Turbo Tuning Question

[robwright]

Guys I mentioned this briefly on another thread but didn't want to hijack it. I have just got into analysing my AFRs recently so I can get to know the car more with a view to what I can do in the future. I am a bit concerned about my WOT AFR. I have set my idle AFR at 14.2, which equates to 0.6% CO and my cruising AFRs are around 14.7 at 40 mph and 14.2 at 80 mph. When on power but not on WOT at low to middle revs my AFR is in the low 12s. All good so far. However when I floor it and start reaching the higher revs my AFR is dipping below 11 to the 10.5s -10.9s. This of course puts me at risk of borewash due to the amount of fuel being delivered. The car is running 18 psi on a very new K26/6 turbo and standard injectors. I have a Tial DPW and 3 bar FPR. The chips are max 951 chips from Russel Berry who chips for Lynsey Racing. These were arranged by Vic Timpauer of Pauer Tuning, from whom I bought the Tial. So my question to the rest of you tuning guys is short of a custom map from the dyno what other options do I have? I have considered fitting a K&N panel filter to try and increase the air volume into the engine but I am not convinced that this is the answer. All help will be gratefully received as always guys.

 

[Lowtimer]

I'm guessing, but I wonder if the chipset anticipated a bit more top-end throughput which you would get from a 26/8 turbocharger. With a 26/6 it seems implausible that it can be delivering 18 lb of boost all the way to the top of the rev range, even if it does in the mid-range.

 

[robwright]

You are possibly correct about the boost lowtimer but you know how difficult it is to monitor these things without the luxury of a dyno. The AFRs I can see failry easily and quickly but as you know it can take a short while for boost to start tailing off and it can be quite difficult to find that much cop free road lol. I was considering popping down to Promax one weekend in the new year to discuss it with them. Perhaps they could reprogram my existing eprom with one of their maps. I don't know if that is a service that they would provide?

 

[Lowtimer]

I dunno, but Andy always seems very helpful as well as being very smart and knowledgeable. I don't know whether they use different maps for 26/6 and 26/8 cars,but I would not be surprised if they did.

 

[Frenchy]

Rob, do the chips not have DIP switches for different fuel maps, better to be too rich than lean though..........keep off full boost []

 

[robwright]

Mark you have just reminded me I was going to ask you about these DIP switches. I don't remember seeing them when I had the ECU open to fit the new chips. Where are they to be found? What is the binary code for the chips? If I have them and I can find them I am willing to give it a try. Staying off the full boost isn't too difficult this time of year. You know how much greasy roads and a tuned turbo don't make good bed fellows. Having said that though it is a bit frustarting/annoying as I am constantly mindful of the AFR now and constantly holding back. Makes you enjoy the car just a tiny bit less I think []

 

[TTM]

You said you adjusted AFR to be 14.2 on idle - how did you proceed?

Russel Berry chips should be spot on without need for further adjustments.

 

[robwright]

There is a mixture screw on the front right of the turbo AFM that only affects the off map mixture. The manual quotes to set the CO at 0.6%, which a quick internet search of AFR to CO conversion comes out at about 14.23. I agree with the statement about the chips. I was confident they had good pedigree? Unless my AFR is completely wrong? It is less than two years old and doesn't get hammered so why would it be? If there was an exhaust leak it would be reading lean not rich.

 

[944Turbo]

Dip switch is probably the rotary accessable from the outside, usually in conjunction with the various region coding plug links in the loom.

Boost leaks and other sensor faults can affect the mixture.

My ISV had a big leak under boost, the connectors to the intercoolers crack, my heater valve at the rear of the engine was leaking. Any air that has been measured on the way in and escapes will create rich running.

Arnworx do a pipe end that allows you to pressure the inlet system with a compressor (gently!) - then its just run round with soapy water spray or listening carefully.

Tony

 

[TTM]

ORIGINAL: robwright
There is a mixture screw on the front right of the turbo AFM that only affects the off map mixture. The manual quotes to set the CO at 0.6%, which a quick internet search of AFR to CO conversion comes out at about 14.23. I agree with the statement about the chips. I was confident they had good pedigree? Unless my AFR is completely wrong? It is less than two years old and doesn't get hammered so why would it be? If there was an exhaust leak it would be reading lean not rich.

If your engine is in good condition with everything working as it should (no vacuum leak, etc), checking the AFR only should be enough, as you should always get the right level of CO when combustion is fine.

What kind of lambda sensor do you use and where is it mounted?

Try to adjust the screw on the AFM to get an AFR of flat 14.7 at tickover when the engine is fully warmed up.
I suppose you still run standard injectors, so make sure you have the FQS set to position #0 (fully anti clockwise) and let us know of your AFR numbers by then and of the colour of your spark plugs.

When I was running standard mechanicals on my '90 250, it always went through the MOT's emission test with flying colour, either with some old Guru Racing or MAXhp chips.

 

[robwright]

I use the innovate LC1, which is mounted in the downpipe after the turbo. I am still running standard injectors as I don't have the budget for an upgrade to 55lb ones at the minute. Damn you Christmas [] I need to know more about setting the FQs and coding plug. Does anyone have pictures or instructions or a reference to it in the workshop manual? I am already inventing a dveice in my head that I can conncet to the J boot after the AFM which will allow me to pressurise the system with a couple of PSI of air to see if I can detect any leaks. They can be vary hard to find with the engine running. Not sure if I will get the opportunity for a good run this side of Crimbo though []

 

[944Turbo]

I use the turbo output pipe (well actually I have a spare which is easier than getting it off the turbo) and have a copper 'end stop' (like a aerosol can lid) with a tyre valve mounted in it. I thought it was from Arnnworx but they don't seem to have them anymore. Looking at their site also reminded me I had a pretty big leak from the throttle body as well and that their repair kits don't really fit that well.

This thread is also reminding me why i wanted a V8 - easy reliable power with no messing about

 

[Diver944]

The Max951 chips have a very good reputation so as long as you are sure you have the set for K26/6 and not for the K26/8 then I would guess you either have a boost leak somewhere or your setup is not holding 18psi long enough for what the chips are expecting. The quickest and easiest way to diagnose this is to get a Rolling Road Dyno chart that measures your boost and AFR as well as the power figures. This chart is from Scott Woods car on www.cannell.co.uk and have pretty much identical modifications on a K26/6 Turbo, notice how the boost has tailed off below 12psi after 5500rpm

 

[944Turbo]

If you are getting 18psi with a boost leak that also works the turbo harder which pushes it further out of its efficiency range. I had a gradual leak develop which I had compensated for with the boost controller, when I fixed it, boost jumped to 24psi which when reduced to 18psi felt significantly better than the previous 18psi with the leak (K27/8 turbo)
Tony

 

[Frenchy]

Drilling and tapping a thread to take a fitting in the inlet manifold near to the inlet boot to avoid strip down would then allow you to introduce pressure with an instrument (Druck or similar) once pressure has been built leaks would be apparent.
Got me thinking now !
Leaky rings won't help though []

 

[944Turbo]

Wont that leak out through the turbo?

 

[George Elliott]

I think it will
George
944t

 

[robwright]

Sorry it's been a while since I revisited this been I just haven't had the time to look into it until today. Went into work today and fashioned a device to pressurise my intake system. Luckily enough I had an old AFM that I could bastardise an air line fitting onto and pressurised it up to 5 psi. Please see below. All patents applied for.

The upshot was that my J Boot had a tear in it causing a boost leak. I bandaged the J Boot, which will do until the ever reliable Alasdair can dig me out a replacement.

After leaving the workshop and getting not just 500m down the road I put my foot down and blew a pipe off. I am presuming that the temporary fix has worked then. I managed to re-attach the pipe with the aid of a one pence piece and continued on home very gingerly trying to avoid boost. I don't think the rain would have allowed it anyway. Will resecure all the plumbing in the morrow and await a replacement J boot.

 

[Frenchy]

BTW My proposed method probably would leak []

 

[944Turbo]

Strictly its only an air leak from the J boot, the pressure isn't built until after the turbo,
Tony