Tweecer question

leon_reynolds · Sep 30, 2005

I have already posted this on the yahoo tweecer group, but thought I would try here also as there is alot of people that are familiar with the product........I have recently upgraded my 89gt with 42#injectors and an 80mm pro-m calibrated for 7 psi. Once I completed the install the car wouldnt start unless under wot. I assumed it was getting way to much fuel and purchased the tweecer to adjust to these and previous changes. I just got it in and tried it for the first time....I changed my maf to the preset 80mm in the program, and adjusted the injector slope to 42 high and 50 low. I saved it to the tweecer and tried to start.....same thing. Need to know what else I should do besides pull my hair out. THanks in advance for any advice you may have.

HISSIN50 · Sep 30, 2005

With the TwEECer, cant you dial back the cranking fuel? I seem to recall guys talking about that.

Good luck with it.

MatthewP · Oct 1, 2005

Obviously your 80mm MAF is not calibrated for 42# injectors, or the car would have started ok on the stock A9L (assuming your a 5 speed car)programming. Your Pro-M meter will probably have the injector calibration scribed onto the electronics. Look for a "19", "24", "30" or some other injector size scribed on the black electronics. If it says 19, try the stock MAF curve with the injector size set as you already have it. If it's 24, shift the entire stock MAF curve higher by 24/19 (26% higher), etc.

Good luck.

-Matthew

leon_reynolds · Oct 2, 2005

Well that is what I have been feeling all along. Why would you pay to have a maf setup for your calibration if it wouldnt work with your stock system. That just doesnt make sense. I have gone through the engine, ran codes and everything checks out good. I just have a very rich system according to the tweecer. My injector pulswidth is way too high.....up to 10 and 15 at certain moments and then back down to 3and 4. Has anyone out there done a similar upgrade and been able to run without a tune? Or is it normal for this to happen? Any advice you may have will be greatly appreciated.

Michael Yount · Oct 2, 2005

Do you have the multi-point voltage vs. mass transfer curve for your meter? If so, you need to use the Tweecer to load your meter's actual transfer curve into the ecu. If not, you need to obtain the meter's actual transfer curve (ProM might be able to help if you have a serial number) - and load it into the ecu. Then simply use the tweecer to tell the ecu what size injectors you're running.

That should help tremendously -- you may still have to pull starting fuel with those injectors -- but there should be a table that makes that relatively easy.

MatthewP · Oct 2, 2005

Michael is right. If you have the flow sheet that would have shipped with the meter originally, load that curve into the tweecer. I was assuming that you don't have it.

Another problem that sometimes affects these cars at idle or part throttle is a pressure surge from the bypass system on the supercharger. If the return is too close to the MAF, it can generate false and fluctuating reading on the meter. The solution is to plumb the return in as far away from the meter as possible, and use as big of a bypass line/valve as possible.

Good luck.

-Matthew

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