Engine building questions: high compression , high compression turbo, e85..etc

[MiltonHavoc]

Sorry, late night error.
Milling, not gasket.

Thanks guys, you've answered my questions.
What i take from it is yes, it can be done.
However on a street car...and much less a mazda, its more beneficial to just turbo the engine given hp/dollar.

I still want to learn more about high compression. Maybe not for my car. But just in general ,i have an interest

[Movin]

Does short rods ( piston spends less time at TDC per revolution ) help prevent detonation more than long rods ( piston loiters in the TDC area longer per revolution ) ? It would seem if the RPM requirements stayed the same but compression was raised until detonation occurred it could be controlled initially many different ways, running out of ways as compression is raised will short rods with longer stroke or relocated wrist pin be effective at controlling the detonation caused by higher compression ?

[bhearts]

I'm not a B series expert but as far as I know the upper limits for compression on them is in the 11:1 area and that requires 93 octane and very careful timing maps to make good power. I personally would not want to build a motor that requires e85 due to its somewhat random availability. It also gets weird around this time of the year as every batch seems to be different mix do to the anti-icing additives that we get in the midwest. I've run E85 in my 2.3 turbo at various times over the last two years and it is fun to play with especially with turbo motors but you really need to have an ECU that you can tune (I use the mega/mircosquirt) and generally know what you're doing.

General when talking about compression in N/A engines you want to run as much as possible until the fuel becomes unstable. More compression makes the engine more efficient, more efficiency means more torque and more torque means more horsepower. The only problem is that the higher cylinder pressure and heat means more NOx. This matters if you're going to have to pass any type of emission testing as it's very easy to exceed the EPA limits just ask Volkswagen.

If you want to continue on the 1.6 build I would recommend that you pick up some ZM-DE heads to use. They bolt on the B6D blocks and have some significant port and combustion camber improvements. I would guess that one of these heads worked over with 11:1 compression and a good tune could make around 120 ft-lbs and 160 hp to the wheels. This would put you into the range of the average b6t swap and well ahead of a BP.

On the topic of nox emissions, cylinder temps can be greatly reduced by a form of water injection. Big water injection spray would not only allow you to run pump gas, but help the environment. The numbers are 25 percent water volume compared to gasoline is the rough maximum that the engine can ingest. So roughly 25 cc/min per cylinder on a b3. Considering the factory injector size is ~110cc min.

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[bhearts]

I wonder if carb testing checks for water levels in the exhaust. It should be fairly simple to hide a nozzle, water tank, and pump somewhere in the car. It's only cheating if your don't plan to inject year round.

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[Advancedynamix]

Does short rods ( piston spends less time at TDC per revolution ) help prevent detonation more than long rods ( piston loiters in the TDC area longer per revolution ) ? It would seem if the RPM requirements stayed the same but compression was raised until detonation occurred it could be controlled initially many different ways, running out of ways as compression is raised will short rods with longer stroke or relocated wrist pin be effective at controlling the detonation caused by higher compression ?

This can help on some engines. The mazda b series engines already have an unfavorable rod ratio though, so this could induce harmonic issues like what we see on BP engines.

[MiltonHavoc]

Bhearts, tell me more on this theory.
I dont have emissions where I'm at.
Why water injection vs ethonol?
And why not a device like a fuel injector but for water?
( just tossing stuff out there)

[blake4591]

Does short rods ( piston spends less time at TDC per revolution ) help prevent detonation more than long rods ( piston loiters in the TDC area longer per revolution ) ? It would seem if the RPM requirements stayed the same but compression was raised until detonation occurred it could be controlled initially many different ways, running out of ways as compression is raised will short rods with longer stroke or relocated wrist pin be effective at controlling the detonation caused by higher compression ?

This would help if the detonation was occurring late in the dwell time. If it was happening before the piston reaches TDC or at the beginning of the dwell reducing the total time would not help. Additionally as I understand it detonation in the end of the dwell period is unlikely since the flame front should have reached it's peak as the piston reached TDC and there should be little available fuel to detonate after that point. This is all theoretical though and I'm sure there are cases in the real world as Charlie mentioned were reduced dwell time would have an affect.

[jdobbs86]

Bhearts, tell me more on this theory.
I dont have emissions where I'm at.
Why water injection vs ethonol?
And why not a device like a fuel injector but for water?
( just tossing stuff out there)

Comment on using fuel injectors for water injection. I don't see why they couldn't work especially for something temporary. However since most injectors (internally) are made of steel they so they would probably fail due to rust. Some people do use fuel injectors for their home brew water injection systems with varying levels of success. Those who are more successful typically add something like Marvel's Magic Mystery oil to their water mix to help keep the injectors from seizing.

[bhearts]

Bhearts, tell me more on this theory.
I dont have emissions where I'm at.
Why water injection vs ethonol?
And why not a device like a fuel injector but for water?
( just tossing stuff out there)

With a high compression engine you get knock because cylinder temps are too high. Putting a higher quality fuel through like methanol prevents that, but it's not drastically changing your cylinder temps like alot of water could.

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[MiltonHavoc]

So a standalone "spray" system huh.
So roughly and basically:
Mount a water or other "cooler" tank in the engine compartment, wire in a small "fuel pump", have the injection system we stated previously in place?
Do I have the rough of it right? And that wpuld be dorectly injected into the cylinder?
I guess since water is free/cheap it makes sense to use. Ive seen marvins water wetter, but i hear people using windex in place of that...?