Turbo inlet manifold design

[sluggy]

Have a read of this ... http://forums.aussieveedubbers.com/viewtopic.php?tid=103157 .... It's VW stuff but I'd be really interested in any knowledge outside of this. I'm not convinced super car manufacturers would allow body shape to dictate a shitty manifold design....

[NaN]

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[DJZ]

The Audi race car manifolds are interesting but yeah, you don't need the fanciest of manifolds to make a lot of power.

 

 

 

 

[Rookie]

I'm not convinced super car manufacturers would allow body shape to dictate a shitty manifold design....

 

You should beleive it, everything is made to a price. Why would they put a manifold that can flow 1000hp onto a car that only makes 500hp? They wouldn't, that is just wasting resouces and therefore money.

[NaN]

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[eke_zetec_RWD]

Since a mk1 escort is a super car it did dictate the shape ov the manifold I made. Throttle had to enter the bottom of the plenum in the centre. Internal trumpets which I added later did add torque at low rpm.

[kpr]

^ should work better than feeding it into the end anyway.

 

i've always thought of it as "filling" the plenum.  or pressurizing it evenly.    from there on same deal as n/a,   good sized bellmouths,  tapered runners that are tuned to rpm required.  helmholtz  etc..  

 

usually you need to run shorter runners for a big turbo setup. to tune to higher rpm, but if you can make them long enough to catch a stronger pressure wave, worth trying.

 

on a big turbo setup.  i usually try setup the inlet manifold so it  comes on 1000rpm or more after the turbo comes on boost. which should get you a wider progressive powerband with more peak power. make sure your engine is going to handle the rpm first!   if you set it up when turbo comes on boost  will get a massive surge of  power then it will fall over. resulting in narrow powerband.   (this usually happens when someone chucks a big turbo on a car with factory inlet manifold.)    

[eke_zetec_RWD]

Yea I knew it would work mint. Quite even flow. Trumpets are a must. Also has to be strong. Welds in places where flexing won't induce cracking, 20psi of boost puts a lot of force and flex into a manifold then so does vacuum.

[kpr]

harmonic vibration can also suck when using thin wall, at decent lengths  

[flyingbrick]

Iv heard that shortest runners possible is good for turbo.

[eke_zetec_RWD]

Good Turbo repsonse is partly due to good n/a design. And remember peaky turbo motors arnt fast. Except on the Internet.

[NaN]

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[anglia4]

Yea I knew it would work mint. Quite even flow. Trumpets are a must. Also has to be strong. Welds in places where flexing won't induce cracking, 20psi of boost puts a lot of force and flex into a manifold then so does vacuum.

 

It was amazing at nats watching YoeddyNZ's viva try and suck the manifold inside out when he revved it.

 

(still got the noise in my head Alex! )

[mjrstar]

Can't say i have seen this issue with factory manifolds falling over top end wise (well there are plenty of factory evo's making 400KW plus on untouched inlet manifolds)

 

As DJZ states You can get away with some reasonably rough tactics /factory stuff as far as inlet design and still make Ok power when forced induction is in play

 

there's alot of thought around this; but the general rules are something like....

 - - pressure release valves (BOV's) work best on the manifold, at it's rear most point, they also work well anywhere else but close to the turbo

 

 

I would suggest not mounting a BOV on the inlet manifold (unless it has ITB's) because it really isn't going to work.

 

Good turbo response is mostly down to good turbine wheel / exhaust housing selection.

[Jase]

ok now how about for diesels ? turbo ld28 has daggy factory manifold with long runners very small plenum and very small intake at one end.

I expecially like that audi design as it would convert a turbulent mass of swirling air into a sheet of uniform air to be drawn into the bell mouth and runners .

I reckon a bath analogy might work pull the plug on the bath and start scrubbing the scum off ,the water becomes waves with uneven flow going down the plug, put a board across the plug end with a gap underneath and even though theres turbulence in one end the flow will be even at the plug.

the pressure drop from the small intake runner through to the main plenum through the slot would likely give the air a very standardised turbulence and density as it enters the main plenum.

i'd love to see a smoke cutaway video of that working

[Jase]

solid works is the shit

[flyingbrick]

I reckon a bath analogy might work pull the plug on the bath

I wonder if air swirls down the inlet ports in different directions depending on if in America or nz

[Spencer]

There is a cool thread somewhere on the net about a guy building a audi style manifold for a 6 cylinder, may have been for a L series? (ling post) Anyway the guy ran CFD of his designs and the first few iterations had some massive flow problems to certain cylinders, took some work to get it right. Just trying to wing making a manifold like that on a 6 can lead to results worse than using a stock shitter.

[flyingbrick]

Not turbo- but a great example is the ls6 manifold vs the ls1 manifold.

The only difference that I recall is the shape of the plenum floor ( which dictates plenum volume) ls6 is larger and gains something like 30hp over the ls1 piece.

Comparing the two pieces its easy to assume GM deliberately derated the ls1 with that first design.

I do wonder how much power these different companies engines could be producing if politics played no part. Often revisions include bigger valves, bigger throttles, higher compression etc etc... They KNOW all this makes more power so why not just engineer it to 100% in the first place?

Is it so that their special versions are easier to produce? (Eg hsv) who knows.

[Spencer]

Because its not needed? economy? cars that meet a price point in the market have less specifications?

 

its like saying why don't we all have a top fuel motor in our camrys? why didn't every Chevelle come with the LS6 package 454? how is a rainbow made?