Quote: will a t04z get you around 500 rwhp on a twin cam head rb30 bottom end? Both the 3540 and 04z will. What's ur max power target?

Quote: Originally Posted by gmchaser dont hks use garrett turbos as a base, and then modify them in one way or another. yes

yeah modify as in put their own housings on

I have a TA51r which is the old school bush bearing equivalent of the one you are talking about from what I can gather from what you have said and what my turbo man (John Patrick from turbo supplies .... built the turbos for TRYHRD and numerous race cars lives in Townsville you might remember a gold vk commodore race car with a twin turbo 350 running high 7.9s in the street machine and Zoom mag he does alot of good work) has said. He quoted $2500 for the t51r same rear housing flange patterns for the dump and manifold flange. He told me that once you get to the size of turbo you are talking about that the ta or t series of turbos are a more desireable turbo because the way the wheels work in the t turbos once they are making 1 psi of boost the engine is going to start to make power and they will make boost more gradually. This is apposed to the gt turbos that need to be pumping depending on the turbo 18-20psi before the engine starts to make any decent power and they have no mid range they are on or off. The way I look at it when you are boosting at 4500 or latter and you are only reving to 6500-7000 maybe more but you are only going to have a very small power range and you don't want to make that power range any smaller than it already is... Not only that but the t51r is a significantly cheaper turbo isn't it ?

Is that what he said, that sounds like a load of crap. The Gt wheels have a much wider Boost range than the old school wheels. So they are more likely to make power on LESS boost. That has been proven search the net, you will find back to back tests T wheels versus GT wheels in the same comfiguration/a/r everything, Try the buick regal turbo sites. My baby Gt42 makes killer power at only 16psi(315rwkw ,auto) and is well into it's power range. Actually 90 percent of this forum would be happy with just driving it on this setting. I know what a turbo feels like when it's not in it's effiency range and i can tell you it is, it's perky as, suprised the hell out of me,thought the area under the curve would be dismal. The bottom end at 16psi, is still closely matched to the 3540 1.06 . They are also more likely in a manual car to actually reach fullboost in the lower gears, With old school turbo you can have a problem(especially with under 2l motors)were engine revs rise faster than boost. But i have seen a few posts in here where people where saying they had the same prob with Ta's on Rb30's, But can't verify it as i haven't had one. cheers darren

Strange choice ,T04z versus T51R aswell, would be worlds apart, One would have full boost in the low 4000rpm range, and the other i would have thought would be up in the 5000-5500rpm range, massive difference cheers darren

Quote: Originally Posted by PLATNUM garrett T51r is more responsive than HKS, and it costs alot less Any evidence to back this up from real life testing? Some Specs on the T04Z HKS T04Z Compressor 84mm 63Trim with .70AR Ratio housing Turbine 74.2mm 76Trim with .61/.81/1.00 AR Ratio housing. Claimed power is 700 Hp or PS . Note Some GTRs are running ~430 kw at the wheels (4wd) with this HKS T04Z Turbo and ~400kw at wheels (4wd) with the Garrett T04Z "Version". By Comparison, the Garrett GT35/40R has similar specs and power flow. The T04Z uses an 84mm 63 trim comp where the GT40 side of the 3540R is 82mm 56 trim. The OD is not much different but the trim jump from 56 to 63 is pretty big and if the aero development is better the pumping efficiency could be as good or better. Generally speaking the higher trim the better developed the wheel and the more efficient the compressor map is, but it has to be matched to the overall package to get best results. No use in going for a high trim wheel when you can’t spin it up into the efficiency range. The turbine has gone up in size from 68mm (GT35) to 74.2mm (HKS T04Z) but the trim has dropped from 84 (GT35) to 76 (HKS). So the GT35 has less rotational inertia due to a smaller turbine inducer size but may have less response due to a larger trim. Again it’s all about compromise and how the turbine is packaged to the compressor. The HKS can flow more top end and keep the compressor spinning faster, that is why you can see 430awkw out of GTRs on about 25PSI, which is over the 700HP or PS rating that HKS give the turbo. In the real world, its a pooftenth difference and there are many other variables that contribute to power - not just turbo response and peak flow. It is well known that most HKS turbos are actually Garret CHRA Assemblies with HKS custom developed housings, wheels and Trims. The R&D to build the turbo from scratch in house would be close to 50Million and you will have to get involved with a lot of patent laws and so forth - so they subcontract the work to Garrett who own the technology and have been established in the industry for many years, and then have HKS' team of engineers work in conjunction with Garrett to build the best package for their kits. HKS Turbos also have innovative features such as Anti-Surge housings which allow the compressor map to have an almost even gradient surge line - meaning that you can add more boost without reaching surge at higher RPMs and also increase response. The Anti-Surge housings have appeared in some bigger GT40 compressors in Garrett offerings. HKS Turbos will always be better than Garrett Turbos - but at their stupid prices - a Garrett Turbo has best bang for buck. If you got the money, go for a HKS turbo. Ill be using a Garrett "HKS" Style turbo for my build as the extra 200-500 rpm in response and flow can be gained by other ways such as cam timing, cam profile selection, ignition timing and management, etc at a cheaper price.

From Another Discussion: It no secret that the TO4Z cartridge is an evolution of the Garrett/HKS TO4R turbo and now has a modified GT40R/GT42R/T51R style ball bearing centre section . It also uses the TO4 P trim turbine which is getting pretty long in the tooth . Its surprising that they chose that turbine given that the ball bearing GT40R was being developed though to be fair it was not then being tested in its final form (Garrett were still playing with the 84T GT40 turbine) . Garrett is starting to change their ideas about turbine trims for petrol engines and moving down from the agricultural 84T to lower sizes such as the 78T in the final release version of the GT40R (GT4088R) . The old P trim measures about 74.2mm OD and is 76 trim , its rather heavy and uses I think 11 blades compared to the 10 Garrett uses on the UHP family ie GT35/37/40/42 . Many people are saying that the 68mm GT35 turbine can pretty much do the same job while being more compact and have less innertia to overcome at the spool phase . It sounds good to me though The 68mm turbine compared to the 84mm TO4R compressor wheel makes me think hmm are the turbine blades long enough to get good easy low gas speed shaft power , did the TO4Z use the P for this reason ? I think Garrett should have looked at using their 72.5mm GT37 turbine in an appropriate trim to replace the aging P when it grew balls . The fact that the GT40 ball bearing cartridges turbine is 78 trim rather than 84T sent me after its turbine map to see how it weighed up compared to the GT35R's turbine map . The smallest .85AR turbine housing for the GT4088R comes out at a similar ~ 32lbs of corrected flow to the GT35R with its largest 1.06AR turbine housing thought the 40R reaches this point at lower pressure ratio than the 35R . Then I started to find mention of a hybrid GT40R 67 (67 is what the Americans call the TO4R compressor) which is the GT40R hotside and the TO4Z compressor end combined . A company called Precision Turbo and Engine get this combination made up and market it in the US as the GT4067R . The as sold GT4088R is no slouch either though it has gone to a new 7/14 blade GT compressor of the C117 family . It uses a huge .72AR GT40 port shrouded cover which looks like a carry over from the TA45 series turbos . The debate over GT4067R/GT4088R is ongoing in the US but the power developed is easily in the 7-800Hp and beyond with the best optomised housings and engine setup . The Honda/Lancer/Supra people are developing all sorts of things ATM and much of it surrounds these turbos or the even larger GT42R/HKS T51R . Just on these last two take note that HKS's T51R gets the 76T 82mm turbine while the Garrett GT42R gets fobbed of with the 84Trim 82mm turbine - Power and Response by High Kost Spec ..... So anyway the TO4Z or GT4067R or GT4088R are all vying for the 650-750Hp arena with the US performance crowd pushing the two GT40R based turbos . I have a feeling that the Precision GT4067R will be the best all rounder and very tunable with turbine and compressor housings . Its unfortunatly going to be the most expensive of the non HKS options because it has to be disassembled and balanced plus its unique backplate machined up and fitted . Garrett could do a lot worse than offer it themselves . Any of these turbos are not for the faint hearted and probably need a high reving RB26 or preferably an RB30DET to do them justice . -discopotato

Noticed the Anti Surge Belmouth leading to the Inducer - allows for more boost at higher RPM on engines that may have limited flow at certain high RPMs Some original photos have not been recovered yet.

Quote: He quoted $2500 for the t51r same rear housing flange patterns for the dump and manifold flange. He told me that once you get to the size of turbo you are talking about that the TA or T series of turbos are a more desirable turbo because the way the wheels work in the t turbos once they are making 1 psi of boost the engine is going to start to make power and they will make boost more gradually. This is apposed to the gt turbos that need to be pumping depending on the turbo 18-20psi before the engine starts to make any decent power and they have no mid range they are on or off. What you have said does not sound logical at all. The TA Wheels have a much narrower compressor map with greater surge issues than the GT Wheels. It’s not so much the size of the wheel, but the trim and aero design that makes them efficient. Engine power is directly proportional to airflow. The fact that the GT turbos start to build boost more rapidly is because they are a better design and are thus more efficient. Perhaps your mechanic is suggesting that the T Series turbos, such as the TA45S etc, are better suited to your application because they make boost slowly and thus the power surge isn’t as rapid causing a loss of traction. If you were to increase or decrease the response of any GT Turbo, simply change the rear turbine housing to suit your application. Brent (NZ VLT) has noted that the 0.83 housing has a very violent transient state where it is difficult to control on the track and thus not as drivable. The 1.06 housing proved be a better alternative because the transient response was slower, and onramp on boost not so violent - thus making the turbo more drivable through "lag". Again, I do stress to match the turbo to your power goals and specific torque curve you would like to achieve. Granted the T04Z and T51R as well as most GT40s would flow enough to run 9 second passes with a working rev range of 4k - 8k on an RB30ET and RB30DET combo, but that same turbo might not be all that crash hot on the street for response and lag. It’s not uncommon for a proven 9sec car to loose a race on the street to an 11second car because of a lack of traction in the faster car off the line - Not to mention most street races are ended before any 1/4 mile is achieved anyway.