GTR pistons in an RB25DET - off boost response

[Warpspeed]

I have been thinking about this plenum/runner flow business a fair bit myself lately.

Testing the static flow of each runner on a flow-bench individually means nothing really, because you are flowing only one runner at a time, although getting them all the same is probably a good start.

What you need to do is flow all the runners together at the same time, so that for example, cylinder number one sees five cylinders worth of air passing right across in front of it.

The runner and plenum flows should be something like what happens in the car. To make it even more real, you might have to drive the inlet cam with an electric motor, so the runners pulse in turn.

I have not done it yet, but how about blowing air into the plenum under pressure, turning the inlet cam with a motor, then measuring the flow out from each combustion chamber with six identical orifice plates ?

The turbulent air into the plenum would approximate pretty much what comes out of the intercooler I would think. You could drive the inlet cam at any speed you really want as well. The only thing missing is piston action and exhaust reversion, but I think this would be as close to measuring reality as you could get.

Probably an ideal tool for plenum design testing.

I will definitely try this when my new larger flow-bench is completed, I should finally have enough airflow to do it.

[Roy]

A good starting point is Computational Fluid Dynamics Software. If someone can find pirated software (licence is worth tens of thousands) i can use it.

You see all the big car makers with their 3D modelling, its a very good place to start, and if you have access to the software you can setup accurate models. You still need to validate the model with calculations but you woud be surprised how easy the software is to use.

Anyone want something modelled in 3D then PM me:D

Sadly dont have access to Finite Element Analysis Softare (Forces and stresses) or Computational Fluids Software (looking at flows) but can still model stuff.

Sorry about being off topic!

[Cubes]

Good ol' Emule has quite a few PDF's etc on the above.. but no software..

[Roy]

Here is a quick go i had at the Std RB inlet manifold. Took me bout 90 mins. The idea is you can then dump this 3D drawing into other progrms that allow fluid/stress/motion analysis.

[Roy]

...and same model different angle

Ill shut up now and let RB25 owners tell you what pistons to use.

As for compression ratios im looking at using up to 9:1 on the RB20 im building.

Im hoping to get good low rpm response, and get the turbo on song as quick as possible. (Still have to check with engine builder that im not building a hand grenade)