Yet Another Turbo Thread

[Drift Motorsport]

There's heaps of BS in this thread that needs some clearing up.

The T04Z is built on a GT40 core. I'ts marketed as a T04Z due to the unique compressor design which has curved fins instead of straight fins. This makes the compressor slightly inefficient - but you can flow more at higher shaft speeds and pressure ratios. Its similar to back cutting the rear turbine wheel for more flow. The efficientcy is still in the 70-76% which is the sweet spot. Operating at 70 instead of 76 will slightly heat up the air more due to the compressor's friction with the air. For a setup with an intercooler - it will be able to cope with this no problem. There is NOTHING old about the T04Z design. It was built by HKS to flow heaps of air at high pressure ratios. The GT4088 is based on a SCANIA 9LT DIESEL truck turbo. Garrett/Allied Signal supply these turbos with a 27psi internal gate for SCANIA trucks. They flow around 650HP in their truck format but have a really peaky compressor map. The Garrett GT4088 that you buy for your street car has a slightly different trim to make it flow at lower flow rates and high pressure ratios. This is done so that the turbo does not surge. Since a Diesel doesn't have a throttle body - surge isnt so much of a problem so a peaky turbo is OK.

The T04Z is between the GT4088 and GT4092. The GT4092 flows 80lb/s but it would be a LAG monster compared to the T04Z due to its huge turbine and compressor wheels. The T04Z is probably the most streetable large frame turbo - when matched with the right A/R. A 1.00 housing on the rear on an RB30 is very responsive and has a lot of torque. Off boost response is quite good and once it spools - it will power slide.

The T04Z comp wheel FLOWS MORE than the GT4088 across the whole map.. At its peak - the T04Z will flow ~73lb/s at 2.25 Bar. The GT4088 will flow 67lb/s at 1.4 bar. The T04Z at 1.4bar flows 69lb/s. This is largly due to the larger inducer on the T04Z (66.65mm) vs the GT4088 (63.5mm). The T04Z also has a larger trim size, which is the most important part of the compressor and turbine geometry. This is the relationship between inducer and exducer. The larger the trim size - the more flow you will have through the housing outlet.

Trim = ((inducer)^2 / (exducer)^2 )* 100

The benefit of the T04Z over the GT4088 is that it only needs 30lb/s exhaust flow - compared to the same A/R GT4088 which needs 33lb/s (.84 ar on both). This will mean that the T04Z will be less laggy than the GT4088 if you are using the same housing. You also need a faster shaft speed on the T04Z to make the boost - hence why the smaller wheels and trims on the exhaust side. This helps the turbo spool up much faster due to the high shaft speeds required.

The only reason why a GT4088 may appear to make more top end power - is due its larger exhaust wheel and trim size allowing more exhaust flow. If you carefully select the A/R housing size of your T04Z - you will make more power than a GT4088 any day.

Anyone that thinks that the T04Z is a truck turbo is a) uneducated in turbos, b) having you on c) stupid. There is no "old tech" in the T04Z turbo. The wheels are a complete re-design to flow over 70lb/s whilst still being more responsive. You can thank HKS for making such a turbo and garrett for delivering the final product. HKS have done a lot of research into turbos and streetability to get the best response vs power.

HKS have been known to have a great combination of small yet efficient exhaust wheels matched to larger frame compressors. The T51R (HKS and Garrett) is a work of art for a shelf turbo considering it flows 10000HP and is probably is less laggy than a GT4088 due to its 71mm exhaust wheel, vs 77mm on the GT4088.

9.5 seconds 1/4 in a SOHC RB30 backed with an R33 5spd manual and Jim Berry Clutch in a VL using a Garrett GT51R.

In short, if you have a streeter and want a great turbo for the street and track - T04Z is the go.

If you want to run high times behind a 2speed glide and need all the top end to make 800HP at the wheels - a T51R is the turbo of choice. The T51R will flow 100lbs due to the higher trim and outflow the GT4202 whilst having a smaller turbine wheel than a GT4088!

den001 - you dont know what you are talking about and are relaying info (not facts) that you were sold to on. Croydon have been feeding you BS to pay for a more expensive turbo setup. All Garret GT turbos are "performance" Turbos and are based on their then new GT design wheels which is miles ahead of the AiResearch days of the 80s. The only TRUE performance turbos for petrol applications are the HKS / Garrett T04Z and T51R which are ammended designs of the HKS street petrol turbos. The GT40/GT42 and GT50s etc are all based on Diesel turbos retrimmed for the petrol/performance aftermarket market. You can defend your GT4088 all you like - but the facts and figures from both HKS and Garrett show that the T04Z is a better turbo for power, flow and response compared to the GT4088. With a bit of porting of the compressor cover - I would also suggest that it could make more power vs response than a GT4094 as well.

Back on topic - Saft - Run a T04Z with a 0.84 housing for your 2.6L engine. If you were going to run an RB30 - I would recommend a 1.00 for top end.

You will only need one wastegate, perhaps around 40-45mm depending on the boost level you will be running. Higher boost = smaller wastegate. Low boost = larger wastegate due to the increase in the exhaust bypassed.

[discopotato03]

Well my opinions differ but I'm not interested in starting WW4 .

Firstly the cartridge assembly , forget the wheels for a sec .

If you take a close look at the center housing or bearing housing it looks very like a Garrett GT bush bearing one basically because it is .

If you look at how the turbine housing and compressor backplate mount/ bolt to the bearing housing they are same . There is a minor difference in the oil inlet drilling in the BB version but drilling and tapping a different hole is no drama .

Now to what is called the T51R or T04Z variation of the above center section .

Take one large frame BB bearing housing and machine what would be the the turbine housing mounting ears off and form a register like a bush bearing T04 center housing has . Bingo , now we can fit older tech T04 style turbine housings to the larger frame BB cartridge assembly .

Look very closely at the compressor backplate on a "T04Z" , looks very like an old heavy iron T04 60-1 backplate because it is .

Now lets just wind the clock back a little to the pre BB turbo days and remember the sorts of things that people made good power with , the old T04 60-1 springs to mind . Applied well they worked well but people could not keep the thrust bearings together in high boost apps .

IMO Garretts marketing eagles asked themselves how good sales would be if they could take this turbo and give it a vastly superior bearing system and reliability .

So , the wheels they have and the housings and the backplate so whats left ? Machine up a large frame GT bush bearing core to take the ball race assembly and the oil restrictor (which locates it) and bobs yer uncle . They can now offer a direct replacement cartridge for anyone using an old school 60-1 that fits between their existing housings . Change the oil inlet fitting and in she goes .

This possibly didn't set the world on fire bling wise and I imagine the marketers though what can we do to freshen up the scene .

They would have known that HKS have the zoomy image and whats in the old T04R cartridges because they made them . So if you can make a T04R its very simple to machine the compressor side of a backplate to 84 odd mm rather than approx 76 . Its also nothing new to take a 0.70 A/R T04S compressor housing and profile machine it to suit their 84.4mm BCI-8D compressor wheel .

Really all they've done is rejig the compressor/backplate/housing like they did earlier with the P/60-1 to make a T04R .

Now to wheels and trims . Put simply that T04R compressor is hardly a modern design by todays standards . I can see where its possible to think that a large trim compressor like the R will be good - purely because the inducer size is big . In fact much of the American turbo brigade are so in love with inducer size that they have their own unique turbo description system based around it . You could be excused for thinking that the major diameter of the wheel is unimportant which it most certainly is not but you cant see it with the turbo assembled . My guess is they think big hole hole up front so has to be a world beater , put your own judgement on that theory .

Now they do have some very switched on people in the US and some are even more interested in finding things that work rather than just things that sell easily in a mass market . One of them I know of can't sing enough praise for the GT4088R and if you asked him to back to back one with a T04Z I'm sure he could quote a telephone book full of numbers from personal experience . He may not ever be rich but the measure of success is not always lots of money .

I'm also not going to flog the twin scroll system to death again , you either know or you don't and understandably the cost rules against it for most .

Turbines , the old T04P trim is not such a bad thing and has a useful trim size at 76 . It is thick in the blades an heavy compared to later developments so it is hardy but innertia is the enemy of spool - takes more exhaust energy to get it moving . Off the top of my head they are ~ 74.4mm major diameter wher I thing GT40 turbines are 77mm . The turbine in the GT4088R is different to most of Garretts GT40 turbines in that firstly its made of high temp material and its designed to be a petrol engine turbo - not a lower EGT diesel one . They already have diesel spec ones in 84 and 73 trim sizes for the bush bearing diesel spec GT4088 and GT4082 turbochargers .

Compressors , The 88mm C117 was unique to Garrett when it first saw the light of day . GT stlyle blade form and back to 7/14 blades rather than the usual 6/12 that most GT compressors have . So for its major diameter its inducer size is not huge , what is different (compared to a T04S combination ie 60-1 or T04R) is the larger GT40 backplate and compressor cover . The combination work really well in apps where the exhaust manifold pressure is low and the putts if you like are sharp - unrestricted . These turbos really like mid to large A/R turbine housings and using small ones to lower the boost threshold really knocks them around . Again it comes back to peoples acceptance of exhaust energy and how to get the most from it with the least restriction losses .

One thing does stand out on a GT4088R and thats the combination of not huge trims on either side , the T04P turbine based turbos have it on the turbine side (76T) but not really on the compressor side ie ~ 60T for the 60-1 (Pn 409535-1) or 63T for the T04R wheel . The C117 is 52T .

Trim sizes are important to any turbo wheel , its what tailors the gas flow potential for a given major diameter . Garretts position is that middle size trims tend to give the best efficiencies but for economic reasond its easier to adjust the trim size up or down rather than make a huge range of wheels with mid sized trims . In the case of the 60-1 the 60T is the largest of its family from memory , I'm not sure about their T04R's but I can't imagine needing larger than 63T .

Many of the GT range of compressors are up in trim size but when 56T is as large as they usually go it has to say something .

Compressor covers . Often when you get high speed wheels mobs like Garrett go up on comp housing family , examples of this are GT2510/GT2530/GT2860R/GT2860RS/GT3071R . The GT25/28's I mentioned have ~ 60mm dia compressors which is the basic T3 dia but they don't use T3 sized comp housings , they are T04B family . This gets them a larger diameter diffuser and the housing better suits the air flow capacity of the higher speed wheel of approx T3 dimensions . The GT3071R has a 71mm compressor which is approx basic T04B size but gains a step up to the T04E family of backplate and housing .

People who're read my ramblings for years would remember my dislike of T04S sized compressor wheels (generally 76mm dia) but they use a compressor housing thats larger than say a 76mm T04E or 76.2mm GT37 (from GT3076R/GT3037) wheel normally does . I'd say the reason that they do is that they have 7/14 blades rather than 6/12 so for a given wheel speed they would try to move more air . So to have a wheel with more blades in a larger series housing is what Garrett did in that era .

I believe the move to a larger diameter and larger trim (from 60-1 to T04R) in the same sized compressor housing was a backwards step , HKS obviously had issues with it and had an alternative housing made , actually both housing . I don't know Garretts position on all this , possibly they stayed with the S housing because in the pre BB days going larger in housing with such a large trim wheel caused too high a boost threshold .

Anyway out of time , cheers A .

[Rezlo]

In short, if you have a streeter and want a great turbo for the street and track - T04Z is the go.

Could not have said it better, 28psi @ 4400rpm on a RB25 with tiny cams & instant response at anything over 4500rpm from second onwards...

[Cjmartz2k]

Wow this is some good reading. I think it also blows a lot of the well established "knowledge" thrown around a lot on these boards out of the water.

[Drift Motorsport]

Interesting Info, however if I would still run T04Z instead of a 4088. You need to select the right the housings for the application and top end exhaust flow.

Whilst the GT4088 is a "newer" turbo in the sense of design, it fails to deliver in my opinion due to its trim sizes and exhaust turbine options on a 3.0L RB/2JZ etc.

The 4088 is great for anything in the 3.5-4L range however for the 2.5-3L class it is my opinion that the T04Z will be more responsive and make more power than a GT4088 on the same engine, tune and boost level between 2.5-3L.

From my experience the T04Z is a great turbo and it WORKS BETTER than a GT4088 in correctly sized and matched housing + applications. As with any turbo setup - the turbo charger itself is 1/4 of the application. The rest is the correct wastegate, manifold, a/r housing size and engine + tune setup.

The downfall off the T04Z is that it requires a higher shaft speed to attain the higher flows (about 10-15% more than a GTcompressor). With this in mind - one should always run a smaller housing on the turbine to allow for this so that the turbo can reach its peak shaft speed at the desired pressure ratio. I have found that the 1.00 twin scroll is has been the best compromise for a 3.0L 6 between top end and streetability. Garrett have 10 exhaust housing options to address this exact issue.

discopotato03 - I know you're in love with the GT4088 and you frequently say that the GT4088 is a better turbo than the T04Z because of the material/technology/date it was designed. Turbos are based on early 1900 technologies - The concept has not changed - but with the CAD/CAM use and material use - reliability and better wheel profiles have resulted in more performance. Do not discount the T04Z because it is based on an evolution of a T60-1 and from quasi-diesel setups from the 60's. I will say that if you had the exact spec T04Z wheels and trim setups in GT wheels (ie: custom GT4088 wheels made to T04Z sizes) the custom GT4088 would have better response due to its efficient design - and perhaps flow just as much up top as the T04Z. The GT wheels are a great wheel for response and mid range - but they all seem to have issues flowing high volumes at HIGH pressure ratios when the trim size is too small. Since we are talking about off shelf turbo units - I am a still firm believer based on my driving of GT4088 and T04Z 3L 2JZ/RB30s that the T04Z delivers more in response vs power and makes more TOP END power because it can flow more at higher pressure ratios. Any response issues on a T04Z can be tweaked with a simple rear housing change.

In short - 4088 is a newer turbo - but it does not deliver a better street/track setup on a 2.5-3L than a T04Z purely based on its wheel and trim sizes. The HKS Developed and Garrett built T04Z and GT51R are turbos that have been trimed and speced for street racing setups in mind.

I know that you will still love and promote the GT4088 and that is fine. I will agree to disagree - but please do not slam the T04Z as a highly inferior turbo to defend the GT4088 when it has been proven to out perform the GT4088 in street applications. Both are great turbos and both have their place. If you have a GT4088 already - you have a good turbo so dont worry! Likewise with a T04Z. How they perform is entirely relevent to your power and response expectations.

[den001]

why would croydon feed me bullshit, i got the turbo for the same price as a t04z.

im sure you have much more knowledge than Jim himself.... he has told me that i will make more power and response with my setup, rather than using a t04z

i guess every1 has their own opinions, so i am going by what ive been told by a reputable workshop... i guess results will show soon...

also nobody slammed the t04z, i was going to go for one and was steered away from it.. it obviously makes the power, i was just stating what i have been told...

the wheel sizes and trims are so very very close to both turbos, im sure they will do very close to the same job....

[discopotato03]

Not in love with any mechanical devise , they are all flawed .

Just lost another long post to cyber space via another flawed system ...

Long/short , I would not be trying to make super power from a mechanically std production engine mainly because what the manufacturer had in the way of heads/cams/manifolds is not up to the task .

There is no such thing as a mystical black art turbocharger that spells out instant gratification and solves the meaning of life (42) .

If you can modify the sections of an engine that can make it breathe really well and in the right cold/hot proportions often elevated boost pressure is not needed so putting together a turbocharger system that functions efficiently high pressure ratios is not necessarily the answer .

Its been said here before that boost pressure is a measure of resistance to flow through the inlet system so if you can reduce the level of restriction you can have same airflow at lower manifold pressure of more from the same pressure .

Often people don't initially look into what is going on in the hot side of the turbocharger to allow it to generate high boost pressures . The air pump is a centrifugal type and the way make higher gas flow (boost) is to spin it faster , actually to spin the turbine faster because logically they are fixed and turn at the same speed .

If you have a big piston pump (engine) getting lots of exhaust gas energy (thermally excited gas velocity) is not a problem , if you don't then you have to make a deliberate effort to speed up the available exhaust gasses to really give it to the turbine blades . To speed up these gasses means effectively making a restriction and thats the last thing to want to do because it chokes the engines ability to make power (and rev) and the exhause temps go supernova and fry everything they touch .

I cannot get it through to some that small turbine housings are a poor solution to what is often too big a turbocharger , your calls but its not a path I'd tread .

So to the "T04Z" and GT4088R specifically .

The bottom line is that a GT4088R is larger than any T04 based turbo like a T04Z , the wheel major diameters are 77 and 88mm where the Z's are 74.4 and 84mm . The 88R's housings are GT40 family where the Z's are T04 and T04S .

Specifically the 88R's turbine housings are really only available in the large twin entry T04 international flange size where the generic (not HKS) Garrett T04 housings are available in T4 "Euro" (v similar to "T3") single and twin entry or the above mentioned T4 international size in single and twin entry .

C'mon they ask , what is the point of this mush ?

The point is that many "T04Z's" I've seen have the smaller mount flange T4 turbine housings on them . IMO to get anywhere near the REAL potential of these turbos it would HAVE to have the large flange series T4 international turbine housings and be be twin scroll . A 1.00 A/R international T4 housing normally has much larger ports than the 1.00 A/R T4 Euro version and its not just because different manufacturers have different flanges on their exhaust manifolds .

I'm going to keep hauling you back to the HKS variant of the T04Z because although it has the same exact cartridge and wheels as the Garrett marketed versions the non Garrett components (both housings) make all the difference .

I can't tell you what the compressor housings A/R is but some have suggested 0.80 instead of 0.70 on the Garrett . I've seen pics inside the HKS comp housing and the diffuser diameter looks larger than a Garrett T04S's one , I'm not even sure if all the HKS housings are like this because some say that they have this larger diffuser and others say they don't .

Their turbine housing is another case in point . Only available in the larger T4 international flange but while the flange is divided the divider does not go in very far so you could say its not a true twin scroll housing . The volute section is also different to Garretts T4 housings .

Now you really have to ask yourselves why HKS went to the extra effort to alter the characteristics of a generic Garrett turbo if it was so good to start with .

So make your turbo choice and lets hope it does what you expext of it .

Also as I've mentioned before I probably won't build an RB30 DET , if I was the most it would ever have is a GT3582R though more likely a twin scroll GT3076R intended for the Lancer Evo 10 in the 0.94 A/R turbine housing - if it ever reaches the market .

I don't seek Hp or Kw , they are stupid unrealistic rev based numbers . Ft/lbs or Nm are what moves mountains .

Your calls .

Edited March 23, 2009 by discopotato03