MAF Piggyback Owners – Pay Attention
02-26-2006, 12:53 AM
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MAF Piggyback Owners – Pay Attention
Piggyback owners – pay attention
I dynoed my 951 Turbo track car today for FIVE hours due to a problem that we finally identified. Let me first provide some history.
I started driving this car three years ago and have run it thirty weekends. The first two years were with stock engine and ancillaries except for a boost controller. Last year I installed a MAF and MAFtuner piggyback , still with the stock turbo. I dynoed the car to adjust air/fuel ratio and ran great all year but did destroy two stock turbos.
Last month I installed a water cooled K27/8 with Garrett center section, purchased from a Rennlister last June. I dynoed the car a couple of weeks ago but had tuning problems. A run would be going good and suddenly, in the middle of acceleration, the A/F ratio would go completely rich or one run would be good and then the next run the A/F ratio would go rich and would stay that way, even at idle! Also, the turbo was filling the intake with oil. I quit without success. I sent the turbo for rebuild and got it back together Thursday.
Today – the same tuning problem!!! I even removed the DME and KLR with Kokeln chips thinking that may be the problem since I they were installed at the time of turbo upgrade. I installed spare computers with stock chips. Same problem.
A friend was with me and we were discussing how the Porsche DME functioned. Well, thanks to my Rennlist education, I knew that the DME didn’t use the O2 sensor at WOT and that the DME would use a pre-programmed map if there was an O2 sensor fault. So I disconnected the sensor and the runs became consistent. The O2 sensor is intermittent or possibly clogged due to running richer than designed. BTW, the wideband O2 sensor for the Zeitronix datalogger is functioning fine. I got the A/F ratio dialed in and am ready to attach California Speedway in two weeks.
SO, those of you running rich enough to possibly clog the stock O2 sensor, you may want to disconnect it before your next tuning session and recalibrate A/F ratio without it.
I dynoed my 951 Turbo track car today for FIVE hours due to a problem that we finally identified. Let me first provide some history.
I started driving this car three years ago and have run it thirty weekends. The first two years were with stock engine and ancillaries except for a boost controller. Last year I installed a MAF and MAFtuner piggyback , still with the stock turbo. I dynoed the car to adjust air/fuel ratio and ran great all year but did destroy two stock turbos.
Last month I installed a water cooled K27/8 with Garrett center section, purchased from a Rennlister last June. I dynoed the car a couple of weeks ago but had tuning problems. A run would be going good and suddenly, in the middle of acceleration, the A/F ratio would go completely rich or one run would be good and then the next run the A/F ratio would go rich and would stay that way, even at idle! Also, the turbo was filling the intake with oil. I quit without success. I sent the turbo for rebuild and got it back together Thursday.
Today – the same tuning problem!!! I even removed the DME and KLR with Kokeln chips thinking that may be the problem since I they were installed at the time of turbo upgrade. I installed spare computers with stock chips. Same problem.
A friend was with me and we were discussing how the Porsche DME functioned. Well, thanks to my Rennlist education, I knew that the DME didn’t use the O2 sensor at WOT and that the DME would use a pre-programmed map if there was an O2 sensor fault. So I disconnected the sensor and the runs became consistent. The O2 sensor is intermittent or possibly clogged due to running richer than designed. BTW, the wideband O2 sensor for the Zeitronix datalogger is functioning fine. I got the A/F ratio dialed in and am ready to attach California Speedway in two weeks.
SO, those of you running rich enough to possibly clog the stock O2 sensor, you may want to disconnect it before your next tuning session and recalibrate A/F ratio without it.
02-26-2006, 05:00 AM
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Claus, I'm so sorry I missed the Dyno this morning, I got up and went straight to installing my MAF and piggy back. (I geuss I'm kinda excited to get em in) and totally forgot that today was the dyno! I hope you don't think I'm to much of a flake!
02-26-2006, 10:15 AM
#3
Three Wheelin'
Claus, I had the same problem with my N/A. I had such a large cam in it that the only way i could get to run at idle was to have it rich. I ruined 2 O2 sensors in less than 18 months. After the second one I just disconected the o2 sensor and tuned the car without it.
02-26-2006, 10:40 AM
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So you tuned the car without your O2 connected. I can understand that, but what about when you reconnect the O2 and start driving again? Won't you still have problems assuming you do not replace the O2 immediately?
02-26-2006, 12:44 PM
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Ive had mine unhooked for about 6 months.Runs much better without it.My zietronix has a narrow band output I was thinking of hooking up that to the DME to see how that works.
Erik
Erik
02-26-2006, 01:15 PM
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Originally Posted by danny951
So you tuned the car without your O2 connected. I can understand that, but what about when you reconnect the O2 and start driving again? Won't you still have problems assuming you do not replace the O2 immediately?
A track car needs a richer A/F ratio to make maximum horsepower and to not detonate. I loose the fine tuning that the O2 sensor provides when atmospheric conditions change but gain consistancy and repeatability.
The next time that I go to the dynomometer, I'll install a new sensor and make a run with it to see what the difference is.
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02-26-2006, 05:31 PM
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I connected the narrowbad output from my innovative to the DME, saving me a new o2 sensor, the car ran a lot smoother on idle/part throttle.
02-26-2006, 10:58 PM
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yes i found disconnecting the stock o2 sensor makes tuning your idle and PT much much easier, stops the closed loop behaviour jumping around all over the PT map, trying and compensate for poor fuel maps or transfer function. 14.7 is seen by the DME when the o2 is disconnected. Closed loop needs a stable, consistent tune across various zones to work effectively.
