Hi,

I've recently replaced my exhaust on the Evo IX and now its suffering from overboost subsquenetly fuel cutting. My plan is to reduce the boost until I can spend time going through a full & proper remap. My other option which (of course) I dont want to simply increase my boost limit cut off for fear of damage.

I've looked into the tuning guide by NJ1266 and whilst I've picked up some of the fundamentals but unfortunately cant understand how I'd be able to reduce peak boost (without the use of a MBC / EBC).

Any help would be greatly appreciated.

Cheers
CP

 

You could just lower the boost adder. (which will essentially lower all boost target loads)

If you are not knocking, why not just that amount of boost? How high is your boost? Are you tuned at all?

 

Sorry 'boost adder'???

I remember the boost hitting 1.6+ but I can't be 100% sure of the actual figure (I was planning on getting out and full data readings back on Evoscan but heavy rain at the weekend made it seem unwise).

The car hasn't been tuned at all map wise however the only changes have been the HKS Downpipe, Sports Cat and exhaust & Apexi POD airfilter.
However I didn't get this issue until the exhaust was fitted.

Thanks for the help.
CP

 

If you havn't tuned anyhing on the car and only added and exhaust, you shouldn't be seeing any overboost at all. You may see a slight increase in boost, but not over boost. Check your vacuum lines. A pinched wastegate line could cause all kinds of issues. Also, if you are still using the stock solonoid, it is possible on your install you damaged a line.

Check the mechanical stuff before you dive into the ECU.

 

I thought I'd checked everything however I'll do it again just to make sure.

Thanks

 

Thats not terribly out of the ordinary boost. 1.6 bar ~~ 23 psi

I'm pretty sure you are OK (that is a very normal level of boost), but it can't hurt to check over the lines and such.

I personally disagree that the boost limit tables should be used. Their method of action is very abrupt and hard on the engine and driveline in my eyes (god forbid if they intervene when the car isn't pointed in a straight line with nothing around it).

I'm going to stick with "if you aren't knocking don't sweat it". With a more free flowing exhaust it is now easier for your turbo to work at those boost levels without knocking.

 

+1

 

yeah it is normal to hit the fuel cut with your mods especially if it is a bit cold outside. just increase the boost cut load a little like 10-20 across the board.
But you should get a tune to optimize your tune with your current mods. since you have evoscan log, after adding to the boost cut table do some wot runs and make sure you are not getting high knock counts. 1-2 counts is typically acceptable.

 

Hi lads, back again.

For the past couple of weeks - I haven't had a problems at all until tonight when I was logging some power-runs to check for knock etc.

First run in 3rd gear, I didn't have a problem (see run1-nofuelcut.csv in the attached zip).

The second run, got to around 6krpm and it slaps on the boost/fuel cut but after looking at the logs I can't see what the hell caused it.

Boost didnt exceed 21psi
Load didnt exceed 230%
Injectors dont seem to be maxing out.

Does anyone have any idea???

Cheers
CP

 

I assume your rom is stock?

Most of the roms I've looked at have a control boost offset of 80. Furthermore they seem to use 159 up to 5-6k rpm where it drops to like 130'ish then down to like 110.

So essentially once you go over desired boost you get 1 second to get back down to normal then or it initiates fuel cut. Likely your problem is somewhere around 5k rpm but can't really know without seeing a rom.

I really don't like your wideband it looks scary lean for regular gas.

Other than that just simply raising the desired engine load from like 5k rpm to redline would also fix your problem. If you feel like lowering boost lower the wastegate values in the max wastegate duty tables from 5k to redline.

 

Prety much so, I'm on a stock 88570008 (with Immobiliser & Rear O2 disabled).
I've linked the ROM - Download here

I'm in the UK and run on nothing less than V-Power from Shell (99ron). So I'm hoping it isn't that bad.


If its only a matter of raising desired engine load by a few % then I guess its okay but I'd have liked to know whats causing it.

Thanks again.

 

The fuel shouldn't be the issue of why its running so lean. I get the feeling perhaps your wideband just isn't caliberated.

Looking at your rom some values confuse me seems like your cutting out alot of desired engine load all over the place. Is the goal to run the car at some certain psi or something?

I also noticed that you have very low values in the wastegate duty section almost like your are trying to lower the boost there too.

Sugguestions:
Calibrate the wideband or add fuel to your map. I noticed your injector scaling is at 542 for some reason, i distinctly remember stock being 513 which could account for the leaner runs perhaps this is normal in an out of state evo?

Turbo error correction table, since your trying to limit boost having it add boost for you is silly. Change the top 5 rows in to correction side (right hand) to 0. This way it wont be trying to add wastegate duty when your turbo is spooling up nor will it if you don't reach your target boost via wastegate duty %.

Desired engine load, there is no reason to limit 2500rpm to just 188 load by putting in 108 into the table. I'd have kept the max values 159 up to about 4500 rpm on your rom.

If you can't sort all this out perhaps its time for an email tune? Even if you plan to tune the car afterwords its good to see how a tuner would change the rom in order to gain performance.

 

Cheers mate - I do appreciate your help on this.

From my logs before the runs that I've posted the AFR does appear to be near to the right levels but I'll do a clean air calibration later to double check this.


Quite strange since the I haven't made any changes to any values (except the immob & rear 02). I've also had a look at a stock 89280002 rom which has very similiar values for all of the above and the same 542 value for injector scalaing.

 

I'm thinking your car should be like 11.5 AFR for what would be considered around 93-94 octane here PON not RON. Try the 513 scaling on the car I bet it idles fine but the fuel in the higher range should drop down to more reasonable AFR numbers.

 

Defo not a stock rom.

I can send you the stock roms to compare if you like (FQ340 & FQ360)

Timing looks close-ish to a stock FQ340 though.

Curious why you've disabled the rear O2?