Tuning concept for gasoline engine, 93 OCT

[BMWManiac]

I have a tuning question or concept of operation.....for my setup, I have a 91 BMW 325i and am running a BW 256 on an OBX manifold adapter up to 14 psi (stock M20, oring block, refreshed head, arp headstuds) and MS2. I'm working on my street tune before I get to the dyno, but when I am tuning my VE tables, at what point should I transition my tune down to 11.5ish AFRs? When I hit the throttle and making 0 psi, should I be around 13 AFR, 1 to 10 psi - 13 to 12 AFR, 11 to 14 psi (max boost) - 11.5 AFR? Basically, do I want my tune to be as lean as possibly (max of 13ish/12ish) while I'm reaching my max boost level and then hit my target AFR at max boost? Or should I be trying to hit the 11.5 AFR mark as soon as possible in the RPMs/when making boost over 1 psi?

Also, I know that the load changes with each gear. Having said that, when I'm tuning the VE tables after datalogging, each gear provides different AFR values at same RPMs, so should i make it a little richer in early gears so that a 4th gear pull gives me optimal AFRs?

Or does it just boil down to finding out the sweet spot of how the car responds to early spool with lean or rich AFRs....I'm sure this will be the response, but perhaps if I started with the correct concept, I could adjust the tune to finding the sweet spot

Also, if I'm in a higher gear, say 4th, and the rpms are around 1-2k rpms, the car tends to buck a bit....would this be an indication that the timing is too high? AFRs are usually spot on, so I don't think it needs more fuel then....but I could be wrong.

[Matt Cramer]

I have a tuning question or concept of operation.....for my setup, I have a 91 BMW 325i and am running a BW 256 on an OBX manifold adapter up to 14 psi (stock M20, oring block, refreshed head, arp headstuds) and MS2. I'm working on my street tune before I get to the dyno, but when I am tuning my VE tables, at what point should I transition my tune down to 11.5ish AFRs? When I hit the throttle and making 0 psi, should I be around 13 AFR, 1 to 10 psi - 13 to 12 AFR, 11 to 14 psi (max boost) - 11.5 AFR? Basically, do I want my tune to be as lean as possibly (max of 13ish/12ish) while I'm reaching my max boost level and then hit my target AFR at max boost? Or should I be trying to hit the 11.5 AFR mark as soon as possible in the RPMs/when making boost over 1 psi?

I'd go from 12 to 11.5 a little sooner. But not a whole lot.

Also, I know that the load changes with each gear. Having said that, when I'm tuning the VE tables after datalogging, each gear provides different AFR values at same RPMs, so should i make it a little richer in early gears so that a 4th gear pull gives me optimal AFRs?

Can you post logs showing this and your MSQ?

Also, if I'm in a higher gear, say 4th, and the rpms are around 1-2k rpms, the car tends to buck a bit....would this be an indication that the timing is too high? AFRs are usually spot on, so I don't think it needs more fuel then....but I could be wrong.

Again, this could be a lot of things; you'll want to data log it.

[BMWManiac]

Yeah, I'll take some more logs for the bucking.....I still cannot load a datalog file onto this site...says it is too big, maximum allowed size is 1MiB

[BMWManiac]

Here is the tune for example....

[Matt Cramer]

You can put the data log in a ZIP file.

[BMWManiac]

Please let me know if this worked!

[grom_e30]

i used to get the bucking when just resting on the throttle 4 or 5th gear like 30mph and when changing down a gear and very lightly on the throttle. i ended up changing the ve table to go lower and it smoothed it out. you ve table goes down to 40 but in the logs you see as low as 16kpa

[BMWManiac]

Is it possible to just add another set of rows or do I need to readjust the entire table?

[grom_e30]

you should be able to shimmy the table around with minimal re tuning maybe move the 40kpa up instead of the 45kpa then have a 20-30kpa at the bottom of the table

[BigLou240sx]

There is a button on tuner studio on the 3d maps that allows you to change the table scale bins and the map will shift and interpolate to suit the new scaling (using the previous table and scale numbers). It should be pretty close if your engine runs well where it will interpolate.

[BMWManiac]

Should the VE and Ignition tables have the same values as far as percentages in grey?

[quan3165]

Should the VE and Ignition tables have the same values as far as percentages in grey?

I think this is good practice so you don't get confused when switching between VE and spark tables. I set all my tables up to be scaled the same way- Load and RPM axes.

[BMWManiac]

Sounds like a good idea and I'll make the change.

I dropped my VE to 30 at the lowest row, so I'll update with how the car responds sometime this week!

[BMWManiac]

Also, just curious, but should I have a couple different maps based on season/weather changes? I notice when the temperature is 60+ the car runs/feels phenomenal! However, when the weather is 50 and below, my AFRs around idle tend to be really rich....I don't want to lean out the idle area for fear that when the weather is great, then the AFR will be too lean in the same VE tables!

[nathaninwa]

You should only need the one tune for all year round. When your tuning, try to make it all at the same temp, so when you start to see temperature related changes that's when you start to fine tune the air temp correction chart

I watch ego correction and make slight changes to air temp to bring them back to where they were. It works best under cruise when you know your hovering right around 100%

[BMWManiac]

I have MS2....where is the air temp correction chart?

[gruff511]

Did you ever resolve that bucking issue? I get the same issue as well and have changed timing and AFR's and it still happens when im between 1k-2k rpm.

[turbo conversion]

I have MS2....where is the air temp correction chart?

It is under Extended then MAT Correction table.

You can change temp. and correction for your region lowest to highest temp.

David

[BMWManiac]

The bucking is much better, but still happens. I've found if I lower the timing slightly it helps, but I haven't found a point where it is completely gone. There is plenty of fuel for that RPM, so I just either push in the clutch or down shift.....I'm thinking of adding a second table to increase resolution....not sure I want to since I have the car running well, but I want to get it to a point where it feels completely like stock