I'm looking for a turbo that will spool a streetported 20B. I like Garret but will consider anything that will perform best for street driving and occasional spirited driving. A quiet exhaust is the main motivation for going turbo. I must be getting old.


Car:
•'81 FB
•already has full 3" exhaust that is too loud as NA (speaking of getting old lol!)


Fuel system:
•GSL-SE fuel tank
•GSL-SE lines (8mm or 5/16")
•Walbro 255
•MegaSquirt


20B Engine Specs:
•#756 early castings
•streetported intakes
•swapped sleeves to FD/T2
•stock 550cc pri/sec injectors


trans:
•S5 NA 5 speed (yes I know but I'll use it until it breaks)
•RB Street Strip pressure plate
•ACT street disc
•RB aluminum flywheel (could go RB light steel as another option)

Looking for 15psi or less on pump gas. It needs to spool quick for nice driveability, but hopefully off-boost response will be good thanks to a light weight chassis.

What specs should I look for? Divided/Twin-Scroll T4 inlet? What turbine A/R? What compressor size? Is there a list of specs anywhere? Thanks.

 

I already had the engine up and running in NA form back when it was stock ported. It had great low end but nothing above 5k. So I ported it!

My streetporting progress:








Haven't touched exhaust yet, just changed sleeves.

 

The only thing that concerns me about your set-up is the early engine e-shaft if your seeking hi hp levels. I'm only assuming this because you wanna port the engine. Even if you stud the block, it's not gonna help the e-shaft. How much power you trying to make? I'm not sure why eveyone want to port 20b's? The stock porting will easily handle 600 hp. Hell there was a 100% stock port REW that made 600hp (and stock 20b porting is larger than REW porting).

 

Actually REW and 20B secondaries are exactly the same (as is 74 spec in the REPUs with just a minor change at the very bottom). The primaries, as you know, are different shapes.

I was going to be NA from the beginning. That's the reason for porting. Now I know it wasn't necessary. I'm doing an FD engine for my REPU that won't be ported, for this very reason (and it's a truck lol).

The damaged is done. The port closings are a bit mild compared to some I've seen. My only regret is opening them so early. Think that will be a problem with a turbo?

I'm not looking for high HP. Infact my original goal was for 300HP+ and 200+ torque like GtoRX7 so I wouldn't have to upgrade the drivetrain. I also had hopes of going turbo eventually so I stayed with the stock 9:1 rotors. Now, it seems, that's paying off.

So with the port work I've done so far, can I get a smallish turbo that will spool quick and work with my 3" exhaust?

Oh I do have access to some 850cc FD secondary injectors to use as primaries if that's what people do. I'd prefer to keep my stock 550s though.

 

Run a undivided housing, smallest turbo I would consider is 67mm with a larger comp A/r something like a .75 the rear housing should be near 1.0 usually .95 or .96 is where undivided lands. Turbine I wouldn't go smaller than a P-trim you could go larger and possibly should be once you step up to the larger turbine wheels the cost jumps. What's your budget? PM me if you don't feel like advertising that.
It's easy to make 500-600hp on these things almost too easy if your not careful, then you break things and it gets expensive.

~S~

 

Thanks for the offer. I sent you a PM but maybe I'll ask in the thread as well in case others are interested.

I've seen a few possible turbo choices on eBay. I'm looking for something cheap as a starter turbo since I've never done this before. Using Howard Coleman's big turbo comparison list, I began searching for a few that caught my eye. This T88 is affordable but seems too big. Plus it has a divided flange. Hmm.

 

I'm really only looking for oh let's say 400-450 HP now. Nothing huge. The original goal was to follow in GtoRX7s' footsteps and build a big streetported 300HP and 200 torque NA 20B because it would be plenty for an FB and keep me happy for a while. My tranny and clutch could be kept even (light rear end = no traction so you don't break stuff lol).

But high power and NA means a LOUD exhaust. I've been into LOUD NA rotaries for 20 years and have owned them since '96. Time to step up to a nice quiet turbo.

I love the RB dual pipe long primary 'street port' exhaust system for 1st gens. It's quiet at idle but gets loud only when you get on it. I find I drive faster with more confidence the quieter the exhaust. I know, opposite of most people, right? Maybe because I know I can get away with more spirited driving if I know you can't hear me coming from a 1/4 mile away lol.

I'd like my car to end up only as loud as an RB system. I feel a turbo is the right way to do it, and make the kind of power I'd like.

Heck I don't even require 400HP. As long as I can get a quick spool for great drivability, keep it quiet, and keep my stock injectors, I'd be happy with 350HP and 300 torque.

However I do have some 850cc stock FD secondary injectors and I'd purchase some 1680 or 1600 secondaries (top feed) to fit my stock rails if that would be a wise choice. Are they high impedance?

 

After a couple hours of searching, I think I found something that could work. It looks like this turbo is pretty close to what Zero R was recommending.

http://cgi.ebay.com/ebaymotors/T72-T...item27b588d250

Zero R recommended at least a 67mm turbo. Not sure what part in particular that refers to, but this turbo is advertised as having a 72mm compressor wheel right at the top "Big Turbo, Big Power, 72mm Compressor Wheel." Is that what I'm supposed to look for?

I couldn't find an A/R for the compressor. Is that bad?

The rear housing or turbine (did I get that right?) has a .96 A/R. This is good.

Appears to be undivided in the picture of the actual product (includes a v-band and clamp plus gaskets so that's convenient). This is also good.

I don't know what P-trim means, but it's got it!

Oh and a couple of other nice features is it's water cooled and has wet float bearings. I've read on this forum that these two features are great on rotaries due to all the wonderful heat they make and the high oil pressures we like to use. I won't need a restrictor pill in the oil supply line thanks to this, will I?

How about the M16 banjo bolts for water cooling? Will FD stuff work?

 

Somethng just occured to me. This turbo has a really small and wide looking turbine housing compared to what I've seen used on rotaries. Could just be that it's not divided. But anyway It seems to me this would be more efficient at higher RPM on a two rotor, but if used on a 3 rotor, it ought to work out just fine from low to high RPM. Thoughts?

Oh did anyone else notice some of the pics near the bottom? 12A turbo.

 

i have similar goals and actually just purchased that exact turbo from rotaryworks last friday.

 

Holy crap, really? That's great! Please tell me your specs, porting, power goals etc. Or do you have a thread somewhere?

 

Hope this helps.

 

Darn I don't have spreadsheets on this computer. I'll check it on a different computer later today. Thanks!

 

stevensimon, is this the turbo you're talking about? http://www.rotary-works.com/mm5/merc...gory_Code=TRBA

 

yes that is it

 

Polished, very nice! Hey, since my 20B is ported, think I should choose a slightly different A/R? It's got early castings, so my power potential is limited. I'm thinking 400 is a safe limit.

 

they have the 1.15ar housing available, which should be pretty decent too i think. i chose the .96 to help my spool but im also not ported in any way. my goal was 350-400hp @10psi. im sure this turbo will still be a bit on the big side for me but it seems to be a better option than a 60-1 with a huge turbine.

 

Yeah, I saw that one a couple pages in. I'll give it more thought before I buy anything. I'm just sort of surprised I found a turbo that somebody with another similar 20B power goal is actually using. It's been a steep learning curve.

The first turbo I ever messed with was earlier this year in PercentSevenC's '83 FB. It was an S5 turbo on an old school streetported R5 13B with a weber blowthrough (had to space the turbo out from the manifold to make it fit). That turned out noticeably more powerful at 6 psi (non intercooled) than the previous 7" Camden SC was at like 9 psi or whatever the pulley was set up for.

Of course his exhaust was small and restrictive at the time too (2" lol), which may have been causing too much back pressure up into the SC intake manifold giving us a false high reading.

When I tested that same SC on my similarly ported R5 13B with a full 3" system in my FB, I don't recall the boost gauge reading that high. It also was even more gutless feeling. My timing was off (remember pullies are a matched set, and I was using a Camden serpentine aftermarket pulley which turned out to be off by several degrees) and the air filter is known to be very restrictive.

I stopped driving it because the full 3" exhaust was way too loud for the street. I believe I only put 2 miles on that setup. Then I switched to a 5" Camden to test that briefly. It was still not powerful enough to break them loose in gear going straight (I've got LSD and old hard tires so it is easy around corners, but I'm talking straight line). I put only a couple more miles on this setup for a total of 7 lol before I pulled it and dropped in a freshly built ported 12A for test firing for a guy. That worked out ok using an exhaust manifold from a 6 port 12A (it's like a mini header and does not expand like the stock log style our US-spec 12As got)and a 21 year old Rotary Engineering glasspack before it expands to 3" to take advantage of the rest of the existing system; it's still loud but only on the drivier's side of the car now. Weird. Anyway it sounds like it's got a turbo in it thanks to the low and loud but somewhat muffled nature of the exhaust note. I'd like it to be just a tad quieter once the 20B and turbo go in.

It was recommended that I get a Magnaflow 18" long 5x8 oval with a center/offset 3" core http://www.magnaflow.com/02product/s...e=main&id=8916

 

back in the day we figured that the HKS T51 was just about the perfect 20B turbo. the HKS turbo is about the same size as the GT42, but its undivided which is perfect. on a 2 rotor a divided turbo is better, but the 3 rotor is always 3/2....

oh i did get your pm BTW

 

I think I found a local source for side plates so I'm good. Just curious if you or Paul had any decent ones lying around.

How much power would you run through an early casting motor? I'd like to start at 300 since that was my HP goal from the very beginning. It'll let me get aquainted with to how to tune and I get to keep my stock injectors. Then I'll push it up to 350 which is where the 550s start to run out of juice. Can I use FD 850s as primaries? I wonder if the early MegaSquirt I'm using has enough resolution. I'll look for bigger injectors later, just curious. Thanks.

 

This would work for what you're trying to do, and it is within budget. I would buy this before anything used on ebay, the only caveat being it's not a chinese knockoff turbo, I say this because some of their stuff is chinese import stuff.

~S~

 

Thanks! I'll purchase it when the funds are ready.

Is the rotary works turbo the same as the eBay one? They look the same, but the eBay one is about a hundred less.

 

i believe they are the exact same turbo.. both sourced from cx racing. im almost positive that they both come from the same exact shelf..

.. on a side note, i just got a message from the female. my turbo is happily sitting home, waiting to greet me. so if you wanted to wait till tomorrow to purchase it, i can give you a quick visual review in the morning.

 

Sounds like a I can save a little money then. It leaves more for the T4 flange and some 3" u-bends from Columbia River mandrel bending.

Yeah, that'd be awesome if you could post a couple of pictures.

What were you planning to do for a manifold? What type of waste gate? Size, brand etc?

 

Rotaryworks = CX racing

~S~