Rolling Road Session

[james28 0]

Just back from a rolling road session last time 14 years ago the car made just over 200 hp

today with the new piper cross filters the car made 193bhp and slightly more without so not bad it works out to 1bhp lost over the last 14 years so happy

[rallyeash 155]

what engines that? rolling roads can very quite alot so unless you went back to the same one can't really tell if its lost anything

[james28 0]

yes its lost some over the years went to same place 14 years ago lol but no doubt there software and rollers have been changes countless times since then

[rallyeash 155]

engine?

[james28 0]

sorry its an alloy block mi

big valve head

rally cams

on carbs

[rallyeash 155]

not a a bad result then, on mapped ignition or still dizzy?

[james28 0]

still on dizzy

[PVFCpug 6]

RR no matter which on has to be taken with a significant pich of salt! Lots more important is how it feels. If you smile like a chesire cat as you accelerate and come on cam then it's doing what it's meant to.

 

I had mine done (very similar spec to yours by the sounds of it)

 

Cat Cam 283's

Standard Head

Twin 45 Webers

Custom Manifold, Exhaust DES Special

Omex ECU

Dry Sump Set-up

 

In March I went to Hi Tec Motorsport in Walsall, long and well known Carb specialist who tunes some serious Mille Miglia (i think) classics.

 

Measured

 

208BHP, 145 lb/ft

 

 

Two month later at Pro Sport in Stockport

 

180BHP, 175lb/ft

 

 

you work it out. All of a sudden you feel gutted that your engines down, but hold on it doesnt feel any different!

 

Lost 28BHP and gained 30lb/ft.

 

Now I know you cannot get them sort of torque figures out of an alloy MI so if anything it just shows you cannot realy trust any of them. There are so many variables that can effect a run you never get the same rsult consistently.

[Baz 421]

IMO if you're going to care/argue/believe any power figures from a dyno, to ANY extent, you need to research on what a Dynamometer actually does and how the different types work. It's not easy and tbh i struggle to understand it all myself! But, i have experience in operating a RR and have done a lot of research into it.

 

Why do you think that most operators of older RR's ask you if you have an 'expected' figure?? It's for a reason, not just for fun!

 

RR Power figures are a minefield, basically because traditionally anyway, they're corruptable by changing many controllable factors that the operator can do on purpose should they choose or simply by human error, not to mention age, wear & tear etc. Hence why companies can make such wild claims on the tuning work they sell, because they have their trusty RR that they can 'prove' this on. You only have to think of 2 well known three-lettered companies that specialise in PSA cars that constantly give OTT figures for their different levels or 'stages' (another stupid label, a pet hate of mine) of tune, that often never actually live up to it elsewhere.

 

But my opinion is, after doing LOTS of research as i say and playing with a few, for a good reason, is that i'd only trust Dyno Dynamics machines as being anywhere near close to actual power figures.

 

Saying that though to a degree, figures are pointless anyway, you cannot race a rolling road...! There is always differing factors, even if 2 runs are done on the same dyno on the same day! Barometric pressures, engine temps, just to name a few!

 

DD rollers are fast becoming the industry standard for many reasons. They're the only company that for so long have plowed money back into researching how to make their products better, more reliable and therefore realistic. For starters they have a better way of strapping the car down to limit the car's pressure on the rollers or affecting the suspension compression; ever been to or heard of an RR day where they've had people sitting on the car to hold it down?!! PMSL! The DD rollers uses a technique where the more the car tries to climb out of the rollers due to the power being exerted that has to go somewhere, the more it actually pulls the wheels/car into the rollers themselves if you follow what i mean, maintaining the optimum contact, which is why you won't get a car trying to climb out of a DD Dyno. They also don't use the same flawed system that many do to calculate fly-figures from 'run downs', losses in the transmission accounting for the differences, not realistic! It's also well proven that their figures are within a very small margin/percentage of what the engine dyno figures are, again a result of alot of continued research in their area of expertise! In Shoot-out mode they cannot be messed with and are all set to the same standard settings, which is fast becoming the standard. At least so that they're all used in the same way themselves, so one set of figures from DD rollers can be as comparible as possible to another.

 

Anyway, it's late/early and i've babbled enough! And no i'm not employed by DD, but i should be sponsored or something... Mike...!!

 

 

Result doesn't look too bad, do you know what cams they are James? It's peaking fairly lower down the rev-range to what would be expected from massively wild cams. Not sure if you've said also, but does it have a rev limiter?

 

But never the less, as Adrian says, it's more about whether you're happy with it, that's all that really matters irrespective of some numbers on a piece of paper!

Edited June 8, 2011 by Baz

[james28 0]

Cheers for the feedback as regards to the dyno rolling road i only really wanted to take it to get the carbs set up correctly in the first place it needed new filters and 2 of the jets were slightly larger than the other 2 so they were replaced.After the session on the way home honestly i felt slightly disapointed as the car drove the same as when it went there its hesitant at around 3.5k revs.I was told that its having 48 webbers on there and that on full throttle is when you get the best out of them no just at cruising speed.As for the cams they are group a rally cams and the rev limited has been removed.

[Sandy 191]

I would not put that much faith in Dyno Dynamics personally, we've seen some bizarre results from engines we've done on our engine dyno and rollers, that have gone to DD rollers and shown totally inexplicable results... A Saxo for example that showed less peak on DD rollers "at the flywheel" in a shoot out, than we saw two weeks earlier, at the wheels on correctly calibrated Sun RAMXII rollers, with no drop in perceived performance?!! The most consistent "flywheel" results I've seen from engine dyno to rollers, have been with MaHa LPS3000, but I still take it with caution; the rollers many lampoon for unrealistic loss figures. Loss figures are pretty much an arbitary figure anyway, because the "at the wheels" power isn't literal, the way it's calculated is easily corrupted, quite dramatically.

 

All rolling roads estimate figures using a range of methods to evaluate the variables and so the results will vary on each and can be representative of real flywheel figures in some cases, but not others. If there's one thing I've learnt over the last few years of using them, rolling roads are not to be taken as a reliable power measuring tool. You can usually get a good idea, when you do as many similar engines in similar cars as we do, but you have to get it on an engine dyno if you want the truth.

[No Guts No Glory 1]

Variables such as temp/humidity, uneven tyre pressures, tracking and how hard they tie down the vehical all have an affect. Just use the same RR and keep the variables constant. Mikeanics for now 9 years.....

 

Breaking 200bhp with the 8v dizzy Is very good going! However mapped ignition would bring on more torque and remove the flat spots.