8v 2l Twin Charged -my Little Project

[Biba69]

Gosh buzzed, it wouldn' be any fun if something doesn't go BANG! Yes of course kidding. Without going back over all of the replies/comments, do you by any chance have access to an engine test stand? I would think being able to run it before installing might well save a lot of time. On the other hand, I can also see where it could also be easier to install the engine, then build the components around it - especially the plumbing.

A shame picking up and moving has had to somewhat get in the way of your working on this project. Again kidding. I have no idea how someone could concentrate on both at the same time.

Biba

[Greg Gordon]

gtv27:

That is indeed a WW2 era picture. It's the type of system used in the P47 Thunderbolt.

Buzzed:

You are correct in saying that aircraft are very different from cars. The single biggest difference here is that the engine in the diagram shown is designed to run at a constant RPM. However power varies all over the map because of the variable pitch (constant speed) propeller. So it does see a wide range of power. It also sees a HUGE range of boost. At sea level it only needs about 8psi to get its 2000+hp. At the aircraft climbs the turbo boost increases as high as about 50psi in order to maintain 2000hp.

So this thing actually sees a much wider range of operating conditions than any car, with the exception of RPM.

Greg

[Duk]

Good to see your project moving along.

I believe you're on the right track with your turbo requirements.
I'd be looking at the Garrett GT30's or maybe 35's for what you're after. Deffinately be thinking .86 A/R turbine housing, 1.06 A/R is probably a bit big and 0.64 A/R probably going to choke your flow. Exhaust manifold design will be critical to reduce pumping loss's (back pressure), and so I highly reccomend that you look at the way othe high HP turbo manifolds are made by the likes of HKS and TRUST. Log manifolds work (poorly ), but they will compromise your whole engine's potential.

A mate of mine has a 500 hp Garrett GT30 turbo (can't remember the turbine A/R), on a 2.6ltr Sigma (factory Sigma turbo), injected (reprogrammed TP Magna computer ), intercooled, ported head, excessively large cam and a very low 7(ish):1 compression ratio. The way that thing gets onto boost (read: very quickly) and pulls to it's rev limmiter (7500rpm) is impressive to say the least. Although the car hasn't reached it's full potential (it's getting a programmable computer soon), an Alfa with that kind of torque curve would be some serious fun, but also easy to drive because of the linear/progressive nature of the engine.

[buzzed]

Biba69 - I don't have access to an engine dyno but have seriously considered building one in the new shed I am building...May have to settle for setup in the car for now though, time wise, at least for engine 1.

Greg:
Ah yes, I see what you mean, so does mass flow at the engine inlet vary a lot also? Mmmm 2000hp...must...have.....enter 'best Homer drool impersonation'

Duk:
Yeah I had an rx7 s3 13b with GT3540 turbo and ported. On 16 psi that thing was good for 245rwkw's. The rear end on that was a .86, with the way a 13b works its equivalent to a 2.6liter motor. With the supercharger, I think I may be able to run a 1.06, without it, I would just run a 0.86 for sure. The supercharger should give me ample mass flow to spool the 1.06 nicely....I think...maybe :-)

[Greg Gordon]

I wouldn't worry about turbo spool up time or boost threshold on this engine, the supercharger will take care of those issues for you. I would make sure the turbo can flow a lot of air, at least enough for the target horsepower and a lot more than the supercharger.

Buzzed, I didn't want to make this into an aviation discussion, but since you asked, and it is your thread here goes.

The mass air flow in the compound system shown in the G.E. diagram I posted actually stays about the same when at full throttle, throughout the engines huge operating range. It uses something normally called a "density controller". This device increases boost to maintain a certain density or mass of air entering the engine in order to keep horsepower the same. In other words, full throttle at sea level will result in about 8psi and 2000 horsepower (it's a really big engine, turning really low rpm). As the aircraft climbs atmospheric air pressure and thus density decrease so the turbo feeds in more and more boost to keep the air density, and thus horsepower constant. Thus at 40,000 feet it has something like 50 pounds of boost and still puts out the full 2000 horsepower. The density controlling is done entirely by varying the turbocharger's speed. The supercharger runs at a constant speed.

These same "density controller" systems are still in use today. Most, if not all Lycoming turbocharged aircraft engines are set up this way.

Greg

[Duk]

Quote:

Originally Posted by Greg Gordon I wouldn't worry about turbo spool up time or boost threshold on this engine, the supercharger will take care of those issues for you. I would make sure the turbo can flow a lot of air, at least enough for the target horsepower and a lot more than the supercharger.

[buzzed]

Greg: That make's sense. I think you are adding to the interest of this thread anyway, and my education! I am not too concerned with the spool up time of the engine so much as the transient response of the turbo, as I agree, the supercharger will help cover 'lag'.

Duk: I keep forgetting that you run a twin charge setup already. Is it in series and do you switch the supercharger off or leave it running?

As for my Mazda, it had a 5 page feature in Zoom Killer conversions.

I've done my turbo sizinf numbers based on the following assumption:
2liter engine running 10psig from supercharger equates to a 3.3liter NA motor. So I ran my numbers on a 3.3 liter motor running 15psi from the s/charger. I then chose a turbo based on the toral mass flow of the engine but at only 15psi, since this is the pressure the turbo will need to supply but at the total mass flow.

I've settled on a GT3582R turbo from Garrett. My calculated curve ranps up through the meat of the effificeny range and only drops to 74% efficiency (from 79%) at full load, whilst the midrange will pass back and forth through the peak efficiency island. It has the added bonus of being able to supply the total mass flow at 25psi with ease, which means I can test the setup in turbo and turbo+scharger modes to compare. Extenally gated and with aT3 flange it will suit my application nicely. I will use the 1.06 turbine housing. At 1650 AUD from Horsepower in a box it's a steal...cough. I spotted them for 1299 USD at JNZ but by the time you factor in exchange rates and postage it's not worth the hassle.

Head is back from the machine shop, engine reassembly starts wed next week. I had Turin imports send me new top and bottome timing chains...cheap insurance at around 50 dollars each.

[Duk]

Quote:

Originally Posted by buzzed Duk: I keep forgetting that you run a twin charge setup already. Is it in series and do you switch the supercharger off or leave it running?

[buzzed]

Glad you liked the Mazda Duk, I loved driving that car. Actually if you want to see a freinds rotor start for the first time about a week ago, go to this link:

YouTube - Chris Baraciolli's Rx7 13bt project

he's running all my gear that I amassed for another project that I ended up bailing out of (Mazda 1500 13bt). He's running all the cosmo gear in a s2 rx7. He's done all the work himself, and I mean everything, with just advice from myself and others. He's even fab'd up rack and pinion steering, a point of perfection sorely missing from my conversion. Don't know if you've driven rx7 s3's with recirc ball steering....but they are bad...real bad.



Point noted on photos, they'll be coming shorlty as I will grab some of the newly done head and block as I assemble it with my mate.

[Duk]

Quote:

Originally Posted by buzzed Don't know if you've driven rx7 s3's with recirc ball steering....but they are bad...real bad.

[Biba69]

buzzed, you're busted. Super1600 posted a photo of your Alfetta he recently took and it looks like you're just playing around when you should be back with your nose to the grindstone, if not the lathe working on on your 'little project'.

You owe it to your international audience. You can alway play later after you've finished your homework.

Biba

[PSk]

Quote:

Originally Posted by Duk Drove a s2 with a sloppy 'box (minds out of the gutter, please ()), not the best experience, even tho it was a stock 12a with extractors .

[batman]

The alfa steering box and all those joints isn't anywhere as good as a proper well designed rack and pinion steering
I fitted a Triumph Dolomite Sprint steering rack to my race Alfa Sprint GTA,Its just perfect!

[PSk]

Quote:

Originally Posted by batman The alfa steering box and all those joints isn't anywhere as good as a proper well designed rack and pinion steering I fitted a Triumph Dolomite Sprint steering rack to my race Alfa Sprint GTA,Its just perfect!