Hks To4z Turbo Specs, What Else Is Similar?

[Chris Wilson]

I have finally tracked down and bought an HKS cast iron single turbo, low mount, remote wastegate manifold, in the USA. Hopefully it will be with me soon. I want to fit a similar turbo to it to that that HKS supply in their TO4Z single turbo kit, but not pay HKS prices. What ball bearing turbo will have similar flow figures to that? I am thinking GT40? Must be TO4 flange, ball bearing centre section, divided turbine housing flange, remote wastegate. looking for 600 BHP. Engine is all steel with 280 degree Tomei cams, on Motec M800. Stock plenum, 2.6 litre, ported head. Cheers. Car is for track day usage, in a 2WD R33 GTS-t. Any more power would be silly / useless, the things bad enough with 440 BHP Thanks for looking.

[R31Nismoid]

What about using a Garrettt T04z?

being its virtually the same thing excecpt no split pluse rear end if i recall

[Chris Wilson]

The cast iron manifold has a divided turbine housing flange, I'd like to match a similar turbo to it. Are there any flow figures for this turbo? How similar is it to a Garrett GT40? Thanks for the reply.

[discopotato03]

HKS and Garrett TO4Z's use the same cartridge or CHRA (740759-5002) . The HKS turbine housings are only divided for a very short distance inside the turbine housing flange or inlet . They are not a true divided housing because the divider ends before the volute section starts and the nossle that feeds the turbine inducer blades is not divided or split . My theory only but its a remarkable coincidence that the bush bearing HKS TO4R used a split TO4 flanged housing and their TO4Z would make a lovely upgrade .

A few have mentioned that they use the Garrett marketed TO4Z with single entry T3 flanged turbine housings and get good results . I think low friction ball bearing cartridges have removed the need for twin entry or split pulse turbine housings , if you look at the turbine maps at the turbobygarrett site you'll notice how much faster the BB versions get going compared to bush bearing maps . You will also notice that virtually all their BB turbos use single entry housings where many bush bearing types seem to need split pulse housings . My private theory is that a free flowing exhaust path is critical to todays emission/consumption/cat light up and volumetric efficiency requirements and a must have at lowish revs . At times split housings have a bad habbit of cracking around the divider , probably because they were designed for Diesel apps with their lower exhaust gas temperatures and don't tend to cope as easily with petrol engine exhaust gas temps unless material spec is changed to suit . There is no problem with running a single entry housing on a split pulse manifold , all VL's and most RB sixes do it like this .

Its interesting that you found a HKS single low mount split pulse manifold with the TO4 flange , I thought they used the T3 split flange like the RB20/25 version does .

There is a bit of controversy surrounding Garrett GT40's and GT40R's . A couple of years ago Garrett releasd a BB GT40R with I think an 88mm 52 trim BCCW series 6/12 bladed compressor like the bush bearing GT40 has . These were only on the market a short time and in very short supply - soon dried up . Then not too long ago it reapears but this time with the newer design C117 7/14 blade compressor in 88mm 52 trim . The map looks quite good but it gives no indication of how responsive the turbo is in the real world . The turbine in bush and BB form is a 77mm 78 trim UHP design .

TO4Z's use an 84mm 63T TO4R compressor thats supposed to max out at 75lbs flow compared to the late GT40R's ~ 68lbs flow . This wheel has good anti surge properties which is a bonus .

As to which is better ? No one seems to complain about the TO4Z's abilities , most reckon its really good and up to 750 odd Hp difficult to beat for its response .

I don't have any feedback on the GT40R , I can say its getting pretty heavy and bulky for its capacity so that has to say something .

Cheers A .