Yes another 22psi boost cut thread, but, a little different than the ones before.

Before I go back to stock and run the map to see the behavior, I want to get people to throw out thoughts.

A lot of people experienced 22psi boost cuts when running maps with 19psi, as the ecu would compensate with the heat and it would spike to 22.

I had that same issue, but now have received a map file running 16psi, yet it will indeed spike, but what I noticed now too is if rolling into the throttle, I can be wot and see 17psi, and then it slowly creeps steadily up to 22.

Boost creep is usually directly related to the waste gate, but with all these electronically controlled portions of our car now, I have a feeling it maybe something else.

Changed from my wmw dv to stock again with no change. Both diaphragms were okay. With a reflash of the same map, it will be cut free for anywhere between 50-150 miles.

I'm about to flash back to stock tomorrow and see if that will creep, if so then I probably have a bad solenoid for my waste gate.

Running stock dp, 2.5 inches from the dp back. Aem dry flow filter. Noise maker delete too.

Ideas?

 

Unlike our previous conversation...I don't think what you are describing is boost creep. If you are rolling into the throttle and see it rise like that, that is "normal" behavior, at least with every 56 I've seen. The stock tune will do it too. True boost creep would be you going WOT...reaching a target psi then having it creep up slowly.

I would think this all has to do with the damn overboost feature, which as far as I know is dictated by load/torque being requested. When you floor it and go WOT, you are maxing the torque requested and the car tries to overboost (really quickly), but then catches itself. As far as it doing it when you are rolling into it...I don't have an explanation for it other than it has to be load related (in the ECU). It really sucks how erratic boost can be on these cars. It's a shame you can't just throw a manual boost controller on it and run a target psi. Friends STi was set at 18psi....and it would run 18psi all day long, everytime.

The R56....floor it, and you never know what you're going to get. Is it going to be 18? Is it going to be 21-22? Or hell maybe a piston will break? You just never know

 

The wastegate is vacuum operated by an electronic solenoid, but the actual actuator is the standard mechanical diaphragm system.

If you still have issues with the stock map you can try looking at the vacuum lines for damage. Also if you have a vacuum pump, like a mighty-vac, you can put some vacuum to the actuator and check if it's opening all the way.

 

Noo, I roll into the throttle to get to WOT without triggering boost cut.. If I just slam the throttle it'll cut immediately. If I roll into the throttle ill watch boost build, I'll get to wot and it'll reach about 18, hold for a second, then continue to slowly climb about 1 psi per second

 

Yeah I think best thing to do it to go back to stock map and see how it behaves. But the fact that it will hold at 18 when first reflashing map for at least 50-150 miles

 

Interesting. So i would leave the map(BTW which map are you running?) and change the intake. Sounds funny, but we have had a few customers over the last year with the M7 intake cause boost cut problems. We tested this by installing the stock air box and the problem went away.

There are a few maps that can help fix this problem and compensate for whatever causes the intake to be the culprit. The problem is with two of the customers, i spent timing making about 10 total maps trying to fix it and it never really fixed it. One customer went to the stock intake the other went our ALTA intake.

Another thing is you could send me a log of it doing this. I could tell you right away what is going on. Part of the issue could be that the MAP sensors PSI limit is making things worse. For instance if the MAP sensor only reads 22 psi (also say that is 5v coming out of the sensor) typically the last .2V are not linear in their scaling. This means that 20psi may be 4.8V but when then sensor actually sees 5v its really 24psi. What i have found is targeting right around 19psi (Load numbers are around 205 at low RPM) that the spikes/cuts stop. If the map you are running as too much load being targeted that could be the issue. You should try the stage 1 mapping, or even Stage 1 91 octane. That of course is if you have an AP. If you don't have an AccessPORT, then i guess i just told your tuner how to fix it

Email me a log if you have an AP, and i will see what is going on!

 

I was thinking this might be the issue if the problem went away with the stock map.I remember many of the early AP maps caused this, but it hasn't been an issue lately, so I didn't put much thought into it. Any case it's a good point to bring up. Can't say for sure if the other tuner's maps have fixed this or not, but i know it was a problem for some of them too.

 

That is why I went to separate boost control. Tial gate, greddy boost controller. The computers overboost nonsense caused a lot of crap.

@Alta Is it possible to make a "map" certain fault codes deleted? I often throw a charge pressure min and max code (seperate times) due to the turbo and cams which puts car into limp. This only happens when driving the car civil. If i beat the snot out of it it never throws a code. I guess she's a glutton for punishment LOL!

 

Is this what happened to me today? It was cool this morning and I wanted to run the car a bit. I have an 07 MCS auto. On the interstate, using the manual shifters, I downshifted from 6th to 4th at around 80 mph just to see how far the car would pull, at around 100, it sounded like the diverter valve was hung open, and the boost cut out. I eased it back down, then did it again. Pulled hard to 100, then cut. Got off the interstate and in the low gears, no issues. It pulled like crazy, and the diverter valve worked like it should. I am running AP stg 2 tune, with a DDM works race intake no ram and all the mods in my sig. Sorry so long, but What the hell is going on with my boost?

 

i had the same problem starting off. I would mash it in 1st and but would cut off at a 1# all the way to 3rd gear. Then at 3rd i would get full boost.17-18#. It still does this once and a while.

 

I have exactly the same issue. With the higher gears (3rd and above) rapid application of the throttle, especially from ~3k rpm or so, will cause the boost to spike then dump. It is very annoying. Using the reset option on the AP helps for a while as you mentioned. I am totally stock with the AP stage 1 92 octane map. I may try the 91 octane map to see if it helps a bit. I have contacted ALTA about this and the fluctuating idle several days ago and they are working on it (at least the idle problem, hopefully the boost spike as well).

Out of curiosity, how close to sea level are you?

-JL

 

190 ft :-p

 

My theory is a map tuned for an "average" altitude, say 600 feet above sea level, is too aggressive for those at lower altitudes. Since these are generic maps, maybe it's a contributor to the issue. Anyway, I'm flashed back to stock so I can bring it to the dealer on Monday for an unrelated issue (possible failing water pump). I'll try to get some logs after that.

-JL

 

Hi,

I believe the ECU works off absolute manifold pressure (MAP), so atmospheric pressure is irrelevant. The ECU sets a target MAP. The absolute manifold pressure is atmospheric pressure + boost. Therefore people at high altitudes will see more "boost" as there atmospheric pressure is lower. However, the car is running the same manifold pressure, which is the important number.

 

it would be manifold +14.78 psig!

 

Actually not quite true. The turbo has to be driven harder to produce the same boost (manifold pressure) with lower density air at higher altitudes. Remember the turbo is working on a pressure ratio.

My theory above is just a guess however. I'm sure the ECU has ways to compensate for altutude. I'm just speculating that aftermarket tunes, with only some of the maps in the ECU fully understood and modified, may not be able to fully take advantage of things like atmospheric density correction.

-JL

 

Mine is dyno tuned at my altitude

 

Yes true, but that doesn't disprove what robbo said. The turbo will work harder, but the pressures will remain the same

 

Well there goes my theory...