i ahve spoke to a few suppliers about bits for the engine and all are coming back with different advice and i really dont know where to go, please help . ok one says only replace the back box with stainless as if you do the lot it will run to rich and cause engiune problems and another says it is fine to fit a whole stainless, i was looking at a dump valve but have been told that it is pointless unless you have more than 400bhp, but another place is quite willing to sell one i really dont know who to belive so if any one has had experiance with these please help. i have been advised to get a apexi back box with induction controller a de cat and a front pipe
1. its pointless as dump valve wont improve performance on stock car, will only make a sound, your car already has a dump valve but mazda made it quiet.
2. Stainless hass nothing to do with it, your mixing things up, what they are saying is that if you replace the whole system back box, remove cat and make it more free flowing it can make the car run rich if you also add an induction kit, if you do to many mods to your car you will have to buy an ecu and have it mapped to cope with the extra modifications.
How far do you want to mod and how deep are your pockets, the guy telling you, you dont need them is just being straight with you.
If you want the dump valve noise you can disconnect the standard one from the airbox and put a bung in the hole on the airbox,as g11ary said a aftermarket one will not improve performance.
I hope these people didnt tell you that you will run rich with no cat.
If your car is a jap import their is no point changing the downpipe, as it has no cat, just get a cat back exhaust, if you remove the cat on a standard ecu you will have uncontrollable boost and will keep hitting fuel cut and run lean on boost(not good)
hang on, just because its a jap improt doesen\'t mean theres no point changing the downpipe cos it hasn\'t got a CAT, if you are replacing it with a wider pipe :)
Dave
QuoteOriginally posted by g11ary
2. Stainless hass nothing to do with it, your mixing things up, what they are saying is that if you replace the whole system back box, remove cat and make it more free flowing it can make the car run rich
Gary - don\'t you mean lean? as it will cause it to run lean, and possibly and usually will create boost spikes and boost creep as the exhaust needs a little bit of restriction in it (before you start needing, ECUs, better fuel systems etc.)
So for the 10mm bigger diameter is it worth the cost, when you still have a cat that is far more restrictive?
At the stage he is at, their are alot better parts to get the best bang for a pound.
yes I meant if you have a cat replacement, as you say there ain\'t much point having a big 3inch downpipe with a restrictive CAT
I think I am making a my pipes wider than yours joke somewhere :)
Dave
CAT Hater
hey
is it ok to run an FD with a cat replacement pipe? it has a standard exhaust otrherwise, and standard intake. should i get an ecu just to be safe? i think it should be ok but just need reassurance.
rich
I ran mine like this for quite a while, with a cat back on aswell, my car was fine, I kept the boost down to 9-10psi.
You have to be careful, e.g.if your fuel system isn\'t upto scratch you could run lean, I recommend to having the AF checked after you do it.(with a proper wideband)
My opinion is that should be ok, the stock exhaust is fairly restrictive, the trouble starts when you have a free flowing system and not enough fuel going in to compensate
Get an new ECU, a aftermarket backbox, a larger downpipe, and release those horses :)
If you ever have any doubts get your car to one of the rx-7 specialists and have them check it ain\'t running lean with a o2 sensor
Dave
that\'s basically what mine\'s having done to it now (plus an itty-bitty street porting :D )
Now way I\'d risk opening up the exhaust (car removal) withough sorting at least the ECU out.
Iain
induction kit £124+vat,stainless steel front pipe£175+vat decat £60+vat apexi i back £410+vat and a all important ecu , is it worth getting iridium plugs and an uprated fuel system while i am at it ? i see i am going to need deep pockets here .
Mate if i was you don\'t spend your money on a downpipe, i did and untill last week i suffered from boost spikes.
This can be realy bad for the car, it will spike\'s if you have a apexi ecu with standard map @ .925 of a bar. This is quite heavy to suddenly have a cut.
I\'ve now got decat and hks exhaust, ecu, apexi induction. This is a good stage 1. Just do that to start with.
GET the ECU, trust me i suffered from a lean engine, cost me a rebuild.
I just got my Racing Beat cat back in from the US. I went to get it fitted on Saturday only to find (and this is where I feel like at .........) someone has already a 3" system.
By the looks of it they have also replaced the cat, which would explain some of the backfiring. I have decided not to do anything with the intake side because of this.
PFC seems to be the flavour of choice. Who is good for the PFC ?
Ross @ //www.dragonperformance.co.uk have got some 2nd hand ones i think.
Cheers
pip at wgt done me a good price