Hi all,

This To4b has come up for sale, I was considering going the hi-flow s5 turbo on an FD route, but think this may be a better option, what do you think?

This is the ad:

"TO4B garret Turbo for sale - reconditioned

Has-24 Compressor wheel, N-Trim Turbine wheel,Oil cooled bearing housing, .68split pulse turbine housing. comes with ex -housing inlet flange gasket..This is not a chinese turbo..Has been fully reconditioned including core balancing and not used since recon.
The compressor cover was a rotormater but the rest is garret. The compressor wheel is a 409179-24 garret to4b compressor wheel(58mm inducer,don't know the trim). It is freshly rebuilt from parts I had never been on a car. It was ment for a toyota 1g engine but the guy never showed to pick it up."

Does this sound like a good size upgrade to make some decent reliable power, obviously not huge numbers, while maintaining a decent spool?

Please all advice is more than welcome.
Thanks,
Mike

 

http://www.youtube.com/watch?v=8NWLxjXIGjc

the red rx7 in this video runs a to4b. the small turbine cover size does reduce power output by abit compaired to a larger one. This car has a to4b, 61mm compressor wheel, p trim exhaust 65mm??ish. and a .84 divided hotside. i run it at 15lbs and make about 350 rwhp. car is good and reliable. has been used for drifting for two seasons now. there is nothing wrong with a to4b for moderate boost levels.

with your turbo it has a 58mm wheel, and a .68 divided. and a N trim wheel. sorry im not sure what the n trim size is but this turbo seems to be fairly small for a FD. will likely make no more power than th stock twins and still produce most of the heat. it will work on a FD but my guess would be rpms will be limited by exhaust flow because of small housing creating exccessive heat and a 58mm compressor you will max out at 275wheel ish. i had a fairly similar turbo on a fc and we could only make around the 275 mark. unless its close to free i would look for a bit bigger turbo. precision 6262 .84 or 6265 .84 something in that range. you will be happier in the long run.

 

Will be all heat and back pressure by 4500rpm on a 13B.

 

N trim specs are here: http://turbocharged.com/catalog/twheel.html

 

Thanks for the info.

Wouldnt this turbo flow more than a hi-flow series 5 turbo though? Which some people have said the hi-flow s5 turbo worked well on an FD. Perhaps they were wrong?

And Id have to run an external wastegate, which would also help will exhaust flow.

Please correct me if im still wrong :P

 

It will probably flow more than a s5 hybrid (which is limited by the factory turbine housing), and the external wastegate will help with boost control.

 

According to BNRs website, http://gonzaloherrero.com/bnr/index....d=67&Itemid=89, they claim the following from a Stage 2 series 5 hiflow: "We have customers that have been very pleased with the performance of the BNR Stage 2. One of which made 332 RWHP at 14 psi, and the other running an ET of 12.3 at 114 mph in total street trim.
Stage 2 specs are:
T04B upgrade package with 3" inlet and 2" outlet
T04B H3 compressor wheel
360 degree thrust bearing assembly
clipped turbine wheel
ported wastegate
adjustable wastegate actuator.

They claim the following from their Stage 3: "We have had a customer trap 118 mph on the stage 3 which indicates he is making around 360 RWHP in a full weight Turbo II"

It has Billet seal plate
60-1 compressor wheel
more aggressive turbine wheel clip

And the following for their Stage 4 hi-flow : "The BNR Stage 4 is the world record holder for ANY S4 or S5 turbocharger upgrades for most power ever recorded on a dyno! It made 402.7 SAE RWHP and kept that power all the way through the power band. The boost went from 18 down to 15 psi and the car generated that HP at 15 psi"

Stage 4 specs:
all new CHRA (center housing rotating assembly)
fully balanced
360 degree thrust bearing
billet seal plate
T04B package
60-1 comrpessor wheel/P trim turbine wheel
CNC machined turbine and compressor housings
ported wastegate
adjustable wastegate actuator


So according to this info, Id assume the To4b im looking at, running a 44mm external gate, should be somewhere around at least the stage 2 hi flow level, possibly better?

Or are these figures quoted by BNR not very realistic in your opinions?

 

Turbine wheel and housings are way too small.

 

You're paying too much attention to "TO4B" and not enough attention to the actual measurements. That turbo is microscopic for a 13b. Really, the entire t04B family (besides the t04S) is too small for a 13B.

 

Normally what you say is some of the best info on the forum but that is very inaccurate.

52.5mm turbine exducer with a .68 divided housing is going to be choking the motor. In a practical sense you would have 30+ psi exhaust manifold pressure for 10psi intake manifold pressure.

If 55mm turbine with 1.0 divided housing is pushing **** up a hill by 330rwhp that turbo will be talking about 200-250rwhp in my opinion. And that compressor is proven to go all the way to 380rwhp genuine.

 

+1 did have a detailed reply happening
,, and not enough time to finish it back at post 5
but you pretty much put the point across by addressing the pressure ratio thing

a plumbed back external gate is not a fix for way too small a turbine


,, and that is without considering the thrust wear effects of a 3:1 pressure ratio
( small rear + big front = short life 270 bearing )

you should also note that when doing highflows beyond clipping the stock rear
,, BNR and others use only O and P turbine options ( inside a s5 1.0 AR rear volute )
compare that to this t04 at N trim and 0.68

for the OP--
the s5 hotside with the to4b coldside combined will get you that stage 2 highflow
- with much less backpressure and heat on the apex seals
,, and without needing to go external gate till beyond 300 rwhp and without sacrificing all that much spool to stock
( note : when you do go external , go with screamer dump pipe to limit the total back-pressures )


i can recall a time when some japanese tune houses where offering highflow s5 single options to upgrade from the FD twins
( with documentation showing the differences in outputs and TQ across the range )

 

I will preface my response to this by saying that we are all only speculating as to how this turbo will perform. The specs on an N trim turbine wheel are

2.071 inch / 52mm exducer
2.922 inch / 74mm major

or you could call the 52mm an inducer and 74mm an exducer if you want to.

specs on stock turbine wheel is

54mm / 63mm . see https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-turbo-wheel-size-818137/

So this N trim turbine wheel is a slightly smaller in the smaller dimension (inducer, exducer, whatever you want to call it) but has a larger total diameter. It's not a P trim wheel but in one sense it is bigger than stock due to the larger overall diameter. The turbine housing may be smaller in terms of A/R, but A/R is merely a ratio. That's why I like how Mitsu, Holset, and IHI turbos measure hotsides in terms of cm^2 as opposed to a ratio. From the pics it appears to be an actual T4 turbine housing, which means a .68 housing is still going to flow more than the stock s5 turbine housing. Again, A/R is just a ratio.


To say it will be heat and backpressure due to restriction is correct in a sense. That's what stock and nearly-stock sized turbos are like. The more restrictive housings tend to make more part throttle boost pressure with better response. So it comes down to what you need. I'm not saying this turbo is going to make a lot of power over 6000-6500rpm. But that's not always such a bad thing. Some people want more mid range, especially if you have stock ports. It will be more like a DOHC V6 powerband than a Honda powerband.

 

See these are the things which made me ask the question in the first place, i appreciate the discussion so far, very informative, would like to hear more and get to the bottom of this