turbo low compression hp

[NvIs]

hass & C2 turbo kits have great numbers in results with the 2zz motor. seeing numbers like 250 270 hp at 7psi assuming this is still with stock inturnals, but is this really safe. Now i have searched the forum and found that its supposedly safe if boosting on 6-8 psi on stock internals, but if you look at other turbo cars like eclipse gsx, supra, rx-7, or the evo which are some of the best jdm cars ever made they have a compression of 8.0:1 to 8.5:1 at the highest. my question is that how much hp would the 2zz motor make with low compression pistons? and if running on 7psi is reliable would putting in low compression pistons make it that much more relaible for dail driving? thank u

[Smaay]

there are a few celicas here making over 300HP with low compression pistons. Im running the MWR Stroker motor with 8.8:1 compression pistons. I havent had a chance to get on a dyno yet to see what im making, bu im sure im in the 300 range at 14psi

[NvIs]

damn kill my hopes jk. 14 psi should be safe considering the low compresion kit, but compared to other cars like the eclipse gst/gsx the car makes considerably good gains at 14 psi (my freind has one and run mid low 13s)and 210 horse power stock at 6-8psi not sure exact stock psi. But is the celica pushing over 210 horse power at 6-8 psi with the low compression pistons?

[NvIs]

oh and by the way smaay i posted in the southern california page on a good shop to tune a 2zz c2 kit in the riverside area and boosted 2.0 told me you would know. thanks!

[Black_TRD]

damn kill my hopes jk. 14 psi should be safe considering the low compresion kit, but compared to other cars like the eclipse gst/gsx the car makes considerably good gains at 14 psi (my freind has one and run mid low 13s)and 210 horse power stock at 6-8psi not sure exact stock psi. But is the celica pushing over 210 horse power at 6-8 psi with the low compression pistons?

those 210 stock on the eclipse are to the flywheel you can get that to the wheels and more on the celica at 6-8 psi :eatpop:

[Boosted2.0]

oh and by the way smaay i posted in the southern california page on a good shop to tune a 2zz c2 kit in the riverside area and boosted 2.0 told me you would know. thanks!

Actually I meant you could take your car to Smaay.

Those motors you are comparing to are 2.0 Liters plus of displacement. Thats not apples to apples.

PSI is also relative. It represents boost working agains the restriction of the intake, head, valves, etc. Depending on cams, exhaust manifold, turbo, downpipe, midpipe, muffler, IC and intake the power level at a given PSI at a given RPM can change significantly. For instance: My alltrac made MORE power at 10 PSI with HKS 264 cams then it did at 12 PSI on stock cams. The reason being the engine breathes much better with the bigger cams and hence makes more power with less restriction.

Lower compression lets you run higher boost without detonation. However if you can make your power goal at stock compression then you will simply loose power by lowering compression

[NvIs]

so in ur guys opinion would u say buying an N/A car and going thru all the trouble buying low comp. pistons, rods, afc, tuning, and turbo kit would be better in top end horse power than a car that would come turbo?
since N/A converted to turbo makes more horsepower at the same psi and lower displacment than an eclipse or str-4's.

[JayHass]

Are talking about 1z or 2z?

For the 1Z, I tell my customers that max boost is 9-10psi I recommend for trouble free running. However, I will add that I have lots of customers out there running 12-13psi on a daily basis, and some pushing past 15psi - even under road race conditions. I just stress that if you plan on turning the boost up past 10psi on your 1Z, understand and don't freak out if you do have some issues pop up. I personally am running 15-16psi in my MRS but I'm also fully aware that I may push a rod through the block but to date the motor is trouble free. Keep in mind, I've also spent a fair amount of time refining the tune to get there.

For the 2Z, weather conditions play a larger roll in this with the very high compression. We went through great lengths in our kit to be sure we addressed the detonation issue with a large safety margin through the Aquamist 1S water injection system we include.

To date, we have made 327whp with the 2Z at about 11.5psi on a 40+K engine that was driven pretty hard. 6-7 months later the car is still going strong but at this point the owner is going sick with a 2.0 stroker, solid deck with wet sleeves etc etc and we are going to push it to insane levels.

I personally have been up to 15-16psi on the 2ZZGE with pump gas and a 1mm water jet. This was in cool weather but the car was shockingly okay with it.

Please keep in mind I am speaking from the experiences I have had with our kits. I can't speak for custom set ups or other systems

As for low compression and power output, what you should calculate is net cylinder pressure.

Having said that, do a dynamic compression calculation at 9psi and see what you come up with at 11.5:1 static vs 8.5:1 static. The difference is huge. Almost 17:1 for the 11.5 engine vs 11:1 for the 8.5 engine...it's pretty much like running about 19psi on an 8.5:1 engine just from a dynamic compression point of view.

You lower the VE of the engine with lower compression which is why it takes more boost to get the same power output...but are also able to run more boost in the first place. Over the years, I've become more of a high compression, lower boost fan as it give a more linear power curve as you are not relying on mega boost for the power output. VW has started to march to that drumbeat as well with thier factory high compression turbo engines.

Hope that helps explain things a little better.

[timm3r]

so your saying that running on low boost with stock internals on a 2zz is better than actually getting some low compression pistons and running at more boost? or are you just saying the advantages are better? what if you get some higher compression pistons such as the trd 13:1 pistons and run at even lower boost?

[Smaay]

you're talking chances of breaking things with higher copmression....think of it this way, boost is like compression, the more boost, its like raising the compression...its increasing the amount of air and fuel in the cyllender

[JayHass]

so your saying that running on low boost with stock internals on a 2zz is better than actually getting some low compression pistons and running at more boost? or are you just saying the advantages are better? what if you get some higher compression pistons such as the trd 13:1 pistons and run at even lower boost?


It depends on what you want. If you want a 275whp car that acts much like an NA car's powerband only "more" of it, a low boost high compression situation may be something to look at.

If you want to make 400hp, lower compression and turn up the boost because in a street car you will be hard pressed to get there with 11.5:1.

If we were running methanol or C16 all the time, I might say go for big boost on the 11.5:1 but I can't afford $7 per gallon gas. :D

On the 2ZZ I'm very curious to see how a mild drop would react like a 10:1 set up or so. I mean, that's still a point and a half drop from stock...

[02VaderCelica]

correct me if im wrong, but doesnt the thickness of the head gasket also change the compression, so a thicker one would do what? is the C2 headgasket thicker than stock?

[Hetts]

motors with higher compression are going to make a lot more heat, which is the reason you would need methanol or race gas if you wanted to push a lot of boost on a high compression motor (to help prevent detonation)

The biggest factor that comes into play whenever you want to run high boost with high compression is TUNING. Jay said he was running 15 lbs, but he is a VERY experienced tuner, and would be able to make corrections for everything. when boost is that high on a stock engine, everything becomes a factor... altitude, temperature, etc etc...

[JayHass]

correct me if im wrong, but doesnt the thickness of the head gasket also change the compression, so a thicker one would do what? is the C2 headgasket thicker than stock?

Lowering compression via head gasket thickness has always been IMHO a ghetto way to do it for serveral reasons.

There is a relationship between the quench areas of the head and the piston tops. By moving the head higher off the deck, you screw with that relationship and directly affect the engines ability to fight detonation. So the net effect can actually be the same in regards to detonation control.

You also mess with the cam timing and unless you have adjustable cam gears will always be a few degrees off.

You also make a larger area to blow out if you have troubles. Thicker head gaskets fail easier than thin gaskets. Gaskets are a band aid to deal with production tollerances. No gasket is best. Porsche uses no head gasket. They machine the surfaces properly so there is no need. In a large production environment like Toyota deals with that kind of tollerance would makes the cars too expensive.

We do the same thing with our turbo kits regarding gaskets. We machine all flange surfaces dead flat so you need no gaskets for the turbo and downpipe and that gives you one less item to fail or blow out.

[JayHass]

when boost is that high on a stock engine, everything becomes a factor... altitude, temperature, etc etc...

It sure does which is why I don't say it *can't* be done but unless you have an experienced tuner and/or now your car well don't push it past 9-10psi.

There were a lot of tuning issues I had to overcome to get a 1Z to live past 300whp. One of them was calculating where peak cylinder pressure takes place and tuning to optimize that. The 1Z has a pretty harsh rod angle and too much cylinder pressure was putting load on the rod while it was on an angle like this / during it's travel and shearing the wrist pins off the piston and the engines were failing. By fine tuning the ignition timing map and calculating flame travel and where peak cylinder pressures took place I was able to turn the boost up a lot higher and get the connecting rod more verticle before it was loaded down. This has so far let the 1Z live under more boost and power then was ever thought. 325-340whp on a stock 1Z for any amount of time impressed the hell out of me considering what the internals of this engine looks like. It's certainly a lot stronger than I orginally though it was. It's no Honda D16, that's for sure. :D