Recommended AFRs for different setups
 

Hi all,

What's the general census of opinion for running scooby motors with AFRs, I know this can depend on setup so basic details@

Hybrid Garrett, can run 450+ on my car without meth and more with.
FMIC, 800 injectors, forged, etc, etc with 285 piper cams

What's your thoughts on idle AFRs with those cams?
What about light cruise AFRs?
What about boost AFRs, say levels of 1.2, 1.65 and 1.8 bar (the latter with meth only, the rest will be on two maps, one with meth and one without but both shell v max.

I've read some recommend running richer than 12 using meth and yet the likes of scoobyclinic seem to run 12.4 ish with meth...

This is general as I know it will be how the car behaves in the end and where knock starts for all the setups....

Re boost AFRs... Depends on what your exhaust valves, manifold and turbine wheel/housing are made of, where you make best torque and power, whether that performance is sustained at that AFR in hard use, whether the EGTs stay under control and whether knock stays away again in the hardest use. Depends also if your ECU can or does richen when the car is driven hard for a while in the worst conditions possible.

Also the reported AFR by a wideband lambda is not really AFR when you run any methanol. It is lambda and is calculated by taking the displayed "AFR" and dividing it by 14.7.

AFR at idle depends on whether you're trying to pass an MOT or have a stable idle, whether you have any cats.

Having said all that I would probably run such a setup showing richer than 12:1 with a decent slug of meth. I never gained from going leaner, and there is a lot to lose.

EGT gauge would help as long as you can mount it reliably and have a stainless steel probe before the turbo that is thick enough not to break off and go through your turbo.

Some ECUs allow EGT to influence the mapping, some make an estimate of EGT, some richen on timers etc.

The factors in my first paragraph are always the sorts of things you're considering to answer any question about the best boost, AFR, timing, you're obviously looking for the best safe settings that are up to all the abuse you can throw at it and a bit more.

Hey John, thought you'd left the world of scoobynet and went to the dark side, evo and BMW wasn't it?
Excellent response, knew it wasn't a "use this" type of question.

I have alcateck ecu and EGT in uppipe (the thicker probe type) and various other temp gauges including oil etc...so all covered for monitoring, infact I think I need another person in the car just to monitor gauges. The ecu can also read egt's and log them along with wideband...once it's setup, just waiting on ecu return.
I'll go with that then, <12.1 with meth, and yes sure will be thicking safe rather than max horses that wont last - it's funny how few rolling tests printing on here show 12.4 with meth and more power but I was thinking about 11.5 ish anyway. What's the AFR figure you've run with similar spec with say 1.6 or 1.2 bar vmax and non meth? Could I run in the 12s, keepin an eye on EGTs?

As for idle, I'll have two maps with 3d idle setup, set to specific rpm so one will be mot with 1 large cat, 2nd will be no cat and try for ultra smooth idle, if it's ever possible. I can see me playing with the setup for a year or so as I dont use the car all the time but then that's all part of the fun I guess.
I dont intend to go over 880 on EGTs, ever....I'd rather cut power then go over that figure so valves should be fine and

E46 M3, then Evo 9, then R35 GTR and Legacy 3.0R.

I used to run mid 11s on Subarus (11.8 with 10% meth), but the only forged engine I had rattled (three failed builds, all three rattled but the supplier and builder have since managed to do others OK), so I was always tuning seriously on stock pistons. I lost one ring land for my trouble, on an EJ257 at 1.7 bar and an Ion P450, but headgaskets used to go for fun. All the other engines I've mapped in the same way don't do this, so it was related to the head clamping or hydrid EJ20/EJ257, or wobbly EJ257 design.

If you don't run into knock and can keep the EGTs cool then I would say you can go leaner if everything else is in order, but on setup it depends how hard you can safely exercise the car. It would pleasantly surprise me if you can get to 12.4 with EGT <880C (and keep it there!) pre turbo running 1.6 bar of boost when you drive it on the door handles on a hot day, but every spec is different. Let us know when your logging is going what you manage.

You don't need me to tell you it isn't worth chasing the last bit, dial it back a bit and keep it cool and hope it lasts. Of course in your composite AFR, some cylinders could be leaner than others. Not sure if your ECU allows individual cylinder knock detection to see how likely this is, but multiple lambda or EGT probes in Subaru manifolds in my eyes just gives more changes of leaks.

Hmm, interesting, which one did you enjoy most?

I remember you putting topics about the issues you'd had over the years...fingers crossed not on mine but who knows. I've had 1.8 bar for a short period from the last tune (Bob R did tune) but standard run has always been 1.65...compression tests recently very good on all 4.
What head gasket type did you use and what bolts?

Ecu does have individual knock which until now I've not played with but I will and I'm sure I'll need to add a little to 4 and maybe 2.

I'm really hoping I can keep egt's to 880 ish or below, my weapons of choice are FMIC and water injection...

Evo handled by far the best on tight roads, GTR has most grip on bigger roads. GTR engine, gearbox, brakes, diffs are epic. Just a tune on stock exhaust is more than enough power for the available traction in many circumstances. Ride quality is firm. E46 M3 was a bouncy underbraked nightmare.

I had standard or Cometic gaskets, two different thicknesses, standard head bolts, all hotly debated at the time.

Make a contingency if using water injection in case it stops of course.

Funny that, I'd pick GTR every time as well its just I love the scooby sound (with decent pipes) more...

Hmm, I've got worries over my OEM bolts, wish done arp but lack of knowledge at the time but cossy gasket so should be better...time will tell.
Was thinking that and I know the ecu can control it but I've got so many additional wires coming out of the ecu already with wideband, egt and shift light plus others that really cant see I can rewire the existing Aquamist 3s setup...So perhaps I can add more knock protection or something, I'll ask the ecu suppliers see what they recommend. I do have LED warning light for it in the dash and digital flow display on top of dash though so some level of protection just not automated. cheers for this info, prob wont be into serious tuning till new year now as still waitiing for ecu to come back but getting the new software shortly, then have to setup all new features and protection levels and try to get idle sweet first.

Why not run and log on the current map Tony to see what its set at?

The new ECU should translate the old map so it still runs as it did.

Idle you will have sorted in no time

Dont worry Pete, I will do, if map runs nicely as is I'll not touch it but I was after real world experience from others as I've seen maps from SC and the likes and they run different AFRs for meth with good results. Will advise next year now but hopefully will at least get idle sorted this year (if ever get ecu back).