents an opportunity. Pushrod motors don't make the same power as OHC
motors of the same displacement, even when supercharged/turbocharged like
they would in STU. This means we can allow some more people to play (and cut
out some problem cars) if we differentiate on valvetrain type.
Something like this:
STU displacement limits are as follows:
- for overhead camshaft engines - 2.500 litres
- for pushrod valvetrain engines - 4.000 litres
- for rotory (wankel) engines - 1.5 litres
//////I know these got revised later///////
This would allow the Grand Prix, Regal etc (they _are_ pushrod motors, right?)
but keep out the more expensive/rare Porches, Supras, etc.
Looks like something Tony George would cook up, eh? :) >>
Yeah, and lok what happened at indy with pushrod motors ;-)
<< BTW, how big is the Olds Quad 4 motor? >>
The latest version is now up to 2.4 litres.
DG
Josh2 wrote:
<< Yeah, and you just threw out alot of the european cars. But a 944
turbo
still fits, 2.5L 4 banger. However, I can almost guarantee that 95% of
the STU cars are going to be OHC. >>
And this is why I felt like writing in again.
If you are going to play with valetrain types, add in 2 valve, 3 valve, 4 or
more valve as the splits. I seem to remember an equivilancy factor given to
these by some sanctioning body a while back, was it IMSA?? that tried to
equalise them.
>From my poor memory it was something like this//
pushrod 2 valve as 1
OHC single cam 2 or 3 valve, something like 1.2
Twin cam 2 valve or single cam 4 valve, 1.3 or 1.4
Twin cam 4 valve, 1.5 or so
Rotaries were 1.8 or 2
Turbo charging was 1.6 or 1.8
A mecanical blower was less like a 1.4 or 1.5
Figure these all in to get an equivilent normally aspirated pushrod
displacement. And then allow about 5.5 litres.
the Talon 2.0 4 valve twin cam and turbo
2.0 x 1.5 x 1.8 = 5.4 litres, actually sounds right.
My 2.4 single cam 2 valve OHC with a turbo
2.4 x 1.2 x 1.8 = 5.2 litres, still seems good
A Grand Prix with pushrod 2 valve 3.8 and a blower
3.8 x 1 x 1.5 = 5.7, Okay will give them the 1.4 = 5.3, Hmmm getting in there.
Just an idea, and it would allow a good break for the non turbo crowd. Just
another idea to throw into the mix. Even Formula one was 1.5 turbo to 3.0 non
turbo for a while.
And now look what happens with a Vortech on a 3.1 Sunfire
3.1 x 1 x 1.4 = 4.34, still way under max,
but turboed it is not okay
3.1 x 1 x 1.8 = 5.58 hmm, we could move the factors a bit
but the 2.8 bimmer which is fine normally aspirated, with a blower or turbo
is out
2.8 x 1.5 x 1.4 = 5.88 blower
2.8 x 1.5 x 1.8 = 7.56 turbo
Adding a weight factor could be alot more fair, but the remarks about scales
being available adds a mess. I am sure a scale could be made vailable, and at
any tour has to be there for the mods and prepareds so why not?
Have displacement and/or wheel size cut offs at 2 or 3 weight points. All one
class though.
over 1800 pounds 4.0 litre limit and 7 inch wheels.
A 1.6 Honda single cam 16 valve with a turbo just fits, go twin cam, and you
are in the next weight class.
1.6 x 1.3 x 1.8 = 3.74 single cam turbo
1.6 x 1.5 x 1.8 = 4.32 twin cam turbo
but with a blower
1.6 x 1.5 x 1.4 = 3.36 so the Jackson kit even on a twin cam is fine.
Over 2400 pounds, allow 5 litres and maybe 8 inch rims.
And maybe one last one, over 3200 pounds, 6 litres and 9 inch rims
Just an idea to throw out there.
I still have to say, emissions should be legal, at least in the state it is
registered in, or beter yet some minimum that could be easilly tested but
easier then the national average. I am sure some arangement could be made for
simple testing at Nationals, anything less you just need a test result. To
equalize and nationalize, some factor could be used. Since I am stuck with
IM-240 testing I am biased a bit, but I had no trouble making my car pass. It
actually passed the first time on the rollers in full race trim, no de-tuning
of any kind.
As a suggestion, we need to find out what testing is done in Topeka. Use
their test but allow double the HC and CO emissions, or something like that
so a change in altitude or fuel does not kill a borderline car. If your car
passes that, you are okay to race, BUT the car MUST be registered for street
use in it's home state. It is a STREET car class. I drive my car, even to
Evansville (350 miles or so one way) And I will drive it to Topeka, over 800
miles each way, if I win DTN. I get 27 + mpg, not bad at all. Even a simple
sniff test at 2500 rpm no load is fine, if we set some easy ppm Hc number
worse then any states test program, but tight enough to make sure it is not
spewing raw fuel through a 300 degree cam.
I like the open nature of STU as it stands. My motor is about as serious as
you are going to get in a street car. It has a cam and ported head with
forged pistons in it. I had to carefully choose the cam to be sure it would
run clean and pass the IM 240 test. If that was not a concern I could
probably make another 100 hp. Same goes for my injectors, I had to size them
a bit small or the idle emissions went up to much, even with the programmable
ECU.
I don't want an "I" class, and the STU as in the rule book is pretty general.
Taking away the stret registration requirement will ruin it. I did try to
start a street mod car class hee a couple years ago, and it failed bad. So I
went back to EMod last year, STU was perfect for me, I just had to de-tune a
tiny bit to fit in after I put the interior back in my car. I see you want to
allow open wheels and tires from SP also. After re-reading the STU It does
look like they allow it, but I think that is a mistake. I read the rules as
keeping the 7 inch / 225 limit of ST. That is a great equalizer for these
serious street cars. It will greatly limit how far one will try to push when
the grip you can get is limited. If they went to street tires too, I would
not mind, I would even drive to events on them as long as all my competitors
were in the same boat. I like the race rubber, and will stay on it if
allowed. But don't allow 10 inch wide tires on 2000 pound cars, it will throw
the whole balance out the window, All of the STU cars I have come across are
running 7 inch or narrower rims, and 225 or narrower tires. Let's keep it
that way please.
Gary M.
|