Rich & Retard

[wolverine]

where is the ECU getting it's boost signal from to detect 'overboosting'?

[courier33]

Its reading it from the Air Flow Meter. The factory ecu knows what load points are 'normal' for the stock engine and what load points are only capable of reaching during excess boost.

[silversr33]

Fuel cut in a R33 GTS-t ECU?

Yeah, most stock ECUs in 90s up turbo cars have a point at which they'll fuel cut to prevent critical damage. Do a web search it's a very common ECU tactic, as is R&R as a less invasive, immediate measure.

googled this from a document talking about fuel cut from FC rx-7s:

"The stock fuel system is programmed to prevent overboosting the car by cutting fuel past about 8.5 PSI. This system is designed to protect the engine and must be defeated if higher then stock boost is run. Fuel cut feels a bit like the car hitting a wall just after 8 PSI. The Fuel Cut Defender (or FCD) is available from most of the vendors (there is also a DIY version) to trick the ECU into thinking that the car is running less then 8.5 PSI of boost, thus avoiding fuel cut."

Here's one about 90s toyota MR2s

"You're having a great time boosting onto the freeway. You shift into third and floor it and that's when it happens--you feel like you've hit a wall and the check engine light is on. "What's wrong with my baby?" you cry out! Worse yet, now every time you give it anything but a light amount of throttle, you seem to feel a hesitation from the car. Something is blown for sure? No, it's called fuel cut and it was built into your MR2 Turbo on purpose."

I dunno, maybe you've never experienced a fuel cut, but if you have I'm sure you'll agree it's pretty hard to mistake it for anything else - boost builds, peaks, (and if you're watching the gauge you'll see it happen over 10psi in a stock S2) extremely suddenly boost is shut off completely, entire car JERKS violently, strong engine braking and just a really shocking, disconcerting experience.

Tek_01 dangerous how? You mean from a safe driving point of view or dangerous to the car? In the R33 I've experienced probably 4 or 5 different fuel cuts at peak boost levels and it doesn't go into a limp mode, although I know it's capable of it and some other cars use it, in the MR2 after a FC it'll stay in 4th gear and limp along til you shut the car off and restart.

The FC in the R33 cuts the fuel off momentarily to halt short circuit the system instantly and more importantly the turbo which is possibly about to blow and yeah I'm sure it's probably pretty traumatic to your components to have them do that all of a sudden but if it's that or half your internals popping apart..heh

[Newy]

BUMP for finally a thread that is actually informative!!! This should be bookmarked in regards to 'overboosting' and the R&R explaination, its phenominal!

[shaunvlc]

okay, i drive an r33 gtst, found it does have a hks fcd. when i hit say 4000rpm it "feels" as if it misfires bad and you can even hear the popping coming from the exhaust. How can i fix this, it is a pain in the ass!

Car has 3 1/2" turbo back exhaust, fmic, 10psi boost, stock turbo

want a straight answer. dont really want to buy a new computer but.

Edited June 19, 2009 by shaunvlc

[SiR_RB]

i wanna know how people out there are running 12 - 13psi with the stock ecu, no piggy back computers and still make decent power figures like 190+ rwkw ?

why arnt all r33 gtst's for example, hitting R&R ?

[shaunvlc]

well im running 10psi and made 186kw at the wheels. I don't think the gains are too much when boosting above 10 psi. Certainly doubt there are any gains over running 12. (stock turbo)

[mad082]

i got 204kw out of the stock ecu and i was on the limit of R&R, but i was getting it like someone said above, a full cut of power for a split second, not just a slight loss of power. and when it happened in 2nd gear at about 60kmh at WOT, when it kicked back in it started to fry the rear tyres, LOL. i was checking to see if it was going to do it on the drive there so i could lower the boost if necessary... which it was. i was getting it on the drive on the way out to the dyno as i had it on 13psi and dropped it to 12psi and it was fine. afr's were all good though. around the 11's which isn't bad for a stock ecu. once i got a remapped ecu for it never had the issue again.

the first time i encountered it was the night i put my boost controller on. was slowly adjusting it small turns at a time and it didn't seem to be going up at all so i gave it a full turn and then boost went up to 15psi, got to about 3500rpm and it cut out and kicked back in just about giving me whiplash.

[mad082]

well im running 10psi and made 186kw at the wheels. I don't think the gains are too much when boosting above 10 psi. Certainly doubt there are any gains over running 12. (stock turbo)

again this is a bit of a misconception. a mate of mine put his 33 on the dyno (remapped ecu) and started off making about 200kw at 13psi and then kept winding the boost up and stopped at 16psi (didn't want to go any higher) and he was making 220kw. so while it might not be overly safe to go above 12psi, you will still make power.

i was also running my 33 at 14psi for about a year (with the remapped ecu) and never had an issue, and the power was definately more than at 11psi. wound it down 1 day and wound it up after about 20 mins because it felt so boring.

[psi]

power loss at 7psi is not likely to be an ECU issue. I would be checking (or doing a temp swap) of the AFM.

If you go and buy another AFM, dont get caught and buy a cheap chinese copy.. they dont work!

My old ECU was delivered with a speed cut inside the ecu. It also had some other things done before i bought it. It never suffered any of the issues you poor buggers are stuck with. I could run 15psi boost (killed some stock turbos doing it)! It blew truck loads of fuel like a diesel, but it did make power! I had trouble in wet weather, popping, splatters and general crap funning.. found a rub hole in the side of the AFM (old owner) where water was getting into the innner workings. Got another AFM and no more issues..

Find somebody with the same model skyline, throw them a case of beer, and spend a friday arvo swapping parts! Thats how I found my problem..!

happing boosting (when you get back to that!)

[mad082]

maybe try checking the ecu for fault codes, or get yourself a consult cable and drive around with someone watching the AFM voltage (or just datalog) to see if it is dropping out when it cuts out

[Branelly]

BUMP for finally a thread that is actually informative!!! This should be bookmarked in regards to 'overboosting' and the R&R explaination, its phenominal!

I second that, best topic ive read, all the info i needed.

[turbolag166]

check your AFM mate, could be letting voltage through too easy hence telling computer that there is more airflow than what is actually occuring

[JonnoHR31]

dont read too much of that info. most of it is extremely innacurate.

[666DAN]

Firstly, your ECU doesn't read your boost pressure. The boost sensor is only for your gauge on the dash. So its not your boost sensor thats the problem

The R34 has TWO sensors, one for the boost gauge, but the sensor in the middle of the firewall is the overboost sensor...when it reads 4.7v it will cut ignition dead.

[Flargh!]

The R34 has TWO sensors, one for the boost gauge, but the sensor in the middle of the firewall is the overboost sensor...when it reads 4.7v it will cut ignition dead.

Darn tootin! Cursed bloody thing!

[hg56]

Just wanting to bring this one up again, does anyone know if Rich & Retard can be disabled through an ECU remap? And if so, does anyone know which parameter needs to be altered to eliminate it? Could it be eliminated by replacing the R&R maps with the copies of the normal fuel/ignition maps? Or adjusting the TP limit parameter? Does anyone know the hex addresses for these or any parameters that can be altered to eliminate R&R? Thanks

Edited December 26, 2009 by hg56

[winstonusmc]

....Or adjusting the TP limit parameter? Does anyone know the hex addresses for these or any parameters that can be altered to eliminate R&R? Thanks

The TTP max is for the max pulse width that the computer will allow at any given RPM. This prevents overfueling at any given RPM. The AF_LIMIT in Rom Editor is the "boost cut" for a lot of the Nissan ECUs. It is the TP the ECU will shut down fuel, like a boost cut, but based on load. A lot of Chipped ECUs just max this value out to prevent any cut from happening and my RB26 ECU doesnt even have it. Chances are if you are hitting the fuel cut on a stock setup, it is time to up your MAF because the TP limit is usually set at where the MAF is getting to its limit.

BTW, this is a hella old thread.

[lachlanw]

never mind how old it is . i like how it took that long for someone to point out that a r34 does have a boost sensor for the ecu . and that nismoids only comment was a 6 word sarcastic question

gold

[GTScotT]

digging out the old.

Does anyone know how to prevent RnR without changing ECU or adding an inteceptor?

I have a zener that will cap the voltage to 4.7v but it still pulls SHITLOADS of timing running above 10psi at midrange type RPMs... the zener (an electronic diode type thing) wont help in this circumstance as the AFM is only reading 3.8v under 4000rpm, and still retarding.

Initially I had hoped it would be as simple as preventing it from seeing 5v, but it seems the ecu is smarter than that and has a table drawn up for voltage as per RPM

So, anyone know how to prevent RnR without an interceptor or reflash?

Churz in advance