hello.i have a major problem.my car is a 92 type rfully adjustable suspension,strut braces front and rear,a racing clutch and a blitz exhaust.the car was working fine,20ft tracks of rubber in second gear etc,until my brother took it out for ten minutes one saturday night.he hammered it,pinging it off the rev limiter in every gear and whatnot,then put it back in the garage and it seemed to be running fine.the next day we pulled the fuel relay out to see if it would run without it in.it did so we put it back.then my other brother went to fill it up.he floored it and when it got to one bar of boost it violentley shut off the engine and made a huge explosion.so now it wont go past 1 bar.if you accelerate slowly you can reach 80mph but as soon as you floor it its jerk and bang time. we have reset the ecu and it has an aftermarket earthing kit on it.what have we done?does anyone know whats up?also in the dark now if you stand behind the car you can see little embers coming out of the exhaust and the manifold is blowing,presumedly from all the explosions.can anyone suggest anything?
also does anyone know any rx7 mechanics in or near the northeast?
Wow don\'t know where to start really!!
If the car sounds like a volkswagen beetle you could of bust a apex seal. You could of blown a pip off of the map sensor, you could of blown the inlet manifold gasket being a 92 car you\'ll have crap paper gasket that likes to blow especially at 1bar of boost. Have no idea how you hit 1bar of boost with just those mods you listed??
can we take it you\'ve at least broken yer
Brother(s) (http://www.computerpannen.com/cwm/otn/shocked/Wow1.gif)
lol if not funny hope you get to the bottom of it & sort it soon...........
Si
Is it a standard ECU? If it is - doesnt running 1+ bar of boost damage the engine?
I have an Apexi PFC and mine is running 1.3 bar max, even though i have a PFC it still fuel cuts at this amount of boost. I am having to get my hand controller fixed so i can lower the amount of boost as at the moment hard acceleration is tricky and i dont want to damage my engine.
From what you have said and my limited knowledge (most of it from this forum) you are looking at a rebuild and possibly an expensive one. Hopefully i am wrong and i\'m sure some of the more technical guys will be able to help further.
Graham, you seriously need to turn down the wastegate duty cycle and boost on that. I\'m not surprised you are getting boost cut at 1.3 bar. Set it to one bar and get it set up properly by someone.
Also are you aware that the stock Apexi map stops at 1.2 bar anyway, more boost and the maps the same - she\'ll blow.
Doggy fizzle, sounds like you knackered it. Bouncing them off the limiter is not good for them. That is why Mazda had the wisdom to fit a rev buzzer.
Regards
Max
Has anyone thought about the Cat breaking up? That could be the source of the embers?
A know a few jerks were mentioned. I think if you drove a friend\'s car, (or your own) bouncing it off the rev limiter, in every gear, then you are the jerk.
I\'ll bet these same people are going to now walk around saying the Rotary is unreliable. :-(
Hi And Welcome to MRC, l just wish you had found us in happier circumstances,
Unfortunately it sounds as though you may have lost compression on one Rotor due to a damaged \'\'Tip\'\' sadly if this is the case it would have almost certainly been caused by \'\' bouncing off the Rev limiter\'\' and not the poor engines fault.
If you go to the thread below it will explain how to check the compression on your Rotary.
http://www.mazdarotaryclub.com/forums/showthread.php?s=&threadid=3813
Hope this helps.
hello,thanks for your replys.i made a mistake with the 1 bar thing,the gauge actually reads 1 kg/cm2 when it cuts out.someone has mentioned before that it might be the cat breaking up and therefore the exhaust cant generate the correct back pressure.i will try the compression test next,and if any one wants to visit my brother he is now in ward 53,sunderland general hospital.
thanks
QuoteOriginally posted by doggyfizzle
i made a mistake with the 1 bar thing,the gauge actually reads 1 kg/cm2
Hardly any different, 1bar = 1.02kg/cm2...
so why is the car boosting that high?as far as i know it has a stock ecu.how do i turn the boost down?help me obi wans
Get a boost controller, or put some restriction back in the exhaust.
Third way, buy yourself an Apexi power fc ecu and turn down the wastgate duty cycle figures.
Regards
Max
Is it just the back box you have? do you still have a cat, or a straight thru pipe in its place? The easiest way to control the boost is to add exhaust back pressure e.g. more restrictive back box or swap straight thru mid pipe (if u have one) for a cat. converter.
With a free-er flowing exhaust the drop in back pressure can easily over whelm the stock turbo control system. The pissy little stock wastegate physically cant ditch enough gas quickly enough to maintain control over how hard the turbos are working. Result, you get a combination of boost spike and creep i.e. more boost than that set.
Apologies, DoggyFizzle for my hostile post, but I cant help but get p*ssed off with people with no mechanical sympathy. I couldnt bring myself to write it nicely like Clive did!!! :-)
Really sorry for you, guy. I hope the bank acc doesnt take too much of a beating. (Like the one I\'ll give give your brother if I ever meet him) :-))
The advice you\'ve received so far is good - a compression test is definitely the next step , to ascertain the condition of the engine. It is unfortunately a myth that the Rotary engine can withstand high revs - Apex seals especially. The RX-8 can rev a bit higher, but the internals are slightly different to withstand the revving.
The beeper is a good place to change gear, if you must rev that high.
Let us know what happens next
sorry to change the subject slightly but Maxim, what do you mean by:
"you seriously need to turn down the wastegate duty cycle"
I don\'t understand what a wastgate duty cycle is?
Cheers
Dave
hello,martiny no offence was taken at all,so dont worry.my next step is to take the cat off and see if there are any guts left in it.after reading the rest of the website and a few others,such as rob robinettes.i have checked the hoses and they all seem fine and i was going to check the y pipe but when i looked it has an aluminium one.i thought they were plastic?
the car has a huge cat on it,so i am assuming the blitz is just an after cat kit.
also,does anyone know where the engine number is located,like on the block or head?
oh,my headlights will go up when turned on but wont go back down,although if you turn the manual knobs a couple of times they whizz down then back and remove the skin from your fingers.any ideas how to fix them?
thanks for everyones help.
general lee,1969
The Power fc controls boost by using the duty cycle of the solenoid valve. This is a percentage of open and closed cycles for the solenoid valve, which in turn controls the wastegate
This is otherwise known as base duty, wastegate duty or solenoid valve duty. It is this percentage which gives different levels of boost, the lower the percentage, the lower the boost.
screen looks a little like this:
Settings 1
Boost primary 0.8 bar 56%
Boost Secondary 0.7 bar 62%
Settings 2
Boost primary 0.9 bar 62%
Boost Secondary 0.8 bar 70%
(these numbers are accessable on a Apexi commander.
When you nail the throttle, the solenoid valve which controls the wastegate jumps straight to 56% duty cycle which will give you xxx amount of boost, then the ecu tries to compensate for any over or under boost to reach the desired pressure (0.8 bar). Think of it as the 56% is the intial boost level, the 0.8 bar is the target boost figure.
If the % figure is too high, then the boost will initially go way beyond the 0.8 bar (spike), then recover to 0.8 bar.
Too low a percentage and the boost will be laggy and take a while to reach 0.8 bar.
A stock car will boost properly with the pre programmed figures above. If you start changing downpipe etc and reducing restriction, then the extra gas flow will mean that boost will jump up, so you\'ll need the reduce each of the percentage values, normally about 6-10% off each of the values, or you\'ll spike.
Any clearer?
Regards
Max
Right, so this explains why you get boost spikes when you change components in the car, as the base map of the std ECU is configured for a static setup, i.e as it rolls out of the factory!
Thanks for the info mate :D
I seem to THINK only the early cars had plastic Y Pipes, and Mazda changed them later????
Yep, placky y-pipes went in the \'95/\'96 along with the 8bit ecu\'s I think?
i have had an idea,although how bright it is remains to be seen.last year i had a mitsubishi gto twin turbo,i decided to try a mod i read about,on how to increase boost.it involved using a valve bought from an aquarium store and some pipe,to make a cheap boost controller.
now,shall i try this on my rx7,putting the valve in the pipe that goes to my wastegate controller and fully opening the valve,then slowly closing it until im back to stock boost,or am i totally wrong?
if i buy a proper boost controller,would this cure my overboost problem?im sorry i dont know much about turbo engines and especially a rotary,so dont scream at me too much:)