4 registered members (Golfpro, Dan79, Edinburgh, 1 invisible),
267
guests, and 1
spider. |
Key:
Admin,
Global Mod,
Mod
|
|
Forums69
Topics113,649
Posts1,341,480
Members1,820
|
Most Online731 Jan 14th, 2020
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313523
04/02/2012 01:08
04/02/2012 01:08
|
Joined: Feb 2007
Posts: 3,486 London Tan
technics
I need some sleep
|
I need some sleep
Joined: Feb 2007
Posts: 3,486
London Tan
|
Well, im sure you know the cold weather will definitely help with the feel of it and even the power figure.
Good luck, look forward to hearing the difference/result.
Now in the 400+ bhp club!
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313736
04/02/2012 21:23
04/02/2012 21:23
|
Marco20ValveT
Unregistered
|
Marco20ValveT
Unregistered
|
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313749
04/02/2012 22:09
04/02/2012 22:09
|
Biggenz
Unregistered
|
Biggenz
Unregistered
|
No news in this case seems like bad news!
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313808
05/02/2012 08:30
05/02/2012 08:30
|
Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
OP
Forum veteran
|
OP
Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
|
And we have a winner... Drum roll..... Technics Fuller story later, but as usual for me, it didn't go entirely to plan. Max power was 452, but this time at 1.5 bar, rather than the 1.7 bar used previously. The problem is that the injectors couldn't keep up with the turbo - they were at 100% duty by 6000rpm at 1.5 bar. I also suffered a lot of misfiring, so Leighton had to put some spare plugs in However, it is definitely faster, just not where we expected it to be. I reckon it's spooling roughly the same or ever so slightly later than my 2871 - it's hardly noticeable though - I can easily live with it. It's also reaching full boost slightly later, but only just. Again, it's not so bad that I'm bothered. However, the way it keeps on pulling is amazing - the bigger turbine wheel has freed the previous restriction and it just flies . MUCH stronger now after 5000rpm, all the way to the new 7500rpm redline. Leighton says the power is still rising at the redline, which is encouraging for future mapping sessions when the issues are sorted. Even on the 2871, the boost used to tail off towards the redline, but now the boost trace is impressively flat - a perfect 1.5 bar all the way to the rev limiter Can't wait to find some 630cc injectors and get it back to Bristol, but sadly, I'm going to have to wait - two to three months probably. Right, where's the kids' piggy banks....
|
|
|
Re: What bhp will it give....
[Re: ]
#1313838
05/02/2012 11:50
05/02/2012 11:50
|
tricky
Unregistered
|
tricky
Unregistered
|
Ahem... Not a bad prediction I'm not going to offer a figure but I will say this; It won't 'spool' any earlier, it will more than likely stay the same or show a positive boost a few hundred rpm later. The torque slope will be steeper although the peak won't move, from aprox 5.5k-6k rpm to redline will show a 15% gain more or less independant of the boost level run. But then I could be completelty wrong. Sounds like a good result so far, well done.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313842
05/02/2012 12:14
05/02/2012 12:14
|
Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
OP
Forum veteran
|
OP
Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
|
Yes - not bad at all!
I guess I was hoping for mid-range gains, and if I'd had a billet wheel on a GT2871, I reckon I'd have got them.
As it is, what I appear to have done is gone up a size on the turbo, and then removed the extra lag by speccing the billet compressor wheel.
I was difficult to test the car yesterday - I only got a handful of full-throttle squirts on the M5 before the snow got too bad and meant that ANY throttle was an issue.
However, do you remember the first time you drove a Coupe with a big turbo? That feeling of the world going into reverse just when a small turbo starts to run out of puff? Well, this feels similar. The GT2871 definitely dropped boost as the revs rose - probably as much to do with the hot side strangling it, rather then the turbo being unable to produce the boost. I ran it to the redline twice and while it feels no better OR worse below 5,000, it really takes off above this point.
The interesting point is one of traction - Leighton made a point of remarking that despite the weather, he didn't suffer any traction issues - rather than a thump in the back of a small turbo, it's more akin to that feeling you get from a plane when taking off - just a constant, relentless surge. TBH, it's nicer (and easier) to drive, although it probably doesn't feel quite as quick as some, simply because you don't get the big thump
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313858
05/02/2012 12:55
05/02/2012 12:55
|
group5lancia
Unregistered
|
group5lancia
Unregistered
|
Well done!
In your first post you said the car produced:
1.5bar 451bhp @ 6826rpm 368lbs/ft @ 6036rpm 402wheel power @ 6678rpm
1.7bar 457bhp @ 6575rpm 389lbs/ft @ 5702rpm 410wheel power @ 6482rpm
So I am a little surprised that the injectors couldn't provide enough fuel for more than 452BHP with the new turbo. I guess it indicates that the BSFC is more at higher RPM, which makes sense.
Having said that, wasn't it predictable before you got on the dyno that the 440cc injectors were going to be the limiting factor?
I normally size injectors for turbo engines based in a BSFC of 0.5 lbs/BHP/hr and 80% duty cycle - though some may think this is over-cautious. This makes the 440cc injectors good for 430BHP @ 100% duty cycle and just 345 BHP @ 80% duty cycle.
The 660cc injectors, on the same basis, should be good for 495 BHP @ 80% duty cycle - 617 BHP @ 100% so plenty of headroom.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313867
05/02/2012 13:21
05/02/2012 13:21
|
Joined: Feb 2007
Posts: 3,486 London Tan
technics
I need some sleep
|
I need some sleep
Joined: Feb 2007
Posts: 3,486
London Tan
|
Will be interesting to see in the near future with bigger injectors. I know what you mean about the extra pull from 5k onwards, it just doesnt give up, its a really nice strong pull all the way. Do I win a prize then?
Now in the 400+ bhp club!
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313868
05/02/2012 13:25
05/02/2012 13:25
|
group5lancia
Unregistered
|
group5lancia
Unregistered
|
I've had a suggestion that I ought to check my fuel pressure - the walbro is six or seven years old now and could be starting to lose its efficiency I had forgotten you had a 3.8 bar FPR. I'd say that checking fuel pressure would be a good idea; at 3.8 bar the 440cc injectors should be working at < 80% @ 452 BHP.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313871
05/02/2012 13:56
05/02/2012 13:56
|
group5lancia
Unregistered
|
group5lancia
Unregistered
|
I'll let Leighton comment, as I have no way of checking the fuel pressure, but I don't want to replace the fuel pump just to test the theory You/someone could check with a fuel pressure gauge before changing the pump? Perhaps it can be checked with a suitable reader via the OBD socket? I don't know.
Last edited by group5lancia; 05/02/2012 14:07.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313888
05/02/2012 15:00
05/02/2012 15:00
|
Joined: Dec 2005
Posts: 5,405 Castle Combe
Flea
Forum is my life
|
Forum is my life
Joined: Dec 2005
Posts: 5,405
Castle Combe
|
1.5barPower: 453bhp @ 7107rpm Torque: 342lbs/ft @ 6545rpm Wheel power: 399whp @ 7074rpm The injectors were pretty much 100% on the old turbo, but the problem we have with the new turbo is that the power is still climbing beyond where the 2871 had run out of puff. Nigel's injectors are 440-450cc, so at 3.8bar fuel pressure they will flow circa 490-500cc. This of course assumes the pressure remains constant, especially at high loads/rpms, which the Walbro 255 should be able to achieve up to around 500bhp. Using RC Engineering's injector calculator a BSFC of 0.55, we can see that 450 flywheel power would require a 460cc injector @ 3.8bar pressure running at 100% duty. On most 20vt engines, I do find 450bhp to be the flow limit of this particular fueling setup. In terms of max power from Nigel's turbo, well you can see on the graph that power is still climbing. I think we may see 460bhp @ 1.5bar, and perhaps closer to 470-480bhp @ 1.7bar if we can extend the limiter to around 7800rpm with the fuel delivery to match. It's a very smooth drive, more like a supercharger than a turbo. Very tractable with a frentic pace that only grows as you keep the throttle planted. It should be very kind to the transmission, and certainly driveable in many more conditions like yesterday.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1313965
05/02/2012 19:31
05/02/2012 19:31
|
Joined: Dec 2005
Posts: 5,405 Castle Combe
Flea
Forum is my life
|
Forum is my life
Joined: Dec 2005
Posts: 5,405
Castle Combe
|
I wouldn't bother Nigel, you would have to test it at full throttle at high rpms to get any real result. I have a fuel pressure kit which I do use for diagnosis, but as I said above, your horsepower correlates with 100% injector duty on your current setup so there is no suggestion at all that you have a fuel pressure issue, just need bigger injectors!
Angelo's car which pushed out 518bhp on a GTX, well even with the 630cc injectors it was struggling for fuel at the top end, so we installed a second inline pump. The Walbro 255 pumps are rated to approx 500bhp, so it was no surprise that a second pump was needed. We use twin pumps (and if required a larger external swirl pot) on all cars above 500bhp, especially in the race cars.
|
|
|
Re: What bhp will it give....
[Re: Nigel]
#1314089
06/02/2012 09:04
06/02/2012 09:04
|
Joined: Dec 2005
Posts: 286 Germany
Stichl
Making a profit
|
Making a profit
Joined: Dec 2005
Posts: 286
Germany
|
Hi Nigel, Wow – a good result! I assumed a maximum output of 450HP with your small hotside… It is clear for me, that the cold side (with new comp. wheel) is able to do much more boost – therefore the power graph is still climbing and probably this compressor could do now >500HP. But your small hot side won’t go much further… First evidence is this: 1.5bar 451bhp @ 6826rpm 368lbs/ft @ 6036rpm 402wheel power @ 6678rpm 1.7bar 457bhp @ 6575rpm 389lbs/ft @ 5702rpm 410wheel power @ 6482rpm Between 1,5Bar und 1,7Bar 6HP difference, only… I don’t think, that you will gain much more with a bigger fuel pump – maybe another 10HP, but not more. Your results show, what has been proven by GTX series with new billet wheels already. In most cases a little bit more lag, but much more top end. But exactly this “more top end” you cannot use because of your 0,64 T25… To your 3,8bar fuel regulator… unfortunately this regulator will effect in nothing in combination with your weak Walbro 255lph. Please have a look to these graphs regarding Walbro 255lph: http://www.autoperformanceengineering.com/html/fpspecs.htmlAt higher pressures the performance of this fuel pump will break down. Therefore it is senseless to heighten fuel pressure… this you can do with a Bosch 044 (which is still really strong at high pressures), but not with a weak Walbro… Sorry for my words – I wish you much luck in still getting a few HP… Juergen
20VT coupegrale 4x4
|
|
|
|