Hi All - I am new on here so hope I have posted in correct area.

I live in the UK, and am currently building a new race car powered by an Evinrude Two Stroke V8 with 3.6 litre capacity delivering about 325hp at 6500Rpm. Also using a Supreme Tools CVT transmission.
I have two major problems to overcome.
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Here is the car - a 1996 Prosport 3000

NOISE: With open exhaust it measures about 145db and I need to get down to 105db to pass the static noise test before I can race. Last weekend I visited a race meeting where a Turbo'd 4 stoke - 2 litre car was running. He had a Turbo fitted and passed the static noise test WITHOUT any muffler! It appears a Turbo reduces noise levels BUT do they on a two stroke?

Water COOLANT temperature: These powerheads are normally found on the back of a boat where there is a plentiful supply of water at 60F. So how do I create a maximum exit temperature from thermostat of 135F with ambient air temp of 80F? I have investigated injecting/spraying CO2 in front of the radiator etc. Latest thought is to instal twin Turbos. One Turbo feeding the air inlet plenum and the other ducted to the radiator. In the ducting I can instal water injection into the hottish air, and by evaporation,use the change of state Enthalpy to cool the air flow.

EFI. I am installing 16 injectors. 8 into the cylinder crankcase using 40:1 oil to provide bottom end lubrication and then 8 into a new port into the cylinder pulsing fuel only after the exhaust port is closed to provide the correct mixture considering the extra Turbo air volume. I need lubrication so cannot consider cylinder head type injection.

ANY help/advice/thoughts appreciated.

 

I was a National Sound Chief for about 10 years. Tough to get the cars to pass that 105 DB check at times.
You are talking a MASSIVE "noise correction" with your deal. 145 DB is many many times higher vs 105 DB.
Do not know if even the turbo could lower it that much, only testing would tell.

Tom V.

 

Hi Tom
Yes, I built a development car using a f500 chassis and fitted the Rotax 600cc twin cylinder + expansion chambers. Got this down to circa 108db with stinger design but I finally had to enclose the expansion chambers in noise absorbing material to finaaly achieve the 105. I am on a BIG learning curve with this powerhead. I am 73 years old so its my last BIG project.

 

Is the 145dB of the tuned pipes with or without the turbine? (I assume it was on the Rotax?)

Are you planning tuned pipes for the V8?

 

Hi
The 145db is on the V8 without Turbo using the original OMC expansion chamber design which provides a final exhaust of all 8 cylinders via a 5" x 3" rectangular outlet, normally under water. Currently not converting to 8 separate pipes. These V8's have been tuned to 550+ hp without Turbo. I will be happy if I can get a reliable 400+hp using a Turbo(s) + EFI + a bit of porting.

 

I've run multiple Rotax twins and triples both with open stingers, and turbos with short open down pipes. I don't have any real data, but the turbos are much quieter, at least until the gate opens.

 

Hi Mnix
Thanks - I am OK with gate noise as I only have to do a static noise test at 3/4 of max RPM. Were you running EFI or carbs? I am also looking for info on a startup map on the ECU.

 

fascinating project .

 

I've run both carbs, and Megasquirt. There isn't much info on efi two strokes, so I used tunerstudio to approximate some settings, and tuned the old fashioned way. It wasn't as tough as I expected though.

 

Thanks Mnix - I am going to use the Megasquirt for EFI but initially retain the CDI ignition system.

I have so many potential problems to investigate once I get the engine running what with EFI - mapping, water flow/temperatures, Etc. Since I am installing the crankshaft horizontal, I have lost the normal pulsed oil feeds to the crank main bearings. So I am fitting an external oil pump & distribution system to feed the main bearings. All this needs checking before I start running to max RPM.

So ?????. I want/need to try the turbo(s) mainly for the exhaust noise reduction. Initially I will have enough things to investigate that I am considering running the turbos but NOT turbocharging the engine. Once I get everything else sorted, then I can contemplate supercharging and re-mapping to suit. Can I run the turbos without any back pressure on the compressed airflow or do I need to instal a plenum with a pressure relief valve?

I am looking at using the Aerocharger Turbo which is self lubricated. Any comments on these units?

 

I have since gone back to carbs (Mikuni round, or flat slides), they're simple, and very easy to tune with just a few mods. You need to have the compressors plumbed in to keep turbo speed in check. The Aero's have both good, and bad points, but most have gone away from them because of their cost, and reliability. I (and most kit builders) run Gt series ball bearing Garrett's. They work great, and require very little oil.

 

Hillclimber,
What are you doing with the exhaust? Normally a 2T V8 is piped as two V4 engines to use the blowdown pulse from one opening cylinder as the plugging pulse for the next closing cylinder.

 

Hillclimber-
Latest thought is to instal twin Turbos. One Turbo feeding the air inlet plenum and the other ducted to the radiator. In the ducting I can instal water injection into the hottish air, and by evaporation,use the change of state Enthalpy to cool the air flow.

Whatever fan/compressor you use to cool a heat exchanger you want to use the inlet side of the fan/compressor on the outlet side of the heat exchanger so that you do not have the added heat of the fan/compressor outlet blasting onto your heat exchanger.

Good idea to use water injection onto the heat exchanger. If you preheat the water before spraying it onto the heat exchanger it will evaporate faster and you can increase the amount of water injected/evaporated this way.

As an alternative, you could cool the power heads directly with injected water evaporation and have the outlet of the powerhead's cooling jackets hooked up to the turbo compressor inlet to draw out the steam so more water can be injected.

You will have to calculate the run time and how much weight of water would be required versus the weight of a conventional cooling system.