Rolling road dyno, worth doing?

Francis, are you sure about that figure? Given the standard 15% deduction for powertrain loss, that means your car was making c. 280hp at the flywheel.....seems like a lot for an engine that's had nothing more done to it than a compression bump. Was there maybe some head work, different cams, etc. involved as well?
- Dave

 

Could also just be Dyno differences. We would constantly get comments from customers saying something like, "your dyno shows 400 HP but the shop that built the engine showed 420HP!" The type of dyno, the settings for the dyno (which can be "adjusted" to produce the results you WANT to produce!), and the atmospheric conditions on any given day can change the engine's HP readings. Inertial dynos produce different results than "real" dynos.

A rant follows:
A chassis dyno can produce different figures depending on the gearing/gear selected for the run, the weather, and the settings on the dyno. YES, if a shop wanted to sell you something, they could do the dyno run/produce a chart, tell you that if you add their "whatever" upgrade you will get more power and, even if no additional power is produced, a change in the dyno settings could produce a chart that shows it is! Chassis dyno info is only "accurate" if viewed as a relative thing and only when the SAME dyno/same settings is used. IOW, if the same dyno (same settings) shows 300 HP before and 350HP after, it's reasonable to say there is around 50 more HP. But it is NOT ACCURATE to say that the engine is producing 350HP because chassis dynos base their output on a series of settings/assumptions, including things like drivetrain loss. That loss varies based on the drivetrain configuration and the losses also change in different gears. Engine dynos are the way to go but, of course, most people are not going to pull an engine to do a dyno run!! Engine dynos are usually found in dedicated engine-building shops.

IOW, the only way a chassis dyno is really useful in a one-time test is if several of the same car models are tested that day. If two 328's for example, are tested in succession on the same dyno and one shows 237HP and the other 225, I'd say that the first one IS producing about 12 more HP. If the same two cars had been tested in two different cities with the same HP results I wouldn't be comfortable using the figures to compare the cars.

 

This.

Since the OP is based in the UK, if you really want to understand what the thing is for then take it to the Alps.

Everything will make a lot more sense from the ride & suspension to the gear ratios - and indeed, there is enough power too.

 

I have two separate readouts over a couple of years on different rolling roads showing similar figures. Happy to send them to you privately. Head and cams are factory original. Just high compression pistons.

 

There is a company.......here:

https://dkubus.com/?product=frankencis-dpr-controller-module

That has a setup that makes CIS programable through the WUR. This leaves the mechanical mass flow sensor in place (along with its flow restrictions) but in theory this would let you correct a buggered massflow signal caused by new cams to get the right mixture. I have never spoken to anyone who's used this setup so I don't know how well it works

If you change the intake to ITBs you would just remove the CIS and put it on a shelf. That will gain you about 20hp....and them you can add cams for another 20-30hp. This would be a $10k adventure and is reversible if that matters.

 

A dyno is no harder on the car than driving on the road as long as you are not changing anything! Hell...every time I drive my 308 it hits the redline many times!

Now, if you are doing any crazy tuning on it...things can happen! I have spent hundreds of hours on a DynoJet 248 tuning my old diesel drag truck. It eventually made 1800 hp and was fairly reliable. But I blew up a couple of motors on the dyno and several on the track before I got there!

some videos of it doing 900-1000 hp on the dyno

https://www.facebook.com/video.php?v=207976632561806

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https://www.facebook.com/video.php?v=2542518892379

 

Absolutely not necessary…was just confirming the number wasn’t fat-fingered or an artifact of “The older I get, the better I was Syndrome”.
Congrats on getting a great outcome from your piston swap.
- Dave

 

There was a race kit that was hi-comp pistons, bigger cams (P6) and I'm not sure what else that would bump the stock 240crank to around 280-290 crank or 230-240 at the wheel. But if the cams in that thing are stock 237 is an amazing result.

 

*IF* you can find an inlet manifold!

(Not everyone can just reach for the TIG! )