BackThe Rotary Guru's Q&A's
The Rotary Guru Thanks you for all your queries (there are alot of Rx7's out there!). Here are a few questions with replies.
Hi Simon. I am currently contemplating if I should change over the car I am driving now, for a 1989-1991 RX-7 turbo. I am now driving a 1992 Subaru RS-turbo. It handles very well and is literally problem free. It also has the wondersof a quad cam boxer engine, and the stability of a 4wd too. I am wondering if it is worthwhile trading in these for a RX-7. I really like the looks of the 1988-91 series RX-7, but am wondering if the power is better than my RS-turbo. Also, I am a bit skeptical on the reliability of a rotary engine (especially one of that age), because I have never owned one before. What benefits are there in a rotary engine compared with the normal engine?? I really appreciate your advise. Thanks and best regards,
Shien.
Dear Shien,
The Rx7 you are interested in is the Series 5 Rx7. It has a fuel injected, turbo charged and intercooled 13B which pumps out 165 kW (221 hp). The car weighs about 1400 kg. Your RS turbo's 2 litre turbo boxer peaks at 155 kW (207 hp) and weighs roughly the same as the Rx7 meaning straight-line performance will be pretty similar. Your Rs turbo will have a handling advantage being 4 wheel drive 8-) , but overall the Rx7 would be more fun and more challenging to drive being only rear wheel drive ( there's nothing like going sideways around a corner on full opposite lock). Both of these cars have very good factory suspension and will blow the doors off just about all the cars on the road ( especially big, heavy shit box V8's!!).
The advantages of this Rx7 and the rotary are many - increasing the power output of the 13B turbo isn't expensive or difficult and ultimately the 13B has more affordable potential than the boxer, if you were to go really sick. I have see this 13BT engine in an Australian Drag car putting out 550 Hp!!! ( Rx3 - (9.42 @ 145mph!!). The rotary sounds terrific and is very responsive, and yes, the series 5 Rx7 looks very horny!!
My advise is this - I wish I had your problem!! They are 2 grouse cars - I have got NOTHING against the RS Turbo, infact I think it's a terrific car ( especially the Impreza WRX too!!!). Both are great sports cars but I lean towards the Mazda. But you must remember practicallity - the RS turbo is a 4 door sedan and Rx7 is a 2+2 coupe - this means only comfy seating for 2. If you really wanted a top car save up your penny's and go for a current model series 6/7 twin turbo Rx7. Now that's a top car!!!
Late model rotary reliability ( I consider 89 late model) is just as good as piston engines. Check for good compression, no smoke from exhaust (especially high revs on trailing throttle i.e. decelerating) and if possible condition of turbo and intercooler.
Happy car hunting
Simon the Guru
hi
alternative fuel systems for rotaries- I wouldn't mind finding out any information available on LPG powered rotaries. My plan is a RX-2 (initially a 4 door development car followed by a coupe once I've worked things out) with a 13B twin turbo motor (the cosmo type). The current plan is to get the car running with out the turbos (bloody recirculating ball steering) and then install the turbos, either (or both) by fitting rack an pinion or remounting the rear (secondary) turbo to where the battery sits, the primary can stay as is. Chance of success? The turbo manifold readily splits to separate the two turbos, but I wonder on the affect of leaving the primary turbo in the standard position and moving the secondary. Remounting the secondary would involve approx 4 90o bends and 400-500mm of piping, and I have no idea on the affect of this. Also I have no idea on how to control the sequential operation of the turbos, if I can not make them work sequentially I'll run them simultaneous. Back to LPG, do you know anything about it. At this stage I'll use IMPCO 425 mixer(s). Running naturally aspirated I think that one 425 my be too restrictive. If I do use two they would installed sequentially 1 running from the primary chokes on the throttle bodies the other from the secondaries.
Thanks .. Brendan
Hi Brendan,
Sorry this reply took so long, the Guru has been pretty busy lately. Your project sounds like a big one, but a very interesting one!! My advice about firstly squeezing the 13B REW-TT into your Rx2 is to relocate the second turbo, not fit rack and pinion steering - this would be a big job. If you use the same diameter piping and nice mandrel bends I don't seem to think the relocation will have any adverse effects.
The engine you are after is a very nice twin turbo 13B which in standard trim outputs around 190Kw (255hp) in Jap import form ( Aust Rx7's were a bit restricted with emissions - around 176Kw officially quoted hmm 8-( ) The turbo setup as you already know is a sequential setup - A small turbo runs through the lower rev range, then in the higher revs the larger ones kicks in. This provides good low down response and limits lag, but also gives you big turbo punch up top 8-). Note- in the low rev range when the smaller turbo is in operation, exhaust gas is still bled through the larger turbo in order to keep it spinning for quick response when it comes in later. The change over function I think is controlled by the engine computer hhmmm. I really don't think this system can be run simultaneously - not 100% sure though. From what I've seen about people wanting max power out of this engine, is the removal of the twin turbo setup and fitting one big one like a garret To4 ( e.g. Lance Warren's Cosmo, Pac performance Rx-3 . I know these are 3 rotor engines but the orig twin turbo induction is basically the same as your 13B -REW TT.) Personally I'd persist with the tt as this is more individual and a good project.
With turbos straight gas is DEFINATELY the go. The increased octane rating of gas (105-110) allows for more boost and the fuel is nice and cool aswell, decreasing chances of detonation. With Straight Gas no efi computer is needed, only gas converters and mixers. The Only problem with this is the control of the twin turbo change over - I'm a bit short on ideas there - write to Mazda Aust and ask how it is exactly controlled and then see what can be incorporated in with the gas. I think you will also require twin gas converters and maybe even twin mixers - I recommend GAS RESEARCH mixers. They are the best in the business ( Gas Research is in Dandenong Victoria). michael00@telstra.easymail.com has a Straight Gas GAS RESEARCH system on his Rx3 and will answer any gas questions you may have. Your Primary/Secondary converter setup sound alright too.
Best of luck with the project and please keep Michael and Simon (of this page) informed and also send us pics of your car etc and we'll put them on the page!!!!
Hello,
How are you? My name is Carlos. I just bought a 79 rx7 Limited for 500 in pretty good shape. It only needs a paint job. My questions are; What makes this car limited? Where can I find information on what makes it different?
Tks lots,
Carlos
Dear Carlos,
Congratulations on buying the Rx7, you've made a wise choice - rotary power is definately the way to go. Your Rx7 is a series 1 model - I'm not sure about the 'limited' model - what country are you from??? I will do some research for you - As for info regarding differences, the first place to try would be your local Mazda dealer. They can be quite helpful and occasionally you find a Rotary nut working there!
Happy Rotoring
Simon The Guru
Simon:
We recently bought my wife a 1988 RX7 GLC automatic for a reasonable price, only to find that when you start out, it has very little pick up. I have been working on cars off and on for a couple of years, (but never rotary) and inherited a '88 convertible a few months before, so bought the glc thinking that if there were two, it'd be easy to figure out what's right and what's not -I was wrong, cause, I can't seem to give this thing any power. I did buy a book, and swapped some parts - mostly sensors - between the two, thinking that emission control had to be the problem, but to no avail..Needless to say, I was hopeing you might be able to give me some direction as to what to look for.
Dear Rx7 owner 8-),
Your Rx7 is a series 4 or 5 non turbo model - these cars came fitted with with a 13B 6 PORT engine. It is a little hard to diagnose your fault over the web - but I'll give you a few tips. Firstly don't expect the auto car's acceleration to match the manual car's. Generally Rotaries and autos don't mix too well. Check your engine mixtures with an exhaust gas analyser, check operation of oxygen sensor, check condition of spark plugs, coil pack and leads. If you get desperate, go to your local Mazda dealer and see what they think.
good luck
Happy Rotaring
Simon the Guru