Steve400bhpCossie

Hi from the UK.

Over the winter (now until about april) my cars going to be off the road, and its having a new engine, basically, i was going to do a 600bhp version of my curent engine (Cosworth YB Turbo), could give you details (jus ask and il tell you), but itd produce around 520-550bhp at 32psi held, then i was gona add 100bhp of nitrous (direct port) when drag racing. This would be fine and reliable for road use, easily 15,000miles of hard driving (its jus a weekend "fun" car, not a daily driver).

BUT ive been thinking...

Why dont i fit a 20B....

Am i right in saying a 20B lump could do mush more than 600bhp@Flywheel (on 97octane) without the nitrous and with not too much stress and bother?

Whats the maximum youd say a turbod 20B can produce (on 97octane) and be fairly reliable as a street car (to last around 15,000miles at least)?

What mods are needed, mainly engine internal details pls.

Id prefer to run a single huge turbo or 2 big turbos, rather than three smaller ones, purely on simplicity of fitment. What turbo(s) would you reccomnd?
What boost pressure would they run?
Whats the useable rev range of a 600+@fly 20B??
On a 500+Cosworth engine (without nitrous and the anti-lag switched off) the power band is from around 4500rpm till 7500rpm, not exactly huge, and would prefer a larger band (as well as the more power!).

Also, what kind of PRICE are we talking about here? (bearing in mind i will need to source the base engine) The exchange rate is good for me at the moment to buying stuff from Oz and the US is quite cheap!

Room for engine/turbo(s) is not a problem, the 20B engine is MUCH smaller than the current Cosworth YB.

Fabricating mounts is not a problem.

Its basically a road going racecar its going into, stripped out, cage, buckets, the chassis already upto the job, massive brakes, coilovers, polybushes etc. Even my current intercooler will come in handy, its MUCH bigger than any ive seen on an Rx, much bigger than even uprated Skyline GTR intercoolers.

Transmission wise i was going to use the current Tremec TKO 6speeder and 9" rear diff, and get a custom bellhousing made to mate it up to the 20B.

Also, anybody know of any other good tuners websites and other bb's that specialise in the 20B? Esp one with parts price lists...

There MUST be a large Oz BB about rotary's (esp the 20B as they seem popular there), any web addr's please???

Only one ive found is 3rotor.com, which is good to look at, but no techy stuff (and a bb that nobody uses!).

Thanks, its a big post and a LOT of questions, but itl be worth it.

Actually, if anyone wants ill post up some pics of the car its going into, and 2 video clips (and the bangs n flames on the launch will kinda show u i mean business!! lol)

THANKS IN ADVANCE!!!

Steve

Bridgeported

A 20B can easily make 600 flywheel hp.
If you take a stock 20B, streetport the intakes, and up the boost to about 15 psi (stock turbos), you will make about 500-550 rwhp. (575-632 at flywheel)

So yes, the 20B can EASILY get 600 flywheel horsepower! Just upgrade to a LARGE (as big as you can get) turbocharger, a stand alone ems (which you will need anyway with the swap) and all the other items (fuel system, intercooler, drivetrain, etc). To get 600 flywheel hp (510 rwhp) with a 20b streetport running a huge *** turbo, you probably can acheive it at 13-18 psi.

My project for next winter will involve a bridgeported 20b running about 22-25psi. Not sure on the turbo(s) yet. My goal is 800+ rwhp.

Steve400bhpCossie

Aaaaaaah!

Superb, thanks mate, 20B it is then!

What would be the powerband be on an 600bhp streetported 20B with huge single or twin turbos? Basically when would the turbo kick in and what does a 20B rev to?

If 600 is THAT easy, then il have more, 13-18psi is nothing really.

The 20B will be rebuilt, so porting and any engine internal mods are fine to do.

Whats the difference between street n bridgeport in price, power, and drivability?

Im happy to do as much mods as possible until it gets STUPIDLY expensive, or badly unreliable. If i can go 700/800/or more flywheel BHP on a 20B before it gets badly unreliable n far more expensive than 600flywheel BHP, then ill do it.

520bhp before the nitrous on my current engine is pushing its limits (a Cosworth YB is only 2litre!), so as long as this engine could last 10000/15000miles of action before a rebuild then its fine.

Im guessing more than 600bhp would cost me little/no more than jus 600 as im going to be buying the engine alone, no turbos or ems, and rebuilding the engine, so immediatley ill be going to get some huge turbos and standalone EMS, porting the engine, and already have an intercooler that can more than cope.

God, ive put you even more questions to sort now!

But il REALLY appreciate it if you could answer em, as nobodys got a clue in this country! 20B is the best kept secret over here (i honestly think there are les than 10 20B lumps in the entire country...).

Thanks again for any and all help (i need it!),
Steve
(BTW the name says 400bhp, its more like 450bhp, holding 30psi boost)

Turbo 3

iTrader: (3)

Do a search, there are plenty of web sites out there for 20B's. Here's a start though:
http://www.northstarrotaries.com/links/

There's even a http://www.4rotor.com/ if you want. I know there is a company in the UK that has 3,4,5, and 6 rotors. If you ran a 4 or more rotor configuration with a small street port for reliability and breathing, you'd easily be in the 600+ flywheel range.

The Mazdaspeed site and company in CA will have replacement parts for you to rebuild your 20B. If you look a little further down the page, MVAMotorsport is selling a complete kit to drop in a 3rd gen RX-7 for $35K. You could get it a little cheaper because you won't need some items that the kit requires, subframe, oil pan upgrade, etc. It would definitely save you a lot of time having to try and find all these parts when someone can do it for you in a one-stop shop, already having all the engineering done for you.

If you want to run more boost that's fine but you can't pressurize these motors into the 20-30's range without a lot of strenghening of the motor so it doesn't twist itself apart. You'll need to dowel pin the motor, different apex seals, probably lighten the rotors, shotpeen the housings, etc. It's not as easy as just adding more boost, things will break quickly.

Streetporting, Bridgeporting, J Porting - do a search. There's plenty of info and pictures on other threads. The general rule of thumb however, is the bigger the port, the less reliable over the long term it becomes because you add extra heat to the water seals. Sounds like an option for you if you don't mind rebuilding every 15K however. It'll put you into the 800 flywheel hp range quickly but your powerband will move from having a lot of low end torque to not a lot until 3-4k, but your powerband will go up to approx. 9-10k. They normally redline at about 8-9k, depending upon your safety factor.

The motor should cost you about $4K U.S. plus s/h. If you can do all or most of the fabricating and welding yourself, the conversion should be in the $15-20k range for your power wants since you have most of the car already done. It will most likely take you a lot longer than one winter to finish if you have no idea of where to begin with suppliers. That's the biggest battle, finding stuff that will work and fab'ing to make it work.

Barwick

dang.. I wasn't aware it was that easy to make mad power with a 20B.. now spending money on my TurboII with a 13B, I kinda feel like I did when I was modifying my Civic.. heh..

not really.. but man that's a lot of power for not a lot of heavy mods

Bridgeported

We'll it's not quite as easy as I might as made it sound. It's still a lot of hard work and expensive parts to get it running great.

Pineapple Racing www.pineappleracing.com sells 4 rotor engines which they claim make over 850 fwhp. (NA!) The price is $8500 USD.

twin_turbot4

does anybody know how to drop a 20b cosmo into an 88 rx7? i have yet to find anyone who has done this. any help would be really helpful.

bcool

FAQ section and $10K is a good start.