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Old 07-02-2015, 07:03 PM   #21
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Originally Posted by patsmx5 View Post
Well I'm doing it for both I suppose. Make it safer, and while making more power if possible.


Like I mentioned above, this blower makes realllyyy hot air. I'm working on getting my intercooler to work better. Currently it's around 10-15 over ambient in cruise, and will climb an additional 40*F in a 1-2-3 pull to 8,500. It's an ebay bar/plate, maybe it sucks but I ran this same IC with a turbo and it was beast then, more like Ian's numbers.
Is it possible for an aftercooler for your setup? I just realized you lived in TX. We should pow wow one of these days. I'll bring some shiners.

Anyway, I honestly think you should give it a shot just to see. I run the stock MSM turbo and injectors, so I kept my timing table pretty lame. Until I go bigger injectors.
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Old 07-02-2015, 07:08 PM   #22
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Is it possible for an aftercooler for your setup? I just realized you lived in TX. We should pow wow one of these days. I'll bring some shiners.

Anyway, I honestly think you should give it a shot just to see. I run the stock MSM turbo and injectors, so I kept my timing table pretty lame. Until I go bigger injectors.
Yeah I've already got an aftercooler after the SC. Maybe I need another!

Edit: And yeah we'll have to meet up one day. I go to Houston Motorsports Park about every friday night they are open. If miata is down I run my C63. I'll be there tomorrow in the C63.
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Old 07-02-2015, 07:11 PM   #23
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Right, I'd forgotten you were running a blower. I have a GTX2863, which is one of the super fancy, new-tech efficient compressors that Garrett is turning out. My intercooler is a standard FM2 unit, nothing all that elaborate.

--Ian
Nice. Yeah the blower on paper doesn't heat the air that bad at lower boost, but at higher boost its efficiency drops and things get hot, fast. My SC air exit pipe touched the air filter, and burned the cotton black, for reference....
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Old 07-03-2015, 04:41 AM   #24
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Default Post your MAT Based Timing Retard Table

So this is what's called a de-rating situation. On aftermarket ECUs doing basic tuning I pick a max acceptable temp where I assume I'm going to try and still have good performance, and above that it's aggressive reduction in torque. So then you optimize the cooling hardware (intercooler etc) to stay out of the danger zone during expected use.

There has to be some kind of understanding of what the misfire limit is for AFR and timing. Either you induce it experimentally or you set it based on rule of thumb, past experience, etc. At some level of retard or enrichment it's just not going to burn and you will feel the engine hesitate. If you have a cat you could melt it from misfire.

If the goal is safety primarily, decide at what temp you want the ECU to go "oh ****" and pull significant spark and enrich just above the misfire limit. So if 7 degrees does it, pull 5 or 6. If 9.5:1 is too rich, enrich to 10.0:1 .

What patsmx5 is talking about is a progressive de-rating strategy. The more knowledge of hardware sensitivity and the more sophisticated the software is the more you can pull that off.

So i have experience tuning boosted engines for towing on an engine dyno, simulating pulling a trailer up a mountain in the desert. Usually that's at about 70C airtemp and maybe a somewhat elevated water temp.

What you end up doing is seeing how much torque you can get at each air temp by reaching all limits. My basic advice is (making generalizations without engine specific data):

Its More like an Exponential relationship between air temp increase and spark retard required. Going from 55 to 60C increases knocking more than going from 35 to 40C.

If you are starting out with an already rich mixture like 11:1 you are more likely to hit rich misfire from adding fuel to control knock before you hit misfire from pulling spark. Spark has more room for adjustment.

If you're trying to optimize torque at each IAT, rather than just focus on safety, it's sometimes actually better to add boost and pull spark if adding boost doesn't raise charge temps to much.

So in your modern stock ECU designed to help non carguy Joe Sixpack drive in the desert without noticing that his boosted engine is struggling, there's a whole torque arbitration scheme with temperature.

Add boost to increase airmass according to gas flow model up to compressor speed limit (modeled speed). Pull spark according spark sensitivity curve and knock sensor activity but only to minimum spark curve to prevent misfire. Enrich according to exhaust temperature limit and lambda sensitivity curve.

Once limits (rich limit, min spark, compressor speed) are reached, calculate a torque torque target reduction, and run all those calculations again.
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Old 07-03-2015, 12:42 PM   #25
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^^



arghx7, thanks for taking the time to explain this in plain English, I think even I understood it.
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Old 07-03-2015, 02:14 PM   #26
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^^



arghx7, thanks for taking the time to explain this in plain English, I think even I understood it.
I might be in the minority, but I think actually thanking people is 1000x better than any props system.
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Old 07-03-2015, 02:17 PM   #27
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Originally Posted by arghx7 View Post
So this is what's called a de-rating situation. On aftermarket ECUs doing basic tuning I pick a max acceptable temp where I assume I'm going to try and still have good performance, and above that it's aggressive reduction in torque. So then you optimize the cooling hardware (intercooler etc) to stay out of the danger zone during expected use.

There has to be some kind of understanding of what the misfire limit is for AFR and timing. Either you induce it experimentally or you set it based on rule of thumb, past experience, etc. At some level of retard or enrichment it's just not going to burn and you will feel the engine hesitate. If you have a cat you could melt it from misfire.

If the goal is safety primarily, decide at what temp you want the ECU to go "oh ****" and pull significant spark and enrich just above the misfire limit. So if 7 degrees does it, pull 5 or 6. If 9.5:1 is too rich, enrich to 10.0:1 .

What patsmx5 is talking about is a progressive de-rating strategy. The more knowledge of hardware sensitivity and the more sophisticated the software is the more you can pull that off.

So i have experience tuning boosted engines for towing on an engine dyno, simulating pulling a trailer up a mountain in the desert. Usually that's at about 70C airtemp and maybe a somewhat elevated water temp.

What you end up doing is seeing how much torque you can get at each air temp by reaching all limits. My basic advice is (making generalizations without engine specific data):

Its More like an Exponential relationship between air temp increase and spark retard required. Going from 55 to 60C increases knocking more than going from 35 to 40C.

If you are starting out with an already rich mixture like 11:1 you are more likely to hit rich misfire from adding fuel to control knock before you hit misfire from pulling spark. Spark has more room for adjustment.

If you're trying to optimize torque at each IAT, rather than just focus on safety, it's sometimes actually better to add boost and pull spark if adding boost doesn't raise charge temps to much.

So in your modern stock ECU designed to help non carguy Joe Sixpack drive in the desert without noticing that his boosted engine is struggling, there's a whole torque arbitration scheme with temperature.

Add boost to increase airmass according to gas flow model up to compressor speed limit (modeled speed). Pull spark according spark sensitivity curve and knock sensor activity but only to minimum spark curve to prevent misfire. Enrich according to exhaust temperature limit and lambda sensitivity curve.

Once limits (rich limit, min spark, compressor speed) are reached, calculate a torque torque target reduction, and run all those calculations again.
Sweet, thanks for the information!!! I do appreciate it sir!

Ok, so here's a few thoughts regarding what you wrote as it applies to my situation.

So basically there's 3 ways to derate power- less boost, Add fuel, reduce timing.

I'm using a SC that is about to be pulley'd to the max, so I won't be able to reduce boost. But that's ok as it seems if I can control AITs it's better to keep the boost and manipulate fuel and spark anyways.

Regarding misfire sensitivity, I know for a fact that with 10.5:1 compression I could run 9.5:1 AFRs with 170*F AITs and no misfire. When I did this a couple years ago, my intercooler wasn't working well so I ran lots of fuel to keep it safe. I don't know if I can run that rich with 9.0:1 compression though.

What I suspect is that with higher AITs, the limit to how-rich you can run changes. My guess is that higher AITs = can run richer before misfire. But I don't know that.

Based on what I know now, here's what I'm thinking.

Pick a number as you say to maintain full performance. I'll say 120*F.

Above 120*F, begin to enrich the fuel mixture as much as possible to control detonation. Say by 140*F I'm running 10.0:1 AFRs for example.

After 140*F, begin a timing retard. Make it an exponential curve as you say, not a linear one.
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Old 07-03-2015, 02:27 PM   #28
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I might be in the minority, but I think actually thanking people is 1000x better than any props system.
I would have posted that anyway.

The props system was great. Arghx7 has 64 posts and usually I'd take advice from someone with such a low post count with a grain of salt. However, we all know post count isn't everything, just look at me for example, or you I happen to be stalking him at the moment and reading his posts in other threads so I'm familiar with the quality of his submissions. Had I not been creeping I probably would have been as inclined to read the wall of text unless it had the props to back it up.

Back on topic... I feel like the base settings on most of our ECUs "as delivered" are a bit aggressive. I'm glad to see I'm not alone in this thinking. I appreciate threads like this and post like the above because it all comes together to give me a better understanding of what I'm trying to do.
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Old 07-03-2015, 02:36 PM   #29
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...Back on topic... I feel like the base settings on most of our ECUs "as delivered" are a bit aggressive. I'm glad to see I'm not alone in this thinking. I appreciate threads like this and post like the above because it all comes together to give me a better understanding of what I'm trying to do.
Yeap I like this where we can have good conversations and make progress and learn more!

Yes I want to optimize everything and I agree the "stock" settings aren't perfect for a miata. In my experience most of the stock settings for the car error on the side of safety, which makes perfect sense.

I guess the other thing I've learned from this thread is I really need to get my intercooler working better. I'm going to try swinging it down a bit to give it more airflow and see if that helps any.
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Old 07-03-2015, 04:21 PM   #30
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Default Post your MAT Based Timing Retard Table

Glad I could help. I certainly don't know everything but I hope I can at least bring a useful point of view that is at least readable.

In my experience from several boosted engine development programs, the stock intercoolers are sized to maintain between 45-50C (120f is like 48c) in 25c ambient, to achieve peak advertised rated power and to maintain vehicle max speed running at the governor. Above that the torque reduction can begin.

Those power rating tests are run in a quasi steady state, like flooring the engine in top gear at 1000rpm up to redline on a dynojet. So a lot of heat can build up.

That's one of the reasons some boosted engines appear underrated when somebody straps a stock one down on a dynojet on a 20c day. It's just not that abusive of a test and the air temps don't get that hot unless you do repeated pulls.
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Old 07-03-2015, 04:35 PM   #31
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Originally Posted by arghx7 View Post
Glad I could help. I certainly don't know everything but I hope I can at least bring a useful point of view that is at least readable.

In my experience from several boosted engine development programs, the stock intercoolers are sized to maintain between 45-50C (120f is like 48c) in 25c ambient, to achieve peak advertised rated power and to maintain vehicle max speed running at the governor. Above that the torque reduction can begin.

Those power rating tests are run in a quasi steady state, like flooring the engine in top gear at 1000rpm up to redline on a dynojet. So a lot of heat can build up.

That's one of the reasons some boosted engines appear underrated when somebody straps a stock one down on a dynojet on a 20c day. It's just not that abusive of a test and the air temps don't get that hot unless you do repeated pulls.
Hmm ok. So based on your math, the intercooler is keeping air temps withing 45*F of ambient under severe conditions. Alright, I gotta get my intercooler setup better.

So if I had an awesome intercooler that could keep air temps within 45*F of ambient, then I suppose tuning all of this would be much more straight forward.
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