The Triumph Dolomite Club - Discussion Forum

Hi does anyone know what the engine spec was for a group 1 dolly sprint?? I believe they pushed out around the 215 - 230 bhp mark. Thanks Tom

Did you ask this question recently on the fb page also?

Jeroen

Yes I did but no one come up with the answer

According the old specs a group one engine in its latest form was around 190hp i thought but for real it will be near 180 i think.

There are people who claim they have much more but that is measured on positive calibrated dynamometers or figures at the wheels using fantasy conversions to hp engine.

Jeroen (278hp)

Hi,

I think Gr1 is limited by exhaust and exhaust manifold. We also got suprisingly low power and torque ratings, although power band was wide. Maximum torque was under 190 Nm, being quite low figure for 4-valve head with BIG Webers. We were way under 180 hp.

Famous cylinder head design doesn't allow much variables for valve timing. Timing is always compromising between good intake for intake and bad for exhaust syndroma.

Mine is generally to that spec but runs 45 Dellortos rather than 48 Webers. With a block brace now fitted it will rev well, but the only time I ever put it on a dyno, one that is reckoned to run average type figures (rather than those of the flatteringly high variety), it gave a max of 147bhp at the rear wheels. It runs out of puff at high revs so whether the larger carbs would improve that I don't know.

The torque curve too was interesting and gave optimal gear change figures at around 7200 rpm for 1-2 and 2-3 with around 6600 for further changes using the overdrive. Using a 4.1 diff with LSD.

In the end it is all about lap times, not theoretical power. Dynos are really only useful for fine tuning (timing and carbs) so you are comparing one reading with another on the same dyno, not between different dyno machines.

Geoff

Original Broadspeed and Don Moore engines produced between 220 and 225 BHP on a fyno. The maximum ever seen by Broadspeed was 227 but the engine broke whilst on the dyno. The engines I produce have between 195 and 203 @ the wheels, do the maths and they are producing between 235 & 250 depending on what loss ratio you calculate. Modern technology and fuel has allowed this increase.

For the people who don't know a fyno it's a fantasy dyno giving fantasy figures.

A good sprint drive train has 15 to 20 hp loss but we regularly have this discussions on the Facebook page. So 200 at the wheels will be 220 not 250. Only on a fyno.

Jeroen.

You are quoting 278 BHP. Is that on a PITSNO???

For those that do not know, a PITSNO is a Pie in the sky Dyno!!!

Ken, yes i remember i did but that was calculated by using the standard dolomite facebook group from wheels to engine conversion factor. One of my std sprints with std cam and carbs does have 139 at the wheels and using the average factor used on that page, about 2, my engine should have 278hp.

I thought you knew it was a joke.

Jeroen

The accepted transmission losses used have always been 25% for helical gears and 20% for straight cut gears. Therfore 200 @ the wheels equates to 240 or 250 depending on gearbox used. Every RR I have used for nearly 50 years has used this calculation. Obviously all RRs vary, I could use one that gave me 250 at the wheels but I am a realist and know this is incorrect. I have been building Sprint engines since 1973, my engines are both quick and reliable, figures are for my use really but I do get asked what my engines produce so I give the nu
Bees I have. They are certainly not fantasy figures. As I said to start with, 203 @ the wheels, you do the maths!!!

I do believe your cars have on a dyno around 200hp at the wheels but there are many articles on the net of people who tested different cars, with auto trans or manual trans with the engine first on an engine dyno and then fitted the same engine in a car to test and have the real figures.

The average loss is about 15 percent with a good drivetrain. A little play in an universal joint or a worn wheelbearing will eat a few hp's. It also shows that it's different for any car and not lineair through the revs. At the highest torque there's the least loss and revving over the max torque towards the max hp figure the loss increases again.

When some one shout's my engines have this or that because at the wheels it has this so the engine must have that i cannot take those figures and that person serious. If you are an engine builder claiming figures for your engines then engine dyno test them so you know and can claim. Maybe you have very bad gearboxes and rearaxles and have 25% loss but then you know.

An average sprint box does eat 15hp.

Jeroen