034 has had good success selling a K26/Garrett 2871 hybrid for AAN, etc applications:
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RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant -
@OT
maybe you are right but i would still not be my choice. If going with such a nexpensive turbo then go for GT3071.
Go Holset or Go RS4Comment
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My weak spot
Go Holset or Go RS4Comment
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you can avoid surge on BB turbos with proper tuning!Comment
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i didnt have any problems except 6th gear going WOT from 2500rpm. It only surged then and nothing on previous gears.
So if you can live with that, then no problem!Comment
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GT28RS surges like crazy, GT2871 surges quite a bit too with small turbine housing...
And yes, because you have to dial down the spool, there is no point to fit it.
Plus, the ballbearing turbos can not be rebuilt, KKK is known to last better... etc...
AFAIK M2.3.2 does not have gear dependent boost settings, so you need to dial down the spool in ALL gears... this was exactly what was done in Vasilis Motronic tune btw and all the GT28RS tunes I've seen.
And that makes it pointless to use the turbo. On an aftermarket ECU where you can dial in gear-dependent boost a such turbo makes more sense.Comment
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for what reason the GT28 and 3071 got surging ??? it eats too much air and our pipes are not enough?
RED Mitsubishi Lancer Evolution VI TME nº 16 of 250
BLACK Mitsubishi Lancer Evolution VI TME nº 189 of 250
LWB Audi Sport Quattro projectComment
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small turbine (impeller and housing) + ball bearings = pushing too early too much air and the engine cannot process it.
It also happens to bigger turbos with mismatched wheels/housings. look (at the boost gauge) and hear here:
Go Holset or Go RS4Comment
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RED Mitsubishi Lancer Evolution VI TME nº 16 of 250
BLACK Mitsubishi Lancer Evolution VI TME nº 189 of 250
LWB Audi Sport Quattro projectComment
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On my ecu, (VEMS) i dont run gear depended boost as it is not as refined yet. However even on the realy old firmware with megatune, immediately i was able to achieve a tremendous difference in turbo spool without surge, and i have power runs to prove it. So what i couldnt have on a motronic tune because of N75 not being able to be 'tuned' properly by not even just 1 person, i managed to achieve with an aftermarket ecu. As i said i only had slight surge on the 6th gear and that was it.This is why i mentioned that this should be achieavable on motronic as well. It shouldnt make a difference. + im not a professional tuner either.
A lot of people have had this surge issue when tuning on motronic with the BB turbos.
And also i was told that BB turbos will last even 200K kms if they are run within their maps, and there is no oil starvation to them. 200K kms without any service is good enough for everyone!Comment
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Motronic does not magically make your turbo surge. It's a purely physical process, and your engine management has nothing to do with it.
If you do not get surge on VEMS that means it's spooling slower.
That's pretty damn simple.
Reason you had horrid spool on Motronic, is because your tuner conveniently just set WGDC to 70%, and he did that everywhere for some reason, starting from 900 rpm.
Maybe because he did not know the axis values for the N75 map.
Correct way to map around surge is to set WGDC and target boost lower only in the area where there is surge, not all over the map and mess up spool. And there is no reason to set it as low as 70%... that hurts spool really badly.
In an aftermarket ECU, it would be correct to use gear-dependent boost control.
P.S.
You said you had surge at 2600 rpm. Well, in your Motronic target boost map, at 2600 RPM the target boost is max. Meaning literally "unlimited". I am sure if you do this on VEMS you will have surge too..Last edited by prj; 6 April 2011, 19:03.Comment
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i dont have to persuade you Dmitri,and as i have figured out already, i wont be able to. As i said, there were changes tried on my boost chip from different tuners as well with same results. I have no idea what they did, but the result was rediculus surge of more than 0.5bar. I suppose those tuners were useless as well according to you....
As i mentioned, car was hitting max torque and boost on motronic after 4500rpm due to the delay in boost and on vems i was having max torque @ 3500rpm on 4th gear and the boost there was 2.0bar and it was there from 3300rpm. In motronic i had about 10Nm of torque less at 3500rpm.
I put all that down to mapping and possibly inability of the motronic to be able to provide this kind of tuning. (although as i said i think its mapping alone)
Also requested boost on my old setup was:
1.3bar @ 2500
1.5bar @ 3000
1.7bar @ 3500
1.8bar @ 4000
1.95bar @ 4500
but that was merely to avoid boost spikes as boost control on megatune wasnt ideal. So i was still getting 2bar @ 3500rpm even though target was 1.7
PS: I am only posting this in the thread to say that GT BB turbos CAN work without surge, if mapped properly and KKK turbos although i like them, are not the only way.People shouldnt be discouraged from a BB turbo just because of surging, because in my case it worked brilliantly. (ok it wasnt a GT28RS or 2871 but i wouldnt put that in a I5 engine anyway. Its too small. With 2bar from 3300rpm its not excactly slow!Comment
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