Stavros

Ive asked questions about plenumns before, with my concerns about unequal airflow to each cyl on std and especially all these giant aftermarket cossie plenums that are appearing causing fueling issues (and also becuase the std GTR plenumn is the same), so....

How correct is this? Another problem with uneuqal airflow i didnt really think of before...

Makes sence to me, and makes me wana go buy a decent plenumn...

How right is it tho?

Stavros

BTTT already

Didi Mau!

I can see Sheadys online, got any views on this sir?

Mark Shead

The inlet manifold is a very diff thing to get right also how are the people testing them or are they talking crap and how are they mesuring HP per cyl as saying its taking more fuel doesnt mean to say it is,
As for Skylines the best prepared one I have seen is Kieth Cowie's one Biult by Rod Bell motorsport give him a call and see what he says about it.

Mark

PhilM

Hmm, Id say probably not a massive amount of difference in terms of wear etc.

If it was even remotely possible at work, would be great to stick a fresh engine on one of the dynos, run it for a week and strip to examine it, however not really possible .

Id not have thought theres too much wear, i'd imagine really it'd just be stressed between the centre line of the crankshaft and the big end, and if this doesnt come near any kind of structural limit anyway (ie, 95, 96, 95, 96 etc over 4 pots - yet the materal can take 200.). The crankshaft should always be floating on oil anyway, so shouldent get much extra bearing wear, as the crank always has a power stroke in a different place along it anyway.

Hmmm....as you said mate, any views, this is mine as a first year mech engineering student, so, could be totally wrong.

Would be great to hear what Karl has to say as an engine designer, as opposed to just a tuner, someone who has worked on dynos doing R&D (ie, at Jag, rather than 600bhp R&D that say Sheady might do).

Stavros

Mark- The JUN single throttle inlet system Keith uses is perfect, but is fookoff expensive.
Il probably keep the standard 6 throttle bodies and just run a different plenumn.

Main reason for this post is to confirm what the person says in the quote is true.

I agree that most/all these big inlets everyones loving these days arnt tested and probably dont flow anywhere near equaly to each cyl, which apart from underfueling issues (unless your VERY careful), will cause premature engine wear IF whats said in this quote is correct.

Also any airflow differences between cyls will be magnified the higher the boost pressure, so high boost and "special" plenumn i can see big problems in the long run...

whitneyd

I don't think it would make that big of a difference because stock manifolds are not equal and stock motors are made to last a lot of miles. Beside the crank and rods are rotating in an elliptical pattern not a straight up and down motion so it would take a lot more than just a 5% difference to start extra crank wear. Also I think if you got to far of it would make your idle suck because of the constant speed up and slow down of the rotating mass. But thats just my opinion.

Stavros

Stock turbo inlet manifolds are designed to be "fairly" equal, and the cars run low boost where it isnt as much of an issue.

It doesnt matter on n/a engines, only force inducted (turbo/supercharged) engines.

Wang up the boost, and/or use a less equal distributing inlet manifold and you got much more airflow to certain cyls than others, which means VERY careful mapping to not accidently melt a piston
(as if its not equal lamda and EGT sensors in the downpipe would show everythnig is fine, when infact some cyls are very rich, and some are dangerously lean).
And like this post is about, more power to produced by some cyls and not others surely throws the engine out of balance, and combine that with high revs and i can see a problem there too.

Sean Bicknell

Surely (well in my opinion anyway) a std cossie plenum aint spot on and gives more air to number three. And as a cossie on std type management gives the same amount of fuel to all cylinders, surely as the mixtures are different in each cylinder you are getting the same effect of one cylinder having more BHP than the others anyway???????

I wonder how much out the std system is with a lean mixture going to number 3 as described above???

I have got an EGT probe for each cylinder and T6 lets you do individual cylinder fueling, so surely having each cylinder running at the same temp and running a correct mixture is more important than any potential difference in power at any one cylinder?????

Just my opinion by the way.

Sean..

Stavros

Deffo agree with the fueling/cyl temp being THE most important thing, but the 2 things go hand in hand as problems, and both stem from unequal flowing inlet plenumns and lots of boost.

With EGT on each cyl and managment that can do individual cyl fuel adjustment, your sorted, but how many cossies/cars run like that?

keithcowie

Here are a few photos of my Jun plenum

Sean Bicknell

Keith, you are too BLING for your own good!!

Good to speak to you at TOTB by the way. Fingers crossed a few of the peeps on here will be showing you Skyline boys the way home next year!!

keithcowie

The way it went this year for me you should not have a problem

Hope to get the new diff fitted next week
then try the car again on the 1/4 mile at the end of the month

Keith

Stavros

BTTT as i notice Stu is online and Karl probably will be today, and any other techy types.

AlexF

This is a good subject and one many tuners have argued about for years in one form or another.

Its very similar to the question of how equally do you need to balannce the CR of each cylinder when modifing combustion chambers.

I personally don't think its much of an issue on 4 cyl engines as the transient opperating condidition of the engine will mask a fairly large variation on cyl to cyl outputs. Certainly in terms of wear it can't be an issue... if you think about it each cylinder is performing differemtly nearly ever time is fires anyway, as the revs and hence volume of air/fuel will be slightly different to the cylinder before it...

As for fueling and ware differences, if you take an A-series engine (mini) then the outer cylinders ALWAYS run lean due to the 2 port design... even tuned up to near 200 bhp/l there is still little evidence of excessive crank wear due to different power output per cylinder!

Just a few thoughts, nothing 100% thought through!

Alex

Karl

The effect of actual power imbalance per cylinder has no direct detrimental effect to crankshaft or bearing wear.

However the issue is AFR imbalance between cylinders caused by lack of individual cylinder trim ability.

Since I run weber mgmt on my car I have over come this by monitering individual cylinder EGT's and using injectors with normal variance in their flow rates to suit each cylinder.

That said my plenum has only 5% air flow variance from best to worst and this is also the kind of drift you can see in injector tolerancing so it's straight forward in balancing AFR's/EGT's by using a higher flow tolerance injector for the cylinders that flow most air.

foreigneRS

cunning. one way to get around limited mangement possibilities i suppose

helps if you've got the gear to flow test stuff though

AlexF

If you had seperate exhaust headers you could put a wide band probe mount in each and have a look at the end result...

Some experimenting with injectors might well help you.

Then again you could take it to Karl and he'll do a top notch job for you!

alex

SeanT

The original issue (crank flex / bottom end wear) will only present itself on engines with more than four cylinders IMHO as there is only ever one power stroke at one time in a four pot four stroke.
However, with more than this, surely the pistons will be in different positions on the power strokes at any one time, and thus making different power each at any instant anyway - so the problem in effect happens whether you get it perfect or not and is just another thing that the crank has to deal with regardless - or have I got the wrong end of the stick?

AlexF

I think you have the right end of the stick... but I dont think it matters...

Crank flex is a fact of life, everytime the cyl fires it accelerates that journal and hence the whole crank flexs as it catches up.

alex

foreigneRS

i've got an egt probe in each header so would be able to trim my fuelling that way (if i had management capable of it). obviously could do it by swapping injectors about, but don't have access to a large stock of 803's to select from.

was wondering about separate ports for the wb lambda too, but was also thinking of taking out a small sample from each header with a small bore stainless steel tube from fittings on the manifold and passing it through a chamber with the wb in it and then out to atmosphere. i guess it would work if the chamber was basically open to atmosphere at the outlet so didn't pressurise and affect the sensor? any ideas on this?

Karl

foreignRS

The problem in that idea is the flow rate through the small bore tube off each header would be insufficient in comparison to the sample chamber, and the vent to atmosphere would be a dilution point.

The theory is sound but being able to get the correct flow rate of exhaust gas in order to get an undiluted sample would be difficult.

foreigneRS

that's what i thought karl. thanks for confirming it.

Stu @ M Developments

iTrader: (12)

Wheres all the arguing and bitching gone from this technical topic? Has it been moderated?

Top Discussion guys

I also dissagree that it can be an issue, simply due to the already highlighted point that since we have varying throttle and loads etc the loads imparted on the crankpin per cylinder will never be exactly the same anyway, except perhaps at idle and under WOT on a flat road.. and thats negotiable..

foreigneRS

i'm not sure that i agree.

if one cylinder on a 4 pot engine (for example our beloved no. 3) has 5 % more airflow, and we trim the fuelling to optimise each individual cylinder, no.3 will surely nearly always have a corresponding higher load on it than the others.

whether that higher load is detrimental in temrs of 'wear' is unlikely.

i'd say it's much more important to have the fuelling right for each cylinder with the associated load difference, than it is to try and average the fuelling across all cylinders and risk a meltdown in a higher flowing one.

Phil

iTrader: (1)

I don't think that many engines producing the sorts of power for it to be of any importance last long enough for mains bearing/crankshaft wear to be an issue!

Stu @ M Developments

iTrader: (12)

Im talking about the topic question..

Will it cause extra wear on that cylinders bearing. I say its very unlikely.

AlexF

CozzyBrom

i dont know about skylines but big plenums are not a problem when you got injector trim get a proper ecu if they trim each injector

GARETH T

top topic, and would lvoe to comment but its all been said, but someone else might wanna read

Stavros

Individual cyl trimming is fine, but still means you need a EGT hooked up to all cyls, which isnt common (usualy jus one in the downpipe) and a pain in the ring, surely?

AlexF

Yes it would be.... but do you want a fast car or not

GARETH T

but it is simple to install and cheap

CozzyBrom

yes i got 5 temp probs going in mine i got the one in at the min and at £30 a probe thats cheap as chips
so its not that expensive

Stavros

I might jus spend 800quid on the on the Nismo Z-Tune plenumn and be done with it, lol

Would be 1st in the UK with it i reckon too....

keithcowie

Go the full hog and spend £2000 on the JUN Plenum


Keith