Zac's 1998 RX7

[ProZac]

Whoa, those baby-things take up ALOT of time!

I've managed to get the odd bit done on this though.

To cure the oil leakage issues that FD's commonly suffer from, a sump brace is purportedly the way to go. They're available to buy, but I thought it'd be fun to give making one a go. I ordered a sump flange gasket, with much tracing and scanning later I had the pattern cad'd up, and could cut up a blank on the waterjet at work. We had some 1/4" 316 stainless plate at work, and I figured that would be good to use. Wont go rusty, and it pretty damn stiff. Kind of heavy, but most of it gets cut away anyway...

[ProZac]

Whoops, not too sure how that actually got posted. There were pictures to go with it and everything, but then there was pizza, and wine. Hmmmm wine...

 

To be continued.

[NickJ]

Wait what, you guys have a waterjet out there?

[yoeddynz]

12 hours ago, ProZac said:

Whoa, those baby-things take up ALOT of time!

Yep- I know those issues. We have a cat.

 

Glad for updates. I was thinking about this car the other day and wondering how it was progressing.

[ProZac]

Right, to get back to where I was lastnight before I was called away for Pizza and Wine (oh, gosh, what a chore my life is....)

Babies. Go have one. Now, honest, totes legit an awesome time :-). There are shit parts, but wow, overall its actually pretty awesome.

Work has been really busy, surprise surprise. I did _a lot_ of this:

In order to get the car we've just finished building going:

And go it does. The new track at work has been sealed, its got an (almost) straight that is about 1k long. Listening to this thing bang gears down there is pretty awesome. We've all been promised a drive, but I'll believe that when it actually happens.

Sooo, back to RX7 related things :-).

Because I'm an idiot and could just go the easy way, I gave making (instead of buying) a sump brace a go. Lots of tracing and scanning got me a cad model of what I wanted. I used a table cutter to cut out an outline of what I'd cad'd on paper, to see if I was on the right track. It all matched up to the gasket, so I committed and cut the profile out of 1/4" 316 stainless on the waterjet:

One of the first jobs I had when I got to work was to get the waterjet cutter sorted. Its a Chinese machine, with some terribly translated NCStudio software on the controller PC. With a bit of finesse though, I can hold a pretty decent tolerance on it, around 5 thou or so if I really try. This job didn't require such accuracy though, so I didn't replace the orifice or nozzle or anything, 0.25mm is close enough!

The profile cut out really nicely, and matched the gasket spot on. One thing that bugged me though, and seems to be the same on most of the commercially available sump braces, is that they don't have reliefs cut for the stiffening ridges pressed into the FD sump flange. As you bolt the brace up, it would just squash them flat into the block. With a bit of white paint to outline the ridges, and a few photos, I got the location of the ridges onto my model, and cam'd up some toolpaths for the CNC mill:

Yeah, an example of brilliant fixturing once more, but it worked and didn't chatter... much.

Was my first time machining stainless, with a 3mm end mill none the less. No breakages and actually a really good surface finish. GWizard is my friend. I grabbed some new fastening hardware, as the bolts originally holding the sump on were a bit of a eclectic collection. A coupe of them were actually too long and weren't clamping the sump flange at all, no doubt contributing to the leaky leaky... A thorough cleaning later, tapping out all the holes to remove old sealant and the sump went back on. There was also a broken 6mm tap incident that put a hold on play for a couple of days till I figured out how to get it out... heh. I used grey 3-bond sealant, as it is 100% the best stuff I've ever dealt with. Its one of those products that has a distinctive smell. You know if you ingest of inhale it, its going to be really bad for you, so that means it must do a fantastic job. Honestly though, if you're sealing a sump on, its the only way to go.

So that will be the oil leak from the rear of the sump fixed, woohoo. The engine mounts will now be sitting 1/4" lower then they were (thickness of the sump brace), raising up the motor 1/4"... However, when I took the motor out I wasn't really happy with the condition of the factory mounts. They were 'ok', but could be better. Some googling later, and I discovered that factory replacement mounts are really really bloody expensive! Some more googling of engine mount suppliers, and I found that 1979 - 1997 land rover engine mounts are a similar studded hockey puck design, and almost expactly 6mm shorter than the factory RX7 mounts... Perfect, that'll sit the motor back in its original location :-).

I'll post another update later on with some info on where the intake / sensor system is up to, and the turbos. Cool stuff going on there :-).

Cheers all.

 

[yoeddynz]

Man... you have acess to all the toys. Very jealous.

Please tell us more about the race car!

Oh and your baby ain't as fluffy as our baby so you have it easy.. no fur to clean up etc.

[Dell'orto]

That tread pattern looks eerily like an Eager

[ProZac]

Real Men Smoke Eagers. ;-). It's got slicks on it now though, i think they are just display wheels those ones.

The bossman at work bought the defunct Lotus T125 project, lock, stock and smoking barrel. We built one up that's since gone over to Germany, this is the second built as the original T125's were. Its to be our testing and development car, for us to debug as many of the issues the T125's had as we can (flammability being the major one...).

[ProZac]

Work still continues on this car, albeit in fits and starts. Things have gotten a bit jumbled, but I'll continue showing how the turbo project is turning (pun intended) out, to keep things sort of linear-ish in this thread...

 

I continued to focus on the compressor wheel side of the turbo's first, and cut a couple more test pieces to get the fit to the compressor wheel really dialed in. Finally, I committed to machining the actual compressor housings, and was pretty damn nervous about doing so. I made up a fixture to hold them, which consisted of a piece of 60mm aluminium barstock, with four tapped holes in the end, onto which a plate bolts with countersunk fasteners. This plate has the holes to mount the compressor cover. Everything is made with a bit of slack, as we don't have a 4-jaw available for the CNC lathe, so I got it centered buy just snugging up the bolts holding the compressor cover to the fixture, channeling my inner Abom and bumping it around till it was as dead-nuts true as I could get it. Then I cranked up the mounting fasteners to keep it in that position.

First cuts had a pretty decent butt-pucked factor, but it all worked out swimmingly :-).

I'm going to have to modify the inlet piping to the turbos too to port-match, but I'll do that in the mill, as it'll be much easier to fixture.

I've got around 0.35mm clearance radially between the compressor wheel and the cover, when assembled there isn't any rubbing between the two if you force the shaft one direction or the other, so I'm calling this side of the job good :-). I had to do a bit of noodling and measuring to spin up an adapter ring that pressed into the back of the compressor cover to allow the T25 CHRA to slot in and get the right spacing, but it wasn't too tricky and everything fits together with the original circlip.

 

On to the exhaust side! If I thought the butt-pucker factor was high before, these puppies are HEAVY! I used the came fixturing method as above, but made new plates to mount the turbine housings. Once again quite a bit of measuring and noodling was involved to get it to all fit together, have the T25 CHRA's centered and spaced axially correctly, but once I put everything into CAD it wasn't too hard to figure out.

I used the big-momma boring bar for these, as I needed quite a bit of stick out to have sure the tool turret cleared the housing mounting flange at full cut depth. To be honest, it didnt actually clear, but only by .05mm or so, just left a little witness mark ;-).

Got a little chatter right up the top, but everything fits beaut.

I left a little more clearance on the exhaust side, around 0.6mm radial clearance, as I figure things here get hot, so better to lose a little efficiency, but maintain integrity ;-).

So... Yeah. Turbo mission is getting there. The whole setup actually fits together now, but there are mods to be done to the oil lines, intake piping and water cooling. I need to fit them to the motor to size all this up though, so finishing it off completely will have to wait till later.

Cheers :-).

[LinkDave]

Subbing to Zac's porn.