[mrluke]

Very nice 👏.

Are you going to cut out the overlapping bell mouths? I would recommend to cut them at the touching. As they are symmetric they will form at the cut line exact the same shape, which makes it flow-wise much better. Just in case you do 3D print outs, on a single bell mouth fab approach, you would do that automatically.

How much volume to you provide for the plenum? The plenum volume is beside the shape of it the 3rd free parameter. You can design it via Helmholtz-resonance (cylinder displacement vs plenum volume) or do an 1D calculation method approach. In any case it is always power support vs. throttle response. If you don't race slalom races, where throttle response and control is most important, a rule of thumb would be around 2-4 Liter are ok for most applications. Maybe that helps.

Yes, the overlap will be resolved, at the moment I have only drawn one of the trumpets, the software is duplicating it across the other holes, this means that I can still make changes to the profile and they will all be identical. To make the cuts I need to first make each trumpet into its own object which is one of the last steps

The trumpets and the flange will all be printed together as one solid piece. This will be easier and more reliable than trying to join the trumpets to the flange afterwards.

The volume at the moment is the same as oem with the resonance chamber removed. Alot of the papers on intake volume are workarounds to having a restrictor fitted, but its easy enough to print some spacers to play with the volume and see what difference it makes

Next stage will be getting the last piece of the manifold scanned in which then opens up CFD fun for what its worth. I'm really curious to see what the flow distribution is like and whether there is room for improvement.

 

[LotusElise]

To make the cuts I need to first make each trumpet into its own object which is one of the last steps

That makes sense. Very good.

The trumpets and the flange will all be printed together as one solid piece

Good approach, 3D printing does make it possible 🆙.

Alot of the papers on intake volume are workarounds to having a restrictor fitted,

How do you mean that. What should be restricted and in which approach?

Next stage will be getting the last piece of the manifold scanned in which then opens up CFD fun for what its worth. I'm really curious to see what the flow distribution is like and whether there is room for improvement.

I am curious about your results. I have my doubt the 3D CFD is any near reality as you simulate only moments of an whole work cycle and you likely don't have a model for the fuel film and vaporization, which has an huge influence on VE of the engine. Anyway, I am curious what it will show as results...

 

[mrluke]

How do you mean that. What should be restricted and in which approach?

Many competitive race series require an inlet restrictor to limit maximum power.

You can see here pre-turbo

And here on an NA fsae engine

Because the air feed into the plenum is restricted, there is benefit in having a much larger plenum volume as it effectively stores air mass post restrictor.

On street cars we obviously dont need to work around a restrictor. I'm not saying plenum volume is not important, just that its use / requirement will be different.

I am curious about your results. I have my doubt the 3D CFD is any near reality as you simulate only moments of an whole work cycle and you likely don't have a model for the fuel film and vaporization, which has an huge influence on VE of the engine. Anyway, I am curious what it will show as results...

There are lots of factors that wont be accurately modeled by CFD, but that doesnt mean it has no use to us at all. What i'm really looking to gain from it is equalizing the air distribution between the intake runners.

There's no point making something that has perfect runner length, diameter, taper etc if the flow looks like this:

 

[LotusElise]

Many competitive race series require an inlet restrictor to limit maximum power.

Understood. You talk about an intake restrictor.

...What i'm really looking to gain from it is equalizing the air distribution between the intake runners.

Via e.g. a center feed plenum, like I suggested above (PRC plus customized center feed plenum)

Because the air feed into the plenum is restricted, there is benefit in having a much larger plenum volume as it effectively stores air mass post restrictor. On street cars we obviously dont need to work around a restrictor. I'm not saying plenum volume is not important, just that its use / requirement will be different.

A stored mass is only effective for one or two working cycles. What I mean is something which is always there. The alternation of load process is a complex system of more then one drivers. One of the bigger supporters are resonances, which squeeze out the maximum of energy available in the pressure oscillation during an work cycle. The resonance of plenum und chamber is one of them. You might be look into the CFD if they use an acoustic approach to model the pressure energy or if they include a temperature-pressure-correlation to model those oscillation. It is not natural that CFD codes include this as stationary flowing doesn't focus on that.

 

[mrluke]

I don't believe the PRC is a modular design? So somewhat trickier to modify in the way that I can the RSP.

So last night I pushed the button on the trumpets and a new back plate.







2-3 weeks until arrival, depending upon Brexit.

 

[LotusElise]

I don't believe the PRC is a modular design? So somewhat trickier to modify in the way that I can the RSP.

Yes, it is no modular design, but it has a way better clearance design as basis for your requirement to fit into the Lotus engine bay. As an extreme example you can find this here: Aggressive as fuck RSP custom "center feed" plenum | Honda / Acura K20a K24a Engine Forum

So last night I pushed the button on the trumpets and a new back plate. 2-3 weeks until arrival, depending upon Brexit.

Looks nice. But maybe you need to push the button a second time. How do you want to place bolts into the flange or do you place threats with screw nut. Anyway both will get challenging. I would design bigger bore diameters around the bolt axis in vertical to get the screw's mounted.

 

[drtye]

Allen socket head bolts with a tool like this might be able to reach around the bells,

 

[LotusElise]

Allen socket head bolts with a tool like this might be able to reach around the bells,

Definitely drtye. This allen socket approach would safe some clearance, but the bore diameter of the cut out of the bell mouths is the same as the flange bore. The screw head is always bigger to give a surface to be able to transfer the bolt force right down. I assume at least a 2 mm bigger radius. With the actual design it won't be possible, it has to be reworked. Just my two cents.

 

[mrluke]

Thanks.

I'm pretty sure the bolts will be accessible one way or another, there's plenty of room under the bells and the holes shown are 8mm to allow for inserts whereas the bolts are 6mm (well 5.8).

As suggested can always change to cap heads

That said these are only a mockup, i'm not expecting them to be a final product but hopefully I can mount them and start testing for durability.

But I will happily bet you a beer that I can install the bolts without too much bother.

 

[LotusElise]

But I will happily bet you a beer that I can install the bolts without too much bother.

I am not sure if it will arrive due to the new mess around the Brexit 😇 . These are M6 or M8 bolt threads?

 

[mrluke]

M6 threads.

I dont want bolt the plastic directly so it will have metal (likely brass) insert which is much more robust. Therefore the holes are oversized to allow for installation of the inserts.

And FWIW I'm aware of unmodified elise's with the RSP manifold fitted, we'll see.

 

[mrluke]

I love delivery day! Wasn't supposed to be here until Tuesday









I did manage to get all the bolts but the bottom two were a bit awkward to tighten. Cap heads would work but now I have the physical part, making the cutout larger doesn't look as bad as it did in the 3d model so i'll do that.









Blown away by how accurate the hole placement is.

 

[LotusElise]

Nice progress mrluke 🆙! Are you satisfied with the surface roughness of the bell mouths? How do they align with the runners? I can't see it clearly in the picture.

Cap heads would work but now I have the physical part, making the cutout larger doesn't look as bad as it did in the 3d model so i'll do that.

As I suggested 😉.

Are you going to do a back to back test on the dyno with it?

 

[mrluke]

Nice progress mrluke 🆙! Are you satisfied with the surface roughness of the bell mouths? How do they align with the runners? I can't see it clearly in the picture.

As I suggested 😉.

Are you going to do a back to back test on the dyno with it?

I think you said it wouldn't fit

Surface roughness is actually slightly smoother than the aluminium in the runners. The phone flash isn't very complimentary to it on the close up but its actually pretty good.

They align well with the runners, if you look carefully at the bottom of the far right bellmouth there is a little bit of lip showing but that could be resolved by moving them slightly and re-tightening.

There will be a back to back dyno run but mostly i'd like to get them fitted so I can start a longevity / reliability test. If that goes well i've got a few different options i'd like to run on the dyno.

I also need to make/fit the brass inserts before these are permanently mounted....still awaiting delivery of brass tube.

Next major step is getting the rest of the manifold body scanned and modelled

 

[drtye]

This is amazing. Bravo to you sir.

 

[LotusElise]

Surface roughness is actually slightly smoother than the aluminium in the runners...They align well with the runners, if you look carefully at the bottom of the far right bellmouth there is a little bit of lip showing but that could be resolved by moving them slightly and re-tightening.

Sounds good. For the first approach of it fits very well. My pencil shadow draw technique with a paper and the head to get a better blue print basis for creating a intake manifold flange needed 2 subsequent laser cut outs of a 1 mm alu sheet to get it aligned finally for the CNC flange.

This picture shows the 1st CNC flange attempt and the alignment. The flange CNC cut quality was awfully as you can see. The double sided cut direction was not aligning, there was an offset of 1.2 mm and the surface smoothness was draft level only. A 760 Euro failure working with the wrong people. If the 3D plastic would hold higher temperatures of around up to 180 °C without any change of dimensions and shape than it would be more interesting for IM fabing.

There will be a back to back dyno run but mostly i'd like to get them fitted so I can start a longevity / reliability test. If that goes well i've got a few different options i'd like to run on the dyno.

Great 🆙, I am looking forward to it.

Next major step is getting the rest of the manifold body scanned and modelled

I stay tunned 🆙.

 

[drtye]

Would this fit the bill?
Ultrasint PA6 FR (Flame Retardant) 3D Printing Material
Looks like it's melting point is 201C and flame retardant. Limited by printer bed size.

 

[mrluke]

There must have been a lot of work in getting your inlet manifold made up!

The benefit of the nylon part is that if needs be it could be sanded fairly easily to improve the port match, it might even be worth making the ID slightly too small so that they could be hand finished.

For comparison the actual print cost for the trumpets is under £50.

I'm not sure if this nylon is going to be the final material, waiting to see how it deals with the temp. However I have a fallback option of Nylon 12 CF which can be heated to 143c under 18bar load before it deforms by 0.25mm. Which I am more confident would be up to the task. Failing that there are things like Ultem.

Even the plain nylon can hold 4.5bar at 150c so we're certainly in the ballpark of possibility.

Details on the Heat Deflection Test:
Heat Deflection Temperature: Definition & Values at 1.8 Mpa (264 psi)

 

[LotusElise]

Would this fit the bill?
Ultrasint PA6 FR (Flame Retardant) 3D Printing Material
Looks like it's melting point is 201C and flame retardant. Limited by printer bed size.

Wow, you are up early and well informed. Thanks for the link. I skimmed it, many properties of it looks promising. My feeling says I would still need notched brass inserts to enforce the bolt bores to spread the blot forces far wider into the material. I am not sure about this.

There must have been a lot of work in getting your inlet manifold made up!

It took some effort, yes. Costs for my prototype was around 2000 Euro only for fabrication and material, a bit expensive, but worth the results. Made already 180 [email protected] rpm (or 180 [email protected] rpm at the wheels), not bad for a 2 Liter NA engine shortly after VTEC.

For comparison the actual print cost for the trumpets is under £50.

That's another world, the same of alu would be under 50 GBP when producing as cast type. Sounds very good!

The benefit of the nylon part is that if needs be it could be sanded fairly easily to improve the port match, it might even be worth making the ID slightly too small so that they could be hand finished.

So it doesn't smear when it get sanded?

Details on the Heat Deflection Test: Heat Deflection Temperature: Definition & Values at 1.8 Mpa (264 psi)

Wow, thanks for the link. It seems it may worth a deep dive into it for the next IM, which is planned for raced 87x99 NA engines.

Thanks for the inspiring links guys!

 

[mrluke]

Wow, you are up early and well informed. Thanks for the link. I skimmed it, many properties of it looks promising. My feeling says I would still need notched brass inserts to enforce the bolt bores to spread the blot forces far wider into the material. I am not sure about this.

That's my next step when my brass tubes arrive. The Brass tube will be cut to match the thickness/depth of the flange then you use a flanged bolt to tighten. This means that the torque is transmitted by the brass tube from the bolt head through to the underlying metal fixing point. The plastic is then held in place by the bolt flange.

This is pretty standard in many OEM plastic parts, however they dont seem to be available in quantities <1,000s so i'm resorting to making my own. I imagine as this sort of printing becomes more common you will be able to buy "compression limiters" in much smaller numbers, like you can with threaded inserts.