I agree PSI is completely irrelevant. The correct question is how much power can the block handle and I'd say from the people already running 500 WHP+ with no issues, you should be just fine with your plans. By the way, defintely get a Red if you want to make serious power with a bolt on turbo. Blouch doesn't offer anything that big at all and I've had problems with them.

 

One thing that is being left out is longevity, which I don't think has been tested in depth. Sure, people can/are running 500whp - but can this be kept up for 10k, 50k, or 100k miles? Maybe, maybe not - only time will tell. I'm guessing the OP is like most of us who wants their dd to be a ton-o-fun on the commute to work and that needs to last for at least several years.

Regardless, it is good to hear that the initial results of the 4B11 are impressive. Before the X came out many, many people were bashing its potential.

 

Wrong. AMS said that initially they were going to drop in a built block with upgraded internals, but didn't have time so they left the stock long block in place with all factory internals. The magazine article confirms this, would you like me to scan it and post it up for you to see for yourself? AMS decided to use this as an opportunity to test the stock block and internals and were very impressed with the results. They have a thread somewhere in the X general section disclosing all of this info if you don't feel like reading the magazine article. Do more research next time before making blatently incorrect statements like that; there's enough misinformation on this forum as is.

 

I'm just going to throw out there 26.7 lbs on the stock turbo, and up to 50lbs with supporting mods
I'm surprised there isnt a "FP Red now AVAILABLE for Evo X" yet.....or is there

 

You are correct sir

Our white EVO X that competed in USCC had a completely STOCK motor, that never left the engine bay.

 

Well you are correct, the December issue did indicate the switch. That said, in the Set up issue in November for the Street Car challenge, the mag indicated that AMS' engine had the Ross pistons which is what I recalled. Guess I got lost between issues.

Later, Ken

 

No biggie.

 

If you know what seat pressure you are trying to achieve at installed height, you basically take that and add your desired boost pressure and that is the actual seat pressure you want to see at installed height. For example, if you would like to achieve 60 lbs on the seat, and you want to run 20psi, you would run a spring that has 80 lbs on the seat. If one day you decide to turn the boost up to 30, you are no longer achieving your 60 on the seat. The stock springs seem to be pretty good for a stock camshaft and up to around 30psi. Once you start running more lift from a bigger camshaft, you will need to go with a heavier spring.

Most people don't know what to look for and they just run whatever comes out on the market and never look to see if the springs are doing what they are supposed to do. I have had aftermarket springs that start out at XX presure and after 2000 miles they have lost 10 lbs. I haven't seen enough 4b11 heads to look at the valves and springs to know what was going on. I have now done heads for 3 people and those guys sent me all brand new stuff so I wasn't able to look at the wear.

Every time a valve closes it bounces on the seat several times, regardless of the amount of spring pressure. We look at the spring seat to see if the spring has been rotating and we also look at the tip of the valve stem to make sure that there is a distinct solid line to indicate that the valve has been under control and not rotating as it opens and closes. In a year or so you will have shops and companies that have had more of a chance to look at these heads and develop products. Based on the older motors and what people have done so far, I would say you are ok running up to 30psi on the stock turbo and stock cams. One of the heads I did in the beginning was for a 42R car that was going to run a large camshaft, and since there were no springs available we supplied a really nice spring from PSI. Those are the same springs that we run in IRL and cup motors, but they make them in many different sizes, pressures, and finishing grades. We went with a high polish spring like the IRL, but with more seat pressure. The head flowed over 300cfm @ 28" and peak lift, so we were shooting for maxing the 42R out at about 35psi and 900hp.

There will be more spring options available in the next 6-12 months, so just be patient. If you plan on running a big turbo I would starting looking into spring options. The stock ones handle a suprising amount of abuse initially, but they fatique over time.

 

Great information! You mention fatigue over time, does this mean spring tension should be checked and if reduced by XXlbs replaced after some mileage? If so, what is that approximate mileage under "normal" use?

Also, in another thread regarding engine longevity under two options: OEM turbo at maximum output with just external mods (intake exhaust, O2 housing and reflash) vs larger turbo with same externals (and presumably larger fuel pump and injectors). Part of the post by Spdracerut was, "The stock turbo is completely strained at those power levels [~400whp]. Not only that, but it has a relatively small turbine housing causing a lot of backpressure in the exhaust manifold. By going to a bigger turbo, it'll be more efficient in that power range and also have a bigger turbine housing, both reducing the strain on the engine." Your thoughts on this comparison relative to longevity would be appreciated.

Later, Ken

 

This is not a ball bearing turbo. And actually this turbo hits max boost just like stock. I think i hit max boost at about 3700 RPMs. I am also 4500 ft above sea level. So if you are closer to sea level the faster you will get boost.