E85 tuning - how IGN timing affects boost

[PL]

Just thought I'd share an experience I had over the last week. It's been a big week. Turned out well in the end but I'm a bit ragged now..

Background. Built S14 engine in track car. I've been tuning this one for years. Started as stock S14 engine and slowly worked up to his current build. First big build was TD06SL2-20G, BC 264 cams, Tial 44mm ext WG, 1000cc inj, Z32 AFM and homebrew E20. He went with the E20 in an effort to achieve consistency. Pump E85 here varies from E60 to E90. It made 290rwkw on 20psi in this configuration and he did about a year of track work like that.

Then it torched a cylinder. Much investigation ensued but nothing was ever found. Bit like losing a 777! Best clue was that owner changed wastegate to 50mm Turbosmart and took it to the track without really checking what boost the new WG was giving.

Anyway, after a rebuild the decision was made to go full E85 and get an ethanol test kit to keep an eye on fuel consistency. This should allow similar power levels but on a tad less boost - as well as all the nice safety benefits that come with E85.


First dyno attempt - Thursday night.

We checked base timing and ran it up just using WG spring pressure to give minimal boost. This saw boost being very lazy to start with and then going uncontrolled at about 5000rpm. Hmmmm. Boost cut grabbed it at 26psi.

We tried various things but nothing worked. We called off the tune and decided that there simply had to be something funky going on with that new wastegate. But couldn't explain what other than maybe the shaft was binding.


Second dyno attempt - Tuesday night.

Owner changed back to the old Tial WG with 14psi spring over the weekend and we got it back on the dyno. Same deal. WTF??!! Much head scratching ensued.

We had a gathering of the great minds (anyone at the workshop who cared to stick their head in the dyno bay). Fingers were initially pointed at the WG, the manifold design and cam timing. We removed the rocker cover and checked cam timing - all good. Then IGN timing was questioned. I admitted that it did seem to be wanting a lot more timing than usual but I really hadn't done much with it as we were still in the "leave it conservative until basic AFR's and boost levels are set" mode. I added more timing. Boost was still going ballistic but it was doing it later. So I added more timing and boost went vertical later again. Hmmm. Until this point in the rpm range boost was perfectly controlled.

Got timing light out and double checked base timing. 15 degrees. Even gave it an extra 5 and ran 20 degrees base timing. Which helped a bit. I've just changed timing lights, so that was worth persuing. I've always used an old crusty timing light (which recently emitted the magic smoke that made it work) and it's functioned perfectly off Mr. Nissan's timing loop for many years. Using this method the new timing light was picking up the wrong edge of the coil pulse. I changed to triggering off the wires going to coil one (and later by using a plug lead extension) and there it was. Timing changed by 20 degrees. At idle it had been firing around TDC instead of 15 degrees. Idle was lovely and stable though.

So we reset timing and turned idle air right down to bring idle speed back. Changed IGN map values to something more sensible and suddenly boost was controllable. E85 plus radically retarded timing = silly boost. We'd created a jet turbine on the side of the engine! Obviously this was creating higher EGT's and big exhaust gas flow but I still didn't expect a result quite that radical. We ran out of time that night and had to come back next day. Sheeesh..


Third dyno attempt - Wednesday night.

We rolled the beast into the dyno bay yet again. Boost was still rising towards the end (min boost was 16psi up front which rose gradually to 18psi at redline). Finished up tuning to a max of 20psi, which was nice and stable across the RPM range. Had to gap plugs back to 0.6mm to cure a misfiring problem, so looks like new coils are on the cards. It made a handy 333rwkw (on DD dyno in shootout mode Shoot_4F) which was produced at redline. So I might get him to advance the inlet cam a bit next time to bring power back more into the midrange.

Anyway, all good in the end. But an interesting journey. IGN timing values finished up in the low 20's in the midrange, going up to mid to high 20's at high RPM using the MTBT method. Mixtures 0.84 lambda. I'm actually gonna richen that up a tad more...

Thanks to Trent for answering the phone and helping out in my hour of need. You are truly a gentleman and a scholar.

Keen to hear if anyone else has had any similar experiences tuning E85.

I tried to upload a nice dyno graph but it just made everything crash so I've given that up as a bad idea.

Pete L

[PL]

Here ya go:

S14 SR20 TD06SL2-20G E85.jpg

Final result after much shenanigans

(175.81 KiB) Downloaded 8147 times

[unex]

I have seen uncontrollable boost when AFR was way too rich. Leaning it out helped radically. Maybe you was "safely rich" at your starting point, besides ignition problems ?

[PL]

That's a distinct possibility. It was definitely rich. About 0.7 Lambda from memory. So it may have been a combination of things...

PL

[raddy]

for better ignition coils look for VAG pencil coils, they are incredible strong and allow to keep 1.1mm gap for plug even with very high boosts/rich AFR...
Kit for sr20det can be found here:
http://www.z-power.fi/catalog/product_i ... ucts_id=91

[bachig24u]

Pete,
Do you have a log of the EGT's?

KR
Sime

[PL]

Unfortunately not. Wish it did have EGT. It would have told the story straight away I suspect.

I'm gonna get him to add a fitting to the dump next time it's apart. Then I can just drop my probe in and monitor EGT on my meter. Be nice to log them in NIStune but I haven't made a thermocouple interface for my DLPIO board yet. No big deal - I've done thermocouple amp boards before (still have some AD595's laying around even...) it's just not something I use often...

PL

[RomChip200]

The problem with E85 is you can advance timing as much as you want till you throw out a rod ...
For experience, on my audi S4, I added over stock +7°, than 10° then 13° then 18°, all these gave me the same boosts and the same power at the end ... 350wrhp
but +18° is just not reasonable, so since few years, I oscillate b/w +7° and +10° over stock (that are basically reasonable values), +10° gives me the best fuel economy when cruising. With such value, when building boost, my S4 becomes a rocket.
Remember on a V6, the timing is maxed out at 60° (360°/6cyl), so when cruising any value over 60° will just be 60° BTDC .... Nissan ECU and Audi Bosch ME7.1 ECU do this check.

My 300zx IGN table for full E85 (down to 73% in winter, up to 85% in summer, I don't change timing accross the seasons):
16psi means TP = 78-82 in my case

v33.3 IGN table.jpg

(179.81 KiB) Downloaded 8061 times

[PL]

Looks about right. I've seen massive variations in how much timing E85 engines want over standard. Some will easily take 10 degrees - I go up 2 degrees at once and the power just keeps going up with ever 2 degree increment. Yet other engines for no apparent reason want little more timing than they did on 98. Very confusing.

I did another SR this week and besides the extra fuel I hardly changed the timing and it still made really good power (310rwkw+ on Mainline dyno). It didn't make any more if I added timing so I left it at that. He did a track day yesterday and all went well.

About the only problem was that it was tending to get hot. Yet when it was on 98 it ran nice and cool. Which is very confusing given that usually going to E85 has the opposite effect!

PL

[bachig24u]

LOL... more power... more heat...

[skyline_stu]

Hi Pete,
I've seen that retarded timing problem, many digital timing lights get fouled up with the trigger edge.

I have used a conventional plug lead for many years and check it right at the spark plug.

You've also probably noticed when tuning and you've added spark that boost often drops off [even though power increases],
as the engine is extracting more energy to push the piston rather that throw it out the exhaust port and get the turbo wound up.

I remember years ago after I fitted a ported head on my 'ol skyline that boost went off the 30psi gauge.
Mixtures were still good but all it would do was try and break off the needle's end stop.
After a lot of thinking, I threw a stack of timing in boost became normal and power went through the roof, but the AFR's went way lean.
Added in fuel and all was good again.

I developed the idea that the increased flow completly changed the engine's VE with the porting/chamber mods.
Engines with a good chamber design will loose power before knocking happens. [evo's come to mind]

I ended up running about 35psi in those days with 95ron fuel + a touch of 104 [1997-98].
All it did from then onwards was break rods like match sticks.

It often comes back to 'check the basics!'

Stu

[RomChip200]

You should also carefully look for knock, not with your ears but instrumenting the ECU variables. Because on E85, burning process is just so different and knock sensor may get knock that is not real knock !!!
On Z32, I got knock below 3000 on full boost, I tracked it but I wanted the keep the knock sensor management, this is why I cannot go above 15 16 16 17 18 20° below 3000 in last column, even on E85 !
On Z32, checking these variables is the knock indication:
fdb timing_offset2 ; instantaneous knock on accel
fdb knock_value ; continuous knock detected in gear
timing_offset2 EQU 0x1614 15
knock_value EQU 0x1610 11

You believe some engines don't want so much timing but maybe you advanced the timing but at the end, the ECU retarded it at low rpms when boost applies ! and then ECU applies the same amount of retard to all the maps once you went above 3000.

[unex]

.

[unex]

It didn't make any more if I added timing so I left it at that.
About the only problem was that it was tending to get hot. Yet when it was on 98 it ran nice and cool. Which is very confusing given that usually going to E85 has the opposite effect!PL

retard timing by 7-8 degrees on 98 and you will get hot too. Every fuel have to burn at time it should burn to keep temperatures in range. Now, because you left 98 ign table for e85, it means, its way too retard for e85. Its strange why it didnt made any more power while adding timing, but I would bet, that hot is related with retard timing

[PL]

Thanks for the replies guys. I'll definitely be trying more timing next tune. It's breaking the "only add enough timing to get to peak torque" rule but I'll do it all the same.

One other problem was that the car had semi-sticky track rubber fitted - which I think was affecting our measurements. So torque may have still been increasing but wheelspin meant the readings weren't showing it.

PL