[Hurrakaine]

According to most people the stock ecu pulls timing above 18 psi. I can not for the life of me figure out how the ecu can see 18 pounds of boost when you have a bcc installed. As far as I understand the bcc alters the signal to the ecu so it does not see more then 14.7 or whatever so this makes me so confused. Also I once read well recently I have been reading through the archives from 2002 or whatever and I am up to 2007 at the moment but someone stated that the obd 2 ecu does not pull timing the way that the obd 1 ecu does. I have only read that once does anyone know if its true?

I am at work typing from my blackberry so please excuse the sentence structure and crap.

 

[AlxRSPTT]

I don't think anyone has told you it pulls timing based on boost, but most cars on pump gas will have timing pulled by the ECU around 17-18 lbs. It has nothing to do with the ECU seeing boost, but the ECU seeing knock. If you put race gas in and push it past 18lbs, guess what, it's not going to pull timing. It has no correlation with manifold pressure.

Alex

 

[cwtt]

Think about it. The car is metering the volume of"air" via the MAF (not psi). The BCC only clamps the turbo pressure sensor. On a US spec car the TPS does nothing for fuel/timing. That is what the MAF is for.

(Talking about US spec cars obviously)

 

[cwtt]

Oh and to add some more to what you were saying, the stock ecu will pull timing when running pump gas especially at 18psi. (Talking about stock turbos here) People have data logged this to prove it.
Now the difference between obd1 and obd2 is that the obd2 ecu seems to give back timing faster than the obd1 ecu does. I noticed when I switched to obd2 a long time ago, that the car recognized that I had just put race gas in and would immediately start adding timing. The obd1 ecu is just a little slower when doing this.

It is funny how people try to run high amounts of boost on pump gas and they say "well I dont feel it pulling timing." When in reality they are too ignorant to actually do a data log and actually see how much timing really is being pulled.

 

[Hurrakaine]

Ok than makes sense but how do the guys using the stock ecu and a piggy back such as the vpc/gcc, Safc or the map ecu guys never complain about timing being pulled when they are making 700 hp. Obviously they are running more then 18 psi and using the factory knock sensor? If so much detonation is happening on stock twins making 400 whp what happening when the same car is making twice that?

 

[earl3]

^ Because they're burning race gas and thus there is little to no knock sensor activity. If they tried to make 700+ on straight pump with the stock ECU/piggy back they would toast a motor in no time.

 

[AlxRSPTT]

^Exactly, I thought I said that in the first reply though... (not directed towards you Earl)

Alex

 

[Hurrakaine]

Well race gas does make some sense. But I am still not so convinced. If I was running 18 psi on the stock twins my air fuel is somewhere between 9 and 10 to one. If I am running 22 pounds or so my air fuel is still around 10 to 1. With the car running so rich unless I did like 13 fifth gear pulls and my intake and egt temps really climbed I don't see any reason why the car would be detonating one bit or enough to make the ecu pull timing. As far as I understand the ecu has three maps to choose from. I don't know if that's true,I also never saw anyone data log the stock ecu and compare timing from a pull on lower boost and one from higher boost either. I personally think the whole 18 psi and timing thing is something that has been said over the years and everyone just simply takes it for bible. If I saw actual proof then I would be quick to change my mind. I respect everyones opinions no doubt but in the end a opinion is an opinion until proven true of false.

 

[tissimo]

Well race gas does make some sense. But I am still not so convinced. If I was running 18 psi on the stock twins my air fuel is somewhere between 9 and 10 to one. If I am running 22 pounds or so my air fuel is still around 10 to 1. With the car running so rich unless I did like 13 fifth gear pulls and my intake and egt temps really climbed I don't see any reason why the car would be detonating one bit or enough to make the ecu pull timing. As far as I understand the ecu has three maps to choose from. I don't know if that's true,I also never saw anyone data log the stock ecu and compare timing from a pull on lower boost and one from higher boost either. I personally think the whole 18 psi and timing thing is something that has been said over the years and everyone just simply takes it for bible. If I saw actual proof then I would be quick to change my mind. I respect everyones opinions no doubt but in the end a opinion is an opinion until proven true of false.

Hook up a obd2 scanner to your car and look at the timing figures.

Its not that the boost is doing it. The turbines are so restrictive on the stock turbos that they have a lot of back pressure. Probably 25-30 psi at 18-22 psi of boost (if not more). That leaves a lot of Hot exhaust gasses in the combustion chamber heating up the air charge (even if its ambient temp from the best intercooler). That heated air in the combustion temps and the low octane rating of the pump gas doesn't allow the high cylinder pressures with advanced timing (or it knocks) so it pulls timing out to get everyything in check.

 

[Hurrakaine]

Thanks lol that makes plenty of sense in my book!!! I appreciate the response.





Steve

 

[Nick 95 6sp]

Well race gas does make some sense. But I am still not so convinced. If I was running 18 psi on the stock twins my air fuel is somewhere between 9 and 10 to one. If I am running 22 pounds or so my air fuel is still around 10 to 1. With the car running so rich unless I did like 13 fifth gear pulls and my intake and egt temps really climbed I don't see any reason why the car would be detonating one bit or enough to make the ecu pull timing. As far as I understand the ecu has three maps to choose from. I don't know if that's true,I also never saw anyone data log the stock ecu and compare timing from a pull on lower boost and one from higher boost either. I personally think the whole 18 psi and timing thing is something that has been said over the years and everyone just simply takes it for bible. If I saw actual proof then I would be quick to change my mind. I respect everyones opinions no doubt but in the end a opinion is an opinion until proven true of false.

just to add to another comment, I'm also not sure you understand that no matter how perfect or rich your a/f is, the motor will still knock if you exceed the capability of the octane to support whatever boost you are running.

 

[Hurrakaine]

I wasn't aware of that. Thanks Nick.