Possible T2/T3 Hybrid Turbo Issues?

[mdb4879]

So I got to thinking about it because I remembered Dee saying he's made/used turbos with a small T2 exhaust side and a large T3 compressor and was wondering what issues there could possibly be with this and what needs to be taken into consideration when "designing" such a set up. I haven't really looked into this, but what I'm guessing is done is you use a turbine with a small A/R so you get a quick spool and a large compressor to get the airflow needed to make a lot of power. If you do this, though, eventually the small turbine will cause excessive back pressure and limit your power potential. So what do we do? We put multiple or a really big external wastegate on the exhaust manifold to vent off all the excess exhaust not needed to drive the turbine. Problem solved, right? Well, that's where I'm a little unsure. If you use a big enough compressor with a small enough turbine wouldn't the turbo in a sense spool too soon and cause compressor surge because the motor couldn't suck in all the air the turbo wouldn't be pushing out? In this case how do you find the line between quick spool and compressor surge? I know how to read compressor maps, but I have no idea where to start to determine at what point the turbo will spool to what speed based on the turbine and the mass it has to turn (the larger the compressor the more mass so I would figure a later spool, right?).

While typing this I think I realized if you were using some sort of standalone utilizing a MAP sensor you could vent off the excess intake charge to prevent compressor surge, but what about for those using MAFs? How do they overcome this?

[float_6969]

The issue with a little turbine and a big compressor is the risk of surge and choking at high rpms. The choking isn't fixed by a big wastegate. What actually happens is that the turbine is too small to move the volume of air needed through it to keep the compressor spinning fast enough to keep the boost up. Boost will fall off, EGT's will SKYROCKET, and if sustained, turbo failure will follow.

I can't sit and explain how to plot out airflow on a compressor map. It's way too involved. Sorry.

[mdb4879]

I think I get what you're saying. Kinda like putting a 3" cut-off wheel on a Dremel tool. It is capable of the speed, but the motor (turbine) isn't big enough to drive that much mass.

I can plot airflow on a compressor map. That's not a problem at all for me. I just don't know how to determine how fast a turbo will spool based on the manifold, size of the turbine, tune, etc. Or is there not really a good way to estimate that other than by what other people have and actually trying it out yourself because of all the factors involved?

[dash]

isn't that what a t28 is esentialy ?
most of em have the same 60 trim T3 compressor wheel
why reinvent the wheel ? far too may successful ca18 examples out there

[mdb4879]

Well I was thinking of something a bit more extreme. Idk what all the dimensions are so idk how one goes about mating different housings together, but I was thinking something along the lines of a compressor that would be efficient up to about 500-550bhp on a CA with the CA's stock, tiny 0.48A/R turbine. Idk if I'd even need a compressor that big on anything I will ever own, but just in case I was curious about the possibility. It seems like most T28's that would be good on a CA can make up to about 450bhp with I'm guessing a 0.64A/R. I haven't really looked into any T3 frame turbos though.

[s13drifter88]

Sounds like you're talking something like Garretts 3071 in T2 right? Atleast that concept anyways Im assuming.

Hi Dash, long time no see

[s13drifter88]

450 crank would be possible with a 2871 but it'd take some sticks and a solid tune of coarse. Chris is laying down 700 in his black 300 with a pair of .64 2871's. You could go for like an .86 3071 or I even think 3076 sized turbo and pull it off but external would be the only way you could control it and something like a Tial 44 would let enough out that it could keep back pressure down while and 86a/r would let enough in the hotside to keep the compressor at speed. The idea of an external wastegate preventing exhaust from choking due to back pressure in the manifold is plausible as Jeff demonstrated at Static years ago but only actually works when the a/r of the hotside can get enough in to keep wheel speeds up. Comp turbo has some nice frames and the Borg Warner EFR's are so far showing to be some nice leaf blowers. Reed down at Work Turbo in Birmingham is doing some pretty neat things with them but OMGWTF they are pricey. I would call Work and talk to them cause they build some pretty nasty whistlers.

http://www.compturbo.com/
http://www.workturbochargers.com/

[mdb4879]

Yeah, I was just interested and curious about the whole concept. I think that for MY ACTUAL goal (not an example like earlier) of 400whp it can be done with a 2871 (with a very solid tune as you said, of course). I'm certain it'd be a lot easier with E85, but I'm not to certain I want to try that or not. I pass 3 E85 stations on my 8 mile drive to work, so it's available, it's just seems so foreign to me though. But with everything else I'd have to do to make the power the only difference with E85 would be injector size and maybe fuel pump size, so my end price would essentially stay the same, so idk it may be good for me to learn about it. Plus now I'm unsure about what I'm going to do about tuning. I was thinking Nistune, but I've never done any tuning so when I read things about resolution and such I understand the concept but I don't know if or how much I maybe be hindered by not going with a standalone. Ugghhh, so many details and so much planning, lol,

Well, a little back on topic, lol, would a GT2871R (I know there are several) be able to flow 400whp with the small turbine housing (0.64 I think) or would the larger one (0.86 I think) be the only way to go? Obviously I want the fastest spool possible and broadest torque band, with the least restriction in the top end (don't we all?)

[s13drifter88]

Nistune will suffice anything a 2871 can do, standalone for a 2871 would be like putting a scope on Beretta 9mm. 2871 .64 for 400 wheel, enjoy stopping at a Sunoco for every fill up (110 is $9.xx a gallon). The .86 will get you there and with poncams, ported manifold and maybe a quick timing dip at your boost transition area in your fuel map it'll spool like a rocket. Obviously if you want 400whp cams are already in your budget and those will help with flow and a little more "push". The timing dip will help as well, when me and Harry tuned Wes's RB20 with Dustin's Nistune we pulled a degree or 2 right where boost started coming in and we noticed spool times drop by a few hundred revs and he has that hybrid that Reed at Work turbo did with that big P trim turbine wheel. A little DSM trick Harry said he learned from building those 4G's with Victor and Rhodes a while back lol.

If you want some crazy hybrid though Work or Forced Performance will be the best route but with a 400 goal an off the shelf 2871 (.86ar) will suffice. Now some people (who's name I won't mention till he makes himself apparent) might suggest going T3+ but I'm sure you know that'll involve a manifold, wastegate and pricey downpipe.

[mdb4879]

I'm not too sure what to do for a manifold either. It seems I remember the stock exhaust manifold can do it if I were to extrude hone it. A tubular manifold may be better for the flow, but I fear it may slow the gases too much and lower my spool time more than it may benefit my power gain. I'm certain that who you speak of may recommend a T3, and it would definitely be better to make the power, but Idk what sort of space constraints I may have in a FWD format (although I'm sure he has had a T3 in FWD). There is going to be so much modification to the car as a whole making room for a T3 shouldn't be a big deal, but even though some say not to bother trying to make power under 4k because a CA is useless under that I still want to make as broad of a powerband as possible. Even though I'd be pushing the limit of a 2871 on pump gas (probably not so much on E85) I think if done right I may get a better result closer to my desires.

So what would cause the 2871 to make the power on 110 octane but not 93 with a 0.64 A/R? Would the small turbine cause too much strain on the turbo and the compressor would just be blowing hotter air, causing the motor to be more prone to detonation?

From what I've been able to tell, there's no way a 2871 could even create enough pressure to force that much air into a CA on stock cams. So yes, cams are in the budget, lol. And I'm certain there will be a little intake manifold work and some head work as well (when I get there I'll figure out what's too much and too little).

So what would you guesstimate I could have full boost at, both with the 0.64 and second with the 0.86 A/R? For example, with the stock CA turbo (0.48 A/R), stock tune and all, I can floor it in fifth gear at 2000 rpm (so I can hit full boost at the lowest possible rpm) I hit full boost at 2800 rpm. So for that as reference, what do you think?

What I may try doing is going with the 2871 and maybe take the risk on the 0.64 housing and if I cant make the power comfortably I'll buy a bigger set of injectors and switch to E85.

And back to the exhaust manifold, I noticed that on Casey's motor (cbh148) with an S15BB turbo his compressor housing was really close to the manifold. That being said could a 2871 even fit on a factory manifold?

[s13drifter88]

The person Im speaking of about T3 is not who you think Im talking about lol

Race gas is like E85... you can run higher boost, a little more timing and a little leaner all which will yield more power.

.64ar - 35ish; .86 4k, maybe a little faster depending on porting, cams and tuning (Just a guestimate, Chris is making full boost around 3800 with his .64's with only 1500cc @ 3 pulses per turbo so I would think that an extra pulse with 300cc more would speed up spool a tad)

The comp housing on a 2871 is the same size his s15bb

[mdb4879]

The person Im speaking of about T3 is not who you think Im talking about lol

Whoops, my bad, lol

Race gas is like E85... you can run higher boost, a little more timing and a little leaner all which will yield more power.

Except E85 has a different power potential than Gasoline. I can't remember exactly what all the numbers are, but E85 makes less power per mas but takes more fuel to reach stoich, so it turns out to make a certain percentage more power per volume of air than gasoline. I want to say 30% more, but that seems a little bit high. I'll have to look it up again.

.64ar - 35ish; .86 4k, maybe a little faster depending on porting, cams and tuning (Just a guestimate, Chris is making full boost around 3800 with his .64's with only 1500cc @ 3 pulses per turbo so I would think that an extra pulse with 300cc more would speed up spool a tad)

I'm certain that with Nistune something can also be done with the butterflies to help make more low end torque which ought to help with spool, right? But if 500 rpm is all the difference I'd see then I may not even bother trying for the 0.64.

The comp housing on a 2871 is the same size his s15bb

I did not know that. Good to know to help me weigh out all my options.

[boost_boy]

Some how the mentioning of down-low torque and CA18DET makes me sigh. Obviously, I love the CA18DET, but this engine is not designed to give you a monster pull off boost, so I say to most, stop wasting time trying to re-invent the wheel. Those little T2/T3 turbochargers I played with produced more than enough power to make the CA18DET pretty efficient yet mean on any given Sunday. My car pulls/drive off-boost very well because it's the way I tuned it. You guys with your stock ecus can keep toying with the butterfly valves or evolve into much more useable systems that will allow you to be more flexible. Keep in mind folks that those old seals between the twin port intake runners do go bad and will cause you more ghost issues than you care to know. I mean, do what you want, but I learned my lesson years ago and got rid of as much of the factory stuff as I can because this engine is pretty old and crusty and stuff will fail faster than you can type. I'm just saying.....

[mdb4879]

It may make no difference because you may consider it the same thing, but I'm not trying to make power off boost. I'm trying to make boost sooner. Regardless I'm just trying to obtain info and make an educated decision on what route to take. If you would be so kind as to enlighten me with your methods, Dee, and converse on my options, please feel free to PM me.

I kinda figured that I would be right at the power line between help and hindrance with the butterfly valves. Being as such and probably being cammed I figured they may help in giving some more bottom end and aid in spooling the turbo. But if there are methods to help with that with the butterflies (properly) removed or with a four-port head then I'm willing to learn.

I think that overall I would be will to sacrifice some peak power to spool sooner and make a broader power band. Essentially my goal is to make this car a BMW so to speak (the ultimate driving machine). I want to make my torque curve (line) and flat and over as broad of an RPM range as possible. I think with tuning capabilities today and the technology in EMS's and boost controllers this can be done. I just figured the butterflies could be an aid.

[boost_boy]

It may make no difference because you may consider it the same thing, but I'm not trying to make power off boost. I'm trying to make boost sooner. Regardless I'm just trying to obtain info and make an educated decision on what route to take. If you would be so kind as to enlighten me with your methods, Dee, and converse on my options, please feel free to PM me.

I kinda figured that I would be right at the power line between help and hindrance with the butterfly valves. Being as such and probably being cammed I figured they may help in giving some more bottom end and aid in spooling the turbo. But if there are methods to help with that with the butterflies (properly) removed or with a four-port head then I'm willing to learn.

I think that overall I would be will to sacrifice some peak power to spool sooner and make a broader power band. Essentially my goal is to make this car a BMW so to speak (the ultimate driving machine). I want to make my torque curve (line) and flat and over as broad of an RPM range as possible. I think with tuning capabilities today and the technology in EMS's and boost controllers this can be done. I just figured the butterflies could be an aid.

If you are trying to make boost sooner, you should use a supercharger. The first 2000 rpm on the CA is IMHO "worthless" and that's usually where the butterfly valves engage and start doing whatever they were intended to do. Getting your fill of hot air as fast as you can is cool and all, but if the engine's timing is not compimentary, you may still end with semi-lazy dog once your little hair dryer gets the engine to wake-up. Because the CA is an engine prone to creating hot spots and is notorious for cracking ringlands, one has to be smarter than the engine think it is. Instead of over-timing the poor little engine throughout the powerband to achieve maximum power, you increase the timing before it gets deep into it's powerband and back-off timing once it reaches it's power threshold. This not only provides insurance (for a well-tuned engine of course), but allows you to eliminate that out-dated and clumsy butterfly valve set-up as well. Heck most, most of you don't even have the system hooked-up correctly as most CA swaps will not come with all the components to make this system function correctly. Unfortunately, to test my theory or better yet, to test what already works for me, you're gonna have to spend some money a real tuning system as epromming to achieve these results will get old annoying quickly. Hope this provides some better insight on this particular topic, now back to T2/T3 stuff.

You guys buying this little turbo with the massive .64 and .86 A/R exhaust housing are gonna develop some lag and not be able to take full advantage of the smaller and alleged effiviency of these turbos. The CA is a pump and that pump is physically smaller than the pumps that these turbos were either attached to or highly recommended for, so why take an S15 ballbearing turbocharger with a .86 rear housing and throwing it on a CA and then have the nerve to think it's suppose to spool like it does on the SR20DET? Be realistic. That S15 SR20DET is not only more advanced than the CA, but is also a bigger and better pump as well. So in short, stop being so quick to ditch the T25 completely. You can have the T25 converted to a T2/T3 hybrid whilst keeping the original .48 A/R housing that the CA came with from factory and put an end to your early spooling issues, your butterfly issues, your lag issues and a few other issues if done correctly. The turbo is good for around 18psi efficiently and was also onboard our old silver sentra that smoked the S2000, the WRX, the bossted IS300, the AudiTT and countless other unsuspecting chumps that scoffed at the old B12 sentra. Do not try to build this yourself and make sure a well know builder does this for you as well. Now, which one of you guys are truly paying attention to what I wrote? Experience is my teacher as well as my money, time and days of misery with this motor. Knowledge is power, so don't be a know-it-all and soak -up the knowledge from those who have paved the way and have journied the same beaten path you're attempting to travel down. The proper phrase is "Been there and done that" .

[s13drifter88]

Boost, almost sounds like what you described was a Garrett GT2559 lol. I clicked it on accident one day and saw that it was actually a pretty neat looking little hair dryer. Upon more research it seems to be almost identical to one of the twins off a 26 and looking that over seems like it would make a really neat match for the CA with a cool balance between response and top side with its relatively small a/r and near 60mm (2560 or 2860) compressor wheel. In a nutshell though, for a good bang the S15bb (GT2560R) T28 is hard to beat. They respond well and pull quite nicely on top. While the one I bought and installed was for an SR, which as Dee said is a whole 'nother animal, the difference made was quite impressive. Now, if you dont want to drop on one of those, Forced Performance offers what they call the Big 28 which is done inside of T25 housings. Another member on here ran one of these ( post6145313.html?hilit=xiaphin#p6145313 ) and made some great power http://store.forcedperformance.net/merc ... gory_Code= , here is his dyno results http://s191.photobucket.com/albums/z50/ ... 78_NEW.mp4 . From what Ive seen and read (and you should research them too) they seem to be pretty explosive and do quite well