Z24 Super Sniper 2300 and turbo build plans/questions.

[SharksTit]

I am a long time reader, but never posted or registered. Here is what I've done so far and my plans for the build.

 

I've had my 720 for about 6 months now. Bought for for $500. Odometer reads 187k but it stopped working. Was taken care of maintenance wise. It leaks a quart about every 1k miles.

 

I wanted to start a turbo build but didn't want the headache of a blowthru carb. I made an adaptor for my Super sniper and it fits nice, but not installed. I'm leaving the truck factory untill I have everything ready.

 

I have all the parts fuel wise, but want to hear comments relating to the turbo portion on some things i should do first, as well as, ask a few questions.

 

My plan is to aquire a turbo manifold for a ka24 and grind out the ports a bit to match the z24. I'm guessing a cheap Chinese turbo will suffice for 10-14lbs of boost. I'm looking to make around 200hp to start. Cheap intercooler along with the intake plumbing isn't an issue.

 

My questions are:

1. What is a good AFR to start out with when i start tuning?

2. What are some preventive measures i can take to avoid a blown head gasket or a hole in the block? (New head gasket will be installed prior to first start)

3. Head. Should I worry about porting the head or swapping one from a different engine? If so, what heads would fit?

4. Timing. I'm new to playing with turbo installs. Should I worry about adjusting the timing? 

 

Any input not related to the questions would be appreciated.

[datzenmike]

I believe the KA exhaust will almost fit the Z series and can be made to.

 

 

HEAT is the most destructive thing to worry about on a boosted engine. Everything you do should be centered around managing the temperature of the air entering the combustion chamber. Twice the HP is going to make twice the heat so maybe a better rad. Oil cooler to remove oil heated by the turbo. Probably a synthetic oil. You can also have a separate water alcohol injection under boost. Water and alcohol will absorb heat and turn to steam. This is called charge cooling. Intake air should be collected from in front of the rad. Warm air is bad.

 

The Z24 makes about 100 hp at one bar so in theory you will need two bar of boost to double it.  Not impossible but the stock hypereutectic pistons are reliable to 0.5 bar but held above that for any time isn't good. I would definitely get some kind of engine management set up that tailors the ignition timing to the boost (question one) and dove tails with the EFI to run richer during boost. This should save the pistons although forged would be a good idea.

 

 

Perfect a/f is 14.7 to 1. This is theoretical perfect burning of all oxygen and fuel. The a/f graph is a bell curve with a broad curve at the top and 13.7 rich to 15.7 lean doesn't really affect mileage or power too much. Best mileage is just above 14.7 to 1 where there is more oxygen than needed but it assures that all the fuel is burned. When you get too lean, the mixture is harder to ignite and lean under load can cause hot spots to form because there is less available fuel to absorb heat and cool the combustion chamber, piston and valves. Too lean under load is a bad thing with a turbo it 100x worse. For full throttle, a richer mixture of 12.5 to low 13s is better. The excess fuel that isn't burned helps absorb heat by evaporation and reduces pinging. If you have EFI this can probably be dialed in on a lap top taking boost pressures into account as well.

 

ARP head studs are almost a given as the Z24 seems to loose it's clamping pressure on the head gaskets and blows them.

 

KA24E high volume oil pump in conjunction with an oil cooler.

 

There is nothing you can do about the Z24 head. Normally aspirated it has flow limitations that don't help it make as much power above 4k as it could. It wasn't designed for power but for low emissions and low end torque. HOWEVER... it does have a very efficient hemi combustion chamber, dual spark plugs that reduce the burn time and ignition timing and it is a cross flow head, so the intake ports are not baked by the hot exhaust ports right beside them. All good things for a turbo engine.

 

Ignition timing is covered under engine management above.

 

 

 

 

 

[SharksTit]

7 hours ago, datzenmike said:

 Ignition timing is covered under engine management above.

 

 

 

 

 

The super sniper is the engine management when set up with the proper parts. It has it's place for ignition timing control as well. I wasn't sure what could be done. The twin spark stumped me on that. I wanted to get an msd ignition coil but wasn't sure if I needed 2 to mimic the existing 2 ignition coils. 

[datzenmike]

Forget MSD they are over hyped and last I heard the quality is getting poor. Stick with the Nissan EI (electronic ignition) ignition module and coils.