rexhvn

Hello,
Looking at buying a 94 rx7. It has a mines piggyback ECU (not sure why) but it back fires, the owner says it's because of the ECU and it needs to be changed, is it possible just to re-map the ECU if that's what's causing it?
Thank you. Information very appreciated!

kuning

Yet, another "search button is your friend" post.
https://www.rx7club.com/showthread.p...ght=backfiring
https://www.rx7club.com/showthread.p...ght=backfiring

kuning

https://www.rx7club.com/showthread.p...ght=backfiring

Do a search before you post and read "3rd gen FAQ" for noobs. This prevents you from getting disappointed when no one reply to your post (even worst, flamed) just simply because they have been discussed for zillions of times man.

DaiOni

don't be too quick to jump on the 'use the search button' bandwagon (though it should always be your first step). This kind of issue can be really individual - and definitely not (necessarily) solved by some general advice.

"is it possible just to re-map the ECU if that's what's causing it?"

no

the mines ecu are a 'set and forget' unit - they are preset/pretuned to certain modifications. It's a very common style of modification in japan - but has (thankfully) gone out of style in the western world. It's a very inflexible method. My advice - go and get a pfc, then go get it tuned. If you wanted to add more mods, you'd need to go put it on the dyno after anyway - to see if you were within safe parameters. If you weren't you'd be screwed. Do it right from the start - invest in a real-time, retuneable ecu.

BTW - the mines ecu units are usually really expensive - more than the far better pfc - as you are paying for a 'name brand' tune. All the big workshops still do this sort of tuning - though these days it's generally added to a retuneable unit (pfc, f-con, etc). I think the japanese, in general, like to buy a car, follow a basic tuning scheme (often from a magazine), then sell the car and do it again with a new car. In the western world, cars aren't generally considered as such disposable items - and we tend to hold on to them, nurture and mod to a greater extent.

As for the backfires - fairly normal for a modded FD. What kind of backfires though, and how constant? The occasional pop, loud cracks, or a machine-gun attack?

charr33

When you say backfire, do you mean a little pop-pop when warming up? Or full out bang such as you might get when letting off the throttle after a run?

When I turn my car on at first and it is warming up (idling at say 1500-2000 depending on how cold it is) it will pop a bit until it hits 73 degrees C, then settle down into a nice hum. I know my car is running hella rich right now, so that may be it.

Also, I had a problem where my car would backfire loudly whenever I would let off the gas at all. Such as reversing into a spot, or creeping along in stop and go traffic.
Turned out I had a crack in the intake gasket which was allowing extra air into the mix.

rexhvn

It's just a little pop every now and again thank uoi.

rexhvn

The car only has pops when idling, i'm not sure about driving because i couldn't hear it over the exhaust.
Thank you.

NuTbAgSaN

wat else is done to the car? from the sounds of it, maybe full exhaust if its so loud...unless there actually is some problem with the ecu maybe, thats probably not it at all. sounds more like what charr said.
i have the same ecu for now, a pfc is the best idea though. if you can afford it, do it! i notice with both my 7s the aws doesnt really go if i start the car in gear which i do, so i dont know if higher revs during the warmup combined with an open exhaust may be causing it. that might be all it is

rt turbo

sorry to jack the thread, but people on this forum are fast to play the "search" feature. Sometimes people want to get up-to-date info from people with the cars now. These threads need to be updated every so often to make sure the most up to date info is diffused through our population. That being said, there is some things way way too played out. judge be the source.

rexhvn

I agree, i do need to purchase a power fc, they seem to be really good. Just asking sorry, i don't have the money at the moment, would it hurt not to do it now yet, still drive the car a litte? It only back fires.

DaiOni

It's hard to tell - if you don't know the mod history of the car. If you haven't modded it, and it's in the same state as it was when the ecu was added (and assuming the ecu was indeed a good match for the mods) - then it may well be withing safe parameters. That's a lot of 'ifs' though.

If you want to be sure - the smart idea would be to take it to a workshop with a dyno - and get some actual readings. A lot less $$$ than a new engine.

kuning

Den, the car backfires under decellaration (when you take your foot off the gas pedal), it's not during idle. As far as I'm aware from asking the same question about 6 months ago in this forum (which the only replied I got was to "search"). That said, the car tends to backfire because it's running pig rich from the aftermarket intake, front-pipe/DP, the 3" piping and the "no brand" SS canon-type muffler (thus the loud exhaust) with just piggy-back ECU (the Mine's).

Not believing 100% from the search results, I then turned to Bill from Rotary Performane Center in Reservoir who happens to own a s6. He told me the backfiring is normal based on the same reasons others' have mentioned (running rich, mainly exhaust gas related). He also told me that he would guarantee the backfiring would go away once I get an aftermarket ECU. But unlike those in Japan and the US, Microtech LT8 / LT10 seems to be the most popular brand sought by Ozzie rotor-head. The reason is because we have yet to find a good PFC tuner who specialize PFC tuning on rotaries although there are heaps who knows how to tune them PFC. On the other hand, we have a handfull of Aussies who not just know how to tune rotaries with Microtech but extract all Microtech's capabilities to get maximum results. One reason being, Microtech is Australian product/brand so more mechanics/tuner are familiar with it (to name some, Simon from Promaz, Vlad from Rotorworx, Stuie from BA Performance).

Having said that, I myself might not be correct about the backfiring. so I'm open to any inputs =)

p.s Dont worry, I won't try to persuade you to buy my car lol. Shop around, look for more resources/opinions so you won't be disappointed on whichever car you finally choose. Good luck mate =)

rexhvn

Thanks guys. The only has an ECU, 3 inch exhaust and HKS intercooler piping, not an intercooler lol. They are the only engine mods. While on the topic, the car was only boosting at 5 psi, what could it be?

kuning

Den, when it read 5psi what gear was it on? If I'm not mistaken, a proper boost test is done on 3rd gear @ WOT. But yeah as Daioni-san said, a dyno and mechanical check would be best your best shot to find out.

rexhvn

Yeah of course. I think i only looked at the boost gauge in 1st.

CantGoStraight

3rd gear is where you need to take a look at your boost pattern. I've found the little popping can (in most cases) be adjusted out. TPS needs to be at correct setting as this can also cause this. There is a screw adjustment under the TB elbow, you didn't mention what rpm the car was idling at or if it quit when completely warmed up.

rexhvn

Not sure what the rpm was sorry. It just had a slight pop every now and again. Not that loud but, loud even to realise. Sorry but, what does TB stand for heheh. I don't know much about rotarys.
Thank you.

CantGoStraight

TB= throttle body, the poping at idle doesn't mean a whole lot without knowing the rpm . I was able to adjust out the popping on mine but had to settle of an idle of around 11oo rpm. I still haven't checked my TPS= throttle position sensor, for correct reading at zero throttle.

rexhvn

I'm not 100% sure but i think it was reading at 0 rpm but yeah....

CantGoStraight

That's the same RPM I launch my car into the garage at. (-:

rexhvn

Just found out that the car was idling at 800rpm

CantGoStraight

Not a bad idle, might only need alittle tweaking with the adjusting screw under the TB elbow.