The other day i decided to crank up the boost a llittle to see the diference. Before i was spiking to 21.5-22 and holding 20-19 to redline. Now it spikes to 23.5-24 and holds 21-20 towards redline then to 19.5. What a huge diference!! At WOT i pulls so hard and clean all the way to 7500K. I am on 93 oct, should i be ok? I have a 10.9 AFR's right now sometimes 10.7 so i felt the diference since im running a little better and not so rich.What do u guys think?

 

Not good at all. First off, anything below 11.5 is on the rich side...below 11 is quite rich. You can't run that much boost on 93oct without timing being pulled UNLESS you are running really rich, but that defeats the purpose of running more boost. This is even moreso true in really hot/humid weather like you experience on a daily basis. You should be running 20-21psi with an 11.3-11.5 AFR daily while maintaining a solid, linear timing advance with a peak of ~20 degrees. In the winter, you can run a little more boost on the same AFRs.

 

I am running really rich, the car does not pull timing at all. I need to get a SAFC to lean it out. My afrs on the dyno where 10.9 sometimes 10.7 so u can imagine how rich the car is.

 

You see that often with flashes, because the flash tuners have to give you a tune that can work all year 'round in all weather conditions. An S-AFC on top of the flash will allow you to keep it tuned well at all times despite weather changes.

Anyway, you don't want to be running that much boost on pump gas. People run that with alky kits and race gas...

 

Ok, i will turn it down. How much to be safe? Highest?

 

i will disagree alittle with Warrtalon you can hit peak of 23-24 but if it drops fast and you maintain a boost of 20-21 then this is ok, watch for knock and look at your timing issues. peak boost is not really a problem since it drops off. now if your trying to run 23-24 and maintain that boost he is right you should use race fuel because when you get your AFR close it will knock and then your timing is pulled. of course every car is different and one may hold a little more boost than another with timing changes. it sounds like you want to maybe start with your boost holding good at 20psi with a tiny bit of creep. then adjust your AFR to a safe range, i do like his 11.3-11.5 range then try and keep your timing in the 20 range. if this runs good then try and turn the boost up by 1 and see if you can maintain your other parameters. as usual this is an art due the differences in cars mods and how weather is in your area. 1 really cold dry day will make you thing you just found 30hp. dont you notice when you first drive the car in the morning it seems extra peppy and the boost is quick to spool.I am in the middle of ECU+ tuning looking at everyones changes just proves each car is different in what likes.

 

Maybe a 22psi spike in 3rd that holds at 20.5-21 to redline followed by a 19psi taper at the end. That's my suggestion, although many will tell you they run 23psi daily on 93 pump with no issues. I just don't buy it, since I've seen the effect with 10 different Evos dyno'ing on the same hot summer day and all having pulled timing over 21psi on 93oct...

 

I don't think you're disagreeing with me at all. I concur with everything you said, ESPECIALLY that each car is different and should be tuned specifically to itself, vice what others do/say. The whole boost spike thing is iffy, because it depends on if you slowly roll into full boost or if you downshift and nail the boost from 5500 rpm or so. Nailing it immediately with a downshift at higher rpm starts you off at the tapered boost level without a spike, whereas a slow roll-on spikes higher only temporarily. I still think a 23-24 spike is not good. I can physically feel the loss in power when I have my boost set too high, but then again I don't have a flash like him that keeps his timing at 7-8 in the mid-range...mine falls to 0 on the stock timing maps.

 

ok I agree,


what do you think about the accuracy of the non digital boost gauges. i am currently talking with someone who just did the GM maf and his boost reading are like 20 spike with it dropping to 16 each time 2-4th very consistant. his boost gauge is reading 20 psi but drops to 19. now who do you trust. is the boost gauge just not good enough. should you let more spike occur and only follow hold boost. i know some have had better luck with aftermarket BOV and other MBC ,. mine seems to hold pretty well. if ( boost gauge is accurate.)
your thoughts.

 

I think it's all relative really. Boost gauges are probably not very accurate, but as long as you know what works on YOUR boost gauge, then you're fine. In other words, if you go to the dyno and mess around until you get the most power with the most boost and the best corresponding afr/timing curves, then it doesn't really matter what your ACTUAL boost is, but moreso what your boost gauge reads, as long as it's repeatable...

 

my thoughts are this maybe the reason some say they can boost to 23 or hold 22-23 when if we had better monitoring it maybe they are at 20 instead. but yes , as long as you tune to the cars abilities the gauge is only helpful to tell you up or down values on the amount of boost your seeing.

Off to Tune somemore .

 

Heh...welcome to my world. I have a Defi D mech. boost gauge, an AEM MAP sensor and a Blitz ebc. All of them provide an independent way to measure boost and all of them read diferently. The mech. boost gauge reads the highest, then the ebc and the AEM reads the lowest. There is about a 1 psi difference between each. I choose to believe the middle one and recalibrated my AEM MAP to read 1 psi higher than the AEM calibration. It doesn't make much difference what the boost is as long as the car doesn't knock. It's like timing...keep advancing until you bump into knock and then back off a little.