givemethebighammer
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| posted on 13/5/05 at 06:22 PM |
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Happy - Rolling road results
My car has just got back from Geoff Bloor's rolling road in Nottingham today. He said my jetting was right for the application, the car went in
running OK at the top end (3000rpm upwards) but was hesitating at lower rpm and was popping a little at idle.
Setup:
2.0L Zetec (standard)
twin weber 45 carbs
GEMS miniDLS ECU (with thottle pot)
34mm chokes
120 main jets
125 air correctors
F16 emulsion tubes
idle jets 65F8
pump jets 45
spill valves 45
Results:
162BHP at flywheel at 6065 rpm
117BHP at wheels
150 lbft torque at 4500 rpm
He basically remapped the ignition and reset the carbs up. He also mapped out the flat spot that was present at 2000 rpm.
Car is now much better to drive especially start / stop in queues and around town. Pulls away properly and accelerates well, I can't ask more
than that.
I would recommend Geoff to anyone in the East Midlands.
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Shogun969
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| posted on 13/5/05 at 07:04 PM |
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Rolling Road
Hi,
I too need to get my car set up properly and was also considering using Geoff Bloor Garages, could you tell me how long it took? did you book it in?
and if you dont mind what did it cost?
Thanks
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givemethebighammer
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| posted on 13/5/05 at 07:51 PM |
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I left the car with him overnight because he had not used the gemscom software to map my gems ecu before (I actually left him a laptop with all the
data cables etc to play with). He charges £48 per hour ex VAT. My session cost me around £80 inc VAT. I was expecting to pay more, because I had
convinced myself he would have to spend ages doing it. All depend on exactly what needs doing I guess (my jetting / chokes etc were already right so
he only needed to do some remapping of the ignition to get my car running right.)
give him a call and ask
0115 9821803
I'd never heard of him until the other week. I only used him because he was close to me and a friend recommended him to me. Thought I'd
give him a try and I'm glad I did.
PS - only booked it in at the start of this week, so no long waits.
[Edited on 13/5/05 by givemethebighammer]
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givemethebighammer
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| posted on 13/5/05 at 09:43 PM |
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Put like that Dave the loss does sound a lot. Not sure what I should have expected. But EP90 in the diff, soft tyres running 18psi ?
However like I said, the car is running loads better now and using less fuel so he must have set it up properly. I was never wanting the absolute max
BHP out of the engine (hence the 34mm chokes). I asked for better lower speed running and more torque through the midrange. The graphs he showed me
said that these had been achieved . After driving the car I can confirm that this was the case. If nothing else he has got the engine running
properly.
I may call and ask the possible reason for the loss.
Just had a quick search on the web and 10% - 35% seems to be the range of loss you should be looking at from the flywheel to the wheels. The most
power is lost in the tyres and is higher on a rolling road than on an actual road. Also the loss is only ever approximated. The important thing is
that if you make changes to the engine .i.e new cams etc. they are tested on the same rolling road so you can see the difference they have made.
search for "transmission power losses" on Blatchat http://www.blatchat.com , seems to have been discussed by various individuals.
[Edited on 13/5/05 by givemethebighammer]
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tks
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| posted on 14/5/05 at 01:31 PM |
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uhh??
wy would tyres eat BHP???
i think the main loss is in the differential..unit
the weight of the axels..etc..
i see it like a airco, it stops the engine running a bit..well in fact thats just what a diff does/ axles does...
they have mass and the mass. need to be rotated...
but 50HP loss sounds quet an bit..
it will mean a F1 Car 900bhp engine =>(20%) will los 180Hp in the drive train..
don't think sow...
for me it sounds to much..
how do they measure crank BHP???
TKS
The above comments are always meant to be from the above persons perspective.
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givemethebighammer
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| posted on 14/5/05 at 09:22 PM |
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I'm not expert on any of this stuff. The car went to the rolling road to sort out the problems with the low speed running and the "flat
spot". Quite why (if it's true) the most bhp is lost in the tyres I don't know. However this whole thing has got me interested
enough to do some reading. I guess what really happens is that they measure the BHP at the wheels then estimate how much should be at the flywheel ?
(I might well be wrong)
The most important thing is still the fact the car is now running right and goes as fast as I had expected it to given the components I built it
with.
what do numbers mean when you have a grin from ear to ear after beating some ar$3 in a porsche off the lights (OK so he hammers you 100 yards down the
road, but that's not the point !). His car £50K+, yours £5K and mostly from the scrapyard to boot !!!!
[Edited on 14/5/05 by givemethebighammer]
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NS Dev
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| posted on 15/5/05 at 07:44 AM |
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quote:
Originally posted by tks
wy would tyres eat BHP???
i think the main loss is in the differential..unit
the weight of the axels..etc..
TKS
Sorry, but I have to interject here!!!
The above statement is utter crap!!!
The tyres use by FAR the most of the power on a rolling road. If you only had 18psi in them then you will have high rolling losses. Remember that on
the rollers you have two convex contact patches, on the real road you only have one, flat one, so losses on the rolling road are more than double the
loss on the real road. The diff etc loses a small amount of power by comparison, and the gearbox very little indeed (unless it's an auto!)
You don't have to run on a rolling road for very long to overheat your tyres, which says something about the amount of power dissapating in
them!
The losses given do sound high, but as you said, the main thing is it's running right now!
From my point of view, my old opel manta (with a std XE 16v on throttle bodies etc, now in the grasser, but the same as the engine going in my
"locost" made 176hp @ wheels, and 204 hp flywheel, so that's 26hp loss, but I had my tyres up at 35psi for that run. I think if
yours had been the same pressure your losses would have been at least 8-10hp less.
Regarding the "how do you work out the losses" type questions, it is very simple indeed! You run the car up on the rollers, then when you
have finished, (still motoring at whatever speed you finished the run at) you dip the clutch and the rolling road computer "runs down" the
roadspeed, and the load cell on the torque arm on the rollers reads the reversed reaction caused by the braking effect of the losses in the
transmission and tyres. The computer knows the wheel rpm and the torque, and from the initial speed calibration it knows the car's gearing, so
it can calculate the hp loss and therefore the flywheel hp.
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givemethebighammer
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| posted on 15/5/05 at 07:08 PM |
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Gets more interesting by the minute. So in effect on the "real" road I probably have 140 BHP at the wheels ?. I always run the car with 18
psi in the tyres all round, so I might be losing power but the car sticks to the road (I guess the Yoko AO48R's also have something to do with
the grip as well !).
Anyway I took the car our for a run to the Tiger open day today. Taking the opportunity to overtake a line of traffic up a hill when a "crawler
lane" appeared, I left the bloke in the Audi behind me a long way back in my mirror (despite his efforts to go with me).
Thanks people .........roll on more hot dry days
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NS Dev
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| posted on 16/5/05 at 07:33 AM |
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quote:
Originally posted by Dave Ashurst
Hi Nat,
quote:
....so it can calculate the hp loss and therefore the flywheel hp.
How accurately?
regards
Dave
Hi Dave,
Pretty accurately to be honest. Everybody slags off the accuracy of rolling roads but set up correctly, calibrated regularly etc etc then absolute
accuracy is possible. However, a lot of systems may not have correction factors etc built in properly, but a modern well set up rolling road used
properly (power allowed to tail off at each rpm break point before a reading is recorded, to allow for heat soak etc) should be able to match a dyno
in terms of accuracy.
The problem is that there are so many more variables to control, that it is easy to be reading incorrectly and not know anything about it, whereas on
a dyno, as long as it is calibrated, it should read the right output!
Clear as mud!
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NS Dev
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| posted on 16/5/05 at 07:40 AM |
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quote:
Originally posted by givemethebighammer
Gets more interesting by the minute. So in effect on the "real" road I probably have 140 BHP at the wheels ?. I always run the car with 18
psi in the tyres all round, so I might be losing power but the car sticks to the road (I guess the Yoko AO48R's also have something to do with
the grip as well !).
Anyway I took the car our for a run to the Tiger open day today. Taking the opportunity to overtake a line of traffic up a hill when a "crawler
lane" appeared, I left the bloke in the Audi behind me a long way back in my mirror (despite his efforts to go with me).
Thanks people .........roll on more hot dry days
Probably along those lines power wise, but if it drives spot on then who cares! The tyre pressures are much less of a power waster on the real road
because you have much less sidewall distortion as you only have two flat contact patches, so don't worry about that one, set the tyres for
handling as you have!
Go and enjoy the sunny weather, if you feel like popping over to Barwell to give me some inspiration to get mine done then great!
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DarrenW
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| posted on 16/5/05 at 08:29 AM |
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quote:
Originally posted by givemethebighammer
Gets more interesting by the minute. So in effect on the "real" road I probably have 140 BHP at the wheels ?. I always run the car with 18
psi in the tyres all round, so I might be losing power but the car sticks to the road (I guess the Yoko AO48R's also have something to do with
the grip as well !).
Anyway I took the car our for a run to the Tiger open day today. Taking the opportunity to overtake a line of traffic up a hill when a "crawler
lane" appeared, I left the bloke in the Audi behind me a long way back in my mirror (despite his efforts to go with me).
Thanks people .........roll on more hot dry days
Well done GMTBH. Sounds really good. For me the best figure os Torque, this is what alloys you to use the power. As for BHP id rather have 120bhp on
the tarmac (sticky tyres etc) than 140bhp thro a hedge!!.
My understanding is that rolling roads are best as comparators. ie checking before and after powers etc to prove if improvements have been made. Like
all complex measuring instruments you have to understand how they work to understand the results. (I often have heated discussions about first off
samples that are tested on 2 different CMM's in 2 different countries etc - same deal as comparind rolling road reports from different cars on
different rollers)
I calculated i only need 125bhp and 550Kg car to have power to weight ratio of my old M3 Evo - ill be extremely happy with that. Instant adrenalin
rush - nice.
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