Ignition ignitiion ignition
07-21-14, 09:47 PM
#1
Ignition ignitiion ignition
I preach strengthening the turbo rotary ignition system every change I get and a recent dyno tuning session has further reinforced my views on this.
Backstory:
I modified my ignition with a Crane Hi-6 and LX-92 coil per leading coil about a decade ago when I had misdiagnosed a power cut out as poor ignition. It turned out to be two separate things, fuel pressure dropping out under boost creep and BOV popping open.
However, when I dyno tune my set up I find it is unlike most people rotaries that make power by "leaning" out the air fuel mixtures. I believe leaning out the AFRs to make power is often a bandaid for poor ignition strength on a rotary.
This current dyno session:
My friends got a DynoDynamics dyno for their shop.
Its awesome in that not only does it have the ability to hold the vehicle at a set rpm to vary the load for steady state tuning, but it actually shows how much power the vehicle is making at that load point in real time (ie shows part throttle power under load).
Its not so awesome because it reads really really low rwhp numbers. Ie the healthier of the two "505hp" stock class C6 Z06s dynoed made 380rwhp and countless other hearts broken in my area as its the only dyno for 300 miles.
Luckily it has a "dynojet" setting where it spits out ego soothing numbers and the "dynojet" numbers were within 5hp on my car when compared to both the Dynojet dyno as well as Dyno Pack dyno my set up has been on.
1) The tuner was amazed that my engine wanted LESS timing to make peak power at many load points compared to the Haltech conservative base map I use. Less timing= more manifold burn= more boost. Sure it worked for steady rpm loading, but interestingly it make more power in the full dyno sweeps as well.
2) I believe I am reaching the limits of the turbo compressor (60-1 in little HiFi housing). This low reading dyno showed it made 300rwhp at 10psi boost and we could only get 330rwhp raising it to 18psi and 325rwp at 16psi boost seemed to be the "sweet spot". We were vigilant in checking for boost leaks.
Of course the final tune was 16psi to lower heat rise and thus increase the power over several pulls.
Even so at 16psi initially there was a 2psi drop in boost at peak torque that recovered at higher rpm.
We found the motor made the most power with the AFRs flatlined below the 10:1AFRs that the 02 sensor could accurately register once the wastegate was open.
Lowering the AFRs had the added benifit of eliminating the boost drop at peak torque and so raising overall power.
The engine had a 8" cone of flame out the 60mm "high priority" wastegate (manifold favors wastegate flow over turbo flow) the entire time the engine was at peak boost whether it was a cold pull or repeated pull. No flames out the exhaust tip.
Sound like the recipe for really high EGTs? No, my preturbo EGTs are 750-800C.
These findings were consistent with my earlier dynapack dyno tuning session where the tuner found no power leaning out the mixture from my street tuned 9-10AFRs except in the 7-8,000rpm range where 10.5:1 made slightly more power.
So five things learned from the dyno session:
1) It is possible to run very rich AFRs with no power drop with an upgraded ignition.
2) Timing advance can hurt power.
3) We have to remember we have an external as well as internal combustion engine
4) Every engine wants different tuning (your rotary might want something else)
5) Contrary to what we would have thought a forced induction rotary loses much less power from repeated back to back dyno pulls than an NA V8 (we are hillclimbers so we want to know what our power is when we are actually using it).
We dynoed about 50 pulls on my car and including steady state tuning used 15 gallons of gas in about 4 hours. We did 3 pulls back to back to back on occasion and the power would drop by as much as 22rwhp on the 3rd pull. Oil temps as high as 85C and 100% Sierra PG coolant @ 0psi up to 212F (185F T-stat).
The stock C6 Z06 LS7s drop from 380rwhp to 340rwp in a single back to back pull in ~60F morning pulls, the owners declined to do a 3rd pull as water temps were over 220F.
That power drop with heat and elevation change helps explain why my near stock FD has one of the highest top speeds on the "straight" at the top of the hill and my FC did as well- even though I have to brake for half the "straight" because the FC chassis is so shady and wheel/tire limited.
Backstory:
I modified my ignition with a Crane Hi-6 and LX-92 coil per leading coil about a decade ago when I had misdiagnosed a power cut out as poor ignition. It turned out to be two separate things, fuel pressure dropping out under boost creep and BOV popping open.
However, when I dyno tune my set up I find it is unlike most people rotaries that make power by "leaning" out the air fuel mixtures. I believe leaning out the AFRs to make power is often a bandaid for poor ignition strength on a rotary.
This current dyno session:
My friends got a DynoDynamics dyno for their shop.
Its awesome in that not only does it have the ability to hold the vehicle at a set rpm to vary the load for steady state tuning, but it actually shows how much power the vehicle is making at that load point in real time (ie shows part throttle power under load).
Its not so awesome because it reads really really low rwhp numbers. Ie the healthier of the two "505hp" stock class C6 Z06s dynoed made 380rwhp and countless other hearts broken in my area as its the only dyno for 300 miles.
Luckily it has a "dynojet" setting where it spits out ego soothing numbers and the "dynojet" numbers were within 5hp on my car when compared to both the Dynojet dyno as well as Dyno Pack dyno my set up has been on.
1) The tuner was amazed that my engine wanted LESS timing to make peak power at many load points compared to the Haltech conservative base map I use. Less timing= more manifold burn= more boost. Sure it worked for steady rpm loading, but interestingly it make more power in the full dyno sweeps as well.
2) I believe I am reaching the limits of the turbo compressor (60-1 in little HiFi housing). This low reading dyno showed it made 300rwhp at 10psi boost and we could only get 330rwhp raising it to 18psi and 325rwp at 16psi boost seemed to be the "sweet spot". We were vigilant in checking for boost leaks.
Of course the final tune was 16psi to lower heat rise and thus increase the power over several pulls.
Even so at 16psi initially there was a 2psi drop in boost at peak torque that recovered at higher rpm.
We found the motor made the most power with the AFRs flatlined below the 10:1AFRs that the 02 sensor could accurately register once the wastegate was open.
Lowering the AFRs had the added benifit of eliminating the boost drop at peak torque and so raising overall power.
The engine had a 8" cone of flame out the 60mm "high priority" wastegate (manifold favors wastegate flow over turbo flow) the entire time the engine was at peak boost whether it was a cold pull or repeated pull. No flames out the exhaust tip.
Sound like the recipe for really high EGTs? No, my preturbo EGTs are 750-800C.
These findings were consistent with my earlier dynapack dyno tuning session where the tuner found no power leaning out the mixture from my street tuned 9-10AFRs except in the 7-8,000rpm range where 10.5:1 made slightly more power.
So five things learned from the dyno session:
1) It is possible to run very rich AFRs with no power drop with an upgraded ignition.
2) Timing advance can hurt power.
3) We have to remember we have an external as well as internal combustion engine
4) Every engine wants different tuning (your rotary might want something else)
5) Contrary to what we would have thought a forced induction rotary loses much less power from repeated back to back dyno pulls than an NA V8 (we are hillclimbers so we want to know what our power is when we are actually using it).
We dynoed about 50 pulls on my car and including steady state tuning used 15 gallons of gas in about 4 hours. We did 3 pulls back to back to back on occasion and the power would drop by as much as 22rwhp on the 3rd pull. Oil temps as high as 85C and 100% Sierra PG coolant @ 0psi up to 212F (185F T-stat).
The stock C6 Z06 LS7s drop from 380rwhp to 340rwp in a single back to back pull in ~60F morning pulls, the owners declined to do a 3rd pull as water temps were over 220F.
That power drop with heat and elevation change helps explain why my near stock FD has one of the highest top speeds on the "straight" at the top of the hill and my FC did as well- even though I have to brake for half the "straight" because the FC chassis is so shady and wheel/tire limited.
07-23-14, 11:08 AM
#3
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i wanna go play on that dyno! seems like you would learn a LOT really quickly
08-04-14, 07:35 PM
#4
Old [Sch|F]ool
MSD 6AL: 135 millijoules/spark
Crane Hi-6: 1200 millijoules/spark
...
1.2 JOULES PER SPARK???
Kee-ripes!
I'm thinkin' that I'm going to get one of those instead of the MSD I have now.
Crane Hi-6: 1200 millijoules/spark
...
1.2 JOULES PER SPARK???
Kee-ripes!
I'm thinkin' that I'm going to get one of those instead of the MSD I have now.
08-05-14, 12:19 PM
#5
Yeah, when you are cranking a fresh rebuild engine to build oil pressure with fuel pump fuse out, and injector outputs disabled it will stumble start on the engine assembly lube fumes if you don't pull ECU fuse to disable ignition as well.
The downside to all that spark energy is the plug wear is much worse. Count on changing your leading plugs with your oil if you don't already.
I could see this being a serious downside if you had to run expensive race plugs.
The downside to all that spark energy is the plug wear is much worse. Count on changing your leading plugs with your oil if you don't already.
I could see this being a serious downside if you had to run expensive race plugs.
08-05-14, 03:21 PM
#6
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you should switch PJ, my MSD died. cause of death appears to be hooking it up to electricity...
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08-05-14, 04:53 PM
#8
Old [Sch|F]ool
I've never had an MSD issue. They have always just worked for me. ~40k on one box, ~70-80k on the current one.
The only problem that I do have is that if I use 9000+rpm at a rallycross, I notice the car stumbling and missing lightly when on the highway trip back home. So I pull off and have to scrape the flaky crust from the terminals inside the cap, and then all is well again. I'm running one MSD through an FC twin-post and a single FC trailing coil wired in parallel, and the trailing coil goes through the distributor. The distributor cap apparently doesn't like anything over 8000rpm because I never had this issue with the previous engine and its hard 8000rpm limit.
In case it isn't clear, it seems that under idle and light load, the trailing is critical. I can idle and cruise with no leading but the car barely runs with no trailing, until heavy throttle when the roles get reversed. Must be a bridge port thing.
The only problem that I do have is that if I use 9000+rpm at a rallycross, I notice the car stumbling and missing lightly when on the highway trip back home. So I pull off and have to scrape the flaky crust from the terminals inside the cap, and then all is well again. I'm running one MSD through an FC twin-post and a single FC trailing coil wired in parallel, and the trailing coil goes through the distributor. The distributor cap apparently doesn't like anything over 8000rpm because I never had this issue with the previous engine and its hard 8000rpm limit.
In case it isn't clear, it seems that under idle and light load, the trailing is critical. I can idle and cruise with no leading but the car barely runs with no trailing, until heavy throttle when the roles get reversed. Must be a bridge port thing.
08-06-14, 10:40 AM
#9
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the P port is like that too.
08-06-14, 04:55 PM
#10
Old [Sch|F]ool
You know, I wonder if running split timing would be a benefit for drivability. Very low timing settings at low load makes for excellent manners, but the engine response is soggy when you whack the throttle, so you learn to not whack, but do a kind of double tap to get the revs up and then whack the throttle. But if there was split, the idle/low load trailing precedence would mean the engine would be running happily at whatever low timing settings were there, but whack the throttle and it would cross over to the leading preference and that would be an instant jump in timing by whatever the split is.
But that would mean having to get another ignition box and 2-step module... Anyway this is not very relevant for single turbo subforum since you guys tend not to run distributors
But that would mean having to get another ignition box and 2-step module... Anyway this is not very relevant for single turbo subforum since you guys tend not to run distributors
08-06-14, 05:51 PM
#11
But we single turbo guys do play with ignition advance and trailing split, so it is relevant.
I find my engine (early opening, stock closing, "small" streetport) is happiest idling with very low timing (zeroed) and zero trailing split.
If I could run negative trailing split like an RX-8 I would.
Negative split pushes the compression charge across the rotor housing minor axis into the leading chamber so there is less work against the rotor.
As Load increases I add in timing and put the trailing split back in.
Around the transition into boost I again decrease the trailing split drastically as I find that increases EGTs and spools the turbo.
I add trailing split back in with boost and start to trail advance off with boost.
I find my engine (early opening, stock closing, "small" streetport) is happiest idling with very low timing (zeroed) and zero trailing split.
If I could run negative trailing split like an RX-8 I would.
Negative split pushes the compression charge across the rotor housing minor axis into the leading chamber so there is less work against the rotor.
As Load increases I add in timing and put the trailing split back in.
Around the transition into boost I again decrease the trailing split drastically as I find that increases EGTs and spools the turbo.
I add trailing split back in with boost and start to trail advance off with boost.
08-06-14, 05:52 PM
#12
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You know, I wonder if running split timing would be a benefit for drivability. Very low timing settings at low load makes for excellent manners, but the engine response is soggy when you whack the throttle, so you learn to not whack, but do a kind of double tap to get the revs up and then whack the throttle. But if there was split, the idle/low load trailing precedence would mean the engine would be running happily at whatever low timing settings were there, but whack the throttle and it would cross over to the leading preference and that would be an instant jump in timing by whatever the split is.
But that would mean having to get another ignition box and 2-step module... Anyway this is not very relevant for single turbo subforum since you guys tend not to run distributors
But that would mean having to get another ignition box and 2-step module... Anyway this is not very relevant for single turbo subforum since you guys tend not to run distributors
my MSD blew up, so i went back to stock, and now i have a ~10 degree split, and it is tamer. (i think it runs better too)
08-07-14, 01:20 AM
#13
Yeah, when you are cranking a fresh rebuild engine to build oil pressure with fuel pump fuse out, and injector outputs disabled it will stumble start on the engine assembly lube fumes if you don't pull ECU fuse to disable ignition as well.
The downside to all that spark energy is the plug wear is much worse. Count on changing your leading plugs with your oil if you don't already.
I could see this being a serious downside if you had to run expensive race plugs.
The downside to all that spark energy is the plug wear is much worse. Count on changing your leading plugs with your oil if you don't already.
I could see this being a serious downside if you had to run expensive race plugs.
Crane Hi-6 with lx92.
I did nearly 8-9000kms of very hard street driving in that period with no issues
08-07-14, 12:35 PM
#14
That is good news. I don't have any experience with quality race plug$.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
08-07-14, 04:36 PM
#15
Old [Sch|F]ool
I think my last set of four FC trailings lasted 20k miles.
08-08-14, 12:21 PM
#16
That is good news. I don't have any experience with quality race plug$.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
Thanks for making me spend even more money on stuff I didn't know I needed
08-08-14, 08:56 PM
#17
That is good news. I don't have any experience with quality race plug$.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
I tried the BR10EIX but the ground straps erode at an alarming rate. I would get a couple race events out of them and have to change them out as the increased gap would lead to ignition misfire at high rpm.
Those BR10EIX are bad, they drop the ground strap into the engine with detonation too. Had that happen twice- didn't learn the 1st time.
I just use stock 9 heat range plugs for now and they last much better as there is so much ground area with the surface discharge plugs.
I tried the AR3932X breaking in the latest engine and they worked fine, but they do have slightly more reach than stock plugs which scared me.
I have 1 crane Hi-6 and LX92 for each Leading plug. That is likely overkill and doing nothing but eating spark plugs.
08-11-14, 12:40 PM
#18
very cool stuff. are you running stock platinums or coppers?
Platinum.
Originally Posted by BLUE TII View Post
3) We have to remember we have an external as well as internal combustion engine.
i read your original post a few times and i get the other 4 points. i'm not sure i get this one.
The rotary loses a lot of air and fuel out the exhaust port during the overlap phase which expands (combustion) in the exhaust manifold.
In addition, it has a poor combustion chamber shape which leads to incomplete combustion and again dumps air/fuel out the exhaust port to expand (combustion).
This is why we have to use huge turbos to make any power, but also why we can spool those turbos like a much smaller one.
You can compare how the RX-8 vs RX-7 relates to turbo sizing to separate out how much of this is combustion chamber inefficiency and other "rotary weirdness" versus peripheral exhaust port overlap.
Quote:
Originally Posted by BLUE TII View Post
If I could run negative trailing split like an RX-8 I would.
Negative split pushes the compression charge across the rotor housing minor axis into the leading chamber so there is less work against the rotor.
why can't you? is it outside the capability of your EMS or is there some other reason?
Yes, just the archaic Haltech E6K I am using.
i remember a thread on here where some guys were throwing ideas around about spark plugs, power and reliability and someone had brought up using the NGK BUEs. up until then, i'd never even heard of them. i haven't seen much else floating around about them, but maybe it's something you can look into.
I am traumatized in regards to plugs with ground straps after losing two on the BR10EIX with detonation. I am going to stick with the "one less thing to fail" surface discharge plugs.
Platinum.
Originally Posted by BLUE TII View Post
3) We have to remember we have an external as well as internal combustion engine.
i read your original post a few times and i get the other 4 points. i'm not sure i get this one.
The rotary loses a lot of air and fuel out the exhaust port during the overlap phase which expands (combustion) in the exhaust manifold.
In addition, it has a poor combustion chamber shape which leads to incomplete combustion and again dumps air/fuel out the exhaust port to expand (combustion).
This is why we have to use huge turbos to make any power, but also why we can spool those turbos like a much smaller one.
You can compare how the RX-8 vs RX-7 relates to turbo sizing to separate out how much of this is combustion chamber inefficiency and other "rotary weirdness" versus peripheral exhaust port overlap.
Quote:
Originally Posted by BLUE TII View Post
If I could run negative trailing split like an RX-8 I would.
Negative split pushes the compression charge across the rotor housing minor axis into the leading chamber so there is less work against the rotor.
why can't you? is it outside the capability of your EMS or is there some other reason?
Yes, just the archaic Haltech E6K I am using.
i remember a thread on here where some guys were throwing ideas around about spark plugs, power and reliability and someone had brought up using the NGK BUEs. up until then, i'd never even heard of them. i haven't seen much else floating around about them, but maybe it's something you can look into.
I am traumatized in regards to plugs with ground straps after losing two on the BR10EIX with detonation. I am going to stick with the "one less thing to fail" surface discharge plugs.
08-11-14, 02:51 PM
#19
i don't get it. i initially mentioned the BUEs to you because when i first learned about them, they most definitely DID NOT have grounding straps. i bought 4 of these plugs about 3 years ago and i promise you the 2322/BUE plugs i received, stamped and labeled as such on the plug itself do not have grounding straps. i can provide photos if you want.
so i'm not sure if they're being replaced with another plug, but keeping the same number or if there is something else at work here.
08-12-14, 11:14 AM
#21
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they are a funny plug though. the ground strap is huge, but the stock gap is so big it basically won't run on the stock 81-85 ignition, the 86+ is ok, or you need an MSD. the stock gaps are also inconsistent, since its an autolite, the threads aren't always cut right, sometimes the reach is wrong, i don't trust that its an appropriate heat range, or that the porcelain can handle the job.
so they are great to tune idle, cruise, but i do not trust them for WOT at all.
08-12-14, 05:00 PM
#23
Old [Sch|F]ool
Oddly enough, the spark plug manufacturers seem to know this, given all of the myriad 3/4" reach 14mm thread spark plugs available from just about everyone.
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