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Anonymous
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hey im Building a 40psi 250 cross flow and i was hopeing somebody could tell me what exactly i need to build it
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Most turbos can't produce 40 psi worth of pressure by themselfs. You'll be looking at a twin turbo set up ran in series. You could also run a paxton with a turbo forcing air into the inlet side. Some sort of staged set up is what you will be looking for. Hope this helps some.
userman":27ukceog said:
Welcome mate. Oh boy, what a way to start off! This is just a ramble on the details, not a comprehensive list at all, cause I've never run 40psi let a lone 9!
First, lets look at what you are expecting.
40 psi won't work on a road car unless you have a 3000 rpm + converter auto. It will have so much lag, it'll take 2 seconds and 60 feet just to spool!
There is a need for an intercooler. 40 psi is an effective boost ratio of 3.7 times normal air pressure. While you are busy smashing the air mix together, air is getting heated by the compressor, and then by the growing amount of compressed air inthe intake plenub. This means you are going to create a massive amount of heat. It's likely, even with two huge stacked intercoolers, that your effective boost ratio won't get over 3 times atmospheric.
If, before turbo, your engine could make 200 hp net @ 5000 rpm at the flywheel, then with a 40-psi boost, you'll see less than 600 hp, tops. If it has 250 or 300 hp at 5800 rpm before turbo, it'll make 750 to 850 hp. With nitrous, there is boosting the stock turbo size, for a 900 hp potential. Nitrous lowers the critical loads by forcing the peak power rpm down 500 rpm or more. It increases bearing loads, and cross drilled cranks with full grove bearings are not a good idea.
A 40 psi engine is so far up there, it'll need the best steel 300 Ford rods, Carrilos, or alloy rods, a cast crank will need regular replacement, the overall rev limit will have to stay down to 6000 rpm tops, and AVESCO-style triple lug roller rockers will be needed, or an iron head with 7/16 screw in studs. This is why people are going sohc. Another thing. The valve pressures are going to be so high cracking the valves off the seats that valve gear failure is likely. The pushrods a bundy tubes, and are under extreme load. The block should handle most of the racket, but I'd look at half filling the water galleries with Hard Fill grout.
If you limit the rev range, any thing is possible. A soft ramp cam, which has the cam taking up the lash with a long 10 degree ramp rather than th 6degree ramp of newer cams, is one important means of protecting the rocker gear. Look for good duration. Wades old 392 grind cam has lots of duration, but doesn't have a savage ramp. Dick Johnston used it on his True Blue Falcon and in his Toranas. The duration is long, but it doesn't hurt as long as the turbo is operating at wide open throttle. Surge with long duration cams is the reason people sugest sub 270 degree cams on street turbos. Don't worry about duration blowing ehxast out, a turbo engine responds to a cam just like a normally aspirated cam does. Do get a wide lobe spepartion angle, greater than the stock 110 item, if you can.
If its legal in your drag class, the solution for turbo lag from a too big puffer is to run a 100 hp nitrous nossle impinging on the impellor, and an extra injector downstream. The nitrous cools the turbo, mixes with the fuel, and acts as an intercooler. The nitrous use of 100 hp of nitrous is one third of use of a 100 hp kit on a non turbo engine.
I wish you the best. Take this lot, and see your machinist. If your the machinest, don't exist stage left, youre on man. Break a rod!
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Anonymous
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I was thinking that you might beable to turn it into a diesel with about 10 to one compression to start with and about 25 lbs of boost is the range of diesel fuel.
What would be a safe compression ratio for a motor running 40 psi or even 25 psi? I'd think less then 7.5 or 6.5.... Even race fuel has it limitations. Something to think about. Thanks.
What would be a safe compression ratio for a motor running 40 psi or even 25 psi? I'd think less then 7.5 or 6.5.... Even race fuel has it limitations. Something to think about. Thanks.
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Anonymous
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40 psi on a 200hp n/a motor will throw way more than 600hp. 15 psi on a 200 h/p motor will throw 350-400hp and 25 psi around 500. 32 psi would probably be more like 600hp. what the hell do you want 40 psi for?! run 25 psi and some n2o save yourself the lag and expense of a twin turbo setup, turbos alone will cost like 4k if your looking into 900 hp potentials.
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