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I'm having a bit of a (re)think regarding turbos. The existing 3582's are OK but too slow coming on spool. I've seen some good information around the G25-660 turbos and I've decided to go that route, but before the engine goes back in I've got to consider if I'm likely to want to go further, later on.

With Built box, Quaife billet LSD, casings and all of the supporting fuelling I could fairly easily go for a larger engine (maybe 4.1litres) in future and make 1300-1400hp at the crank, but I really don't know whether the driveability at 1000/1100 would be that much worse with G30-770's versus G25-660's.

I know both Turbos are fairly new to the market but if anyone has any practical experience of either of these on VR38DETT engines I'd be really interested to hear about it. I'm guessing I'll make the same power at 1.8 bar on G30's with slightly later spool as I would at 2bar on G25's. I just don't want to be buying turbos again when I go large on the engine, the question is if the G30 will be any less driveable / will the difference be noticeable?

Cheers in advance!
Hi! You said you have changed your OEM differential to Quaife LSD and no need to limit torque anymore, so can you tell me how much OEM front differential can handle power/torque? If the casing is already changed to billet.

I have heard that the cast casing is the biggest problem but parts inside of it should handle well even bigger horsepowers, +1000bhp.

Or am I wrong?
 

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Discussion Starter #23
I'm going by the advice I've received that the Quaife LSD will be "enough" with the other drivetrain components I have to do mid 800lb ft's, but anything else is "unknown". I think that was to cover said person, so no complaints. The front casing does seem to be the thing that holds together most of the standard diffs and of course, less flex is less stress on the internals. I guess it's horses for courses as there will be many out there with standard internals and uprated casings, too.

I don't have any definitive markers here but I'm quite confident that this setup will hold a 850lb/ft (or maybe more) setup with 1000-1100hp and in my style of driving.

If something breaks I'll be going up towards the 2000hp mark with a billet race engine and might even be confident enough to drag the car, that's the summer target but I'd like to see how it drives at 1000hp, first.
 

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I have the quaife. Make a nice difference to the drive. I also went billet front diff housing as I wasn't prepared for the oem housing to break as on rare occasions it can take the block out. I run the Litchfield sport engine and needed to protect it.

The issue is often the big gear (pinion gear?) that breaks. I'm pretty sure this is reused, even when you go for a quaife.

If you opt to go 2000bhp, you'll pretty much be starting from scratch. I'd also say it will be terrible to drive on the road.
 

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Discussion Starter #25
Been in today to collect the RS6 and had a chat. I'm sticking with the G25's for this engine; we'll replace them if / when we need to go further - I think the spool will be worth it and there's not much point going to G30 (T3) for now.

Thanks for the advice on the diff, will be looking to do the casing and ask about the pinion gear, although I saw what they removed today and it's a complete unit that's been taken out...
 

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I have those G25’s also going in soon, so was thinking just to replace the billet casing and keeping oem internals. Was thinking that you get more benefits from Quaife if you are driving on the track and I’m planning only doing some 400m/half mile challenges. But do you guys think I still should go with Quaife?
Yes the pinion gear is the weak point and I haven’t found any stronger part with oem ratio. Linney said while ago that they are currently designing that.
 

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Discussion Starter #27
Re: " But do you guys think I still should go with Quaife? " I'll let you know once I've driven the car, hopefully this weekend.
 
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