13-04-2012, 04:08 PM
Ruan Wrote:The HDi one seems pretty restrictive, whenever I've put ANYTHING on the turbo of my car, it pulls power down...
I'd be very interested to see some results from a HDi with no intake system at all, simply turbo to air... And yeah, the MAF is a ballache... Is there no way on these to convert to MAP based and go without a MAF - putting a bigger one on involves recalibration, sure it's not ideal as far as economy and precision metering goes, but for stage 2+? IIRC I remember someone saying they're WAY out of their range past about 130hp, so apart from idle and cruising, they're pretty pointless anyway?
Or am I barking up the wrong tree?
Yeah the pipe running from MAF > turbo might not be ideal. I can't say it's gonna be THAT bad though. At speed the OEM system should be in almost positive pressure due to the ram air intake effect. I've never checked, but lets say it evens out the intake drag losses we should hopefully not have to worry about the intake at all.
To run something different would be a risk, you are much more likely to make something worse than better unless you have lots of test equipment and are happy to go back to the drawing board a lot, and have the engine half out a lot
Yeah, people can run MAP rather than MAF for smoke control. I'm assuming there is a good reason for running MAF vs MAP though...
I'm not certain, but running off MAF means the air is measured before the turbo so before the feedback loop system, while MAP is run post turbo... so perhaps you become more at the mercy of the turbo responding before you move 'up' the smoke map?! Maybe it makes steady state smoke tuning harder, but in return you get better response tuning for getting onto boost?!
The standard MAF seems to run enough for loads of fuelling mid-range for torque, but yes, as revs rise you are limited and that means limited power.
The thing is, you may as well just tune the smoke map to be clean till the last step, then on the last step adjust it for max fuelling you want, and adjust the mapping accordingly. The time you will ever end up in that window where the smoke map isn't perfect will be fairly damn narrow. The MAF will 'read' for maybe 160bhp nicely, but it'll 'flow' enough air for probably double that power if you really wanted it to
It'd just be a restriction rather than a useful air meter at that point though
I don't have my laptop going now but I've got loads of plots of actual MAF readings vs rpm, both g/s and mm.3/stroke, and I'm fairly certain that an FMIC is still giving 'nice' MAF readings at 150bhp... it might just be getting out of range, maybe at 140bhp, but since the smoke map itself is so granular anyway, the last step takes you from enough flow from 140-150bhp anyway (ie, as above you'd never notice the point where good metering ended as you'd never be there except at FULL throttle at near 4000rpm)
I'd say just with a good hybrid (the right one, matched specifically for the peaks you wanted, not pie in the sky 'future dreams' outputs), you could land yourself with 180bhp/275lbft at 4000rpm/2500rpm respectively. So just a normal HDi with a good clutch and FMIC, and the right turbo of course.
Beyond that your HP pump is struggling as much as the MAF sensor is at doing nice metering. Your injectors are open a long time at high rpm (not ideal), so they are struggling and would be best being opened for less time with more rail pressure, so running an upgraded sensor.
150bhp is about the standard limit with fmic.
No one seems to be going to what is obviously the next bottleneck, the turbo. That takes you to about 180bhp I'd say.
Then it's onto the whole 'stage 3 (probably should be stg4 really?)' where you go for pump, rail sensor, injector tips maybe, even bigger turbo specs etc.
Gah, I so want a HDi to tinker with again... first job would be FMIC and then set my sights for the 'new' stage3, a properly matched turbo and 180/275 outputs on otherwise standard bits
Dave