Lucas' 1991 Mazda Eunos Roadster

[Themi]

47 minutes ago, Roman said:

Does this head have a different valve angle, or port shape or whatever? 

And to answer this, yes (compared to a b6). The port is quite a bit steeper, and larger cross sectional area. The valve angle is steeper (valve face is closer to parallel with the deck) and the intake port has less bowl, "straight shot" from intake manifold to valve.

From what I've read, this design results in higher air velocity and more swirl in the combustion chamber resulting in higher efficiency from a complete burn. Contrast that to the bowl or "high approach" where you get more complete use of the perimeter of the valve,

This is pulled from https://www.austincc.edu/wkibbe/headdesign.htm

[Roman]

Steeper port with a less shitty short side radius will earn its keep. 

A lot of modern performance engines have quite a narrow valve angle, to get the combustion chamber volume down for higher CR without all of the grossness associated with having a big crown on the piston.

Get the VVT and runner length working nicely and you'll have a solid 1600 setup! 

[Themi]

A steady drive on totally private roads, for posterity. The tune still reeeeally needs a professional, it has a few big flat spots.

https://drive.google.com/file/d/1Uy84HwzMM1ADAAT59gE432VnYk1q4Xfe/view?usp=share_link

I also think the banjo bolt for VVT is rubbing on the bonnet, hence the flat spot and flaked paint... Oh well, holesaws make for pleb shaker hoods!

[Roman]

2 hours ago, Themi said:

 

 

Heaps of people think that porting is about just smoothing out intake side of the valve. 
But if you look at how theres like a 45 degree cut around the valve, if you blend that into a radius then you can get some good flow gains. 
Like you might not see gains from doing that when the valve is at full lift, but if you can improve low lift flow then it's like stretching out the duration of the cam for "free".
But depends on how willing or brave you are to mod the combustion chamber (wouldnt reccomend it unless you at least have a spare, and some valves to grind down to protect the seats)

[Themi]

I've done a bit of bootleg porting with the air die grinder, but havent looked in to this. I know what you mean about the radius, I'll look in to it for the next iteration of the motor. I need to go pick up a spare longblock that has been at a friends house for far far too long, and will grab another head. This head pictured was my "spare" but the engine it came from was well and truly dead. Over 280kkms on the clock and there was damage to the head gasket in multiple places. I wouldn't run this one.

I do need to pick up another head plus intake manifold to look at ways of re-manufacturing my intake manifold, I have ideas on how to modify one.

I was playing around in fusion with better port transitions, straight shot etc. I need to look at how they angle the injector from factory, and how they deal with the separation between injector and the rest of the runner. I would put money on that transition being a big player for airflow.

[Roman]

I reckon you'll see some sweet gains by straightening that intake up to port direction! 

[Themi]

Is the entire assembly on the piss? Why yes, yes it is. My rx580 reeeally has a hard time with this many faces. For fun I loaded a low poly version of the cylinder head into fusion, just to see how it would look. Also there is a mesh of some 4age silvertop ITB's in there, and some short trumpets I modeled a few years ago. Attempting to rotate the entire assembly just causes crashes, so I left it as is.

Currently the flange on the car turns sharply downwards right after the port, and the throttles are actually below parallel with the deck of the engine.

I have more work to do, but it is cool to see the thing come together in fusion! It is really interesting reading up more on runner length, shape, cross sectional area etc. It looks like many of the things I wanted to model have already been done on test benches, so perhaps it is just the case of trying a few things out?

[Themi]

So I don't have a 3d printer but I diiid borrow an AC Tig welder, so I'm "here we go again"'ing it and going to make my replacement intake out of aluminium, just without the gross bend.

Here you can see how even the stock runners "flared" where they were joined to the old intake. The cross sectional area increases quite significantly here, which is bad mmkay.

Next, a little illustration of where my old manifold was cut and shut. 

Now here's me using a totally normal and not at all weird method to hacksaw through this manifold. I hate hacksaws but my angle grinder was hating this more.

And lastly, the chopped manifold.

I intend on cleaning those holes up with the angle grinder flush to the flange, and then using the die grinder to cut out the rest of the tube from inside that hole. I think from factory it is basically glued in? 

Im going to make a flange for the 4age ITBs to come straight off this flange at the same angle as the ports, just barely clearing (or even mildly touching) the fuel rail.

Anywho, hopefully the aluminium tube and plate will arrive this week so I can weld up the runners properly!

[Themi]

Itb manifold part deuce:

New runners are 95mm long 2" OD aluminium tube with 3mm wall thickness. I'm using 10mm thick aluminium plate as the flange, which will be trimmed to size later.

I made a real effort to get the angle just right to match the port angle. Looking down the trumpet at WOT you will be able to see the top of the piston! I can't shorten the runners as them parts of the fuel rail interfere with the throttles.

The comparison between the old manifold and new one is quite stark.

Also, I'm not so sure if the new one will clear the bonnet... But the main issue is the TPS now will interfere with the clutch res.

Anyway, I haven't welded everything together as I have quite a bit of prep and tube "massaging" to make everything fit. Still I'm happy with this progress.

[Roman]

Shit yeah, looks great! 
 

[Themi]

I've been busy with a major milestone at uni, which I have (un)officially completed as of Friday so I could spend the long weekend carrying on with this.

I've tacked together the intake manifold. need to get some roloc pads from blackwoods to do proper surface prep before continuing as the tacks are pretty dodgy to say the least.

The ZL casting is far worse than the old 4age flange I had on the old manifold, this is full of crud and loves to pop and splatter, however once new material is infused into the casting it doesn't do too badly.

As I was hoping for, it clears the fuel rail, brake/clutch things and bonnet. Perfect. One day I'll get around to making a plenum for it, but for now it'll remain open to atmosphere.

[Themi]

Lights out and away we go, the new manifold is on.

I had to flip my brake booster to clear the trumpets, painted it again at the same time to tidy it up.

Also I had 10,000 vacuum leaks. Turns out my aluminium welds are just as shit as ever, thick casting doesn't help my problems. Eventually I noticed that one little bump on a weld was touching injector #3, stopping a good seal at the base of the injector.

Rectifying the air leaks and solving fuel hose routing, plus a few other things done.

Now the car is back to running and driving but still always more to do! Wof is expired so I'm needing to tidy up some of the gremlins that have appeared before taking it back in.

Video of dorts here

[Themi]

Alright air filter time.

Bare trumpets are cool, but every bit of roadworks or loose surface scares the shit out of me. I don't have an engine undertray so rocks are a very real concern!

Some cheap filter socks came up which fit great. I don't mind the look, but they are very restrictive for airflow. A friend had an ITB'd BP on the Dyno and gained 10kW removing his socks, so they aren't excellent for performance.

Some may have seen that I used to have a pipercross px600 box air filter, which I had modified to clear the clutch slave in my old setup.

Well I wanted to un-modify the backing plate to save money, and possibly eventually replace the box filter with an unmolested one.

I welded a new plate on where I cut earlier, then ground it flat and cut the shape up.

Now I have to replace the box filter but we have option number 3: a badass box filter setup. My trumpets don't fit under this filter and the filter is a bit hacked up at the back, however I love the look.

Soo yeah, filters are cool but the box one will prove expensive. I'm not sure what option I'll settle with but if anyone has any thoughts (or a cheep box 80mm or domed 120mm px600 filter) let me know!

[jakesae101]

If you wanna sell that box filter let me know as im running shorter trumpets

[Themi]

5 minutes ago, jakesae101 said:

If you wanna sell that box filter let me know as im running shorter trumpets

Are you at all concerned with the "modified" section at the back? Lol

[jakesae101]

Should be ok ill just measure the length 

[Themi]

The suggestion given to me last wof was to tidy the front bumper mount and tow hook points. I did that, plus tidied the front sills and most of the engine bay. Its amazing how much the engine looks more at home in a halfway tidy engine bay!

I'm also reassembling the interior and tidying up the guards and front bumper a bit before final reassembly. Should be able to take it for a shakedown soon to see how the intake behaves, then hopefully wof this week. Meet in Tauranga next weekend so I'm hoping for a pass first try...

(Broke a lamp...)

[Themi]

Alright Friday night shenanigans.

Im making the drive to Tauranga on Sunday and it's time to remove the drone and rasp from my exhaust. Previously I had the absolute cheapest stainless resonator I could find but I splurged for a Vibrant Ultra Quiet 2.5" resonator to replace that.

I ordered it late last night, arrived today and I was very happy (jump scare face reveal included). 

And yeah. The money shot:

Some late night welding:

And the old resonator:

New one welded on:

 

And the end result... Well it's not ultra quiet, but it has none of the old farty rasp that my exhaust used to have. Finally an NA setup that doesn't sound like trash! I really like the new sound. Growl and bite but no bark. Ready for a good weekend!

Oh and I got a wof, with a few minor suggestions...

[87creepin]

Need video demonstrating better sounding zorst pls 

[Themi]

I'll get to the "current" exhaust video one day - however these are before videos of the old setup (bad intake, shit resonator) at a motorkhana held by SCCNZ in march.

Not the tidiest

I don't think this course was meant to have a loop

Cue excuses: no handbrake, no power steering, no abs, bad driver

 

The reason I have few/no "current" videos is that I have this annoying "chirp" at mid throttle: it sounds like the intakes are whistling? I believe I need to take my intake off and really smooth down all intake surfaces so there are no lips/edges for air to flow over and make noise, because it is super frustrating to drive like that. It also makes cruising super frustrating because most gentle inclines cause the chirping noise again.

I'm also going to get a new rear muffler, I think my current one is fine but I want something that reduces the total exhaust volume significantly, as it is a bit loud at motorway speeds, reducing the top-down comfort I'm expecting to need this summer.

Gratuitous overrun on the way to a meet in Tauranga.