×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Single Inlet restrictors

Single Inlet restrictors

Single Inlet restrictors

(OP)
Can someone advise where I might go to get advice of how to determine the cam and rpm range I should be looking to optimise for a road race engine? It will be twin cam 4 valve 1.8L. Looking for max performance. Inlet restrictor will be in the neighborhood of 24 to 25 mm. What help can you provide?

RE: Single Inlet restrictors

I would either use a vehicle simulation package or employ the services of someone that knows how to use one.
Typically you input data such as frontal area of the vehcile, torque curve, the CD value, the wheel base, the vehcile mass, gear ratios, losses, rotational inertia of the drivelne etc etc

Then this vehicle simulation package would then be used to simulate the kind of track or road use the vehcile would be subjected to. You could then change your cam timings, lift chatacteristics and re-input the data and examine the effects.
Vehicle simulation packages are usually very accurate-as they're very simple. I've completed several models, for Porsches and BMWs and compared the performance with REAL measured vehicle cycle test data or with magazines quoted performance figures with excellent agreement.

RE: Single Inlet restrictors

Bosch lapsim is great for the circuit simulation  sort of stuff and it has a free demo version that may be good enough

For the engine simulation side you might have luck with something like Performance Trends, which seems ok for cam timing but I'm not sure it can handle a restrictor.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Single Inlet restrictors

With Performance Trends you can set the CFM for the throttle.

If you can determine the CFM of the restrict or that should suffice.

As a rough estimate, I would get a Holley catalogue, work out the CSA at the venturi restriction for a range of sizes, then extrapolate the restrict or plate from that.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Single Inlet restrictors

The mass flow through the restrictor is governed by the fact that as volume flow increases, density falls.  The formulae of Q=V*A where Q is the volume flow rate and A is the area of the restrictor, and delta P = P0 * 0.5*M^2 will tell you how much actual mass airflow you should be using for calculations (M is the mach number for a given density).  Of course rho = P/RT, use this to find the density at any volume flow rate.

Quick calculation shows that for the 1.8 litre engine, you will have a pressure drop of only 0.23 bar at 7000rpm.  This means your air is around 3/4 as dense as it normally would be if there was no restrictor, hence you should see a reduction of 23% in peak power due to the restrictor, all things being equal.

Try to get a copy of GTPower for analysing your system.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources