E85 tuning - how IGN timing affects boost
Posted: Thu Mar 20, 2014 3:25 pm
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
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