RB26 2pc Intake Plenum

[Allan74]

Going through some old pics that I have collected since owning a skyline, I found these again. I took screenshots of Videos of a 1998 Drag Event in Japan after noticing this unique Plenum.

http://www.gtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwr.com/downloads/pics/1998-99%20GTR%20Drags/2pc_plenum/rb26_drag_twin-3cyl-intake.jpg
http://www.gtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwrgtrpwr.com/downloads/pics/1998-99%20GTR%20Drags/2pc_plenum/rb26_drag_twin-3cyl-intake2.jpg

I have often wondered why something like this was never mass produced, as obviously this was custom. It's sometimes looked at, that in 'TT' form, the RB26 is managed as dual 3 cylinders (ya, thanks A'pexi Djetro).....and this just seemed to take that 1 step further.

A bit of a plumbing clusterfuck, yes......but definately FINE tuneable compared to a single 6 hole/runner intake plenum.

Cheers,
Allan

[XXXsebXXX]

It should get better result with the twin plenum if the tuning is done cylinder by cylinder because its easier to have an equal air flow to each cylinder.

[mcfly]

this will just make two cylinders you need to watch rather then one. I can see issues forming if you did not have a balance tube between the plenums. if one turbo started spooling ahead of the other the cylinders and ecu would not like you. I really liked those drag videos when i found them and hosted them :P

[Skym]

Seb, individual cylinder fuel trim.

Mcfly, wastegate actuator related?? Not all wastegate actuators produce exactly the same boost level. Adjustable wastegate actuators could help to tune it out on dyno. ECU tune probably would be another area with individual cylinder fuel trim, as to make the cylinders produce equal amount of exhaust gas.

[mcfly]

no i was more referring to unequal cylinder pressures creating additional stresses on crank/rods/bearings. front cylinders running a bit hotter for example therefore spooling front turbo faster and then it multiplies since you cannot equalize the pressure between the manifolds. Seems likes a quick way to break something.

[Skym]

I would have thought that to, considering those cylinders are closest to radiator.

A tuner friend was telling me the rear 2 cylinders run the hottest (I gather, due to being closest to firewall, etc). He says that is where stock headgasket usually fails. I would assume that's where stock headgasket gets crushed from head getting too hot, warping. I guess it makes sense, as hot air from radiator, etc builds up around firewall.

This article from Japan backs up what he was saying about rear 2x cylinders running the hottest on RB26 engine in a R32 -

http://www.jdm-option.com/eng/feature/06_02/r32.html

He seemed to add water galleries?? around those cylinders to solve problem. Nismo supposedly do the a similar mod to galleries (enlarge them) on N1 head, N1 shortblock.

[SuperHatch]

I would think the rear cylinders run hotter not due to engine bay temps being hotter near the firewall, but due to those cylinders being the farthest from the coolant inlet/outlet on the engine. If there was a way to feed the coolant in the middle of the head/block it would stabalize temps better.

[mcfly]

I was just making an example of a potential problem. But while we are here, yes the rear of the block is hotter then the front but that does not mean the cylinder temperatures are higher as well.

[SuperHatch]

I would have to respectfully disagree with that.

[DrMango]

if those cylinders are getting lean then I would assume that the cylinders McFly speaks of could be hotter than just the rear of the engine just because of being close to the firewall issue

Kyle

[Allan74]

Let's just call it:
1) Lean(er) condition.
2) Tight Spaces (firewall).
3) Furthest from Water outlet.

........and move on to the next thing ;)

[Skym]

Interesting. I just used, etc for the rest. :D

How much air do those 2x intake plenums flow???

Limited by butterfly's inside throttlebody's, or are they upgraded???