True TR6 CP BHP figure??

[PILKIE]

Hi all.

 

I've been trying to find out what a true at the wheels BHP figure for the TR6 150CP cars should be,as I know that figure was just advertising blarney!

And I cant see one in the brown bible,haynes or handbooks,only the CR one listed at 125bhp@5000rpm which again isnt really true!

Anyone know what the actual figures should be for the TR6pi,150bhp,CP series,uk car?

There are a few figures posted on the net,but not sure which is closest to being correct!

Just that I had mine on the rolling road at Malvern,"always meant to do it for the graphs in the album" and would like a figure to compare it to!

 

Cheers Dave

[Guest ntc]

Hi Dave

There are rolling roads and rolling roads you and others would not like to know the true figure

[marko]

Tell us what yours was Dave - don't be embarrassed.......

[PILKIE]

It doesnt really worry me what the true figure is,and I know its more like 110 maybe!

But how do we know if a rolling road or whoever operates it,is telling the truth?

Most of us,I doubt couldnt afford a session on one of the 100% reliable ones that probably cater for rally and race cars!

I suspect the factory figure is at the flywheel,on the bench no box or axle attached!

Go on then neil? what is it???

[Alec Pringle]

The figures from any 'rolling road' are almost meaningless in absolute terms, the chassis dynanometer (to give it a more accurate name) is an aid to tuning an engine, a comparator, which might give an approximation of power at the driving wheels but can at best offer a notional approximation of flywheel bhp by extrapolation - whereas an engine dynanometer, measuring flywheel output, is intended to offer a value in absolute terms. There are not that many engine specialists who can offer both engine and chassis dyno testing, but they are the only vaguely meaningful guides to an actual figure at the wheels.

 

Offhand I can't recall any volume car manufacturer quoting figures for either power or torque developed 'at the wheels', and nor can I think of an accepted standard relating to such figures.

 

Triumph figures were always a matter for conjecture prior to the CR series TR6, in so much as first 'gross' and later 'net' bhp figures were catalogued, but whether these were derived from measurement by the old SAE J245 and J1995 for gross, and subsequently J1349 for net, is debatable. To the best of my knowledge, Triumph did not specify the measurement standards. This changed when figures were quoted according to DIN 70020, which incidentally is nowadays replaced by 80/1269/EEC, in conjunction with ECE R24 and ISO 1585.

 

As has been discussed time and again on this Forum, the CP cars were generally not capable of achieving anything like 150bhp by any accepted measurement, not even SAE gross. The only way a CP PI engine in standard form could achieve 150bhp at the flywheel by DIN measurement was by very careful blueprinting and balancing - been there, done that, and believe me it was a damned expensive exercise.

 

I very much doubt that the average CP lump bettered 130bhp DIN, although the CR figure of 125bhp DIN wasn't far out by the standards of the time. Even a new CP TR6 wouldn't have achieved much over 100bhp at the wheels, if that - quality control wasn't exactly 100%. You'd be lucky on a 40 year-old engine to be seeing the ton on the rollers, if only because even V-Max doesn't equate to 101 octane leaded . . . .

 

 

Don't worry about it Dave, whatever any of our cars 'achieve' on the rollers at Malvern means sod all in absolute terms, only in comparison to other cars being tested at the time . . . . and even then, operator technique can significantly affect the 'result'.

 

Cheers,

 

Alec

[PILKIE]

The figures for mine only really confirmed what I already knew.

ie;

It goes very well and power delivery is very smooth!

Theres pinking under heavy load,ie,throttling up from 20mph in 3rd,4th!

Power dropping off at 5000rpm.

And running a little rich.

All things ive been meaning to get round to!

All things that really dont affect its normal day to day running!!

 

The figures they recorded were 129bhp at 5000rpm,was showing running a little rich at mid and top revs,power dropping off at about 5200rpm.

They said that if the ign was adjusted and the mix adjusted a bit it would probably be more like 135BHP at 5500rpm.

Smooth graph on the acceleration curve all the way up to 5000rpm.

Compared to other 6's tested that day,they said it was very good!

As you say Alec its an aid to tuning!

And just really a gimmick for the average joe public!

[scotty]

I presume you had just started up and was on full choke when you went to the rolling road ? I only ask 'cause there was a bit of smoke when you drove up . My 2 mates and me were sitting at the food stalls waiting for the bang . Thankfully it didnt

[Stag powered]

The figures for mine only really confirmed what I already knew.

ie;

It goes very well and power delivery is very smooth!

Theres pinking under heavy load,ie,throttling up from 20mph in 3rd,4th!

Power dropping off at 5000rpm.

And running a little rich.

All things ive been meaning to get round to!

All things that really dont affect its normal day to day running!!

 

The figures they recorded were 129bhp at 5000rpm,was showing running a little rich at mid and top revs,power dropping off at about 5200rpm.

They said that if the ign was adjusted and the mix adjusted a bit it would probably be more like 135BHP at 5500rpm.

Smooth graph on the acceleration curve all the way up to 5000rpm.

Compared to other 6's tested that day,they said it was very good!

As you say Alec its an aid to tuning!

And just really a gimmick for the average joe public!

 

I asked them a few years ago (actually I think it was the first year we had a rolling road) what a good 150bhp TR engine should do, and was told a good standard one should do about 125. I think the best figure I saw was 122 for a totaly standard TR5, but I also remember a 125 supposedly rebuilt to 150 spec making only 85bhp.....He was not a happy bunny. I was happy enough as my injected Stag powered TR250 made 165bhp. I was even happier on Saturday when it made 216bhp, and today I have just got back from a 450 mile round trip to devon and it has averaged 30mpg including rolling road time

129 bhp is a pretty good result, and at least you know what needs doing to it to put it right, which is information you will not get in a standard tune up!

Neil

[PILKIE]

I presume you had just started up and was on full choke when you went to the rolling road ? I only ask 'cause there was a bit of smoke when you drove up . My 2 mates and me were sitting at the food stalls waiting for the bang . Thankfully it didnt

 

 

It had been sat in Avon hall since sat morn,and always has a bit of smoke on 1st start up.

I know it runs a bit rich as it only ever takes 2 clicks of the choke to start it,then a minute or so for the pi to settle depending on how long its been standing!

Warmed it up before doing the rolling road,but I too was waiting for the bang,as it doesnt usually get the balls revved out of it!

[Mike Collins]

Dave, I'll show you the curves from mine next time we meet.

 

Like you a bit rich overall, a bit rich and smoke at the top end, a dip to rich around 2500, similar dip in the torque curve.

 

Peak of 140 around 5000 from memory, test continued to 6500!

 

An interesting excersize, as Alec says, good for relative numbers over a range of cars on the same day.

 

Mike.

[mccallm]

Hi

 

Just for comparison the two cars I watched on the rollers were a TR5 reaching 122bhp and a 6 that reached 124bhp.

 

Mine got 120 bhp last year at Malvern on carbs.

 

Mark

[rpurchon]

Hi

 

Just for comparison the two cars I watched on the rollers were a TR5 reaching 122bhp and a 6 that reached 124bhp.

 

Mine got 120 bhp last year at Malvern on carbs.

 

Mark

 

for more comparison i got 132 this year.running on su.

i noticed when he was inputing data. effiency was set at 70%.

so the guestimated flywheel figures are assuming 30% drivetrain losses.

richard

[jellison]

Hi

 

Just for comparison the two cars I watched on the rollers were a TR5 reaching 122bhp and a 6 that reached 124bhp.

 

Mine got 120 bhp last year at Malvern on carbs.

 

Mark

 

AWESOME. Mind sounds about right. I think a 150 would be about 135 and a 125 about 120. Torque not the best with these either but butter than the smaller engined competition at the time.

 

Std and most after market exhaust just kill thee engines power though (terrible things).

[ianc]

Sorry to be pedantic (well, not really!), but BHP = Brake Horse Power and should be measured on a rig with the engine driving a dynamometer. What is measured at the wheels is Horse Power (not BHP).

Clearly, there is a relationship between the two, because the engine drives through the gearbox, prop shaft, differential and drive shafts to the wheels and, via the tyres, onto the rolling road. All along this route, there are losses, which will be particular to the vehicle.

The important thing is that the rolling road can help one diagnose problems and can measure the improvement achieved by any remedial work and/or modifications. As Alec has said, comparisons are what matter (your car with other similar cars, your car before and after work has been done) and whether or not it performs well on the road or, if you are a competitor, on the track.

Ian Cornish

[Alec Pringle]

30% drivetrain losses for an IRS TR ? On which particular planet ?

 

As far as road IRS TRs are concerned, 20-22% losses might be acceptable for a well worn standard transmission, down to maybe 16% for a thoroughly sorted drivetrain - anything less requiring some trickshit competition engineering. Bear in mind that the more powerful the engine, the lower the proportion of power lost - given that some loss factors are fixed, others variable. Overdrive will sap an extra horse per thousand revs.

 

If the Malvern rolling road operator is applying a 30% loss factor to extrapolate flywheel estimates, I wouldn't personally place too much reliance on his figures. 130bhp claimed at the flywheel with 30% losses suggests 90 horses at the wheels, which to my way of thinking implies an actual flywheel output in the region of 110-115bhp, or a handful more if you have overdrive . . . . but nothing like 130bhp !!

 

Cheers,

 

Alec

[Andy Moltu]

I suspect the rolling road at Malvern was more than a tad generous in its readings.

 

I was surprised to see them taking some 6s up to 6500rpm - almost recklessly - I would suggest that a standard bottom end would be getting dangerously stressed at that. 6300 perhaps for a lightenened & balanced bottom end with decent con rod bolts. More than that is really steel bottom end territory.

[jellison]

I would never trust one of these Old style rollers that just give you the rwhp as you do not know your cars transmission and tyre losses, etc.

 

A modern state of the art set of rollers is the only way to go. Regularly calibrated these give absolute blob on accurate flywheel bhp numbers (precise run down braking calcs).

 

Only way to go.

 

mccallum - mine make exactly twice yours btw.

[david ferry]

Blimey Jon. That's a big number!

 

My TR3 was on a proper set of rollers on Monday morning and they showed that it produces 143.6 bhp at 5605 rpm.

 

Not bad for a road going 4 pot TR.

 

Clearly more than many 6 pot TR engines!

 

David

[Goswell]

Took mine to Cambridge Motor sports, some years back.

At the wheels was 100bhp with mixture running a bit weak.

They were able to make an adjustment to the metering unit which changed the mixture and gave me 105 bhp.

They felt that was normal for a standard CP engine.

[jellison]

Blimey Jon. That's a big number!

 

My TR3 was on a proper set of rollers on Monday morning and they showed that it produces 143.6 bhp at 5605 rpm.

 

Not bad for a road going 4 pot TR.

 

Clearly more than many 6 pot TR engines!

 

David

 

That is good for a nicely tuned TR 4 pot. Cool road car.

 

Mine is a tad tweeked though. My TR6 only lags slighty behind.

Edited August 13, 2010 by jellison

[Ashley James]

Sorry to be pedantic (well, not really!), but BHP = Brake Horse Power and should be measured on a rig with the engine driving a dynamometer. What is measured at the wheels is Horse Power (not BHP).

Clearly, there is a relationship between the two, because the engine drives through the gearbox, prop shaft, differential and drive shafts to the wheels and, via the tyres, onto the rolling road. All along this route, there are losses, which will be particular to the vehicle.

The important thing is that the rolling road can help one diagnose problems and can measure the improvement achieved by any remedial work and/or modifications. As Alec has said, comparisons are what matter (your car with other similar cars, your car before and after work has been done) and whether or not it performs well on the road or, if you are a competitor, on the track.

Ian Cornish

 

 

I agree with Ian and for those who'd like to go the whole hog and have their engine tested on a dynamometer by an expert I'd suggest Stanton Motorsports near Membury. He maintains a few TRs and also lots of racing 2 Litre Bristol engines. He's a properly qualified engineer who designs camshafts and tunes engines for an impressive array of customers and he's nice, helpful and approachable.

 

Ash