Frederic,

excellent post, very thorough and informative.

THE ONLY area you and I will disagree is the type of piston to be used in ANY forced induction engine. Other than this....you are right on the cashola.

Pistons designed for Forced induction typically have a dished or reversed dome as they call it....in order to "contain" the explosion from the power stroke as best possible. The dished crowns help keep most of the thermal energy over the center of the piston crown keeping the rings cooler than normal flat top or domed pistons.

Also...the forged pistons designed for forced induction have different ring land to piston crown clerances in order to hide the rings from the extra energy.

I do advoacte the thermal barrier coating on the piston crowns ad above the top ring land....I also advoacte the skirts be dry film moly lube coated to help with the additional side loading on the piston.(lateral stress is what causes the piston to rock in the bore causing the galling and affecting longevity and reliability)

Valve faces should also be thermal barrier coated as should the chambers. I prefer to polish them for n/a motors...but for turbos the coating is a must.

The exhaust side of the turbos must get the thermal barrier coating as should the downpipes and headers.

Valve stems should also get the moly dry lube coating

cyl heads, intakes, oil coolers, intercoolers, intake and oil reservoir sides ofturbos should all be thermal dispersant coated for maximum thermal transfer efficiency from the oil.

I will agree that air to air intercooling is the way to go.

As far as detonation goes...the static compression of the engine should be around 7.5-8.5:1 (depending on application), Detonation control is where the forged dished pistons will come in...these minimize hot spots andspread the thermal energy in the chambe the way it should be. Since explosions are spherical in nature, the effort to contain it must mimic the phenomena as closely as possible.

Yes, a knock sensor will be your best friend.

A datalogger will also help you determine where the engine has lean or rich spots...and allow you to adjust accordingly in order to keep your exhaust system from glowing cherry red. (mostly caused by lean spots in the powerband)

I also recommend the use of interlocking piston rings to control the oil and compression better.

HV oil pumps are also an essential part of running any turbo.

I have heard of water or alcohol injection to help offset detonation...but a properly built engine, with the right pistons, Intercooler, quench tolerances, casting flash removal and cotaings as well as engine management usually won't need an "extinguishing" injection system.

As far as fabrication is concerned....that is where the fun begins..mwuahaha

 

dished pistons....

Yes, in street engines, dished pistons make a huge difference. However, I tested on a dyno a bunch of Buick V6 4.1L engines and found if the compression is below say.... 7:1 or thereabouts, it made absolutely no difference whatsoever. If you look at two identical OEM engines, one naturally aspirated and one turbocharged, you'll find more often than not that the turbocharged engine has dished pistons and the N/A engine has flattops, and the reasons you stated is 1/2 the reason. The other 1/2 is the dish pistons, everything else being equal (rod length, stroke, deck height, head chamber volume) you get a little less hard compression ratio, allowing room for more boost without getting too crazy.

But on my 6.5:1 c/r 500cid stroker, I can pretty much use whatever I want only because the compression is so low.

BTW do know that I wasn't trying to suggest that dished pistons, or forged pistons were a bad choice, quite the contrary. I happen to agree with you. I was merely trying to suggest that under certain conditions (like mine) hypertuerics are actually not a bad choice, and I attempted to explain some theory as to why. I was not trying to suggest hypertuerics are an excellent choice for all applications - of course not.

I simply offered my experience and what I've personally witnessed and proven thus far, based on many experiments and built engines I've done in the past. Some experiments that had catastrophic results and a hefty price tag.

Along the way with any kind of experimentation, occasionally you find out something interesting and go hmmmm. A low compression engine, under high boost with hypertuerics working very well was one of those observable abnomilies, and I thought it was worth mentioning.

The other thing I'm about to do, is bore a hole part way through the side of the block towards the liner of cylinder one, then tap it for a 200psi oil pressure sender. Then in the center of that incomplete hole, I'm going to bore a pinhole so the pressure of the cylinder can be monitored.

Its a very cheesy way of estimating power based on cylinder pressure. After all, thats what makes power

 

cut and pasting/timeouts

Thanks Bdraft for the suggestion... I could do that if I weren't using a text browser("Lynx") through a SSH window

 

Frederic,

you are indeed right.........with your experimentation and results, I would say that Experience will almost always outweigh hearsay.

re:twin 2.3L turbos
---------------
These should suffice in providing an ample amount of airflow for a 5.8, Changing the impeller to create a hybrid turbo would really benefit the larger engine. The smaller 2.3L Garrett turbos will spool up quicker and offer better low end torque and less turbo lag than largerturbos. THe drawback is top end....

It is an inverse relationship.

I also recommend a stud girdle for this application.

 

frederic,
I am new to this sight and I have grown to like it and thanks to guys like you I have learned a great deal.

I ahve a project that I have started on and have determined what I am going to do with the engine in my show truck.....

1988 F-350 4x4 dually ( 4-link air ride and 6 , 44inch boggers)...seriously
Powerplant......466 inch twin turbo big block....Thus my questions

My goal is a "mild" 500-600 hp street driveable(pump gas) ,blow through carb system (simplisity) I have started on my bottom end and have left it low on compression for this purpose....Haven't cc'd yet but around 8.00 ????? I would guess.

What suggestions would you have to meet my goal ?
Header material?
What turbo? T04's?
Who sells a carb box?
Carb size? How to set carb for this?

Any advice would be greatly appreciated.

 

re:What suggestions would you have to meet my goal ?
Header material?
What turbo? T04's?
Who sells a carb box?
Carb size? How to set carb for this?
----------------------------
Header material = stainless steel, preferrably thermal barrier coated stainless

What turbo? YOu have to go with a larger turbo due to the large CID.
A ported and coated T04S would probably do the trick quite nicely. These are good for up to 700hp.

Carb box, you'd most likely get away with using a Paxton Carb box from their supercharger kit.

Carb size? 850 holley with implosion proof bowls, lots of jet and transition cicuit work will need to be done to get it to work right, but the results will be astounding.

If you can get a main capstud girdle, I recommend it. You will also need an upgraded HV oil pump, (Melling) along with an oil feed line to keep the bearings lubed.

You probably won't need twin turbos (unless you want top end) Just route the headers into a y pipe and have them both dump exh into the turbo flange....(this is how the Buick GNs are setup)

thorough use of coatings will yield you longer lasting components and better V.E.

Get your heads port on the exhaust side....and do use nice headers to help exh flow.

Oringed head gaskets are also rec'd Felpro makes a set.

 

Hooking78,

Sorry I was slow, I don't read FTE every day... usually anyway

BTW, with a slightly stroked 460 like you have, 500hp is doable naturally aspirated with porting and some cam (lots of lift!). You can skip the turbos if you're c/r is in the 10:1 range. Just a side note.

8:1 like your looking at is low enough you could pump in about 12lbs of boost very safely. 15 if you're careful and going to spend time tuning. Maybe a hair higher. Two GN turbos (To4's) would be about right.

Carbs are fine, a lot of folks are afraid of turbocharging carb'd engines but its less complicated to do than an EFI system. You fabricate a "bonnet", essentialy a box that bolts to your carb pad, and the carb goes inside, and you increase the jets quite a bit. use a good quality electric fuel pump for consistancy.

Header and turbo plates/flanges should be 3/8" stainless or 1/2" mild steel, the tubing can be 1/8" stainless or 1/4" mild steel if you want it to last. Of course you can use flimsier materials but then you'll be replacing them every so often.

Coat the insides of the headers to protect them from excessive heat, and force that heat (which runs your turbo!) into the turbo.

Cast Iron manifolds actually would work find in most cases, simply braze your steel or stainless steel turboflange to the manifold outlet. The only thing that stinks about using cast manifolds is the outlets may not necessarily be where you want them. But for a street application, you don't need fancy tri-Y headers and all that jazz.

I don't know offhand of anyone selling carb boxes (bonnets), but they aren't difficult to make. Weld together 3/8" thick steel plates to make a box around your carbuerator, so that the top screws down onto a 1/2" lip with machine screws, and use a gasket to seal that up. Works fine, I did it once before for a friend's hemi.

 

Well I stopped getting e-mail notifications and appears I missed a lot of info.


frederic

Appreciate the info. Seems the 2.3 turbos or turbocoupe turbos on a twin setup is very common on a 351w engine. I may keep my eye out for two of those or a Holset H1C off a 5.9 cummins. Then again I have the ported D0's sitting here with the comp cams so I may just run that be happy. Thanks again for the information

 

No problem JW. chrysler 2.2L or turbo t-bird turbos (two of either) would be a good starting choice.

If you undersize the turbos a bit you'll have more oopmth off the line because they will be spooling up earlier. Then your top end suffers.

But, do you reallly need to sit at 6500 RPM cruising down the highway? Probably not

Whatever turbos you go with, try to keep the spindle speeds in the 85k-95K range, and not much higher. Measuring turbo RPM is a good way of determining after the fact how far off you really were. Not that it matters *that* much. If they are sized within 10% its more than fine for a truck.

Perfect is the enemy of good enough

 

Thanks for the info, I am going to to use twin turbos mainly just for the awww factor it will be built as a show truck. Thats why I want it to look pretty with tubular coated headers and lots of polished aluminum an ss steel. I had turbonetics quote me a price on two T04 turbos with exhaust housing coated and intake side polished for around 800.00 a piece ????? Good ...,....Bad ....what do ya think?

 

Hookin - the price doesn't sound unreasonable, but I really can't say for sure since I rarely, if ever, buy new stuff.

I haven't built a show vehicle (or did a full restoration) in about a decade, when I do make time to build something, I build sleepers. No chrome, no lift, no drop, no wings, no spoilers, no nothing.

Looks stock until you see my taillights get very small very quickly

 

Well I have hopes to open an off-road shop and I need something to advertise with. In that case something extremely out of the ordanary is what I want to go for. 24 inches of lift six 44 inch. mudtires, air ride and a fourlink suspension system, and two turbos may fill that requirement.

 

Make sure its a crewcab

 

If it's just going to be a trailer queen (or king), does it have to be functional?? Just a question. Also, unless you're driveing it around the shows and stuff or driving it and from shows (that much height it would be illegal on most if not all roads, so fair ground romps only), it only has to run long enough to get off the trailer and to get back on the trailer. Though the occasional blip of the throtle would be cool and may give you an "ohhh-aaaa" with people standing around watching.

if you want to go oinkers on it....I believe I have seen a supercharged and turboed system. I believe they had the turbo's feeding the super. That may be intresting.

You could also have a triple turbo, 2 smaller turbos off from each bank feeding a single larger.

Or quads, each bank has a turbo feeding a turbo. You could try rigging up a split intake then of some type, each bank getting air and fuel independantly of each other.
That would be a bugger to rig up and configure, and a real pain to tune I'd think.


The split quad and the super-turbo would be hard. The triple would be somewhat easier, then you could goto the salvage yard and get a single turbo off like a 5.9L Cummings out of a Dodge, or a turbo off the 7.3L desiel out of an Effy (F-250 or F-350 or higher) to compliment your to smaller single turbos.

Alternate meathod would be to have the quad turbo but feeding into a single standard intake, the dual intake manafolds and stuff can be skipped.

Hard chrome it all, paint the engine "Ford Blue"....and then put a link to the pictures of it in here....
Oh, if you do go the twin, triple, or quad turbo route, you mibht be able to get away with straight pipes, turbos have a tendancy to quieten down the exhaust, and the pure turbo whine might be cool.

later...
bdraft

 

I have been planning the twin turbo for the last few months. I have used toohighpsi.com for gathering my information. 2.3l Turbos would be a awesome match with some BBK Shorties. Half of the stuff I have except for the turbos and plumbing. Running a 8.0 - 8.5 :1 would be a safe range to work.

The only bad thing would be the loss of traction within a pickup.