GT42 vs HKS T04Z
 

Can any one tell me if there is any actual deference between the Garett GT42R turbo and the HKS T04z

T04Z is ball bearing. The GT42 is not unless its a GT42R. I believe the GT42 wheels are bigger too but I don't know the specs. Heck, I think the whole GT42 turbo is a bit bigger than the T04Z. T04Z has different compressor cover with different anti-surge design that the GT42. The Garret T04Z & HKS T04Z both have different comp housings as well with different anti-surge designs from each other.

You´re right ,the GT42R is the one i had in mind .Some one said to me the T04Z is manifactured specificaly for better use in rotary engines.I wonder if this is right cause it costs three times more than the GT42R!

Well it all depends on what aplication u are gonna use the turbo for. The GT42R will spool slower then a T04Z but will make more power.

I currently have a T04Z with a 1.15ar exhoust housing and im getting 1.2 bar of boost at 3000 rpm. But this is with a rather large bridge port and E85. Now im having the problem of keeping the boost down. At 5000 rpm i can keep it at 0.9kg but once i get to 5500 rpm it goes up to 1.2-1.3 bar. This has to do with the flow of the exhaust propeller, the housing and that the wastegate can't take away enough exhaust. This is due to the BP port and E85. On a streetport and normal fuel this would not have been a problem.

Now without adding a second WG i could have gone for the GT42R with a 1.15 housing and i would have been fine. Since the GT42R has a 10 blade Q-Trim type exhaust propeller, wich moves alot more exhaust and gives the turbo alot slower spool.

So if u want a turbo that spools fairly fast on a streetport go for the T04Z, if u want more then 550rwhp go for the GT42R. But u won't see 15 psi untill 4-4500 rpm depending on the porting and size of exhaust housing

Im also guessing someone that has more knowledge of these turbo's will give a more indepth explenation.

JT

To4Z is cheaper than a GT42R. Someone is blowing smoke up your ass.

3x more lol

The GT42R will make much more than 550hp, lol. I have the smallest GT42R offered and it spools very fast and makes 640whp at 20psi. Spools by 4500. The Turbo will run about $2200 is hands down 10 times the turbo the overpriced HKS unit is.

ernie, you're running the GT4294R? kick ass!

74mm comp.
1.01 a/r

Currently im using the Greddy T-78 turbo kit which makes about 480 hp at 1 bar ! It's not bad, but i'd like to replace it with something that spools faster.I have a street ported engine and my goal is up to550 I've searched the forum and the best choices i came up were this two turbos,but as i said above i wonder if the HKS turbo is worth it the price deference ,which over here is about a 1000$!

Is it RWHP of Flywheel HP ur aiming for? And don't go for the HKS T04Z, get the Garrett T04Z wich is a hell of alot better turbo. And will spool quite fast. Alot of ppl get 1 bar at around 3800 rpm with regular gas and a streetport.

I have 1.2 bar at 3000 rpm with E85 and a Bridge Port :) And 370rwhp at 5000 rpm at 0.9 bar. Adding a second WG this weekend, and installing the new exhausthousing as well. So it's going back on the dyno next weekend. Il give u a shout at what HP numbers i get at higher boost and a full rpm pull.

JT

Hey this may sounds like a totaly dumb question

but when you say the turbo "spools" by 4500 , does this mean that you make 20psi by 4500? and produce 640whp by 4500?

I would like to see your dyno char just out of curiousity.

Full Boost. And you guys are silly with this whole lag BS. If your driving along and you downshift, its not going to drop your rpms below 4500 anyhow, so what in gods name are whining about with lag? Its real simple people, if you want power you will suffer some lag. Get over it.

"Full Boost. And you guys are silly with this whole lag BS. If your driving along and you downshift, its not going to drop your rpms below 4500 anyhow, so what in gods name are whining about with lag? Its real simple people, if you want power you will suffer some lag. Get over it."

five stars from me to Ernie on the above. if you want max power you will just have to deal w some lag. if you want no lag you will give up power.

think of the trade off as a straight line graph.

LAG............................................... .................................................. .X POWER
.................................................. ....................................X
.................................................. .................X
..........................................X
lag.............X................................. .................................................. .....power

now simply decide where you want to be on the line given the tradeoffs.

there is a tendency to look at the topline numbers, HP and Tq which of course are valuable. i am a street/road racing guy and so i also look at power under the curve. i have probably a couple hundred dyno charts and one of the things i look at to get an indication of overall hp is the rpm where 200 rwhp is made.

generally most FDs make 200 rwhp between 4000 and 5000. i really don't consider this to be a huge range indicating that it is easier to live w a later spooling situation than you might think.

most reasonably tuned midrange turbos (GT35) make 200 around 41-4300. GT42s make 200 from 4300 to 5000 depending on lots of factors. some of Ray's motors make 200 at 4300! my twin TO4 (84 lbs min) makes 200 at 4300.

where do you make 200? and what's your peak?

then, as Ernie points out, there's always the gearbox. :).

the rotary was made to rev.


howard coleman

I couldn't agree more ,but i need to set some things straight .When i wrote that i want to replace my T-78 with something else that spools faster it's not cause the turbo is laggy ,actually is one of the best .It's because by doing something very stupid i managed to damage the propellers on the front wheel .Since i cant find a replacement wheel over here i have to send the turbo to Japan to have it fixed ,this can take a few months back and forth,so i decided to have a new one and if possible something that fits the existing manifold and down pipe My goal is not to high but i would surely want to have the best turbo available ,and nothing better than a two ball bearing turbo which would for sure spool faster than a none ball bearing like the T-78.In my research i came up with a wrong impression ,it's not the actual T04Z turbo but the whole HKS kit that has such a huge price difference from a one using the GT42R!
So do you thing aT04Z with similar specs same housing(1.0)could fit to my trust 3,5" down pipe & manifold ?

Most rebuilders can order that part through MHI dealers.

Wait, isn't the T04Z a T4 footprint and the GT42 a T6?

the gt42 can be either a t4 or t6 depending on turbine housing

from what's listed on garrets website, you can get
1.01 t4
1.15 t4
1.28 t4
1.44 t4
1.01 t6
1.15 t6

tial also makes there ss undevided housing with a vband inlet, which is a 1.01 iirc aswell

Geezus Ernie, I thought you had T6 frame? I'm running the 1.2 cause of my whore ports, goal is 600hp @ 20psi... looks like I may be getting that eh? Maybe I'll go balls out and do a 35psi run and blow up a tranny or 5.

Mine is a T6. Its the smallest GT42R for it.

I also have a T6 framed GT42R. It is the 1.15 A/R with the 76mm compressor housing.

That is large but small... I beleieve the major on mine is 108mm or somewhere around there... minor is 92 or something.... don't recall the specifics... T4 foot though. Honestly, I'll just be happy to hit 600 @ 20.

t6 is where it's at!

Anymore lag using a T6 vs T4? Or would it actually decrease due to more exhaust flow?

t6 more lag, more power, less exhaust velocity into the turbo, less pre turbo backpressure

t4 less lag, less power, higher exhaust velocity into the turbo, more pre turbo backpressure

http://www.ausrotary.com/viewtopic.p...58&hilit=gt42r

massive thread on it here.

Really its going to come down to what suits you, not really one better then the other.

Id love a gt42r, but for a mainly street car Im going to be heading down the T04Z option once I out flow this little 60-1 :D