R35 GTR v My 944 Turbo

[gavinm]

ORIGINAL: sawood12

ORIGINAL: gavinm

Regarding the comments about the GTR time around the Ring...of course the car was supported by a team of engineers...no car that is taken there by a manufacturer for an official time is not supported by engineers..this comment has no real value..if you look just outside the ring there are a growing number of manufactuerer centres built there specifically to support their cars testing and developments at the ring. I can assure you that Porsche also have a team of engineers on hand when they get down to some serious testing on the ring.

And as an employee of Dunlop Motorsport i can confirm 100% that the tyres used where Dunlop SP600 run flats for the second attempt, where the GTR was a bit quicker, recording a time of 7'27.56 using the GTR V Spec model which does have lighter wheels than the standard.....this tyre is the homologated tyre for GTR'S for Europe and Japan, the GTR Porsche used was imported from the states, it wasn't running on Dunlops, I don't know what it was running on...

HTH []

I'm afraid I disagree - or at least come from a completely different school of thought. The time is completely irrelevant unless the car is completely in stock production trim - i.e. the standard the car would be if you went and bought one. The GT-R that posted that time was far from bone stock trim - as Porsche has demonstrated when they took a bone stock one round themselves- it was way way off that pace. The official Porsche ring times for each model are for a bone stock car on stock tyres. I realise the tyres on the GT-R are 'stock' tyres (i.e. the ones they come with), but they're hardly like Continental Contisports - they're much more akin to R spec tyres - pretty specialist pieces of kit - and the price of nearly £1k a corner demonstrates that (i'm sure you'll correct me if i'm wrong, but it is what i've read in many magazines). Now if you stuck a 997 turbo on semi-slicks, got a team of Porsche engineers to customise the cars' setup specifically for a single glory ring run on a particular day then the times would be far far closer.

Tom - sounds like you're having a blast in the old girl. Good on you. I noticed a night and day difference to how the turbo picked up when I installed the DPW (got 240bhp on the 'rollers of truth'). I then noticed another night and day difference when I installed the ECU chips and increased boost (got the 179bhp on the same 'rollers of truth'). Sounds like you are unlocking more potential. Get a Vitesse MAF kit on her and you'll unlock even more. The free'er flowing MAF will allow the turbo to spool up a bit quicker and will help flow more air at higher RPM. Keep us posted!!

debate is always healthy!

the GTR which did the 7.29 was bone stock, the one that shaved a second and a half off was the V-Spec...

as for tyres, yes, they are not your average run of the mill Conti's, but they are just as valid as the porkers using Cup Sports...which are also pretty tasty as an OEM tyre.....same same....

I think it would be naive to say that Porsche wouldn't have their engineers out in full force and setting up their car just right for their lap record....it would be extremely shortsighted on their part....

Don't get me wrong, I'm not saying the skyline is a better car, but on the day, it acheived a quicker time on the ring....it's all a bit of daft willy waving in the end anyway......real world relevance is pretty much nil....

I know if i had the cash my money would be spent on on a GT2, GT3, GT3RS...hell I'm not picky..they're all gorgeous....[]

 

[Suffolk944]

ORIGINAL: barks944

Tom - sounds like you're having a blast in the old girl. Good on you. I noticed a night and day difference to how the turbo picked up when I installed the DPW (got 240bhp on the 'rollers of truth'). I then noticed another night and day difference when I installed the ECU chips and increased boost (got the 179bhp on the same 'rollers of truth'). Sounds like you are unlocking more potential. Get a Vitesse MAF kit on her and you'll unlock even more. The free'er flowing MAF will allow the turbo to spool up a bit quicker and will help flow more air at higher RPM. Keep us posted!!

I do like the vitesse kit, especially the full package with the piggyback and v-flex. Although after being told by JM that there is a full engine management kit being produced I'm tempted to wait for that or to setup one myself. I think adding an EBC at this point would give a really quick spooling turbo, maybe too quick .

Thats my next step (hopefully in the very near future) along with some bigger injectors,though dont think will get the piggyback at this stage. Have already got an EBC so in theory that will be the last mod on the car (yeah right ! []).

 

[barks944]

What did you think of the EBC then?

 

[Suffolk944]

I like it, it holds boost much better than a MBC and the power delivery is far more linear with it. It also has the useful function of being able to set boost levels, so I have one with a lower boost for damp/icey/slippery conditions - not that I have ever used it ! []

 

[barks944]

Does the 944's DME cope with chaning boost levels? My car has a promax chip and I was told not to change the boost level. I also thought that the DME didnt really use the AFM while on boost and was injecting based on some pre-expected boost level or somthing. But I have reason to doubt that now and I have heard the AFM can measure up to about 300hp so should be able to adapt to changes in tune.

 

[sawood12]

DME doesn't see boost at all. The AFM is just a flap and there is no way whatsoever that the collection of sensors fitted to a 944 turbo can directly measure air mass flow, therefore boost levels are assumed. You cannot vary boost levels with stock AFM/DME setup - you need a true MAF kit or MAP with standalone or piggy back. If you use an AFM with the Promax setup - or any other aftermarket chip setup, you need to set it to achieve a single max boost pressure setting and cannot utilise the functions available to you on the EBC. Personally I don't really see the need. I found it very easy to regulate boost pressure with the right foot with a bit of practice. If you want to set the car up such that you can give it full welly and let the EBC sort things out thus preventing excessive wheelspin, then the functions would be useful (e.g. varying boost pressure with gears - a sort of dumb traction control), but I prefer to regulate using the throttle. However even in this simple mode you are getting the benefit of the extra control of the EBC - getting boost built quicker and holding boost longer.

 

[Neil Haughey]

ORIGINAL: sawood12
DME doesn't see boost at all.  The AFM is just a flap and there is no way whatsoever that the collection of sensors fitted to a 944 turbo can directly measure air mass flow, therefore boost levels are assumed. 

KLR? I have never owned a 951 but AFAIK you have a vacuum line going to the KLR. The KLR has a pressure transducer inside it which in effect measures boost.

 

[barks944]

I think the KLR only detects overboost and isnt used to inject.

Scott, this is what I thought originally but I have info to suggest otherwise. Actually the DME doesnt need to know boost to cope with changing boost levels, just as with a MAF setup as long as the AFM can measure the volume of air the DME can calculate air mass and inject accordingly without knowing what boost the car is running. Ok we all know the 944 AFM isnt as good as a MAF but it should still cope as long as it can measure the air flow. Originally I though the AFM's output maxxed out with quite a low air flow but other information I have read suggests that the AFM on the turbo can measure airflow good for around 300HP. I can't confirm this at all yet. But I think I will do some tests. I guess the reason that there are different maps out there for different boost levels is for the igntion timings and maybe to adjust AFR to help prevent knock. Also note that MAF also doesnt know boost pressure, it works as it doesn't need to know it as it knows how much air the engine is sucking and therfore knows how much fuel to inject to achieve a given AFR. The same principle applies to the flap AFM.

The problem then with MAF alone or the 944's AFM is that the DME cannot adjust timing or AFR based on boost level thus you are stuck using settings that work across the board unless you switch maps.

Also scott, the promaxx guys suggested there are multiple maps on their chip. How does one select the different maps out of interest?

Edit: To further confuse the issue JM's Klaus Hoffman chips are claimed to be able to fuel his 3.2 litre engines. My understanding is this is without needing to be re-mapped, otherwise it wouldnt be much of a claim....This further confuses things as I can't fathom how when surely those engines are much more than 300HP! Perhaps he has a way to measure boost using the KLR even though it wasnt used originally. Even if it knows boost it still shouldnt really know what to inject.

This DME is shrouded in mystery I swear.

 

[sawood12]

To work out air fuel ratios you need to know the mass of air entering the engine and not the volume. The 944's stock motronic system cannot measure air mass. There have been plenty of 944 engines ruined by people simply increasing boost pressure. The pressure line going into the KLR is there to measure against overboost and knock protection. I don't believe the pressure values are not passed over to the DME for the DME to adjust fuelling against. When the KLR detects overboost, sends an input over to the DME to tell it to start retarding ignition. The MAP sensor in the KLR is only good upto about 1 bar or something like that anyway. There was a guy on Rennlist who was a bit of an electronics wiz who replaced that MAP sensor to one that could measure higher pressures and, along with some chips increased the max boost pressure whilst retaining a fully functioning stock motronic system.

Tom, The different maps available on the Promax chip are selectable via the FQS switch. This is the Fuel Quality Switch and in the stock chips selects different ignition maps to cater for lower quality fuel (not to be messed about with). This is a small rotary switch on the side of the DME. In the Promax chips the extra maps are for use with different sized injectors (55lb and 65 lb I think). The instructions should be included with all the paperwork supplied with the car.

 

[barks944]

ORIGINAL: sawood12

To work out air fuel ratios you need to know the mass of air entering the engine and not the volume.

But with an approximation of the atmospheric air pressure and the air temperature you can calculate the air density and thus the air mass flow. Certainly that is what I was doing the reverse of in my MAF converter to make an air flow signal from the MAF signal. The later 944s had an atmospheric pressure switch that would lean out the fueling at high altitudes.


Edit: Thanks for the chip info too . D/W I'm not just going to crank up tha boost . Ive ordered an 8 channel 10khz datasampler and Ive got a wideband kit so just want to do some exploratory datalogging.

Oh and the reason for this is that I might have found a solution for approx $450 to allow real time map editing, datalogging, MAF and adjustment of all 75 maps on the 944's DME. Not quite sure yet though .

 

[TTM]

ORIGINAL: barks944
Also note that MAF also doesnt know boost pressure, it works as it doesn't need to know it as it knows how much air the engine is sucking and therfore knows how much fuel to inject to achieve a given AFR. The same principle applies to the flap AFM.

The problem then with MAF alone or the 944's AFM is that the DME cannot adjust timing or AFR based on boost level thus you are stuck using settings that work across the board unless you switch maps.

This is more or less what I have observed.
For instance the Vitesse MAF doesn't work with boost, but with engine load, and it will send a certain quantity of fuel given the load applied, regardless of boost. I have found this to be very problematic in moderate load where I find myself either using boost or not, leading to running either too lean or too rich depending if I've chosen a fuel map suited to work, in moderate load, with low boost or no boost at all.

ORIGINAL: barks944
Edit: To further confuse the issue JM's Klaus Hoffman chips are claimed to be able to fuel his 3.2 litre engines. My understanding is this is without needing to be re-mapped, otherwise it wouldnt be much of a claim....This further confuses things as I can't fathom how when surely those engines are much more than 300HP! Perhaps he has a way to measure boost using the KLR even though it wasnt used originally. Even if it knows boost it still shouldnt really know what to inject.

As far as I understand it the KLR works as an active boost controller, not only as a safety device. It is a well put together piece of EMS which requires loading the engine with different levels of boost to get the righ, final, fixed fuel map, and when this is done I see no point moving to a MAF set up bar the advantage of getting rid of the flap responsible for the slow throttle response.

 

[Diver944]

The flap on a standard AFM goes to full deflection way before a standard car reaches peak boost of 0.8 bar, at this point it is just looking up tables and delivering a set amount of fuel compared to RPM. When you raise the boost and use a different chip it alters this fuel delivery accordingly.

If you start lowering or raising the boost from this pre determined level then you will simply start running lean or rich because the DME will carry on delivering fuel regardless of what boost you run at.

However, if you know what you are doing you can re index the spring inside the AFM so that the flap does not go to full deflection until a greater volume of air passes through it. This is what JMG did to my 3.2 when running on the KH chips in it's early days. We took it to the Dyno to measure the AFR and found that the maximum safe boost was 15psi with a peak AFR of around 11.5:1

It made more power at 16psi (350bhp/450lbft), but the AFR was going over 12:1 and the Dyno operator started to detect some knock so it was dialled back to 15psi

 

[barks944]

Ah right, that clarifies a few things then. I heard mention of the KLR calculating load before, what information is it passing to the DME?

 

[DivineE]

This thread is rather confusing my understanding of the cars engine management. I get the feeling that there are many people (like me) who have a partial understanding.

My understanding is the standard setup measures airflow and calculates appropriate fuel at partial throttle but switches to a set map on the chip for WOT acceleration because its outside the sensors reading.

On that basis with a chip which knows the size of the injectors and the fuel pressure (even if all is standard) it should adjust the fueling correctly as long as it is measuring air flow correctly no matter what boost or air flow sensor.

So (in my theory) if you had an air flow sensor (MAF) that could always calculate airflow - even at full throttle - and the readings could be inturpreted by the ECU then the ECU should adjust the mixture correctly no matter what boost or power. The beauty of simplicity.

I also believe that the boost signal sent to the ECU is only for triggering the overboost on the standard car which is disabled by aftermarket chips. I don't see any other reason why it would need to know it?

That's as far as my understanding reaches. I'd love to know the full story or be corrected if I'm wrong though?

 

[edh]

That's how I understand it Ben - I think the vac line to the KLR also works the factory boost gauge

 

[barks944]

I don't think its that simple unfortunately as even though it can inject to a given afr as it knows air mass it cannot know what afr to inject to or what ignition advance to use as it depends on boost pressure. Without knowing that you cannot actively control knock except by being conservative. It would prob do the job but it won't get it perfect.

 

[sawood12]

OK, for starters the motronic doesn't flex ignition according to boost pressure. Ignition maps are not sensitive to boost pressure and are set conservatively. The Vitesse C-Flex does this but outside of the Motronic in the Vitesse piggy back computer. Also the motronic doesn't at any point calculate air mass. The motronic works totally off maps encoded into the ECU EPROMs. The values off the maps are read off according to the values measured by the various sensors and the values in the maps themselves are achieved largely from trial and error. There is no clever maths that goes on to calculate AFR's. It is a bit like you reading off a bus timetable. You just read the times off the timetable - you don't sit there and calculate when the bus should arrive at each bus stop according to average speed's, allowances for traffic and the old dears taking too long rummaging around in their purses for coppers to pay for the bus ticket.

The boost line to the KLR is purely there for protection against overboost and knock. The DME doesn't at any point know what the boost pressure is. The KLR will detect overboost and tell the DME we are in an overboost situation and upon receiving that signal the DME will retard timing. If you have aftermarket chips this functionality is disabled as you'd be triggering the overboost protection every time to achieved above stock boost pressures. Incidentally the KLR also looks at the rate of increase of boost pressure and will trigger overboost if it deems the boost is building too quickly. Ignition retardation will still occur when knock is detected.

So if you change fueling, the motronic doesn't know and will not accommodate. If you change boost pressure, the motronic will not know and will not accommodate.

 

[barks944]

I think the DME does know air mass Scott, or at least has an approximation to it. As well as reading the AFM value the DME also knows the air temperature (at least what it was at startup). The DME has a map of fuel compensation for air temperature to allow it to inject correctly across a range of air temperatures. This compensation is essentially a *rough* conversion to air mass. Thus the DME get its air mass, or an approxmation too, from air temp and air flow. The Vitesse MAF for example measures air mass directly and does not need to know air temperature (although it may still use air temp in some way). Either way both setups use air mass, or an approximation, as a component for working out how much fuel to inject. The difference is the number of sensors needed to work out what the air mass is.

As you say Scott neither know boost and neither can change ignition or fuelling to compensate properly for changes in boost level. Which is where somthing like Vitesse V-flex comes in.

Check out: http://www.thedmeeditor.com/

This is some new software by FRWilk. There are over 75 maps on the motronic DME. Not all used for injection but also ideling speeds etc. This software can address all of them. I think this opens up a route to DIY true MAF conversion. I think it may be achiveable by cancelling out the air temp correction map and doing it all via what was the AFM signal. You can see how many maps the DME uses for ignition and fuelling based on a multitude of inputs. This software is about £140.

Now here is the interesting part, a company called Moates make a product called Ostrich. This is a hardware device that allows you to hook up to the 944's DME chip slot and emulate the DME. You can upload maps via usb, real time tune, datalog etc etc. This device is about £130. Currently a few ppl on rennlist are using this but they only have access to about 7 maps, which is *apparently* what many chip makes have access too. I guess Vitesse might be the main exception. One guy is making 390WHP on his turbo using this. They can hookup MAF sensors but it is not a true MAF, an changes in air temp prob screw up the AFR's. Perhaps the ADC used for air temp could be adapted for a MAP sensor.

Couple this software with the ostrich device and you have a real time editing function with the ability to edit all 75 maps on the DME and setup true MAF conversion all for about £300 + a MAF meter. Sounds like an interesting prospect for the DIY tuner. Especially coupled with a datalogger and knock sensor. Still, you need to know what you are doing and would probably still need a Dyno. Still not got the ability to properly handle changes in boost level though. But as mentioned this should really be using our right foot for this .

 

[edh]

Just read this on Rennlist - posted by John @ Vitesse

"You just have to love it when a 951 can still play with the newer and much more expensive P cars.
A good customer in Europe just emailed me the followings (I'm posting with his permission):

Quote: "Yesterday we made an acceleration test at the track between my car at 21 psi (456 BHP and a weight of 2895 Lbs) and a 997 RUF (550 BHP and a weight of 3290 Lbs) from 62 mph to 143 mph.

I enclose one of the pictures,

the RUF won 2 and my car won 2. The two cars have the same acceleration." The 951 is still a 2.5L running: Vitesse Stage 2 kit, VR Sledge Hammer (Big Valve) head and Vitesse Cam. He was running V-FLEX and E85."

http://forums.rennlist.com/rennforums/944-turbo-and-turbo-s-forum/540293-951-playing-with-a-big-modified-997tt.html

 

[barks944]

Awesome! That car is really flying . Well done Vitesse!

The vid : http://www.youtube.com/watch?v=FCVodImUOrg

Nice vid of a 44 giving a gt3 a good run too: http://www.youtube.com/watch?v=vExPd7IlCbc