# Time for a new idea



## Murph (Aug 8, 2002)

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. Some responses from some of you NPM would also be appreciated.

Any comments welcome.


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## Chuck (Nov 19, 2003)

Murph said:


> 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.
> 
> ...



hmmm i see where you are going with this,it wouldnt give you anything to an added bonus, except gay turbo lag, and bad flow of exhaust... i mean, try it out, let us know, but i think it would suck


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## wes (Apr 30, 2002)

Benefit of this?


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## Murph (Aug 8, 2002)

benifit of this being boost and usagle of the ultra cheap T25 turbo without severe manifold backpressure.

what is "gay turbo lag"? Thanks for your constructive comments chuck. Bad flow of exhaust? Would you mind explaining that to me? You sound like a guy who knows his shit inside and out. I've only read a few book relating to forced induction applications. Maybe you could send me yours 

Anyhow, whatim getting at here is a relatively low-backpressure setup utlizing the T25 turbo. I would love either of the Mikes to comment on the long term detrimental effects on the engine harmonics from a setup like this. Any _constructive_ info is greatly appreciated.


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## TheVodKA (Sep 19, 2002)

It would take a really high amount of airflow to even spool a turbo like a t25 from 1.0L (2 cylinders.) They only spool so quick b/c of the 2 liters of displacement, so it'll luckily spool at 4k. Maybe it would work better with a Suzuki capuccino turbo (tiny, right?,) but you're not going to have much of a powergain. That, and you have to have an unnecessary amount of piping to both plumb the 2 cylinders and the turbine outlet to the same dp. Simply just not worth it IMHO, but if you want to be a trooper, be my guest.


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## Chuck (Nov 19, 2003)

lol, i was tired.. Gay turbo lag would consist of 2 cylandars trying to fill up a turbo that is ment to spool with a minimal 4... think about it like this.. if you have a T28 on a Sr20det, and it spools at... 2300.. taking away 2 cylandars, it wouldnt spool until probably double that... then your at 4600rpms.. i just dont quite see how it would be any more beneficial that hooking up all 4 cylandars..

IMHO, give it a try, and let us know.


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## Murph (Aug 8, 2002)

I apologize chuck if I sounded a bit irratable.

Thanks for the ideas everyone. In the next few weeks im going to be doing some number-crunching relating to the spoolup time (you all made some good points), however I still need some ideas regarding the structural integrity of the KA when putting each cylinder under a different stress level.


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## Chuck (Nov 19, 2003)

Murph said:


> I apologize chuck if I sounded a bit irratable.
> 
> Thanks for the ideas everyone. In the next few weeks im going to be doing some number-crunching relating to the spoolup time (you all made some good points), however I still need some ideas regarding the structural integrity of the KA when putting each cylinder under a different stress level.



much understood, i suspect i would be pissed at "gay turbo lag"..

as far as each clyinder under different stress... TECHNICALLY... each cylandar woudl accept as much air as the one next to it.. unless you have 4 direct ports of intake, and exhaust.. but if the intake manifold is still getting 1 intake, and 4 outputs.. technicaly each cylander will accept just as much air as the others.. just the exhaust part is what i would worry about if i were you.


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## scrub brush (Dec 31, 2002)

This concept has been tried before in CART. On big tracks, Toyota decided to run a single, large turbo on one bank, and open exhaust on the other. Apparently, they made slightly better peak power, but lag was so bad it only worked on the superspeedways.


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## FFgeon (Nov 28, 2002)

using exhaust ports 1+2 or 3+4 would be pairing the wrong ports together. if you are going to do it (i dont see teh benifit) pair 1+4 into turbo and 2+3 into downpipe. (or vise versa) why not just get a manifold and throw a t25 on there and run it on all 4 cylinders. more power sooner. get a jim wolf computer, some sr20 injectors (370cc i belive, hell, ill even sell you mine when i get my turbo) a clutch and a 300ztt fuel pump. then your good to go. :fluffy:


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## Murph (Aug 8, 2002)

FFgeon your right with the 1&4 or 2&3. I sat here and thought about it for 10 mins and I think your right.

Putting a manifold on and running a straight T25 is a terrible setup. Its a terrible setup because of the immense turbo manifold backpressure which will rob you of power severly because of the tiny turbine that cannot handle all the air. I talked to someone on another forum who did this running 4-5psi and he only gained 25whp. Not the way to go. I need lower backpressure numbers in order to make the most of the available boost. 180whp would be nice.

PS. fuel pump and fuel filter would be plenty to run 4psi just fine.


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## go4broke44 (Jan 14, 2003)

i thought pistons 1 & 4 fired at the same time? or at least they both have the same up and down stroke, they could fire alternatively i guess too... i think a T-25 would be too big to use for just 2 cylinders, you might be better off with a TD-05, or something smaller. doesnt sound like too bad of an idea though, and you wouldnt lose a whole lot of low end power, since you still have 2 cylinders running through, unrestricted, as far as exhaust flow is concerned. i guess the only way you would really know is to test it out


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## FFgeon (Nov 28, 2002)

4-5 psi isnt going to do much. run on 12 lbs. that will wake up your lil 1.6 trust me, run all 4 cyl into turbo.


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