Offroad-Express

Crash bandicoot wrote:nissan spent multi millions on r&d, there gtr plenum is probably the most efficient design for a factory inline six.

google it a study the shape of it.

No its not . The air flies in and piles up at the back wall infront of number 6 .

The nismo one is quite different . And there is a million aftermarket ones . So it cant be that great .

The r n d that went into tge vg30dett manifold is public knowledge . Go read some of that . That was interesting

you can't pile up intake charge when you have intake cycle vacuuming it away, wedge shape is just to maintain air velocity and volume down the length of the manifold.
i'm running one on my gq currently with very lean afr's and 450c max egt's , very happy with it plenty of potential to crank it up.

Good to hear your style of manifold is working mate. Always good to see some fresh thinking

running a standard wedge plenum on the gq its doing fairly well too.
next step will be longer runners trumpets an a more tech split plenum for it.

Do you have your own DC AC tig welder?

nah just a mate runs A street custom alloy fab in morrinsville,
does a good job at homer prices and doesnt mind my weirdo designs.
id love an hf start tig to replace my scratch start multi welder set up .
shed up an extra room on the hut got priority for funds though

i think its time for the next evolution.
a quick google search will reveal a miriad of 24valve diesel in europe making up to 550hp.
is that even feasible on a td42? probably not...but one thing you do notice is the use of the standard manifold,
insignificant you may suggest? until you dig further an touch on volumetric efficiency harmonics and resonance.
so the theory of it is with each valve closure a pressure wave bounces back up the inlet runner at the speed of sound until it bounces off something else till it returns and repeats the bouncing back and forth till the valve reopens,
so by running a longer runner there will be less bounces and the pressure wave can be timed to be right at the valve in time for opening ie tuned length.

beauty of this is the calculators are all on the web already.

next step is fitting 280mm runners to the next manifold so that on every valve opening the 6th cycle of the pressure wave has arrived at the valve just as it opens

slidenyo wrote:i think its time for the next evolution.
a quick google search will reveal a miriad of 24valve diesel in europe making up to 550hp.
is that even feasible on a td42?

they are not far off that.
however they are breaking cranks rather regully which is imposing a limit.
the 2 valve per cyl head does make it very difficult.

probably not...but one thing you do notice is the use of the standard manifold,
insignificant you may suggest? until you dig further an touch on volumetric efficiency harmonics and resonance.
so the theory of it is with each valve closure a pressure wave bounces back up the inlet runner at the speed of sound until it bounces off something else till it returns and repeats the bouncing back and forth till the valve reopens,
so by running a longer runner there will be less bounces and the pressure wave can be timed to be right at the valve in time for opening ie tuned length.

beauty of this is the calculators are all on the web already.

next step is fitting 280mm runners to the next manifold so that on every valve opening the 6th cycle of the pressure wave has arrived at the valve just as it opens

most of that is all great in theory.
its also relative to the stye if intake port and big part of those calc's are vacuum based. on a lowish rpm diesel thats almost always on boost, the calc's don't translate into real world performance.
if you read through whats been tried and tested over the last 20 years or so, you will see that they actually recommend very short runners for the TD42.

short runners are perfect if you plan on making power at 10000rpm but the td42 is fairly rev limited so will benefit a longer runner to achieve higher v.e ,
and with boost a runner can be shorter to achieve the same v.e.
disregarding the numbers check an om606 manifold or a banks power manifold no such short lengths or directly opposing surfaces reside there.
the td42 crowd are still fairly behind in comparrison to the euros and yanks with the fixation being centred on fuel an boost whilst ignoring the maths and basic fundamentals of good engine dynamics

slidenyo wrote:short runners are perfect if you plan on making power at 10000rpm but the td42 is fairly rev limited so will benefit a longer runner to achieve higher v.e ,
and with boost a runner can be shorter to achieve the same v.e.
disregarding the numbers check an om606 manifold or a banks power manifold no such short lengths or directly opposing surfaces reside there.
the td42 crowd are still fairly behind in comparrison to the euros and yanks with the fixation being centred on fuel an boost whilst ignoring the maths and basic fundamentals of good engine dynamics

i suggest you go read and talk to the guys who have already been there and done it.

Good to see someone thinking outside the box.

sorry tweake but after a fair bit of research haven't found anyone who has seriously tuned a manifold for a td42.
plenty of flow matching and increased volume but am yet to see any tuned length runners.
beit thinking outside the square or not i'll get something blasted up an see how it goes at dirtdrags

td42 crank failure gets attributed to a fair few things.
imbalance
harmonics
torque and power.

rather than get lost in what has been done by the likes of swaffie ufi and trundles ,
i'm going to try copy some petrol principles like what i did with the split plenum and try get the engine working a little more harmoniously.
like on an om606 the runners are about a foot long which would be perfect for a v.e up to its 5000rpm redline , funnily enough they're then throwing holset 35-52s on them and making up to 550hp.
have yet to see a td42 manifold with foot long runners?

you guys banging different cam profiles at these thigns yet?
always miffed me that people don't seem to touch cams or cylinder heads when tweaking diesels in nz, it's always just about max fual and more boost

not yet but on the cards 248 duration could definitely be increased a tad.
see how the next intake goes with current fueling before doing cam and dual valve springs

from what i gather, the issue is head design. for some reason the long runners don't work well so they tend to focus more on just outright flow. the short runners match the head and tend to flow better.
build a new head design and i'm sure tuned intake would work better.

Cameron wrote:you guys banging different cam profiles at these thigns yet?
always miffed me that people don't seem to touch cams or cylinder heads when tweaking diesels in nz, it's always just about max fual and more boost

i can't recall off hand what the situation is with the td42 cams. i suspect the stock cam suits the engine well.

with some engines they change cams. a common one is the toyota 3l cam in a 2lt. a lot of it is down the characteristic of the engine to suit the vehicle rather than outright power and what the manufacture did.
eg 2lt tend to run a low rpm cam then use the turbo for the high end. fitting a 3l cam, which is more high rpm, increases the top end but looses bottom end. however as most of the vehicles are fairly low geared, the lack of low rpm is not an issue due to the effect of the gearing. also keep in mind it really only works in this case due to the engine working well in the rpm range to start with.

nissans td42 is designed primarily for low rpm. fitting a high rpm cam in it doesn't match well with the rest of it.
design a head for higher rpm and a higher rpm cam would work.

by the time you design and make a new head you might as well just put a different engine in.

can't argue the heads badly designed if no one has run a tuned manifold to suit?!
getting rid of the precomps and direct injecting would be ideal but probably not the cheapest avenue to explore

slidenyo wrote:can't argue the heads badly designed if no one has run a tuned manifold to suit?!

as i said before tuned manifolds have been made. theres tons of them around.
just about everything has been done to those engines.

i just don't see the point of repeating other peoples failures.
if you have something completely different that hasn't been done, great, try it and most importantly prove it works better.

i would make the usual 50mm lift manifold, dyno for a base line. swap over your one and see what the difference is.

borrowed from patrol forum , old Mav , he's done a lot of testing , on manifolds
With a good designed intake there isn't really any benifit under 7psi the std log does ok in this area. But once you push boost above this the system will not flow creating all sorts of distribution issues hence different egt values across the 6 cylinders mainly 1 and 6 which can see very big diffences in egt's over 3 and 4. Hence it is more an insurance to your engine life with a better manifold. For me i have only done most of my testing at 22psi and 18.5 to 21 AFR's. Its just impossible to try and compare power outputs from one to the other due to very different tunes required for the std manifold and modified system. Basicly what is does is to give you a lot more flexability with your tune for example boost values makes a big difference for lowering egt's, AFR lower at least 2 point on and on. But if you dont consider the flexibility to tune you could see a 20rwkw increase at my 22psi easy but really what i was looking for was torque graph change and this is what changes very much to the better. Also when driving the engine feels free and willing to rev and a hell of a lot more responsive these things you just cannot see or tune for on a dyno so it is all subjective but really for the TD it is well worth doing just for these subjective points alone. It really does make the TD feel like a nicer engine.

yeah read old mavs threads and definitely had a search for tuned length manifolds,
for something that has been done apparently struggling to find evidence.
problem with the short runners is the pressure wave could be oscillating away from the opening valve , causing your intake charge to have to overcome the pressure waves direction before it can charge the cylinder.

Almost need to make a manifold out of Perspex and film it then watch in a very slow frame rate.

slidenyo wrote:yeah read old mavs threads and definitely had a search for tuned length manifolds,
for something that has been done apparently struggling to find evidence.
problem with the short runners is the pressure wave could be oscillating away from the opening valve , causing your intake charge to have to overcome the pressure waves direction before it can charge the cylinder.

tho i wonder if the reflection wave is dissipating in the plenum before the next intake charge gets going. ie instead of timing the waves, get rid of them so they don't interfere.

old mav has tons of info on manifolds and intakes. well worth spending a few months reading it all.

Sounds like we need a td42 dyno day.....................

a interesting idea

Im keen for a dyno day, will give me a base to start from

yeah i wonder what my 290k engine is poking out now?
i know its surprisingly quick to other motorists but its not 550hp fast by any means.
have to tutu further an see what changes with different intake.
tweake pressure waves like sound waves will diminish with collisions with solids and other waves , losing potential energy that could assist in charging the cylinder.
like a tunnel rammed petrol motor you are utilising these pressure waves to increase v.e an essentially get boost for free.
on mr turbo diesel the benefit would be easier cylinder filling , even air distribution?
might just start by lopping a cylinder off a couple qd32 intakes an blast them together

Are the qd32 manifolds tuned to length? I like your thinking

slidenyo wrote: tweake pressure waves like sound waves will diminish with collisions with solids and other waves , losing potential energy that could assist in charging the cylinder.
like a tunnel rammed petrol motor you are utilising these pressure waves to increase v.e an essentially get boost for free.
on mr turbo diesel the benefit would be easier cylinder filling , even air distribution?

this is why i say go chat to to guys like old mav. there is a reason that it never worked for them and they spend huge amount of flow bench and dyno time on it. save your self the time and $$$.
you can make a tuned manifold easy enough and it will "work" but that doesn't mean its going to match everything else and be better than the typical intake mods.
your only looking at one small part of the whole picture.
what works in theory doesn't necessarily work in practice.

tuning the manifold is all good but is it going to be enough to counteract what you loose in plumbing losses and also manifold volume.
by making long runners your adding quite a bit of volume which is going to add lag.
you still need a big enough plenum to achieve even air distribution.

keep in mind the long qd32 manifold is the atmo version. the turbo version uses a short runner manifold.

a big turbo I have ,plus a balanced engine, the high big volume intake all add up to a reasonable system,