Long time lurker, first time poster. Ive done some datalogging on my 7MGTE, and have noticed something that concerns me. I can get 10 pounds of boost at 30-50% throttle, and the stock ECU wants to maintain stoich in closed loop. I have trouble believing that this is good. Some notes on setup-Shimmed CT26 (Max 12 PSI), 3" from turbo back(Rabid Chimp Elbow), walblow 255, afpr set at 40 static(32 vacuum attatched), 2-1/2 inch hard pipes and cartech clone aftermarket intercooler. Car is currently tuned to satisfy VF, and will fuel cut at freezing temps. My datalogs show 14.7 afrs for up to 3 seconds at 10 psi at 40% throttle before open loop is triggered. WOT triggers open loop instantly, and AFRS fall off to 11ish. Ive bounced this off several people here and elsewhere, and consensus is that stock ECU at stock boost levels with restrictive piping was Designed to be WOT or nothing, therefore it cannot provide for safe part throttle boost with upgrades. Id love to hear any and all opinions on this. Mike
Part Throttle Boost Concerns
- Thread starter carfreek
- Start date
JJ will be the man to answer this, some of this was discussed in a thread about EGR. The EGR system is there to control knock in closed loop as well as to quench out nox for emissions.
I have often wondered if it would be best just to pull the O2 sensor and use an SAFC to tune your fuel from 1500rpm to redline. I'm sure there are 101 reasons not to do it but will see how bad I get arse raped for suggesting it.
I have often wondered if it would be best just to pull the O2 sensor and use an SAFC to tune your fuel from 1500rpm to redline. I'm sure there are 101 reasons not to do it but will see how bad I get arse raped for suggesting it.
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well i hope there's not an issue with this cause i can spool that at 20-25%thrtl w/o any problem at low RPM. I don't see why it would be an issue since the computer will still adjust to the amt of air going in with feul....just won't be the most efficient and power producing acceleration you could get...?
My concern is that 14.7 a/f at any length of time under 10 pounds of boost is bad for power and durability.
10 psi at part throttle isn't nearly the same as when you have the throttle plate open. The throttle body is limiting intake of air if it is not open.
You need to load the engine more. When you do, the frequency of the airflow meter will go up, and so does fuel delivery. Opening the TPS also increases fuel.
You need to load the engine more. When you do, the frequency of the airflow meter will go up, and so does fuel delivery. Opening the TPS also increases fuel.
You need the fat A:F due to high cylinder pressure @ WOT, not high intake manifold pressure. Don't worry about it unless you hear pinging (pretty easy to hear at part throttle).
The stock ECU does remain in closed loop under part throttle boost but I've never seen one do it past about 3 psi. If you have airflow controller I suspect it's been adjusted to offset some other problem. Could be a TPS issue too. Those are guesses though.
That said it's nothing to worry about as long as the engine isn't making more than 75% power at the time. In fact it could run even leaner than stoich all day long at 75% and nothing bad would happen as long as sufficient octane is available. That means at least one grade more than what the book calls for if EGR has been defeated.
That said it's nothing to worry about as long as the engine isn't making more than 75% power at the time. In fact it could run even leaner than stoich all day long at 75% and nothing bad would happen as long as sufficient octane is available. That means at least one grade more than what the book calls for if EGR has been defeated.
jetjock;938176 said:
I've been running mine like this on 93 octane with the stock ECU for just under 1 year now (Daily) with no problems what-so-ever. A couple cents more per gallon just isn't worth crying over, especially when you see your mileage increase from running leaner than stoich; while maintaining the ability to run higher boost levels.
No airflow controller, yet. I have been running premium since upping boost last year, and still have EGR. TPS has been set to tsrm spec with feeler gauges and a test harness I made from old wiring pieces. I daily drive this beast, and have 27k or so on it in last two years. Thanks to everyone who replied.jetjock;938176 said:
Nick M;938960 said:
Hey Nick, true that. Been dusting my mk3 off after a bit of a 2JZ induced vacation (haha) so I figured I'd see what was up over here.
Carfreek- Sounds like you may be one of the few who actually take care of your 7M, keep up the good work!