was chatting in another post about my RR figures... and again the subject of my drag came up?

i have wondered about this b4 as it seems oddly high?

does anyone have any idea how to tackle and solve this prob? ive been told the drag should be around 20 25bhp? so i have a few loose horses i need to tame?

:orb_sad: i tend to have no luck with this tunning lark damit...

help!

Get a plane

Get a plane

? :orb_rolli

Short of removing your gearbox, I'm at loss as to what you can do.

It maybe the rolling road talking nonsense or it could be those wheels.

I am no expert on this though so you can probably write these statements off as utter borrax.

the rolling road was with the 18s i had?

on the actual road against my mates standard vrs and my brothers there is no doubt, breakie dinner and tea :orb_devil

the rolling road was at TSR

maybe worth a 2nd RR somewhere just to see how it matches up?

very annoying :orb_angry

The easiest way of getting more go is reduce weight. Have you considered this. Its cheap and easy to get started.

your big heavy wheels probably aren't helping

would the 18" tsw have casued that much extra drag n loss tho? if its usually 20ish its 30 odd horse running around lol

i could see the 20s causing abit but 25 30 bhp seems alot?

How was the engine power measured, did the RR plug into the ECU?

(I have not been on a RR for over 15 years, and that was with a non ECU motor).

The way they USED to work was they would give you the power @ the wheels and then an estimated flywheel figure (unless the engine was dyno run, it could only be an estimate)

I agree that your big (= heavy) wheels will be loosing you power.

How was the engine power measured, did the RR plug into the ECU?

(I have not been on a RR for over 15 years, and that was with a non ECU motor).

The way they USED to work was they would give you the power @ the wheels and then an estimated flywheel figure (unless the engine was dyno run, it could only be an estimate)

I agree that your big (= heavy) wheels will be loosing you power.

from what i can remember they just sat it in the rollers , strapped it down, and then booted it in 4th ... or sumin like that.

i dont think anything was plugged in

I get 35bhp drag if its any help.

Would a Seized brake caliper cause the extra drag?

That was the case when i used to use a RR the figures were purely from the rollers themselves.

If nothing is plugged into the ECU then the 225BHP figure is only an guesstimate.

The true figure (and IMO the only one that matters) is the 170 BHP @ the wheels.

It's a bit annoying when manufactures only quote the flywheel figures of an engine, because unless you are just buying just an engine the figures are pretty worthless.

The BHP @ the wheels is what matters.

All you can do to reduce the losses are by fitting straight cut gears (noisy and not as strong) that do not loose as much power through the transmission and lighter wheels.

Would a Seized brake caliper cause the extra drag?

Yes, anything that makes moving the car forward harder will hamper the figures.

Although a sticking caliper is pretty easy to spot, as that wheel will get covered in brake dust much quicker than the opposite one.

I've just replaced my front tyres. I had the choice of the cheaper 225's but opted for 205's due to having better straight line speed and giving less drag.

would the 18" tsw have casued that much extra drag n loss tho? if its usually 20ish its 30 odd horse running around lol

i could see the 20s causing abit but 25 30 bhp seems alot?

had actually assumed you were running the 20's (:eek:) when on the dyno

That was the case when i used to use a RR the figures were purely from the rollers themselves.

If nothing is plugged into the ECU then the 225BHP figure is only an guesstimate.

The true figure (and IMO the only one that matters) is the 170 BHP @ the wheels.

It's a bit annoying when manufactures only quote the flywheel figures of an engine, because unless you are just buying just an engine the figures are pretty worthless.

The BHP @ the wheels is what matters.

All you can do to reduce the losses are by fitting straight cut gears (noisy and not as strong) that do not loose as much power through the transmission and lighter wheels.

Mostly right, but straight-cut gears are stronger than helical-cut for a constant number of teeth and wheel size.

Thats what i was always led to believe, until i was proved wrong by Quaife.

have you thoguth about trying another set of rollers? as maybe that the resistance figure was bumped up to give higher engine power?

Thats what i was always led to believe, until i was proved wrong by Quaife.

I'd not normally argue with a source like that, but what they're saying is at odds with what everyone else who's made a statement says.

had actually assumed you were running the 20's (:eek:) when on the dyno

lol it was the 18s , i think the 1st thing is to maybe find some recomended accurate rollers, than go from there maybe.

if 35 has been seen as a drag could it maybe be a 20bhp error lol

i will also keep an eye on brake dust on the wheels? the car doesnt get massive amounts of use .... its only just creeping upto 10k

I'd not normally argue with a source like that, but what they're saying is at odds with what everyone else who's made a statement says.

aren't straight-cut gears themselves weaker than helical (something about smaller contact patch :confused:) but they put less stress on things like bearings and casings and make for a potentially stronger gearbox?

aren't straight-cut gears themselves weaker than helical (something about smaller contact patch :confused:) but they put less stress on things like bearings and casings and make for a potentially stronger gearbox?

I was told that the other way round; IE straight-cut are stronger despite an individual tooth of given cross-section and width being weaker, because the actual contact patch is the full length of the tooth (easy to believe if you've ever seen helical-cut gears in mesh: It's obvious that they don't make contact over their full length at any given time).

I could well be mis-remembering, but there was something about helical gears having two teeth (partly) engaged at the same time which meant less stress and less wear on each - the teeth themsleves aren't any stronger, but in practise the gears are?

I could well be mis-remembering, but there was something about helical gears having two teeth (partly) engaged at the same time which meant less stress and less wear on each - the teeth themsleves aren't any stronger, but in practise the gears are?

After looking at some pictures, I agree about the engagement points, but I think that's a flse argument, because the area of teeth that's in contact is smaller.

Gizmo, can you remember Quaiffe's argument in more detail?

According to various sources, the way to guesstimate engine power is to add 10 to wheel bhp then divide by 0.9 for a F.W.D. car the result is Approx engine power. In your case 170@wheels would work out at 200BHP @ flywheel so only 30 Bhp loss. Which seems reasonable.