Tuning MS3X for Bonneville at sea level

[aircooledtechguy]

I'm about to have my son Josh build the motor that will be in our '67 VW Squareback for Bonneville.  The motor will be a NA 2316cc Porsche 914 motor running MS3X with 2 MAP sensors which *should* be elevation compensating, COP ignition and of course a WBO2 sensor.  We're planning to dyno tune the motor with Mario Velotta of www.thedubshop.net which is my goto guy for Megasquirt and it's tuning, but live at sea level. 

My questions are:

1.  Since I'm going to be running 2 map sensors (one sensing the engine load and one sniffing the outside air pressure) should I be able to tune it at sea level and have it accurately compensate for the elevation at Bonneville or should I still plan on tuning a little lean at sea level??

2.  Any tips for a rookie running this EFI at Bonneville??  The car currently runs MS2 (MS2 extra firm wear) w/ EDIS and is dead reliable.  We're taking a big leap on this one and can't yet see the net. . .

We're really looking forward to getting down to the salt for the first time and going balls-to-the-wall and entrance (hopefully) into the 130 club!!

[maj]

all going to depend on your calibration of the altitude correction

i would tune for what you want at sea level then check and adjust the correction at Bonneville

You would get a good idea just idling and free revving and comparing to same at sea level 

[johnneilson]

Having minimal Megasquirt experience, meaning that I was not impressed with older ver2 units and switched to different brand.

I would approach this from the safe side.
Do the tuning on the dyno and get the AFR right. Be very conservative on the altitude trim map (~<3% or disable it if close to sea level, 70°etc. ).
 
Get your hands on a good air analyzer that has vapor pressure measuring and take notes when you do the dyno testing.

The altitude compensation trim can be adjusted when you get to Bonneville.

The approach would leave you on the rich side at higher altitudes and allow for trimming leaner easier.

Also, the pass at BV will probably be much longer than the dyno so thermal management will be factor.

You will have to make a Rookie run or two. This would be a good time to run the car and get some data on the pass. Then do some tuning.

J

[Matt Cramer]

I'm about to have my son Josh build the motor that will be in our '67 VW Squareback for Bonneville.  The motor will be a NA 2316cc Porsche 914 motor running MS3X with 2 MAP sensors which *should* be elevation compensating, COP ignition and of course a WBO2 sensor.  We're planning to dyno tune the motor with Mario Velotta of www.thedubshop.net which is my goto guy for Megasquirt and it's tuning, but live at sea level. 

My questions are:

1.  Since I'm going to be running 2 map sensors (one sensing the engine load and one sniffing the outside air pressure) should I be able to tune it at sea level and have it accurately compensate for the elevation at Bonneville or should I still plan on tuning a little lean at sea level??

The compensation is only as good as the correction curve. You'll want to tune it for an accurate AFR at sea level, then make sure you're still hitting those targets when you get it to the salt flats.

2.  Any tips for a rookie running this EFI at Bonneville??  The car currently runs MS2 (MS2 extra firm wear) w/ EDIS and is dead reliable.  We're taking a big leap on this one and can't yet see the net. . .

We're really looking forward to getting down to the salt for the first time and going balls-to-the-wall and entrance (hopefully) into the 130 club!!

Use the AFR Safety system and the MS3's check engine light feature to let it warn you if any sensor readings are headed out of bounds so you can shut it down quickly.

Bring spares of anything that's cheap that could shut you down, like crank sensors and maybe the injectors. You don't want to be sidelined with a dead $40 sensor and find the only parts store in Windover is out of stock on them.

[GH]

Matt, you will not need the things you take and the things you didn't take is what you will need.

[johnneilson]

I am living proof, last year at Bonneville we lost the crank sensor, or partially lost it.
The motor would run up to about 4500 then went flat.

Oscilloscope showed the signal die off. So much for ford parts and engineers.

John

[aircooledtechguy]

Thanks for all the insights guys.  I really appreciate it.  Since I do have mountains around here, I'm gonna grab Mario and head for a drive in the mountains with the car before we go so I can be sure we have the correction scaled correctly just for some piece of mind.