172 inlet?

[dunlop]

been having a think lately about fabricating a new inlet for my 172, almost like the style of mini-valvers inlet.

I was looking at it in the way that throttle bodies gain well, as they do in an airbox. so if i was to fabricate some 200mm inlet tracts into an aly/cf airbox with a larger tb, would this be worth while?

 

[BenR]

yes, almost anything is better than stock.....really.

 

[Andyman]

Theres a couple of threads kicking about on this subject. By reading between the lines the plenum and inlet set up can be improved upon 10 fold but dont think anyones done it on a F4R plus theres question marks over the potential to loose torque

Tis all above my head but these are just things iv read on it and picked off lol

 

[BenR]

Main problem is space on the aircon equipped cars, you have the alt in a very unfavourable position.

If you junk that then you'd still want to install a shorted rad to provide clearance for moving the plenum as far forward as possible.

We worked hard to come up with a design that would fit the stock engine bay of a FF1*2, however production costs have prohibited us from putting them to market. The slabs on billet would be so large and costly and the machine time would run into the 10-12hr margin.

However, even with short runners you can retain a solid torque curve like Dave's stupidly flat one.

 

[dunlop]

thats the sort of thing i want.

i dont want to junk the ac, as its still an everyday car.

but, i would want it to gain in the pwer and hopefully torque area's, as mine off cam is quite simply awful. and as i've got the engine sitting in the kitchen, i could quite easily fabricate a steel one in the evenings then get it made out of aly.

i've niticed the plenham on mini-valvers is quite deep, is this necessary or can i make it quite slim line almsot like a 20v vag plenham?

 

[Icarus]

Main problem is space on the aircon equipped cars, you have the alt in a very unfavourable position.

If you junk that then you'd still want to install a shorted rad to provide clearance for moving the plenum as far forward as possible.

We worked hard to come up with a design that would fit the stock engine bay of a FF1*2, however production costs have prohibited us from putting them to market. The slabs on billet would be so large and costly and the machine time would run into the 10-12hr margin.

However, even with short runners you can retain a solid torque curve like Dave's stupidly flat one.

I love that torque curve! Bloody hard to achieve something like that.

Cheers
M

 

[BenR]

thats the sort of thing i want.

i dont want to junk the ac, as its still an everyday car.

but, i would want it to gain in the pwer and hopefully torque area's, as mine off cam is quite simply awful. and as i've got the engine sitting in the kitchen, i could quite easily fabricate a steel one in the evenings then get it made out of aly.

i've niticed the plenham on mini-valvers is quite deep, is this necessary or can i make it quite slim line almsot like a 20v vag plenham?

Compensation for runner length with plenum volume to an extent......tiny plenums (where plenum volume is equal too or less than engine capacity), I've only seen work, in person, well with small capacity high rpm engines.

Vag engine, personally I wouldnt use as a model for anything

 

[BenR]

I love that torque curve! Bloody hard to achieve something like that.

Cheers
M

Drives very strange.......just as fast at 3000rpm as it is at 5000rpm.

Thankfully the 1.6's ports are a lot more performance friendly than the 730's, combined with the chamber shape. And its running UNDER 260 deg of cam duration!

 

[dunlop]

so if i were to build a plenham in aly, with it tapering in towards no.4 with a capacity of 2 litres,with as long inlet trumpets as possible it would see definate(sp) gains?

obviously would have to be mapped for it?

 

[BenR]

It would see definate gains yes, the extent would really depend on how well you take care of the airflow.

There are small details which make all the difference.

If you need some help feel free to call or email.....i prefer the phone though otherwise essays ensue.

 

[dunlop]

Something i've quickly knocked up, good theory?

 

[BenR]

No.

Dont worry about taper, it really does nothing.

 

[stan*]

Volume wise I'd make it as large as you can physically fit... definately more than 2 litres.

Have you thought about throttle plate size?

 

[stan*]

ok youve got a nice TB

 

[dunlop]

ah right, i remember reading about tapering it towards the last cylinder, so if i just made about 90mm square, that should be sufficient as 90x90x450mm = 3.6litre

 

[stan*]

in theory tapering slows the air near the entrance, so giving a better distribution.

ben have you got any data to show that tapering is not worthwhile?

 

[dunlop]

Have you seen gains from it craig? is there any inlets like this on any other car? i'll ring you tomorrow ben.

 

[powey]

Vauxhall corsas run inlets like these, think irmscher make them and dbilas.

Sure broster could fill you in

 

[mini-valver]

Dbilas make an inlet manifold for the K4M too but its still got the stupid curve up and around the head so cant see it being worthwhile over a custon one like mine.

Like Ben said, its a weird power deliver, kinda like an electric car, lol.

 

[dunlop]

your running quite mild cams though, so i would still expect mine to be 'peaky' but have alot better driveablilty.

And i can always go back to the standard inlet if i dont like it.

 

[mini-valver]

It'll be peaky, but no-where near as peaky as you'd think. The velocity stacks on mine are tiny and it still makes stock torque from 3k RPM.

 

[powey]

Get it done, then report back to us and we can all have one then lol

 

[dunlop]

i've been looking up alot of internet, and every one i look at is tapered towards the last inlet, and the inlet from the throttle body appears to be at an angle pointing towards 2/3/4

another note, any use having the injectors positioned like stand-off injectors?

 

[stan*]

depends on rev range...^^

I personally would include a taper.

What sort of overall intake length do you think you will be able to achieve?

 

[dunlop]

not sure yet, havent got an engine in the car to mock up with, but, i'm hoping to fit atleast 200mm trumpets, and then an plenham of around 450mm.

rev range is upto 7500rpm. so i would be better off going with keeping stockish injector postiton.

 

[stan*]

Have you seen gains from it craig? is there any inlets like this on any other car? i'll ring you tomorrow ben.

not tested tbh, the theory makes logical sense to me, so if I was fabricating one as a one of piece, I would include it (taper). Regardless whther there will be a gain or not with a taper compared to parallel profile, there is less chance of a loss... plus its no extra work to include it.

 

[dunlop]

i guess if i'm amking a mock up one out of steel, i can have a backing plate then make up a few outer plenhams to bolt on to test to see which works best, then properly fabricate one from ally

 

[mini-valver]

I cant say I've seen many stock plenum's that are tapered? Unless I'm just being ignorant?

VAG is pretty much square aswell, with reference to using it as an example.

 

[stan*]

im not saying it would be definately necessary for optimum results, port/tract volume and length will be the major influencing factors. But the theory at least would favour a taper.

How that transpires ont he dyno I cant say.

As I say, if i were making one I would include it as the theory is logical.

 

[mini-valver]

What about the distance between each runner and the wall of the plenum? If one is shorter, would that effect the flow into each cylinder as theres more volume in front of 1 than 4?

I love geeky stuff

 

[stan*]

I think there would be more of an effect on pulse reflection. I doubt to any significant extent though, as it not a large taper and the "width" in front of the trumpet is minimal compared to the overal width of the plenum. so the variation in profile the pulse is "seeing" is minimal.
There isnt strictly more volume as the whole plenum is the volume i,e the cylinder isnt JUST drawing the column of air infront of the trumpet.
The taper biases velocity, and so flow, to stop the cylinder nearest the throttle being "starved" from the oter 3 cylinders drawing a higher percentage of air into the rest of the plenum...i.e past that throttle/cylinder.

Ive not tested any of the above on my engine dyno, so cant comment on any significance in terms of real data/figures.

 

[mini-valver]

All seems logical I guess. Volume needs to be split equally (or as close as possible) between 4, with a TB at one end, is that even possible?

Interesting, head blag though :S

 

[BenR]

In this instance, the plenum dunlop mocked up, the taper will proove not beneficial, hence my comment, also I would consider the volume too small.

Taper can prove beneficial, but I think many are missing the point and best way to use a plenum. IF your plenum is small, if it is straight and ESPECIALLY dependant on the exit of the throttle body and its distance from the major plenum volume, then a taper can 'fix' some of the issues you might run into.

We could go into major detail for hours, and argue and argue, but we all do things our own way. But for me, I prefer to remember that pressure differential flows with a push, not a pull and that cylinder to cylinder exchange and mass air directional change is affected to a greater extend with a smaller volume and linear TB placement (horizontal axis of the runner inlets). I try not to generate 'velocity' in the plenum as this, through definition, requires a direction.

Daves works well with the flat front, large volume and offset TB position, all in respect of the short runner length and space restrictions we were bound too.

 

[ditz]

space issues aside, an inlet roughly like what dunlop has mocked up minus the taper,,

what if you were to put the tb right in the front bang in the middle of no 2/3


would that not do away with the problems you are trying to solve with the taper??

or would 1/4 be starved

 

[BenR]

If that were the case i'd place it in the middle from the bottom facing up with a 45 deg angle off the horizontal. You'd also have to place the TB off from the plenum slightly so you could blend it in over a distance.

 

[mini-valver]

Theres fark all room to put it there anyway!

 

[powey]

Would there be a gain from not having a taper and increasing the actual size because of this.

 

[dunlop]

I think this is what ben is saying, So far i've looked every plenham i've looked at, includes a taper, but then again it has a very long side towards the throttle body:

And is around 1.6x the cylinder displacement.

 

[dunlop]

another:

 

[broster@JAM-Sport]

Vauxhall corsas run inlets like these, think irmscher make them and dbilas.

Sure broster could fill you in

the standard vauxhall 1.4 1.6 16v inlet is very restrictive so respond very well to that type of inlet mod.

be interesting to see the gains on a clio.