I am looking for information on HG thickness and how much more boost, (and up to what point) is safe on a stock VVTi block with just the thicker gasket and ARP head studs. Can this engine handle say 16psi? 20? Say I did a GTE head gasket, or a custom one whatever. My build as a whole is good for 450-500hp with the addition of another pump and the turbo good for 25psi (it claims). Wondering what I can get out of this after strengthening the transmission etc. If anyone knows the limits of the pistons/rods.

I joined Supra forums to ask some of the questions I've been asking in their NA-T section, but it seems like the forum is all but dead. No responses and no recent posts there in general by other users.

 

https://www.suprastore.com/n2thhegafor2.html According to this, a 2.5mm head-gasket brings compression down to 9:1 on a vvti engine. How can I use this figure to judge a safe psi?

 

I think your concern is torque and the relatively bendy nature of the GE vvti rods. The GE vvti rods are not near as strong as the non-vvti from what I've read. Here's a thread for some consideration. https://www.supraforums.com/threads/...i-rods.743746/

 

Unfortunately Facebook seems to have killed forums in general and it makes it impossible to find good information on things anymore.

I think the answer to your question is it depends on your personal desired safety level as well as your exact engine. Some engines just naturally make more power than others. I know that you said its dead but there are a fair number of older threads on the Supra forums as well as SC and IS forums on here about NA-T. I know that may not get you an exact answer but I don't think there is a universal answer that will apply. Every setup is different and obviously if you lower your compression you can add more boost and make more power. From everything that I've read over the years since buying my car, there are people running 8 psi and people running 22+ psi on the same setup. I think if you go to above 15 psi you'll be getting into the danger zone. At 8 psi you know you'll be safe and if it were my car, I would start getting a tuner involved once I was over 12 psi. They should be able to tell what is safe and where you're pushing things too hard for your particular setup and engine.

Like KyleH said the rods are going to be the weak point of the engine followed by the pistons if you upgrade the rods. Also keep in mind the GTE also has oil squirters to help with cooling at higher boost levels.

 

Thanks guys, that link KyleH posted actually answered it in the first few posts. The IS300 guys are seeing 450whp with a head gasket and ARP studs. Liking to go a little less than the limit people push to for longevity, I'd run low 400-420whp. Being that I'm going to be around 300-320whp with my current setup, Id say after my transmission strengthening upgrades, the price of a 2.5mm head gasket and some studs is well worth a weekend project to pull the head and then up the boost through my same setup by another 100 ponies!

 

I didn't say it in my last post but I love your build and all of the heart that you're putting into it. Keep up the good work!

 

Thanks man! I'm actually dyno tuning the car today, so we'll see how all this time and effort pays off. Only shooting for the 300whp range to keep it all safe. All these questions I've been asking around the forum are for the next phases being planned. It's going to go transmission next, then rear end. Then the head gasket/ARP studs as a project just to maximize my current setup. Put me over 400whp. Then eventually a GTE block or GTE internals maybe and a bigger turbo/injectors/pump and go for 600+. Thats all a long time off though.