GTR Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
540 Posts
Discussion Starter #1
I am slowly getting to know my GTR after being unsure about it last year. One thing that I'd really like to improve is the power delivery. I love the torque sweet spot between 3-5k revs on acceleration, but it annoys me that that feeling of shove falls away so quickly when there are still so many revs left. I'm realising that I love a flat torque curve and the feeling you get wringing every last horse from each gear up to the redline.

So my question. I am considering a Litchfield stage 4 with downpipes, but I am concerned that the drop off after 5k will be even more pronounced. Can a stage 4 be mapped to produce flat curve to the redline, at the expense of peak power?

If not, which bolt on turbos are the best to deliver stock or better response, whilst being able to deliver a solid wall of torque all the way to the redline? I'm considering Switzer P800 turbos as their graphs seem to deliver that, but would prefer a UK based offering for support purposes if possible?

I would be looking to stick to stock internals, so capping the torque.

Any advice or experiences?

Mart.
 

·
Registered
Joined
·
6,385 Posts
With stage 4 you will notice the torque difference further up in the revs, the stage 4 cars definitely show the power in the higher speeds, but off the mark your notice hardly any changes in fact it might even feel a tad lazier because of the higher fueling, I've had the same set up on my previous gtr from Litchfields and to be honest preferred my car as a stage3 because I had no smoke, over fueling and I basically wanted off the line response instead of top end torque. So if your after top endish torque then the stage 4 would be good hope this helps
 

·
Registered
Joined
·
321 Posts
For sure, you can map a car that has a peak of 600lbft torque falling away to 500lbft at red line so it's 500lbft all the way through, this would give you the flat torque curve that you are after but you would lose a mountain of torque and power and have a slower car:confused:

I don't suspect you mean this though, you would like that peak 600lbft that you are seeing at 4000 spread all the way along to 7000? Then you need bigger blowers that produce a lot more hp but then that peak 600lbft at 4000 is now 700lbft and you're back at square one, why not 700lbft from 4000-7000?

With a flat torque curve like that, you are effectively giving yourself an overall slower car, horsepower being a by product of torque.
 

·
Vendor
Joined
·
480 Posts

·
Registered
Joined
·
3,576 Posts
you cannot make torque without making power, with that in mind to make 600 lbft of torque at the hubs at 7000 rpm you will need approx 800 hub hp at that point, and approx 660 hub hp at 6500 rpm.

what you will need is a Litchfield stage 5 to maintain 600 lbft to near the limiter.
 

·
Registered
Joined
·
540 Posts
Discussion Starter #6
This is the Switzer P800 graph on stock internals. They've done over 100 of these with no issues on stock engines. This is the sort of linear torque that I'm looking for:

 

·
Registered
Joined
·
3,576 Posts
For sure, you can map a car that has a peak of 600lbft torque falling away to 500lbft at red line so it's 500lbft all the way through, this would give you the flat torque curve that you are after but you would lose a mountain of torque and power and have a slower car:confused:

I don't suspect you mean this though, you would like that peak 600lbft that you are seeing at 4000 spread all the way along to 7000? Then you need bigger blowers that produce a lot more hp but then that peak 600lbft at 4000 is now 700lbft and you're back at square one, why not 700lbft from 4000-7000?

With a flat torque curve like that, you are effectively giving yourself an overall slower car, horsepower being a by product of torque.

boost control will stop the high torque spikes low down, its only lots of boost and low revs that cause the spike
 

·
Registered
Joined
·
3,576 Posts
This is the Switzer P800 graph on stock internals. They've done over 100 of these with no issues on stock engines. This is the sort of linear torque that I'm looking for:


a Litchfield stage 5 should get you almost there, that's just the kind of power im looking for myself :)
 

·
Registered
Joined
·
540 Posts
Discussion Starter #9
I'm not that concerned with peak bhp. I'd rather have less peak power and more consistent torque throughout the rev range.
 

·
Registered
Joined
·
3,576 Posts
I'm not that concerned with peak bhp. I'd rather have less peak power and more consistent torque throughout the rev range.
its not a case of what youd rather have you cannot defy the mathematics, if you don't make over 800 peak hp at 7000 rpm then it wont make 600 lbft at that point, to make big torque at high revs takes a lot of hp.

divide your hp by rpm and times it by 5252 will give you your given torque at that rpm. torque and hp will always intersect at 5252 rpm on a correctly calibrated dyno plot, torque and hp are directly mathematically linked and this cannot be changed.
 

·
Premium Member
Joined
·
2,514 Posts
I have P800 turbos on a stock engine with stage 5 supporting mods but im affraid i havent been on a RR.

Ian Litchfield who fitted them and mapped the car on Ecuteck says they are good turbos and similar to his stage 5 turbos, Probably a little smaller and sit between his stage 4.5 and his stage 5s. They were afterall designed for a stock engine whereas litchfields stage 5s can go to 850 if needed on a built engine. These will max out at 760 ish on a dyno dynamics RR.

If you search for a project build by Ryan G he did a lot of testing on these turbos in the uk including several RR print outs which he showed on his thread..
 

·
Registered
Joined
·
540 Posts
Discussion Starter #12
Thanks for the feedback guys. Good point on the relationship between power and torque.

So, as I'm going to stick to stock internals, what's the cheapest turbo kit that will provide stock like response, whilst delivering the power to provide a flat torque curve of 650lb/ft all the way to the redline?

I'm a little aghast that turbo tuners are charging £2500 per turbo to hybridise the OEM units, when on any other car (Evos, Scoobs etc) you can get it done for under £1k per turbo. Smells a bit fishy!

Anyone recommend a turbo specialist that doesn't get greedy when they hear 'GTR' mentioned? I hate being ripped off!

Cheers,

Mart.
 

·
Registered
Joined
·
166 Posts
is the 800+bhp pushing the stock internals a little too far
everyone ive spoken to says not to exceed 650lbs of torque
 

·
Registered
Joined
·
540 Posts
Discussion Starter #14
As someone posted earlier, to deliver 650lbs of torque at the redline, you need to be making 800bhp. Power isn't what bends rods, torque does!
 

·
Registered
Joined
·
85 Posts
To make a flat torque curve of 650lb/ft all the way to the redline, you have to boost the engine around 1.2 bar below 4000rpm and gradually increase up to 1.4 bar at 7000rpm

Thanks for the feedback guys. Good point on the relationship between power and torque.

So, as I'm going to stick to stock internals, what's the cheapest turbo kit that will provide stock like response, whilst delivering the power to provide a flat torque curve of 650lb/ft all the way to the redline?

I'm a little aghast that turbo tuners are charging £2500 per turbo to hybridise the OEM units, when on any other car (Evos, Scoobs etc) you can get it done for under £1k per turbo. Smells a bit fishy!

Anyone recommend a turbo specialist that doesn't get greedy when they hear 'GTR' mentioned? I hate being ripped off!

Cheers,

Mart.
 

·
Registered
Joined
·
85 Posts
AFAIK the cheapest hybrid turbo that can get 800hp is AAM GT800 $4995 / GBP2950.
Indigo-GT stg 1 is cheaper GBP 2399 but only 720hp
 

·
Premium Member
Joined
·
2,514 Posts
To make a flat torque curve of 650lb/ft all the way to the redline, you have to boost the engine around 1.2 bar below 4000rpm and gradually increase up to 1.4 bar at 7000rpm
My stage 5 on stock engine is pushing a peak of 1.5 bar.
 

·
Vendor
Joined
·
480 Posts

·
Vendor
Joined
·
480 Posts
what does it run at 3-5k rpm ?
Knowing the size of those units, it'll be running around 1.15-1.2 bar to around 4400rpm then ramping up in a pretty straight line to a peak boost of 1.5 at the top, if they can hold more you tend to. The limitations of the turbos normally restrict the top end boost pressure available after 6200rpm.
 
1 - 20 of 20 Posts
Top