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What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

Mike everyone is allways complaining about the cost,cost,cost. By forcing competitors to use a 30.7 mil restrictor you just added 10,000 + to the build. 34 mil is mappable with a 2.5 unlike what all the un qualified post have said about the (bastard engine) By both of the series being different you are forcing one to make a choice. The choice should be how many events in each series can I run. Production is Production, PGT is PGT, Gr2 is Gr2, GrN is GrN, Open should be Open.

Rallymeister
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

What is the restrictor size in Canada?
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>What is the restrictor size in Canada?

Joe:

From the CARS rulebook:

1) All open class turbo-charged, 4WD vehicles must have a turbocharger air inlet orifice of 34 mm diameter or less.

2) In the event of turbo/supercharged engines being used, the nominal cylinder capacity is limited to 2500 cc maximum.

Doug Woods
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

The exising rules require a 30.7mm restrctor for a 2.5L 4-valve turbo engine

Matt
GTX #291
Arlington, WA
 

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Discussion Starter #6
RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

We (RA) inherited the 30.7 rule from the SCCA (ourselves?). I can't fault the previous PRB's decision on this, because it's always politically easier to go up on a restrictor size than down.

With all the inquiries / complaints I've jeard this year, large engined open class restrictors hasn't been one of them.

One thing I'm fairly certain of: If we changed to 34 or even 32mm for the 2.5, and someone who can drive figures out the map and makes it run good, The screams from existing 2.0 competitors will be deafening.
 

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don't cut
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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>
> Mike everyone is allways complaining about the
>cost,cost,cost. By forcing competitors to use a 30.7 mil
>restrictor you just added 10,000 + to the build.

Yeah, well going from 40mm down to 34mm on 2.0l motor added $10k to my build. I bitched and it fell it on deaf ears as well. The sanctioning bodies have made it clear that they are more concerned about ease of enforcement than they are cost (note: this may or may not be a bad thing). Personally, if I were you I'd throw the 2.5 up on Ebay and use the money to buy a 2.0L STI block and go from there.

Dennis Martin
[email protected]
920-432-4845

Ps. Actually the correct answer is no restrictor for anybody, because restrictors suck! }(
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>One thing I'm fairly certain of: If we changed to 34 or even
>32mm for the 2.5, and someone who can drive figures out the
>map and makes it run good, The screams from existing 2.0
>competitors will be deafening.

And one thing I guarantee -- you change it, and you'll find the guy who can drive and the guy who can map it good. If you're a serious competitor, you're not going to leave that performance potential on the table.

- Christian

Bjorn Christian Edstrom
www.christianedstrom.com
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

Dennis,

You are monthly reader of Racecar Engineering correct? They have had several articles on turbo restrictor tuning, it seems to me that they were under the conclusion that 2.5 (larger engines) would not be better off than the 2.0 with the same size restrictor citing that the larger displacement with smaller restrictor because much more difficult to tune and would have much worse VE and flow problems. One article in particular was referring to a 'limbo' homologation year for Citroen where they chose the 1.8 liter over 2.0 liter engine because they were getting a much better HP and power delivery. There speculation was that smaller engine with smaller valves kept port velocity up and therefore made a broader power band with the same size restrictor. My half of cent worth would be to say that the 2.5 tuning would suffer worse (narrow power band) than 2.0 engine therefore there would be no advantage and the same size restrictor could be used (probably made huge difference when restrictors were 40mm, but there is probably a law of dimishing returns once restrictor sie is reduced). Are there reasons why certain WRX teams change from crawford 2.4 liter engines back to smaller displacement prodrive engines once the 34 mm restrictor came into being?

Just releasing unrestricted hot air, flame away

Scott
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

Hasn't there been this push to "bring US rally inline with the rest of the world"? We reduced to a 34mm from 40mm for this reason. Group N has now become almost more plentiful than Open class cars. So, what does the rest of the world feel about 2.5L turbo motors in rally?
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>So, what does the rest of the world
>feel about 2.5L turbo motors in rally?

They ban them entirely. Which seems like a pretty tough line to take. Really, there are no other countries which have to deal with this. The 2.5l Subaru motor is a USDM and CDM anomaly.

- Christian

Bjorn Christian Edstrom
www.christianedstrom.com
 

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Discussion Starter #12
RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>
>And one thing I guarantee -- you change it, and you'll find
>the guy who can drive and the guy who can map it good. If
>you're a serious competitor, you're not going to leave that
>performance potential on the table.
>
>- Christian

...maybe a guy from British Columbia?

Changing right now would create a competition issue / problem where none existed before...but that doesn't mean it shouldn't be done.

If you're taking sides, would it be a mistake to side with a few 2.5 cars, and forsake the many more 2.0 cars? What if all the 2.5 cars sided with NASA, and all of the 2.0 cars stuck with RA because of this issue?

Either way, I believe RA have will a good supply of Subarus showing up at national events next year. ;)

BTW, you could save another $10,000 and run Prototype 2, right?
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

I was always of the general opinion that a restrictor plate limited the HP to about the same regardless of the engine displacement. That is, a 5L V8 or a 2L turbo would have about the same HP if forced to breathe through the same 32mm hole. Obviously that is not correct and also obviously, despite my being a member of SAE, I am an electrical engineer not an engine man. Any references for my edumakation?
TIA
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>>So, what does the rest of the world
>>feel about 2.5L turbo motors in rally?
>
>They ban them entirely. Which seems like a pretty tough line
>to take. Really, there are no other countries which have to
>deal with this. The 2.5l Subaru motor is a USDM and CDM
>anomaly.
>
>- Christian
>
>Bjorn Christian Edstrom
>www.christianedstrom.com

Actually starting this year, the entire world uses the 2.5L engine for the STI. The only market that still uses the 2L engine is Japan.
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>>What is the restrictor size in Canada?
>
>Joe:
>
>From the CARS rulebook:
>
>1) All open class turbo-charged, 4WD vehicles must have a
>turbocharger air inlet orifice of 34 mm diameter or less.
>
>2) In the event of turbo/supercharged engines being used, the
>nominal cylinder capacity is limited to 2500 cc maximum.
>
>Doug Woods
>
Then that's what I would use as my guide were I making the rules. We all want to encourage 'cross border pollination' (almost sounds dirty when you say it like that). One good way to do it is to make the preparation rules as close to the same as possible. Since plenty of folk on budgets are building very fast cars to your rules, no one could blame the car, or its restrictor.
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>Hasn't there been this push to "bring US rally inline with
>the rest of the world"? We reduced to a 34mm from 40mm for
>this reason. Group N has now become almost more plentiful
>than Open class cars. So, what does the rest of the world
>feel about 2.5L turbo motors in rally?

Teeee hee, stop it Grant! stop making sense!! tee hheeee hi!
Next thing you know you'll say something like, Gee golly winkie, if a guy can afford to just run out and buy a brand new car, he could probably just sell the 2.5 to some pimple squeezin' punk and get a EJ20 and shove that in and drive exactly the same "speed" (or lack thereof)

Maybe it's time to just stop farting around ansd knock off the folly of three classes for ESSENTIALLY the same type and conmfiguration of car.
Here's a new proposal:
Turbo 4wd class.
And if you have an old Maz-dog, or Eclipsed, or Gaylant, put the dough you so wisely saved into a good gear set and some turbo that last laonger than 35 minutes!!!

Conisidering that really Open, Peee GT, and Grope N are essentially all FULL of virtually identical blue Sub-a-rats what the hell is the point of three classes.

Enough silliness.


And if the silly 2.5 pos is 25% more Volume, shouldn't the restrictor be 25% less area if the car is Open, and 25 % less than Grope N or PeeGT, so where's the 28. whatever and 26mm choices?

Poo on all of those!
34mm (since you all let yourselves get railroaded by the slimey Dave Champignon writing directly to the old SCCA BOD) for all


and if some individual boy wants to tow to Mexico,or Argentina, or some _real_ International, then let that individual worry about getting a 32mm restreictor and a map that works

One big class.








John Vanlandingham
Seattle, WA. 98168

janvanvurpa (at) f4 (dot) ca

Vive le Prole-le-ralliat!
Vive Le Groupe F!
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

I'd like to see one size for all the turbo awd classes - makes sense to model it on GN - 32 right?

I know the open guys would complain, but it would make the competition even closer.

I don't really understand the allowance for a bigger restrictor in open - they are not WRC cars,so why not make our top class the equivlent to the 2nd tier class in the rest of the world (GN)?

All that said I am still not a fan of GN, the rules don't work for US models. Although the GN rules allow for more development (by the manufacturers) than PGT, the main difference seems to be the gearset allowance. At the end of the day it would be less expensive to run PGT...


Just an opinion I have no real equity in the decision.

Mike
 

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RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>I was always of the general opinion that a restrictor plate
>limited the HP to about the same regardless of the engine
>displacement. That is, a 5L V8 or a 2L turbo would have about
>the same HP if forced to breathe through the same 32mm hole.
>Obviously that is not correct and also obviously, despite my
>being a member of SAE, I am an electrical engineer not an
>engine man. Any references for my edumakation?

The forced induction cars get to force the air through the restrictor hole (under pressure, boost), thus they can get more air volume through the same size restrictor hole vs. a NA car. Since the goal of the restrictor is to limit power output, one needs to make forced induction motors blow through a much smaller hole than NA motors are sucking through.

Now, this concept can be extrapolated into the Open-class-forced-induction-restrictor-size-difference issue being discussed in this tread via the following oversimplified explanation:
If you're only concerned with leveling PEAK power output between different displacement turbo engines, then restrictor size arguments would be simpler (as you suggest above),...BUT... ,the real headache comes when trying to level usable power output through an entire RPM range. That's why people will hotly debate this samller restrictor-for-bigger-displacement issue.

Did that help?

Jim Cox
#558
 

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Discussion Starter #20
RE: What restrictor should a 2.5L turbo 4WD open class car use. (If 2.0L must use 34mm).

>
>The forced induction cars get to force the air through the
>restrictor hole (under pressure, boost), thus ....

Uh..no, they don't.
 
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