Ambient Temps. on the rollers?

[six appeal 53]

Was chatting to Vince today about the difference in BHP that ambient temps can make to the running of your VR on the rollers etc....

He was saying that a few degrees on the rollers can make all the difference, even as much as 6-10 BHP!

It started as my car was down on power even though it is now fitted with the shrick (although not mapped/chipped yet so knock sensors were holding the timing/power back )

Vince said that due to running my car later in the day the temp. have risen in the workshop enough to sap power from all the cars run later in the day!

He asked me to check out temps last time, and the results speak for themselves!

First time at Stealth. Modded but no shrick TEMP. 28 degrees

191.8 BHP(146.3 BHP)/ 184.7lb ft

Last RR day. Modded but no shrick TEMP. 6 degrees:

204.9 BHP(163.5BHP)/ 189.7lb ft

Todays RR day. Same mods, with Shrick TEMP. 15 degrees:

195.7 BHP(158.6BHP)/ 194.7lb ft

I was shocked to say the least! That a few degrees can make all the difference! You can see the Shrick works well though just from the torque figures!

Have you guys all found the same? Be interested to see your power to temp. ratios?

So there you have it , if your going out for a thrash, make sure it cold outside!

Ps. Can I go first on the rollers next time LOL!

[ Edited ]

[Eat this 2]

does that mean i can add 5 bhp to my total lol (i think only claire went on after me)

[ Edited Sun Oct 31 2004, 07:17PM ]

[six appeal 53]

LOL, no mate unfortunately not, I just want to see what everyone else had found when they compared there Temp/BHP ratios from last time!

[Pittuf 0]

didn't go last time so can't compare, but if I could squeeze more out of mine i'd have been even happier.....187 with just the exhuast for me :-)

[VR6Rich 3]

You will have to get there earlier then to go on first! :-)

I was first on and got 191.4bhp/183.6 lb ft with my BMC CDA and supersprint exhaust. Didnt go last time so cant compare.

[tandino 1]

Whats even more worrying is that my car made 157.8bhp at the wheels (the figure that really counts - not the pub figure 8) ) but the transmission loss on my car was only 30bhp whereas others were around the 40-45bhp mark - if you add this to my power at the wheels then its on the door of 200bhp at the crank......

Somethings not right/consistent with the run down figures

Pete.

[tommy 0]

stealth 31 10 04

Actual BHP @ Fly 184.5

@ Wheels 148.6

Torque 183.5

power loss (on 17" wheels) 35.2bhp

min amb. temp. 15 deg c

min amb. temp.18 deg c

barometric pressure 1011mb

stealth 22 02 04

Actual BHP @ Fly 186.3

@ Wheels 153.7

Torque 178.7

power loss(on 15" wheels) 34.7bhp

min amb. temp. 10 deg c

min amb. temp.10 deg c

barometric pressure 1007mb

[ Edited Sun Oct 31 2004, 11:04PM ]

[six appeal 53]

You will have to get there earlier then to go on first! :-)

I was first on and got 191.4bhp/183.6 lb ft with my BMC CDA and supersprint exhaust. Didnt go last time so cant compare.

What was the temp. there then Rich on your run?

[cliveyp 0]

i was close to the end and managed 184.8bhp and 177Ib/ft, but like many others, have nothing to compare it to, apart from my Corrado which managed 186bhp on a warmer day. But the golf feels quicker so that doesn't make complete sense!! lol

Tandino - i onlt had a transmission loss of 31 bhp too. Managed 154@wheels IIRC

[Eat this 2]

i went on after the r32 and got 198bhp 187lbft at 15-18 degrees and got 45!!! bhp tranny loss (im sure i wouldv cracked 200 if id got on early hehe) just decat axhaust and filter for me well happy to mix it with the schrick boys

[anorak 0]

I'm sure the temp. figures on my printout read;

min ambient - 15 degrees

max ambient - 45 degrees

(which is a little Sahara like - so Ill check tonight)

Not sure where the max ambient reading is taken from but I thought the corrected power (the one everybody quotes) took temperature and barometric pressure into account, giving a theoretical power figure at 10 degrees C and 1000mb pressure?

Vince did say at an earlier meet that unless the cars had sat switched off for an hour or so heat soak after a long drive could adversely affect the power output.

Mine went on after about an hour so I've got no complaints (other than the car trying to run on just air above 5000rpm! - but that's down to pulley greed. Sometimes less is more!))

I'll check that max temp figure later and edit this if I'm being a nobsack.

[anorak 0]

I'm bemused by the tranny losses as well.

Mine lost 58bhp apparently this time but just 41 in Feb.

Tracking? Binding brake pads?

As Pete says - it's what is at the wheels that matters on the road. Mine was almost 50bhp down on last time so I've booked a date with Vince !heart

[VR6Rich 3]

Power at flywheel : 191.4 Bhp

Power at wheels : 152.9 Bhp

Power loss : 38.8 Bhp

Torque : 183.6 lb ft

Min Ambient Temp : 15 Deg C

Max Ambient Temp : 18 Deg C

Barometric pressure : 1011 mb

This might be a stupid question but how is power loss calculated?

[Eat this 2]

its done by measurin the time it takes to wind down after the power run i think

i got very similer numbers to u rich

power at flywheel : 198.4 bhp

power at wheels : 152.2 bhp

power loss : 46.5 bhp (that 1 stings)

torque : 187.2 lb ft

min ambient temp : 15 deg c

max ambient temp : 18 deg c

barometric pressure : 1011 mb

i got fantastic crank power (considerin the mods) but also got quite high transmision loss

[anorak 0]

Just checked the sheet.

Max ambient temp was 45 degrees!

Mina did a run at Stealth in April 2003 and got a max temp of 58

Where are these measured? In the radiator?

[Pittuf 0]

Mine did a run after a super charged one, Vince said they put up the ambient temp to account for the super charger (don't ask me why), my power was coming out really high untill they put the temp back down to the 18 degrees I have on my sheet.

I lost 41.9bhp due to transmission and tyres, I know my fronts are sh*te (Do not get Falken 451's) and they are almost out of tread, also I know my tracking is out, I can't wait to get mine done when the car is in better condition :-)

[anorak 0]

Mine did a run after a super charged one' date=' Vince said they put up the ambient temp to account for the super charger (don't ask me why), my power was coming out really high untill they put the temp back down to the 18 degrees I have on my sheet.[/quote']

So the max ambient temp is an estimate by Vince then?

Sounds like he just adds 30 degrees to the n/a figures.

Bit hit and miss, don't you think?

[Eat this 2]

seems that way isnt it a set formula to calculate tranny loss??

[anorak 0]

Check out www.pumaracing.co.uk

15% is the accepted maximum transmission loss for front wheel drive cars

[VR6Rich 3]

15%?!? That means I should get 28.71 Bhp power loss!!! That is assuming its the same for all cars. :-(

[Eat this 2]

iv read it and im peeved now lol EVERY1 TAKE NO NOTICE OF FLYWHHEL BHP ONLY GO BY WHEEL BHP(which sends me flyin down the list grrr using his formulee i actually produced around 181bhp at the flywheel not 198 im goin for a cry now

[Eat this 2]

how is torque worked out then? is the torque figure measured at the wheels

[anorak 0]

I know what you mean - it's a bit deflating to be told you're power might be lower than the RR said but you can't argue with the maths on the Puma website.

There MUST be slight variations in transmission losses due to different tyres and bearings etc as well.

As for torque, I've posted what I understand about it on the 'escos' thread.

[eViL 0]

I think you are all looking into ambient temperatures far too seriously.. other than probably the first two, the others were pretty much in the same boat anyway.

Just be happy your car could go on the rollers..

I've spent a fortune and mine didn't get anywhere near em!!

[eViL 0]

*edit*

[ Edited Tue Nov 02 2004, 07:26PM ]