I had the view of Andy's Spec C in my rear view mirror for a good five minutes or more. :D

Caught me rather rapidly and I couldn't pull away from it, though.

:lol1:
It turns out all you flippin' road mappers go running off to "borrow" dynos every five minutes! It's like the man who runs the AA classes keeping a nip in his hip flask..

I've read a fair few comments now on forums across the pond and Australia/NZ from mappers that tune all sorts of turbocharged Jap machinery. They say that often when straight after a session on the rollers they log their cars on the street they see higher boost and engine loads than they did on the rollers, and certainly when going through the gears.

It happens in this country too ;)

lol

And we know how to deal with all of it... and you'll still use a dyno when it suits your purpose..
Yah boo sucks.. :lol1:

Is there a RR Dyno v Wheel Hub Dyno thread yet :lol1:

Yes, and we won that too...

fpmsl

Is there any argument you haven't won?

My customer is usually the dude with the dyno.....


I'll have some of what he's drinking lol :lol:

It's all that salty air.....That's two of you working near the sea for too long. :lol1:

So far, no one has managed in this thread or any other about dynos to satisfactorily explain the discrepancies I mentioned in post #414.

I've just finished some custom code for the GTR ECU to add gear compensation to the boost control. I'm just waiting for an email from a tuner that tries it on the dyno and wonders why it behaves oddly when it is beautiful on the road...

A good read, but stick the kettle on first :lol1:

https://www.scoobynet.com/general-te...ling-road.html

John, you know as well as I do that discrepancy is the name of the game when you get out on the public highway trying to map high performance turbo cars. I don't even know where to start about how many potential problems there are when making a commitment to tune someones car regardless of actual conditions. If you turn up on the day with your laptop, you have to perform, rather than making the decision that safety considerations take priority, never mind the host of parameter variations with gradients, road surfaces, climate etc. We've all heard of some lurid accidents or near misses while mapping, understandably nobody wants to talk about that. If you're off to Bruntingthorpe, that's fine, but I don't fancy sitting head down with a laptop while somebody you don't know is holding their foot down "just that little bit more"
Martyn and I work as a team, we don't expect the customer to be taking that kind of risk.
We all appreciate your undoubted ability and I'm sure that you'd be decent enough to warn tuners of the quirks of the boost control system you've designed. :thumb:

John, I think to provide satisfactory answers to your question on discrepancies you would have to get a dyno manufacturer on to answer that one.

Seeing as you can get differences in the "environment" the engine is running in from one day to the next, or even from one gear to the next, I don't see the problem in taking the dyno environment as one that it's possible to base a map from. However you must know the difference, and if you can easily and fairly accurately translate it to the road, then it's a pretty good way to do. The biggest single problem I've encountered is higher than normal charge temp, which means your dyno map can be centred around a 35ºC charge temp (for example) and common corrections to make the map applicable for say 10ºC are way way out. You really need to be able to check the map in a wider range of temperatures.

However you can do this, simple things like fan placement and timing (of runs and cooling periods) allow a wider range, but simply ignoring these changes causes problems for sure.

I think John's view is slightly skewed because he has perhaps made the road work better for him than most, but effort put into making the dyno work can pay dividends.

But after all that, if it's not right on the road, it's not right, end of story.

Amen.

What would a dyno manufacturer know about the air, or the engine that we don't?

It's not a question of why, it's a question of what to do about?!

Won't argue with any of that. Of course you need to monitor everything that needs to be monitored, it's why we data log on the dyno as well as a matter of course. There's been plenty of occasions when charge temp turns out to be an issue on the road/track as well. I can't imagine what makes people think that it wouldn't be! The map has to be able to take the heat as well as the mapper. :)

In which case with mappers knowing as much as dyno manufaturers why aren't mappers designing dynos that better suit the application.

1. Designing and ultimately manufacturing a dyno costs lots of money
2. Creating a dyno manufacturing business costs even more money
3. Mappers are mappers, and most of them don't want to build dynos, they want to map cars
4. The biggest single thing is the software development
5. The second biggest thing is the dyno cell, and a temperature controlled dyno cell (with refrigeration) costs even more money than a dyno!
6. It's cheaper to buy an engine dyno and more closely control the load and temperature, but it will change again in the car, and you can't expect every mapping customer to remove their engine for mapping!

The list goes on I'm sure.

So if you could drive on a dyno as you would on the road going through all the gears as you normally would, sample the outside temp/humidity/wind speed and recreate that in-house with refrigeration/air-conditioning and fans that flow more air as the car goes quicker and all that, could you completely map a car on that dyno and expect it to drive as if it were road mapped?

Isn't that tantamount to mapping on the road? In which case, why not just map on the road (bearing in mind safety considerations of course)?

Something like that yes.

However, even a dyno typically of the current installations of most tuners CAN in my opinion be used to get very close to a perfect map for the road, if used with the benefit of intelligence and some experience.

Because on the road, you can't just fire a new number in for cam advance and whilst at a steady speed and watch the power jump up 30hp, or even 3hp! Cam maps is one area where the dyno wins hands down, especially if you're using a smart ECU with full time close loop lambda and knock! ;)

The quite ridiculous inference there is that just because it was mapped "on the road," it must therefore be better in some way?
Tosh mate.. If you really wanted to make as good a job of it as possible, you'd take it to a test track, where the freedom to thoroughly check out all eventualities without interference would pay dividends. Mapping at high load settings thoroughly on a public road just isn't on, and you all know it.
Let's start a debate about test track mapping, and we'll see how many of you can actually run a business on that basis.
We do track test, we help to run a classic touring car amongst other projects. Funnily enough his charge temp problems are on the track, rather than the dyno! we've had to reduce the cooling to simulate the effect in actual race conditions.

You've answered your question haven't you?

IF?!?! there was such a (hypothetical) dyno available, then surely the 'Holy Grail' would be hit upon?! Ergo, taking into account ALL loads/road-replicated conditions... BUT... in a controlled environment/complete safety (aside from the car driving off the rollers!) AND without 'driver input' variables!(?)

Alan, wind your neck in!! I asked a perfectly legitimate question and wasn't inferring anything. Paul answered that question and his answer was good enough for me, thanks.

Totally agree :thumb:

Or breaking speed limits on any highway or byway while mapping. Something you've never ever done no doubt ;)


I disagree. I think under the right circumstances, and certainly with OS mapping this could work business wise. For the the right mapper this would a real feather in the cap and offer customers a safe no limits environment with which to get the best from their car. A distinct advantage over competitors and cracking marketing tool.


You simulated the proper hammering a race car gets and the whole raft of temps normally seen under race conditions?

Sorry, but mapping in "real world/road blah" is consistently touted as being better when we all know it ain't necessarily so.

I was testing a car on the road not 20 minutes ago! The difference is I'm not 250 miles from home and having to run on unfamiliar roads with a time deadline.

We have been track testing for decades when appropriate, you're preaching to the converted.

Of course not! but we did want to check the mapping under the high charge temp conditions we knew he'd encounter. The intercooler is restricted under the regs. It's just ironic, when the usual gripe is centered around the notion of high charge temps automatically when dyno testing.
Addendum - this is a classic situation where you need a dyno! race car, race tyres, not road legal, and the track is miles away. Please don't tell me I should have road mapped it...:lol1:

This is not just limited to JB and his GTR's. Many of the OEM and aftermarket Subaru ECU's have per gear boost control. This can be set up on the road to make a faster accelerating car by tailoring the wastegate and boost settings appropriate to the actual acceleration rate of any particular gear.
This cannot be evaluated on the rollers, in fact as previously mentioned you are likely to get an ill performing car, either not achieving boost target or overboosting and therefore showing either poor numbers or an irregular graph.
(ideal opportunity to recommend a remap though ;) )

This goes some way to explaining why a car showing lower numbers on the rollers can be faster on the road than someone with a bigger number.

Putting the danger in perspective, out of the tens of thousands of maps done by hundreds of tuners on the road, I know of only 1 fatal/serious accident which may be related however who's to say that actually occurred as a direct result of mapping, as opposed to the sort of accident that happens to regular people in bog standard cars.

Personally in the past 8 years having mapped somewhere between 4000 and 5000 Subarus on the road, I have not been involved in 1 single accident related to speed. These are the sort of odds I have no problem with :)

Andy