Final drive swap + tune changes

[ITmushishi]

I've been researching final drive gear swaps -- something like 4.1 to 4.56. As those who tinker with tuning notice the engine is most sensitive to knock in 6th gear (RPM and other things being equal).

It occurred to me that not only will a final drive gear swap give me more torque where I can use it, but it will make the total gear ratio of 6th closer to the pre-swap total ratio of 5th. I think this will allow me to add a little more timing without seeing any more knock in 6th gear.

Anything else you'd adjust in the tune with a final drive gear change?

[phrosty]

Final drive ratio and ECU tuning are completely separate topics -- one can't be changed for the advantage of the other.

5000rpm @ 1.4 load will still be 5000rpm @ 1.4 load. The difference is that your wheels will be going a different speed.

[tomm.brz]

just change in romraider the 2 tables "gear determination thresholds A & B"


from:
8965,700640281148 5942,19076923077 4460,073981588139 3601,6636301192057 2851,760137608498


to:
9951,340472953198 6595,829938376418 4950,679930083977 3997,840033754424 3165,4499814639566


to let the dash display the correct gear

[n0thing]

Originally Posted by tomm.brz

just change in romraider the 2 tables "gear determination thresholds A & B"


from:
8965,700640281148 5942,19076923077 4460,073981588139 3601,6636301192057 2851,760137608498


to:
9951,340472953198 6595,829938376418 4950,679930083977 3997,840033754424 3165,4499814639566


to let the dash display the correct gear

How did you come up with those values? What if you change it from 4.1 to 4.88?

[tomm.brz]

From 4.1 to 4.55 is a 11% difference.. Just multiply to the right value
If you put 4.88 FD multiply x1,19
Doesnt have to be super precise to work good

[Tor]

Originally Posted by phrosty

Final drive ratio and ECU tuning are completely separate topics -- one can't be changed for the advantage of the other.

5000rpm @ 1.4 load will still be 5000rpm @ 1.4 load. The difference is that your wheels will be going a different speed.

I disagree. As correctly stated, the engine is more prone to knock the more physical load there is put on the engine. Physical load, as opposed to "engine load" (which is amount of air ingested per revolution).

After I switched to Ecutek, I made a custom table that adds/removes timing depending on gear. I was able to run a bit more timing overall and a fair bit more in total in 3rd gear. This is what it looks like:



By changing the final drive, all gears are made shorter and will physically put less load on the engine. If I was to change my final drive I would definitely revisit this table. Or if I was still using RomRaider I would look at Base Timing B and see if I could push it a bit higher.

[tomm.brz]

That looks interesting, but timings look a little too retarded in higher gear? Or does it mean you really had a chance to raise timing a lot on the base timing table?

How do you modify the Y axis on the custom map? I have racerom licence but still didnt figure out how to modify the number of cells on those maps.. Or. Do you have a master tuner version of proecu?

Edit: ah ok i saw that the custom map O already has only 6 cells On the Y axis.. Good

[Tor]

This is the total timing I run in 3rd gear with very high quality 100 RON EU E0 gasoline (95 AKI?). So I wouldn't exactly call taking out 3.5 deg at max rpm in 5th gear retarded (6th gear values irrelevant as they can't be reached). At 7000 rpm, total timing is 31.4 in 3rd:



I ran relatively close to these values with RomRaider too but would have FLKC in 4th gear and above. Some of it I could alleviate with the TCPC hack and some of it I had to accept.

It will have some FLKC if driven on track or very hard on the street (e.g. a lot of pulls one after another). Either you compromise or you adjust for one, or the other. Or I could, of course, make different timing modes with Ecutek if I wanted (I haven't bothered yet, but I run different AFR on track and street). I let the ECU retard what it needs though it may not be the most efficient solution. It's fairly recent that I switched to Ecutek and I didn't have the opportunity to test a lot on track since then either.


But, actually, I could otherwise run even more timing advance below 6500 rpm. The pull below was part of some other test I did (automatic AFR enrichment based on FLKC), so I was actually trying to provoke knock. I don't use this as it would require a dyno to see if it's advanced past MBT and I think this would be too much for track in any case.

But if it's not past MBT then it would be good for a dyno hero pull. It's on a custom input so I can add (or remove) timing with the Ecutek app on my phone.



Anyway, Ecutek is not the reason that I can run this much timing, generally speaking, the fuel is really good here! So your mileage may vary. You can just advance until you find your max in 3rd with RomRaider too and you will have the same result. But with RomRaider you might have to remove some of it again to keep FLKC under control in 4th and 5th, especially if you track. If it's a street driven car, that is being driven legally and never being revved out in 4th or above it doesn't matter.


Anyway, not to get too far off the point, which was that FLKC is definitely dependent on which gear you drive. As such final drive has to play a part as well.

As for the reason, why physical load on the engine would cause more knock, I would speculate that it has to do with how much time the engine spends passing through those more critical areas. I would presume it's generating a lot of heat and the longer it's "stuck" in a specific rpm the more the internals heat up and the higher the likelihood of FLKC.

As such you may get the same FLKC in e.g. 3rd when driving up a steep incline as you would drive level in 4th. It's not really the gear per se, but rather I would presume how much the engine is being restricted from accelerating. I think it might even be worth considering to tune per track if we are speaking pro level. Going up the steep fast back straight "Kesselchen" of the Nürburgring is very hard for the engine as an example. I guess with modern advanced stand-alone ECUs you could even make timing based on GPS input (I know it can be done with traction control with some units, so the TC loosen/tighten up depending on where you are on the track).


P.s.
The difference between ProEcu and ProEcu Tuner version is only that you can't compare tunes. So it's a bit more complicated to copy tunes (e.g. between calids).

[tomm.brz]

I also run euro 100ron but can t reach those timings also reducing PI
Which header are you running?

[Tor]

Originally Posted by tomm.brz

I also run euro 100ron but can t reach those timings also reducing PI
Which header are you running?

It's the Gruppe-S header. I run 20% PI from 3200 rpm to redline. The MY17 K00C tune runs 35% PI in the mid-range where MY13 tunes ran 0%. So not sure it's better to run less. It was discussed a bit in this thread. This is what Matt from Cosworth had to say:
http://www.ft86club.com/forums/showp...7&postcount=36

It also seems like RON measurements are not really reliably comparable across EU (even less so across the world). Specifically, I use Shell V power and they say it's minimum 100 octane, so I don't know how much higher it could be. I also run 102 octane from Aral (BP in Germany) from time to time and so far I couldn't tell a difference.

I should note that my car is pretty much under constant surveillance. I probably wouldn't recommend setting the timing this aggressive unless you log regularly anyway, even if you have the fuel to do it.

[tomm.brz]

Wr100 in italy or vpower are pretty good
Anyway Fensport in UK use PI 0% from 1600 to 5200 and then just 10%
Car is pulling good with higher timings than with 20% or more Of PI

What GDI are you using? Stock.. Ots v4?

[Tor]

Originally Posted by tomm.brz

Wr100 in italy or vpower are pretty good
Anyway Fensport in UK use PI 0% from 1600 to 5200 and then just 10%
Car is pulling good with higher timings than with 20% or more Of PI

What GDI are you using? Stock.. Ots v4?

I use my own matched to my header according to the advice in that thread I linked above and combined with a lot of testing. It did seem to have some effect on FLKC, especially at 3-5000 rpm as far as I recall.

[Kodename47]

Originally Posted by tomm.brz

Anyway Fensport in UK use PI 0% from 1600 to 5200 and then just 10%
Car is pulling good with higher timings than with 20% or more Of PI

Higher % of DI generally requires more ignition advance to make the same power. All to do with mixture and flame front speed.

[tomm.brz]

Yes of course in my tunes i keep PI 9-10% from 5200 and more ignition timing
I like it more than >20% PI feels more awake