first topic! kick ass! Rotary engines

[dubber91]

ok ok...modern ones are ford engines...but i mean the real ones.....the rx7s....

The rotary engine has got some bad press over the years......rebuilds after 60k miles, blown turbos, cooling issues, unreliability....and to be honest with you its unfounded. The NA engines will often do in excess of 100k miles, which is more than can be said for some reciprocating inline engines! Turbo'd engines do last less well, but the expense to rebuild is not as great as some may expect, especially when importing parts from the states.
The NA was my weapon of choice, from a rotary between 86 and 91 i beleive. This engine is denoted the 13b. It is also possible to get the 13bT, but i chose to stick with NA due to money and complexity. The 13b engine is quoted as 146BHP, but considerable gains are possible with minor modifications. Porting is very popular (much like the port and polish of a cylinder head) but in % terms it yeilds much larger gains than from standard engines. Indeed, i have heard claims of 300BHP from a NA 13b, although driveablity becomes an issue with race ports. Porting is easy to do, so im told, and it is simply a case of widening/smoothing intakes in the intermediade and side housings. You can buy templates to stick to the engine to guide you as to how much material to take off.....theres no secrets to it like of reciprocating engines. The 12a is the another popular engine, which is from rx7's 86 and earlier. Also rx2s had them. These are slightly smaller in capacity (2.4 technically speaking) and use a less complicated elecrical system (easily integrated into the VW beetle loom). The push out a moderate 100BHP but you can get pretty quick cars if you fit a single 48IDA instead of the four barrel Nikki carb it uses as stock. Again rules for porting apply.
Later engines, with the renowned twin turbo, i know very little about. The electronics become much more difficult, and rebuilding them is more expensive. They are, however, based upon the 13b engine block, and therefore i see no reason why one wouldnt fit into the bug engine bay (i can say anything about the turbo location)

Fuel management systems can yeild huge gains, microtech, apexi and others are very popular, especially when coupled with ports, induction and exhaust work.
Rotaries rely upon backpressure to operate. They need a correctly flowed exhaust of suitable length in order to yeild best performance, but i have got away with a short one for now. Ideally i will make one to travel backwards, over the gearbox, and out at the side. Exhaust temperatures can reach 2000 degrees farenheight (due to 3 sparks per rotation and the combustion of oil with the fuel), so care must be taken when building an exhaust. www.mazdarotaryclub.com is a great forum for advice on all matters.

Cooling a rotary can be a problem...they can run very warm. The mazda pump isnt really up to big lengths of coolant lines, so an external additional electric water pump can be used (try a Vr6 or 16V renault for a scrap yard find). I bought my rad from Andy raw at TSR, but i have heard a Golf GTi radiator will cool one.

Wiring for me (im useless at it) was done by TSR, but i shall be spending some time neatening it all up, and so can help with the wiring if you need.

The adapter plate is available from kennedy engineering, but i warn you, the flywheel should be torqued to 400Nm! a big extension bar is needed, with 54mm socket (although 56mm is easier to get and will suffice. same size as a transit hub socket)

Also recommended is a 6V starter to run on 12v as it will spin up quicker. Longevity suffers, but VW starters do cope relatively well. This often means changing the starter bush, and the flywheel must be of the correct type.

Thats all i can think of at the moment, if anyone has questions, let me know!

Steve

[dubber91]

Next up, rotaries require oil coolers. The stock one is really an amazing peice of work. It has a thermostat bypass integrally, to prevent excessive cold running. When operating, the oil cooler has a large number of coils wound for a very efficient cooling of the oil. It may be cumbersome...BUT KEEP IT! you wont beat it for cooling potential.

Next is the engine mounting. Many people have made up different methods of supporting the engine other than the gearbox. I solid mounted my gearbox, and had a brace made up, running down where the rubber engine seal would on a stock VW engine. A bar then goes underneath two webs on the front of the engine. I have heard of people using a good quality (e.g. Gene berg) traction bar with a little modification. To be honest, mine is probably a little over-engineered.

A good fuel pump is required to circulate the fuel (a fuel return is a must) and i recommend uprating the clutch...a kennedy stage 1 will suffice, as a stage two is nothing more than an on/off switch!

I am endevouring to improve my braking system (due to the lack ofengine braking with a rotary engine) and i would recomend rear disks and a brake bias adjust to keep the back end inline.

[dubber91]

heres some more detialled pics i took whilst fitting the engine...again!


thats the engine out, i was just torqeing up the flywheel. There you can see the VW starter ring heat-shrunk onto the mazda centre, and the adapterplate behind it.
Below is a simple pic of the solid mounted gearbox, and various electrical gubbins required to get her runnin..


Heres the additional electric waterpump im fitting, from a Vr6...ill let ya now if it works!



Engine in....you can clearly see the engine mount that was made up....Bolting to the webbings on the front of the engine.



The exhaust is short......and gets very hot as you can see!
Just to scare those of you who dont like electrics



a pic of the oil cooler above the transmission....



a confusiong one of the exhaust....



another one i got kicking around.....its huge!



vaious other bits you dont need on a bug.....essentially an air pump for the emissions control system.... It is used to pump oxygen into the exhaust which oxidises the excess hydrocarbons and CO in the exhaust.... used because cats were known to break up under the higher temps experienced...




valance on....filter on....


and finally a bonus one of the cooling system....i added a bike fan for some extra sucking/blowing!

[fbiiburton]

Well impresive that is. Looking into a rotory engine for my bug. Very intresting information thanks

[dubber91]

glad you enjoy it

Steve

[famous phil]

here's one for yer , 4 plug leads n 8 pistons?

made a nice job there , how many rpm does it run at , and whats the torque
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Auto Union Munga Jeep ,T4 2.4td , T4 2.5tdi ,Mercedes S Class on LPG , 66 splity deluxe , GP mk1, 3 type 25s 1 with 1.9dt pug engine + 1 with N/A pug engine ,,there are 6 t25s with pug power in Darlington

[rusty69bus]

i count five

[famous phil]

can't quite see but was working on 4 for the rear brakes n 4 fert front
looks like his made a good job of it ,
the was once a prototype diesel , pigyback setup with small rotor ontop of slightly larger one as to get the compresion
_________________
Auto Union Munga Jeep ,T4 2.4td , T4 2.5tdi ,Mercedes S Class on LPG , 66 splity deluxe , GP mk1, 3 type 25s 1 with 1.9dt pug engine + 1 with N/A pug engine ,,there are 6 t25s with pug power in Darlington

[fbiiburton]

[dubber91]

theres a leading and a trailing spark plug fo each rotor. Therefore there are two sparks per combustion event. It basiclly helps reduce unburned hydrocarbons due to the inefficient combustion chamber shape. There are two coil packs, one for the leading plug, one for the trailing.
8 cylinders? front and rear brakes?
A rotary can be catagorised as one of three capacities. 1.3, 2.6 or 3.9. Depends how you calculae it!
either way theres only two rotors each with three sides '6 cylinder' if you like.

and as for the torque i assume your making a comment upon the 'hearsay' that states that rotaries have no torque?
torque is proportional to power and RPM. Stock rotaries only rev to 7-8K. Not that high. Max power (as with any piston engine) is at 6500RPM. Max torque is at 3500rpm
Rotaries make torque VERY early in the rev range, they have no parasitic loses such as valves or massive rotating masses. Stock, big, american V8s only make massive torque because of their low volumetric efficiency at higher RPM, and they have relatively low power output for their size. The rotary torque curve is superbly flat until you bolt turbos on.
In fact the REASON most people love rotaries is smooth power delivery. that means a smooth torque delivery

[famous phil]

as for the piston joke its somet the rx lads get all the time ,

now when they refer to the two banks of rotors equivalent to a v12 when the 4 stroke factor is taken into account ,
i once new of one that was made into a three bank rotory engine , was a lot of work involved making centre shaft (to them that dont know crankshaft but not a crank ) and yes they run so smoooooooooth
no parts flying changing direction at 100 times a second ,

then there's the mayflower prototype engine , a 4 stroke loose's a lot of power as it fire's at T.D.C just like a hamer hiting a steel pin then has to force crank circular , but the maflower has an intermediate crank and conecting rods so as the main crank passes T.D.C the intermediate crank keeps the piston at T.D.C untill maybe 15 degs past far less stress & emisions and good increase in bhp to cubic capacity , only thing to its disadvantage was the amount of extra moving parts enough said for now me think LOL, carry on the good work M8
_________________
Auto Union Munga Jeep ,T4 2.4td , T4 2.5tdi ,Mercedes S Class on LPG , 66 splity deluxe , GP mk1, 3 type 25s 1 with 1.9dt pug engine + 1 with N/A pug engine ,,there are 6 t25s with pug power in Darlington

[dubber91]

ah right. I dont bother with the piston jokes. Ive been caught by the rotary bug! (pun most definitely intended!)

the centre shaft is normally called an eccentricshaft. you can get them from cosmos, but have you seen my friends 4 rotor motor? :p





as for the prototype ive never seen it. However, ive seen some VERY interesting variable compression ratio engines. They are beautifully simple.

Steve