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]

Originally Posted by 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.

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

Sorry -- couldn't resist...

RH77

[GasSavers_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]

Originally Posted by 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.

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.

[GasSavers_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]

Originally Posted by 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?

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