[Jaggu]

Hi all!

I have a 2zz Spyder that needs a headgasket replacement and I intend to go turbo before the summer.
Heres my thinking and I would like someone to correct me if I am wrong.

Cause the high compression ratio on the 2zz stock is 11.5:1 it cannot take much more than 8psi.
So to gain more power (into the 300s) reliably i've read you need to drop compression ratio.
So what I thought I needed to do was get myself mahle forged pistons 10.5:1 as it's in the range from 5-15 psi that i am looking for.
However I saw that cometic has a headgasket that is 1.3mm thick (stock is 0.5mm) and drops compression by one full point (from 11.5:1 to 10.5:1) according to MWR. Which is significantly cheaper and does exactly the same as forged pistons.

Link to both items:
Cometic head gasket – Toyota 2ZZ-GE 82.0-82.5mm 0.052″ (1.3mm) | Monkeywrench Racing
Mahle Piston Set – Toyota 2zz – 10.5:1 compression 82mm | Monkeywrench Racing


Am I being dumb or will this actually work?

 

[Funkycheeze]

Forged pistons are stronger and will make the engine more knock resistant. Plus just a thicker head gasket makes the quench area (cylinder volume with the piston at the top) a very non ideal shape. Go with the pistons. Might want to go down to 9.5 or 10:1 depending on what fuel you plan to use.

 

[Jaggu]

Forged pistons are stronger and will make the engine more knock resistant. Plus just a thicker head gasket makes the quench area (cylinder volume with the piston at the top) a very non ideal shape. Go with the pistons. Might want to go down to 9.5 or 10:1 depending on what fuel you plan to use.

It's either 10.5 or 8.8. I don't plan on running too high boost as I would like the engine and transmission not to die on me right away. 15psi was okay on 10.5:1 compression ratio and that would give me more than I trust the engine to cope with.

Might start with 7 or 8 psi and upgrade later but if cheaping out on gasket will cost me later I guess it's not so worth it.

 

[Funkycheeze]

Can always order custom pistons with a spec compression ratio. Just a little more $

 

[MerryFrankster]

Run Ethanol. Problem solved. You don't even have to open your engine.

 

[Node]

Run Ethanol. Problem solved. You don't even have to open your engine.

Run METHANOL and problem solved. The compression ratio is NOT the issue with the engine. The weak ring lands are. This makes the pistons sensitive to any knock so tuning is difficult. Case and point my build is currently stock block running air to air plus methanol injection. The engine has been boosted for years and years. The street setting is 13 PSI (used daily) and track setting is currently 20 PSI. I think the key to it's long life has been progressive methanol injection. Fully 3D mapped just like the fuel injection. This allows for the effective octane to be varied as needed, keeps carbon out of the pistons and washes PCV oil away.

Thinking that you need much more than that in a car this light is a bit silly. The transmission just wont take it. Many Lotus owners destroy the transmission right at about 350 HP. My transmission is seeing over that and the differential is no longer healthy. I expect I will be shopping for a spare soon.

The point is, properly tuned you don't need to lower the CR. The car will be insanely quick around 10-14 PSI. Like on par with supercars in the 700hp range. So, my advice is build for mid 300's and enjoy some reliability. Everything starts to need rework as you approach 400 hp and at 500 hp none of the driveline can be stock at all. I'm talking transmission, axles, tie rods, return style fuel system, electronic throttle for traction, etc... Cubic dollars there.

 

[k_swap_it]

If you need to replace the head gasket anyway, just go with the thicker one and drop the compression. You won't miss the extra point of compression and you'll have more headroom to tune it after the turbo install. This isn't a racecar so no reason to run it on the ragged edge unless you're prepared to deal with the consequences.

 

[Jaggu]

If you need to replace the head gasket anyway, just go with the thicker one and drop the compression. You won't miss the extra point of compression and you'll have more headroom to tune it after the turbo install. This isn't a racecar so no reason to run it on the ragged edge unless you're prepared to deal with the consequences.

Will the lack of compression reduce horsepower by a large margin?

 

[k_swap_it]

Will the lack of compression reduce horsepower by a large margin?

You'll lose around 5hp from the drop in compression. Which will of course be negated when you boost the motor.

 

[Funnyman]

Engine rebuild + turbo + pipping + standalone choice + gauges electronics + custon exhaust + brake-in engine + dyno tune.
Doing a complete engine rebuild turbo for 300hp ready for the summer (in 3 months) is very/too short. I didn't include shipping delay.
As you seem to want a reliable tune, there is not many choice. In all case, the C64 trans will take a hit.

 

[SafetyNate]

Meth and 30 psi, its an addiction thing...
if your going forged pistons just go full forged internals and balance the rotating assembly.
10:1 compression & 20 psi you'll have a perma grin... boost is addicting dont under build the engine tho

 

[evilthorne]

Node is right the ringlands are the weak point of the 2zz, crank and rods are stout to 400hp. But the same thing that prevents our motor burning oil is the same thing that signs its death warrant for boost. Meth injection may cool the pistons enough to run up to 300hp. Maybe

 

[Node]

Node is right the ringlands are the weak point of the 2zz, crank and rods are stout to 400hp. But the same thing that prevents our motor burning oil is the same thing that signs its death warrant for boost. Meth injection may cool the pistons enough to run up to 300hp. Maybe

You're not wrong. I run timing on the VERY conservative side and stay well away from any knock. I probably leave 30 HP on the table just to protect the engine.

300 hp is way on the low side of what the unopened 2ZZ engine can do. 300 crank is only like 8 PSI on most builds and maybe even less. You can do that without an intercooler! Heck, you can even manage that supercharged with no intercooler (see Lotus TVS builds). I have done that with my 71mm turbo even without active knock control from the ECU.

 

[Jaggu]

Meth and 30 psi, its an addiction thing...
if your going forged pistons just go full forged internals and balance the rotating assembly.
10:1 compression & 20 psi you'll have a perma grin... boost is addicting dont under build the engine tho

Don't have a very large budget but I wont take shortcuts. I am only looking for low boost as it is cheaper than having to install new pistons and such. Got about 5000$ set aside for everything including dyno day.

 

[evilthorne]

You're not wrong. I run timing on the VERY conservative side and stay well away from any knock. I probably leave 30 HP on the table just to protect the engine.

300 hp is way on the low side of what the unopened 2ZZ engine can do. 300 crank is only like 8 PSI on most builds and maybe even less. You can do that without an intercooler! Heck, you can even manage that supercharged with no intercooler (see Lotus TVS builds). I have done that with my 71mm turbo even without active knock control from the ECU.

over 300hp on a blower car with stock engine is dangerous because it takes power to make power with a supercharger. 300 would be 330hp ish in the end. Even though you are only making the soft imposed limit of 275whp you would be making over 300whp technically.

Trust me though, with 220whp my supercharged 2zz is fun and very fast. I fear very few cars. Most think it is an underpowered miata.

 

[Node]

220whp my supercharged 2zz is fun and very fast.

That is exactly my point. In the era of 1000 HP street cars that weigh 4000 LBS not many people really understand just how quick a 2000 lb car is with over 200 hp and short gears. If you can keep the tires from spinning not much can compare at under 70 MPH.

 

[Funkycheeze]

It's true. My Cayman has 350 HP (known for being close to that at the wheels) and weighs just over 3000 lb and is very quick. My Supra is just under 3000 lb and 475 wheel (in the higher gears) and is frightening. Even my cammed non FI 2ZZ MR2 is quick.

 

[dblotii]

You're not wrong. I run timing on the VERY conservative side and stay well away from any knock. I probably leave 30 HP on the table just to protect the engine.

300 hp is way on the low side of what the unopened 2ZZ engine can do. 300 crank is only like 8 PSI on most builds and maybe even less. You can do that without an intercooler! Heck, you can even manage that supercharged with no intercooler (see Lotus TVS builds). I have done that with my 71mm turbo even without active knock control from the ECU.

On the other hand, the more you retard the spark the hotter the exhaust gets, unless you go richer in fuel/air.

 

[Funkycheeze]

You get in a bit of a corner between knock, spark retard, and too rich. Only way out if you want more power is better fuel, lower CR, more inter cooling or water/meth (which cools the intake and improves the fuel quality)

 

[Node]

On the other hand, the more you retard the spark the hotter the exhaust gets, unless you go richer in fuel/air.

That's not exactly the case. I can make no more power at 10.5:1 than 11.5:1 with more timing in most of the map.

I go back to my point I was making earlier though. A 500HP 2ZZ does not make a whole lot of sense if you are running a C-series transaxle. Seriously, look at what the power to weight would be (if the transaxle didn't explode). That is an insane car. Trust me. IMO it is not worth building the 2ZZ for that kind of power.

Power/Weight LBS
Cayman GTS 4.0 = 0.123
FAT Spyder 2200lbs @ 500 HP = 0.23
Huracan = 0.188