Supercharged ChevyV-6/V-8

[Joe Patterson]

I had a very nice conversation with Mike today, and between that and the information offered here from all of you; The way I figure it,.........Supercharger NO / Turbo Maybe .........I also learned today....that................... even if I use an Aviation Engine

( Lyco/Conti ) I will be able to work on it myself.

 

 

This is an important part, as I will need to keep my overall cost down.

 

If I use the Lyco-360(that mike is gonna use)-Well not that one, but one like it-I will have 220 HP @ Sea Level...........Reckon what that will give me @ Altitude ????????? 60 % ???? or so.....

 

wow...... What a learning curve this day has been.

 

I have about a year to get this engine stuff under my belt, maybe less.

 

Need I say it............Thanks for all the input, and bare with me .........I will get it, my head is not as thick as my Mom says it is.

 

Notice I spelled Bare incorrectly

[No4]

Just picking nits with a couple of earlier posts, there is only one turbine in a turbocharger. The exhaust gas exits the exhaust manifold and drives a turbine, the turbine is connected via a shaft to a centrifugal compressor.

 

Native Spirit,

At 8,000 feet you definitely need a supercharger or turbosupercharger to name it correctly.

A centrifugal compressor is a flat circular disc with a series of vanes or fins if you like on it's face. As it spins at many thousand rpm air is accelerated off the ends of the vanes into the casing. The speed causes compression in the casing and on into the manifold.

A centrifugal compressor has an effective compression ratio of up to 3.5 to 1, and the air mass flow rate, or horsepower, decides the size of the wheel. ie big turbo big hp; small turbo small hp.

 

So if you "turbo normalise" an engine not usualy turbocharged, it provides no boost at sea level, and then maintains sea level pressure until the ratios drop below 3:1.

What does this mean? well, a simple turbocharger will maintain you sea level power to about 20,000 feet (critical altitude), and then the power drop off will be the same as a non turbo climbing from sea level.

75% power will be available at 25,000 feet.

The turbocharger actualy becomes more efficient in an aircraft at altitude, because on one side it still has the same mass flow of air at the same high temperature, yet on it's outlet side the static air pressure is 1/3 (at 20,000) sea level pressure. Hence a greater pressure ratio, and more work done by the compressor wheel.

Choosing an engine that requires boost at sea level, and the critical altitude is reduced. Choosing a NA engine and adding a turbocharger, you have to be very careful not to overboost the engine at lower altitude. The continental and lycomings use low compression piston to allow for some boost, and even then require careful engine management.

 

http://www.nar-associates.com/technical-flying/turbo/turbo.pdf

 

TURBOCHARGER Vs SUPERCHARGER

 

A supercharger can be of several types, but each basicaly compress and pump air, the compressor being driven by the crankshaft. Once the compressor has been sized, and it's optimal rpm decided on, it is relatively straightforward to match the gearing from the crank to the compressor. Horsepower from the crank is used to drive the compressor. On the exhaust side there is no restriction, so heat build up in the exhaust manifold, at the head, in the valves is not such a problem. The effects of altitude cause the exhaust gasses to flow much easier from the exhaust ports, and therefore as the piston (rotor) rises to exhaust the gases less resistance is met, so a slight reclaim of the hp taken by the compressor.

 

A turbocharger as previously described is driven by the exhaust gases, and mainly utilises the rise in heat of the exhaust gases which would otherwise have been wasted. It is harder to get the sizing of the turbine and compressor just right. A centifugal compressor works best between 70 and 95% of it's designed rpm, outside these speeds it is practicaly useless.

The turbine chokes the exhaust causing back pressure, and a rise in temperature at the valves and head.

 

A gas turbine engine can be made from a simple truck turbocharger, they have a burner can instead of cylinders for the combustion process.

It is generaly proven that a turbo is much more fuel efficient than a supercharger.

 

[Joe Patterson]

Thanks No4.

 

You guys are great..........I think I am gonna cry.

[No4]

Nativespirit,

In case you havn't guessed I'm firmly in the aero diesel camp.

The Thielert Centurion turbo diesel aero engines come as a 135hp or 335 hp unit. They are based on Mercedes 4 cylinder and V8 engines. They are turbo normalised, standard with constant speed propellor (improved take off at altitude),no spark plugs, no risk of detonation (in fact when it stops detonating you start to worry!), run on cheap diesel or Jet fuel, and the decider for me, a much less flammable fuel source in the event of an accident.

 

Going into Theory land, actually the finest supercharging system is the turbo compound recovery system as seen in DC-7's and on the Connie.

A two stage supercharger fed air into the 3350 cu in radial producing over 3000 hp, and in the exhaust a turbine was linked by a hydraulic gearbox back to the crankshaft. The turbine was installed to try and trap the heat, and dampen the flames that were frightening the passengers.

 

Regarding the reduction drive,

1, If a 360 cu in Lycoming with vintage injection system can achieve 180 hp at 2700 rpm, then I'm sure a Chevy 350 cu in can match it.

2, My Nissan Skyline with an RB25DET (2.5 turbo six, 24 valve, 350 bhp) howls at 5000 rpm, and sounds and behaves like it is the ideal rpm, at 2500 rpm she does not sound so happy. The pistons are changing direction more often at higher rpm, but twice the number of cylinders means a shorter stroke, so piston speed is halved. I think the piston speed of a V12 Merlin at 2500 rpm is faster than a 1100 Kawasaki at 11,000 rpm.

 

3, Whilst I agree entirely a psru adds weight, becomes a maintenance factor, sucks shaft horsepower, there are some advantages.

The Lycoming / Continental's propellers are mounted directly onto the engine's crank. Any forces or vibrations are felt right through the engine.

 

A psru can act as a dampner between the prop and the engine. Also the gears inside it must be the weakest link . As we discussed in the retractable gear thread, a gear up landing results in the likely death of a lyco/conti motor. I can't back this up, but I imagine the shearing of the teeth might save the engine. This could also apply to bird strike or the prop shedding a blade.

Also, judging by the latest turboprops, it appears a slower spinning propeller at 1200 rpm is advantageous to the traditional 2500 rpm, which I suppose is only decided by the Lyco's.

[LargePrime]

When is a nit to small to pick?

 

Total energy of the piston at the top and bottom of the stroke is THE determining factor in engine longevity. The slower you spin an engine the longer it will last. Piston velocity is a kind of red herring in that metal over metal velocity is not a wear issue, but the velocity will add to the energy that has to be delt with at TDC and BDC. Cranks (and all metal) dont like the tension but love the compression.

 

I understood the turbo compound engines where straight geared back to the crank. Thanks No4.

 

3, Whilst I agree entirely a psru adds weight, becomes a maintenance factor, sucks shaft horsepower, there are some advantages.

A proper PRSU (see how I define my way around issues, hehe) will;

be a non matience item. Tracy cooks is pretty close to 0.

"Suck" less than 2% HP, probably less, and I doubt it could be measured accuratly it is so small.

 

Also the gears inside it must be the weakest link . As we discussed in the retractable gear thread, a gear up landing results in the likely death of a lyco/conti motor. I can't back this up, but I imagine the shearing of the teeth might save the engine.

I would rather a PRSU that handles prop strikes gracefully, like an appropiate sized shear pin or some such thing.

 

A centrifugal compressor has an effective compression ratio of up to 3.5 to 1,

Not strictly true. If you find one that can do it let me know, but higher ratios are relativly easy with a larger diameter. Most turbo's (about all) are used in automotive applications and a small diameter is used to minimize lag. Even the truck applications use this to get the high volume price break. The turbo F1 engines used to run 90psi with one 11" turbo, and had very high efficency.

 

The turbine chokes the exhaust causing back pressure, and a rise in temperature at the valves and head.

Interestingly I am reading a book by Corky bell on turbochargers. He mentions this very thing and spends some time on it. He suggests it is not a big deal and that if one could get an appropiate turbo (larger, he seems pissed at OEM's for the small ones they put on cars) one could use the high pressuer boost to scavange the cylinder with fresh air and see a 15% power and a small efficency gain. An idea much more suited for diesels I would think.

[No4]

Largeprime,

I havn't done the maths, but I think comparing a V8 to a four cylinder, at the same rpm, the pistons will be smaller and lighter and travelling at a slower speed. Plus this force is split over 8 cylinders so more harmonic for the crank, whereas a 4 cylinder lyco will have heavier pistons which need to accelerate and decellerate to/from greater speeds in the same timeframe, and experience a more uneven load.

The 2 stroke diesels definitely need forced air to scavenge the cylinders. The four stroke will run better with more boost, also no need for wastegates or dump valves, let it pump as much air as it likes.

I'm sure special turbos can produce more than 3:1, that F1 engine sounds like 7:1, but most charts I have seen for turbos have a compression ratio of 0 to 3.5 on the vertical axis, and mass flow rate along the horizontal.

[Jim Sower]

... A centrifugal compressor has an effective compression ratio of up to 3.5 to 1, ... a simple turbocharger will maintain you sea level power to about 20,000 feet .... 75% power will be available at 25,000 feet ...

I had thought that 3.5:1 would "normalize" you much higher than that. 1000/3.5 ~ 300 mb or a little less. Looking only at pressures, I recall that the 500 mb level is right around 18k', and the 200 mb level around 35k'. That would put the 280 mb level at maybe something over 25k'. Now, take temperature into the equation and you have a density altitude of .285 which would indicate your 'critical altitude" (and onset of power decay) occurs at something on the order of 28-30k' wouldn't it?

 

But of course this is all pretty academic. Turbo normalizing to 20k - 25k would require the prop from hell. You'd need a CS unit that could be pitched pretty coarse and very wide blades. Your mission profile would be a little wierd, you'd have to be IFR on a hard altitude ALL the time, O2 ALL the time and a pretty robust cabin heater (whose weight might help offset some of that mass back aft.

 

As to diesels, it was brought up that a reciprocating mass is bad for engine life - ALL of the components involved, from the crank and main cap to the wrist pin and piston - and even the block. The higher the pressures on the piston the more detrimental to the engine. Isn't that why the really reliable diesels (like on generators and line haul trucks and the like) have power/weight ratios of arouond 0.2hp/#? Additionally, diesel compression and power stroke numbers abuse bearings hellishly. Which is the aero diesel that has no TBO - you just junk it after 2000 hrs? Do those folks know something we don't about what happens to structure when you pare down the weight to meet aero application requirements?

 

As one might infer, I much prefer three moving parts and a rotating mass. The fuel specs aren't as desireable as a diesel, but the power/weight ratios are quite good and they have enviable reliability (race teams running recips rebuild their engine after every race - rotary teams rebuild at the end of the season - whether it needs it or not:)). A rotary costs something on the order of $3000. Firewall aft (engine, PSRU, fuel and cooling systems) can be set up for under $10k if you only do it once. TBO is unknown at this point but indications are that it could exceed 3000 hr. A rotary can be rebuilt for around $600:).

 

Props are another matter. CS props cost a fortune (both to purchase and to maintain). One that could provide a Cozy with efficient, full power cruise at 25k' and 200-250 hp may or may not exist at the moment. They weigh a lot, and are located where that weight will do the most damage. For the money, I'll take my ~220 hp NA to 15k' and cruise at something upwards of 200 kts and spend all that other money elsewhere. $30k or more for a turbo-diesel engine, $12k for CS prop will bankroll my $10k - $12k firewall aft, a nice radio stack, a brand new BMS EFIS with all the trimmings and an Infinity retractable gear.

 

I'll TAKE it!!

[dust]

Thats what i am doing

 

heater from hell

 

cs $10,000 prop - mtv-d/ld168-101

 

enjoy the build

 

Mike

[LargePrime]

The higher the pressures on the piston the more detrimental to the engine.

Not true.

 

The higher pressure actually cushions the piston as it hits TDC. BDC is the same(boost or no boost) as the Exhaust valve is open. The tough spot is TDC of the exhaust stroke (which is the same, boost or no boost) as there is no cushion and it's all tension. TDC on the exhaust stroke is tougher on the engine than about any boost level you going to get with gasoline.

 

Isn't that why the really reliable diesels (like on generators and line haul trucks and the like) have power/weight ratios of around 0.2hp/#?

Nope. Diesels have horrible power to weight ratios because no one cared. Diesel engine technology has gone no where in 50 years, until now. Currently there is a revolution going on in diesels. The power to weight ratio’s are gaining quickly on gas, and they are bringing there incredible BFSC with them.

[Jim Sower]

Originally posted by LargePrime

Not true ....The higher pressure actually cushions the piston as it hits TDC ... BDC is the same(boost or no boost)

I was alluding to bearing loads at TDC and during the [early part of] power stroke. Do reciprocating acceleration loads exceed compression and combustion loads of a turbo diesel?

 

...power to weight ratio’s are gaining quickly on gas, and they are bringing there incredible BFSC with them ...

No mention here of the company who is actually flying that diesel that you have to throw away after 2000 hrs. Or why Zorsch and all those folks have been "developing" aircraft diesels for 15 or 20 years and have not been able to get anything light enough and reliable enough to fly. The loads on the drive train of a diesel are HUGE compared to gas engines. Absent compelling evidence I will have to be very skeptical of diesel engine having the same weight as a gas engine of similar displacement. Someone's going to have to show me the science on that part.

[LargePrime]

Do reciprocating acceleration loads exceed compression and combustion loads of a turbo diesel?

Yes, but that’s not the point. Compression Loads are a non event compared to the Tension Loads at TDC exhaust. It's not that the numbers are higher, its that the materials are less capable of handling the tension load than the compression load. If we have a assembly that can handle the tension load it will take the compression load without complaint. Ask a crank engineer what they design to and they will say tension load.

 

"Maximum Boost" by Corky Bell explains this in detail.

 

As well the mentioned revolution in diesels are using multi stage injectors that address just this issue. Not because it needs addressed, but because of efficiency reasons.

 

A multi stage injector injects a small amount of fuel to burn early in the injection. As this fuel burns the pressure in the cylinder raises. When it gets high enough a pin on the injector is pushed back and a flood of fuel enters the cylinder under pressure. This does a few things. It takes the sharp edge off the cylinder pressure (which wastes energy) and it creates a very clean burn as the fuel burns much more evenly.

This technology has the net effect of reducing the peak bearing loads, but as i said thats not a big issue in the first place.

[No4]

Hi Jim, I was waiting for you to get here,

 

1/ 3.5 is the upper end of centrifugal compressors ability, there best efficiency is around 2 to 2.5 :1. 20,000 feet is 466 hpa. You could be right, and it may work up to 35k plus, I hope so.

 

2/ Yes Yes the prop from hell, I like it. If I can afford the Thielert, (which is unlikely) I'd be a fool to dump the CSU. I've been working on a fixed pitch prop for the Volkswagen V10, it makes 400 hp at 4000 rpm, and 230 hp at 2000 rpm. I'm planning a reduction drive of 3:1. If the prop is designed for 300 mph at 1300 rpm, it should be good for 150 mph at 700 rpm. At this speed it will be delivering 230 hp, 50 hp more than a standard I0-360 with a prop set for 200 mph at the lesser horsepower.

 

3/ Yes Yes Oxygen all the time, not planning a big heater, but wooly socks, mplafleur's heated motorcycle suit combined with a pressure suit, furry leather jacket, silk scarf, goggles, and a nice leather flying helmet. I might go as far as to rig a pipe directly from the compressor outlet to pump any unused hot air from the turbo.

 

4/ Yes Yes the Thielert is expensive, but it is certified, and comparing it to the Lyco I think it might be cheaper. I'm sure you could either not junk it at 2000 hrs, just rebuild it yourself, or build your own auto conversion, and then we are into the price range of the Rotary. Mercedes Benz, Volkswagen, Volvo, Peugot, all make diesels which are now light enough to fit in a plane.

 

5/ Plenty of Thielerts flying down here, the flying schools love the 130 hp motor, with orders for the V8 to go into the sightseeing Cessna 206's at Queenstown. Fuel figures show a saving of 10 litres an hour in a similar aircraft for the 130 hp. All the businesses have worked out it pays for them to go diesel.

 

6/ Diesels have twice the compression ratios of gas engines, rings are usualy the first to go, then the head. It's expected, I won't be surprised by it, I'm already planning to replace the rings at regular intervals.

[Jim Sower]

No4,

Sounds like you've got it worked out as thoroughly as Dust.

I bless you. I wish you well. Keep us posted on progress.

Jim

[dust]

i'll take that as a complement

 

enjoy the build

 

Mike

[cncdoc]

Sorry I couldn't get back to you LargePrime, I had to drive 600 miles.

 

Quote:"I know of no EFI systems that use the crank sensor as an input to the flow Pulse width Modulation.

Could you point to any referance that says that the Fuel injector PWM function concerns itself with the port opening event."

 

I suppose you were referring to a stand-alone system?

The one reference I can give that offers an answer is the Haynes manual for 86-91 Mazda RX-7 page 114 I can't reprint it legally, but the part that I was talking about is the first sentence that says that the ECU alters the the injector opening duration among other things using various sensor inputs etc etc.

 

 

A throttle body injector is a whole different story, but I thought we were helping the gentlemen understand the basics of "general" theory of the benefits of a stratified charge. PWM is a side issue of the timing I was talking about. It's more important for attaining peak power/economy than for pure function. A carb will work on a EFI engine if you mount it in front of the intake where it used to go.......

So the ECU takes the data and compares it with MAF, TPS, CPS Camshaft PS (Ford) and other sensors and then times the opening and duration of each single injector in a multiport injection system. It has to be coordinated with the ignition timing to work.

As far as a "port opening event": Camshaft position sensors provide that information to the ECU on some typical piston engines. The Rotary doesn't have valves so the rotor acts as a valve when it turns and allows opening to the combustion chamber. The CPS is the only practical way to get this info to the ECU for injector opening and endurance and ironically, it's what MAzda used in many of their RXs. To change "valve timing" in a rotary, you have to physically change the port opening.

 

In the early days of EFI Volkswagen had a system that didn't rely on pure electronics (I had a Scirocco with a little EFI engine that ran like the dickens.......whatever that is) It used a seperate injector in the throttle body for cold starting. Now, the ECU can control the duration of newer systems and they just make the duration longer.

 

 

Does that answer your question?

[LargePrime]

This web site explained what I needed

 

http://yarchive.net/car/fuel_injection.html

 

It seems BMW in 83 doesn't think the valve opening event is that important, but Chrysler in 97 does.

 

http://www.stealth316.com/2-injectortypes.htm

 

Thanks cncdoc! I learned something.

 

P.S.

http://www.kinsler.com/m_efi.htm

I had never heard of SEQUENTIAL FIRED only "GROUP FIRED".

[Jack Morrison]

To set the record straight:

In 1996 I originally installed an all aluminum supercharged 300 hp V6 chevy in E Racer 113 in the mark 1 location, behind the cockpit seat, running a driveshaft to the rear of the AC coupled to a marine reduction drive unit. This engine produced 287 hp at 3600 rpm and was a great engine for the AC. The only problem I had with this engine is the radiant heat generated by the exhaust manifolds running alongside the upper longerons, burning paint on the center cowling and onto the top of the strakes. It got so hot that when Shirl Dickey was test flying the AC, it was softning the main gear fuse holders and popping out the fuses. It was a good thing I had designed a manual drop lock

for the main gear, there were no plans system. Shirl spent about 10 days with me trying to resolve this issue with absolutely no results to control the heat in the cowling. Shirl tried to make it to Oshkosh in 1996 but had to turn around about 10 miles out of ARR. I asked Shirl if I could install the Chevy engine aft of the firewall and he told me no because of the plans called for a aviation engine behind the firewall. I should not have listened, the Chevy with the supercharger complete less the redrive weighed in at 365lbs. At 4200 rpm develops over 300 hp. My SEFI540 LYC weighs over 500 lbs. but develops 380hp. I did not feel the mid-engine setup was safe and decided to pull the Chevy in 1996 and spend the next two years installing the IO540. I spent another two years developing the automotive supercharger to adapt to the LYC. engine. I sold the Chevy engine to another E Racer builder in Florida, he is mounting it behind the firewall with a bolt on redrive. In my opinion, this is where it should have been all along. Dont discount the Chevy V6 as an engine option, it performed well and was smoother than the LYC.

Heres what I changed on the LYC engine. I had lycon 3angle grind the valves on new TIO540 cylinders and flow match the heads, and balance all components. Stock 8.2 pistons and special cam grind on the cam. I installed a programable automotive EFI system (F.A.S.T.), an automotive throttle body, 2 Jeff Rose electronic ignition systems, two electric fuel pumps and a Vortech automotive supercharger. After many trial and errors, I finally reached my objective. I completely understand what John Slade is going through turbocharging his rotary. The superchargering answers I was getting from the (experts) in the field did not apply to my application. Very frustrating. Trial and error, trial and error, and I finally found the solution. Here is what I get. I am running a 64/113 three blade Catto prop. I do (not) have a wastegate. I control HP and MP with throttle . At 2000 rpm, 40 MP, alt 760, I can take off and climb out at 1500 fpm. The higher I go, just add more throttle, increases Mp, increases Hp, maintains rate of climb. At 10000 36 MP at 2950 rpm. That should give me SL pressure at 15000. Very fast. This prop is new and I have not finished my testing yet but should see great results. The only time I have pushed this engine at low altitude was leaving RR this year. Low approach at 275 mph, 2910 RPM,57 in Mp, climbed out at 5400fpm to 6000, 3200fpm to 8000. I would not think of changing this system,and if you do not push the system, It will never cause detonation.

 

Jack Morrison

[Hennie Engelbrecht]

Weight Issue

 

Someone is South Africa added some length to the nose end of a CozyM IV, and changed the shape of the nose to make it a bit more pointed( I like the way it looks), but it gave him enough room to put the battery up front(counter-balance, offset the weight of the supercharger is my thought) , I am wondering .

 

I have seen the cozy you refer to. It belongs to Jannie Versfeld. He is installing a 540 into his cozy. He will use the battery to offset the additional weight. I will ask Jannie if I can post a picture of his plane. It looks absolutely beautiful and is almost finished(exhausts, radio remaining)

Hennie Engelbrecht Qatar