My 20B powered RX7

[WindWalker]

Love seeing the detail of these rotary engines. I’ve never really had any dealings with them so don’t know much about them.

As an apprentice we did have the odd Ro8o in with non start/bad starting which I believe was down to rotor tips on those wearing out. Those that didn’t buy a new car had a Ford V4 conversion (or V6) but I never saw any that had that done.

Nice bit of welding as well

 

[mccarthy]

is that the garage on the right? by station where it has big forcourt at the front then it drops back to the work shop? used to me a bmw place i belive?

Yep thats the one. Its now Carbontek which my brother owns. I'm Just behind them.

 

[mccarthy]

Love seeing the detail of these rotary engines. I’ve never really had any dealings with them so don’t know much about them.

As an apprentice we did have the odd Ro8o in with non start/bad starting which I believe was down to rotor tips on those wearing out. Those that didn’t buy a new car had a Ford V4 conversion (or V6) but I never saw any that had that done.

Nice bit of welding as well

Yeah it was the very commen conversion. Persoanlly i'd love to find a mint one and drop a 400hp twin rotor in there.

 

[BillJ]

As an apprentice we did have the odd Ro8o in with non start/bad starting which I believe was down to rotor tips on those wearing out. Those that didn’t buy a new car had a Ford V4 conversion (or V6) but I never saw any that had that done.

I'm fascinated by them too although I've never actually worked on one. I believe that the main problem with the Ro80 was lack of any rev limiting so with an engine so willing to rev, people wore out the rotor tips in fairly short order. Reading an article on them some time ago, one of the guys that did a lot of those V4 conversions started looking at his mounting pile of old rotary engines and engineered a solution using carbon-fibre rotor tips. He then ended up converting many of his V4 conversions back to reconditioned rotary engines. It was pretty good going to get people to pay twice, I reckon

 

[weejimmy1]

sweeeet
loving your project . i wanted a tripple in my fd but couldnt afford it and didnt want to do it myself.
but i did get a t78 turbo and some big street ports.
would love to do a triple at some point,

and your car even looks good. so many rx7 get ruined with stupid looking mods but i like yours,

what did you have to do to get the trippple in there?
and do you know if it affects the 50/50 weight at all

 

[mccarthy]

I'm fascinated by them too although I've never actually worked on one. I believe that the main problem with the Ro80 was lack of any rev limiting so with an engine so willing to rev, people wore out the rotor tips in fairly short order. Reading an article on them some time ago, one of the guys that did a lot of those V4 conversions started looking at his mounting pile of old rotary engines and engineered a solution using carbon-fibre rotor tips. He then ended up converting many of his V4 conversions back to reconditioned rotary engines. It was pretty good going to get people to pay twice, I reckon

The carbon tips are great in N/A engines. No good for the turbo'd ones. The OEM Mazda tips are very very good tips. Good for some silly HP numbers. I'm trying out a new set in this one developed by a compnay in in Australia. We'll see how they pan out.

But yeah i see what you mean, "agh yes your rotary is broken. Here have v4 conversion". 2 months later "yes, your rotary is fully recon'd lets put it back in"!

sweeeet
loving your project . i wanted a tripple in my fd but couldnt afford it and didnt want to do it myself.
but i did get a t78 turbo and some big street ports.
would love to do a triple at some point,

and your car even looks good. so many rx7 get ruined with stupid looking mods but i like yours,

what did you have to do to get the trippple in there?
and do you know if it affects the 50/50 weight at all

Cheers, so do you have an fd then?

Its a big project without doubt. The gearbox and engine bolt straight up. Use all the normal FD clutch etc. So thats easy. You can now buy either new engine mounts to fit the 20B to the stock FD subframe. Mine has a totally new subframe. This one also drops the steering rack down and forward so the 20B sump doesn't hit. This then needs tie rod ends with bump steer correction. Not 100% bolt in and go. The machanical fitting is the easy part. The wiring is where it takes the time. New ecu etc etc.

As far as weight goes the 20B is 16kg heavier than the 13B twin rotor. That weight is all the the front of the engine over the front wheels. So yes it does effect the handling in that respect. However i have a chromoly cage going in the back with weighs 46.5kg so that issue should sort itself out. If it doesn't and its understeery that i'll move the engine back and cut the firewall

All fun a games.

 

[weejimmy1]

cool.
yeah i have a fd, its stock 93, with 99 spec front bumper / spliter.
then the engine is t78 turbo , power fc, extended street ports, 1600cc inj etcetc.

i know therers some people who move 20b back in the fd and some that dont. im not convinced it needs to be.
as you can put battery in boot along with a few other bits and bobs to even it out a bit.

do you mean the bendy seals? the ones that bend instead of exploding if you det~~?

also have you seen the new alloy rotors being made? allow it to rev to 12k. but there making lighter ones that should go to 15k . . . . nice

 

[mccarthy]

Yeah seen the billet ones up close, very nice.

Some of the upperinlet manifold "in the making" Its pretty mush a similar size to the stock item. Slightly larger. Should make the air flow more equal across the 6 ports

 

[BO0557]

nice build happening here man..

how come the custom inlet manifold ?? the stock ones with a bit of porting can make 1000hp easy...

 

[Rick]

Nice project, the tripple rotors are awesome, out of interest though, why use such a big turbo with a mild ish port job. You'd be better with more wild ports on the bigger turbo to promote spool, although you'll loose the very low down power you'll gain in the midrange and up top.

Also, whats the plenum volume and what are the bends your using on it?

Nice work. Keep it up.

 

[mccarthy]

nice build happening here man..

how come the custom inlet manifold ?? the stock ones with a bit of porting can make 1000hp easy...

I'll be using a 80mm singe throttle body so i want to use a custom inlet to suite. Also when the engine is shunted back so i'll be running a V-mounted system so having the TB so close to the front of the engine the pipe runs will be much shorter.

Nice project, the tripple rotors are awesome, out of interest though, why use such a big turbo with a mild ish port job. You'd be better with more wild ports on the bigger turbo to promote spool, although you'll loose the very low down power you'll gain in the midrange and up top.

Also, whats the plenum volume and what are the bends your using on it?

Nice work. Keep it up.

The ports on the engine are extended street ports. Wilder bridge ports would be not so favourable for what i'm doing with the car. She'll still make power well over the 500hp mark.

A smaller turbine would choke very quickly. A unit in the GT40 range couldn't handle the volume of air thrown out by a 20B. Usually the best suited turbo's are things of a similaer size to the GT45 or 55. That one is a 42 hybrid unit. perfect for the engine and flow. She'll have no major problems in the Spooling department.

The volume on that version onf the plenum is very similar to the stock plenum. Ther something like a 2D bend. Not too harsh. I'm doing another whicch will be higher volume then to the dyno with both and see what happens

 

[tigler]

Whats durability REALLY like on these big number rotary's ? You hear all sorts of stories from bullet proof to grenades !! My theory is that they are like 2 stokes and need routine rebuilds to be reliable. Whats the truth ?

 

[mccarthy]

If built well with new parts then yes ther are very strong in a flat out racing enviroment. They love been in the high revs as can be there for very long periods of time with no effort even in a 700hp application. Alot depends on the use aswell. If your building a drag engine with huge peripheral ports and a bigger turbine with 2bar of boost your putting enormous strain on the engine with the impacts of launching. These engine are not any less reliable but require much more frequent services and checks to maintain the power. In a circuit application you run less boost say 1.2 bar less stess on all the ancillaries.

As with ANY engine weather v8/flat 4 or rotary. High performnace engine has a shorter shelf life than a stock one. If for example a stanard 13B twin turbo RX7 has an engine life of 80,000mile then the 500hp version has a 40,000mile life due to the extra stresses, heat and pressure. The 20B is much the same.

I have this 20B turbo for racing so mileage will be limited. However i am also building a none turbo Peripheral ported 13B for my daily driver. I wouldn't be doing that if i though i'd be rebuiling all the time.

 

[tigler]

So they are more sensitive to the way they are used then ? This is a discussion I frequently have with a buddy who has the same rex as you. He is always singing it's praises but has needed 4 engine rebuilds in the past 14 months , each one proclaimed as the one that will outlast any piston rubbish I care to mention , then the inevitable occurs , BANG !! I try not to gloat that my poor little Evo 6 , knocking out a paltry 400 gets ragged whenever it's used and has yet to show any signs of distress. Not to mention other mates with Evo's pushing upto 700 without any issues. Same applies to other types of Jap too , S14's , R32's , R33's , R34's, Supra's , Pulsars , Starlets , etc , etc.
Probably there are reliable Rex's out there but I reckon they are in the minority , I hear more bad than good and have had 3 direct experiences with mates where their Rex has Claymored or always seems to have niggling problems.
Respect though , it's good to see someone committed to their chosen ride.

 

[mccarthy]

All depnds how well there built. Then the car is only as good as the mapper who tunes it. 4 engine in 14 months!!!! Not good at all.

 

[mccarthy]

Not much in terms of progress!!! been very busy with the Daily driver FC3.

Anyway stage 1 of the fuel cell

 

[Dr pepper]

Like the dr pepper can.

 

[mccarthy]

Cheers for the comments people,

Work on the fuel cell

I got a diffuser through today. No brakets tho same but it was a bargin so wohoo!!

Anyway i made it sit a little lower that it would usually.

I'll be finishing the exhaust in the next few days. The turbo has gone off for inspection today possiblely a change on the rear turbine housing. Info to follow.

Finalised the exhaust system now to suite the ground effects

New mid section:

 

[mccarthy]

Rear mufflers

 

[mccarthy]

Quick pics of the mufflers in place... not attached but in place!