Turbo 1.8L Plenum vs. 1 into 4 performance concerns
Turbo 1.8L Plenum vs. 1 into 4 performance concerns
(OP)
I am building a Sunbeam Alpine 1.8L turbo motor and am currently trying to decide whether I should build a plenum to distribute the charge or would it be better to build essentially a reverse header 1 into 4 and force the air directly into each port. Conceptually I would think more flow and more even distribution could be achieved using the 1 into 4 approach, but are there any performance concerns?
I am running individual throttle bodies for each cylinder, 12 psi boost, and the plenum / inverted header would all be upstream of the butterflies.
In the event the plenum is the preferred method, how big should it be?
Any help is greatly appreciated,
Thanks
I am running individual throttle bodies for each cylinder, 12 psi boost, and the plenum / inverted header would all be upstream of the butterflies.
In the event the plenum is the preferred method, how big should it be?
Any help is greatly appreciated,
Thanks





RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
I'm no expert, but will the butterflys handle the 12 psi boost? Possibly so with individual Idle Speed Valves/Systems. My understanding is that the throttle body is normally upstream of the turbo. I would be interested in how this turns out. Keep us posted. Possibly you coud use a type of poppets or globe valves for throttling instead of butterflies, your change in throttle area would be more linear, controllable, and less flow losses if done properly. You could also design some swirl into the flow stream. If you took this route, my opinion is that the plenum with the apropriate taps would have less flow losses. I would rather see data though.
Interesting!
jomor
RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
Kai @ Wishbone Classics
http://www.wbclassics.com
RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
Long runners will give you better low end off boost torque, but the same long runners can be restrictive for top end airflow.
Long runner induction systems will work best where boost pressures are fairly low, and engine compression reasonably high. In other words a mildly boosted stock engine. Or put another way a turbo assisted engine.
Short runner systems work better for a more highly tuned higher Rpm application. Compression would be lower, cams more radical, boost pressure pretty high. An engine like that will be a slug off boost, all the performance comes from the turbo alone. No real attempt is made at induction tuning, all the air comes from the turbo.
It really depends what you want to use the car for.
RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
Some effort should be expended to assure equal flow, of course, but, unless you really screw up, this shouldn't be a problem. The cardinal rule in fluid flow: Avoid transition losses.
RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
Regards
pat pprimmer@acay.com.au
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RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns
If you want to do a turbo, do a search on this site and google for plenum design. I recall someone saying that the plenum helps to balance the flow between cylinders and a plenum volume of 2-3 times engine capacity works well. There are pulse tuning benefits but it's more complex than NA engines due to the pressure changes. For better balance the plenum should extend beyond the last runner and the better ones I've seen are tapered down in volume from inlet to end.
cheers, derek
RE: Turbo 1.8L Plenum vs. 1 into 4 performance concerns