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Old 18-06-2012   #1
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hybrid turbo

will start this off to go with turbo strip down pic post.
what is a hybrid turbo? usually just a normal turbo that has (mostly) the compressor side modified with parts from a larger turbo, machined housing and lager compressor wheel or sometimes complete larger housing and wheel from a larger turbo.
what do you gain? airflow + reliability
a larger wheel will flow more air at the same shaft rotational speed(needed for more hp) or will flow the same air at a slower rotational speed(=more reliability), it will also be more effecient at your desired rev range if properly sized for your requirements(i went for a 52mm exducer 38.6mm inducer 55trim std was 49mm exducer 34.6mm inducer 48 or 50 trim) i think a 52mm 50 or 52 trim would have made a better daily driver maybe?
trim is best explained low trim (45-50)gives low rev torque, low surge but runs out of breath high rpm.
high trim (55-60) better flow high revs but suffers more with low rev surge
what's the downside?
turbo compressor maps help you choose compressor and trim, unfortunately not much data available for garret gt range compressors(i will post any helpfull data i found)
a larger wheel takes longer to spool up(more weight to get spinning).
too large a compressor wheel for turbine can cause boost creep, overboost etc.(a 1756 hybrid seems popular but i can still get creep on this 1752 even with a 39.5mm exducer turbine so not sure on if necessary for the 56mm comp)
boost creep is where the vnt control is fully open(mine shows 19.99%)and the actual boost keeps rising out of control this is probably too much fuel for set up.
too large a trim size can cause low rev turbo surge(damaging to turbo,)
increase in boost pressure with no turbine mods will increase emp(exhaust manifold pressure)what goes in has to come out.
when turbine becomes choke point or main restriction increase in boost mostly just increases emp and equals extra heat and less effecient.

what can be done to turbine/hot side?
most hybrids ive seen advertised have modified turbine wheel described as cut back, as i understand it this is the machining of the wheel itself on the exducer.
the wheel is cut back o reduce the efficency of the turbine itself, by removing some fin area at the exducer the turbine becomes less restrictive this is helpful to reduce the emp and boost creep described above.
the turbine is now less efficient ,spools slower, spins at a slower shaft speed for same given mass airflow, this is not all doom and gloom as these are vnt turbos.
the ecu can and should recalculate less vnt opening to get back turbo boost presure under control.so say 25% vnt gave 2500mb a cut back wheel may need 35% to get 2500mb, but larger comp wheel is flowing more anyway so vnt % may be not much different.
in my set up i went for a completely larger turbine wheel from another vnt17 turbo, i think it was the largest available exducer 39.5mm with a 43mm inducer.
this required a lot of guesswork, assumptions and machining work which i assume is why turbo builers just do cut back wheels.
i have been holding off for a while till i have run in turbo and tested on the car.im pretty pleased with how it performs, but realistically the time cost and effort put into making this hybrid would have gone a fair way to buying a much better complete turbo aka gtb1756 or gtb2056 or gtb2260 and modifing exhaust manifold and downpipe, oilpipes etc.
i will ask to keep this thread clear for a day or so , so i can finish downloading related pics and data etc.
thanks
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Last edited by sussexa; 18-06-2012 at 22:43.
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Old 19-06-2012   #2
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Re: hybrid turbo

Are you running a vnt on a petrol engine?
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Old 19-06-2012   #3
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Re: hybrid turbo

tech porn... Love it
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Old 19-06-2012   #4
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Re: hybrid turbo

this is all based on the garrett gt1749v 777250-1 which is the latest model that replaces others fitted to the jtd 16v (and some alfa's also) i measured up and compared sizes to my turbo when removed and it was all the same dimensionally.

here is a larger 52mm comp wheel next to a 49mm comp wheel, notice the different back design to the new wheel, (to make things easier get the right back design, a spacer sorted it though)
Click image for larger version

Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 new compressor 002.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 new compressor 005.jpg
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here is the larger turbine fitted untouched with no cutback(hopefully more flow without loss of turbine efficiency)
Click image for larger version

Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 new turbine 001.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 new turbine 002.jpg
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if you look at my old turbine i had a quick go at performing a cut back with a dremel and a stone with turbine rotating at high speed also, you can see the exducer blade angle is much steeper.
there are several pieces that then need machining accurately, i measured up all original parts and came up with around a housing diameter 1.00mm bigger than the comp and turbine wheel diameter, so with wheels in place there is 0.5mm clearance to the housing from the wheel.
i read up a lot about custom turbos being machined to finer tolerances but with a dry new bearing there is a few tenths of a mm movement on the shaft.
im struggling with internet connections and uploading so please bear with me i will upload all relevant pictures or videos i have(eventually)
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Last edited by sussexa; 19-06-2012 at 15:31.
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Old 19-06-2012   #5
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Re: hybrid turbo

here is the flow path in the 16v turbo into the vnt area, i found that there is a slight step reducing the actual flow area to less than that of the vnt vane height shown by the height of the vnt ring spacer.
Click image for larger version

Name:	new  <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 2011 before hybrid diy cutback 3 009.jpg
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Name:	new  <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 2011 before hybrid diy cutback 3 014.jpg
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this was opened up to the full height of the vnt spacer (hopefully removing a small restriction)
Click image for larger version

Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> porting idea.JPG
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im not sure what pro turbo tuners do internally to there turbos but most list some internal efficiency mods no idea what they are.
the original manifold and turbine housing was also ported to remove any steps or lips by making a temporary gasket and gasket matching both ports.
the turbine housing is also part of the major restriction, no point putting a bigger turbine in there than what the housing can flow. i think the 8v turbo actually has a higher flowing turbine housing, but smaller vnt vane height.

will try after 6 its taking forever to upload pics
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Last edited by sussexa; 19-06-2012 at 16:14.
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Old 19-06-2012   #6
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Re: hybrid turbo

Click image for larger version

Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 strip down 2011 001.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 strip down 2011 011.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 strip down 2011 014.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 radius and polished for 52 wheel 001.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 radius and polished for 52 wheel 002.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 radius and polished for 52 wheel 004.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 radius and polished for 52 wheel 007.jpg
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Old 19-06-2012   #7
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Re: hybrid turbo

Click image for larger version

Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 bored out for new wheels 001.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 bored out for new wheels 002.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 bored out for new wheels 004.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 bored out for new wheels 005.jpg
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Name:	 <a href='http://www.fiatforum.com/autolink.php?id=31&script=showthread&forumid=33' target='_blank' class='gal'>turbo</a> 777250-1 bored out for new wheels 006.jpg
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some data i used to guess my sizes
idea of extra flow capabilities of slightly larger turbine
http://www.theboombopshop.com/v/vspf...t/GT1548-T.jpg
http://www.theboombopshop.com/v/vspf...t/GT1544-T.jpg

some 52mm compressor maps i used at the time(not ideal but o.k. to compare trim on flow capabilities)
48 trim
http://www.theboombopshop.com/v/vspf...T2052-48-C.jpg
50 trim
http://www.theboombopshop.com/v/vspf...T2052-50-C.jpg
52 trim
http://www.theboombopshop.com/v/vspf...T2052-52-C.jpg
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Old 19-06-2012   #8
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Re: hybrid turbo

a helpful site to work out what airflow you will need with your hardware and desired outputs is
http://www.turbobygarrett.com/turbobygarrett/webadviser
when inputed my wish list i got a figure of approx 230hp @ 27psi would require 24lbs/min of air. this ultimately gave the go ahead for a hybrid over complete turbo although this value is closer to a 56mm compressor so i dropped my target hp slightly.
heres another online calculator
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml

of course the final part of the rebuild was new bearings (the std turbo already has a 360* thrust bearing, as many hybrids advertise as extra)and assembly and i requested a staggered gap piston seal on turbine(supposed to help on low back pressure exhaust systems) and most important is the turbo balancing. i would not recommend refitting a rebuilt turbo that has not been professionally balanced(just remember it may be spinning at 180,000rpm or more)
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Last edited by sussexa; 19-06-2012 at 22:02.
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Old 19-06-2012   #9
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Re: hybrid turbo

i would recomend for the work fitting something like this instead better gtb vnt3 turbos
this guys a regular on tdi forum
http://www.darksidedevelopments.co.u...onversion.html
if you fancy a read and some real turbo p*rn take a look on here
http://forums.tdiclub.com/showthread.php?t=313001
click on ryanp and see more posts
heres a chart i think he knocked up(for tdi engines)
http://i1219.photobucket.com/albums/...Comparison.jpg

http://i1219.photobucket.com/albums/...omparison2.jpg
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Last edited by sussexa; 19-06-2012 at 21:08.
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Old 19-06-2012   #10
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Re: hybrid turbo

looking through my old data logs this(hopefully) shows pretty clearly, that the std turbos can easily be overspeeded(by overfuelling)and then are in boost creep
std turbo is on the right, just look at the boost curve in the middle brown =desired boost, light blue = actual boost and purple= vnt %
at max desired boost the actual boost just keeps rising, vnt hits min value 19.99% and turbo is out of control , more fuel = more boost = turbo overspeed =

now look at the new turbo, much better control still a small overboost but vnt only hit 30% .also you can see on the off throttle that the boost drops quicker thanks to larger turbine.
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Old 19-06-2012   #11
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Re: hybrid turbo

even managed to find one where i was still just out on new turbo, i have raised boost again from here and raised it higher in the rev range also where it dropped off quickly in desired.

hope this all helps someone in the future.
anyone doing anything like this i would recommend at least a seperate turbo boost gauge, a exhaust temperature gauge , exhaust manifold pressure gauge or at least to log these things properly during set up.
i think a lower trim 52mm wheel and no turbine mods would suffice for 99% of set ups where just a remap is done, and plenty of guys run decent hp with the std turbos anyway.
the whole thing started when i was 99% sure my old turbo was weeping oil on turbine seal(probably due to decat and some massive overboosting over the last few years)i just couldnt do swapping like for like.
lastly it took me a long time to complete, buying a spare, research , buying parts, machining of housings(if i had had to pay for machining id have probably bought one done) ,porting,polishing etc.if tinkering is not your thing buy one done properly(even the turbo guys who balanced my unit could not give any guarantee on the turbo as they had not done all the work plus there was no proof parts would all run o.k together, i understood this and accepted it, there was a few sweaty moments when i ran in anger for the first few times)
i have no idea how long it will last reliability wise, ill post back up if it doesnt
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Old 19-06-2012   #12
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Re: hybrid turbo

in the words of the late great Pacman

wakka wakka wakka wakka...


need more nuggety turbo info

@sussexa
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Old 20-06-2012   #13
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Re: hybrid turbo

as i said before: are you running VNT with petrol engine??
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Old 20-06-2012   #14
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Re: hybrid turbo

Quote Originally Posted by shakey_hand_man View Post
as i said before: are you running VNT with petrol engine??
Check out his second post.

Quote Originally Posted by sussexa View Post
this is all based on the garrett gt1749v 777250-1 which is the latest model that replaces others fitted to the jtd 16v
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Old 20-06-2012   #15
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Re: hybrid turbo

Quote Originally Posted by Shadeyman View Post
Check out his second post.
saw that... Way it was phrased, was unsure if he had taken it from a JTD..
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