timing maps/strategies for old-school turbo engines

[thechuckster]

hi folks,

Wilbo666 and I did some tuning of the 18RTE last night

Much of his work consisted of pulling out fuel from my initial VE map and learning how to drive the tuning software while i avoided hitting things driving up and down Mt Cootha. So kudos to him for being a quick learner while under seige.

We've now got a fair wack of the fuel map tuned for near-stoich and some part of boost territory.

However, afterwards we were still guessing as to a good reference point (and a tuning strategy) for improving the timing map?

suggestions and comment on the maps below are most welcome...

As the engine old-skool (non-cross flow, SOHC, iron head, tapering combustion chamber) and forced induction (ex-RB20 turbo) i can only use existing data on 18Rx engines up to 0psi boost.

The engine CR is a low 7.4:1, injectors are 365cc/min and it has the world's stupidest plenum, being about 50% too small.

Will's borrowed a copy of Corky Bell's book for me to read, but anything else on timing maps would be handy.

Anyone with an 18RG turbo or similar 8 valve turbo willing to share their timing or fuel maps?


This is where we were up to on wednesday night:
(100kpa is 0psi):

Timing
http://www.mkhala.com.au/thechuckster/tuning_13_03_07/timing_14_03_07.gif
Fuel
http://www.mkhala.com.au/thechuckster/tuning_13_03_07/fuel_14_03_07.gif

If it helps you to visualise stuff, here's those two tables as 3D wire charts:
Timing
http://www.mkhala.com.au/thechuckster/tuning_13_03_07/timing_graph_14_03_07.gif
Fuel
http://www.mkhala.com.au/thechuckster/tuning_13_03_07/fuel_graph_13_03_07.gif

FOr those with megatune, see attached MSQ file - it's MS/Extra_HR_09c code so you may need to down the firmware from here (http://ys3al35l.googlepages.com/hr_09c.zip)(zip file).

[raddavey]

A good book to get is "How to Modify and Tune Engine Management Systems". Goes it pretty good detail optimising afr's and ignition maps. From my understanding Ignition timing is best optimised on the dyno to achieve RBT (rich best torque) or LBT (lean best torque). This isn't necessarily just before the engine start's to ping. It could be a few degree's before. They mention the most power is made when combustion occurs at 15degrees atdc.

[tortfeaser]

I dunno. But when you find out, let me know. I've just done a MS on an FJ20T, mainly on the road, and then on the weekend a few runs on a dyno. I'd love to know what to do just off max boost. Its running 11psi but the lag is huge. Hit the pedal and the boost comes in around 3800 in a big rush.

I'd love to know what the go is with timing before the torque peak to try and boost earlier and to get more while waiting for the lag to go away.

I'll post my MSQ and tables tonight when I've got the laptop. And scans of the dyno plots.

[thechuckster]

Marc: my boost is on by 3k or earlier - an effortless climb to about 5psi and then quick work to get to ~11psi.

am not sure if it is the timing, excess fuel or the manifold that's getting the turbo spinning. Accell tuning needs much improvement as it's going lean despite lots of fuel being added - perhaps that's what is spinning up the turbine quickly?

All: Forgot to add link (http://www.mkhala.com.au/thechuckster/tuning_13_03_07/megasquirt200703142233.msq)to MSQ file.

[Calibrator]

This may help. Rename to xls extension.

[poid]

lean and/or retarded conditions will help bring a turbo on boost earlier, due to the extra heat generated (compared to a richer/more advanced situation). So its gonna be helping the quick spool.

[thechuckster]

calibrator: that XLS is wonderful! is much easier to use than the estimator posted on the msextra forums. Can I share it around or would you rather it remain here?


poid: yeh, i suspect that it's mostly the temporary lean condition (AFR is jumps up before accel enrich takes effect) combined with the turbo (ball-bearing core if i'm not mistaken) allowing it to spin up quickly - plus a very free-flowing dump.

[bigmuz]

I would guess that any benefit of higher temps due to leanness would be offset by less mass flow of exhaust and fuel. If it spools up quick with it lean it will be better with it right.

[tortfeaser]

I'll give that lean-before-boost hits a try. I am running fairly rich there. MSQ attached, using version 029v. Spark, fuel and AFR tables attached. Tuning was done aiming for those AFRs and runs entirely closed loop a lot of the time.

Dyno plot also below - this was just some stuffing around on the local TAFE dyno, taking out a bit of fuel everywhere, adding advance just to see what would happen where. Inlet temp sensor not connected on dyno, so under-readding a bit I'd expect.

Grateful for any tips. Not really sure why torque drops away as significantly as it does. Its the NA FJ20 motor unopened (apparently the turbo version runs the same 9.?:1 compression) with the turbo inlet cam? I just tune the thing. Maybe its an exhaust cam timing thing. Maybe its the old school factory turbo. Can't change that (rules-its in a PRC rally car).

http://users.tpg.com.au/goodship/VE.jpg

http://users.tpg.com.au/goodship/spark.jpg

http://users.tpg.com.au/goodship/AFR.jpg

http://users.tpg.com.au/goodship/dyno.jpg

[Calibrator]

calibrator: that XLS is wonderful! is much easier to use than the estimator posted on the msextra forums. Can I share it around or would you rather it remain here

Its not mine I found it on a Danish website. May be best to keep it here?

[thechuckster]

OK - i'll not cross post it - you should probably remove attachment in a day or so.