Turbo Buffs in here please :)

eidolon · 13 Mar 2006 at 16:53

Simon said:
No question it will be strong enough, it just will be out of its efficiency meaning extra heating of the compressed air, especially on a bigger engine.

The T2 on the Fiesta turbos isn't much good for over 170hp and most t25s are only goof dor 200-220.

18PSI was found to be where the turbo stopped making extra power and just making hot air. Quite a few people tried 19/20PSI but made zero gains so it seems that 18PSI was the max that the turbo could flow before turning into a hairdryer/flamethrower

Simon said:
How much power was your R5 running out of interest?

I had it rolling road tested a few times when I was running 18PSI and got wildly varying results from 150BHP to 170BHP (different rollers each time so it could be down to that)

eidolon · 13 Mar 2006 at 16:55

Bear said:
Isnt it the case the smaller the engine, the higher the boost you can run. 18psi in a 1.4 isnt the same 18psi in a larger engine.

Not sure to be honest. 18PSI is widely regarded as the max safe amount you can run on a standard Revision 3 MR2 turbo too so I guess it's more down to how good the standard intercooler/fuelling etc. is

Simon · 13 Mar 2006 at 16:59

eidolon said:
I had it rolling road tested a few times when I was running 18PSI and got wildly varying results from 150BHP to 170BHP (different rollers each time so it could be down to that)

Yeah 170hp rang a bell for a typical T2. Turbos tend to be power limited rather than boost limited, 12psi on a engine thats flows more air (bigger cc) will be pushing the turbo just as hard.

As said you get to a point where you make no more power, same with the Rover turbos, 12 to 14psi makes no difference to power. Bumps up the torque curve slightly though. This is due to the turbo rather than engine

Trickle · 13 Mar 2006 at 17:11

What psi is the limit where the injectors are maxed out for this volvo? Or should I say where abouts on a non modded volvo do your injectors pass 100% duty roughly speaking as you start to increase air pumped into the engine - all things being equal etc.

On a disposable car such as this I would push the psi up until just before I hit the (owners club assumed) limit in the following three areas:

Engine internals estimated limit with some empirical reliabilty feedback;
Turbos empiracal estimated limit;
PSI roughly equating to 100% injector duty cycle at max bhp.

Are there any other known limits on this model? Gearbox, fuel pump, ECU's airflow meter? That sort of thing.

Malt_Vinegar · 13 Mar 2006 at 17:41

Trickle said:
What psi is the limit where the injectors are maxed out for this volvo? Or should I say where abouts on a non modded volvo do your injectors pass 100% duty roughly speaking as you start to increase air pumped into the engine - all things being equal etc.

On a disposable car such as this I would push the psi up until just before I hit the (owners club assumed) limit in the following three areas:

Engine internals estimated limit with some empirical reliabilty feedback;

Turbos empiracal estimated limit;

PSI roughly equating to 100% injector duty cycle at max bhp.

Are there any other known limits on this model? Gearbox, fuel pump, ECU's airflow meter? That sort of thing.

170bhp is said to be safe when re-mapped with the "Rich mod" Not just a re-map, but also increased boost (Some people have been running for 50k+ with the mod and no problems)

I think the 14psi limit is down to the injectors being maxed, there are people who have taken it higher but have had to do fuel system mods, including changing injectors. Some people go for different turbos to allow

Point 3 - ya lost me there guv

(I did mention the Auto gearbox issues earlier)

Im taking this from more knowledgable people on the volvo 480 forum, so dont assume im getting that all 100% correct!

Bear · 13 Mar 2006 at 17:55

eidolon said:
Not sure to be honest. 18PSI is widely regarded as the max safe amount you can run on a standard Revision 3 MR2 turbo too so I guess it's more down to how good the standard intercooler/fuelling etc. is

I could be wrong but with a turbo, its a matter of how fast it spins to shift a certain amount of air that dictates its efficiency range. At the point where its spins up so fast its heating up the air to much for the intercooler to cope, its getting pointless going any further.

So with a big engine, it has to shift a lot of air to fill up those cylinders. Therefore to fill that engine up with a certain amount of boost, the turbo has to spin up that turbo rather quickly as it has to shift a lot of air.

Now with the same turbo, a small engine has to shift a smaller amount of air to fill the cylinders to meet the same boost level. Therefore the turbo doesnt need to spin up so much for the same psi and as such it can run higher boost as a result compared to the larger engine.

Its all about how fast the turbo has to spin up to shift a certain amount of air to meet a set pressure.

Simon · 13 Mar 2006 at 20:06

Trickle said:
[*]PSI roughly equating to 100% injector duty cycle at max bhp.[/list]

Are there any other known limits on this model? Gearbox, fuel pump, ECU's airflow meter? That sort of thing.

You never want 100% duty, indeed anything over 90% duty is pushing it as you will start to overheat the injector coils.

Trickle · 13 Mar 2006 at 21:19

Agreed. They would be open all the time (assuming you could theoretically remain at 100% power constantly) and overheat as you say.

I've heard it said that while some people run more boost than the injectors can handle and seemingly get away with it (in the short term), they are probably leaning the engine out full on at high revs.

Bear · 13 Mar 2006 at 21:32

Trickle said:
I've heard it said that while some people run more boost than the injectors can handle and seemingly get away with it (in the short term), they are probably leaning the engine out full on at high revs.

You can get round the max flow of the injectors by upping the fuel pressure but its not a good way of tuning and a bit of a bodge IMO.

Simon · 13 Mar 2006 at 23:18

Bear said:
You can get round the max flow of the injectors by upping the fuel pressure but its not a good way of tuning and a bit of a bodge IMO.

Agreed in most cases as it results in the whole fuel map becoming richer, part throttle cruise, economy and throttle response will suffer.

Bumping up the pressure before a remap can increase flow rates but then combined with boost your fuel pump is working harder and the flow rate will actually reduce. 3 > 3.5 bar will take injectors from 380cc to 420cc, but with 1.5bar of boost, the pump will be running at 5 bar, obviously your going to get into problems then with maintaining pressure. :eek:

What is this 'rich mod' does it involve a Vice and a fuel pressure regulator ?

Malt_Vinegar · 14 Mar 2006 at 00:12

Simon said:
What is this 'rich mod' does it involve a Vice and a fuel pressure regulator ?

Its just the nick name given to a re-map done by a bloke called richard. Hes the only bloke in the UK who mods 480s like this