Date: Thu, 24 Jun 1999 09:18:21 -0400
From: dg50@daimlerchrysler.com
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?
In a class faster then they should be, in anything above stock. There are
some that look good, but most don't. I think the Talon is one that can be
made to do it, but the whole car is going to have to be right. The hot ESP
cars have had a long time of development, and it will be tough to catch. I
see why you want the up/back date, but I have to agree that alowing it may
cause trouble with other cars, the motors are VERY different. The entire head
is different, and I think the pistons are too. Do we then allow V-8 head
swaps to get more compression on a motor with better flowing heads?
<<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 have seriously thought about buidling an ESP Supra, that is one I noticed,
but the car is SERIOUSLY heavy.
< 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.
I have a big problem with this. On my first gen Talon (TDO5-14B) the waste
gate solonoid would close and drop boost to 8 psi or so any time it went over
12 psi. I monitored it with a test light. Iff all of the hoses are connected
right, and you have stock or better flowing exhaust, that is all you are
going to get, in ANY GEAR. If you are making it creep higher with a downpipe
blocking the waste gate outlet, you are using a very creative CHEAT. The
stock gate has no trouble keep up UNTIL you do something else to make it get
over 15 psi in the first place, I run turbos, I know how they work.
If you have anything that is NOT operating the wastegate solonoid at the
stock pressure of the bigger turbo, you are cheating. If ANY of the wastegate
hoses are not stock size or length, you are cheating. Theyraise the bost over
the spring preload by leaking air out the solonoid, this is a critical
balance, and all of it has to be STOCK. The bigger air flow meter of the
later cars is a legal change as would be no air meter under the rules, so you
will pick up some boost there, but the gate should still have full manifold
pressure applied if the boost goes over 13 psi, it will open, and the boost
will drop.
> 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
< 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)
Some of them are, and the motors are basically the same, but once again have
different cams and compression. Talk about opening a HUGE EXPENSIVE can of
wormsa to find the hot setup. If you were not allowed to do the swap, look
how much it would have saved you. And any newcomers would not have to spend
it either. If you do start choosing the turbo based on the course, now look
what you try to make others spend to keep up.
> 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.
I would say operating a control valve in the waste gate pressure hose is a
definate ECU control of boost, NO QUESTION.
> 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.
There were 3 chips available, they all upped boost. Getting a custon chip
back in 91 would have costed close to $1000 to pay for them to tool up for
it. Now days it is not so bad as many more ar fighting for the business. But
going to an aftermarket ECU would have made the car total protest bait. All
of the sensors would still have to be feeding the old ECU to operate the
stupid wastegate solonoid. On that car the gate spring opened at just 4.5
psi, the ECU acted just like an HKS EVC. It ran 9 psi all the time, and would
overboost to 12 psi if everything was cool enough and it didn't ping for up
to 10 seconds at a time. With the intercooler it would hold the 12 psi for
entire autocross runs.
> 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?
I agree with your spirit, and would love the tubo rules to be more open, but
I also see where they are coming from. You have one car where it has made a
difference. You honestly feel you are doing it legal and that is good. But I
brought up points where it could be easilly cheated on. There is a big
difference between getting more power through a legal od, and bending the
spirit of the rules to make even more power. The downpipe withthe restriction
in front of the waste gate was a BLATANT disregaurd for the spirit of the
rules, and I believe was the whole reason for this to come up. Within the
rules, the wastegate should have no problem keeping boost creep from EVER
appearing. I drove (and experimented with) a first gen talon for 9 years. I
know what the stock turbo will do. With the wastegate functioning, it will
not creep. even with NO muffler, cat, downpipe, etc. Until you get the boost
over 15 psi or so, then it wants to keep climbing at higher rpm, but to do
that required modifying the boost signal to the gate. I will be in
Evansville, I would be very curious to se how you have the stock controls
connected.
The ease of making huge boost on the older cars was exactly why they put the
leaking BOV (Bow Off Valve) on the new cars. It is a boost controller of
sorts on those cars. I hate that they did that, but they did. I feel a BOV
should be open, but in the case of that one car, the stock one should have to
remain in place. You should be able to add another for better flow when you
lift off the throttle, that is what a BOV is for. But putting on one that
does not leak allows more boost then the motor was meant to have.
<<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 will have my ST Unlimited car at Evansville. I have open turbo rules but
must pass emisions, which I did (I have the IM-240 results in the car) so you
can see what big turbos do. I run just 12 psi with a TO4E turbo. Lag is my
friend. Getting out of slow corners is easier than it was with the T-3 I used
to run. The boost climbs about as fast as the tires can take it, almost like
traction control, Under our local (RTP) index I have to beat ESP by a small
margin, and I have to pass emissions and run 7 inch wide rims and 225 tires
max. Yes, I have a catalytic convetor on the car. It is rear drive only, an
83 Celica.
> 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
I agree completely. As you can see, I really like turbos, and they have
gotten a bad rap in many racing classes. If the SP rules were more favorable
I would be more interested in running there again. An inlet restrictor has
been proven to work in many forms of racing. There would have to be different
sizes for certain combinations. Probably based on the weight of the car would
make most sense. A 2800 pound car should get less air then a 3200 pound car.
In Prepared they run 52mm which is not much of a restriction. With a good
turbo system that would easilly flow enough to make 400 hp. Beyond a certain
point, speeding up the turbo will pull more through, but the exhaust pressure
climbs fast, and the intake heat climbs too, and the power generated will
start to fall, even if the bost gauge still swows bigger numbers. People
pulling through small air flow meters know what I am talking about.
I hope this is all settled fairly for the largest amount of people. The
bigget error I see was someone at SCCA allowing this in the back date to
begin with.
Gary M.
I should be number 24 STU at Evansville.
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