RB30 engine conversion (lots of pics)

[SteveN]

Originally Posted by Cord

Why so low?

Rod Bell has built OSG RB30s at 7.5:1 for customers who wanted a reliable 700bhp on pump gas, has he not?

Granted, that dont stop the crank pulley flying off mid journey, but it stops melted pistons.

Id not go to 7.5:1 unless i was running coming on for 2bar held on pump gas tho, and the 7:1 thats been mentioned sounds like "2.5bar held, on pump gas and mild duration cams" style compression to me.

Shocked if lower comp affects boost threshold much tho, certainly not as much as big ports and lairy cams do (which also compounds any bad effects lowering comp would).
Certainly would lose some off boost power, but not actual boost threshold really, unless it was mapped for the higher compression still.

Im bored of RBs anyhow, bloody things

[tonysoprano]

Originally Posted by SteveN

Rod Bell has built OSG RB30s at 7.5:1 for customers who wanted a reliable 700bhp on pump gas, has he not?

Granted, that dont stop the crank pulley flying off mid journey, but it stops melted pistons.

Id not go to 7.5:1 unless i was running coming on for 2bar held on pump gas tho, and the 7:1 thats been mentioned sounds like "2.5bar held, on pump gas and mild duration cams" style compression to me.

Shocked if lower comp affects boost threshold much tho, certainly not as much as big ports and lairy cams do (which also compounds any bad effects lowering comp would).
Certainly would lose some off boost power, but not actual boost threshold really, unless it was mapped for the higher compression still.

Im bored of RBs anyhow, bloody things

Your only just out of nappies.

Lol

Tony

[bobstuart]

STEVE N

I hope that your engine runs good when you have it finished as you seem to think you know everything about building engines


Or will you do the same as you did with your cosworth and sell it in bits rather than let everyone see how it runs

[paul cawson]

Originally Posted by R32 Combat

I wanted 8:1. I might get the block decked and re-ringed. I'll find out exactly whats what when I have the pistons.

Could the heat tranfer from the piston crown to the cylinder block have been changed by the sealing rings that have been fitted.

[SteveN]

Originally Posted by bobstuart

STEVE N

I hope that your engine runs good when you have it finished as you seem to think you know everything about building engines


Or will you do the same as you did with your cosworth and sell it in bits rather than let everyone see how it runs

What you talking about you clown? Thats complete lies! Who are you anyhow? Apart from another old guy with his facts wrong, of course.

I sold my Cosworth as a whole, and the engine was running in its final form for about 1.5yrs and 13,000 hard miles. And 20k+ in other forms in the 2yrs before it.
Countless people saw how it ran or have been in it, inc planty of well known people who are still around today, so that makes as little sense as the rest of it.
It was only a 400bhp T35 engine anyhow, nothing special on the engine front.

It was sold in bits by who I sold it to at MY request, ie I sold it to him for a bit less than others offered me because I didnt want someone to get it featured in a mag (something I was never interested in as wasnt complete in my eyes) and take the credit for a car id spent 3yrs doing.

Who said I know everything? I certainly dont think so, I just have a slightly different view of speccing engines than some openly admit on here (but a lot closer idea than many seem to have you believe ). I like boost and torque, other like revs and, err, more revs!

Might well flog the engine tho, lil bit bored of RBs, got other ideas.

My engines got nothing to prove anyhow, just a nice drivable powerful engine, similar to tons of other RB30s (OSG and not) in this country and abroad, so that makes no sense either...

PS- Your username dont come up on the "other" forum, but youve mentioned it in your posts here, so I take it this is one of them from over there hiding beind an assumed name?

[R32 Combat]

Come on chaps, no bitching here.

[Cord]

Originally Posted by SteveN

Rod Bell has built OSG RB30s at 7.5:1 for customers who wanted a reliable 700bhp on pump gas, has he not?

Granted, that dont stop the crank pulley flying off mid journey, but it stops melted pistons.

Id not go to 7.5:1 unless i was running coming on for 2bar held on pump gas tho, and the 7:1 thats been mentioned sounds like "2.5bar held, on pump gas and mild duration cams" style compression to me.

Shocked if lower comp affects boost threshold much tho, certainly not as much as big ports and lairy cams do (which also compounds any bad effects lowering comp would).
Certainly would lose some off boost power, but not actual boost threshold really, unless it was mapped for the higher compression still.

Im bored of RBs anyhow, bloody things

Are you attempting to have a dig? Or Am i just reading it wrong???

I'm not aware of any RB30's that we've built for customers that have been under 8:1 and I've built all of the RB30's apart from the first one in the country which Rod did at Middlehurst's years ago. Maybe it is that one you are refering to?

If you are agreeing you lose off boost power, then how can you assume you don't alter boost threshold, it's exhaust gasses which drive the turbo, and quantities of exhaust gasses are linked to how much power the engine is making.

We've run engines in near identical states of tune but with diferent CR's and the differences do exist. I am only speaking from my own experience so that others don't need to go to the time/expense of experimenting. If you have evidence to prove my thinking incorrect I would be VERY interested to hear it.

[R32 Combat]

Update.

New shells are here.

New pistons are in the UK, should be coated soon by http://www.dlcuk.co.uk/index2.html

I've blagged a burette from Glos Uni(Cheers Loz)

Next step:-

Get the block bored,
Dummy build
Calculate amount to be machined off the block to reach desired compression ratio
Machine block and re 'O' ring
Clean
Re-build
Enjoy



But at the moment


Tick follow tock.......

[gtr1987]

There is a question that has been bothering me around. I'm wondering if displacement of the engine really affects the horsepower output of the turbocharged engine. Lets say i got a RB26 engine, at 2.6 litre, running twin GT-SS turbos. This engine will be producing around 450-500 hp. Now, let's say i bore the engine up to 2.8 or 3.0 litre, still using twin GT-SS turbos, will i get more than 500 hp? Another question, say if i swap the engine for larger displacement engines, like a VK45DE engine(4.5 litre), still running twin GT-SS turbos but with the addition of external wastegates, will i get more than 500hp?

[fabianGTR34]

well bigger displacment will make more power with the same amount of boost,
The average cilinder pressure is converted to a force by the piston, and the rod and crank convert it to rotating force, (torque) The force is created by the pressure X surface area of the piston (bore) so a biger bore creates a bigger force with the same pressure. A long stroke has a relative small bore ( surface but the pressure doesn't drop as fast during the stroke, resulting in high torque with relative low horsepower. A bigger bore will convert the pressure to a bigger force, but due to the bigger bore the pressure drops relative fast during the stroke, resulting in higher horesepower and relative lower torque.

As for the bigger engine with the small GTSS, It is more commont to mach a turbo to the kind of engine, the exhaust flow rates of the 4,5 liter engine are different ththan a smaller displacement engine, so the small turbines could become a restriction to the engine, I can emagine that the gtss on the 4,5 liter engine restrict the max power due to the small turbines, but if you let that aside, they will make more power at the same boost level due to the bigger displacement.

[gtr1987]

What you said is right. But according to Welcome to TurboByGarrett.com , the horsepower output of the engine does not increase according to the displacement. As in this formula:

Wa= HP* A/F *BCFC/60

Where:
· Wa = Airflowactual (lb/min)
· HP = Horsepower Target (flywheel)
· A/F= Air/Fuel Ratio
· BCFC/60= Brake Specific Fuel Consumption ( ) ÷ 60 (to convert from hours to minutes)

As you car see here, airflow target when searching for the suitable compressor doesn't take into account the effects of displacement. Since that is the case, how can HP increase when engine displacement increase?

In the same website, there is also this formula:

MAPreq=[Wa*R*(460+Tm)]/[Ve*N/2*Vd]

Where:

· MAPreq = Manifold Absolute Pressure (psia) required to meet the horsepower target
· Wa = Airflowactual(lb/min)
· R = Gas Constant = 639.6
· Tm = Intake Manifold Temperature (degrees F)
· VE = Volumetric Efficiency
· N = Engine speed (RPM)
· Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61.02, ex. 2.0 liters * 61.02 = 122 CI)

In this formula, you can clearly see that Manifold Absolute Pressure is inversely proportional to the engine displacement. So, in this case, if you set the twin GTSS turbos to produce 1 bar boost in the 2.6 litre engine, when you use the turbos with the 4.5 litre engine, it will not hold 1 bar boost. Is this true? What are the effects on the horsepower output on the engine? (Assume that turbine restriction doesn't exist)

[fabianGTR34]

how can HP increase when engine displacement increase?

Because the maas airflow of a bigger displacement engine (compairable engine) is bigger, and the total mass of air that gets into the engine determains the amount of power that can be made.
If you increase the pressure of a smaller displacement engine, you get more mass of air in the engine and so more power.

if you set the twin GTSS turbos to produce 1 bar boost in the 2.6 litre engine, when you use the turbos with the 4.5 litre engine, it will not hold 1 bar boost. Is this true? What are the effects on the horsepower output on the engine?

1 bar on 4.5 liter means that you have to double the volume that is pumped tound by the 4.5 liter engine, this amount is bigger than the rb26's.
If the amount of airflow to reach a certain pressure is bigger that the turbo's can deliver then the boost will drop, I depends on the max rpm and volumetric efficiency of the 4.5 engine if it maxes out the GTSS's airflow.

But to achieve the same mass air flow as the rb26dett has @ 1 bar @ lets say 8000rpm there are less rpm or less boost requiered for the same result.

[R32 Combat]

The pistons should be done friday. DLC coated and ready to go.

Things should start picking up speed soon.

Roll on the next dyno session.

[R32 Combat]

Pistons are done and the block/pistons away at the M/C shop for boring/other work.

I'll have forgotten how it goes back together if this goes on much longer..

[R32 Combat]

Pics of the ACL piston(left) and the coated wiseco(right)






Spanners time