t4 vs t3 t4 hybrid

[mattallac]

I have a 73 rx 2 with a second gen motor ,street ported , 3" exhaust front to back and a t4 turbo .I'm running 10 psi and about 400+rwhp. The only issue is that the t4 spools late in the rpm (about 4800). It is a journal bearing t4 and if i change to a t3t4 it will stay journal bearing .I am interested in good street manners ,i'm not interested in maxing out my h.p. numbers or running a ball bearing turbo ,just drive ability for practical street use . I would be interested in any advice ,rating ,drive ability ,etc. from forum members that have hybrids and what they think about them .

[Fendamonky]

Get a smaller turbo if you want better response...

[RETed]

What is your turbine A/R?


-Ted

[RICE RACING]

Not what you asked for I know......... Buy a T04Z *ball bearing* with 1.32 A/R and run 26psi boost, guarantee 500rwhp and 1 bar boost at 3600rpm minimum.

I used to run T04S with 0.96 rear A/R (P trim turbine) and they are similar to what you have now.

Forget "Hybrid's" I ran every type known to man, in both S4 and S5 frames with T04 front compressors (H trim) and Garret front compressor covers. These are total shit! they can spool early but suffer stupidly from the small turbine. A full T04 you have now will make 50bhp+ for the same boost levels all other parameters being held equal (yes its that big of a difference).

You can dick around with heaps of other "small turbo's" but nothing will ever beat the T04Z when fitted with the right turbine housing. its responsive and mega power at the turn of a knob , you can make EASY 750bhp engine power with one on a 13B, or as little as 400bhp engine power (what ever this equals in your own local rwhp talk is up to you).

Trust me T04 anything less is a miss guided choice.

[mattallac]

Need to check what A/R i have (warning :I am not in any way a turbo expert ,I'm learning) , but i would be interested in a different trim and keep my t4 and not dick around with fitment as long as i can get the spooling to start at an earlier rpm (3500). Questions :1.I have read about taking material off the A/R trim turbine to make a quicker spool, less rotating mass and better exhaust flow. Don't know how good or bad that is ?2. BB turbos are a good thing (for application) ,but at our shop we have had some problems with "bb" turbos with long term or extreme use on them ,RR why is this your preference ? In my limited experience 200 to 300 rpm quicker spool with the exact same turbos is the difference . Journal or bb can be a feeling issue (meaning how the turbo reacts to the drivers pedal action ). Price is also a huge factor BB is almost double . Remember its a street car and I'm not trying to make max HP, just a fast vintage driver .

[RICE RACING]

I probably would not recommend you back cutting the turbine or reducing the diameter of the wheel as that will kill your turbine efficiency and boost level you can make.

I have only ever used Garrett BB cores and Turbo's they at the boost I set up on cars seem to live pretty well, but I never had a problem with journal bearing types either I just liked the logged response better on a BB unit, transient is where I have measured it being best, 4th gear onwards the differences can be minimal to justify the cost increases associated with buying them in the first place.

Street porting really does kill the mid range & response on a rotary engine, the problem with trying to pick this back up with smaller turbines is you really kill the engine and turbo, higher turbine inlet pressure to inlet manifold pressure and resulting higher EGT is common place. In a perfect world you could resort back to stock standard porting and run a larger A/R and alleviate the stress on the motor and the turbine long term, and have a much more responsive engine that will still rev to 8500rpm when needed (say to do 210mph in top gear )

In your case you would need to maybe run a smaller turbine housing (0.82 A/R) divided with a divided manifold, stay with the H trim 58mm compressor wheel and run a good electronic boost controller (Blitz I color works great!) and all of these things combined would offset the lack of mid range power you yearn for on the street. Many years ago I changed out a customers set up on his RX3 running a T2 street ported block from a 0.96A/R to a 1.32A/R set up and even though it was an auto trans it sucked ass! the turbine spec was a miss match for that engine specification. Great thing about T04's is the housings are available and cheap and you can experiment on your set up to test what works best, sure sometimes you may need to dick around with the exhaust outlet etc, but it could be worth the trouble for you. I'd still stick with the T04 frame turbo, these are a work horse and been around since the 70's!....... ideal frame size for a 13B engine. Just trim out that turbine to get the characteristics you are after to match you engine set up.

[RETed]

Turbine A/R dictates your power band - generally speaking.

You can just drop down one turbine A/R size, and that will induce the turbo to boost faster.

The problem is that if you drop the turbine A/R too much, you start to choke power, and you lose top-end power.
It's a delicate balance of sizing the turbine A/R.

In general for a 13B using a T4 sized turbo is to run an around around 1.00.

At this point, it's probably the least hassle just to swap the turbine housing to a smaller A/R.
No need to mess with the wheel or any other part of the turbo.
You might need to readjust the intercooler pipes, as the turbo position will be slightly different.

Side note about clipping the turbine wheel...
This is primarily to increase flow through the turbine section and to minimize the turbo overspooling - in essence, it kills the efficiency of the turbo.
This is really a band-aid fix for a turbo (i.e. turbine) that's not sized properly.
Bottom line: if you size the turbo properly, there is no need to clip the turbine wheel.

BB centers - I'm talking primarily Garrett units - are expensive.
It's expensive to fix if something goes wrong.
Last time I checked, a Garrett GT-series BB CHRA starts at $1,000 and goes up.
Garrett does not sell the individual parts.
You have to buy the entire CHRA.
(If you don't know what "CHRA" is, it's Center Housing and Rotating Assembly - it's the turbo minus the turbine and compressor housing.)
In general, the BB center will give you only about 500RPM faster spool versus a non-BB center when the turbo is sized properly.
The Turbonetics BB centers are CRAP in my book.


-Ted

[mattallac]

what do you think about the turbonetics journal bearing t4 ? i have a cheap godspeed super t4 on my car now and i want a more quality unit .garret is made by honeywell, the price is high and seems the quality has went down hill.But that is subject to debate . To add: yes RR the street port does lack in the mid range drive ability ,and faster spool is what I'm looking for to help the lack of mid range .

[RETed]

Stay away from all that Made-In-China CRAP.
You're just wasting money.
At a certain point, cheap is going to bite you in the ass.

I would expect to pay at least $500 - $700 on a good unit - you should be able to find a brand new 60-1 or comparable size in this price range in the U.S.A. pretty easily.
I only use Garrett turbos at minimum.
Don't be tempted by all that cheap Made-In-China CRAP that's flooded the market - Godspeed, OBX, Goodspeed, almost anything new on eBay that doesn't offer a brand name that's price under $500 is CRAP.

You can save a little money on trying to locate a unit turbo, but standard disclaimers apply for anything used - you take the chance that the turbo needs a rebuild.
The one thing good about Garrett units (non-BB GT-series) is that rebuild kits are cheap.
Most good turbo shops can rebuild these Garrett units for a very reasonable price - check out your local "diesel" shop if you can't find a "turbo" shop.
Find one that does dynamic balancing if possible.


-Ted

[sa22c]

sa22c RX-7
Stock block 12A
Stock 12A gearbox
Stock 12A diff with 3.6 final drive and LSD
Garrett T04B - Vtrim
Series 5 Hitachi turbine and housing (no back cut)
1.4 Bar off the spring

121mph 1/4 mile terminal speed, 2600lb as raced

13psi available @ 3000rpm
19psi available @ 4000rpm

Gets loose in 2nd gear with 3.6 final drive, LSD and new Yokohama Advan A048 205 50 R15 R-Compound semi slicks.

Dyno's are shit the low rpm boost response looks nothing at all like that on the road (but the top end drop off is real), infact its 10 times better on the road. Power curve on the dyno sheet has exact same shape as the secondary injector duty cycle (orange trace in attachment).

[sa22c]

Make that 11.828 @ 124.3MPH

60ft 1.972
330ft 5.207
1/8 7.782
mph 97.15
1000ft 9.997
1/4 11.828
mph 124.30