i'm in process of gathering some of the parts required to do this. anyway, engine displacement is 2.5l, rear of engine has common exhaust chest. i currently have a wolf ecu running a similar engine naturally aspirated, and the wolf is boost friendly. my current injectors will support 450 hp, so i could add 2 more injectors to the plenum(wolf will fire up to 12 injectors). engine is a 60 degree v6, hp target is 450-500, rpm is 7500. what would i select for a turbo? i'd like something with an internal wastegate. i was considering a large t3, the ones i just picked for my camaro are good to 500-550 hp, but don't have an internal wastegate. i would also like a water cooled housing, and already have the oil system planned. thanks guys!

 

I run a stg 3 t3 .82 a/r on 780cc @8800-9000 rpm that makes 150hp n/a. What does the engine make for n/a hp? The 2.5 2 stroke will require the turbine for a 5.0 4 stroke given equal ve.

 

current hp is 240 crankshaft. i just don't want something thats laggy, i'd like to go into boost around 4-4500 rpm. hp n/a probably will drop a lil with stock lo compression heads. i could get the n/a hp up by raising the exhaust port height, but figured it would be best to leave the port timing alone-i am basically going to start with a steel bore 2.5/200 hp block and put better tdr reeds in it made for boost, and forged pistons. i also will try to intercool it.

 

Stock port heights typically work the best, especially with a log type exhaust. Without doing any math, and just taking a guess, a p trim turbine, and compressor in the upper 50's to low 60's wouldn't be too far off.... but you'll probably want to go gt series, and a bb would be nice. We have the luxury on our sleds of having a cvt transmission, so we go from idle to max rpm, and stay there, little bit different load than what your outboard will experience. Also just a note from my experience.... a small turbine will kill pistons quickly.... even forged with good fuel. The piston crown cannot take it, so turbine selection is critical. We have run stock cast pistons for 3 seasons with some questionable tuning at times with a proper turbine, and have killed sets of forged pistons with a restrictive turbine...... sucks at $500 a set.

 

here's the turbos i went with on the camaro project, http://www.ebay.com/itm/CXRacing-T3...s&hash=item2575451cf7&vxp=mtr&afsrc=1&afsrc=1 exhaust seems close to the p trim, and they are water cooled. only downside is no integral wastegates. i was thinking about shooting it with water injection(with a big tank!), alot of time we go do runs that are 150 miles plus, i usually cruise-80-90 mph(between 4500-5500 rpm). i am going to use a set of forged pistons i have from customer takeouts when i do rebuilds. the forged pistons from mercury racing for these are 2k$/set!! they are used in there nicasil race blocks and use a titanium/nitride ring set-the rings alone are 450$/set!! insane. i'm running a steel bore(stronger) so i'll have to come up with a ring set. the merc race stuff is top pinned too(don't have to worry about locating pins falling out)

 

The exducer is close, but the inducer is a fair bit smaller. The load will higher on your application than it is on ours. Since you're in unknown territory, i'd look for something that has multiple a/r options. I also wouldn't go t3, or smaller than a p trim sized wheel, but that's just my 2 cents.

 

what would you recommend, i'd like water cooling as i have an abundance of water, cooling the turbo will help keep the oil temps down. also if possible something with a built in wastegate. i was also thinking twin scroll, i've read of people putting a butterfly valve in one of the scrolls to shut it down to build boost faster, and install an actuator and let the computer run that part of it. i just looked on ebay and i'm lost,lol!! there are so many choices!

 

Do you happen to have a dyno sheet for this or something similar? Everything we run have expansion chambers, so these outboards are quite different.

 

i do not have a dyno sheet for it, i've built alot of them. i do remember the last one that i fully modified, it made 320 propshaft hp at 7200 rpm, and was making 280 at 6k, but you have to add 20-25 hp to the propshaft numbers. that engine was na but high compression and fully ported with a stuff crankcase, relieved exhaust, etc. most of the hi perf stuff is based on the 2.5 engine. on the engine i want to do stock hp would be 240 at 6k rpm, naturally i want to turn it around 73-7500, and i didn't want to touch the exhaust timing, so the boost hopefully will extend the rpm range, you can turn them higher then that with stock port timing(people turn them 8k plus in that configuration) but power curve stays flat or falls off. that engine comes stock with smaller 5 petal reed cages, i will be going to 7 petal reed cages in it.

 

We really didn't notice a power improvement from more reed area when turbo charged, the key for our sleds was to find reed material that would hold up.... they tend to flutter, and some had issues with a lean pop, and petal breakage. The forced induction does tend to extend the power band, in my case it was only a few hundred rpm, but with chambers there is a very small window of power, and it falls like a rock above that window.

 

i got you. i don't think there is much exhaust scavenging/tuning going on here. here is a pic of the exhaust chest. left and rite sides are divided by the exhaust cover, which incidentally is water jacketted. i'd have to cut the cover, weld the exhaust jacket closed where the flange is going to be. #ad

 

incidentally, the width of the cover is aprox the od of the t3 flange. also, the bottom of the block has 2 rectangular openings for either side(i'll blank them off), they measure 1 3/8" by 2"

 

the edit function isn't working! tdr(tony doukas racing) makes reeds, he does them for all my engines, and could probably make yours if you send him an old reed for a pattern, and he has experience turbocharging banshee engines(350 cc twin). looks like a t4 gasket id would line up perfectly with the inner od of the exhaust chest

 

I found a set of petals for mine that have been holding up. My sled is actually pretty easy on reeds, but the one I built for my dad likes to eat them.... he has tried a few different materials, and now has a set of heat treated stainless petals that have been holding up. What material are tdr's? I was always amazed at the power that could be made with the Mercury's with expansion chambers..... there is a local guy that used to run them on dragster-like speed run sleds. These engines are not my area of expertise, and like I said before, anything I chose for a turbo would be an educated guess. There must others that are turbo'd that a guy could use as reference, as I hate to steer you in the wrong direction.

 

i haven't had any luck finding anyone, so your help would be great! years ago land n sea made a turbo kit for a 2.4 merc, it was blow thru carb, and wasn't successful, people blew engines left and rite with them, had no ign control or anything like that. the kits are pretty rare and i've been unable to get any info on it, but was also done back in the '80s so turbos have come a long ways. as far as the reeds, give tdr a call, he makes them out of different thickness materials and uses fiberglass or carbon fiber. i wouldn't want to use stainless steel, the production mercs use them and its pretty bad when one breaks, which happens regularly if you try to spin them over 6500.

 

Yeah, the stainless isn't very forgiving, but they have held up well as these are drag only sleds, don't see much run time, and get some regular maintenance. We both have tried carbon fiber, and had breakage after a couple races. The next time i'm looking for a set, i'll give them a call though, thanks for the tip.

 

your 2 cents is worth way more to me then 2 cents! is this turbo similar to what you think i need. if not please tell me what specs you think i need to make this work. this compressor seems large though. this is still a t3 though. what is your opinion of controlling flow to one of the scrolls? http://www.ebay.com/itm/T76-Turbo-C...Parts_Accessories&hash=item4d15997a03&vxp=mtr

 

That actually looks to be a T4 flange, but the compressor is larger than you need, and could possibly induce some surge if boost comes in at a low enough rpm. I would stick to something about 60mm, but the turbine is what I was talking about. I like this turbine (even though its old tech, and there are much better out there) because you can get a/r's from like .58 to at least 1.30. With a fresh supply of cool water, this thing is also begging for a w2a intercooler.

 

for what its worth kids around here are running the 60-1 60mm compressor t 4 p trim on thier 3.0l supras which are 4 strokes (power stroke every 4th stroke)

i would think a 2.5l 2 stroke (power stroke every other stroke) would act more like a 5.0l 4 stroke

i agree mnix on the turbine and the compressor (60-70mm)

id go with a s366 or a s360

and take this as a grain of salt, i have very little 2 stroke experience

 

Yeah, the turbine will make or break (literally) the combo, and they do act twice their size. The thing about 2 strokes is that many of them have expansion chambered exhaust systems which make them much more efficient than their non chambered counterparts. Its just as easy to over turbine them as it is to under in a setup like this where a fairly broad powerband is needed, and these actually turn a reasonable rpm, much slower than most i'm used to. If it was run on something with a cvt clutch like a sled, and had chambers i'd say go big on the turbine, but like posted earlier, i'd try to set it up so as to be able to swap a few different a/r's, or possibly the complete turbo with something larger/smaller. Just to give an idea the differences between chambered, and non chambered setups (there are many other differences, but this being the main one) my .779 liter 3 cyl makes 150 hp stock on pump fuel.... 192hp/liter, whereas this 2.5 liter at 240 hp is at 96hp/liter, and it has a constant fresh supply of coolant. When I was researching my setup I had access to a dyno test where I could calculate ve numbers across the rpm band, and used that to get a rough idea of when it would spool, and the turbine I needed.