brad-cam

I put my old Guru DME chip back in today, with Siemens 55 lb/hr injectors (p/n 3102) and set the FQS switch to position 1 (remembering that Guru remaps the FQS switch to select different injector sizes). The engine wouldn't idle worth a crap, and stumbled when I rev'd it. I was sure I had introduced a huge vacuum leak somewhere.

But, when I set the FQS switch back to position 0 (stock) it ran perfectly !! Knowing that it was probably running rich now I swapped the stock injectors back in and it still runs perfectly.

So, mystery, why doesn't the Guru chip work as advertised with the FQS settting and 55 lb injectors ? Has anyone else had issues with this ?

No need to start a "Guru chips are junk" thread, I run Vitesse normally - this is temporary.

brad-cam

Searched harder and I think I found my answer:

https://rennlist.com/forums/showthre...t=Guru+Siemens

Siemens 55's have lower fuel delivery at partial duty-cycle compared to Delphi injectors and Danno calibrated to the Delphi's, so looks like I was running too lean at FQS setting #1.

eniac

Don't know if this helps but Danno is still around. The other day I got a suprising email from him. Granted this was a response to an email I sent 4 months ago but I still appreciate he took the time to respond while noting he placed the email aside then forgot. You can try emailing him, if you indeed get a quick response back I would also suggest buying a lottery ticket.

Thom

Question along the same lines : will Guru or MAXhp chips work with Siemens #83 lbs ? At which FQS setting ?
Thx

brad-cam

Opening back up this thread that I started two years ago and never really got to the bottom of IMHO, and researching this a bit more, it occurred to me that the testing I did was at idle and part throttle, thus in closed loop, and should the DME not have compensated for inaccuracies in the fuel map ? With FQS 0, tuned for the stock 34 lb injectors, it seemed to run ok with the 55 lb injectors, suggesting that the DME was doing it's thing in closed loop, but not when the FQS was set to position 1 for some reason... strange.

Question, does anyone know if the SMT6 piggyback has the range to compensate the fuel map to run 55's on a stock 34 lb injector setting, both for closed loop and open loop (WOT) ? Do any of you have a SMT6 map for such a setup ?

BTW, the 55's are running sweet with my Vitesse MAF and chipboard combo (thanks John!).