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Strategies for Dyno Tuning


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I've finished swapping the P90 shaved head onto my NA L28 and have the megasquirt tune pretty well dialed in for street driving as well as on the track. I figure it's now time to take it to a dyno and need some advice on the best approach to take. The main things I'd like to learn/accomplish are:

 

1) What's the optimum timing for max power at WOT for my combination of head and cam?

 

2) What are the optimum AFRs for max power at WOT?

 

3) and of course, how much power/torque am I making?

 

I've found a shop not too far from me with a Dynojet that is available for $105 per hour for self tuning and $175 per hour if they do it. I'm pretty familiar with my megasquirt set up (it's also controlling ignition) as well as datalogging, so am leaning towards doing it myself.

 

My questions are:

 

a) What's the best approach to achieving #1 and #2 in the shortest amount of time? Should I start with a baseline pull and then work on timing first, and then play with AFRs?

 

B) Am I being naive and thinking that I can do this myself? Should I instead just let them do it with me watching?

 

Again, my current tune is very driveable and has served me well on recent track days. My goal is to make sure I'm getting the most out of this combination, not solve problems.

 

I'm attaching my current timing and AFR target tables in case any of the NA experts have any advice to add.

Capture8-11-2008-9.06.53 AM_thumb.jpg

Capture8-11-2008-9.07.12 AM_thumb.jpg

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Before you hit the DYNO, I would run 36 degrees timing full at 2000 RPM and about a 12.7-13.1 AFR for a NA car with what I am suspecting is about 10-1 Compression Ratio? That will get you close to max power, than you can add or subtract from there to see if anything helps. Just do lots of datalogs prior to make sure it is right where you want it. My last dyno session lasted 20 minutes, just because I had it very close, it just took some slight tweaking.

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I agree with Bryan...get it in the ball park, and then it's 'control-shift-arrow up or arrow down' to figure out where your peak numbers are.

 

Most people will run to peak power, then richen slightly to ensure nothing is 'too close to going boom'.

 

The entire map should be done within 2 hours-3 at the outside.

 

WOT will be done first, then spend your time doing runs to fill in the load points below.

 

Generally, a Dynojet tuned car will 'run lean' when you take it out on the road and do a test run. Generally, as stated above, the dyno operators will simply highlight the whole table and bump the fueling up incrementally (less than 5% or so) to give the correct 'true load' numbers you need to run correctly on the street as opposed to on the dyno.

 

This is if the dyno is inertial only. If they can load brake you and hold the load point, then you can get a more accurate AFR for the engine loaded, and not just accelerating through a point.

 

And like Bryan says, once the map is optimized, changes for this header, or even a total displacement change only takes a few passes, and well less than an hour.

 

When we went from 2.8 to 2.0L in the Bonneville Car, the setup took 45 minutes to retune. When we changed header primary length, it was about 15 minutes. Changed the exhaust system configuration to run the belly pan, about 20 minutes...but most of that was B.S. ing with the operator while it was warming up. I think we made three passes and were done!

 

It's all a matter of playing with it, and changing only ONE parameter at a time. You got time, just go back and do the fueling. Once that's done, play with timing. Then go back and recheck fueling, just to be sure.

 

There are no set rules for a magic AFR or timing number. Advance it till you see no more power and back off a degree or two. Fueling, go rich, then lean and see where power is hiding. Then move a bit off that for 'margin of error' ... Usually you adjust rich to lean till you see power stop raising, and then go back rich a couple of steps. You can go until you actually see power start dropping before backing off and putting in that margin...but I'd only do that for cruise spots where it's lightly loaded. For WOT, generally rich to lean till power stops raising then back a coule steps rich (rich best)

For cruise, rich to lean till you see power actually fall, then back a couple of steps rich (lean best)

 

splitting hairs I know, but it returns dividends in fuel economy.

 

After your base map handles slow roll-ons enable accel enrichmnent and start stabbing the throttle to get the accel and decel fuel cut working correctly.

 

Sounds like a lot, but if you're methodical, it goes pretty quickly.

 

If you have a ZX, go to the dyno with the bumper removed for easy fan access to the radiator! LOL

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I don't mind shifting the discussion to tuning turbos, but before we leave NA behind, to summarize what I've learned so far:

 

1) Get a good tune on the street using target AFRs at WOT of around 12.7 and timing of 36 degrees.

 

2) Assuming it's an inertia dyno, experiment to find the optimum AFR at WOT (find best lean and then richen a little).

 

3) Then experiment to find best timing advance.

 

4) Go back and verify best AFR hasn't changed.

 

All of the above is focused on getting the most power/torque at WOT.

 

Tony D, you mentioned tuning for economy. I wasn't going to spend any time on the dyno on that, but you bring up a good point that it could pay for itself quickly. But it wasn't clear to me how to approach that if it's an inertia dyno. Can you be a bit more specific?

 

And thanks for the inputs so far guys - this is exactly the kind of inputs I was hoping for! :cheers:

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WOT on an inertia dyno can be set in about 15-20 minutes. I mean everything. Complete.

 

The rest of the time is the 'drivability portion' of the map. Places where you are accelerating from a given load cel at less than WOT.

 

For 'economy' (and others can chime in here) anything below (on a stock cam car) 65KPA and less, and below around 3500rpm...those cels are usually best tuned for 14.7 to 15.5 AFR instead of 12:1.

 

Sure, it wil lrun well, and fat, and have some more torque.

 

But your fuel mileage will be atrocious. Anything with 'high vacuum' and 'low rpms' is not where you need WOT AFR's.

 

If you look at the specifications for the stock ZXT's you realize most of the cars don't go 'open loop' until 3500rpms, or 35% throttle opening.

 

So basically, where your car spends 95% of it's time is NOT tuned for 'power' but for 'economy' with the leanest AFR you can get by or tolerante without burning valves, or having drivability problems.

 

My wife's frontier tach juuust under 3500 at 80mph. So you drive 78 and the thing can get 20mpg (and you can see the O2 sensor feedback) speed that up to 81 where it's juuuust over that 3500 Closed-Loop setting in the ECU, and you drop almost instantly to 16mpg.

 

That kind of difference!

 

I need to go eat, so I can come back and flesh it out more if you need, but that's the general idea. If you've been dirving your car for a while, you know where that dot floats in most road conditions. Cruising speeds you tune lean best, for economy. WOT and above a given load cel block or rpm where it becomes clear you WANT more power, tune those areas for 'rich best'.

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I have done tuning on both load bearing and the dynojet dyno's

I wont have anything to do with the dynojet again. I ran the car and it did very well on the dyno, on the street however the car did rattle the pistons when driving the car. So yes you will have to do additional tuning on the car after you completed the tuning on the dynojet.

The load bearing dyno has it's place, and I believe it is a better dyno to tune with. The one thing that you will have to contend with is if you are running a MAF type system. Most people put the air cleaner in the front of the car, so when you start blowing air from a big fan on the front of the car you just may see incorrect readings from the MAF. That is one consideration to keep in mind when tuning. The higher rpm levels, and boost seem not to be affected to bad.

The other thing you will have to deal with on both dyno's is the air temperature into the engine. I was seeing 25 degrees C change on both dyno's the air was much hotter then running down the road. You will tend to go rich somewhat because of it.

AFR's, under power (boost) you will want to keep the AFR's in the 12.0 to 12.5 range, FOR BOOSTED applications. The N/a car you can run into the 13.1 AFR's and get better mileage, but you will see a slight loss of power because of it.

the 11:3-11:5 AFR's (for boosted applications) will turn your turbo exhaust housing glowing red, or in my case after jet-hot blue, PINK! that is way to much unburned fuel going out the exhaust, that is basically igniting in the exhaust turbine housing of the turbo. Very bad for heat and longevity of the turbo, not to mention the water temp will be around 100-110 degrees C not good for the engine in any stretch of the imagination. Keep in mind, that the weak spot of the L engine is in the rear cylinders of the engine, they run the hottest there. Ever wonder why Nissan did not put the water temp sensor in the thermostat housing, care to take a guess?

These engines will give you well 658Hp that I know of for sure. I did that @ 23psi of boost with my car. The car would not make more power on the dyno with 26psi of boost, but that was WOT, and air temps that were much hotter then running down the road. The car did just fine @ 26psi on the road and did make more power then on the dyno.

You know, it would be in your best interest to do like Tony suggested and get the drivability going after you have max power set at WOT. Get a friend to tune the car while you are driving, and find the steepest, longest hill you can find so that you can populate each tuning block with the correct AFR settings. then it's all downhill LOL.

Whatever you do, you are better off running rich then lean, so be careful, and make damn sure the management is operating correctly before you start. That includes the spark plug wires and boots as well.

I think that covers it.

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Before you even think about tuning on the dyno, make sure:

 

1. Your car can run reliably for an extended time period.

2. Your cooling system has enough reserve capacity to handle the dyno loads and lack of airflow.

3. You've got a good battery in the car and the charging system works.

4. The suspension is in good shape and all then nuts and bolts are tight.

5. You've got good tires on the car.

6. You figured out some good strap mounting points.

7. You know what you're doing regarding tuning.

8. Your computer boots up reliably and the tuning software works without bugs.

9. You've got a spare, charged up battery for your computer.

10. You computer/ECU connection cable works.

11. You have backups for your baseline and you can reliably restore from those backups.

12. Your toolbox has all the tools you'll need to make the tuning adjustments.

13. You have spare electrical wire, connectors, electrical tape, solder, soldering gun, etc.

14. You have the user manuals for your ECU, computer, and tuning software.

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Too many stickys already, pretty soon we will have to go immidiatly to page two to see the new post, ha.

 

 

As for the FAN affecting the MAF readings? What about a 80 MPH wind, does that effect the reading, or only a fan?? Hmmmmmmmmmm.

 

 

Max torque is produced at 13.2 AFR on a internal combustion engine although every engine is a little different. My NA motor runs at 13.1-13.3 at WOT with 36 degrees full timing for max power.

 

 

658HP??? Any actuall documentation of this? Pure speculation on a guess of what drivetrain loss there actually is, or is this a verified number on a engine dyno, or????

 

 

 

We tuned the Twin Cam car on a dyno jet dyno, made great power, and was perfect right out of the box, when driving on the street. I data logged on the dyno, and on the street, and the AFR's were EXACT, I was impressed.

 

 

Data logging is your best friend. Dont have someone tune, that doesnt know what they are doing. Get it close by easing into the throttle, then start datalogging. We usually get a car 98% tuned within an hour or so, when street tuning. I think People get too hung up on tuning on the dyno. Tuning for WOT is one thing but for anything less than WOT, doing on the street is SOOOO easy. I was talking to another member of the board today at my shop, and we were discussing how people dont know how to actually tune their EMS, and that causes MOST of peoples problems.

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I've been datalogging and then using megalogviewer to modify the VE table and with MSII Extra I've had really good success getting a very drivable tune. At this point what I can NOT do on the street is a) safely tune for WOT and B) determine the best spark advance and VE at WOT for max power. That's what I hope to accomplish on the dyno.

 

Again, thank you all for the advice - this is good stuff! I'm thinking I'll rent the dyno for self-tune and do it myself.

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Road tune it first for sure. Get a good feel for everything and get it fairly even on A/F ratios before you go paying $100+ per hour to learn some tuning when you should be dialing the engine in. Most dyno tuners that aren't familiar with your engine and your engine management are going to end up costing you some time/money to do the same thing. You will be surprised how well you can "feel" how it's behaving on repeated road pulls and end up getting within a decent margin. I wouldnt consider dyno tuning until you have it as far as you can on the street. Especially now that they gave you some L28-specific targets to shoot for.

 

On turbo, it really varies by the engine (and the wideband to a tenth or two) what the best AFR is. I am surprised that best power is achieved at 12.0~12.5:1. That's rather lean for a turbo car, but it's obviously working. Generally some engine designs like richer fuel and more timing (boxer engines that I know of) and some like lean and not much timing (mitsubishi evolution, etc.). If you back off on both (rich and retarded) you will get the turbine hot like jeffp said. If the timing is decent for the motor, you can dial it so rich that you get spark blowout with heating the turbine up excessively. EGT's are handy to have as another tuning tool. (and diagnostic tool after it's tuned)

 

Overall, be wary of running your pulls too close together on the dyno or your engine won't pull as much air as it should and run rich (like they said). Once you tune the richness out, you will end up lean when you get it back on the road. Most dynos cheap out on fans which causes a lot of that. Even though you have air temp and coolant temp compensations, it still doesn't account for everything that happens to an engine sitting stationary and running pull after pull without some cooldown and proper cooling. I used to run a shop and we had a 4-wheel dynapack. For "quick" tune jobs I could usually get a pull in every 2~3 minutes (on a fairly unstressed setup) but if it dragged out I would stretch that out further. I had a very good fan collection, however. Watch your baseline coolant and air temp numbers in megasquirt to get an idea.

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Before you even think about tuning on the dyno, make sure:

 

1. Your car can run reliably for an extended time period.

2. Your cooling system has enough reserve capacity to handle the dyno loads and lack of airflow.

3. You've got a good battery in the car and the charging system works.

4. The suspension is in good shape and all then nuts and bolts are tight.

5. You've got good tires on the car.

6. You figured out some good strap mounting points.

7. You know what you're doing regarding tuning.

8. Your computer boots up reliably and the tuning software works without bugs.

9. You've got a spare, charged up battery for your computer.

10. You computer/ECU connection cable works.

11. You have backups for your baseline and you can reliably restore from those backups.

12. Your toolbox has all the tools you'll need to make the tuning adjustments.

13. You have spare electrical wire, connectors, electrical tape, solder, soldering gun, etc.

14. You have the user manuals for your ECU, computer, and tuning software.

 

Great list John.

 

I would add:

 

- Verify that the timing you set in your ECU matches what you see with a timing light.

- Bring an extension cord for your laptop

- Create a basic conservative timing map

 

Here is what I would suggest for tuning your NA motor.

 

- Set max advance to 25-30 deg

- Dynojet: do some pulls, check AFR and listen for detonation. Try to correlate dyno results with fuel map bins.

- Dynapack: Set dyno to maintain RPM point. Tune all fuel map bins to 12-13:1. Listen for detonation. Let engine cool after every other RPM band.

- Start increasing max advance a few degrees at a time. Listen for detonation and check AFR. AFR will go lean as advance is increased because it will start making more power. Adjust mixture to maintain 12-13:1 AFR. Keep increasing timing until you here detonation. Check AFR. If AFR is 12:1, and you still get detonation, you have hit the wall. Back off timing a few degrees and do another pull. Give yourself at least 2 degrees of head room to account for bad gas.

 

I spent a few hours with the race car on the Dyna Pack last weekend. Here are the specs:

 

L28

1mm flat top ITM pistons

Stock, unported N47 head

Stock head gasket

460/280 camshaft

Port match intake manifold with 60mm TB

6:1 header -> 2.5: exhaust -> 3" Supertrapp

Stock 81' ZX NA distributor and coil

Made 185HP at 35 deg advance, but detonated

Set max advance to 30 deg, no detonation:

 

Club-Car-aug-08.jpg

 

ZCCNEDynoDay8-2-08008.jpg

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"As for the FAN affecting the MAF readings? What about a 80 MPH wind, does that effect the reading, or only a fan?? Hmmmmmmmmmm."

 

Take a MAF equipped car, idling, remove the air cleaner, situate the MAF element so you can blow into it, and blow into the thing---the engine will bog if not outright die.

 

On many BMW's now, you can not adequately dyno check their power because they have sensors that monitor airflow through the engine bay and detune the engine accordingly when it shows the car is not moving through the air in real-time.

 

And yes, an 80mph run down the highway would result in different readings that a static run down the dyno---it would alter the AFR. This is why the MAF's have so much baffling and pulsation dampners built into the system beforehand. Most modern MAF equipped cars actually pull air from the fenders to prevent the very condition Jeff is talking about.

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"As for the FAN affecting the MAF readings? What about a 80 MPH wind, does that effect the reading, or only a fan?? Hmmmmmmmmmm."

 

Take a MAF equipped car, idling, remove the air cleaner, situate the MAF element so you can blow into it, and blow into the thing---the engine will bog if not outright die.

 

On many BMW's now, you can not adequately dyno check their power because they have sensors that monitor airflow through the engine bay and detune the engine accordingly when it shows the car is not moving through the air in real-time.

 

And yes, an 80mph run down the highway would result in different readings that a static run down the dyno---it would alter the AFR. This is why the MAF's have so much baffling and pulsation dampners built into the system beforehand. Most modern MAF equipped cars actually pull air from the fenders to prevent the very condition Jeff is talking about.

 

Tony, if the maf is located high enough upstream on the intake the resulting problem would be minimized no? I grab my air in my S14 from in front of my drivers side tire.

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No.

 

The further upstream the MAF is located (meaning closer to the air cleaner) the more susceptible it will be to 'puffs' of air making it get a false 'high airflow' indication and transmitting bad data to the ECU.

 

You are taking it from an area where there is not airflow blowing on the element. The wheel wells are actually lower pressure.

 

If you remember a few years ago on GRM 2000 Challenge there was a Z31 with the MAF stuck through a snorkel in the hood facing forward. This gave the car 'Full Rich' when moving. In that case, the MAF could read significantly different numbers if you were driving into a 30 knot headwind than going in the other direction with the wind at your tail. In such a setup, a stiff breeze might indeed make the car run rich enough at idle to stumble. Explain that to someone...your car died because the wind was blowing too hard!

 

My kid was like 4 years old when I 'Blew Out The Fire' on a Ford Thunderbird. Picked up the MAF and blew into it, car died. Restarted it, and let him blow into it, and he killed the engine as well. MAF's are VERY accurate at reading airflow---this can be good and bad!

 

This is why most MAF systems have defined runs of piping before and after the sensing element, and why most performance mods center on removing the prepiping and belling a smooth entrance to the MAF (JWT or HKS POP Charger style)---any little change in throttle will cause the MAF to read and richen with these setups. It takes out the engineered deadband in the operational characteristics of the sensing element making it more responsive to changes in airflow.

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>As for the FAN affecting the MAF readings? What about a 80 MPH wind, does that effect the reading, or only a fan?? Hmmmmmmmmmm.<

 

Yes there is a difference between a 4' fan blowing on the front of my car then driving down the road. The hood is open on the dyno, and there is a much smaller amount of air going across the radiator on the dyno. AND I am very happy that is the case. The car will run into the 100-110 degree C water temps in no time on the dyno, interesting enough, I don't have that problem on the road. And yes there are times with a good cross wind on the freeway I do get the occasional surging. That is just the nature of a MAF, and it's location.

>658HP??? Any actuall documentation of this? Pure speculation on a guess of what drivetrain loss there actually is, or is this a verified number on a engine dyno, or????<

Ok 5% loss through the drive train @ 658hp=625hp 10% loss=592hp 15% loss=559hp 20% loss=526hp I posted a run that stated 537Hp @ the wheels with 509 foot pounds of torque, that was not the final WOT run, so you tell me.

I don't build the dyno's Brian. So if the guys running the dyno tell me the car made X amount, and give the graph, or in this case show me the readout then I tend to believe what they say. Now they also had an engine dyno at the shop they test engines on, I did not want to take the time effort and money to dyno the engine that way.

 

I don't know what your problem is other then your age for one, but I don't have a thing to prove to you or anyone else for that matter. The car does what it does. You really seem to have this need to be the top dog, well be the top dog Brian, not that I believe I am. I built my car to acheive a result and it has done that, with all of the things a number of people said I should have done this or that yada yada yada.

Your comments are not welcome nor are they helpful to anyone except your ego. You in my opinion are basically calling me a Liar, well so be it, I don't think I will lose any sleep over it.

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