I know that turbo's make insane amounts of torque with a lower amount of hp. Theforced4twister turbo kit I read puts out 333rwhp and 400+Torque at 10psi. I know out block's limits unforged is 400rwhp, but would 400+rwhttorque be pushing the limits too? I read it's suggested to get at least shimmed valve spring for above 8psi boosting on the turbo, butwould that be all I need for a reliable daily driver at 7psi on weekdays and 10psi on weekends?There is anadjustable psiswitch, so I couldturn it down to7psi. And would there be any transmisson issues or rear end issues if I leave them stock? Thanks for all the help ahead of time!

 

I think 9-10 psi is fine on the stock block. If fazm doesn't answer this thread I would recommend pm'ing him because he probably has the most experience with turbo on the stock block. They aren't currently making the forced4 kit either.

http://forced4.com/v6turbokit.html

 

You will have no problems at those PSI levels. Most f/i people are running at that. Supercharger or turbo, PSI is PSI, it is just extra pressure on the engine. Superchargers at 10psi are actually making the same amount of power as the turbos, but a lot of it is being lost to crank the unit. All those kits out there will work just fine as they come. You really only need to worry about changing things when you change things on the f/i setups

 

With the turbos, 8-9lbs of boost is 100% on the stock block, at 11lbs, you could experience valve float with the turbo and I would at that power level, shim your valve springs. But you can run 11lbs of boost all day long on the stock block.

 

It takes a centri 10-12psi to equal what a turbo makes at 8-9psi. I was running 12.8's consistantly at 8lbs of boost with the Ph turbo. A centri would need 10-12lbs of boost to match those ET's (and for some, it took them 14lbs). This is because people look at peak HP, and the turbo has power in a wider power band, lower rpm and it takes less to get into boost. With a centri, you have to make up for this with a more aggressive gear, shorter tire, etc to spin the motor and get into boost.

So from a peak HP point of view, psi is psi. But for street and track performance, you have to look more at the power band, and low end tq. That is why the X shines on auto-x, cause the power can be instant at idle. All depends on your applicaiton and goals.

 

I was not talking about power to the ground. I was talking about the power that the engine is actually making. When I meant was that 10psi on a turbo has the same strain on the engine as 10psi on a supercharger. However, because the supercharger is parasitic, you will see much less power actually being transfered to the ground. So to answer the original question, "is 10psi too much for a turbo on the engine", I am answering "no, because most superchargers do 10psi". Sure they put down less power to the ground, but at the crank they should be the same.

 

Really Great Info! So now my ? is, where could I get shimmed valve springs and an estimate of what they would cost?(install hard?) And, do you guys think 4.10's would be too much for a small turbo like the forced4 kit has? 3.73's ok? Stock 3.31's? Thanks aheadof time!

 

4.10s would be too much, stay with 3.55's or 3.73's. Some even get by with the turbo fine on stock gears and just go to a smaller tire. Any shop can do the shimmed valve springs, the shims themselves is like 10 bucks worth of parts, its more labor at around 300-350. Call Powerhouse, they have the info. www.powerhouse411.com.

 

Chris,

Crank HP ratings are obsolete once your roll it off the dealer lot, only dealers use those numbers. We have can only use rwhp SAE as its the measurement we have unless we want to pull the motor and put it on a engine dyno seperately.

I do see your point, stress on the engine is stress on the engine. And agree he should be fine anywhere from 8-11psi turbo on the stock block.

Hows the custom IC project coming on your car?

 

totally agreed with lol

for the IC, I am actually done with it. the tune is too safe though, running at ~10.2 AFR, but with that and 10.5psi, I am making 287rwhp. I was gunna go for a retune to make it more aggressive and hopefully break into the 300s, but I am running out of money lol. I have a thread on the 40c with pics and all

Oh yeah, and those numbers are on a Mustang Dyno, so I am probably in the 300s on Dyno Jets, but I really am only concerned with the MD numbers