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Discussion Starter #1
So I was reading some threads a couple days ago, and all of a sudden I'm starting to make plans for this... Building for mpg is all new to me, so I have a lot of reading to do, but I was hoping to get some input in this thread in addition... So here's the deal:

I have a rt4wd wagon that currently has a jrsc on it, and I'm using it as a combined dd and weekend warrior on icey lakes during winter season. I know I wont get monster mileage with rt4wd and the wagon that is as aerodynamic as a brick, but I think it would have been a fun project anyway. I currently get 34mpg with the blower, which isnt bad, but I have a long way to work, so I would like to see some better numbers.

I have a d15z1 laying in the garage, and I also has a set of p28 pistons/rods. The d16a6 in the wagon burns a lot of oil, so I have to do new rings and a hone anyway. I was thinking about using the p28 pistons and the d15z1 head/IM/tb and exhaust manifold, mated to a peanut sized turbo such as a t25 or something out of a VAG. I will be picking up a used turbo locally, so I'll take what I find. But it will be something small that will put out 170-180whp max.

With the z1 head and z6 pistons I get around 11:1 static compression. The z1 is 9.2 stock. What I'm wondering is why the z1 has such low compression, does it have something to do with the lean burn? Is using a thicker head gasket to bring compression down a bit a good idea? The car will be ran at 95 oct RON during dd, and 98 oct when on the ice. That is equal to 90/93 oct in the us (I think, lol).

Has anyone tried to tune something with the z1 head? I'm really curious about the lean burn mode, and what it takes to make it work at 20'ish afr's during cruise.

Or is the z1 head just a stupid idea? I have a z6 head too, so I might as well be using that. But I have to say that the z1 head sounds more interesting. It would have been fun cruising at 20 afr :)

I know there are some people with a lot of knowledge here, so please share your thoughts :) I know about the search button, but I havent read everything on this forum yet, so sorry if everything has been asked before...
 

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IIRC, Z1 has 25cc combustion chambers. But the dish is pretty damn big on the piston.
16.1cc dish, 27.75 compression height, according to zeal.

Robster did a build very, very similar to what you want to do, but N/A.
D15z1 / D16z6 Combo rebuild - onecamonly.com

Z1 head has small, swirl inducing ports. Maybe a low-power, high port velocity, mpg beast?
I vaguely remember the Z1 switching to normal valve operation at 3000rpm. A small turbo should be spinning nicely at that RPM too.
 

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Boost Gets You Laid
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Can't help you too much except for stating the obvious that you'll prob take a small power loss for the sake of MPGs.
 

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Discussion Starter #4
IIRC, Z1 has 25cc combustion chambers. But the dish is pretty damn big on the piston.
16.1cc dish, 27.75 compression height, according to zeal.

Robster did a build very, very similar to what you want to do, but N/A.
D15z1 / D16z6 Combo rebuild - onecamonly.com

Z1 head has small, swirl inducing ports. Maybe a low-power, high port velocity, mpg beast?
I vaguely remember the Z1 switching to normal valve operation at 3000rpm. A small turbo should be spinning nicely at that RPM too.
Sweet, I havent seen that thread before. I'll read throught it now. Thanks! I'll rep you once I am allowed :)

Can't help you too much except for stating the obvious that you'll prob take a small power loss for the sake of MPGs.
Yeah, I wont be making tons of power, but I'm not too worried. I have had TONS of fun this winter only with a jrsc with a street tune @ 4-5 psi. I think a t25 @ 10-12 psi will make quite a bit more power, even with a z1 head.

:bigok:

 

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i have ran 3 d15z1 with z6 head turbo... they are fun little motors.. the last one i had i ran about 16psi on with a big turbo didnt fully spool till 2nd gear and i got about 40mpg if not more as long as i stayed out of boost... but i did run it kind of lean at part throttle
 

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If you want to get serious with the Z1, don't run the Z6 pistons. You loose a LOT of quench that way. The Z1 head works because of the quench and swirl in the chamber. I find it amusing that that kind of chamber is what it takes to do something Honda did in the original CCVC engines from 30+ years ago.
 

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Can't help you too much except for stating the obvious that you'll prob take a small power loss for the sake of MPGs.
Not necessarily. You can make power wide open and still get good mpg when not wide open.
 

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Discussion Starter #8
If you want to get serious with the Z1, don't run the Z6 pistons. You loose a LOT of quench that way. The Z1 head works because of the quench and swirl in the chamber. I find it amusing that that kind of chamber is what it takes to do something Honda did in the original CCVC engines from 30+ years ago.
Good info, didnt know about the quench area on the d15z1 pistons before now. Googled a picture and I see what you are talking about :) So if I wanted to use a d16 block I would have to use p07 pistons, d16 rods and then deck the block to get the quench back... Using the complete d15z1 motor sounds like a better (easier :p) easier option, then. It didnt burn any oil when I had it in my civic, so I think a good tune-up is all that it needs.

So I was just out in the garage taking a look at it and holy shit that IM and TB are small...! Has anyone ever dyno'ed a boosted car with a z1 head and IM before?

I was thinking about using a z6 IM and TB. Then I would have to dig out a bit on the intake ports to get a proper port match, so I guess that would screw up the airflow and kill all the benefits of using this head?
 

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Classic Man
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heres an idea...

use the turbo as a homoginizer... also as a check valve

use a water to air core with HOT coolant in it to heat the charge air more

box intake manifold in with steel to surround it with exhaust fumes, relocate sensors and IACV...

install stainless thick wall tube down the center of the exhaust, pre cat, and run fuel through it pre rail...



tune it


bet you pull over 65mpg.
 

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install stainless thick wall tube down the center of the exhaust, pre cat, and run fuel through it pre rail...



tune it


bet you pull over 65mpg.
I might be misunderstanding this part, but wouldnt this be a REALLY fast way vapor lock? Curious, just not sure if I understand what you mean...
 

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I wouldn't run fuel directly through something near the exhaust manifold. I would however, run a heat exchange system and do like Danz said and build a liquid/air heater.

Danz definitely has some good ideas and I know where they are coming from. =)
 

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Discussion Starter #17
Wow guys, I appreciate all the ideas, but I wont be taking it that far ;) It is supposed to work as a FUN car too, not sure how well all that stuff would be working during "race" mode. I've got most the answers I wanted, the d16/z1 combo is not a good idea because of the quench area, and it seems like it would be possible to tune for the z1's lean burn when I'm tuning it myself. At least the guy on onecamonly managed to run it at 20:1'ish afr. What I'm curious about now is what kind of numbers the tiiiiiiny d15z1 ports and IM produces in boost. Cant find any dyno's, so I guess I'll have to find out myself if go for it.
 

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Quench is almost always good.

Small Ports = Build for high velocity. You don't need a massive port because your not going for high-rpm/high-power. Small ports with a well designed turbo manifold will further help spool the turbo (high exhaust velocity).

With a W2A intercooler, you can simply shut off the pump/cooling circuit to get intake temps up if you wish. A simple electronic circuit can be wired up so that in lean-burn mode you have the intercooler in hot mode, but in all othercases in cool mode. Best of both worlds. A -small- W2A intercooler with good heat exchanger and pump is no more than $500 all bought from Frozen Boost. Not that bad, imo.
 

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Classic Man
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the closer to vaporizing the fuel is the better its gonna burn and the harder it will be to induce detonation...

you might end up with something that uses less fuel and hauls more ass...


smokey yunick to the rescue!
 
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