T25 challenge...cont.

[MikeMurphy]

To start off, I have mentioned this in 2 other forums, but I was also looking for some ideas from NICO. I was hoping for some of your folks' thoughts.

So I have been thinking about a very small boost application for quite some time now. I ask you guys this,

Why cant I just make a custom turbo manifold that connects to only 2 exhaust ports, and have the other 2 run free into the downpipe? It seems like the perfect solution! It would either be bolted onto 1&2 or 3&4 obviously. I was thinking that it should be good for about 5psi (which I understand the stock injectors to be good for with some fuel controller) for most of the powerband and with only 1.2L of displacement going through the turbine, backpressure should be at a minimum. Only 2 pulses at 1.2L would take a moment to spool it up im sure. The weak part of the setup would be the compressor, but thats fine.

Your thoughts? I know only using some of the exhaust ports is NOT something that is practiced, but why not? I cant see why it wouldnt work well with a small turbo setup. Someone please pop my bubble with a well-constructed arguement.

Any comments welcome.

(recap, boosting all cylinders, but driving turbine with 2)

[theronin]

what is the point of it? i mean why? sounds interesting dont get me wrong... but WHY?

[MikeMurphy]

before someone does, please dont tell me to not cut corners on cost. This is theoretical stuff were talkin about here.

1- T25 is so damn cheap2- Want very low-boost setup to play with3- Want VERY low backpressure to make the most of the boost4- walbro and a z32 filter would be all the fuel mods needed.

[theronin]

ahhh, ok interesting

but dont the cylinders fire in a different order? like 1-3, 2-4? or am i smoking crack?

[MikeMurphy]

Yes, 2 pulses at 1.2L would be pretty slim pickins. It would have to be attached to 2&3 to even out the pulses.

[MikeMurphy]

What im thinking is that you could EASILY package this entire turbo package for probably around $500 and get at least an additional 45whp with low backpressure.

[j-z]

like he said WHY? what youre saying doesnt make any sense at all. WHY? your mani-exhaust setup is gonna cost you since it will have to be custom made. if you want to boost do it the right way. get a jgs log, t3 super 60 with .48 a/r and you can run 5 psi with that. and those turbos are on ebay all the time for cheap! no intercooler, just a straight pipe to the tb. inline pump for $50 and a 8:1 fmu for $60. the ka will spool that thing like theres no tomorrow and you will have instant response. to me that seems alot more logical and alot less work and cheap as hell too.

[MikeMurphy]

T3 would be far more restrictive at 2.4L than a T25 would be at 1.2L. In other words less backpressure would mean that the 4 or 5psi would make a whole lot more power for ya. I could just as easily run 2.4L off the T25 and get 4 or 5psi pushing out 25whp, but thats not fun.

[andrave]

you would see boost early on with either a T3 or a T25, it would just drop towards redline. You aren't going to make any more power running the T25 off only 2 cylinders, it would probably just make it spool up later in the powerband and possibly make less power since its debatable if it would fully spool at all off only 2 exhaust pulses... I'll know more about that in a few months.With a T3 you could use jgs log style to keep cost down and you will hold a few pounds of boost to redline, and make 7 psi or so up to 5k rpm or so...dunno, its an interesting idea though.you could be the first to try it and see how it worked...

[MikeMurphy]

Thanks andrave. Im analyzing the idea in itself, instead of comparing it to other ideas. Im wondering now if it would net any positive pressure at all since its pushing in so much more air than what the turbine is using. I wonder how the hell I could derive the numbers?

[Jonny 290]

Think about it. The only reason that a turbo even works is that it can generate more energy from the exhaust flow than it 'costs' to keep it spun up.

if you have four cylinders of air being pushed by only two cylinders of exhaust pulses, it's going to be very hard to get enough exhaust flow to get any appreciable boost.

[MikeMurphy]

Good point. But im stubborn and will go figure out some numbers sometime in january probably.

[C-Kwik]

Aside from the technical reasons not to do this, consider that it would be just as easy to build a manifold that accomodates all for cylinders into the turbo. It's not like the two free cylinders would use the existing(stock) manifold anyways. And it may be more cumbersome to have to merge the two free pipes to the downpipe. It may be harder to fit this way as well.

[theronin]

hmmmmmm this is all so very very interesting

[Xero]

tuning will be horrible...

remember, a turbo creates ALOT of backpressure, you'll be running really efficient on 2 cylinders, and less efficient on the other 2. You would either have to run individual injector trimming, or compromise in both areas, it wouldl sorta neglect doing it.

In all actuallity, you wouldn't be saving anything, you'd still have to make all the parts a 4-port turbo system would. IMO, it'd be a waste of those other 2 cylinders,

[raging panda]

I'm not too sure about this, but do you want all cylinders to be even in most aspects? If you used two cylinders to push the turbo, only those two would be working hard, and the other two would flow easily. It just doesn't make sense to me, but I might be wrong. Otherwise, why do people work so hard to get the right sized piping for the headers, or other things like that.

[TrunkMonkey]

you're gong all the way around the block just to get next door.

for 5psi, it would be cheaper, easier, and you'd have less lag if you used the t2small with a conventional setup.

-demetrius

[Jonny 290]

Take the JGS unfinished log manifold, and rotate the flange 90 degrees along the axis of the pipe so that it's now a side-mount manifold.

Now move it between the #1 and #2 runners, and visualize it tilted approximately 20-25 degrees up (bring the compressor inlet up). Now you could possibly weld another flange between #3 and #4 runners, at the same angle. The downpipe would be easier, but still not simple. Wastegate is simple, mount it dead center on the log, on the bottom side.

The other setup that I thought of involves the same manifold, only having one turbo top mount, and one bottom mount. You could keep the manifold symmetrical that way, but dear lord would that take up some space. Possibly one side mount and one top mount?

Corky Bell says that turbine oil drainage is good up to about 30 degrees off vertical on any axis. i think you could do it.

boom. twin turbos, spooling quick and hopefully moving plenty of air. i'd pick turbos that would fit well on a 1.8-ish motor, and would be able to flow at least 25 lbs/min each at good efficiency and psi.

[andrave]

I'm doing a tubular manifold for twin skyline turbos, I just ordered the parts from JGS...I'll find out more about how it would all work in a bit....

[ca240]

you could probably do some highly mathematical tuning with the exhaust piping sizes and length on those free cylinders to make it flow the same as the turbo ones would...but as demcj said "you're gong all the way around the block just to get next door."...good luck man

[Checkered-Member]

MikeMurphy

you keep saying T25, they put those on accords and preludes with a 2.2L engines

Look into T20 they are dirt cheap and will spell up faster, and most of them are Ball Bearings, they use them on B16's (1.6L) should be prefect to run 1.2L

[andrave]

you would want it either on cyls 1 and 4 or 2 and 3. anything smaller than a small T25 and I don't even see the point in bolting it on, it won't make more than psi or two of boost on a larger engine like the ka.

[RMiller]

What if you just clip the turbine wheel and port the housing...alot, and direct exhaust from all 4 cylinders to the turbo. Then you would have less backpressure like you want, and the backpressure would be equivalent for all cylinders.

[SeVa-S13]

High RPM Heat Pump.