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HOWTO: Custom OS - Boost by Gear / Boost by Speed


Roland@pcmtec
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Problem: You have a car that is making 500rwkw and simply cannot get the power to the ground on the street and is even losing to cars with less power on the drag strip due to a peaky and uncontrollable torque curve.

Solution: Utilise our boost by gear / boost by speed functionality to torque limit the vehicle in lower gears to allow the car to be as fast as possible.

To enable this feature you require the workshop edition and a 5 credit "Standard Custom OS". This is an extra 2 credits on top of a standard license.

First open the custom operating system wizard, select "Standard Custom OS" and press Next.

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You will then see a "Custom OS Options" page. Leave these options standard.

Press "Check License and Proceed" which will then ask you to license the file, this will charge you an extra 2 credits (total of 5 for the vehicle). This will only be charged once.

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You will now see a second set of Custom OS options (these can be changed as many times as you like). Select the "Boost Configuration" dropdown menu and you will be presented with various options.

Boost by Gear:

For a street car we always recommend "Boost By Gear" for all applications. In the ZF 6 speed auto gears 4/5/6 all use the 4th gear row. This is as the gear calculation code is legacy from the BTR and does not set a gear higher than 4th gear. We have found that in almost all applications you will want full boost by 4th gear anyway, however if you do need to reduce boost 4th gear we recommend using boost by speed instead. In manual vehicles the gear is calculated for gears 1-6.

Boost by Speed

For a vehicle which is doing 300kph down the drag strip or has a 2/3 speed gear box the boost by speed options may be more appropriate.

When choosing boost by speed you can choose a specific wheel or the average of all wheels. We recommend one of the front wheels for a RWD car. For an AWD car either pick "Boost by Speed" which will take the average of all 4 wheels, or pick the wheel with the most traction (usually a rear wheel).

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Press Next then "Finish" and the file will automatically save and re-open. Now navigate to the Wastegate Duty Cycle for Open Loop table and you will see gear (or speed) as the Y-Axis

As you can see the factory values no longer make sense as we are no longer referencing IAT as the Y-Axis.

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The next step is to set all rows to be the same by copying the row from the most common IAT. Repeat this for the desired boost table as well. Or if you are running open loop boost you can ignore the desired boost table.

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Next depending on the power the vehicle is making and how much traction you are getting in the lower gears you can try something like this. In this example we have multiplied first gear by 0.25 so that you will be running approximately 25% of full boost in 1st gear. 50% of boost in second gear and 75% in 3rd gear. Once 4th gear hits you will be running full boost.

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The above setup will allow a vehicle with hard non sticky street tyres to now get traction in all 6 gears on the street. This will make for a faster and far more fun vehicle, not to mention safer for when your partner takes the vehicle for a drive.

We recommend combining boost by gear with the MFT (Multi Flash Tune) and setting up the following tunes to maximise the potential of the vehicle. These tunes can be changed with the engine running at any time to allow you to quickly pick the correct profile for the weather/street conditions.

Tune 1: Valet / 0% boost (for other family members)

Tune 2: Low Boost (wet weather)

Tune 3: Boost by Gear (street driving)

Tune 4: High Boost (eg drag strip, burnout competitions etc)

To achieve low/high boost with boost by gear enabled, simply set all rows to be equal. This will negate the gear/speed part of the calculation.

Read more about the MFT here:

 

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Update. In the ZF 6 speed auto gears 4/5/6 all use the 4th gear row. This is as the gear calculation code is legacy from the BTR and does not set a gear higher than 4th gear. We have found that in almost all applications you will want full boost by 4th gear anyway, however if you do need to reduce boost 4th gear we recommend using boost by speed instead. In manual vehicles the gear is calculated for gears 1-6.

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I'm thinking of the numerous days when I'm an idiot and leave the ZF in Tiptronic 6th and give it the beans to over take a car on the terrible Vic Roads pot hole laden country roads on my journey to work. TCC unlocks and flashes up, I get 26 pound of boost and 1000+Nm at 2,500rpm in 6th gear.

I know it's not easy doing what you do. I remember there was some ideas being thrown about a while ago, but if maybe you have another sprog, that you may have some bored moments and could spare some time to revisit the code to see if there is a viable work around?  

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If you can find a PCM DMR that reliably shows the current gear and doesn't drop out to 0 during gearshifts or when the torque converter is slipping we can see if it's the right data type to patch in without any major changes. 

We don't have any ZF vehicles available on hand to test with. Only a 6 speed manual. 

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It runs as you would normally have those tables setup for either closed or open loop.

I.e. 

If open loop the boost by gear follows the open loop WGDC table for each gear row. It still does output the boost target as per what is commanded in the desired boost table so that needs to be setup for each gear a couple of psi above actual so the overboost protection can still operate. But obviously being open loop, ultimately the OL WGDC table sets the boost. 

If closed loop, it sets the boost target as per desired boost table. The closed loop calc will also use the respective OL WGDC table gear row.

Geez, hope that makes sense??? 

If you weren't running boost by gear before, and then choose to enable it after already having tuned the OL / CL boost tables, then you will have to go back and tune those again and for each gear. 

And as per Rolands information, if running a ZF just make rows 4, 5 & 6th gear all the same. If you're running closed loop boost control, It's a bit of a pain in the ass to set up 4, 5 & 6 because if tuned in a TCC locked nearly all the time strategy, in 6th gear it can build full boost by 2200rpm. It's more like 2800rpm in 4th gear. To get the tune right and not trigger overboost in 6th and not spend to long in underboost on 4th where you can get a boost spike, you need to do back and forward with 4th and 6th a few times until you have a compromise. Open loop is much easier but still requires the back and forward to ensure you don't build to much boost in 6th. 

 

Edited by hjtrbo
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It does make sense, thanks for the explanation. I figured it worked like that but haven't played with it much, except to have all the boost, all the time.

I had actually thought about turning gears 5 and 6 down, as there will be a load of load and heat generated to get the car to those gears under wot. Also it'll take some load off the trans.

I think my tc strategy will be mostly unlocked to take advantage of the high stall converter. My turbo is a big one and cams are hectic, so full boost doesn't happen until around 4k in 3rd and 4th. I've got a 4 port boost solenoid, so might just run it in open loop for a while until I can get a handle on what it needs.

Just thinking out aloud here, if the converter code can discern between the later gears, surely there is something there that can be related to the boost by gear code.

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What I think Roland was saying is the issue is in the PCM. Taking the load off 5th and 6th is a good idea. Especially in your case, with your high stall / big turbskie / big cam, if you're in manual 6th, she'll flash up and generate some crazy torque numbers pretty quickly 😊. I don't think 6th gear was designed to take 1200+Nm. 

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Yeah I understand that the issue is in the pcm, surely it can be recoded to read 6 gears tho. There can't be that many variables it uses. Probably not worth it to make it happen tho.

Haha it made 1500nm last time and will be getting another few hundred soon. I wonder if 5th and 6th gear can handle all the power tho? I reckon it can, just have to have the box tuned for it. It's just the massive heat and sustained load that scares me. I need some egt's wired into my dlp8 lol

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21 minutes ago, Puffwagon said:

I need some egt's wired into my dlp8

Plus a wideband, fuel pressure sensor, exhaust manifold pressure (back pressure), turbo speed, coolant pressure, oil pressure, oil temperature & tuner nerd knock box output. That takes you up to 14 inputs :). Might be time for a Link ECU bro. Or at the least a custom box with configurable inputs and some basic logic that can fail safe the engine. Another project???

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Pretty sure you can get a dlp20 and that would take care of it.

I'd like to stick with the stock pcm for now cos I've sunk all the credits into it. The only thing it really lacks is a proper failsafe system for mega power builds. If I can get an engine off with an oil pressure loss and a throttle closure with fuel pressure loss or a lean out then I'd be happier.

Could be another project hey. Gotta pull my finger out for the current one first lol

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