What's in your tank?!

[appletonn]

Just about to collect my new 944t next week and was wondering what you other turbo owners are putting in the tank? 'Mine' has some Lindsey Racing bits on it and is slightly up on the stock 250, so i was wondering how beneficial Tesco's 99 RON fuel (etc) would be?

It is running on 95 RON at the moment & no pinking or anything like that.

Just want as much bang for my buck as i can get...!!

Cheers
Nick

 

[PJS917]

Can't speak about turbo's but with my S2 and 68 I get far more miles/tank using Tesco 99 or
Optimax, not quite as good with Sainsbury's high octane but still better than normal 95 ron. The
performance does not seem to change but the engine is obviously working more efficiently with
the higher rated fuels, given the extended range.

 

[333pg333]

Thought I saw somewhere recently that they said the Tesco high oct was better than some more glamorous fuels??
If you want to increase the boost levels certainly the higher oct will be beneficial.

 

[appletonn]

Hmm, that's what I thought. Certainly, my 'day to day' 325i has a much crisper response to the throttle when I put Tesco's 99 in the tank, so I would expect the Turbo to benefit even more.

Ta very much![]

 

[John Sims]

IIRC BP Ultimate is 97 (so not really the ultimate at all []) Shell V-Power (formally Optimax) is 98.

I use V-Power on all of my cars when ever available. I like the added protection it gives with the Turbo.

On modern cars, with knock sensors, you may not experience pinking as the ECU will work its way around it.

 

[Diver944]

ORIGINAL: appletonn

It is running on 95 RON at the moment & no pinking or anything like that.

It all depends what's been done to it, but it's fair to say that most chips or remaps will have been done for Super unleaded so if you use 95 RON you will not be getting the best out of it. The knock sensor 'should' detect any pinking and retard it thereby losing power but keeping it safe.

I've only ever used V-Power and Optimax in mine but it seems a lot of they guys at the last dyno day had been using Tesco 99 for quite some miles with no prblems.

Of course you could fork out £5 a litre and use the BP 102 [8D] and have your car mapped to suit [8|]. Just think of all the free tumblers you could have at the end of the year

 

[Mark_Bennett]

ORIGINAL: John Sims

Shell V-Power (formally Optimax) is 98.

Optimax was 98, V-Power is 99 [8D]
http://www.shell.com/home/Framework?siteId=uk-en&FC2=&FC3=/uk-en/tailored/shell_for_motorists/fuels/v-power_pkg/tech_spec/tech_spec.html

It does vary by market - e.g. In Germany V-Power is 100...

 

[berg944]

Is it true that most performance chips do not incorporate a knock sensor?

If so it might be costly to run 95 RON.

Mike[:'(]

 

[wibble]

I've only use Shell V-Power since I've owned mine, so cannot compare. It also helps I have two Shell garages nearby within 5 mins of home. []

 

[Neil Haughey]

That would be quite a surprise since AFAIK most performance chips just fiddle with the fuel and ignition maps. AFAIK the knock sensor input on systems like our DME take a certain knock level and equate this to a ignition retardation level i.e. some number of degree's to take of from what the map says. To do nothing about knock is madness.

 

[sawood12]

Virtually all ECU chips disable the knock protection as far as I can tell. This is partly because the pressure sensor in the KLR computer can't deal with higher than stock boost pressures and would trip overboost therefore you need to disable the knock protection to enable higher boost pressures. I'm sure there are other reasons also but that is something I have read. The only way to run higher boost levels and retain knock protection is to go the stand alone ECU route.

The Scivision chipsets with their mafs retain knock protection to a certain degree, however these chips have been developed by the chaps who have had some involvement with the original development of the Bosch motronic ECU system so understand the inner workings much more so than the plethora of aftermarket chip producers. I've also read on Rennlist that the same chaps have developed a kit that replaces the stock KLR pressure sensor with one with a wider range so you can run higher boost levels. However this is intended to work with the stock single port wastegate and cycling valve setup so wont work with DPW's and external boost controllers unfortunately. Also I don't think this mod is available as a kit or if they are even intending to market it as a kit.

Not sure what the limit to the extent you can tune our cars to regarding octane levels. Our dizzy cap ignition systems can only provide +/- 6 degrees of ignition control which limits you to 98ish Octane, so to unlock the true potential of 102 octane you might need to replace the stock ignition system to enable you to advance your timing more than 6 degrees and take advantage of the fuels greater pre-ignition resistance. Again here you are really looking at an aftermarket ECU system which basically equates to $$$$$$ to buy and install and more $$$$$$ to optimise. If you've got the reddies, time and patience though it is the best way to go.

 

[Neil Haughey]

Scott are you talking about the knock detection cutting the boost or the knock detection adjusting the ignition timing. If its the former then I can understand that because cutting the boost is a bit like shutting the door after the horse has bolted.

Getting rid of the ability to adjust ignition in relation to knock is insane. It is somewhat of a myth that engines don't knock except in extreme circumstances. I was surprised to see just how much knock is considered normal by my daily drivers ECU when I had a garage do some diagnostics with the Tech2 plugged into the OBD port. It happens all the time (for a small percentage of the time) and you don't really notice it. I managed to feel some mega buzzing once from the engine at about 6k but in reality this was the ECU cutting the ignition or fuel or both to stop the engine from killing itself because the boost control wasn't working.

 

[sawood12]

As I understand it our knock control systems work all the time in closed loop by advancing timing to the threshold of knock (as you have said in your previous note). If you are still getting knock at full ignition retardation then on the turbo cars it opens the wastegate to dump boost as a safety net feature - so you are right, it's locking the gate after the horse has bolted. I guess the aftermarket chips must only disable the boost dump feature due to the limited range of the KLR pressure sensor. This is obviously not a problem with S2's of course!

One thing that using higher octane fuels does do though is guarantee you do have a good level of octane in your tank as by the time fuel gets to the pump it has been contaminated and diluted by allsorts of filth in the distribution network, so when you buy 98 RON you are probably actually getting something less than that by the time it gets in your tank. So to ensure you're getting 95 RON in your tank you probably need to buy 97RON and to ensure you are getting 97 RON you probably need to buy 99 RON etc.

 

[John Sims]

ORIGINAL: sawood12

....If you are still getting knock at full ignition retardation then on the turbo cars it opens the wastegate to dump.....

Assuming you still have the cycling valve. Most turbo tuners remove it as an unnecessary source of boost leaks.

 

[appletonn]

Hmm, so basically more RONs = more Go and less chance of detonation.! Are you saying that the Lindsay Racing chipset in mine would have disabled the the knock detection process? That would worry me as that is the protection against a bad batch of fuel etc.

If that was the case though, then presumably the timing cannot be 'perfected' to best take advantage of the higher RON fuels we are talking about?

Nick[8D]

 

[sawood12]

This is what i've trying to be getting to the bottom of and have queried most of the main aftermarket chip suppliers and none seem to be able to give me a clear cut answer. The KLR seems to be a bit of a mystery to alot of people. They can talk DME till they're blue in the face but are alot quieter when it comes to KLR. It is definately the case the dump-boost safety net is disabled, but this only affects turbo's and as John has already pointed out most people who mod turbo's bypass the cycling valve anyway so that is no great shakes. However the fact that most chip suppliers say you've got to use a high octane fuel makes me suspicious that they have hindered the closed loop knock control to a certain extent, because if not why would they specify to only use higher octane fuels? I don't know for sure, but on the basis that I only use 97RON as a minimum and try to always use 99RON V-Power it's not a real issue for me - also my current setup is only a stop gap.

 

[Axl Rose]

I use Shell V-Power in my non turbo 944(s)..there's no huge price difference with normal unleaded but as far as i'm concerned it keeps the engine "clean"..

 

[MarkK]

Shell V power!!

 

[eastendr]

I use Tesco 99.

The KLR can only retard a maximum of 6 degrees under knock detection. The DME can me mapped for 102 octane - it is a programmable ingnition map. Maximum advance is 63 degrees BTDC as this is the timing counting reference before TDC. The wiper arm in the distributor cap will cover that range of ignition timing (especially bearing in mind that maximum timing is usually about 9 BTDC degrees during engine start).

The KLR does cannot work in closed loop. The KLR can only retard (not advance) the timing.

Timing is preset in the map (withing the DME). The DME/KLR can only 'closed loop' a timing retard during knock - not advance beyond the timings in the map in an adaptive sense. The DME can, however, closed loop a Lambda sensor signal for AFR under certain conditions (excluding full throttle and RPM over 4,000).

The KLR pressure sensor is good up to 1 bar (14.7 PSI) although overboost protection is triggered below that level with the standard chip.

Knock protection and boost protection are not the same thing.

Most aftermarket chipsets include both a new DME chip with updated timing and fuel maps, mostly optimised (mapped) for higher octane fuel, and a DME chip which disables the overboost protection only (allows greater than 1 bar boost but retains the standard knock retard system that will retard the spark by a miximum 6 degrees under severe knock protection).

The boost protection will only function with the standard cycling valve in place (OK with a Boost-enhancer but redundant with a dual port wastegate / MBC / EBC)

Simply using higher occtane fuel (99 instead of 95) will not release more power unless the timing and fuelling map are optimized for the additional octane.

All said and done, the DME and KLR used in the turbo are very basic in operation. The DME used in the 16V engines (944S / 944S2 / 968) features two knock sensors and adaptive idle so is a slightly more advanced design.

I hope this clarifies ...

 

[sawood12]

Good stuff Rick, that does clear up alot of loose ends in my mind. However you say that knock protection does not run in closed loop,, then what controls timing advance? If the ECU doesn't advance timing upto the knock threshold, say under WOT, then what does it use to determine how much advance to use and when? Surely it can't be via engine vacuum like my old MK3 Escort?