Gotta love Stewie! Wicked little b'stard with plans for world domination - just like the rest of us =)

Greetings all!

It's with great pleasure (and shallow pockets) that I post my nearly completed FC 20B! Thanks McCarthy for prompting me to pull my proverbial out

I wanna say upfront that although I’m an engineer, I’m not a mechanic. Yes I do a lot of my own work and have a workshop, but I’m into older restorations and rebuilds. With the exception of my own 12a and 13BT, I don’t do much rotary work. Sure I rebuilt my 12a – which I rebuilt again 3 months after as I screwed it up (rofl!) and do maintenance and development work on my 13BT, but I’m big enough to say a high spec 20BT is outside of my comfort zone. So yes I am having it built, but also yes I am designing and redesigning the project as it goes – of course with the help of my local Rotary workshop.

So why do it?
I know it's been done, and done well at that. But it's been a dream on mine since I knew what a 20B was. Even though my first RX7 was a '79 series 1 NA and I seriously didn't know what a 20B was back then, I knew these little beasties were special. Hell, it would be another few years before I knew what a turbo was! I remember fanging my 7 on the standard rubber and dragging everything I could find... And damn it went well!! What can I say? I was barely 20 and that was two decades ago! Since then I've added to the collection and have a nice mix of classic bangers and spinners. But damn I love the power and handling of the turbo RX...

Three years ago I was out in my S3 13BT (a modest ride, non-standard sure, but only 220 horses at the wheels) and I saw something coming up fast when I was heading up a mountain road. I soon found it was a wrx that I thought was standard - eeek, wrong. Held him off for as long as I could, but dammit to hell I was in third at 6kish, and maxed out at 12 pound and he simply drove past me when the road opened up – it was an impressive pass – I didn’t stand a chance. But I was gutted. I'd been up against them in the past and I'd left THEM standing. My pride had been dented, a banger had done my favorite spinner and I had to make good… Victory shall be mine (um, eventually…)

It took 6 months of R&D to discover clearly that getting the power AND torque I wanted out of my 13BT just wasn't going to happen without spending a bomb - and even then there would have to be more than a couple of compromises. So like any power mad (and slightly insane) business owner with a love of cars and bikes, I decided a 20B was the solution. I’m emphasizing the slightly mad here, just so we’re clear.

Firstly, to anyone who may be reading this and thinking of doing the same thing or something similar, stop. Stop and read this forum and your local, talk to people who HAVE done it, or are doing it, so you get an idea of exactly how many headaches you are going to have. Don't get me wrong, it's far from impossible, but it is NOT a straight forward conversion by any means. Frankly, it would have been MUCH cheaper for me to put in a small block v8 with a nice turbo. But although there are people out there who have done just that, I personally believe there is something to be said for keeping an RX with a rotary donk. So seriously, read lots, talk to people lots, and expect to spend money (lots and lots and lots and... You get the picture.)

My starting point was a straight and neat Series 5 (FC) RX7. Bought it from an Ozzie forum member with an engine that was running on one rotor (like I cared), and then found a late serial D series 20B in a Jap front cut. I had to go an FC as a 20B would have to remain NA in my S3 to remain legal here – yeah, right!

The car itself was an NA model, so the drive shaft was weaker than the turbo model and the dif was open. Honestly though, that didn't bother me as the shaft and dif were always going to be replaced. What (2 years later) would turn out to be a pain was that the NA bonnet had no scoop. Did I care for air flow in? Hell no! All the scoop was there for was to try and cool the factory inter-warmer - and look good =). I was more interested in getting heat out, not air in. So no, that didn't bother me. I cared because I'd find that the bonnet didn't close!! My proposed solution is a two fold blessing, modify the bonnet with a reverse scoop that would a) allow the bonnet to close, and b) help get the heat ‘out’ and promote better air flow through the front of the bay – this is in progress currently. Why all this was needed is simple, I decided not to move the engine back as most FC 20B projects do, but rather make space in the standard front for the air, oil and inter cooler, as well as the new cross flow ac condenser and large thermal fan. That's a decision I don't regret btw. I'm happier with keeping the gearbox in the standard position and with the weight distribution of having the 20B 1 rotor forward (noting the heavier diff and rear end I have planned.)

The 20B was removed from the cut and rebuilt from scratch. New everything, including local made unbreakable apex's - they'll bow but won't break (PM me about these if you want more info.) Opened up oil channels, balanced and spaced/ machined rotors and of course the engine has been studded. Btw, thanks to those who suggested I do this rather than simply doweling it. That advice came from this forum and was bang on the money! Can't recall who said it, but he (you) who did, pointed me in the direction of Xtreme Rotaries in Melbourne - and I'm very glad you did. It wasn't cheap (nothing good ever is) and it didn't happen overnight (actually the estimated time frame was tripled - and that was before Rohans accident) but I wanted it done right, the way I wanted it, and not on the cheap.

As you can see by the pics, we're about 80% there. Here’s the summary of works as it stands:

• Engine and mounts are in. Street porting only as I want to maintain low end pull, although I have knowingly sacrificed some high end potential in doing so. It is a street car after all. The engine needs to sit 10mm above the mounts to be legal here. See the pic below. It sure doesn’t look like 10mil, but it is =)

• Turbo is from Billet in South Australia. It’s basically their SB70-GTS with a custom compressor wheel to meet the porting of the engine and my required output. I.e.: I wanted positive displacement on hand at 3000 revs. I’ll it from approx 3100, right up to red line at 8k. Cost me a bomb for the turbo alone, but again, it’s a performance related decision, not a financial one. Btw, I am limiting the engine to 8k for a few reasons. Firstly, I won’t need more. Secondly, I want the engine to last. Thirdly, I wont need more, and lastly, I want the engine to last =) Btw, engine limit isn’t an ignition cut for reason of engine longevity. Will be a Wolf controlled combination of water injection, mixture and timing change, as well as boost drop. My objective is to stop the car being easily loaded past 8. Shift light at 7500 is also planned.

• Water injection is automatic for above 8psi. Mapping yet to be done (as the engine hasn’t been started yet.) Should the water injection run low, I can flip a switch to drop the boost back to 8 till I top it up. Total boost (on 98 pump fuel) is yet to be decided upon. Basically it will be whatever I can get away with without blow by. The turbo is in its efficiency range from 7 pound to 24 – but 24 on a 20B street car is more than a little insane (fun though!) I’ll probably run 16 on the road max, with higher reserved for track days and/ or C16.

• Piping to intake and exhaust manifold are done and custom. Had an aircraft welder do them. Took 8 times longer than estimated, but the result is what’s important to me. It’s not like it’s my only ride.

• Intake manifold has been opened up and flow balanced. I appreciate there is a little discussion as to whether this is beneficial on rotors, but I’ve always found that less resistance and greater capacity for air flow can only be a good thing. On paper, the overall VE attainable should be 86-88%. In practice I’ll be happy with 85.

• Water pump was modified to aid fitting – like where the filler is now? It’s the highest water point =).

• Dump pipe is being done atm (it and the exhaust manifold will be ceramic coated in the next few weeks.)

• The oil cooler is on back-order from PWR. It’s one of the biggest they make – so why is it out of stock??! Anyway…

• 3” Radiator and 5” Intercooler are the biggest I can squeeze in from PWR. Cross flow of course. Love the Intercooler – check out the total height and positioning. Keeping the factory bonnet mount saves clip pins and keeps it looking more factory and less brutal. Also why I’m trying to avoid a bonnet scoop (if possible) currently. If it looks standard, it will lull in victims – okay, I’m a tad insane and admit it I’d hate to be normal =)

• Fuel system was going to be driven by twin Bosch 044’s and a simple surge, but finding a safe AND legal place for the surge tank was proving very difficult. So I opted for twin 500hp rated Walbro internals and a baffled fuel tank. The down side is I loose a little capacity, the up side is it’ll be a little quieter than externals. Fuel lines are being upgraded also, though leaving the returns standard.

• Controlling the show is the Wolf V5. I chose the V5 as support is local and the guys at Wolf EMS have put together a very clever ecu. I’m not saying it’s the best, and never will, but it covers all my needs and allows for my customizations, which are designed for engine longevity and covering the human errors of the dude behind the wheel.

• Brakes, drive shaft and diff are being left standard for the run in period only. However I’m drilling and slotting the front rotors with performance pads as a starting point. Basically (re the brakes), it’s a case of see how it performs. If there’s fade or poor feel, I’ll up the brakes early. Planning to use 6 pot calipers on the standard discs – though looking into other options currently. Suggestions anyone?

• Am keeping air con and power steering, with a new and smaller condenser – which wasn’t easy as there’s only so much room in there. Planning to use the left hand duct area in front of the wheel arch.

• Front air dam is still standard, and the intercooler isn’t the first thing seen at the front (I personally am not a fan of the ‘intercooler with a car attached’ look – but when you have no space =).)

• Box is standard S5 turbo for the time being. May dog it to 3rd gear later. Have a couple of spares, so concerned I am not

• Clutch is a twin plate – see the pics. May change it for a triple when it wears out – it’s a suck it and see moment.

• Running 17x8’s on the front. Currently 225 which sit nicely. Will look at changing this to a road/ track compound if grip is an issue. It’ll never be a daily driver, so tyre wear isn’t an issue for me.

• Rears are 18x9’s with a 22 offset (which is too small I know – should be closer to 30 and up to 35 roughly.) I picked them up cheap on ebay and am using them only as an experiment and are unlikely to remain on the car long term. Not planning to tub the car, but will have coil-overs with the 8.8 translock diff that’s coming. The rubber I’m running was carefully chosen. It’s 245/35/18’s, which will give easily – which is what I want. Remember, this isn’t a drag car and it won’t be seeing track work for a long while. I don’t want to destroy the box in the first week, so I picked rubber that would give easily, so as to not put the box under heavy strain. I also know that 245’s are not enough for a 20BT; it’s an experiment – the result of which will help decide what to run long term.


How much power?

Well, that’s a good question. On paper (and calculated with a VE of 85%) we have approximately the following at the fly:

At 18psi max (As high as I’ll go?) At 22psi max:

4000rpm 228hp @6psi 4000rpm 228hp @6psi
5000rpm 369hp @12psi 5000rpm 369hp @12psi
6000rpm 525hp @17psi 6000rpm 525hp @17psi
7000rpm 632hp @18psi 7000rpm 710hp @22psi
8000rpm 723hp @18psi 8000rpm 811hp @22psi

Looking at those figures you can understand why running at 18psi is too much for the road. Once said, even 14psi still gives a scenery blurring 476hp at 6000rpm. What can I say other than you’ve gotta love a well built 20B!

Test figures are paper based, (and I’ve estimated the boost at 4 and 5k rpm) however there is no reason why they are not approximately achievable. The entire air flow and power build has been designed and built as a single unit – meaning that everything has been built to match everything else from a porting and turbo flow perspective. Once said, I look forward to getting it on the dyno after a good run in period!

So yet to come from the point of these pics is the modified bonnet, dump pipe and oil cooler, engine bay clean up and fuel system and rail. Oh, am running 1700cc Bosch secondary injectors on an Xtreme rail.

If anyone would like to recommend gauge brands, please do. I’m looking at this currently and want something functional and good looking. Hmmmm… Do they come in tall brunets?! Just a thought!

Cheers and enjoy the pics!

 

Additional pics =)

 

And more =)

 

And, um, more

That's all for now folks. have more on my phone, but I've misplaced the transfer cable rofl!

Cheers to all!!

 

Cool dude. I do keep considering putting my 20B in my FC. More room for manifold etc. Then putting my PPort in the FD!

 

looking good mate.

 

Very interesting read. Thanks.

I am also fortunate enough to have a 20B FC. You will not regret it, they are lots of fun. The torque that these motors can produce is fantastic.

You did well by going to Xtreme Rotaries too. Rohan has performed some work on my motor and the quality and worksmanship is second to none! You do get what you pay for, as he is the best.

Good luck and keep us updated.

 

Nice looking project man! The only thing that bothers me about the project is the fan shroud on the radiator. It should be lipped out otherwise you wont be allowing flow from the outer edges of the radiator. and on a 20b cooling is a HUGE issue to tackle. Im still fighting with it on mine.

 

Thanks for all the comments guys, Very much appreciated!!

You're absolutely right bcool! My design sheet showed the shroud flush at the weld points, but 3cm away from the radiator at the point the fan would mount. What it is is bearly 1cm away - which I agree completely is not ideal - and hard to see in the pics. The reason being is the low profile fan I wanted is no longer available. Its replacement is slightly deeper and wouldn't leave enough room between it and the engine pullies. Believe me when I say I was not impressed when it came back like this 'without' my being informed prior. And yes, it cost the fabricator $$ for the error. The other issue is the fabricator was moving shop and (I feel) rushed the completion of the overdue job. However, now that it's been done I'm going to leave it that way for the run in. I can:

1. Add a second fan in front of the radiator - which there is room for (as I always considered putting one there.)
2. Remove the shroud completely and use different fan mounts.
3. Both of the above. Which, knowing me, is exactly what I'd do if there are heat issues.

Funny thing is, my Rotary performace shop feel I'm underestimating the thermal efficiency of the cross flow core. Me, I'm happy to wait and see - but share your concerns. At the end of the day it's an easy job to change it around if need be, so stressing on it I'm not

Hey Pindrop and bcool, do you mind sharing what tranny and diff you're running? I've ordered a translock from grannysspeedshop with Billet axels, but I'm interested to know what you went with.

Cheers guys - really appreciate all your feedback!

 

I'm running a Series6 5 speed and a standard Turbo LSD (4.33 ratio) with the turbo axels. Never had an issue. (Touch wood) I don't drag race, or launch at high rpm on sticky tyres which certainly helps.

"Cooling is a huge issue" - I second those remarks, make sure you pay plenty of attention to this.

 

That's incredible! Your FC is a turbo 20B right? I'm astounded you haven't broken a drive shaft couple, twisted an axel or shredded the dif! You must be fairly gentle on the right foot =) Does yours break traction easily? That could be what saves your drive train from moments of pain. I honestly never considered using a turbo drive train with the 20BT powerplant. Like yourself, I have little to no desire to drag the car. Hmmm... Food for thought indeed!

Re the cooling concerns, we're all on the same page. I'll be doing some work on the car next week. Don't be surprised if the next set of pics show two fans and no shroud =)

Cheers

 

Hey all,

Took out the radiator and flow tested it. How is nothing fancy, old school trick. Attached a wind speed tester to piece of 3" exhaust pipe about 40cm long. Closed off at one end, save for a simple hole to jam a high flow air nozzle into. Had one guy jamming the nozzle into the hole with a rubber seal, and me holding it in place on the radiators front. The results have me eating a small slice of humble pie. The air pressure was over 230psi - the aperture of the nozzle was around 6mm. The air coming out was massive, but that's no surprise. You guys sitting down? Here's the thing: Air flow measured through the centre of the radiator was almost exactly the same as that in the upper and lower corners. When I say 'almost', I mean there was a 3% difference during the tests.

Okay, I'm an engineer - so what does this tell me? Well, firstly high speed air flow isn't being restricted much at all. In fact, let's call even 10% negligible - because, well, it is. 10% is the difference between your car running at 55 instead of 50 - 110 instead of 10. These two differences do not equate in an overheat situation. In fact, my previous thought of putting a fan between the radiator and intercooler may possibly cause more restriction that heat it will help dissipate. In motion at any modest speed, the fans are redundant. When in traffic, they are gold. So the question, will adding a 2nd fan be beneficial in all but the most bizarre circumstances? My gut has me thinking no. Moreso, the restriction the fan will cause in front of the radiator is more likely to cause a problem than prevent it.

I have an assurance from the rotary shop that should the car have a cooling problem, they'll fix it at no charge. I can't argue with that. So, for now, I'm flagging the issue of cooling my ride as covered, pending heavy load testing.

Will definitely keep you all posted!

Cheers

 

Yes, Single Turbo 20B.
I don't drive the car on the street (only circuit, hillclimb, motorkhana) etc. So I am usually running some nice semi-slicks (not during motorkhana of course) and it hooks up very well. The turbo I am running is not massive, so power/boost does not come on like a light switch which helps keep traction out of corners etc.

I have had the car (within this power train) for over two years now and have competed in a tonne of driving events and never broken a driveline component. Lets hope it stays that way

Cheers

 

Thanks mate. Truly, colour me surprised!

I wonder what would happen if I only replaced the dif centre with a Kaaz 1.5 way for a while? Personally I think I'd break a dif couple/ uni joint, but the centre alone a hell of a lot cheaper than dropping in a Granny's and drive train. Honestly, I'm happy to do it if only as an experiment. The Granny's is on its way regardless, but it's not a super cheap option from start to finish. If I kill a uni or twist a drive shaft, at least other members will know what will and won't work - and I love experimenting

Cheers!

 

I didn't realise the FD was a tighter fit. Is that the only reason, or are their handeling and weight distribution advantages also?

Cheers

 

looks awsome

 

Thanks man - appreciate the compliment =)

She's at the panel beaters atm. New rear wing, rolling rear guards, touching up a little wear and tear, minor rust repair (before it became major) and reverse bonnet scoop for breathing. Well, that was the plan, but the sunroof is rusting also - what a surprise. So getting that repaired properly also - what they hey, it's only money! rofl!

 

I thought of and still thinking of a 20B swap in the future just a stupid question for all having cooling issues!!! Would V mount setup be better for cooling. Just food for thought. Thats the way I'm going for my 6 port set up till I either got 20B or 13B RE!!!

 

I've never driven a 20B in my life. Mine will be the first one. But everyone tells me the same thing - it's a life changing moment - chalk and cheese to a 13B. What can I say? I'm excited =)

I think it all comes down to space, and what you can do with it. In my case (because I chose not to move the engine and gearbox back), space was limited. No matter how I mapped it (I used cad and about a trillion measurements.) My best option was always to use the large X flow 3" core radiator and a 5" intercooler - which runs top to bottom. Remember the oil cooler is yet to come and will sit in front of the intercooler, and the air con condenser will sit to the far side of the bay front also. If I were to lean all that, I run out of room real quick and have to compromise sizing. Inside the standard nose, you have a small amount of room at the front (unless you go for the Intercooler With A Car Attached look - which I don't like.) So it made sense to place the most critical component first (oil cooler), which leaves the biggest area (in the centre) for the very large intercooler, then the semi standard area for a large core X flow radiator. The car has water injection above 8pi, so I am not concerned about a little heat soak from the oil cooler, and the radiator is large with a huge hi-flow fan.

Will I still have cooling issues? It's possible - to be honest I don't know for certain. Time will tell for sure. Bottom line is I don't have room for a larger radiator, and what I have should be enough. Worst case, if it's not, I have room for a wide (if not tall) 2nd radiator which can sit above the oil cooler. Of course I'll need to open up the front to let more air in if that's the case - which I don't want to do, but it is an option.

The car comes back from the body shop Monday - new wing fitted, guards rolled and lipped, re-painted rear end and rear guards. Reverse bonnet scoop will be done by end of next week (was needed as bonnet wouldn't close even with spacers and the struts removed.) That's fine by me, will help get heat out and air in (from the front), so all good.

Here are some pics from before she went into the body shop. 18x9's are fitted also.

Enjoy!

 

Hey all,

Finally got the new wing on, guards rolled and lipped, and the rear half of the car re-painted where needed. Sunroof and bonnet (with reverse scoop) are expected by the end of the week. Loving the look of the wing. Functional without being huge, and well within spec for engineering

Had to make a change to the screamer; Now it will go from the gate to the DP just before the cats. Once made (this week fingers crossed) it, the DP, exhaust turbine and the exhaust manifold go for ceramic coating. Going black in and out. Intake's are polished Aluminum, all exhaust system is black. So silver and black - nice balance =)

Enoy the pics!

Cheers

 

Hiya all,

Quick update -

Thermal coating done, was overdue, but has been done very well. Pics coming in the next few days.

Fuel rail, piping - easy stuff and coming along. Working on exhaust system currently. Am running one resonator before the dual high flow cats, then Y split to twin pipes and exhaust mufflers.

Biggest delays now are all electrical - meaning I need a decent auto electrician who can work well with perfornance projects. Patience grasshopper... Argh...

More pics soon!

 

The project looks great!! I have wanted to put a 20BT in an FC since the day I found out about these engines....Jan-Feb it will be a reality for me......I have a red s5 just like your car that I will be putting the 20BT in.....I am glad that you have put up all of this information so other people can get an idea of what it takes to make this a reality.....I am not looking forward to the downtime, but I know it will be worth it...I am planning on building this car into a full drag vehicle(still debating).....Debating fully tubbing the car or not.....Anyway, I don't want to take the attention away from you...It's great to see you are doing this and I can't wait for that engine to fire up!! Please post videos or links to videos....That car is going to be a beast!!!!

 

Hi man,

Thanks so much for the kind words, very much appreciated!

So we'll have 20B twins? Brilliant =) I love the look of the FC, I really do. Not taking anything away from the gen 3's looks and following, but it wasn;t the "look" I personally was after. I would have put the 20B into a 1st gen car, except a) it's not legal here, and b) the series 5 handles better =)

If you;re going to drag your FC then your job will be a lot easier than mine. Everywhere I had to be conservative, you can just go for it, but you know this already =) I did consider mini-tubbing mine, but as a street car there's no point. As things are currently, I'd have to put in a half cage to run a 9", and seriously said, I don't want to have to run a 9". Too heavy for a start. So I'm hoping my Kaaz centre experiment will pay off =)

You have to let me know what times you end up running - my guess is 9's for sure. By the way, what apex seals are you going to run? The ones we make locally are purpose built for abormally high use. They can survive lean outs and nitrous back fires without breaking, and have a replacement warranty. PM me in you would like more info.

Hoping to get those new pics tomorrow - fingers crossed!

Hey, make sure you post your project - will love to see it grow. As I was told prior to posting mine, these things never get old!

All the best!

 

Two steps forward one step back... At least it feels that way...

STILL waiting on the damned oil cooler! Not a happy camper, but wtf does one do...

The good news:

The bonnet is back and on the car - and may I say looks fanbloodytastic!! You have to look twice to even see it's been modified - and from the front it hardly stands out at all. Very standard looking - the exact desired result!

The custom exhaust system has been tacked into place for fitment and approval. With one modification I've signed off on it and it will be finalised this week. Basically we have: 4" dump going to two 3.5" cats, then 3.5 to 2.5 Y splitter. Then one resonator per exhaust channel and a very large baffle, which is so large to A) allow flow, and B) muffle the roar - to do both, you need big. All are mild steel and stainless painted black. All inners are stainless steel, no fiberglass fillers have been used. There is enough room to add another cat, or another muffler (see the pics) - this is a decision that will be made once the car is tested for emissions and noise compliance. Don't get me wrong, I want a 20B to sound like a 20B, not a V6 passenger car, but it has to be at least close to legal or I'm just asking for trouble. Why two cats, or maybe three? Well, first emissions offence in Australia is $2K, next is 30 - I **** you not. So yeah, if I have to run 3 cats, I will!

The ceramic coating has been done and done well. It's exactly what I wanted. Hard to see though, and yes I did the turbo housing inside and out to prevent heat soak and cast iron life shortening rapid temp changes. For the record, there is little to no performance value in ceramic coating the exhaust turbine. True, keeping heat in there is important to continue the expanding gas process, but the duty cycle of gas in the turbine is so short, the concept of performance gain is all but null and void. The benifits or ceramic coating the exhaust manifold, on the other hand, are noteworthy and recommended to all - hotter gasses travel faster - faster gasses make turbines spin faster and sooner. Remember though, if your coater says they can do the insode the same colour as the outside, question what the heat rating of the product is. It's well noted that adding a colour to the ceramic coating product reduces the heat resistance. Eg: Off-Wite (which is the native ceramic product) has the highest heat rating. Black has a significantly higher heat rating than Silver or other custom colours. This rule of thumb may well vary from shop to shop, as some use slightly different products. If in doubt, ring around some places, and don't discount those who do truck work - often they have been doing it a lot longer than a performance shop. And in case you're wondering, mine are off white inside, black outside. Saved me a 'little' money also, no paint dye to use.

Enjoy the pics!

 

And of course the bonnet! Tried to catch camera angles to make it visable - from the front it's anything but =)