Turbo ?'s

[Anonymous]

Hey guys:
Lately i've been toying with the idea of either a direct port NOS system tapped into the log intake, or a supercharger. After pricing both, i think it would be more fun and over all a better performance choice to lay off the gas and go with the super. Anyway, i have a few quick questions that hopefully you all could point me in the right direction on.

Okay, i currently have 9.6:1 compression (approximate, it runs on premium but not on regular...) Is this too high for a supercharger/turbo?

- I have a Comp 260H cam, and from what i have read, near stock with increased valve lift is best, right? So this cam with full roller rockers would be the best config?

- I have Ross custom forged pistons, ARP rod bolts, polished rod beams. Is 15-20 psi of boost unrealistic?

- With above psi, would i need an intercooler or would possibly water injection do the trick?

- Could I use a carb bonnet rather than an entire enclosure on my 500cfm 2bbl holley? What would be the advantages/disadvantages to either one?

- Most importantly, what would be the recommended turbo/supercharger for a blow through design?

Sorry about all of the questions, i'm new to the forced induction scene. Thanks so much for the help.
later

 

[rbohm]

8) 9.6:1 compression would not necessarily be too high depending on the amount of boost, and the cam you would run. a slightly larger cam and keep the boost at 6psi and you can run premium fuel on the street. for 15psi you need to drop the compression to about 8:1.
the comp 260 cam will work fine with the turbo.
the pistons, rods and bolts are perfect.
an intercooler would be my recomendation as it doesnt run out.
you can use a carb bonnet for a blow through install, but the enclosure would be better as you dont have to seal the carb shafts. you need to make sure the float is a material that wont collapse under boost.
you can pull a turbo from an svo mustang or tbird turbo coupe as they are blow through designs.
get the book by hugh mcinnes on turbocharging. you can pick upa copy at your local book seller or from amazon.com

 

[Anonymous]

Ok, I think 9.6:1 is too high to run a turbo with, on petrol. LPG is a different story, you'd be able to run something like 8 to 10lbs with 9.6:1, without much cause for concern.

If however, you want to keep on fuel, and it sounds like you do, I'd suggest dropping back to 8:1 for the amount of boost you want to run. What year head are you running? how big is the dish in your piston? have you had the block zero-decked?. An 8:1cr will give you some headroom for a turbo upgrade, more boost, etc. I wouldn't suggest staying with a carb for a turbo though, forced induction means you'll need a more precise fuel delivery system, if you intend on driving it pretty hard.. Perhaps an aftermarket 2bbl TBI and computer, with ignition control would do the trick?

 

[sefus]

the ideas are more compression = less boost avalible. youd only want 8-12 psi anyway. you do not need an intercooler. it will run just fine without one: no temp problems or anything. it would not be a bad idea though as it is a little extra power and will help to cool the charge: not that it hurts to not have one but a cooler charge is better. turbo choice is tricky. what is your full rpm range? when do you want it to start spooling? when do you want it to be at full boost? these are all things to consider in turbo selection. we are at roughly 3.3 liters so find a factory turbo charged car in this area. biger will spool later, smaller sooner. an oil fed IHI at this size would be perfect but there are so many sizes and companies out there you do not need to stick to just one. what is your plan for the fuel system? dont forget you will need a pump and pressure regulator that will work with boost.

 

[MustangSix]

I think 9.6:1 is definitely too much compression to add boost without a big crutch, like running only on methanol.

For pump high test gas and 6-8 psi boost, you need to lower it to around 8-8.5:1 unless you have electronic management of spark and fuel, then yo might stretch it to 9:1. An intercooler is a must for any boost over about 10psi. With EFI, spark management and intercooler, 14-16 psi is easy, 20+psi is doable.

A t3/t4 hybrid would probably be close to your requirement.

 

[BB6Mustang]

Nobody else mentioned this, but air charge temperature is more important than CR when it comes to detonation sensitivity. The more you cool the air the better. It is definitely possible to run 15-20 psi on a 9.6:1 motor with enough air charge cooling, but you would probably need at least an intercooler and water injection system.

The BLOWTHRU yahoo group has lots of people that have done forced induction with carbs. Check it out: http://groups.yahoo.com/group/BLOWTHRU/