Special Stage Forums banner
1 - 5 of 5 Posts

·
Registered
Joined
·
590 Posts
Discussion Starter · #1 ·
I sat down with a friend at lunch today and somehow we got onto the topic of restrictors.

I guess that since they are inevitable, I may as well look for the silver lining in the dark cloud.

Here is what I came up with:

Top cars will be a lot closer in power since no amount of money will produce more airflow through a restrictor once you have the shock wave in the throat. This is a law of nature and physical impossibility. Therefore, the top $$$ guys will have to spend their HUGE amounts of $$$ going after the 'last 5 percent' that is possible for a given airflow.

It *should* separate the true 'drivers' from the 'big check writers' in a pretty decent hurry since many will no longer be able to be 'saved by the throttle' to make up for a mistake or lack of corner speed.

34mm restrictors are already well known in Europe and Canada, so tuning information is not *that* hard to come by and is available to just about everyone who knows what questions to pose to whom.

It will not force us to give up some roads that we *truly* enjoy. In my case, Brooklyn Tavern and Smith Creek. The cars will be slower, albeit marginally, but the *perception* of increased safety should go a long way with the non-rally types.

There are drawbacks, however:

Engines will have to be 'purpose built' and mapped to optimize torque in the midrange since you will 'run out of air' at the top end of the tach. This can be expensive. I'm hoping to build ONE engine that will go a good amount of time between major maintenance and just go with whatever power output I can get RELIABLY. I'm guessing something in the 290-310 range based on my budget.

I'd be *very* surprised if we didn't eventually see something along the lines of the 'Toyota *special* restrictor' at some point, given the money being spent by top teams.

I still don't like the idea, but I guess its deal with it or park it and I like seeing my rally friends on the event weekends.....

I always considered knowing when and how hard to use the brakes part of driver skill, just like controlling the big BHP beast....but I guess brakes will be getting a good bit less use in 2005.

Just some thoughts....YMMV

Matt Manspeaker
Seattle, WA USA
89 323GTX - OPEN
97 Escort Cosworth - WIDE OPEN
 

·
straight at T
Joined
·
2,472 Posts
>I sat down with a friend at lunch today and somehow we got
>onto the topic of restrictors.
>
>I guess that since they are inevitable, I may as well look
>for the silver lining in the dark cloud.
>
>Here is what I came up with:
>
>Top cars will be a lot closer in power since no amount of
>money will produce more airflow through a restrictor once
>you have the shock wave in the throat. This is a law of
>nature and physical impossibility. Therefore, the top $$$
>guys will have to spend their HUGE amounts of $$$ going
>after the 'last 5 percent' that is possible for a given
>airflow.

No, the more money will go towards optimizing the low-end torque, as you mention below, just like the WRC cars. The costs to run at the top likely won't change - they never have in any form of racing. If you can't afford to have the fastest spec car, you still won't be able to - its that last 5 percent that makes all the difference, regardless of the rules.

>It *should* separate the true 'drivers' from the 'big check
>writers' in a pretty decent hurry since many will no longer
>be able to be 'saved by the throttle' to make up for a
>mistake or lack of corner speed.

See above.

>34mm restrictors are already well known in Europe and
>Canada, so tuning information is not *that* hard to come by
>and is available to just about everyone who knows what
>questions to pose to whom.

Tuning information is likely easier to come by than 40mm because 34mm has been the GpA/WRC size since the mid-90's (I believe).

>It will not force us to give up some roads that we *truly*
>enjoy. In my case, Brooklyn Tavern and Smith Creek. The
>cars will be slower, albeit marginally, but the *perception*
>of increased safety should go a long way with the non-rally
>types.

I doubt if the top cars are going to be a whole lot slower. The teams without the money to build a properly optimized drivetrain are likely going to be the ones to suffer the most. You might still see restrictions on stage roads.

>There are drawbacks, however:
>
>Engines will have to be 'purpose built' and mapped to
>optimize torque in the midrange since you will 'run out of
>air' at the top end of the tach. This can be expensive.
>I'm hoping to build ONE engine that will go a good amount of
>time between major maintenance and just go with whatever
>power output I can get RELIABLY. I'm guessing something in
>the 290-310 range based on my budget.

If you build it to last a long time, you aren't getting that last 5 percent out of it.

>I'd be *very* surprised if we didn't eventually see
>something along the lines of the 'Toyota *special*
>restrictor' at some point, given the money being spent by
>top teams.

What, you are suggesting somebody would CHEAT? ;-)

>I still don't like the idea, but I guess its deal with it or
>park it and I like seeing my rally friends on the event
>weekends.....

Exactly, its just like any other rule change. Some people will deal with it and some people will park it. I don't think a lot of people parked it when Canada changed over.

Adrian
 

·
Registered
Joined
·
590 Posts
Discussion Starter · #3 ·
I'm *not* going for the last 5%

I can't write the big check....

Matt Manspeaker
Seattle, WA USA
89 323GTX - OPEN
97 Escort Cosworth - WIDE OPEN
 

·
Trogdor
Joined
·
915 Posts
>
>
>Top cars will be a lot closer in power since no amount of
>money will produce more airflow through a restrictor once
>you have the shock wave in the throat.

Depends.

If the restrictor is a defined shape (square edged hole) then probably.

If the restrictor just has to have a certain ID a certain distance away from the compressor blades... there are [link:www.theoldone.com|*SOME*] people who have been having [link:http://www.theoldone.com/articles/The_Soft_Head_1999/|*VERY*] good luck in creating shapes that achieve supersonic flow in engine ports, and one of the quirks of supersonic ports is that they tend to be self-scavenging.

It might not work. But one thing that seems to resonate through all motorsports is that restrictions just make it cost more, they don't really cut the speed down.
 

·
Registered
Joined
·
250 Posts
The difference in the mentioned case is the intake speed isn't what you're going for or what matters. It's mass flow of air.

The point that you are missing is that once a shock is formed (sonic velocity at the narrowest point) at the throat of the restrictor, it's choked and you're finished.

Thermodynamic property of the shockwave is that you will flow no more air through that space, even if you had infinte pressure on one side, and infinite vacuum on the other.

Greg,

Vive le Prole-le-ralliat!!!
 
1 - 5 of 5 Posts
Top