Homegrown Turbo setups

First of all, I am a FI-noobie, so I pulled out my April 2005 issue and read the DIY Turbo article.

On any given day I have a wide range of theoretical car projects in my brain. Some of them involve adding a turbo to a NA engine. I am still a bit confused after reading the article so here is a hypothetical scenario that will hopefully clarify somethings for me...

V6 normally aspirated engine (no turbo models in the range). ODB1 and fuel injection. Research online shows that the stock block and internals can handle 8-10 psi. It's a budget build, so I want to use donor/junkyard parts, nothing new. The project is primarily for track / autocross usage, so turbo lag is the enemy.

So here is my mental gymnastics...

1. Single or twin turbo setup? In my head, it seems that a twin setup would be a better solution performance wise, but would require twice the parts. 2 smaller turbos spin up faster and create the same amount of total boost, thus potential performance... right?
2. Is a dual turbo setup even possible in a DIY / Budget build? Dual turbos being 2 turbos of different sizes stacked to provide power increases through a wider rev range.
3. In the donor cars section, some of the turbos mentioned are rated in lb./hr. and intercoolers are rated in potential horsepower. What is the math or method to equate that to PSI for a given turbo (for both single and twin setups)? And I don't understand how hp equates to temp for the intercooler?
4. In a twin setup is it better to use 2 smaller intercoolers, or route the air to 1 larger intercooler (assuming there is room for either method)?
5. As far as engine management, I know you can get very sophisticated (read expensive) but what are the best options on a tight budget? Making the assumption that elbow grease, time and effort are free.

BradLTL wrote: 1. Single or twin turbo setup? In my head, it seems that a twin setup would be a better solution performance wise, but would require twice the parts. 2 smaller turbos spin up faster and create the same amount of total boost, thus potential performance... right?

Single because it's cheaper, if you size it right and keep the revs in the right spot, lag is not your enemy...

BradLTL wrote: 2. Is a dual turbo setup even possible in a DIY / Budget build? Dual turbos being 2 turbos of different sizes stacked to provide power increases through a wider rev range.

You're talking about sequential turbocharging, sure it's possible, but plumbing is the difficult part, if you know how to weld, or know how to make couplers out of magic you can do it...

BradLTL wrote: 3. In the donor cars section, some of the turbos mentioned are rated in lb./hr. and intercoolers are rated in potential horsepower. What is the math or method to equate that to PSI for a given turbo (for both single and twin setups)? And I don't understand how hp equates to temp for the intercooler?

You can get into all kinds of fancy calculators, and they won't come close to what you put on the dyno. The lb/hr is flow rate of air at a given pressure, also used to describe fuel flow rate when talking injectors (sizing fuel system is just as critical as sizing turbo). Try this calculator to get a feel: http://www.turbofast.com.au/tfcalc.html be conservative with your intercooler efficiency, 80-85% is usually a nice starting point...

for the phD library go here: http://www.dsmtuners.com/forums/articles-miscellaneous/226187-useful-calculators.html

BradLTL wrote: 4. In a twin setup is it better to use 2 smaller intercoolers, or route the air to 1 larger intercooler (assuming there is room for either method)?

Depends, space, weight, plumbing, cost, all conserations, but like I said before, I'd go single, single, complexity means that many more places for a leak or something to go wrong...

BradLTL wrote: 5. As far as engine management, I know you can get very sophisticated (read expensive) but what are the best options on a tight budget? Making the assumption that elbow grease, time and effort are free.

MegaSquirt, have it, helped build it with my buddies, love it, works great, cheap (sub-$500), but if you have a car that has a very commonly modded OBD-I chippable ECU you may be able to save serious $$$ and time here by getting a map burned for it that'll work well...

Goodluck...

The answer to 5 is MEGASQUIRT! If you truly are a noob when it comes to FI and turbo's a single setup would be a good way to start, if you still have the itch after that, try fabing up a setup for twins, then at least you would have an idea of what you are getting into.

BradLTL wrote: 1. Single or twin turbo setup? In my head, it seems that a twin setup would be a better solution performance wise, but would require twice the parts.

Normally I'd go with a single turbo to reduce complexity. Unless you get a truly huge one, lag shouldn't be a factor. As long as you can find one big enough for your engine.

2. Is a dual turbo setup even possible in a DIY / Budget build? Dual turbos being 2 turbos of different sizes stacked to provide power increases through a wider rev range.

I wouldn't try unequal sizes without some very sophisticated controls. But twin turbos are certainly possible on a budget; look at the Corvette from the $2007 Challenge. On some engines, it may be easier to find two small turbos than a single one large enough.

3. In the donor cars section, some of the turbos mentioned are rated in lb./hr. and intercoolers are rated in potential horsepower. What is the math or method to equate that to PSI for a given turbo (for both single and twin setups)? And I don't understand how hp equates to temp for the intercooler?

I suspect they're mostly going by CFM of air flow for the intercoolers, but a lot of those horsepower ratings on intercoolers should be taken witha grain of salt.

4. In a twin setup is it better to use 2 smaller intercoolers, or route the air to 1 larger intercooler (assuming there is room for either method)?

A single large intercooler is usually best for packaging reasons.

not to hijack the thread.... but hopefully continue it.....

are there any common factory turbo setups that would work well on his theoretical stock v6 motor looking for 8 to 10 psi of boost?

itsarebuild wrote: not to hijack the thread.... but hopefully continue it..... are there any common factory turbo setups that would work well on his theoretical stock v6 motor looking for 8 to 10 psi of boost?

depends on the displacement and flow rates of the engine in question, if it's a 1.8L v6 from a mx3, that's a far cry from a 3.5L GM unit...

The Biturbo in an S4/A6 2.7T had K03 turbos if I remember correctly. They have two intercoolers and have around 250 hp at stock boost levels.

I'd say a CT26 off a MKiii Supra Turbo should fit the bill nicely. 10psi is a nice spot for those, and they aren't terribly small.

Hell, i'll have a spare in nice shape in about a month that i'd let go for a challenge-friendly price.

From a purely academic perspective, there is nothing about twins that magically make the setup more lag free, there is more rotating mass per CFM in each unit (the flow into each is divided by two, as well) although the twins are probably going to be easier to find and cheaper...

what about converting a turbocharger into a belt driven supercharger? Its something Ive been turning over in my head for a while now...should make it a bit simpler at least from plumbing perspective if your handy with machining. The extra grunt in a V6 would definitely be a bonus for a supercharger. Also, not having to find/fab an exhaust manifold is a budget helper as well.

4cylndrfury wrote: what about converting a turbocharger into a belt driven supercharger?

The biggest difficulty with that is getting a reliable 80,000 RPM geartrain to drive it.

You can get used Vortech chargers (basically what you want) for cheaper then it would take to figure out the gearing.

Raze wrote:

itsarebuild wrote: not to hijack the thread.... but hopefully continue it..... are there any common factory turbo setups that would work well on his theoretical stock v6 motor looking for 8 to 10 psi of boost?

depends on the displacement and flow rates of the engine in question, if it's a 1.8L v6 from a mx3, that's a far cry from a 3.5L GM unit...

true, i guess i was asking relative to some common motors that may be out there like a gm f body v6, a ford mustang v6. a honda accord, or some other appliance type car that you can get cheap in a salvage yard. so maybe there are different turbo set ups that would be more suitable to different motors? or turbo setups that are pretty bulletproof and simple from the factory and a newbie could swap in without having to do a lot of research on these things.

a seem to hear a lot about volvo turbos and stock turbos from cummins diesels. are they good candidates or are there better options out there?

itsarebuild wrote:

Raze wrote:

itsarebuild wrote: not to hijack the thread.... but hopefully continue it..... are there any common factory turbo setups that would work well on his theoretical stock v6 motor looking for 8 to 10 psi of boost?

depends on the displacement and flow rates of the engine in question, if it's a 1.8L v6 from a mx3, that's a far cry from a 3.5L GM unit...

true, i guess i was asking relative to some common motors that may be out there like a gm f body v6, a ford mustang v6. a honda accord, or some other appliance type car that you can get cheap in a salvage yard. so maybe there are different turbo set ups that would be more suitable to different motors? or turbo setups that are pretty bulletproof and simple from the factory and a newbie could swap in without having to do a lot of research on these things. a seem to hear a lot about volvo turbos and stock turbos from cummins diesels. are they good candidates or are there better options out there?

Tbird turbos
Holsets from cummins
Supra turbos
Saab turbos

The rest in all honesty, are kinda meh. Supra turbos are kinda meh as well, but they're just dandy up to about 16psi.

if you want to look for cheap used parts try forums that are catered to turbocharged (or supercharged) cars , like dsm , turbo nissans , turbo mazdas , turbo fords , turbo volvos , vw , 03-04 cobra , ebay is a nice source of new stuff like piping and intercoolers and bov/wastegates for cheap.

try to think of your engine comparatively with others of similar displacement and design to visualize your goals and restrictions...

This whole discussion is meaningless without knowing how much flow you want at 8-10psi, saying 8-10psi on a v6 means nothing...

Figure out what motor you want to use, figure out how much flow it needs through the RPM range

Figure out how much boost you want to add to that (aka increased flow rate)

Find a compressor map for a turbo which has the above point in it's efficiency range at that pressure (most maps are at a given temp)

Select compressor/turbine combo (many can be hybridized or may have been if it's a rebuild). This is where you'd want to run down the list of an IHI, KKK, Holset, Garrett, Chinese knock-off, etc...

Size your fuel system, pump, injectors, fuel pressure regulator accordingly to deliver enough fuel to achieve desired AFR/speed density/whatever method you want to run w/o detonating...

plumb up an intercooler setup, top mount, front mount, air-to-air, air-to-water, air-to-ice, methanol injection, CO2 spray, your only limits are your ability to scrounge, fabricate, and or pocketbook...