20B Mild Port Street car - what turbo??
 

G'day all,

Am rebuilding a D series 20B atm and a series 5 to receive it also. Everything's being done right, water/ oil cooling system, intercooler, brakes, drive train, shocks, wheels, tyres and a full 20B mild port rebuild including all the right mods to make the engine strong and reliable.

I know I have to make a decision soon with regards to what turbo to run, and it's proving a difficult one. Though I have done a lot of R&D on the subject I'd really appreciate some suggestions from those who have already faced the same decision.

I know the 20B will deliver 600+ HP without breaking a sweat (with the right turbo of course), but the lag would be notable - or would it? I've driven many a car, but never a 20B, so I really don;t know what sort of torque it delivers off boost.

Appreciate all suggestions and thoughts!

for being easy to get id go with like a garret 42r. a t88 greddy. or a precision pt76 maybe somthing bigger like a pt 88 or somthing, the 42r i know aspec makes a turbo kit for the 20b using that turbo and it should spool up quickly with a ported 20b. probably as fast as a t04 on a 13b, dont know from experience but from the research ive done on the 20b its just a guess. be sure and post pics of this project we all wanna see, it never gets old

I would say a GT42R, dual ball bearing would be a good option for you. It'll spool up quickly and deliver easily over 600 WHP. The beauty of the 20B is the immediate low end torque available. This will get you going quickly regardless of the turbo you select.

I have the T51R from www.aseturbo.com on my 20B. It will also do 600+ but there is a big debate with my mechanics over how much more than that is is capable of producing. From ASE's website:

GARRETT T51R

The T51R is a turbo for serious contenders wanting to make power figures up to 1000hp and is well suited to larger capacity 6-cylinder and rotary engines.

ASE Price - $2,783

If/when my electrical issue is sorted out, I'll post up the dyno of the turbo and then we'll know. My guess is we'll push close to 700 WHP at about 21 or so PSI before the turbo runs out of air. This would be plenty good for me though and much more than can be driven on the street.

That's mate. Have seen others have used the GT42r with moderate success. A Billet GTS-76r is also on the cards, but I don't think it will spool up until 4000rpm - which for me is too much lag. Once said, my 13BT is moving approx 165 cfm at 3500, while the 20B should be pumping 218 cfm without boost at the same engine speed. That equates to around 114hp for the 20B and 150 for the 20B at 3500. My 13BT doesn't put out that sort of power until around 4100rpm atm - which is very noticable positive displacement.

Maybe I'm overthinking the question; once said, that's why I've asked the question ;)

Thank you for your info =) I hadn't heard of the T51r before, so it gives me more research to do! (groan ;)

But you see, this is the question I'm constantly stuck with. It's not all about power, it's about drivability. Why am I building a 500+ rwhp car when using that much power on the street is next to impossible. Maybe, just maybe, I should lower my power expectations and aim for 400+rwhp and pick a turbo with less lag? Or am I just too used to driving my 13BT and can't concieve the power delivery of the 20?

Sorry guys not rambling, just typing my thoughts...

I think you are just too used to the 13BT and its characteristics. Regardless of the turbo, with the 20B you are going to have low-end torque and this is what will get you going fast. It's very different than driving a 13BT, much more like a V8 (or I guess it would be like a 9 cylinder). Because of the torque, you won't have noticeable turbo lag and the car won't take until 4,500 RPMs to kick in. If you use something like the GT42R or the T51R, you'll be quite happy. The car will take off much better than the 13B and you'll get all the top end HP you'll ever want. If you want to stay in the 400-500 HP range, then turn down the boost and enjoy the ride. At 14 PSI, you'll be in the 450-500 range with the above two turbos. It's nice to know the extra power is there so I would go with something that will get you in the 600-700 HP range.

Now if you put a monster turbo on the car like what Gotham Racing is doing (see their posts in the 20B section), you'll have lag but once that baby hits, what a crazy ride it will be! I don't recommend a 1,500 HP car for the street though:)

Enjoy the ride!

FYI - speaking of doing everything right, are you planning on balancing the rotating assembly? This is a must IMO. I'd also consider the Xtreme Rotaries stud kit although it was a pain in the ass for me to get the machining right . You are in Australia though so have Rohan at Xtreme Rotaries do the work for you. He would also be a great person to ask about the turbo sizing issue.

Hiya,

Okay, sold. Looking closely at the Garret gt42r and the Billet gts-76r.

Yes, balancing and re dowling is happening as part of the rebuild. Once said, will talk to Rohan this week. This is the sort of project that I don;t want to have to re-visit after a mistake. I want it to be as right as possible day in the first instance. Thanks for the referal!

Thanks to all who commented - everything said was informative and in the best interests of the project and it's keen to enjoy owner!

Cheers!

PS: Yes, I'll take some picks and keep all posted with progress :)

^Regarding "doweling", don't, do the Xtreme Rotaries stud kit instead. Call Rohan and ask him about doweling versus stud kit. He can do the machine work for you.

Hi mate,

No worries, am looking to it currently, so fingers crossed the right decidion will be made. I still have the engine apart atm, so it's the perfect time to make the direction decision.

Have to say, it's not the first car I've rebuilt, but it's certainly the most exciting.. Well, second most exciting (DB4 takes the cake). It will certainly be the fastest!! ;) ;)

Cheers to all!

Here's to your success! Post pics!

"Lag" is relative...

I dunno what you're trying to build or what racing you're trying to do, but a 500+ hp vehicle is going to be STUPID FAST.

The 20B already makes so much torque that complaining about lag doesn't make any sense.
In fact, if you want that hard of a turbo "hit", you probably can't get any traction unless you're running racing slicks?
Rereading your first post makes me scared on what you're trying to do...
Really, at this point, the lag might be a GOOD thing, as it allows the car to still keep traction under boost...


-Ted

Hi Ted,

It is really isn't it. It all depends on what you're driving and have driven. Am talking about lag here.

Also, I agree. The 20B as we all know can easily 'easily' make 680 hp at the fly. But other than in a drag application it's a case of 'now where am I going to use this?' That's why I am likely to take on board David's advice and limit the boost to 8 or 10 pound. Even so, it will be very quick and now that I have charted cfm and hp throughout the rev range of my 13B verses the 20B, I can now understand why people say lag in a 20B isn't really noticed.

From one of my earier posts:

You see I agree, so don't be concerned. It's about drivability, not who has the most horses - well, unless you're aiming for a record quarter.

Thanks for you're feedback and I'm glad to see that I'm not alone in thinking there is such a thing as too much.

Cheers

David,

Some good news! Well, more! Going with Extreme's studding solution for the 20B, and yes, DEFINATELY will be balancing the entire assembly. I'm open and keen for any more suggestions from all. I mean, that's why I asked the questions. Wanna do it once, wanna do it right.

BTW, Turbo decision will be between the GT42R and the Billet 76GTS. Both will be perfect for my needs, so I think it will come down to dollars and serviceability in the end.

Cheers!

i think tial makes a stainless exhaust housing with vband for the garret, ligherweight housing, and allows the turbo to be rotated if need be for any fitment stuff. that and hell it just looks cool, lol

Sounds really good. For the studs, make sure you take your irons and housings to someone (Rohan) who knows what they are doing or they could really mess things up. Regarding wanting to do it once, I would consider the NRS ceramic seals and an AI system. How about your coil setup? I ran LS1 coils but found they broke up at anything higher than 14.5 lbs. of boost. A lot of guys will upgrade these to Jacobs or MSDs.

Yep, Rohan's doing them - it's all sweet. Definately running ceramic seals. Using 6 Bosch coils with high powered ignition system to still make a strong spark even with water injection. I'll be talking to Rotamotive on Monday (the engineering shop that's doing the rebuild) so will clarify what's going in. The engine is apart atm, one bad rotar (which was expected) but no other big surprises. So I'm pretty happy. Will post more when I know it myself ;)