high compression thought?

[chromejunks]

has anyone thought about raising their compression 12.0:1 or maybe higher. i have built many of b-16 and b-18 honda engines that are around 12-12.5:1 for guys to run on the street. a little to high for pump fuel in my opinion if you don't have a way to tune. they have all told me that they got better mileage on the highway at part throttle. i have been wondering that at part throttle you are not filling you cylinder with the max amount of air so the efficency of the engine drops and i was thinking that the higher compression makes the cylinder burn more effiecent. note that under hard acceleration you could ping. maybe if you tie in the water injection with the high compression to help cool the cylinder temps down to keep from detonating. hmm may have to try this.. bye the way the insight engine is a 12:1 lean burn if i'm not mistakin.


the only down fall to this is that you would have to run 92+ octane which means a little higher price.

[SVOboy]

DrDisco: 12.5 is not a problem on 93 octane
DrDisco: and more compression = more efficient
Me: Any idea how much more? Such as being worth going up to 93 octane?
DrDisco: i think it's a few percent per point, i'd have to look it up
Me: How does one go about doing this? Increasing the CR I mean.
DrDisco: thinner head gasket, mill the head, high compression pistons, high compression valves, weld the combustion chamber, longer stroke, ummm
DrDisco: ok, found my chart on compression ratios
DrDisco: so from 9:1 to 12:1, you will gain approximately 7.7% more power
Me: Aha.
DrDisco: 13:1 would be 9.7% more
DrDisco: the prius runs some rediculous ratio like 14:1 or some ****
Me: That's awesome!
DrDisco: but that motor is very different
DrDisco: it's an atkinson cycle engine, not an otto cycle

Seems like something I'd like to try also. I'd prolly mix toulene though. I know Matt had the issue of doing just a head swap cuz it would be something like 13:1 CR, but hell, right now that seems like a benefit to me...:-)

[Matt Timion]

SVO Boy is right. I had an issue with a project I had planned. I was planning on putting a d15z1 head on a d15b2 block (all honda parts for the non-honda people). The d15z1 head has a very small combustion chamber and is built for efficiency. The pistons that come with the stock d15z1 are VERY domed to compensate.

When you put the z1 head on the b2 block (b2 block has flat pistons) the new compression ratio is something around 12.3:1. It was ridiculously high for the application I am building for (economy). I can see, however, using this setup for a drag car.

I have actually getting another civic and throwing the z1 head (i have a spare one if you want it) on the b2 block to see if there would be a difference.

Then there is the issue of the weird vtec-e that the z1 uses and I'm not totally sure it would work properly with the wrong pistons in there.

Anyway, if you are interested in a d15z1 head I can send it to you for cost ("cost" being what I paid for it, which is dirt cheap).

[SVOboy]

I'm going to wait on bense, who's doing this with a y5 head instead of a z1 head, hoping his stuff works out fine, then I'll go for the z1 head if it does. But it seems like 8% is a pretty good improvement over the z1 that'd be getting mid to high 50s in our cars stock.

[Matt Timion]

one more tidbit for this thread. I will have a d15z1 head, cylinder cover and intake manifold soon. The intake manifold will be missing the TPS sensor, but it has everything else.

You can use your existing TPS sensor or one from a junk yard car.

You will also need a obd1 distributor (I have an extra, but I'm keeping that) and the p07 ECU along with a conversion harness.

If anyone is interesting in buying what I have let me know. It will just be collecting dust until someone buys it.

Over all the entire swap will run around $130 if you make your own conversion harness. If you can really get 10-20% more power with the added HP it will be worth it.

Heck, i might even try it if I ever get a spare hatchback or something.

[rh77]

one more tidbit for this thread. I will have a d15z1 head, cylinder cover and intake manifold soon. The intake manifold will be missing the TPS sensor, but it has everything else.

You can use your existing TPS sensor or one from a junk yard car.

You will also need a obd1 distributor (I have an extra, but I'm keeping that) and the p07 ECU along with a conversion harness.

If anyone is interesting in buying what I have let me know. It will just be collecting dust until someone buys it.

Over all the entire swap will run around $130 if you make your own conversion harness. If you can really get 10-20% more power with the added HP it will be worth it.

Heck, i might even try it if I ever get a spare hatchback or something.

Yeah, Ummm, Okay. I didn't get the cover sheet on those TPS reports.

Sorry -- couldn't resist...

RH77

[DaX]

I might be interested in getting the Z1 intake manifold from you for my MPFI conversion on my D15B2. I have a P07 ECU if anyone is interested...only thing I have done is practice desoldering where the ROM goes.

[Matt Timion]

I might be interested in getting the Z1 intake manifold from you for my MPFI conversion on my D15B2. I have a P07 ECU if anyone is interested...only thing I have done is practice desoldering where the ROM goes.

I've been waiting onthis guy to send me the intake manifold for over 2 months now. I was originally going to do a z1 mini-me on my b2 block but due to the compression problem I decided against it. I instead bought a JDM d15b vtec-e engine for $350 (plus $200 shipping from CA, ARGH).

So I've been waiting for this intake manifold forever and some day soon *crosses fingers* I'll be able to get it. I may be able to sell it to you at that point.

Don't forget that the z1 throttle body is MUCH smaller than the other ones. It's the same size as the HF intake/TB which would require you to get a different air intake hose/airbox top.

[DaX]

That's fine. I think I still have my VX intake box top somewhere, and if not, fabbing my own would be no problem. Does the IM still have the TB on it?

[Matt Timion]

That's fine. I think I still have my VX intake box top somewhere, and if not, fabbing my own would be no problem. Does the IM still have the TB on it?

According to the guy who has yet to sent it to me, yes.

[SVOboy]

Oh snap, go for it Dax! And while you've got it all apart, drill into your TB for some water injection, ;-), that'll really extend the leanness of the z1, I believe.

[SVOboy]

<a href=http://www.mtggraphics.com/bigmoosepapers/ThermodynamicCycles2.pdf target=_blank>Argument Settled</a>

I'm going high compression, more power, better fuel economy, woot.

[Matt Timion]

As I mentioned, if any one else is interested in doing this same thing (on a honda d-series engine) I have a d15z1 cylinder head (with vtec solenoid) for sale. I also have the valve cover for a little extra. This with a obd1 distributor and p07 ECU (along with a conversion harness which I'll soon be posting the pinouts for) you'll be ready to rock.

[DaX]

Matt, I'd be willing to buy the head and do the swap, but what about all the peripherials that the P07 is going to be looking for? I know there was at least one little 'black box' in my VX engine bay, and you're going to have to wire up a 5-wire o2 sensor. I have a pretty good writeup on converting a 5-wire harness to a 4-wire harness on Honda-Tech - maybe you could use it in reverse or something.

[Matt Timion]

Matt, I'd be willing to buy the head and do the swap, but what about all the peripherials that the P07 is going to be looking for? I know there was at least one little 'black box' in my VX engine bay, and you're going to have to wire up a 5-wire o2 sensor. I have a pretty good writeup on converting a 5-wire harness to a 4-wire harness on Honda-Tech - maybe you could use it in reverse or something.

The black box is the EGR control box. I've been told that the EGR control box from a HF works as well. I can check the junkyard to see if the VX is still there and swipe the extra egr control box if you want it.

As for the o2 sensor, I already have a five wire o2 sensor that I am going to us for my swap. I am planning on just running the wires from the ECU straight to the o2 sensor. In a perfect world I would have found a vx wiring harness, but I never get that lucky. I'm still in the process of making my vx conversion harness which I finally have all of the pinouts for. I should be done sometime very soon.

So, IOW, if you want the head I can sell it. I'm not certain what a good amount to ask is, but I guess that is up for negotiation. I also have a set of obd1 injectors and fuel rail. The guy who was going to sell me the VX intake manifold screwed me, so I can't sell you one of those. ANy HF or VX manifold will work though.

Anyway, i'm rambling. Send me a PM if you're interested.