GSMnow@aol.com wrote:
> As far as I can see, under the current rules most turbo cars are a bit
> overclassed, but that is not the issue here. Anyone who knows how an engine
> works can see a 2.0L turbo motor will not make as huch power as a 5.7L
> engine. But the SPAG seems to think other factors equalize this.
When you say "overclassed" you mean "they're the class lightweights" right?
Aside from the ESP Supra (which is in the wrong class) and the ASP RX-7, all the
other SP turbo cars are classed very conservativly.
I agree though that in many cases, there are other factors that tend to make up
the power differences. In the DSM case, there's AWD and an independent rear and
less weight. You don't need equal raw power numbers to have fair classing - a
DSM with a F-Body torque curve would be a BSP car - but more like equal
power/weight numbers.
Fair classing is NOT simple by any means.
It needs to be emphasized, I guess, that the DSM folks are NOT looking to make
F-body torque or power numbers. (Not that they could anyway)
> If you backdate to the old turbo which has better flow, do you then also have
> to run the older cars LOWER boost pressure?
Yup. The wastegate and actuator is part of the turbo. We backdated folks do
indeed run lower boost pressures than with the T-25.
Now in high gears, with high loads, you will get boost creep to higher boost
levels when the wastegate can't keep up any more, but that's not an issue at
Solo2 speeds/distances. If you've got a course that allows a DSM to see the top
of 3rd and start creeping, you've got bigger problems than a DSM making more
power than normal. Like cars moving at 90+ MPH.
> The small newer turbo makes
> more power in stock trim because they run it at more boost, the bigger old
> turbo runs a lower boost level and has a flatter power curve but more lag.
That's exactly it - and the trade-off implied (assuming the swap is allowed) do
I make more peak power, or more average power?
There have been courses this year when I would have been better off with the
T25, but there also have been courses where the 14b was better.
> If they are allowed to do this swap, then the Porches should be able to put
> the new twin turbo setup on the older cars, right?
If they are are on the same line, and the update/backdate is a bolt-on deal, I
don't see why not. According to my proposed wording, the entire twin setup has
to go as a unit (both turbos plus anything linking them together)
> Now to say why this is a problem, the whole motor and boost control system
> works together. The boost on these cars is controlled by an ECU controlled
> valve.
Then the ECU control must go with the update/backdate. It's not an issue on the
Talon, because the ECU doesn't directly control boost... well, it _can_ but it's
an emergency thing. The Talon ECU has "run full boost all the time, I'll kill it
if there's a problem" logic, not "I control the boost level as a function of
foo" logic.
> When I ran my 87 GrandAm Turbo a few years back, I could not use any
> chips or aftermarket EFI because the WHOLE ECU was controlling the boost.
That's not entirely true. You could have a chip made that played with spark or
fuel, but left the boost stuff alone. Just because all the readily available
aftermarket chips played with boost doesn't stop you from having a legal one
made.
> I can envision many other cars where turbo up/back dates can influence the
power
> curve and/or max power.
Well, that's kinda the point, isn't it? I mean, an air cleaner can "influence
the power curve and/or max power".
That an updated/backdated turbo makes more power (or not) isn't a sin or a
problem, as long as the end result is appropriate for the class. It turns out
that most turbo cars (DSMs included) are SO conservatively classed in the first
place that there's room for a fairly large (potential) power increase without
affecting class balance - aside from making more cars competitive, and that's
good, right?
And lag issues, etc. help cushion the blow somewhat. A (pulling a number out of
the air) 50HP increase on a turbo motor is not the same as a 50HP increase on a
N/A motor, because on the turbo car, that 50HP is not immediately available. A
N/A motor that makes 300 HP at 5000RPM always makes 300HP at 5000RPM, whereas a
turbo car that makes 300HP at 5000RPM under boost may make 100HP at 5000RPM
completely off boost.
> I feel a better solution is going to be some form of flow restrictor or pop
> off valve.
Popoff valves have issues, mostly with tolerences. A flow restrictor is a better
idea, but sizing it is an issue. If N/A boy over there gets to run a 1050CFM
Holley Dominator, do I get a 1050CFM restrictor? Do you use different
restrictors for different cars? Different models? Do I have to pay for it, or
will the SCCA mail me one? Etc. Not impossible to overcome, but it'd need some
thought.
DG
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