12 replies to this topic

[Johnny D]

http://www.raetech.c...SIR-Catalog.pdf

Intake restrictors are being used by race sanctioning bodies to equalize performance
across a range of engine and vehicle types. RAETECH has employed CFD modeling
and Engine Simulation to develop an optimized series of Inlet Restrictors. Designing the
restrictor with the least flow loss at the required minor diameter provides optimal
performance for the competitor.
RAETECH has two restrictor series, GTL Restrictors in sizes 22.5 – 29 mm, and the GT
Restrictors with diameters 31 – 40 mm.

[NPiekarski]

I thought SIR was a Single Inlet Restrictor....what's all this sonic talk? How / what do these do so different from our current RP package?

[Johnny D]

Internal combustion engines combine fuel and air to produce horsepower. In the case of a gasoline engine, airflow is always the limiting factor. A single inlet restrictor predictably and controllably limits airflow and thereby power. Sanctioning bodies are increasingly mandating single inlet restrictors in an effort to predictably and controllably limit power. Raetech has developed a line of restrictors that have been optimized through computational fluid dynamics and designed to thrive in the harshest environments making them the most thoroughly engineered restrictors available for purchase.

Choke flow is the distinct limit when the restrictor will flow no more air, regardless of downstream vacuum. This occurs when the flow velocity reaches the speed of sound across the restricted area. The Raetech restrictor is designed to provide minimal effect up to choke flow and to achieve choke flow at the lowest possible pressure drop. Minimized pressure drop to achieve choke flow means an engine with a Raetech restrictor will have to work the least to achieve the power limits imposed by running a restrictor. Lesser restrictors will require running the motor in a higher rpm band to create enough draw to achieve the rules-limited amount of airflow. This increased rpm adds power-robbing friction along with wear and tear. Besides making more power, the best restrictor you can buy should save you money in the long run due to better engine life and longer intervals between rebuilds. The results of a restrictor on a simulated flow bench are shown below.

Charts
http://www.raetech.c...or_Function.php

http://www.raetech.c...Restrictors.php

J~

[Johnny D]

IMSA: United SportsCar makes latest round of performance balancing changes
Saturday, 15 February 2014

Sonic air restrictor sizes for all of the DP cars is still being evaluated, as is the maximum turbo boost level for Ford's 3.5-liter twin-turbo V6 EcoBoost DP powerplant.

http://www.racer.com...lancing-changes

[Johnny D]

2016 GTE Regulations

Sonic air restrictors will continue to be used for normally aspirated engines, while there will be a more rigid control on turbos.

http://sportscar365....ions-finalized/

[Johnny D]

BoP baby!!

http://badboyvettes.com/787

Pic of some
http://badboyvettes....rRestricors.jpg

J~

[Tom Hampton]

Are you going for a record number of consecutive posts?

[Johnny D]

Not now !!!
J~

[Tom Hampton]

The irony of my post was not lost on me. 

 

[Johnny D]

[Steve Scheifler]

As I've said each time this comes up, I suspect that if you study them closely you will find that they are not the solution to the 1.6 weakness. The point of any restrictor is to equalize max power of different engines. However, I believe that the design of these devices is specifically intended to maximize the power under the curve while limiting peak HP. They are probably better in terms of the stock ECU managing things, which is a plus, but my guess is that with one designed for a peak HP similar to what the NB has now will actually improve their torque curve, exactly the opposite of what we need. You could test one small enough to limit peak HP to about 5 below what a good 1.6 can do, and then the total area under the curve might be closer. What I don't think you can do is use them to limit peak torque, which is really the goal.

It helps to keep in mind that in any multi-make class the parity we have now would be considered phenomenal. SIRs don't get most of them as close as we are now because it is an advantage to start with a higher torque engine and let it be choaked at peak HP.

Perhaps there is something I'm missing so by all means look into it, but I'm not hopeful. What I can do is offer unlimited free dyno time if someone near St. Louis has a reasonably strong NB car they want to test.

[Johnny D]

Steve, it wasn't for the 1.6's. The idea was if nobody (the NB's) could make more than a given number, say 125hp. Maybe you wouldn't need to tear them down to check.

 

But looking at the graph I saw, as you stated that the TQ numbers would be even higher than what we currently have.

 

I guess something to think about if the 1.6's get a header and increase TQ and show a HP number, then maybe a SIR could bring in the NB's if the RP can't do it.

You'd have to match the increased in TQ with mod's to the 1.6 and then whatever the HP number was get the SIR, match that.

Even out weight, bla, bla, bla.

J~

[Steve Scheifler]

Ah, OK, it has come up multiple times in the past as a possible way to reel in the 1.8s relative to the 1.6. But even for just reducing the need for invasive tech the same applies, fudging the rules may still buy you enough additional power below peak to make the difference. Face it, the bottom line is that we're trying to achieve control comparable to sealed engine programs, and that's not possible without very invasive tech, which is why sealed engine classes exist.