Trying to do some rough calculations to see if this whole single plenum thing will work or if it'll just be a downgrade Using this calc: http://www.wallaceracing.com/intake-runner-length.php With these entries; Intake closing point: 46* -------------------------------- got this from an article, was "included valve angle", is this what I want? Average area of runner: 1300mm^2, 2 inches^2 ---- very roughly measured this off of the stock port size where the heads bolt to the lower plenum, like this, is this what I want? displacement: 186 ci RPM at HP torque: 5500 RPM at torque peak: 4500 cylinders: 6 stroke: 3.27" bore: 3.42" rod length: 6.067" --------------------------------------- from sale manual, centre to centre? Advertised cam duration: 264* (my juns) Intake lobe centreline: 110* ---------------------------- this is a bit sketchy, trying to work it out from the jap manual that came with the cams static comp: 8.5 desired RPM: 7500 --------------------------------------- is this desired redline or desired peak torque or...? runner length with DET lower plenum and 2" trumpet APPROX. 9.5" the only thing that throws me off about the calc is the plenum volume; unless that's what's recommended per cylinder? idk 1.9L still sounds low thoughts? -A
What about just working off the volume of the factory intake? I.e. lets say 10ltrs of volume in total for the factory intake, So build the single intake to 10ltrs feeding both banks? It obviously needs to be equal or bigger for it to be a benefit. Or put a Y pipe in front of the single turbo to feed all six cyllinders through the factory intake runners. The boost pressure will be the same across all banks.
These guys seem to be on track using a single turbo on a Z32! https://m.youtube.com/watch?v=QpDGfB2MQRU
you are talking cross purpose; plenum volume and runner length are totally different things oem plenum is nowhere near 11 litres and making it bigger is not how to make it better
best guess is, its not going to matter, if you want the best manifold design, use the stock one, since nissan techs sunk thousands of hours into developing it, Single turbo and Y pipe it. If you are hell bent on a single throttle body plenum largely for athstetics then build it how ever you like. Underbonnet clearance is going to limit runner length anyway. Make it look good and fit well. done deal
Every single plenum design I have seen have truncated the runner length. This has the effect of moving the peak power up the Rev band. Is that really what you want to do?
Pretty sure that dyno measures fart noises rather than HP It's pretty accurate - a LOT of fart noises coming from that car.
This was only an example volume. To replicate current throttle/engine conditions, your going to have to build an intake, plus runners. The engine needs X amount of plenum volume + X amount of runner volume. Your trying to feed two banks with one plenum, So both are relevant to each other. Alot of work to make a wheel that already turns.
Not really relevant to you but AMS has a intake manifold coming onto the market soon. Be interesting to see results from that once fitted and tuned on a few cars
http://twinturbo.net/nissan/300zx/forums/general/view/2579477/AMSs-new-intake-manifold.html This thing. Dont know if it's current or not, but it's popped up on my facebook feed a few times in the last few weeks.
Hahaha probably when it hits the market AMS will copy. I think the dude was joking with the title saying it is from AMS
Fair enough. I've seen it tagged with AMS , but it may be someone else's design. Point is, there may be a aftermarket option available soonish
thanks, that's good advice. I have no idea if the stock manifold is actually the best possible design to suit the purpose; it may well be but I flat out don't know. I don't want to **** things up thus this thread. It just may be that it will make very little difference in the end, in which case I'd have to weigh up simply how much money/time I want to put into a clean up and simplification effort. I already have a big **** off throttle body... Same. Honestly no not really, I guess what I'd have to find in my research before justifying the mod is whether a new design is possible that would increase power everywhere, even if it was shifting its bulk up top, so that despite that fact the car wouldn't be a dog down low. I know that's a silly big ask. I'm just thinking out loud. That, or do the maths first. Would be keen. Would give up on single intake simplicity and Y-pipe to it for the extra go and less fab work.
The only way you will ever know for sure is start with a good base engine (preferably recent build), get yourself an engine dyno, ensure all other variables are fully controlled and test different options back to back. Start with theory, end with real world testing.
To throw more wild speculation on the topic, do intakes have similar pulse effects to the exhaust? Keeping the banks on separate plenums/splitting them earlier with a 1-2-6 pipe design might help keep flow rates high and smooth.
AUTOSPEED!!! love auto. Anti... of course you figure out the volume before you build. Get a spare set of intakes, fill it with water, thats your volume and start building from there. Remember specific gravity of water is 1:1. 1kg is 1ltr.
