I am of the understanding that in a V8 boinger 4-6 pounds of boost is very substantial. Ten or more is getting radical. Compression rings collapse, pistons get "hurt" and ****.

I read threads / comments about boost on this forum that leads me to believe that less than 10 is mild on a Wankel, 10 -20 substantial, and over 20 is getting out there. Is this true ?

Do Wankels need or can stand alot more boost than boingers ? How's that possible ?

Are the boost ranges ( what's considered mild, substantial, and radical ) "about the same" for turbocharger and supercharger ?

 

It's all about the compression ratio's.

That's why 6-10 lbs of boost on a V8 may seem like
alot. Because the majority of them are N/A engines with
boost added in.

Take a Mk IV Supra's 2JZGTE engine. Built for boost.
20 lbs is nothing on it.

Even Rotaries, have different compression ratios for boosted
applications.

 

For an engine to withstand high boost pressures it needs to be built for. That means things like lower compression, forged pistons and a tough bottom end for the horespower that comes along with more boost. Piston engines can run insane amounts of boost. For example the Cosworth Sierra touring cars over here were running in the region of 40-50psi back in the day.

 

It all depends on how overbuilt the engine is.
Low compression,rich running rotaries can survive a fair amount of boost,so long as the tuning is correct.Stock 8psi is for longevity and factory reliability,the stock 2MM seals will hold 14psi with little complaint.
A relatively low compression V-8 will handle a fair amount of boost depending on how detonation resistant the combustion chamber is(usually not very,but the physically large pistons and rods can take some punishment).Plus theres a lot of displacement to start with,so lots of boost isnt neccesary to make big numbers.
Honda's have a very effecient penthouse combustion chamber which is detonation resistant.But the factory takes advantage of this by giving the engine a high factory comp. ratio which is not boost friendly.My buddies healthy,50K GSR engine puked up 3 piston upper ringlands after only 2 months on 7psi boost,despite the excellent factory combustion chamber design.

The SupraTT block is a model of overbuild,as is the MR2 4 cylinder.Both have very tough bottom ends and solid cylinders/pistons, capable of making 2-3 times the factory HP with no problem.Toyota has always been "into" turbos,so they know how to make a boost friendly engine.Nissan is no different with the SR20 and Skyline engines,both very overbuilt with only minor weaknesses.On the other hand,imports like Honda,BMW and Mecedes have always leaned towards lighter,high tech N/A engines that have high volumetric effeciency, without the extra mass and overbuild needed to survive boosting.

 

I think what David is trying to ask is "Can rotary's take more pressure abuse than a boinger?"

For ex: N/A Bolt on Turbo FB
And N/A Mustang Bolt on Turbo

Then...there's

STI STock TURBO
RX7 TurboII stock

Like...what's the difference between high comp psi on a boinger and rotary...
Compared to a low comp psi on a boinger and rotary....

Like taking the examples above and saying:

For ex: N/A Bolt on Turbo FB - 10PSI
And N/A Mustang Bolt on Turbo - 7 PSI

STI STock TURBO - 12 Psi
RX7 TurboII stock - 15 Psi

Wankels CAN take more abuse than a boinger since there's fewer moving parts and it's higher revving. But when a high compression wankel is bolted on with a turbo, then it needs to be built. Simple as that. Same law goes with a high compression boinger. Not built, it won't take high pressure for long...

Just my two cents.

 

Way to many things differnt to make a general statement like that.
Plus there are plenty of people that take a stock 5.0 motor and stuff 20# of boost into it, just check www.turbomustangs.com
And for what it is worth, I was running an old ppinto motor 2.3 4cyl from a thunderbird turbocoupe. Stock boost was 15# on them. I had quite a few mods, but a stock bottom end running 30# of boost from a much larger than stock turbo. Made 422hp and 440 ft# of torque.

Later
Randy

 

But you have to somehow even it out to be comparing "apples to apples" so to speak... at least as close as you can.

We basically need to compare something stock, to something similar stock. So give me a stock mid-eighties sport compact that makes 100hp, and tell me how much boost it can take 1) without any trouble 2) if you don't plan for the engine to live more than six months

And then you'll know how to compare to an FB.

Jon

 

I was looking for a general "feel" for the boost ranges, but to be more specific and to the personal point:

For a 4 port rally ported 13B intended for more than occasional street use, what is the amount or range of boost ( supercharged and/or turbocharged ) recommended for the most bang without sacrificing longevity ?

 

Well, I've researched a little on this subject, but I think 8-10 psi would be good in your case. Even at those levels you'll be making 250+hp, which is starting to get a little unstreetable in a 1st gen.

 

Nah, I drive mine with 15psi on the street all the time

 

Yeah but we know that you ain't all there! I think davids startin to wonder ......Just what would it be like......To havea turbo rotary? Then he could act like most of the 2nd -n- 3rd gen owners and stick his head up his caput! Oh ****, that was your last avatar wasn't it Dave?

cheers

kenn

Dave, Excuse my obvious ignorance but WTF does STFU mean?

 

Shut the Fawk up.

 

not only that but if i did, my wife, and cat would leave me.....(hey thats a great idea, more money for the car! Ya finally came up with a good suggestion FB, now you can say I am Owned!

bwahaa haa.

kenn

 

I drove mine around on the street with 400+ hp at the wheels and a ton of torque. It was pretty decent, but 500 would of been better.

Later
Randy

 

Ok, you have to be quite an experienced driver to drive around with that much power. Really know how to control the clutch. But hey, if you want to have the chance of dieing everytime you drive the car, thats your choice.

 

No you dont...my gf could drive that car. Its all about pedal control See she would never even go past like 1/3 throttle so she would be fine in it.