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I'll be swapping in a freshly rebuilt BP in the coming weeks and have some questions for first startup.
Current Setup is a completely stock '95 1.8 NA engine with I/H/E running ms3 basic and dyno tuned for 98+ ROZ / 93 'muricatane. I've attached the current tune to the post.
(And another spark table for 95 ROZ via tableswitch button)
The freshly rebuilt engine going in is a '96 1.8 NA with 85mm bore(+2mm), 85mm 12:1 Wössner piston kit, stock crankshaft and rods, -0,1mm head shave and -0,07 block shave from the machine shop and a 85mm 0,40" / 1,02mm thickness cometic headgasket installed. Mild porting/cleanup of the intake and exhaust ports. Everything cleaned and all new seals and gaskets.
*EDIT* I'm a dumdum and completely ignored the adjustable cam gears and camshafts - Catcams 3700619 with 254°/219° duration and 10,15mm lift. Original hydraulic lifters and valve springs. The head was already built in 2018. */EDIT*
So engine displacement should be 1929cc with 11.56:1 compression according to the web based engine calculator. A set of ultrasonic cleaned NB purple 265cc injectors was also fitted.
Cams:
Now apart from the obvious stuff that should be checked before the first startup of the new engine - rechecking sensor(TPS) calibrations, enable 10° fixed timing advance - what do I have to change so the current tune is adapted to the new displacement, compression and injectors ?
Going to Basic/Load Settings \ Engine and Sequential Settings \ Required fuel button, then changing Engine displacement from 1839cc=>1929cc and injector flow from 240cc=>265cc and pressing ok will rescale my fuel map automatically ?
Also turning down the spark map due to higher compression - how much would you take out across the board ?
This is the current 98ROZ spark table:
Yes it'll be road- and dyno tuned asap but just for breaking in the engine and the first oil swap these steps should suffice ?
You seem to have a good understanding about what you're doing.
With the req fuel adjustment your car should start fine and if you're lucky, it behaves pretty normal and drives ok, but it will need some more fuel everywhere.
You can add maybe 10% fuel over the entire map and let autotune adjust the rest, when breaking in the engine. It wont grenade on you with forged pistons.
Pull 4-5° timing above 50kpa, maybe 2-3° in your cruise cells, but those are relatively mellow anyway.
With such high compression I would skip 95 octane and only give it the good stuff.
You seem to have a good understanding about what you're doing.
With the req fuel adjustment your car should start fine and if you're lucky, it behaves pretty normal and drives ok, but it will need some more fuel everywhere.
You can add maybe 10% fuel over the entire map and let autotune adjust the rest, when breaking in the engine. It wont grenade on you with forged pistons.
Pull 4-5° timing above 50kpa, maybe 2-3° in your cruise cells, but those are relatively mellow anyway.
Thank you, noted.
Originally Posted by der_vierte
With such high compression I would skip 95 octane and only give it the good stuff.
Yeah that's only for "emergencies" when it's impossible to find a gas station with 98-100octane fuel nearby. For example in South Tyrol / Italy when you're driving mountain passes all day.
My 95 octane spark map for the stock 1.8 had -3° timing across the entire map. I'll check in with the tuner during the dyno session what/if he'd consider this safe with the new setup.
Sorry I completely forgot about the head / cams in the new engine. Dunno if that will also affect fueling but I'd assume so. Will definitely **** with my idle settings ?
I'm a dumdum and completely ignored the adjustable cam gears and camshafts - Catcams 3700619 with 254°/219° duration and 10,15mm lift. Original hydraulic lifters and valve springs. The head was already built in 2018.
Sorry I completely forgot about the head / cams in the new engine. Dunno if that will also affect fueling but I'd assume so. Will definitely **** with my idle settings ?
100% it will. Took me a long time to get Motorola Cup cams dialed in for idle... Don't be afraid to throw timing and fuel at it, and you will be idling at higher RPM and higher KPA values then before.
Right so I'm planning to clean up my AFR target table before retuning the VE table - it's a bit of a mess and way to rich to work around autotune issues we had during the dyno session.
Would this work for a high compression NA tune ? Any areas you'd change ?
Max power for an NA is 12.5-13.5. The AFR is not as much of a factor with a NA application as it is with FI. You may need to run a cooling trend because of the high comp on the upper end to reduce detonation. Read your plugs if they are peppered start with reducing the timing and then the AFR. The timing can only be reduced so much before the EGT's will start to run high. How lean you can run in the cruise section depends on your spark plug gap. If you are running a 1mm+ gap you can run well into the 15's even with the high comp since cylinder pressure/output will be low. Everywhere else I would run for max BMEP.
Max power for an NA is 12.5-13.5. The AFR is not as much of a factor with a NA application as it is with FI. You may need to run a cooling trend because of the high comp on the upper end to reduce detonation. Read your plugs if they are peppered start with reducing the timing and then the AFR. The timing can only be reduced so much before the EGT's will start to run high. How lean you can run in the cruise section depends on your spark plug gap. If you are running a 1mm+ gap you can run well into the 15's even with the high comp since cylinder pressure/output will be low. Everywhere else I would run for max BMEP.
So, maybe more like this ?
Plugs are NGK BKR7EIX at stock gap, so probably around 1mm .
I'm afraid I don't understand the last part.
Tune for maximum output, maximum brake mean effective pressure. This will net the best performance and drivability. One of the benefits of a programable stand-alone ECU is that you can have several tunes. I would start with one that is optimized for performance. If you need an emission or economy tune you can do that afterwards.
The best performance, highest cylinder pressure will be achieved with an afr of 12.5-13.5. On NA applications there is very little power change from one end of this range to the other. If you want a strong idle have a column specifically for that rpm. With cams you may need a slightly higher idle, 950-1krpm and with an afr of 13.8-14.2. Off idle-2krp to the 100kpa line should be tuned for max cylinder pressure. This will make off idle acceleration stronger.
There are very few area’s on the map that the engine will be in a steady state, usually that is the lean cruise region, 3-4krpm. Std gap plugs are usually .75mm which will limit you to 15:1 in the cruise area and there is nothing wrong with that gap or a 14.5-15afr in that section.
Tune for maximum output, maximum brake mean effective pressure. This will net the best performance and drivability. One of the benefits of a programable stand-alone ECU is that you can have several tunes. I would start with one that is optimized for performance. If you need an emission or economy tune you can do that afterwards.
The best performance, highest cylinder pressure will be achieved with an afr of 12.5-13.5. On NA applications there is very little power change from one end of this range to the other. If you want a strong idle have a column specifically for that rpm. With cams you may need a slightly higher idle, 950-1krpm and with an afr of 13.8-14.2. Off idle-2krp to the 100kpa line should be tuned for max cylinder pressure. This will make off idle acceleration stronger.
There are very few area’s on the map that the engine will be in a steady state, usually that is the lean cruise region, 3-4krpm. Std gap plugs are usually .75mm which will limit you to 15:1 in the cruise area and there is nothing wrong with that gap or a 14.5-15afr in that section.
thank you for elaborating.
I think stoiometrich 14.7 is lean enough for my cruise needs.
new attempt:
@yossi126
That first column was idle related and from the previous stock engine tune. idle with this engine is at 1000rpm so never even entered those cells. just forgot to also adapt those.
It is starting to look better. Most modern non-FI engines run in the upper 15’s to the 16’s in cruise. It does require a 1.1mm+ gap. For your app mid 14’s and a smaller gap fine.
Max power for an NA is 12.5-13.5. The AFR is not as much of a factor with a NA application as it is with FI. You may need to run a cooling trend because of the high comp on the upper end to reduce detonation. Read your plugs if they are peppered start with reducing the timing and then the AFR. The timing can only be reduced so much before the EGT's will start to run high. How lean you can run in the cruise section depends on your spark plug gap. If you are running a 1mm+ gap you can run well into the 15's even with the high comp since cylinder pressure/output will be low. Everywhere else I would run for max BMEP.
Also related to this thread https://www.miataturbo.net/megasquirt-18/knock-108054/ but I just pulled the plugs to check gap(all within 0,7 - 0,75mm) and signs of detonation.
I guess those small brown specks on the insulator confirm detonation ?
The black spots are small specks, the brown is fuel or oil deposits. The white insulator material on a spark plug and the piston are composed mostly of the same element which is aluminum. The aluminum oxide of the plug and piston material have an affinity for each other which is what the black specks are from. The plugs look ok and there might be some specks even when well tuned. I would further dial in your afr map and then tune your fueling table (VE) to achieve those numbers. AE will be important, don’t be stingy there. Don’t lug the engine by running high loads in high gears at low engine speeds. Also only run short intervals when at higher engine speeds while tuning. With one map for afr and timing for all gears it requires you to tune for the highest load interval which will be in the top gears 4th, 5th or 6th.
It will not be hard to make it work for average driving and acceleration. The difficulty will be in a track condition where the engine is at full load in and upper gear for a long period or on a high speed run on the street for minutes. After it is tuned fairly well you can start to creep up on the extremes but you should read the plugs and look at the piston tops afterwards. Knock sensors are ideal, but are hard to get setup. You can use a hose run to the engine and a stethoscope or ear muffs to hear the pinging better. EGT sensors or gauge would be a good idea.
Originally Posted by Stoffl
Also related to this thread https://www.miataturbo.net/megasquirt-18/knock-108054/ but I just pulled the plugs to check gap(all within 0,7 - 0,75mm) and signs of detonation.
I guess those small brown specks on the insulator confirm detonation ?
The black spots are small specks, the brown is fuel or oil deposits. The white insulator material on a spark plug and the piston are composed mostly of the same element which is aluminum. The aluminum oxide of the plug and piston material have an affinity for each other which is what the black specks are from. The plugs look ok and there might be some specks even when well tuned. I would further dial in your afr map and then tune your fueling table (VE) to achieve those numbers. AE will be important, don’t be stingy there. Don’t lug the engine by running high loads in high gears at low engine speeds. Also only run short intervals when at higher engine speeds while tuning. With one map for afr and timing for all gears it requires you to tune for the highest load interval which will be in the top gears 4th, 5th or 6th.
It will not be hard to make it work for average driving and acceleration. The difficulty will be in a track condition where the engine is at full load in and upper gear for a long period or on a high speed run on the street for minutes. After it is tuned fairly well you can start to creep up on the extremes but you should read the plugs and look at the piston tops afterwards. Knock sensors are ideal, but are hard to get setup. You can use a hose run to the engine and a stethoscope or ear muffs to hear the pinging better. EGT sensors or gauge would be a good idea.
Thank you for the input and tuning tips - will keep these in mind when I get give autotune another shot.
Regarding the AFR table - I honestly don't know what I could "furhter dial in" there.
Could you possibly post a screenshot or tell me what cells you'd further change how and why ? Fuel economy isn't a priority here, I just want it to run safe and be happy.
WIP from yesterdays first autotune runs with the new afr table. Couple sweeps with cell change resistance on easy and then normal. Still certain cells I wasn't able to hit (no downhill road part)
Haven't run warmup enrichment autotune tune so far, idle / AE and other stuff ported remotely from the previous stock engine tune by a club member who's pretty good at this stuff.
Spark turned down 4 degrees from dyno day to avoid any knock / detection false positives until I've figured that out.
03-01-2023, 04:39 AM
NA BP Engine rebuild - changes in tune ?
*/EDIT*
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Thank you for the input and tuning tips - will keep these in mind when I get give autotune another shot.
