[Gmecm] Tuning a larger MAF on L98

[Mike Poore]

I do have Excel and would love to look at what you have done. Unless 
Mastertune and GME label it differently, there doesn't seem to be a MAF 
table on the 85 prom. Maybe the software doesn't let you edit it. I am 
confused by some of the descriptions. My first goal is to remove the 
hesitation and see how it runs after that. Would I want to decrease the 
point at which the tps triggers full throttle? On carbs there was an 
accelerator pump. What's the equivalent on a tpi? The wide band O2 makes 
sense. You are definitely right about the ecm data being worthless for 
tuning.

Mark Romans wrote:

> Hi Mike:  Do you have excel?  I have done some work with re-scaling 
> the maf.
> I have a ported maf that flows almost 800 cfm and with that flow 
> capacity being about
> 30% greater than stock, I rescaled my maf tables by 30% and told the 
> ecm that the injectors were
> 30% smaller to compensate for the fuel side.  I also had to modify my 
> LV8 scaler.  If you are interested
> I can send you a copy of the bin and the spread sheet.
>
> I ended up having issues with leaking AIR tubes letting excess 02 into 
> the headers and throwing off my
> calibrations. So righgt now I am runnng a more stock calibration.
>
> I am running 89 software though.  Also with the 85 ecm the baud rate 
> is so slow it's impossible to see
> anything that the ecm is doing.  Even the 89 with  8192 baud is too 
> slow to catch a lot of stuff.
> The only way you will be able to tune is by using a separate wide band 
> 02 meter with datalogging.
>
> Mark
>
>
> ----- Original Message ----- From: "Mike Poore" <mp at FlowersByValerie.com>
> To: <gmecm at diy-efi.org>
> Sent: Monday, September 26, 2005 10:50 PM
> Subject: [Gmecm] Tuning a larger MAF on L98
>
>
>> I have a heavily modified 85 L98 engine. I fabricated a new MAF 
>> housing and ducting from the throttle body to the air cleaner. I 
>> removed the oem sensor from its housing and installed it in my 
>> fabricated one. I don't have the exact measurements handy, but the 
>> new MAF will flow about double the stick unit. The engine idles well, 
>> but has a severe hesitation when opening the throttle. The faster you 
>> open the throttle the worse the hesitation. Obviously, it needs more 
>> fuel, but what is the best way to compensate?
>>
>> 1. Increase fuel enrichment, or
>> 2. Modify the MAF to better reflect actual flow.
>>
>> I have Mastertune and GME for editing. I am trying to figure out what 
>> exactly I need to change to get more fuel when the throttle opens. 
>> Any advice?
>>
>> I looked at modifying the output of the MAF. My understanding is that 
>> as airflow increases, so does voltage. If the new MAF housing has 
>> fifty percent more area than old, how much do I raise the voltage? 
>> Any suggestions on how to send a voltage to the ecm that more 
>> accurately reflects air flow. Ideally, something adjustable would be 
>> great. I wish I knew more about electronic circuits because this is 
>> probably very easy. I also think that this would the better approach 
>> because it should not require so many other prom agjustments.
>>
>> Thanks for any input,
>>
>> Mike
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>
>