Exlex

Hi everybody!

I have had some thoughts about what turbo is good for a 20b standard ported engine.

I know the most common answer is GT42R but it seems so darn big for this setup if you want just a streetable 20b engine. Or is this combination a good mix?

I was thinking about the GT35R with the large hotside, but all I can do is guess without knowing what variables to put into the compressor chart. And if the gt42r is a good sized turbo, then the gt35r compared to it is a hairdryer.

low boost threshold is what I guess would be called a streetable turbo, but what is your input on the different turbo setups? What other turbos but the gt42r are people running, anyone got some smaller turbo?

For reference, the "common" answer:
consider that I have put some thought into this thread, I have visited the search engine, if you know a thread already talking about different turbo setups, point me in the correct direction

teachermechanic

iTrader: (4)

Turbonetics T70 turbine housing 1.00a/r work realy fine on conservative street port.
Check my video on my sign.

RETed

A GT35R fitted with a 1.06 A/R turbine is a damn good match for a 13B 2-rotor.
What makes you think it's a good mate for a 20B with an additional rotor with 33% more displacement?

A GT40 is still not an unreasonable choice for a 13B.
Which would make a GT40 still too small for a 20B.

This is why a GT42 is a minimum size for a 20B.

Sure, you can run a smallish turbo, but why choke the motor when you can run a bigger turbo WITH LESS BOOST TO MAKE THE SAME AMOUNT OF POWER.
Less boost is always desirable, right?

I just don't understand where your logic is coming from?


-Ted

Exlex

Very nice! and that curve is rather crazysteep! I like it!

The biggest problem I got with these turbos is the shear size of them. Hard to hide them in the engine bay. And I think thats little what I'm getting at. Are all setups out after big powerfigures or is that just a byproduct when getting a good setup? The biggest advantage of the 20b is the greater torquefigures and to use that to it's fullest potential a correctly sized turbo is a key ingredient.

I guess it all goes down to the purpose of the car. Street, strip or track. And I fear that there are as many answers to what a good combination is as there are different people trying it on its own. Right?

CMonakar

50% more displacement I agree, a 35R is way too small. It will over rotate itself to a quick death trying to keep up with the airflow requirements of the motor.

Exlex

Ok guys, now we're talking. CMonakar you say 50% more displacement and Ted says 33% ... are you guys talking about the same sort of displacement here?

Ted I really appreciate your input, I respect your knowledge. And you are totally correct, when putting it up like that it sounds like a bonehead thinking, but I think that's cause a gt35r with a 1.06A/R feels, to me, like a very big turbo for a 13b, and I think that all bolts down to that I do look to much on the horespower specs on the turbos (which I know are nowhere correct for rotary engines) and listening to people that have no rotary experience.

I agree that more power with lower boost is always desirable to take away the stress on the engine internals. But making power with low boost won't that up the boost-threshold or is that not that big of a deal with the additional displacement and torque of the 20b?

So we are once again boiling the things down to a gt42r, what A/R is recommended then?

CMonakar

Yes I'm just busting Ted's chops. 133% * 2 Rotors = a 2.67 rotor. 150% * 2 Rotors =3 Rotors. The displacement increase is 50% not 33%.

I have a 42R with a 1.15 exhaust. I haven't had any experience using it yet other than to drive it a few feet and rev it. I chose the turbine based on what people said about using a similar size T76 (at the time I couldn't find anybody with a 20b and 42R), input from A-spec, and TEC turbo.
I found a handful of posts by people using the T76 turbo with similar specs and a 1.15 exhaust A/R. The consensus seemed to be that it spooled up around 2500-3200 with a plain bearing center section.

Remember the turbine A/R is not very expensive to replace and I don't believe the position of the center section above the manifold flange changes with the size (someone correct me if this is not true). If you get it wrong you can always switch it.

RETed

Oops, it's like 5am in the morning over here. :P
I was going backwards in the calculation!
DOH


-Ted

RETed

Yeah, and you gotta remember that you're trying to compare different frame size turbine sections...

The GT35 runs a T3 hot side, and even with the "largish" 1.06 #, a T4 with a .96 A/R is going to be bigger and flow more due to the larger frame size.
Best thing to do is read what others have done, as CMonakar had already mention.
Remember what you're trying to accomplish with your set-up, cause it might be different goals than what others are trying to do.

Personally, I like BIG top-end, so big turbine A/R's don't scare me.
I know I can sacrifice some low to mid range response for a big top end.
The 20B already has good torque down low, so response is something I can compromise with.
Running a T4 (or even T6 frame) at 1.32 A/R (or larger) is something I would do with a 20B.
In fact, I would try a "gigantic" 1.70 A/R just for the hell of it!
So you understand my point about what your goals are?
If I had the money to burn, I would run an HKS T51R SPL BB with a 1.00 A/R on a 20B - I bet it would make WICKED power with GREAT reponse!
Too bad it's a US$3,000+ turbo...


-Ted

frisc

iTrader: (2)

that turbo sounds nasty! i'm also trying to find out witch turbo to get and the t-70 doesnt sound that bad. Is your turbo ball bearing?

diabolical1

iTrader: (3)

yes, i think you need to size the turbine just right for any engine, and for the 20B i really don't see anything smaller than a T6 (or similar) frame being suitable.

teachermechanic

iTrader: (4)

No it's not ball bearing, and honestly i thing this winter i will change for T72 ball bearing with "Q" trim turbine housing.

crispeed

Precision Turbo PT76-GTS/.96 will staisfy your size and power goals.
No need for the Mack truck size turbos when this little fella can support almost the same power.

thetech

iTrader: (1)

I am using the Master Power T70 with a 0.96 exhaust. It's slightly bigger on the compressor than a T04R, so I imagine it's really on the small side for a 20B but we'll see how it performs on the dyno in a couple of weeks.

What really swayed me towards using a smaller turbo was looking at the dyno graph of (I forgot his name) one of the FD autocross cars that was using a GT40R with a 0.96 exhaust - he was making 400+ tq at about 3000rpm! For me I am more interested in area under the curve than peak hp, but we'll see if this is *too* small for track use.

Turblown

iTrader: (12)

I am going to try my P trim to4R on my 20B. I have a feeling that the P trim might be too small however, even mated to the 1.58 turbine housing. I feel the compressor should be more than adequate for the motor, especially with pre-compressor aux injection.

If the original poster is interested we offer P trim turbines mated to 35R assemblies, journal or ball bearing. I feel the 35R turbine is too small for even a 13B if one is going to try and make full use of the compressor wheel...

tigerboy rei i

So, what would you expect from the HKS turbo? Good torque, insane hps, and able to change the boost to range from 400 to 700 hp? I'm kinda looking for something streetable that can be turned up to beat Ferraris?

P.S. - Where can I go to find out what turbo specs mean in airflow and boost level? I have no idea what a/r and compressor size have to do with anything. Help me cure my ignorance!

frisc

iTrader: (2)

how about the greddy t-88 34d???

It looks like its smaller than the gt42 and i've read that it put down 650hp in the RE Amemiya Super GReddy RX7 20B...(http://www.jdm-option.com/eng/pickup/05_12/super.html)

just an idea

Exlex

While we are talking turbos and such, how much of a gain is it to have a BB turbo? I hear people say about 200rpm in boost threshold?

tigerboy rei i

Answers still pending?

teachermechanic

iTrader: (4)

All you need to know:
http://www.turbobygarrett.com/turbob...ch_center.html
For map:
http://www.pagparts.com/Garrett_Turbochargers.asp
Compressor size specs:
http://www.precisionturbo.net/turboc...tegory_id=3027

Rub20B

How about a HKZ T04Z with the biggest A/R available? Should flow 600hp easy and is know for very good spoolup even on 13B's..? Or is that also too small?

synergy7

iTrader: (20)

For my 20b project (if I don’t jump on the GT-42 bandwagon) I am looking into "TURBONETICS" T-78 or T-88 Thumper hot side no smaller than 1.15 Low boost but HUGE volume. Although the maps look like they would be perfect for my application, I am not finding much people with real world experience with these turbos on a 20b (just hypotheticals).

GT-42 has been done and works well, the wheel is not that large its the design of the wheel that yields all the performance in fact the GT series are the first updated designs in about 40+ years (don’t correct me if I’m wrong; I don’t care), I think a lot of people get aught up in the look (EXTIRIOR size) of the GT-42 and that has now translated in to the bigger is better theory on turbo charging. Performance comes in all sizes (look at the twins that come on the motor). The real question is not what is (be) the largest turbo, but rather what are your goals and what turbo will meet your goals while providing maximum efficiency.



F.Y.I
Greddy t-88 is about the size of a T-76
Greddy y-78 is about the size of a t-66

Rub20B

http://www.turboneticsinc.com/produc...category_id=84

frisc

iTrader: (2)

any thoughts on a NON-ball bearing gt42??? should it be the same power levels as the ball bearing version but spool a little slower??

thetech

iTrader: (1)

The journal bearing GT turbos are generally alot smaller than their ball bearing counterparts; make sure you check the wheel sizing when picking one out, as the same part numbers have totally different wheel sizes (ie. GT4202 is totally different size to the GT4202R).