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Old 09-05-2015, 01:43 AM   #1
arghx7
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Default I tune for OEMs. Ask me [almost] anything about engines/tuning.

Hey guys,

I've been around NASIOC for years now. I've done tuning at the OEM level (multiple OEMs) and in the aftermarket. I don't do aftermarket as much now--I'm not advertising any services, and I'm not trying to be a vendor here. I can answer questions to shed light on tuning or basically engine performance, emissions, and fuel economy. I know a lot about gasoline engines, port and direct injection, piston and rotary, turbo and naturally aspirated. I have a good understanding of diesel combustion, automatic/DCT/CVT trans, and computer controlled AWD although I've never personally tuned any of them.

Here are some threads of mine to check out:

FA20DIT new technology thread
Knock vs Preignition - cylinder pressure
Comparison between Rx-7 and Supra sequential twin turbo systems
Technical Ramblings

Things I can't answer:

1. Some questions about x OEM's future product - I probably don't even know the answer anyway

2. Anything confidential--I might be able to give a more general answer though to get the point across

3. Very detailed tuning/troubleshooting questions about your exact car ("I have a stumble, do you think it's a vacuum leak?") - this isn't the right place for that, make a thread in the appropriate technical section.
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Old 09-05-2015, 01:44 AM   #2
kgb4187
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How much is performance improved by removing the whole interior of a car?
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Old 09-05-2015, 01:45 AM   #3
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It really burns when I pee.
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Old 09-05-2015, 01:47 AM   #4
arghx7
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^^ that's a case by case basis of course. You have to look at the power to weight ratio before and after, and whether that somehow affected weight distribution.
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Old 09-05-2015, 01:49 AM   #5
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.......

Last edited by G3TD4T4; 09-05-2015 at 05:41 PM.
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Old 09-05-2015, 01:50 AM   #6
arghx7
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Arrrr.
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Old 09-05-2015, 01:50 AM   #7
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...........

Last edited by G3TD4T4; 09-05-2015 at 05:40 PM.
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Old 09-05-2015, 01:51 AM   #8
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Explain the mystery of ghost turds. Sometimes I know I leave a massive turd in the bowl, but when I look to see the fruits of my labor, nothing is there.

Are there poop gnomes just like underpants gnomes?
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Old 09-05-2015, 01:52 AM   #9
arghx7
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Quote:
Originally Posted by godfather2112 View Post
Explain the mystery of ghost turds. Sometimes I know I leave a massive turd in the bowl, but when I look to see the fruits of my labor, nothing is there.
high exit velocity and a small deuce meant that you basically fired a torpedo down the hole and out of sight
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Old 09-05-2015, 02:12 AM   #10
Calebz
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So far I find both the questions and answers to be enlightening and relevant to my interests. The poop thing has baffled me for years.

My question: How do I make my 12 year old awd 2.0 common rail turbo diesel more awesomer without sacrificing gas mileage or longevity?
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Old 09-05-2015, 02:14 AM   #11
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I know jack all about tuning, I'm curious to know what kind of parameters vary between reg. piston engines & rotaries.
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Old 09-05-2015, 02:42 AM   #12
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Did Ford really detune the 351 Windsor on purpose? Can you retune it? The heck does detune mean anyway?
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Old 09-05-2015, 03:06 AM   #13
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Is it true, that if I masturbate, I will burn in hell for all of eternity?
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Old 09-05-2015, 03:16 AM   #14
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Rare opportunity. Arghx7 is full of knowledge.
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Old 09-05-2015, 04:09 AM   #15
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-How much is typically "left on the table?"
-Who figures that out? Engineers or bean counters?
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Old 09-05-2015, 08:29 AM   #16
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is it best to tune an engine to C major or F#minor?
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Old 09-05-2015, 10:12 AM   #17
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Quote:
Originally Posted by SVX WRX View Post
is it best to tune an engine to C major or F#minor?
damn, I was just about to ask a question about why my low E string needs tuning way more than any other. Would expect an expert answer about putting lots of Lube on the nut...

Best of luck.



oh and I am not certain that you have any concept of what OEM means, but thats not really poignant to this thread other than the fact that it is.
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Old 09-05-2015, 10:47 AM   #18
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Quote:
Originally Posted by FellowTraveller View Post
damn, I was just about to ask a question about why my low E string needs tuning way more than any other.
It's because you're livin' low, next to the bass.
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Old 09-05-2015, 10:52 AM   #19
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With the Model X, how much do you plan to adjust the air/fuel ratio to get an even better launch in Ludacris mode?

chris619
dr_wheel


Full_Clip though the knock sensor is too sensitive in Insane mode.
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Old 09-05-2015, 11:11 AM   #20
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Quote:
Originally Posted by SVX WRX View Post
is it best to tune an engine to C major or F#minor?
When I built a bike wheel I checked spoke tension by checking the pitch at which it resonated. True story, and it's actually a valid method.

http://www.bikexprt.com/bicycle/tension.htm

Quote:
Originally Posted by FellowTraveller View Post
thats not really poignant to this thread
Uh, "pertinent" perhaps? (and "that's", too.)
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Old 09-05-2015, 11:15 AM   #21
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Quote:
Originally Posted by Calebz View Post
So far I find both the questions and answers to be enlightening and relevant to my interests. The poop thing has baffled me for years.

My question: How do I make my 12 year old awd 2.0 common rail turbo diesel more awesomer without sacrificing gas mileage or longevity?
I'd be more concerned that your diesel engine even has gas economy.
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Old 09-05-2015, 11:27 AM   #22
arghx7
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Can't answer all the silly questions although they are entertaining. I will try to get to all the technical questions.

Quote:
Originally Posted by Calebz View Post
How do I make my 12 year old awd 2.0 common rail turbo diesel more awesomer without sacrificing gas mileage or longevity?
Someone else here can certainly chime in, but since you said you don't want to affect gas mileage (can't increase injection volume), I'd say options are limited mostly to reducing restriction in the exhaust system. I'm guessing you have a TDI Volkswagen or something like that and they offer chips and such which are going to turn up the boost, change the injection timing and or quantity. I can't give any more insights beyond following a standard upgrade path for the platform. Sorry if that's not too helpful. "not affecting gas mileage" in the broad sense is highly constraining.

Quote:
Originally Posted by sjt View Post
I know jack all about tuning, I'm curious to know what kind of parameters vary between reg. piston engines & rotaries.
It's not as different from a piston engine as you think. I'll talk about the 13B-REW (last gen Rx-7) and 13B-MSP/Renesis (last gen Rx-8)

The big thing for the REW is that it has 2 of everything. It has 2 spark plugs per rotor, 2 injectors per rotor, 2 turbos run sequentially. So the tricky thing is knowing when the 2nd thing operates in relation to the first thing. It's also speed density, meaning there is no mass airflow sensor. Like most aspects of tuning, there are rules of thumb to go by.

The challenge for the REW is that there was never a widely available easily programmable stock ECU. So people jump to standalones immediately, most commonly an Apex'i Power FC. That was a pretty good system when it came out in the 90s, but the number of tables available to modify are limited and Apex'i doesn't update it.


trailing plugs - basic rule of thumb, 12 to 15 degrees between firing of leading and trailing at heavy load. So I fire the first plug at 15 degrees and the second at 30 degrees. If I fire the second plug too early, it will knock. This is because of the long combustion chamber and slow burn. The rest of tuning the trailing plugs isn't so important except for emissions





those are stock Rx-8 timing maps. One axis is rpm, one is load based on mass airflow sensor reading. The "separation" map is degrees after the leading to fire the trailing plugs. Leading - separation = trailing timing , in degrees BTDC firing.

injector staging - this depends on how the tuning software is set up. For a Power FC, you can just stick the same values in there or use the same formula for almost every car. Other systems are more complicated. If it's not done right you will get a hesitation.

turbo staging - very few run the turbos sequentially unless they have a power FC, as it really requires two boost control outputs and a switched ground with the right logic. The default settings in the Power FC are usually ok, but you can lower the transition hysteresis point (when it switches back from both turbos to 1 turbo during deceleration) and it helps response around town.


The other thing is the shape of the intake and exhaust ports. On a 13B-REW it has significant overlap which affects idle and low load. That causes emissions problems. The secondary air injection pump (similar to what 08+ EJ engines have) runs most of the time to clean up the exhaust and smooth out the combustion. On the Rx-8 they got rid of the overlap and that made the engine smoother at part load. Rx-8 also had an accessport available and uses a MAF sensor, so in a way it's easier to tune but doesn't seem to hold up well to high hp boost.
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Old 09-05-2015, 11:36 AM   #23
Russ77
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^

Response to first question is buy a chip. Response to second question is very technical.
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Old 09-05-2015, 11:49 AM   #24
arghx7
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Quote:
Originally Posted by atasnailspace View Post
Did Ford really detune the 351 Windsor on purpose? Can you retune it? The heck does detune mean anyway?
I'm hardly an expert on the 351 Windsor as it was designed by guys who are dead now or in an elderly assisted living home. Same could be said about say the 4.0 liter Jeep engine.

What I can say is that horsepower certifications have changed over the years in terms of how the lab conditions are set (air temperature for example) and the accessory load on the engine. For example, the "STD" correction factor you see on dyno sheets is really based on an old SAE standard that corrects to lower ambient temperature.

Remember that advertised engine power numbers come from running a slow speed sweep at full load on an engine dyno. It's sort of like a slow top gear pull, but with just the engine in a lab. Those are not very realistic conditions for driving around. The rules for exhaust backpressure and air intake restriction are kind of vague. For boosted engines it's even more murky for charge air temps, especially if it has an air to water intercooler.

People come up with rules of thumb for horsepower loss between rated power and dynojet results. But I've seen some engines that, when purchased from a dealership like any other regular engine, don't make their advertised power on an engine dyno without a straight pipe exhaust and an open intake. So if the engine doesn't seem to make advertised power on an engine dyno (or sometimes makes more, depending on how the test is run), those rules of thumb can be useless.

Quote:
Originally Posted by happasaiyan View Post
-How much is typically "left on the table?"
-Who figures that out? Engineers or bean counters?
I think you need to separate turbo engines from supercharged or naturally aspirated, as there's a lot more you can manipulate through the tune.

For turbo engines especially, there really is a thing called "product differentiation." Some team's job will be to report on what the engine hardware can do with a specific set of conditions (level of exhaust restriction, charge air temp assumption). Then the managers and bean counters will decide what to do with it. In some cases you have to put a lower power engine in certain applications because you can't fit a free flowing enough exhaust--notice how AWD models of some cars are rated at less power, because the transfer case kinks the exhaust a bit.

Other times, especially with turbo engines, you will see basically the same set of core engine hardware nailed down early on in development. Then you can sell a lower power version with a different tune, a standard power version at some performance level, and a higher power version with less exhaust restriction for example. You can lower the power level for when the engine is introduced and then crank up the boost a bit when they do a refresh of the vehicle.

Those factory "overboost" buttons come about when the basic mid range torque is intentionally dropped from what the engine can really do, in order to have a feature. At mid range rpms you've got a lot of room to manipulate the torque curve. At high rpm exhaust temperature, turbo speed limits, and backpressure become limiting factors. At low RPM the sizing of the turbine side may limit available boost, or there could be a low speed preignition concern.

Keep in mind though that OEMs are more constrained than aftermarket tuning providor. If the boost is too high and the turbo speed gets higher than what the supplier says is the limit, there will be warranty issues. Same with running exhaust too hot and having cat temps get too high. A regular customer won't notice these problems, especially a slightly over heated cat, but it could fail EPA "in use" testing and the OEM will get fined. Those cat failure check engine lights come on way after the cat is totally dead and won't pass emissions.
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Old 09-05-2015, 11:51 AM   #25
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Can you recommend a tire that has a quiet comfortable ride, good wet traction, great all season handling, superb grip and a class-leading warranty?

Preferrably, one that is specifically engineered to keep pace with my active lifestyle and preference for D cup size tits.







Why would a Datsun RX-7 have 2 spark plugs per brake rotor?
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