hustler's dyno thread - Page 7 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-25-2009, 01:33 PM   #121
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Any in car videos?
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Old 02-25-2009, 01:39 PM   #122
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Any in car videos?
just this absolute garbage one I made on my way from Dallas to Austin on sunday. I had a suitcase in the passenger floor and thought...why not make a vid.

so here's a 5th gear pull. This car is retarded in traffic.

I played with an orange gt3rs on the way into austin...I was absolutely shocked by what my car can do. Its not faster...but if one beats me up on the track I can only blame my skill behind the wheel. Its pretty cool when you get the thumb-up from a formidable car like that.
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Old 02-25-2009, 03:54 PM   #123
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great job.. this page was real helpfull.
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Old 02-25-2009, 06:19 PM   #124
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I started thinking today about MBP, LPP, and detonation.

I think I may have the car tuned a hair too aggressively. I'm starting to think the best, safest way to tune this car is with fuel. I'm considering retuning my spark tables on 91-octane, then running 93-octane in the car. I think that is sufficient headroom, and 2 gallons of purple gets me a 93-octane fuel cocktail for Oklahoma races. I also learned today that WOT at 4000rpm isn't any easier on the motor than 8000rpm. Full boost is full boost...if anything higher RPM is more forgiving.

Questions:
Are LPP and MBT synonymous?
Are my MBT driven spark values safe considering I was able to advance 2-degrees and not incur detonation past the MBT values?
What does everyone else think about tuning for a lower octane?

Last edited by hustler; 02-25-2009 at 06:34 PM.
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Old 02-25-2009, 06:26 PM   #125
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also, there's decent stuff in here for newbs:
Motorsport Developments - Technical Articles by Stu
I think the turbo sizing, spark tuning, boost control, and compressor map articles are required reading.
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Old 02-25-2009, 07:16 PM   #126
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stolen from Miata.net:
Quote:
Originally Posted by RodH
Aha, NOW he tells us he has 8.5:1 CR ...
Oh well ... interesting, all the same

... and on the question of PPP vs MBT: Kind-of. If you set the advance for each RPM so that the motor has rotated to the best position to push the piston down (~17ATDC?) in the same time the burn has reached it's peak pressure, then you should have the best torque.
Thanks,
Rod
sorry about leaving out a remarkable detail.

I also think its a reasonable assumption that MBT and PPP/LPP/PCP are synonymous, but how could I advance spark past MBT, not incur detonation, and not raise cylinder pressure? I'm starting to think there is a lot...and I mean a lot of headroom for more that 15psi from the tater in this motor. The only thing I can come up with is that my values at MBT and the negligible advance is that there is a lot of headroom in this motor. A lot.
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Old 02-25-2009, 09:41 PM   #127
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Quote:
Originally Posted by hustler View Post
...but how could I advance spark past MBT, not incur detonation,
It can happen, if you are running rich with a cool charge, but usually at low boost.

Quote:
and not raise cylinder pressure?
More advance = higher peak cylinder pressures.
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Old 02-25-2009, 11:41 PM   #128
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Hustler, I posted the following in your other thread on the MS forum:
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It gave the best #'s on the dyno. I'd love to hear the logic on why the biggest # on the dyno doesn't translate into the biggest # on the street.

Because your dyno's resolution is worse than how much power you would lose if you were advanced past MBT timing. A number of 1% of peak is what I hear in OEM circles for every 3-5 degrees plus or minus MBT. That's probably a smaller number than the resolution of any kind of commercial dynamometer. Things like ambient temp and pressure, altitude, gasoline octane etc. will always change MBT timing, which can of course be taken care of only by closed-loop control.

Since these changes are inevitable in real world conditions, its a safe bet to run 2-3 degrees south of MBT. Obviously there's no way to tell accurately which side of MBT you really are on, but that can be taken care of by using a calibrated EGT gauge when you're on the dyno. Also, OEMs who dont have the luxury of closed-loop spark control will typically run pig rich at higher boost to avoid detonation rather than adaptively retarding after a knock event has already occured. So you are on the right track as far as your post #124 is concerned.
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Old 02-26-2009, 10:18 AM   #129
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So I'm going to run to the dyno and work on finding MBT again, rolling back 2* from each. Then, for the 91-octane consideration, should I just back off another 2 degrees and rely on my knock sensor?

Sadly enough...my car is tuned so well right now that it doesn't feel fast anymore. Pulling that spark out is going to make me sad. lol
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Old 02-26-2009, 11:03 AM   #130
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I would use 91 and do a spark sweep in the relevant cells to get close to MBT using the dyno. Then look at the EGT and advance until it maxes out. Back off couple degrees from that in a 1000-1500 rpm band around where peak torque occurs (most likely area of detonation). I think that should get you 99% close to the edge on 91, and far away from trouble on 93.

This is all assuming your AFRs are where they should be. Pig rich 10.5-11.0 in the peak torque and above region is very safe. I wouldn't care much about other areas, as long as its in the 11.5-12:1 area.

Make sure you use a good EGT gauge. Not a commercial one like autometer or something stupid.
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Old 02-26-2009, 11:14 AM   #131
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tip: hustler, save a map that has your MBT values and write protect it forever. that way you can always have it as a reference and retard from there.
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Old 02-26-2009, 11:27 AM   #132
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Quote:
Originally Posted by y8s View Post
tip: hustler, save a map that has your MBT values and write protect it forever. that way you can always have it as a reference and retard from there.
I did and uploaded it to skynet. Come with me if you want to live.
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Old 02-26-2009, 11:35 AM   #133
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Quote:
Originally Posted by The_Pipefather View Post
I would use 91 and do a spark sweep in the relevant cells to get close to MBT using the dyno. Then look at the EGT and advance until it maxes out. Back off couple degrees from that in a 1000-1500 rpm band around where peak torque occurs (most likely area of detonation). I think that should get you 99% close to the edge on 91, and far away from trouble on 93.

This is all assuming your AFRs are where they should be. Pig rich 10.5-11.0 in the peak torque and above region is very safe. I wouldn't care much about other areas, as long as its in the 11.5-12:1 area.

Make sure you use a good EGT gauge. Not a commercial one like autometer or something stupid.
I don't think I'm going to get detonation anywhere. I was able to advance 2* more than MBT with no detonation...that was enough for me to know advance wasn't helping anymore.

My target is 12.4 at 101kpa, 11.8 in boost up to 7psi, 11.5 above that. These #'s made the most power actually. Now I'm back to questioning my AFR's. Why do you think I should go so much fatter? Going richer than 11.5 hurt torque, bad...and lots of people think 11.5:1 is safe at 14.7psi as a rule.

I have a Greddy/Omori EGT...waiting on BEGi to send my fitting so I can use it, lol.


Also, should I expect different spark values now that I have COPs? Actually, will anything be different aside from drivability?
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Old 02-26-2009, 11:36 AM   #134
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I did and uploaded it to skynet. Come with me if you want to live.
is there a way in your softWaReZ to set a spark base map and then use your main spark map to subtract from it? so your spark map will always be "MBT minus X" and you just fill in the X?
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Old 02-26-2009, 11:48 AM   #135
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is there a way in your softWaReZ to set a spark base map and then use your main spark map to subtract from it? so your spark map will always be "MBT minus X" and you just fill in the X?
ummm...I could just roll them back manually and save it. However, right now god is telling me to tune on 91-octane aggressively, and run 1 or 2 gallons of purple when I'm at the track in Oklahoma. I think that will be the safest possible solution...although my peak #'s will suffer. Maybe I can just go up to 300whp on the dyno for the street, then turn the boost down to 250whp on the track.

This will be dynodynamics horsepower, like a man.
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Old 02-26-2009, 12:05 PM   #136
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yes, you highlight all the boosted cells, enter your X value, and hit the minus button.
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Old 02-26-2009, 01:21 PM   #137
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Quote:
Originally Posted by hustler View Post
My target is 12.4 at 101kpa, 11.8 in boost up to 7psi, 11.5 above that. These #'s made the most power actually. Now I'm back to questioning my AFR's. Why do you think I should go so much fatter? Going richer than 11.5 hurt torque, bad...and lots of people think 11.5:1 is safe at 14.7psi as a rule.
First get the fuel map sorted out. Go down to the 10.5-11.0 range around the peak torque area, then you'll see for yourself that your MBT timing would have advanced 3-5 degrees in those areas. I guarantee you, you'll make more torque this way than running at 11.8 and lower advance.
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Old 02-26-2009, 01:33 PM   #138
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Quote:
Originally Posted by The_Pipefather View Post
First get the fuel map sorted out. Go down to the 10.5-11.0 range around the peak torque area, then you'll see for yourself that your MBT timing would have advanced 3-5 degrees in those areas. I guarantee you, you'll make more torque this way than running at 11.8 and lower advance.
How does MBT "advance" with more fuel? I thought "LPP" was a static # (+/- 14*) and once you hit it, you're not going to make any more power from spark advance (and with that logic, adding fuel does nothing unless you add air).

I see how adding fuel can prevent detonation, but if I'm hitting "peak cylinder pressure" before knock, then adding fuel and advance will not increase torque, right?

I'm asking, not arguing.

edit:
this thread is reaching epic "how to dyno-tune a car" status.
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Old 02-26-2009, 02:01 PM   #139
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semi on topic:

I just realized that the hydra has a spark aux trim map. if I set my main spark map to MBT, then I can use the aux map to reduce from that. say if I decide to run Water inj to obtain MBT reliably... when the water runs out, the flow sensor can trigger the "I suck" map.

it also has an anti-lag trim map which does the same thing. just ground an input and bam. or rather, not bam.
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Old 02-26-2009, 02:12 PM   #140
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Simple terms, richer mixture needs more time to burn hence needs more advance to reach the optimum PPP, which is between 12-20 ATDC depending on the engine. For a bore size of 80 to 90 mm, 14-16 ATDC seems reasonable.

Thats why MBT (max. brake torque) timing advances with a richer AFR.

Quote:
Originally Posted by hustler View Post
I see how adding fuel can prevent detonation, but if I'm hitting "peak cylinder pressure" before knock, then adding fuel and advance will not increase torque, right?
You're hitting pcp for THAT combination of AFR & timing. That doesn't mean that's the best pcp you can achieve for your engine. All I'm saying is, a safer way to make equal or higher torque is to run richer and more advanced. Try it, you might be surprised at the result.
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