Engines under forced induction

[dado]

high revs kills the FI engine not high commpresion,so it is right balance really and properly run FI should outlast NA engine in my opinion.

[Shteifen]

this is good discussion, i like it!

i would think with an FI engine with a turbo would require a little more maintenance than a supercharged one, just because of the heat generated by the turbo getting so hot would make the oil turn acidic quicker causing the engine to wear. so i suppose a turbo engine would require oil changes more frequently, would that be right?
supercharger wouldnt get as hot i'd imagine.

i think i heard somewhere when i was younger that it puts components under less stress to make power at higher RPMs. like for example a stock 1.8t motor, makes its highest torque at around 1750 rpm. now wouldnt having the piston forced down with an explosion at such low rpm make give more stress to bearings in the crank and rods and such for a longer time, than making the same power higher up, at say 4000rpm? maybe thats not a good comparison.
i suppose making the power higher up might be putting less stress on the bottom end from torque, but more stress on other components, like rings, because they are doing that same movement with a force for a shorter period of time be much more often...


and just to clarify either NA or FI, i wouldnt be looking for massive power, just a fair bit more than i have now and a nice sound.
i wouldnt be skimping on any parts either, pretty much everything would be replaced, bringing km's back to zero, on the engine and maybe the gear box too.
if FI i was thinking a supercharger at around 6-8 pounds would do it, with some cams, in a three litre would do it nicely.
if NA i was thinking, still the three litre, cams, good p&p job, and maybe 10.5-11:1 compression, so not crazy compression but a bit of a bump.
either way i go, FI is going to be more expensive because i'd have to fork out for the parts of rebuild, and on top of that the FI parts.

-steve

[Bug_racer]

I'll make this a simple post as I could be here all day :

Turbo it . low boost with a fresh engine . If your worried about longevity and engine bay temps lower compression ratio and add a thermostatically controlled oil cooler . A turbo running low boost will have the most volumetric efficiency vs cost of any engine in the long term .

Keeping it naturally aspirated to gain more power your going to need to rev it harder , boring and stroking does little on a VR6 , its the head that cant flow . Once youve opened to the head up and it revs , you'll find your gonna need to cool the engine down cause of the extra heat generated & your gonna need to run high octane fuel all the time . You'll find you'll be getting more oil / coolant leaks as well , as well as the pulleys / p/s pump , water pump etc needing to be changed more often .

Supercharging is inefficient . To make the power you have to use the power , and on a small engine like the VR6 it robs it off too much in order to work efficiently . superchargers work better with larger displacement .

[Jarred]

I'll make this a simple post as I could be here all day :

Turbo it . low boost with a fresh engine . If your worried about longevity and engine bay temps lower compression ratio and add a thermostatically controlled oil cooler . A turbo running low boost will have the most volumetric efficiency vs cost of any engine in the long term .

Keeping it naturally aspirated to gain more power your going to need to rev it harder , boring and stroking does little on a VR6 , its the head that cant flow . Once youve opened to the head up and it revs , you'll find your gonna need to cool the engine down cause of the extra heat generated & your gonna need to run high octane fuel all the time . You'll find you'll be getting more oil / coolant leaks as well , as well as the pulleys / p/s pump , water pump etc needing to be changed more often .

Supercharging is inefficient . To make the power you have to use the power , and on a small engine like the VR6 it robs it off too much in order to work efficiently . superchargers work better with larger displacement .

/end thread imo

[gareth_oau]

more and more manufacturers are running forced induction these days, and they cant afford to do this unless it comes with a reasonable level of reliability or theyd bankrupt themselves with warranty repairs.

you can also expect that they will build a decent safe working margin into them so if you choose to go higher that standard then it wouldnt be overly risky.

I worked and turboed a 2L ford engine many years ago, and was getting over 250KW from an engine originally built for 70KW. Was superb fun until one of the conrods headed west instead of north/south. but in this instance i well and truly overdid it, and I suspect a lot of bad stories are from people who have overdone it, or not done it properly

[Shteifen]

good points.

i agree, new engine are made very well, and deal well with forced induction probably because of the massive budgets these companies have to invest in research and development of components to that last.

in an older engine type, like a VR6, to make it ready for forced induction would a simple rebuild be enough? would all the bearings, pistons, rods, valves, guides and such of an engine rebuilt with stock components be enough to deal with different levels of boost?
i mean that engine was never meant to be boosted, so is a refresher all it needs to be suited for it? or are there specialised bearings parts that should be used for a forced induction engine compared to an NA motor?

-steve

[gareth_oau]

i would imagine any dealing directly with the power, ie valve sealing, pistons, rods, BE bearings etc would need to be redone.

clutch as well.

and while its in bits, get your head port/polished - a lot of gains can be realised from removing manufacturers tolerances

[Shteifen]

yeah, id be gettin everythin replaced. probably go for makin it a 3 litre as well

get head fully rebuilt along with the p&p. probably wont bother with bigger valves or anythin though.
bottom end rebuild as well, all crank and rod bearings and whatnot.

ah well, theres so much i could end up doin, just a matter of whether i can justify the work/money/time.

-steve

[GoLfMan]

Listen to Bug_Racer (Seb) he has ALOT of experience in hotting up the VR6! He's building a VR6t drag car at the moment I think? (correct me if I'm wrong Seb)

as he said, I personally wouldn't supercharge it, you wont gain enough to make it worthwhile and a low boost turbo set up will yeild more power

[gareth_oau]

if youre already getting the head rebuilt, then why not use bigger valves? I cant imagine the incremental cost being too prohibitive and if youre going to be using/producing a lot more gases, you'd want to get them in and out of the engine a lot quicker?