Gcg Xr6 Turbo Upgrade

[bcl]

We’re now getting into what I’d call the stage 4 area, let’s say 350-450rwwk.

The stock turbo will take you to around 380-420rwkw, assuming that you are running bigger IC, injectors (larger than 968’s), bigger exhaust, air intake, valve springs, upgraded rods, aftermarket plenum, modified fuel pump, upgraded brakes and transmission. Very few have gone here with the 4-speed trans, mostly people with T56.

This turbo upgrade, as a guide, may give you around 30-40rwkw, and get you up to 450rwkw. However, I agree with Robin, as you get from 420 to 450rwkw it will start to struggle, because of the exhaust limitations. That is where Robin’s car is now.

My view (Shane) is that if you want 450-500rwkw, you will need aftermarket cams plus custom manifold, plus extra fuel pump (or larger external pump). Cams are easy, and available, but custom exhaust manifolds is expensive, and this solution should include external wastegate.

At this stage go to another sized turbo, with split pulse entry turbine. You will suffer more lag, but that’s life.

500-650rwkw it’s another level of expense, with stronger rods and pistons again, fully sleeve the block, bigger IC, possibly 2 external fuel pumps, bigger air inlet, bigger turbo again, mandatory CV’s, and transmission headaches (heartaches).

Less drivability, more lag, but you’ll need ideally more revs to overcome the current low rev limits (part of the reason you need even stronger rods, when you look at piston speed).

Twin turbos are obviously an option, just more expense, and the fitment challenge around the limited space.

Beyond 650rwkw someone else can really answer, but destroking the block is a starting point for a different strategy, to make power through high rev capability.

Brian

[Chooka]

We’re now getting into what I’d call the stage 4 area, let’s say 350-450rwwk.

The stock turbo will take you to around 380-420rwkw, assuming that you are running bigger IC, injectors (larger than 968’s), bigger exhaust, air intake, valve springs, upgraded rods, aftermarket plenum, modified fuel pump, upgraded brakes and transmission. Very few have gone here with the 4-speed trans, mostly people with T56.

This turbo upgrade, as a guide, may give you around 30-40rwkw, and get you up to 450rwkw. However, I agree with Robin, as you get from 420 to 450rwkw it will start to struggle, because of the exhaust limitations. That is where Robin’s car is now.

My view (Shane) is that if you want 450-500rwkw, you will need aftermarket cams plus custom manifold, plus extra fuel pump (or larger external pump). Cams are easy, and available, but custom exhaust manifolds is expensive, and this solution should include external wastegate.

At this stage go to another sized turbo, with split pulse entry turbine. You will suffer more lag, but that’s life.

500-650rwkw it’s another level of expense, with stronger rods and pistons again, fully sleeve the block, bigger IC, possibly 2 external fuel pumps, bigger air inlet, bigger turbo again, mandatory CV’s, and transmission headaches (heartaches).

Less drivability, more lag, but you’ll need ideally more revs to overcome the current low rev limits (part of the reason you need even stronger rods, when you look at piston speed).

Twin turbos are obviously an option, just more expense, and the fitment challenge around the limited space.

Beyond 650rwkw someone else can really answer, but destroking the block is a starting point for a different strategy, to make power through high rev capability.

Brian

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Great informative post Brian

and good for the 2000 post too!!

Chooka

[F6 UTE]

Informative guys, thanks.

Brian/Robin/ Others, could you maybe detail usable rpm ranges for the power levels and 'stages' you describe. Rpm at which fullboost is obtained, and the rpm at which this is sustained to, torque levels etc especially with the different turbos??

I see alot of GTR motors make massive power, but up in the 7ooo-9ooo rpm range. Not suited to the I6's long stroke as Brian pointed out.

I find alot of guys get caught up in numbers. As with so many big numbers floating around, maybe it detracts from the driving experience as a whole, or leads to a different driving experience.

Cheers.

[youngy]

My turbo upgrade is basically using the same configuration as the GCG turbo, ie 66mm wheel, 0.7 AR comp cover, ported and profiled wastegate. I also have done some porting on the stock manifold to improve port flow matching.

So far the car makes about 440 rwkW. M6 XR6T is correct, that the existing GT3540 turbo is very well matched (comp wheel vs turbine wheel and housing sizes). Therefore bumping up the flow capability on the comp side only means it pushes the turbine side into the edge of it's performance envelope. ie the turbine side runs out of flow. Given you can't buy a larger turbine AR housing size, the gain is capped by the fact you run out of flow on the turbine side.

You can work around some of those issues by reducing backpressure in the manifold (ie like I have already done), and post turbine side (ie. freer flowing exhaust). This is why the next logical setup, like the Nizpro setup addresses these issues. ie. a larger turbine wheel and different manifold, to get the flow capability up on the turbine side as well as the compressor side.

What I have noticed, it that the new wheel is more efficient as the car can support more advance in timing (due to reduction in compressor outlet temp), and it seems to me that there is no appreciable reduction in low down response. The OEM turbo comes on extremely hard in the mid range when you boost it to around 18 PSI. With the upgrade the power is more linear, which means it's much more predictable and streetable. Before the upgrade I made about 400 rwkW but the car use to absolutely fry the tires and wouldn't get any grip. Now, the power comes on like you been run up the ars* by a runaway primemover and the car just hunches down and takes off. So the end result is it's much faster.

I don't think getting much more than 450 rwkW on pump fuel with this upgrade is going to be possible. The flow capability is about 10% up from stock. Given the factory turbo is good for 400 rwkW then 450 rwkW is about the max you could achieve.

Like I said earlier the turbine side is where things start to go off the rails with this upgrade. Associated with this is a difficulty in controlling the wastegate and associated boost properly when turbine side backpressure starts to skyrocket.

Here is the post I detailed some of the work on the turbo upgrade including the port matching of the OEM manifold which you might find useful.

http://www.fordxr6turbo.com/forum/index.ph...topic=26190&hl=

Cheers

Robin.

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Thanks robin that's exactly the kind of info I was after

[Lumpen]

<snip>...Less drivability, more lag...<snip>

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Interesting read Brian, I didn't want to quote the whole post just for this little tidbit.

I know you probably haven't driven your T that much at all, especially lately, however from the few video's I've seen, tractability doesn't seem to be THAT much of a problem. If anything traction would be the ultimate consideration?

I remember you saying somewhere that it felt like a big N/A six offboost, is the 'lag' and drivability troubles stem from the dramatic increase in power when the boost comes on or is there the old "Plant the foot, read a Tolstoy novel, wait for boost" kind of issue?

I can't even begin to imagine 5xxRWKW in a usable rev range of 4000rpm (?) would be like, though I imagine at WOT it would be like a lightswitch? Has drivability suffered dramatically in your opinion?

Interested to know the opinion of a high horsepower car set up for the track/street rather than a pretty impractical specialised drag car.

Cheers,

Lumpy

[bcl]

... my opinion

Often when we are discussing turbo changes (in the rex world where there are many turbo upgrade options) we talk in terms of x rpm lag. Rarely do you go to a bigger turbo without having more lag (there are exceptions).

The lag attributes depends on brand of turbo, the type of bearings used, wheel and turbine housings, shape, weight and configuration of the wheels. Generally, a change to the exhaust side will have more of an impact than the compressor side in terms of lag introduced. A simple change such a going to the next size up turbine housing (alone), may give 200-300 rpm lag, but allow 5-10% more power.

In this case Robin has stated that the power is a bit more linear. That is probably because it takes a bit longer to get the bigger compressor wheel going, yet it may still provide good air supply at lower rpm levels. In this case the exhaust side is unchanged, so there isn’t too much impact on spool-up (yet it still takes longer to hit max boost). Robin can report when max boost is achieved.

If you are going to use extractors they MUST be tuned to the car. I’ve seen guys bolt on extractors to turbo cars and make less power untuned, but more power tuned. The extractor pipe diameter is important, as it is on an n/a, as too big and you’ll get lag, but ideally should be mated to the turbo flow requirements, and in my opinion always with an external wastegate, for better control and higher exhaust flow potential. Extractors are good for better top end, but remember you will probably lose a bit of torque down low.

Bigger turbo, and you should look at useable rpm range. The Ford T I’d say is good for 2500-3000 rev range, say between 2500-3000 to 5500 revs. If you put in a larger turbo that introduces 500rpm lag (say), ideally you want to be able to shift your useable rpm to 6000revs at the top end. The more you shift more power into a narrower power band the more unstable and uncontrollable your car will be, so you need to be careful. I’ve put a bigger turbo on cars before, then in the interests of safety gone back to a smaller turbo.

With the bigger turbo I use now I expect it to not really get going until about 4000 revs, but maximum power is at around 7200 revs, with 7500 rev limit. So I still have around 3000 useable revs, which is a desirable result. Under 3500 revs it’s probably like an n/a, but the car has good natural torque. At this stage I don’t know when max boost is achieved.

As I’ve said before, whenever you add a new component it needs to be matched and assessed in relation to an overall solution.

Brian

[bcl]

I remember you saying somewhere that it felt like a big N/A six offboost, is the 'lag' and drivability troubles stem from the dramatic increase in power when the boost comes on or is there the old "Plant the foot, read a Tolstoy novel, wait for boost" kind of issue?

When I drove it (at around 510rwkw from memory) it had been detuned at 4000-5000 rpm, to protect the cv's. It made it feel like an 8 litre n/a, above 4000rpm, without the turbo rush...very strange.

[turbotom]

It made it feel like an 8 litre n/a /quote]

8 litre NA..... I could live with that!

tom

[Lumpen]

It made it feel like an 8 litre n/a

8 litre NA..... I could live with that!

tom

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Well I've got five so I'm more than happy to go half even

That must be alot of power Acceleration on that scale must be more accurate in the 160-260kmh bracket! Below that and wheelspin would be ridiculous.

Lumpy

[G6ET8U]

I remember Simon from Nizpro mentioning something about spinning the wheels in 4th at 200kph... on a dry road

Might a be a bit of a handful to drive in the wet...

Jack