Gen 1 RX7 into tarmac rally Car - Group C Replica
 

Well,

have been talking to Elliot from Turblown recently about turbo selection (more later) and have enjoyed reading all the info in the single turbo section so I thought I would share what I was working on. Below is a condensed version of the build thread I have going on an australian forum. After having a crack at tarmac rally here in Australia in an Evo VI TME I was ready for a change and I decided I couldn't afford a lambo or a 35GTR to play with the big boys, so the obvious choice was to join the has beens in classic. :) The easy (but expensive) option would be to get an old expensive VW (Porsche) and campaign that, as the rear drive rear engine is as close as you could get to AWD and a great advantage when it inevitably gets wet, but cost and the want to beat said person in expensive VW was a motivating factor to try something else. Started out my racing in the suburban backstreets in an RX3 coupe back in the day (wish i had kept it) so had a soft spot for a rotor.

The smart choice in the rotary offering (pre 1985) would have been an FC with the independent rear, abs??, etc etc, but I just couldn't get excited about building one. (No offense to FC owners...) But being an older guy, I remember the moffat cars well, and thought a flared and winged moffat car with some modern tech thrown at it would be a good thing.....at worst it would be a laugh and paint some lines.

As live axles were very foreign to me (Evo/STI background) I looked into doing an IRS conversion into a Gen 1. Possibly an MX5 or other japper subframe and cut and shut. But finally decided it might have been an engineering challenge too far, and encouraged by the times the Impropved Production racers do with live axles, and the fact that the old V8 supercars and nascars make em work ok, I went down that path. Not sure how it will go on the lumps and bumps of tarmac rally though....some seem to make em work....

So essentially, it should finish up as a series 3 shell, full moffat group c body kit, 13B REW engine running a single, FC front subframe graft to get rid of the reciprocating ball steering and update the front suspension, full equal length and adjustable 4 link rear with turrets fabricated into the shell and coilovers mounted over the diff and an adjustable watts linkage. Hoping for sub 1000kg, and 400hp ish at the wheels.

So where have we got to......

Start with one very straight relatively rust free series 3 shell.

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Then strip the beejeesus out of it...

Then the unenviable task of stripping out the sound deadener by hand with dry ice.....man these things have a shite load of it. Way more than the evo...must be a bit loud eh?

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Then it was time to get the FC front subrame in. This is where I started to use the services of a local race fabrication company called Racing Dynamics. Couple of passionate young fellas with more than a few clues. Much respect to those on these forums that do the whole build. I want this to be decent and am not even a fabricators anus. Cocky shit welding just wont cut it. With the subframe, I am not the first person to do this graft so I wasn't in completely new territory. I stripped out the old one and pinned the new one in place. We reused the front mount bolts as they line up quite well, and at the rear had a CNC machined stud with spacer machined up that goes right through the chassis rail and is welded top and bottom, with the right spacer on it and a threaded stud so it bolts straight up. Also did a spot of seam welding. I have sourced an MR2 spyder electric hydraulic power steer pump with built in reservoir which I plan to use to run the powered rack. Sheds a bit of weight, removes a power sapping pump, and allows the weight to be placed lower down. Popular choice for hydrid projects and SAE racecars.

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The rear end was where the main fabrication was. I got a Race Products floater kit and adapted a hilux diff for it. It is both camber and toe adjustable (changeable shim plates) and should be bullet proof. Bit of a weight penalty but I am currently chasing an ali diff carrier (paging Momus :) ) which should largely negate that. The kit I am running is similar to the one below but has a 2 piece floating brake disk as opposed to the one piece.

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So then we had to sort the equal length 4 link and shock towers. Shit was getting serious. Lots of metal cutout. We started with a McDonald Bros cro mo 4 link, but as it is drag racing based, I found the chassis and diff brackets were longer than I would like/need and spaced the upper and lower trailing arms too far apart. So I had a mate do some on CAD and we made them a bit smaller. The ability to just draw things on a computer, email them to a laser cutting mob, and pick them up days later amazes me.

Shock towers in and upper links boxed out.

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Had MSF Racing Components make me an in car adjustable watts linkage. It uses a crank handle inside the car to adjust the rocker. Not really adjustable on the fly unless I get my nav (wife) to crawl through the cage and crank the handle mid stage, but will save grovelling around under the car between stages and allow quick tweaks to the rear roll centre. Very nice bit of kit.

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Once that was sorted it was time to tie it all in with the cage. I got a T45 (cro mo) cage from the UK from Custom Cages. (Never again) I did one in the past for the evo and it worked very well. I imagine they sell a lot more of them for the evo and it is fine tuned over the years. I dont think they do too many gen 1 cages so it wasnt the best fit out of the box so took some work from my installer. But we got a good result in the end and it will well and truly do its job if required and will be a CAMS certified cage. Still a few more bars to add. Will do a harness bar once the seats are test fitted and also brace diagonally off the strut towers to the dash bar once the engine is test fitted. (is already a tower to tower cage)

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From there it is on the rotisserie to finish off the welding underneath the 4 link, strip off all sound deadener, cut off all redundant brackets etc etc. And that is where we are up to now. Gotta love wire wheeling off all the tar shite off the bottom. Found some degreaser and a pressure cleaner finished it off OK.

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Meanwhile, John Otter (Otter Engines...local old skool rotary guru) is in the final stages of building me a dowelled 13BREW very mild extend port, new housings ect etc with Rohan (Xtreme Rotaries Vic) fully balancing the rotating assembly. Plan is to shoot for epic response and midrange (not typically a rotary trait) and try to get around 400hp atw. The Borg Warner EFR 7670 turbo (1.05 twin scroll hot side) I have had on order for about 8 months is due to ship any week. Plan is to fit it on a custom short runner twin gate manifold. Also have an old EVO 9 intercooler and a new FC dual pass Koyo radiator. Plan will be to do a V mount style setup. Evo cooler is extremely light for what it is and should flow enough and provide very short pipe runs......and the price was right.

Have got a series 5 turbo gearbag with new OS Giken 1-5 close ratio gearset through it ready to go. Team that up with 4.8 diff gears and an eaton trutrak and we should be good to paint some lines. Thats pretty much the drivetrain sorted.

ECU wise i have an M800 sitting on the shelf with and M and W CDI to provide ignition. Plan to do a MoTeC dash and PDM with a custom wiring loom to shed weight and make an old car electrically reliable. Basically been bargain hunting on line for the last year or so accumulating new and secondhand parts here and there and drip feeding the money out. Has made the cost a little more manageable.

So thats about all I have at this point. Still a long way to go. Pushing at the moment to get the running gear back under it (off getting powder coated) and then test fit seats, pedal box etc and get the shell off for paint. Hoping it might be driveable later in the year.

For those not familiar with the Allan Moffat cars, this is what I am looking to replicate, but with modern tech thrown at it.

https://farm5.staticflickr.com/4064/...c17_z.jpg?zz=1

A little bit more of an update.

Got the front subframe back together. Stripped it and sent it out to the coaters to have it done the same colour as the rear diff. While it is a race car I still want it to look the part.... all the gear no idea....thats how I like to roll. :) While that was getting done the guys at Racing Dynamics gave me a crash course in using an oxy and I got stuk in to burning the tired factory bushes off the control arms. Once sorted I dropped them round to High speed engineering to blast them to bring them back from the dead, gave em a coat of clear and then fitted new whiteline bushes. Also fitted some bump steer adjustable tie rod ends to fine tune it all once complete.

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Meanwhile I managed to snag a drop tank that had been made for the Stubber genuine Moffat car. As it is a period racecar I think there might have been an issue with the new tank being legal so i picked it up for a sensible price. It was partitioned in the middle to be half tank and half fuel pump setup. Given I will need about 80 plus litres to get through queenstown and arrowsmith, we perforated the partition to make it a baffle and got the capacity up to about 110 litres. Brad Stacey took care of putting a sump in the bottom and running the return line to it to act as a kind of in built surge tank. Will also run an external surge. With a little bit of sheet metal work around it, its a pretty good fit.

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The diff went off for straightening after all the bracketry was welded on (final drive) and it had moved around quite a bit. Important to get the flanges at the end true to ensure you actual get the camber an toe intended by the shims. Its now all back under the car.

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Meanwhile, John Otter has completed the build of the rotang. Is a bit of a mix of parts. Series 6 plates, new series 5 housings, series 8 rotors and shaft, series 6 intake manifold extrude honed and match ported. Went for a quartermaster 5.5" twin plate clutch and a billet flywheel lighter than some of my poohs. Terry Stacey took care of some very mild porting, (focussing on torque and response) dowelling, oil mod to eccentric shaft etc etc. to make sure it was a good thing. Also sent the entire rotating assembly including clutch and flywheel off to Rohan at xtreme rotaries to have it balanced and the shaft isotropically treated. You get a before and after balance sheet. The reduction in forces on the rotating assembly is astounding. Cant be a bad thing. Hoping it will be happy at 20psi boost on E85.

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So the mission now is for the Racing Dynamics guys to fabricate some cro mo engine and gearbox mounts and get stuck into the cockpit and mount seats, steering wheel, pedal box, handbrake etc. (Tom, if you are reading this get off the internet and back to work. :) )

Got stuck into the dash recently with a bit of help from Jarrad at RD and got the one piece moulded fiberglass dash top in place. The factory ones are typically cracked and are heavy. Also all the vents are redundant as I will be running a heated screen so good chance to block them off and smooth it all up. Will send this off to be flocked once final fitment is sorted. Plan is to reinstate the glovebox and centre console down to the gear shift and flock it all black with carbon centre console insert. Like my cars to look properly finished and not too hacked up.

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Also got stuck into gutting the doors. Coupe doors are heavy!!!! Guesstimate is about 30kg before I started. (standing on the bathroom scales holding it) :) Down to about 14kg by the time I finished. Basically they are completely gutted save the door opener and locking mechanisms. Plan is to fit lexan windows that are manually lifted up and down with straps to secure them in the up position as I have seen done in some Porsche's. Managed to get some carbon door skins. Have made my own in the past but with the cost of material these worked out really well priced and saved me the ballache.

Before
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After
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I also got stuck into fitting some of the new body panels today. I have fiberglass front guards, bonnet and front bar, along with the front and rear flares and the rear wing. Keen to get the body completely assembled so when the cockpit is fitted out we can strip it and send it out for paint. Great to see it starting to look like a car again. Going to be a fair bit of arsing around trying to get panel gaps and fitment of the panels right as the glass does seem to move around a bit and change shape a bit more than metal panels. But they are solid once you nip up all the fixings.

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Thats about all for now, but hopefully there shouldn't be any more major delays and we should be able to keep making steady progress.

Got a little more progress. Found some time yesterday to get out there and hit all of the interior with a wire wheel to get it spotless ready for paint. Mainly just getting rid of the last traces of sound deadener. Now just needs a good wipe with prepsol. Trying to make the painters job as easy as possible to improve the chances of a good result.

http://img.photobucket.com/albums/v9...d/Interior.jpg

While this was going on, Tom fabbed up some cro mo solid engine mounts and got the engine in place and a nolathane gearbox mount. The engine is completely behind the front axle line and as low as we could risk going without exposing the sump too much. Can be packed up higher if required. Will probably still install some sacrificial buffers just in case it gets some air and compresses on the crown of the road which might result in contact. Will have a better feel when it is at its final ride height. Plenty of room in front of the engine for the V mount setup. Should have epically short pipe runs on the intercooler.

http://img.photobucket.com/albums/v9...gineMount1.jpg

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http://img.photobucket.com/albums/v9...d/Enginein.jpg

So from here its start fitting out the engine bay with radiator, intercooler, oil cooler, power steering cooler, elec water pump and elec power steer pump. Also now we have a gear shift position and know how much room is in the tunnel, we can work on the cockpit.

Still a long way to go............

So my search for a turbo is over. I had my heart set on the BW EFR 7670 and had been on the waiting list for 10 months or more. Hadn't been a problem up until now, but I am now hoping we are getting close to where we will be starting to dummy up the engine bay. Given they still cant enlighten me on a delivery date it was time to consider alternatives. Suffered a little bit of analysis paralysis as I worked through the multitude of options out there with all vendors spruiking the benefits of their huffer over others. I ended up settling on a TDX61R turbo by Turblown. I am sure you are familiar with it. Basically it is a Garrett GTX35 derivative. Details are in the link below. It was a turbo I had been keeping an eye on and waiting on results. Elliot has been a great help. He has now fitted a few and the results seem to be good. A recent FD with stock ports made 480 odd horsepowers with about 390 odd ft lb of torques on E85 at 22psi. So comfortable it will hit my target of 400 odd at about 20psi on the corn juice and not be getting pushed outside of its efficiency. (The Borg was going to be stretched a little.) Also is making 19 psi boost by 3400 rpm. (boost plot below) So all in all it should make good power from about 3400 - 8000 rpm. Should be a pretty decent power band to exploit with the close ratio box. :)

Is a T4 twin scroll hot side so will be setting it up on a dual gated short runner steam pipe manifold to get maximum response. Is a bit of a relief having the decision made. Was tired of getting fooked around by Full Race. Hopefully it turns out to be a good thing.

Turblown TDX61R - Turblown Engineering


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Awesome build bro. I am doing a similar build trying to get a group C kit and doing front fc subframe and a ford 8.8 rear. Love all of the fab work i wish mine looked that good =D.

well fellow rally rx7 person. you have offically made my rally car seem like crap! Granted its circa 1988, but still. utter crap.

So we have the 8" toyota here in the states, but i would love to know what those hub like purlple axle things are and where you got them!

Basically you have a more advanced version of my gravel car. I ran the subframe as well. Went with a miata 1.6 motor which im taking out for an Rx-8 engine. how much of a spacer did you run? I have a 1/2" curious about maybe 3/4" Im still mucking about wiht the stock rear geometry, but im basically going to replicate the Ford Escort MkII prep manual for the rear, and run a panhard.

US rules are pretty much a living nightmare to get a fuel cell into the car legally... Also, i dont think we can run T45.

you may have also inspired me to make my Rx7 rally car 3.0 to replace the death trap cage i have now.

I want that big wang!

Thanks for the feedback.

The rear axle setup is from a company called race products here in Australia. This system is based off the rear end that was in our national V8 race series. (V8 Supercars) They have this year just gone from live axle to a transaxle system. The system is a bit like a CV joint on the end of the axle allowing the end to be articulated while still sending through drive.

I think you would find similar live axle kits in the US based around Nascar. I know of a guy who imported a nascar rear end and it was very trick. Hollow lightweight axles for memory and camber adjustable etc etc.

Race Products | World Class Motorsport Engineering

Re the front spacer, I will have to check. We kind of bolted up the front and observed where the rear seemed to want to settle and worked to that. I will run a tape over it for you.

Re the rear, I definitely took some inspiration from the escort rally guide. Some good ideas in that setup that are well proven. Panhard is definitely easier and cheaper than a watts.

Nice attention to detail. I just put the final touches on your turbo, and I did get some black waste-gates on rush here. I will ship the second they arrive!

:egrin: Loving it, keep up the good work!

Looking good man, quality build.

Cheers for that.

So we have made a little more progress.

Working on getting the cockpit together. There are definitely some packaging constraints in the RX7 for someone 6"2" ish in height and long in the leg. This has been further complicated by a kit cage that didn't quite go as tight against the roof as I would like. Fortunately my head is basically in the open area of the roof cross.

Has been a fair bit of panel work to the floor on the drivers side. A chunk has been taken out of the trans tunnel to get me in the middle as much as possible, and a hump taken out of the floor to get as low down as possible. We have also mounted the rails under the floor and made them flush with the floor height to again get as low as possible.

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The passenger side was a bit easier. Missus isnt super tall so was just got as low and as far back as possible without going over the top.

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Had planned to use a 600 series floor mounted box but have some packaging constraints with leg length so have punted that off and gone for a hung unit. Should buy us a bit more space and to be honest should allow the pedal to be lower down and have a more natural action to them. Think this will make it a better package overall.

The turbs has arrived. Thanks Elliot!!! As mentioned, its a TDX61R from Turblown. Basically based on the Garrett GTX35. Is a ball bearing unit with a 1.0 twin scroll hotside with a P trim wheel in it, along with a custom billet twin blade compressor wheel with a T04s front cover. Has been dyno proven to make approx 20psi by 3400-3500 and deliver 450+ hp atw. Hoping it will be a good package.

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Plan is to team this up with a fully divided, short runner, twin gate manifold. Example below. We will be going steam pipe to minimise any risk of cracking. Looking to maximise the response of the turbo. This is getting dummied up as we speak.

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The V mount setup has been dropped into place. Very happy with the way this is taking shape. Will lift out of the car as one unit for easy servicing. The pipe runs for the cooler should be epically short. Again looking to maximise response.

http://img.photobucket.com/albums/v9...mountfront.jpg

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Cage is now CAMS certified so that is a relief. Always a risk of revisions coming out to the design and getting caught with a non compliant cage.

On the wheel front , I have been getting templates from the US for the wheel. Forgeline GW3R forged 3 piece wheel. They can do custom offset. Has been a bit of back and forth getting PDF templates sent emailed out, printing them off to scale and gluing them to cardboard and cutting them out as a test fit. Is a nice way to be confident on fitment though before lashing out. No issues with caliper clearance, just getting the offset right now. Hoping to have them in the pipeline in a week.

http://www.forgeline.com/product_ima..._image-488.jpg

Still a long way to go but making steady progress in the right direction.

nice build. is that an evo iv intercooler?

Evo IX inter cooler. Bit more capacity than the early ones. Nice and light. Should flow what we need and very efficient. Handy that the inlet and outlet rake back in the right direction.

wow, sorry, that's what i meant (ix = 9). haven't done roman numerals in forever. if you ever get the chance, can you take pics of the radiator/intercooler brackets please? i'm assuming it's tied to the frame rail, right? thanks.

That you are sir, nice work!

The wheel choice appears both functional and beautiful, should fit the car very well. The V-mount setup looks awesome as well - hope that all works out for you how you want! Good luck with the continuing work on the build :bigthumb:

Thanks for all the positive feedback.

Got a little more done. The manifold has been fabbed up for the turbo. The brief was to be fully divided, short runners, gentle bends. Hats off to the guys at Racing Dynamics. They listened for once :) and nailed it. Just have to place the twin gates. Hoping between this manifold with the TDX61R on it and the short cooler piping we should achieve a really responsive setup. Will get the manifold and the hot side of the turbo coated once it is all sorted.

http://img.photobucket.com/albums/v9...dcd4653a19.jpg

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Have also finally got the wheels on order. Forgeline (Harrop) have been great to deal with and done me a great deal on 4 wheels with the titanium hardware. Thought it might be best just to get the 4 to start with and recover from the financial shock before getting to the 6-8 rims required for the longer rallies. I think these puppies will really set the car off.

http://www.forgeline.com/product_ima..._image-488.jpg

Those wheels will great on the car! Really liking the fab work you did for your driver seat, got any more pics of the floor pan?

very nice indeed. some quality craftsmanship gone into this project.

any updates?

Lovin' it. I've used Forgeline wheels before and plan to in the future. They make a very nice wheel. More importantly they will work with you and they're prompt about getting them done to spec and out to the customer quickly. You are giving me even more ideas, damn you. :lol:

Thanks for the positive feedback. Bit more progress with the car. The cockpit has been completed, tested and stripped out. The hung pedal box was a much better solution and gives me some more leg room and leaves the floor more uncluttered. Overall its gone from feeling a little cramped and awkward to a good space. Really important in this type of car IMHO. Hats off to the guys at Racing Dynamics for a few innovations to help with this.

A couple of bars have been added. Apparently this chassis is prone for flexing along the A pillar. I had seen other cages brace back diagonally and was keen to do the same. So we added those in. Also tied it back to the fire wall internally for added strength. Have also got some roll cage tube joints. Bit like these guys I.D. Tube Clamp Plan is to use these for the strut tower brace. Always thought the off the shelf strut tower braces that weren't rigid and had hinged joints at each end were a bit of a waste of time. This setup should be nice and solid and triangulate the front.

Basically we are doing the last of the body prep and then its off for paint and signage. Should start to look like something once painted. That should clear the path to basically start bolting things on to the car and leaving them there rather than having to strip everything off for paint. We are confident the work remaining now can be done on a painted car without any dramas...just a little more care.

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Wow, just wow. Very impressive. I would love to have to funds and resources to come close to this type of build. I'm impressed with your choice of engine parts combination. I too have tried to keep my powerband from 3500 rpms to 7500 rpms. Feels great being able to hit full boost by 3500 :D