Carpokes Porsche Forum

Tom,
My 86 turbo is totally stock except venturi delete. I don’t have a wideband or boost controller but would be willing to add both as I was already considering a manual boost controller. Recommendations on both would be appreciated.
Let me know.
Lee

Tom wrote: Wed Dec 10, 2025 8:05 am This reminds me, I'd like to find a volunteer or three to test out my baseline performance chip for the 951. Only catch is we'd need a stock car with wideband (and preferably a boost controller) so we can log the AFR and fine tune as needed. If you have or know of anyone with a stock 951 who might be interested, please let me know! I'd supply the chips for free, and dial them in based on the wideband logs. I'll even throw in a pre-wired knock counter to add more data to the mix and make it worth you while!

PM sent!

I have an 88 turbo S that is stock except for a turbo back exhaust, not sure if that could be helpful to you

I don't have a wideband O2 sensor or boost controller, but have been planning on installing a wideband O2

I have a 1987 Turbo. Almost completely stock, except for an aftermarket BOV. I have added shims to the waste gate as per Clarks garage. I have a wideband sensor and gauge that I will be installing shortly after Xmas. I don't have a boost controller though, nor does it have a catalytic converter.
Even though I am in Australia, I purchased the car in England in 1993, so not sure how that would affect things.

markagsmith5 wrote: Tue Dec 16, 2025 6:47 pm I have a 1987 Turbo. Almost completely stock, except for an aftermarket BOV. I have added shims to the waste gate as per Clarks garage. I have a wideband sensor and gauge that I will be installing shortly after Xmas. I don't have a boost controller though, nor does it have a catalytic converter.
Even though I am in Australia, I purchased the car in England in 1993, so not sure how that would affect things.

Did your car come with the cat originally? There are 4 different set of maps (not all maps but most part throttle timing and fuel maps) for different regions, with the biggest differences being cat/o2 equipped vs non cat/o2 equipped cars.

@Tom I'm not sure if you covered this in your tuning guide but it's on my list to explain how all this works. I can bump it up to the top if it's useful. Basically a car that was delivered without the O2 sensor will select different part throttle fuel maps. It's controlled by the plug that normally connects to the altimeter in US cars. Non cat/o2 cars have a 1.8K resistor instead of the altimeter, and that makes them select different maps.

Never had a cat from new.

johnb wrote: Tue Dec 16, 2025 6:55 pm

markagsmith5 wrote: Tue Dec 16, 2025 6:47 pm I have a 1987 Turbo. Almost completely stock, except for an aftermarket BOV. I have added shims to the waste gate as per Clarks garage. I have a wideband sensor and gauge that I will be installing shortly after Xmas. I don't have a boost controller though, nor does it have a catalytic converter.
Even though I am in Australia, I purchased the car in England in 1993, so not sure how that would affect things.

Did your car come with the cat originally? There are 4 different set of maps (not all maps but most part throttle timing and fuel maps) for different regions, with the biggest differences being cat/o2 equipped vs non cat/o2 equipped cars.

@Tom I'm not sure if you covered this in your tuning guide but it's on my list to explain how all this works. I can bump it up to the top if it's useful. Basically a car that was delivered without the O2 sensor will select different part throttle fuel maps. It's controlled by the plug that normally connects to the altimeter in US cars. Non cat/o2 cars have a 1.8K resistor instead of the altimeter, and that makes them select different maps.

Sent you a PM, but would love to finally get to the bottom of all that, including the mysterious California/Japan 'maps' ...

Happy to send a chip to Australia too, though probably best to do some basic testing locally first...

Hi Folks - my side project building a software simulator for the DME system is showing signs of life - I'm able to load a bin file and run the code, observing the main outputs (injectors, ignition, ICV, dme relay, tach), but what I don't have is a set of input conditions that are valid.

So - if any of you have static (single datapoint) or log data showing the following for a well running 1986 or 1989 turbo, it will help validate the simulator results:
RPM
AFM (2 sensors - DME pin 7 and DME pin 22)
Batt_Voltage
AFM_NTC temp
Coolant_NTC temp
ADC_Data_Field
ADC_Ch5
TPS
FQS
AFR

Thanks!
Mike

whalenlg wrote: Tue Feb 03, 2026 6:09 pm Hi Folks - my side project building a software simulator for the DME system is showing signs of life - I'm able to load a bin file and run the code, observing the main outputs (injectors, ignition, ICV, dme relay, tach), but what I don't have is a set of input conditions that are valid.

So - if any of you have static (single datapoint) or log data showing the following for a well running 1986 or 1989 turbo, it will help validate the simulator results:
RPM
AFM (2 sensors - DME pin 7 and DME pin 22)
Batt_Voltage
AFM_NTC temp
Coolant_NTC temp
ADC_Data_Field
ADC_Ch5
TPS
FQS
AFR

Thanks!
Mike

Not sure what you mean by single datapoint? What would that mean with respect to the RPM input for example?

whalenlg wrote: Tue Feb 03, 2026 6:09 pm Hi Folks - my side project building a software simulator for the DME system is showing signs of life - I'm able to load a bin file and run the code, observing the main outputs (injectors, ignition, ICV, dme relay, tach), but what I don't have is a set of input conditions that are valid.

So - if any of you have static (single datapoint) or log data showing the following for a well running 1986 or 1989 turbo, it will help validate the simulator results:
RPM
AFM (2 sensors - DME pin 7 and DME pin 22)
Batt_Voltage
AFM_NTC temp
Coolant_NTC temp
ADC_Data_Field
ADC_Ch5
TPS
FQS
AFR

Thanks!
Mike

This is really cool! I'm looking forward to seeing outputs from the real code.

I have an opened up DME hook up in my car at the moment. It's a busy time for me but if you have a specific request (4 channels max) I should be able to grab something for you over the next week or two. It would probably have to be non-moving though, so idle or snap throttle (we're buried in snow where I live).

Here's a puzzle that your simulation might be able to shed some light on at some point:
This map is stored at 1140. It's actually 2 maps (split in half).

These maps modulate the fuel pulse (the value on the vertical scale is a multiplier, so a value of 1 does nothing).

This graph doesn't quite show the raw maps - I've done some processing to show the effect they have on the fuel pulse width.

They are a bit of a mystery to me because the circumstances under which they are applied are complicated and confusing. As far as I can tell:

* they're applied when fuel is re-activated after cut-off
* the first one (0-15) is applied upon return-to-idle
* the second one (16-31) is applied on return-to-throttle

As you can see from the graph the first one dithers the fuel pulse width above and below it's normal value briefly; the second one pulls it down before gradually climbing back up.

They are applied in the real-time part of the code, just after the spark timing is calculated, and thus they override all closed loop control.

I just don't know why these are there. Some ideas I had:

* it has to do with the catalytic converter
* something to do with fuel vapor purge

I don't think it's the cat because most cat/o2 related code is guarded by the code plug stuff. This code is active for all models.