Bigger turbo, less fuel
07-01-2005, 11:55 AM
#1
Three Wheelin'
Thread Starter
Bigger turbo, less fuel
So far I have gone from a k26/6, to a k27/6, to a super 61, and with each step I needed to decrease the amount of fuel throughout the entire range. I was expecting the opposite, even though the compressor is more efficient, I would have expected with the additional HP more fuel would be needed. I’ve needed to decrease up to 22% fuel in some zones, with the MAFBURNER and a wide band. I can understand less fuel in the lower zones due to the bigger turbine, but not in the higher zones approaching 5500 RPM, and this is using the APE MAF chips for a k26.
Anyone else notice this?
I cut the APE J pipe that steps down from 3” to 2.25” to fit the larger compressor inlet so it would have no step down. Anyone know if that would somehow change the MAF calibration?
Anyone else notice this?
I cut the APE J pipe that steps down from 3” to 2.25” to fit the larger compressor inlet so it would have no step down. Anyone know if that would somehow change the MAF calibration?
07-01-2005, 12:00 PM
#2
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The MAF calibration should not be affected by modifying the J-pipe. Now if you modify the MAF sensor itself, then you can see some changes..
Did you increase the njector size or fuel pressure? Running a super 61 with the stock injectors & chips for them will cause a lean condition.
There is a possibility (you will have to check), if you are maxing out the MAF in the early RPMs then all sort of things can happen.
Did you increase the njector size or fuel pressure? Running a super 61 with the stock injectors & chips for them will cause a lean condition.
There is a possibility (you will have to check), if you are maxing out the MAF in the early RPMs then all sort of things can happen.
07-01-2005, 12:14 PM
#4
Three Wheelin'
Thread Starter
No, the MAF is not maxing out. It's measuring 4.14V at the highest point, and I believe it goes up to 5v.
Injectors are still stock and I haven’t increased the fuel pressure since the k26, but it was raised back in the day to about 3bar.
I'm only running 15lbs on this turbo for now, but ran 16-17 on the k27 and was rich then too. Strange.
Injectors are still stock and I haven’t increased the fuel pressure since the k26, but it was raised back in the day to about 3bar.
I'm only running 15lbs on this turbo for now, but ran 16-17 on the k27 and was rich then too. Strange.
07-01-2005, 12:20 PM
#5
Yeah man - I was cringing reading that. Your DME is probably dumping a bunch of fuel in there because it is confused.
That is a very large gap to try to fill with an MAF tuner.....
That is a very large gap to try to fill with an MAF tuner.....
07-01-2005, 12:40 PM
#6
Three Wheelin'
Thread Starter
Special, like I mentioned I don't think the MAF has maxed out, the datalog file reads 4.14v at the highest point with this turbo at 15lbs. 4.4v with the k27 at 17lbs.
I'm assuming the APE MAF goes up to 5V, anyone know for sure.
I'm assuming the APE MAF goes up to 5V, anyone know for sure.
07-01-2005, 12:44 PM
#7
I can tell you that the APE MAF is only calibrated for 400 crank HP (340 RWHP+/-).
I blew some serious wind through mine, and never saw above 92%(4.6)
That turbo you have will make more power than 340 RWHP.
I blew some serious wind through mine, and never saw above 92%(4.6)
That turbo you have will make more power than 340 RWHP.
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07-01-2005, 12:45 PM
#8
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If you are running the chips designed for a K26 and a 2.5bar FPR, going to a 3bar will give you an additional ~+9% more fuel. The K26 spools up sooner than the Super61, so before boost kicks in you will run richer. Once you hit boost, you will need more fuel, but with the additional 9% and the fact that APE chips run rich in the mid-range you might be ok, but at the top-end you will be running lean, unless your are not holding 15psi boost to redline.
I think you will start to see lean condition if you up the boost some. Regardless, it's a good idea to use a wideband (if not already using it), and log RPM/AFR to monitor closely.
Of course, you still have the timing to deal with. The torque curve of the K26 is different than the larger turbos..
I think you will start to see lean condition if you up the boost some. Regardless, it's a good idea to use a wideband (if not already using it), and log RPM/AFR to monitor closely.
Of course, you still have the timing to deal with. The torque curve of the K26 is different than the larger turbos..
07-01-2005, 12:59 PM
#10
Three Wheelin'
Thread Starter
Well, that's the strange thing, it's rich at the top end too. I've datalogged RPM,AFR,Vin,Vout,TPS, and the rest of the usual stuff with a wideband.
The car runs strong, I just can't imagine why I needed to back off 20+% in fuel.
What would 1 tooth off on the timming belt do in terms of cam timming and AFR? Not sure if I was off, but it's hard to judge TDC when there is no mark on the fidenza flywheel.
The car runs strong, I just can't imagine why I needed to back off 20+% in fuel.
What would 1 tooth off on the timming belt do in terms of cam timming and AFR? Not sure if I was off, but it's hard to judge TDC when there is no mark on the fidenza flywheel.
07-01-2005, 01:34 PM
#12
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Wormhole,
I'll bet it has something to do with the fact that you even have a Mafburner connected into the system.
As I understand, the APE Maf doesn't need any injector pulse width adjustment devices. As long as you don't change injector size, this Maf will measure the molecules of air, and via the chip, will dispense the proper injector duty cycles (irregardless if there was a change in air flow mods).
If it was me, to satisfy my curiosity, I would take the Mafburner out. Then see how/and if the AFR ratio changes (with your wideband) when running different boost levels.
I'll bet it has something to do with the fact that you even have a Mafburner connected into the system.
As I understand, the APE Maf doesn't need any injector pulse width adjustment devices. As long as you don't change injector size, this Maf will measure the molecules of air, and via the chip, will dispense the proper injector duty cycles (irregardless if there was a change in air flow mods).
If it was me, to satisfy my curiosity, I would take the Mafburner out. Then see how/and if the AFR ratio changes (with your wideband) when running different boost levels.
07-01-2005, 02:35 PM
#13
Three Wheelin'
Thread Starter
Well the mafburner doesn’t necessarily change the injector pulse directly; it adjusts the hot wire volt that is sent to the DME. By default the mafburner is set to zero change, Vin=Vout, adjustments can be made up or down, so I don’t see how it could be the culprit. Plus, I’m datalogging with the mafburner, so if I were to remove it I wouldn’t be able to monitor AF.
