How irritating, by the time I finished typing out my lengthy reply, I timed out, had to sign in, and my post was magically gone. Hopefully I can type faster this time...
Anyway.... JW Taylor...
The engine I am building is not complete, so I can't give you any hard numbers as of yet. But, I can say if its anything at all like the twin-turbo 451 mopar stroker I built for my 75 Dodge D200 when I had it, just know that I
shredded the rear (Dana 70) the first time out. I actually expected the transmission to explode first, and not sure why that didn't happen.
The engine I'm building will go into this:
The idea is to fully load the truck up, and watch turbo-cummins Dodge Rams get smaller in my rearview. I am replacing a tired, high mileage 351W, not that it makes any difference what is there now. It won't be for long.
My build here has to overcome a lot of things. First, as you can see the recipient of this engine is not light by any means. I weighed it unloaded, both tanks full and I was six pounds short of 7000. I thought that was ridiculous considering it does not have air conditioning, any emissions equipment except the cat, no hitch and is single rear wheel, but the scale is certified by the state of NJ so I guess it has to be correct. Yes, she's heavy.
The second thing I have to overcome is emissions... while I have her registered as a commercial vehicle (due to a loophole in NJ state registration) I only have to pass an idle test, but it is something to take into consideration when building motors and turbocharging. Lastly, I also want "decent" mileage. "Decent" to me means low double digits. I'm not expecting 30 miles to the gallon. I just can't afford five
I'll stop being a windbag and respond to some of the comments you're received thus far.
First, Steve is correct in that the stock pistons are not suitable for a boosted engine, and trying to reuse them puts your engine reliability at risk. If you're cheap, go for it, but know you'll probably need a new engine at some point.
I will disagree however that hypertuerics are a bad choice, because they are a good choice in a boost engine for many reasons. Here is an analogy for you...
Take an empty mayo jar, remove the lid, and put it on the driveway lip down. Now stand on it. The mayo jar will survive your weight. Now have someone hit the side of the mayo jar with the claw on a big framing hammer. The jar will shatter, and you will drop about 6" closer to the earth.
In this analogy, your body weight represents the normal forces a piston willl experience inside an engine, the mayo jar is a hypertueric piston, and the hammer claw is a shock load - detonation.
The key to using hypertueric pistons in a forced induction engine is to avoid detonation. You can do this many ways... timing, intercooling, lowering the compression, water injection, etc. But if properly tuned, hypteurics are just fine. The problem I see over and over again is people not tuning their combination properly, or being unrealistic. But unlike cast and forged pistons, Hypertuerics do not radically change their size or shape when heated, therefore you will have better ring sealing and less opportunity for piston slap down the road. In a highly loaded engine, this is an important thing to strive for. You want the explosions above the piston, and the oil below.
Speaking of oil, when building your turbocharged engine you have to take into consideration the extra oiling requirements of the turbos, as well as the extreme heat you'll be introducing. On my last project, a twin turbo mopar 451 stroker (also for a big pickup - 75 Dodge D200), the turbos glowed a dark, dull cherry red color. That is hot. This heat goes right into the oiling system because the oil has to circulate through the bearings of the turbos, so you have to use a large oil cooler. For this project, I scarfed out of a junkyard a huge oil cooler off a Kenworth. Was a lucky find really. Anyway, you'll also need at a mininum a high volume oil pump, if not drysump.
Capone mentioned ceramic coatings. He provides good advice here. Coating across the piston tops, over the edges down to the top of the first ring landing area is important. You want the heat in the chamber, not in the hardware, so coat everything. Coat the intake and the exhaust valve heads as well, and the surface area of the head facing the combustion as well. Also put some effort with your dremel to make the chambers smooth and free flowing, casting flash and odd bumps you often find in head chambers do nothing but act as a beacon for detonation. Remove it all, make things smooth, and coat it well. Be sure to recalculate your compression ratio after removing any material in the combustion chamber, of course.
Regarding compression, one of the mistakes I often see is people are a little over-zealous with the boost on normal street engines in the 9:1 and up range. Even with o-ringing the block and heads, you cannot run radical compression with pump gasoline on a high compression engine. Diesel fuel yes, gasoline no. So you have to accept an approximate limit of 8lbs of boost on a street engine, or increase the boost and really lower the hard compression ratio of the engine.
How low is low? The engine I'm building now will have a 6.5:1 compression ratio. The reason for this is in the past several friends and I theorized and have proven with a dyno that more torque/power can be made by running a ridiculously low compression ratio and rediculously high amount of boost - in the 30lbs range... and yes, pump gasoline.
If you do the math, you'll find that for a given combination of rods and pistons, your rods will experience less of a load at 4000 RPMs with 30lbs of boost, than at 6000 RPMs with 5lbs of boost. Your pistons and rods will thank you if you think like this. Your headgaskets might not, but that can be resolved by using quality bolts like ARP, and o-ringing the block.
Your best friend in all this will be your knock sensor, and how it controls your timing (retarding as necessary). Too much timing under boost will give you detonation, and a nice shockwave that will break parts. Your knock sensor is the key to this. And don't just use any knock sensor. You have to find one thats appropriate for your block, and piston size. Knock sensors are essentially a microphone, tuned to a specific frequency. A 500cid engine, under detonation, will "ring" at a particular frequency. A honda 1.6L engine, under detonation, will "ring" at a different frequency. Its important to know this so you chose an appropriate knock sensor.
What EFI system will you be using?
The drawback to this is you won't enjoy neck snapping torque off the line unless you rev a bit in order to spool up the turbos... but for my purposes thats most acceptable. I have zero intention of running my bloated crewcab down the 1/4 mile... but instead if I'm doing 75 with 6000lbs of bricks in the bed and hit a 6% incline, it would be nice to maintain that speed. What are you building for? Highway or 1/4 mile?
Intercooling offers a fun debate. I know a guy with a Buick Grand National (v6 turbo) that is experiencing better performance after he removed the intercooler, and redid the code in the ECM so that the 7-th injector (cold start injector) on his engine joins in the on-the-road fun. No intercooler, plumbing is easier, less weight, less hassles. But you have to watch for detonation, Capone is spot-on.
And there are many types of intercooling too... none of course as my friend does, but also air to air, water to air, water or alcohol injection, etc. Its a big list actually, and your choice may be a combination of the above if you really want to push things. It really depends what you are building your engine for.
If you're building a highway cruiser, that will have a fair amount of airflow most of the time, air to air is very effective. If you're drag racing on the other hand, air to air generally is effective about half way down the track, then the intercooler becomes heat-soaked, and actually heats the air rather than cooling it. You may call it an "interheater" at that point. This is why a lot of the non-pro doorslammer guys run water based intercoolers, or run the airflow through an igloo cooler with a block of dry ice in it. After each run, they dump the "stuff" out and replace it with cold water or another dry ice block. For short bursts of power like drag racing, its extremely effective.
Water injection has been used on and off by the OEMs. VW did a lot of work in this area, even of silly things like VW Rabbits (GTI). Remember that the post-turbo air temperature can easily reach into the 300-400 degree range, way above the temperature that water turns from a liquid to a gas. So when the water is sprayed or injected into the air charge, it immediately boils into steam. By doing so, it absorbs some of the heat (energy) thus reduces the temperature of the air charge. Water injection also really keeps the combustion chambers clean. Your pistons and valves will be very shiney. The drawback to a water injection system is that it runs out eventually, so you have to pay attention to water supply tank size and keep it full.
Alcohol injection works the same way - the alcohol goes from a liquid to a gas at those temperatures as well, and has the additional property that it burns too. Alcohol is also a "dry" liquid, much like gasoline, so on my last project (the mopar mentioned above) I chose to inject a 50/50 mix of distilled water and isopropal alcohol.
