My friends evo is hitting the fuel cut at around 18-20 psi, what psi is the stock fuelcut at? i thought a stock evo will boost to about 21. it has a mbc, cattless turbo back exhaust, and k&n intake on it, its a 05 evo 8, we turned the boost controler to about 17 and it will still do it. He just bought it used and we are not sure if its tuned or not. can u guys help out. we will load the turbo up and around forth gear it will boost then hit about 19-20 and fuel cut and backfire.

 

A. check the spark plugs and there gap and B. upgrade the fuel pump
stock the evos will spike 19psi and hold 16psi...any questions pm me

 

I'm sorry, do you actually work on your own Evo? Fuel pump has nothing to do with boost cut, and neither does the plug gap (blowing out spark results in a misfire not a fuel cut condition). Upgrading the pump down the road is not a bad idea, but it's also not the cause of his problem.

It's not the psi it hits but the load % that is the cause of boost cut. During colder weather the air is denser so load % is higher than warmer months, even at the same psi levels. The test pipe is probably what threw him over the edge and into that boost cut range. FYI, stock boost cut load % is actually pretty low...around 225%. Either raise the boost cut percentage via EcuFlash or lower the boost pressure to the point where he doesn't hit the cut. Regardless if he runs at 17psi at that fine line of boost cut or 19psi with the stock cat on and no boost cut, the car still makes (roughly) the same amount of power. People need to stop thinking in static terms of pressure and start thinking a little more linearly of load percentage. For most everyone else I guess there's mastercard.

 

yes i do, and well put info. i read the thread wrong
also just my smal 2cents. u need fuel to make more boost. if he is fuel cutting from upping the boost it needs more fuel...could be wrong but just my two cents...u r 100% right tho on the load %

 

I knew about that dence air and it causing it to hit fuelcut, but thanks ill just lower it more, and when it gets warmer raise it, the car is originally from florida so i think it was tuned for down there. within the week we are lowering it with swift springs and putting a welbro 255in, i was just making sure it was fine to run it around 16 and wont loose power at all. thanks guys i love the quick responces and the forum in general

 

Fuel cut and backfire? Hmm that's weird.

I would log during the fuel cut. Look to see the load percentage. Its colder and denser out.


*edit: just read slo crx1 post

 

well just turned the boost down to around 16-17 psi so it doesnt hit fuel cut, we will go to ams sometime soon so they can check if it was tuned. thanks guys

 

If still on the stock ecu you could be hitting boost cut. The new mods can cause you to hit a high load which is what boost cut is based on. Just as slocrx was saying.

 

There's an even better chance that if he bought it used it was either poorly tuned or the mods that the previous owner had on it were sold which will cause the car to react much differently than it should.

Instead of having AMS just take a look at the tune I'd just get it tuned.

 

well there wernt any other mods on it because the stock exhaust manifold and turbo wernt messed with at all, you can notice from the layer of rust on the manifold and if it was tuned it would be down in the warm climate of florida. I turned the boost down to 16 and it runs perfect no problems what so ever. Once he gets a evo 9 turbo and cams hes gonna get it retuned. but still not sure if its tuned or not (pulls and run like it has been with the mods). I thought fuel cut is basiclly boost cut because its cutting the fuel so it doesnt overboost? correct me if im wrong

 

boost cut drops you to wastegate pressure instantly or at least it feels like it. I hit it at around 25 psi when i changed roms. I had forgotten to fix the boost cut to a higher load value. It was so violent my knee almost hit the dash. Fuel cut I would get all the time when I would get a p0300 code on the highway and my afr would sky rocket to 30:1.

 

1. check the plugs
2. get a tune
3. nuff said, "Sho Nuff!!!"

 

im pretty sure its already tune and its running perfect now no problems at 16-17 psi

 

Boost limit cut is a fuel cut, I've accidentally logged it before and when you hit the max load % for the set time limit it actually cuts fuel, not drop you to wastegate pressure. Your condition I've also logged as well and is caused by the p0300 code as it changes from a pending to a current code and your SES light pops on. Once the code becomes current your afr's will change a bit also from what they're tuned to be, as will your throttle crossover point.

 

not sure if its throwing a code when it happens because the cel is on right now cause it needs a new o2 but after that and the o2 fix but for right now its running pretty prime