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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!
 

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Discussion Starter #2
Also, does anyone have any advice about "no brainer" bits to change whilst the engine is out - I'm consdering uprated throttle bodies, as an example.
 

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I have some SVM 70mm TB's that I may have fitted next year; though one respected tuner warned there could be idle issues whereas another said no problem. It seems there are lots of US and Japanese cars with larger TB's but you also see standard TB's on big builds. King bearings, ARP bolts and Supertech valve guides could be done with the engine. As well as various braces. The gearbox and clutch will presumably be upgraded too?
 

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Is engine being built?

I had/have the linney Garret GT32’s fitted and found them to be an excellent medium between fast road spool and good torque curve further up.

Graph for comparison on 2 different cars but same turbo set up.

 

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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!
Dude 4.1 with 3582 would not be laggy, we expected no lag with my GT3584RS (which are for sale and will do over 1500whp)
 

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Is engine being built?

I had/have the linney Garret GT32’s fitted and found them to be an excellent medium between fast road spool and good torque curve further up.

Graph for comparison on 2 different cars but same turbo set up.

I can't make sense of the srd plot it's just a smooth torque curve like an na engine, I've just checked mine and the race fuel plot looks like this aswell where torque just keeps on climbing into higher rpms


But the JM run shows clearly full boost hit at 4500 rpm when motor hits peak torque first, I assume that one is a pump fuel run, and srd is race fuel run
 

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I’ve no idea ScoobySlayer tbh as the Jm graph is from my car and the SRD is from another car (courtesy of Dudesvr)

Think they’re the ideal fast road turbo imo and I was delighted with them, just need to sell them now
 

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I’ve no idea ScoobySlayer tbh as the Jm graph is from my car and the SRD is from another car (courtesy of Dudesvr)

Think they’re the ideal fast road turbo imo and I was delighted with them, just need to sell them now
They look good mate with full boost at 4500 rpm, my green one is full boost around 5400 rpm like gt37s I think garret equivelant, and my road car gt30s full boost by 3500 rpm is real responsive for upto around 960 hp
 

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You need to be clear on what you want tbh. If big power the 35s are great. But totally wasted at 1000bhp. If you want better response and to be able to run at 1000 ish with better response then the g25 660 will deliver the goods. But you'll never breach 1200/1400 bhp.

Whilst 1000bhp is a great number to quote, it's just a common power number nowadays. If you want to be really special then you need 1600 to 2000bhp.

So be clear on what you want and shoot for it. If it's sub 1200 on pump with good spool then those g25/ maybe g30s look sweet and will likely out spool most other turbos. I have the full efr 7673 kit which will do similar power on pump fuel so would be interested in the results if you pic a different turbo.

But you need the fuel system to match anything beyond 1050 bhp imo.
 

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Some Dynoplots Linney posted on Facebook a few days before.

All Plots on the same Dyno

G25_660

G30_770

G30_770_vs_EFR_6758
Well you wont make head nor tail of those as they are not scaled correctly, torque crosses hp at 5250 rpm they dont touch
 
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