I wanted to add a twin turbo kit to my MR2 engine it's a 2.2l and I found these turbos tdo25 by kinugawa for a motorcycle rated for 500cc-1000cc, so I need to be corrected if I'm wrong but but looking at the numbers Im thinking I can run 1 of those turbos off 2 of my exhaust ports and it be enough to build boost efficiently? I'm not looking for high numbers just proper functionality and add to the uniqueness of my build

 

Sizing a turbo strictly off of displacement is sort of risky.

What are your power goals? Any other modifications to the engine?

 

It has oversize pistons, oversize valves, head porting, 272 cams(biggest street cam), shimless buckets, bigger throttle body, custom intake manifold, and lightened pulleys

 

Those are really small turbos, they are rated for a 16-74 hp gasoline engine, They have a maximum flow 0f 0.07 m3/s, about 148cfm.

The 2.2L Mr2 motor is naturally aspirated from factory, when you built the motor did you build it for boost or peak N/A performance? I'm going to guess N/A because of the cams you put in. The cams will move your powerband higher in the rpm range, a set of TD025 will probably spool and run out of breath before you reach the best performance rpm for the cams.

What is the compression ratio.

About 23 years ago I cut a set of factory mazda 2.2l turbo manifolds in half (well runners 1, 2 of one and 3, 4 of the other) the plan was to swap them left to right on the engine and run 2 factory IHI VJ11 turbo's side by side but I got a found a junk yard T3 for 100$ and ran that instead, back then without the internet you used magazines, sales catalogues, local parts vendors and the telephone to find parts and information and I couldn't find a turbo for under 1200$ usd, so 2 turbo's on a 4 cylinder was a possible solution to maxing out the tiny VJ11 turbo.

But the problem with this kind of set up would be the exhaust pulse timing to the turbo's.

1 rpm is two revolutions of the crank to an amount of time , so at 800rpm, 1 rpm is 720* crank revolution every 0.075 seconds, in that time a 4 cylinder has 4 ignition cycles, 6 cylinder 6 and 8 has 8...
A 2 cylinder has 2 ignition pulses but both cylinders a in the same position (Like 1 and 4 or 2 and 3 on your motor) and they generally rev faster and higher.
Basically the turbo would be missing an exhaust pulse every 180* like a dead spot in the exhaust pulse
The 2 cylinder engine would pulse the turbo 1 - 2, 1- 2 but the four cylinder will be 1 (3 is pulsing on manifold 2) 2 (4 is pulsing on manifold 2) yes both would pulse the same number of times but the 2 cylinders turbo would spool quicker because the 2cylinder can rev quicker.

A V8 is like two large four cylinder engines back to back when running twin turbo you just size the turbo to a 4cylinder and buy two.
A V6 is like two 3 cylinder back to back.
An inline 4 is like two 2 cylinder engines but on is cut in half and fitted on both end of the other.


If the turbos are ran off runners 1- 3 and 2-4 the turbo would get two pulses and wait while the other turbo got two pulses...

I think the best way to run twin turbo on a 4 cylinder MR2 would be to run remote turbo's off the exhaust which is off the engine on an MR2. Run a short manifold into a collector some pipe and then a Y pipe to both turbos just put the turbo's here dual muffler would sit with two 6" long turn down pipes as downpipes, it would spit flames, cause dust to fly everywhere behind the car and sound like two small jet engines taking off.

You could do the opposite of any car and run exhaust from the engine to the front and put a remote turbo under the hood, if you did front fender exhaust dump on an MR2 that would confuse people.

 

1 rpm is 360°, it takes 720°/2 rotations to get the 2.2L of displacement.

Firing order is 1-3-4-2, to impulse drive a turbo the pulses must be evenly spaced. If there is to big of a gap between the pulses, rotor momentum slows too much, and the next pulse is used mostly to regain shaft speed instead of making boost.
So on a firing order of 1-3-4-2, 1 and 4 should be piped to one turbo, 2 and 3 to the other. Also, impulse driving means you can power larger turbines, going to smaller turbines is counter productive. BUT that is all dependent on your power/ boost goal.

 

Wouldn't the long runners not get a very good spool? I've made custom lines for my heater core cause the copper ones suck and are expensive to buy good condition pipes and we're talking like 10ft to actually read that far when you factor in all the bends to get that way

 

So, I found maps for the td025... #ad


Running the numbers, 250hp will require .095kg/s of airflow at 1.9 pressure ratio. Actually a really nice match, on the compressor side. Running the turbine numbers shows drive pressure will be upwards of 30psi. Way too small and restrictive.

Running the numbers for a single is 25lbs/min at 1.9 for the compressor, and 15lbs/min at 2.0 for the turbine. So the gbc22 looks like a good match

 

Thank you for breaking it down to me I'm going to look into this further I've looked at those maps when looking at turbos but it's hard to make anything of it.

 

Most maps aren't in metric. Most are standard with lbs/min.

What's important is you need 25lbs/min at 1.9 pressure ratio for the compressor, and 15lbs/min at 2.0 expansion ratio for the turbine. That's the design points you need for looking at all the maps. Just because I recommended the gbc22, doesn't mean that's what you have to go with.

For the metric maps, 25lbs/min is .173m³/sec, or could also be posted as .191kg/sec.

Every turbo manufacturer has a different way of mapping their turbine, so I won't even try to figure all those numbers.