darek_u

I think these AFRs are ok, although a little on a rich side. I'm not an expert so your input would be much appreciated.
Car: 1988 Turbo S, stock except for Rogue A tune mated with Rogue DME and LR Clubgate. Stock injectors, vacuum system all new (no leaks), engine fully rebuild with new rings, head etc. etc. The only mod is different KLR chip with max boost 15PSI. Pump gasoline (95 oct as per Euro standards), car is driven on the street, no plans for racing, it is strictly weekend car.
Here are the screen shots from Rogue Logger, you can see hard pull on 3rd and 4th gear, all 3 from one run, just different reference points shown.





What I can tell is that it is a little on a rich side, boost drops down slightly as revs go up (from 15 'ish to 13 'ish PSI) and full boost is reached at around 3500. Little bit too high, right? Otherwise car pulls strong and feels very healthy. What do you think?

darek_u

Soooo should I worry about something or just drive it as is? This rich condition worries me a bit, I'm not an expert wen it comes to logs etc.

Droops83

Well, that is a bit too rich in the full load/higher RPM area, but you are not going to hurt anything in the short term on a street engine if you are not often in that load/RPM range. If it were a track car, it would be a more immediate concern due to fuel washing down the cylinder bores, etc.

What sort of fuel pressure regulator are you running, and have you checked the fuel pressure?

I know the Rogue stuff is harder to find now, but they did offer a piggyback tuner device to allow fine-tuning of the maps on your DME chip. Not sure if it works with A-Tune, but might be worth looking into. Others on this forum will be able to help you more as I have no experience with this setup (I have VEMS standalone engine management on my 951).

darek_u

I have Bosch 3 bar FPR (gold zinc color, not black), I can read the number as it is obviously hidden underneath the regulator and I would have to remove it from the rail to read it... I checked the pressure in the rail and it reads 3-3.1 bar with vacuum on but my gauge is just a small gauge from plumbing shop, not sure how accurate it is. FQS is set to #2 (-3% fuel globally). I did one run with FQS set to 0 and it was even more rich under load. I'm leaning towards excessive fuel pressure, probably in my case 2.9bar would be perfect? I know that Lindsey is selling adjustable FPR but I'm not sure if they are open nowadays and ship overseas due to Covid?
Anyway, I don't floor it on the street so I think I can live with it for some time.

Scott H

You want to check fuel pressure with the vacuum/boost line off the FPR. IIRC the Bosch 3bars are notorious for actually being a bit more than 3bar. If you're at 3.0-3.1bar with vacuum going to it then it's probably a bit higher without.

eman930

YEs, You are getting too rich, You want it to sit at 12/12.5 under full load for best power.

darek_u

I just purchased adjustable FPR from Dave Lindsey, this should solve the problem hopefully. So you are saying 12.5 under full boost? I was thinking closer to 11.5 but Im not an expert...

eman930

the problem with using a FPR to correct your fuel trims, is you cant target the specific area in the RPM where its rich or lean, adjusting the FPR will adjust air fuel ratio across the entire RPM range, SO yes it may fix your rich area but in term make other areas lean. The proper way to fix your fuel curve is with a tuner or new map on a chip. 11.5 is safer, but 12-12.5 is where max power will be.

darek_u

FPR is bought anyway so I'll go that route but very carefully - fine tune to 2.9'ish and keep checking with logger. Looking at the curve I don't think it will be too lean in other areas. Closed loop is not a problem as lambda will keep everything in order.

fejjj

I would aim for 11.7 at WOT. That way you have a prudent safety margin.

Droops83

I 100% agree with you that attempting to correct an AFR issue with an adjustable FPR is a bad idea!

However, there is actually not a huge difference in power with that small of a difference in AFR:

shortyboy

I would also look into ignition system. Plugs/wires/cap/rotor. The weak ignition in higher rpms would also be the reason why your running rich. Weaker spark means, unburnt fuel.

Droops83

No, that is incorrect, and like the ideal AFR for horsepower is another internet myth. Whether wideband or narrowband, an oxygen sensor only reacts to oxygen in the exhaust stream or a lack thereof when compared to reference air outside of the exhaust.

A misfire as a result of an ignition issue will show up as a "lean" reading (usually ~16-18:1 with gasoline), which may seem counterintuitive, but this is because the incomplete combustion results in excess, unused oxygen in the air/fuel mixture.

darek_u

I have no vacuum leaks, new ignition system (cap, rotor, wires), injectors cleaned and flow matched, new FPR, new sensors all around. Harness is brand new (I made one), new DME (Rogue), rebuild turbo, crossover and headers checked for leaks and welded where necessary. Engine have 3.5kkm after full rebuild (honing with AN30, rings, bearings, all new seals etc.) I generally run out of ideas where to look for my rich condition, the only thing I can see that is out of given parameters is fuel pressure. I fully agree that best would be check the tune cell by cell and adjust as needed but I have A Tune. As you probably know Joshua locked (coded) bin file and there is no way to adjust the maps with Tuner Pro or other software. Unless I cannot read it, highly possible as I'm not an expert.
I'll try to dial down the fuel pressure to 2.9-3.0 and see what happens unless somebody can point me in other direction that seems to be more proper...