Road mapping may lead to overly optomistic spark advance, such that the engine seems det free, but then if you get some real heat into it with some on-off-on boost type driving and it will start getting more prone to det. I would also suggest that a dyno mapped engine is more likely to be run at closer to ideal AFR's than a road mapped car, thus necessitating less spark advance than an engine running much richer mixes.

Of course, a dyno mapped engine run with closed loop knock control on ignition timing and closed loop wideband lambda control may be able to adapt itself for road use and possibly even gain some timing in the process under some conditions, but the underlying base map should always be safe. :)

There seems to be a belief that holding a particular load zone for a period of time is bad...Why is that then?

Most OEM`s engines are signed off with a 8hour plus run at full load / max rpm.

More likely to damage an engine on a chassis dyno due to temperature / cooling problems.

You hold what ever you like on the dyno (load and / or speed) as the coolant and intake air should be controlled (temp wise).

There are issues with `dress` kit not quite being the same as an `as installed` powertrain hence the need to `check` on the road / chassis dyno.

But for an optimum solution; engine dyno all the way.

Whilst less scientific, getting the car hot and then driving it through a gear on the brakes with pretty high loads is a way of checking your safety margin.

No, I don't buy it. On an engine dyno you can control oil, and water temps, so you can map the engine at various temps, and use the compensation tables.

Whilst you may get close to MBT on the road, there are too many variables to get it spot on. Besides, you're unlikely to reach MBT at WOT anyway. On the dyno, you'll actually see where MBT is through the cruise, and lower boost zones. I'd agree that this might differ slightly on the road, with the full exhaust fitted, but you're starting from a known point.

I suspect that some of the comments, are based on peoples experiences with particular ECU's, and how they deal transitions, fuelling, and varying temps.

Mark.

Mark

I know for a fact that if my engine is set to run with optimum timing and boost for a rolling road run at Star performance (read slow ramp rate) it does not perform as well on the 1/4 (fast ramp rate) as it does with more timing, less fuel and more boost.

I can safely run more boost, more timing and weaker fuel for the 11. odd seconds it takes to run a 1/4m than I would run on a track day for example.

Call it qualifying spec ;)

Ok, so this really doesn't have anything to do with mapping on a "dyno", but simpley how you choose to map the car !

I suppose that some will tune their cars to "Qualifying spec'", race gas, methanol ;), nitrous, etc', and I accept that their car will be quicker for the 11 seconds or so, it takes them to do the 1/4.

My personal preference is for the most powereful "safe" map, that's good for extended time on the track, and day to day use. That's not to say that I wouldn't have an alternative "Qualifying spec" map for the very occasional 1/4 mile run :D

Mark.

Mark You asked - It's not just about how close to the edge you map, the optimum (safe) settings depend upon the acceleration rate of the engine ie the duration at any one RPM. So if you map for steady state WOT at any RPM the engine will have reduced output in comparison to a set up optimised to the acceleration rate actually used in practice.

I'm sure you know what I mean but the inference earlier in this thread was that steady state dyno WOT pull was the 'best' way to map, I disagree but think it is a good starting point :)

Mark,
You don´t have time to write on this board ;)

Skassa

Bench dyno or rolling road, they are both just brakes and you read off the force x distance x speed to get power at any set rpm.

On a decent rolling road with a good fan you can hold any rpm you want at WOT and tweak away at timing/fuel/boost......but it will be just an approximation due to the different airflows and acceleration rates seen on the road.
The bench dyno suffers the same problems, maybe even worse as you say due to the exhaust system, packaging of the intercooler pipework and the problem you had with fuel supply etc.
If you can control the tyre temperature rise or apply a correction then a rolling road may even be more accurate than your engine out on a bench set up.

Andy, with respect m8 you don't half talk a lot of twaddle sometimes ;)

If you had a brand new untried engine (like Mark's) with no base map to even start with would you even attempt to map it on the road? Even on a rolling road where so many factors have to be taken into account?

A bench dyno makes the most sense, you can try things, hold ignition/boost/fueling zones reliably and repeatably, far more so than you could ever possibly contemplate doing with your foot ;) while the car is trying to climb out of the rollers :eek:

Yes, you will undoubtably have to tweek the map once it's in the car but not on a rolling road, because it still won't behave like it would in the real world, preferably a nice long straight road, Bruntingthorpe springs to mind...

At the end of the day everyone has their preferences usually based on experience, or the depth of their pockets. Maybe once you have had a chance to play with an engine on a proper dyno you'll change your mind :D

Personally I can't afford engine dyno time at the moment, but should I spend 5k + on an engine I think I would...I'm sure I'll be trying Abbey out sometime soon though, to me the dyno pack sounds like the next best thing to an engine dyno!

I agree the dyno packs look like a good option :)
For a road car I just don't think bench dyno time is justified. Different on a one make series race car (which I have mapped on a bench dyno thanks :) ) however that's where 3 bhp at 9000 rpm can be the difference between winning and being an also ran !

It's road cars we are talking about here with no regulations controlling the spec of everything. There is a huge window of satisfactory performance, something like 20% fuel flow and 5 degrees timing will make less than 5% difference to power.

As we all agree the final map needs tweeked on the road anyway, whats the point of spending a lot of time and money getting it 'spot on' on the bench :confused:

"There is a huge window of satisfactory performance, something like 20% fuel flow and 5 degrees timing will make less than 5% difference to power."

Andy,

Do me a favour, take out 20% of your fuel, and add 5 deg' of ignition, let me know how you get on !!!

Mark.

Might be more helpful to know which turbo you're looking at, and what for? Being hybrids, they're all designed fairly specifically for different applications, so will vary greatly...
Most of the difficult bit about picking a turbo is picking the right one, rather than it being 'good' or not; some self-destruct (like the VF22 :)) but aside from examples such as that which are few & far between, it's what's suitable for the application. Buy one that was designed for one spec & try to push it to another (typically trying to ram more boost through it than it's intended for) and it won't be a good turbo. Pick the right one in the first place & that wouldn't have been a problem :)
Some manufacturers (APS spring to mind :rolleyes:) may make fantastic turbos, but supply data for them which is 'a bit iffy' so it's hard to know whether they are suitable or not. They have rave reviews from most, but not all, but all it's possible to put that down to is whether the right choice was made rather than whether it was the right turbo or not (their data appears accurate but sometimes impossible and is compared to a known turbo that the data is most definately bunk for, meaning that it's very hard indeed to make a correct choice).
Advice/opinions, on the whole, will be very personal, and so may not be a lot of help to you. Most people don't work their way through very many turbos, so don't have a lot of knowledge on turbos other than the one that they 'upgraded' to.
Something to bare in mind are that power is most certainly not everything, unless you are into sticking your car on RRs or drag strips, in which case it can be. But for most of us, 400bhp at 5000+rpm just doesn't make a nice daily drive if it's pants below 4000. But for others, this is no problem.
Talking through it with Mark is probably the best way to make sure you get the right turbo. I don't think there are many more people about with more knowledge on turbo choice!
I think I've drivled for long enough :D so will stop now, you'll be pleased to hear!

[Edited by nom - 4/8/2003 11:22:50 PM]

A bit off topic... as to-date I have never personally purchased anything from Lateral Performance. Sorry Mark :o ;)

However, have regularly picked Mark's brains & have found him always to be:
Extremely knowledgable - Knows Subarus & MY variants thoroughly
Very Informative - No Bull to sell a product - straight facts
Honest & Trustworthy

In Fact - This, on at least one occasion, was to the detrement of himself, as he talked me out of buying one of his products :confused:

As such I would whole-heartidly recommend him & thoroughly trust him.

The day I need an upgraded Turbo, Clutch/Fly, Fuel Pump or whatever - he will be the first person I call, & one of the few I would trust & buy from above any-other.


Regards,

Chris


Disclaimer: Never purchased a single item - but a very happy customer :confused: :D

[Edited by Chris.Palmer - 4/8/2003 11:44:24 PM]

TD05-20G would be my choice :) Ported wastegate, 1 bar boost from 2800, easily make 360 at 1.3bar and at that pressure there would be no surge issue (which can be mapped out anyway at higher boost)

A front entry ported TD05 would make the same power at 1.5bar.

Here endeth the vote from the Scottish Mafia (or at least one of them ;) )

[Edited by Andy.F - 4/9/2003 2:13:06 AM]

I will be running a GT series hybrid from L/P on my own car i am very pleased with the spec mark and myself have decided on. I will only use L/P turbos on my customers engines. There will be some very serious scoobs and evo`s coming to light this year and all will be runing L/P turbos.
Steve.
John;).. thats better.

[Edited by S,M,G - 4/9/2003 7:38:55 PM]

Can you not compare lag between different turbos by planting the accelerator at 5000 RPM and measuring the time difference between say 0 and 1 bar boost whilst on the way to something higher? Using a Dawes for example set to equilibrium at 1.5 bar I can't see how any control system could possibly have less lag since the normal position of the Dawes is closed so the wastegate should also be closed assuming the EGBP is not excessive which is unlikely on these sorts of turbos at 5000 RPM I would think?

What I have observed across the list of turbos below (some from datalogs, some from seat of pants) with various actuators and turbine clips and mod levels is that there is a clear and strong correlation between boost threshold and lag from 0 to 1 bar at 5000 RPM with no apparent free lunch, would be interesting to drive/log a Garrett ball bearing turbocharged car compared with the sleeve bearing TD series or roller bearing VF. The turbine and housings in particular seem to use varieties of trim, size and housing AR to achieve the end sizing, boost threshold and lag characteristics.

TD04L
TD04 hybrid
TD05 16G small
TD05/06 20G hybrid
VF23
VF28
VF29
VF35
MD304

It strikes me that Garrett seem to use step ups in trim, AR and size of their turbine wheels with a few options at each level.

For Subaru applications, and things we can use as a basis for upgrade IHI seem to use a step up in AR on P18 and P20, with a relatively small wheel and quite a high trim.

MHI - for standard bolt up we are restricted to the 7cm2 turbine housing (estimated AR is quite low at about 0.5) but the turbines are quite big.

So comparing a TD05 with a VF22 for example you have almost opposite techniques used to size the hot side - TD uses small AR, medium trim and large wheel, VF uses medium AR, large trim and small wheel (all relative). I don't know if this is why the TD05 outperforms the VF22 at just about everything or not?

Hybrids seem to concentrate on beefing up the compressor side - wonder if this is because a big housing is easier to fit in and plumb - only an inlet pipe and outlet pipe which are usually flexible.

The Subaru up and downpipe flanges are obviously rigid, hot and proprietary hence the lower variety of housings for hybrids.

The P20 housing with its big AR is a known strong performer with a Garrett wheel and bearing it seems - the decent AR with bigger wheels than the ones used in IHI VF series for Subaru applications might explain this?

[Edited by john banks - 4/10/2003 12:33:24 PM]

I have :D :D :D :D and they are conservative figures.. :eek: :eek: I blame the driver at the time :D even though it happent in traffic near a bus stop iirc..

And it was through no fault of Marks, hence why someone else is paying (a manufacturer iirc)

Anyway..

Ive got a bed to go to...

Till the next rolling road day :D

David
ps my cars quicker than yours :p

pps If anything is incorrect mark let me know and ill ammend it.. after all I've had a drink, and had, had a few when you were telling me about your engine.. :rolleyes:




[Edited by David_Wallis - 4/11/2003 12:25:15 AM]

I seem to recall Craig H was running a 2.2 ?

I've run an 11.8 at 115 on a std TD05 which was producing only 345 bhp (at Star performance) you can't relate power directly to 1/4 mile times, there's a lot more to take into consideration :)

[Edited by Andy.F - 4/11/2003 1:50:05 AM]

Andy...then that makes my car incredible from that point on if I can acheive 166.6 mph in the same run :p

Did you not notice what I said about my launch for that run earlier:

'Still I think the figures from Elvington last year speak for themselves, with a gentle launch to 1.25 miles 166.6 mph can't be wrong...and I'm only claiming 344 PE brake ;) '

I wasn't prepared to blow up my gearbox, I had to drive home, and get to work the next day :eek: so there was no way I was going to try a proper launch at 5k + rpm and just dump the clutch...nope, I just rolled off the line, then accelerated, still got wheel spin through 1 st and 2nd with a bit of a chirp in 3rd too ;)

If I had been prepared to launch the car, like say Plantie (who was also running a VF series Lateral Performance Hybrid Turbo) and get a 14.5 second 500m run (from memory), perhaps my top speed would have been higher still :D he went on to record 163mph only to discover I had pipped him and they had stopped the top speed runs :p man was he gutted :D

Oops, got Plantie's time wrong

[Edited by Tim W - 4/11/2003 7:13:26 PM]

This is such a great thread. I have not seen such bitchyness in ages. :D

Please keep it up!!!

Dan

Edited to add, I wish my car was as powerfull as most of the cars being talked about. I just wouldnt know what to do with it. Dropping the kids off at school, doing the weekly shop and general 20mph driving. :p

[Edited by Danny Fisher - 4/12/2003 12:22:50 AM]